Water Supply Hand Book

Handbook on Works Audit -Water supply

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HANDBOOK ON WATER SUPPLY

Office of the Principal Accountant General (Civil Audit) Chennai


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Water Supply and Treatment 1. PREAMBLE Tamil Nadu Water Supply Drainage board (TWAD) is responsible for execution of Water Supply Schemes / Drainage Schemes in Corporations, Municipalities, Panchayats, Villages in the entire State of Tamil Nadu except Chennai City where Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) is executing the work. Government of India Ministry of Urban Development, Central Public Health and Environment Engineering Organisation published a Manual known as " Manual on Water Supply and Treatment ". This Manual has laid down the basic principles relating to planning, identification of sources of water, development and transmission, water treatment, distribution system testing and other related administrative aspects and also explain in details the proper approach to each problem. The salient points relevant to audit together with various orders of Government and TWAD Board and audit approaches are given below. The CPHEEO Manual provisions indicated are with reference to the 1999 Publications.

2. PROJECT FORMULATION The objectives of any Water Supply System is to supply safe wholesome water in adequate quantity at convenient points and at reasonable cost to the users. In order to encourage personal and household hygiene proper planning is necessary in the formulation and implementation of water supply projects. Engineering decisions are required to fix the area and population to be served, the design period, the per capita water supply, the water required for the other needs in the area, the nature and location of facilities to be provided and points of water supply intake and waste water disposal. Detailed investigation should be carried out in regard to nature of each source (surface or subsurface) its reliability for quality and quantity, the nature of development and type of treatment required and mode of the conveyance from the source to the consumers. Different alternatives should be considered in detail and the economically viable and technically feasible alternative should be selected by applying financial analysis techniques. Four stages are involved in the formulation of a water supply project before the project is taken up for execution. They are a. Preparation of preliminary report b. Conducting detailed Engineering survey



c. Preparation of Project Report. d. Preparation of detailed plans and estimates. Preliminary report The report should include a brief description about the topography, geological and hydro geological features of the community, existing water supply arrangement and need for the project. Further the report should discuss and include the following aspects also. i. Identification of the area to be served with details of present population, existing water supply and sanitation facilities. ii. Identification of the water requirement for various needs. iii. Estimation of water requirement for various needs. iv. Identification of the possible alternate projects and rough cost estimation them (if possible) for installation. v. Details of engineering survey to be conducted and probable time and personnel required for carrying out the survey. vi. Cost of the engineering survey. An index map to a scale of 1 cm= 2km, a schematic diagram and a layout plan to a scale of 1 cm = 250m should be included in the report. Engineering Survey The data required to be collected for the preparation of Project report initially and for the preparation of construction plans and detailed estimates later, comprises of the following. i) Census population figures for the town for atleast five preceding decades. ii) Present rate of water supply and factors that will affect future and industrial demand. iii) Details of existing water supply and sewerage, electric and telephone facilities, the quality and quantity of existing water supply under average and adverse conditions and conditions of existing mains. iv) Field survey and leveling work connected with source development, location for treatment plants, pumping stations and service reservoirs, alignment of transmission main and preparation of detailed maps for the distribution system with contours. v) Master plan for that area. Further data to be collected for each of the component are as detailed below. a. Surface sources i. Sanitary survey for 10 km upstream and 2 km downstream of the proposed works to locate source of pollution, cremation ground etc., ii. Water sampling and quality analysis. iii. Minimum discharge in the river.


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iv. v.

Plan of river course 3 km upstream and 3 km downstream of the proposed off take. Cross section of river upto and above MFL on either bank. Likely shifts of summer course of the rivers. Sub soil details upto scour depth and hard strata.

vi. vii. b. Impounding reservoir i. Sanitary survey of entire catchment or atleast foreshore areas, existing sources of pollution and possible pollution and remedial measures. ii. Survey of soil, vegetation and their effects on water quality. iii. Water analysis covering seasonal variations. iv. River flow or run off records, stream flow gauging, riparian rights. v. Continuous survey of water spread, dam alignment foundation details and availability of materials. vi. MFL, LSWL and other particulars. c. Infiltration works i. Quality of sub surface water. ii. Whether river is perennial? What is the lean surface flow in the river? iii. A grid work of tell tale borings at 30-60m intervals for full width of the river 120m upstream and 120m down steam, of the proposed site for infiltration works. iv. Effective size and uniformity coefficient of sand at different depths. v. Maximum flood level and minimum summer water level. vi. Scour depth arrived at for the structures nearby constructed, by PWD, Highways etc., d. Ground Water Source i. Availability of ground water and its quality. ii. Geophysical survey to locate bores. iii. Examination of hydro geological and hydrological factors. iv. Topographical survey. e. Pump houses and treatment works i. Topographical survey to decide the best location of treatment plant. ii. Trial pit particulars and safe bearing capacity of soil. f. Transmission main i. Alignment Plan ii. Longitudinal sections at 150m intervals, along the alignment. iii. Details of crossings of river, railway, road (National or State Highways) iv. Trial pit particulars at 1 km intervals along the alignment (at closer internal when there is vide variation) v. Safe bearing capacity of soil at level of pipe support.


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vi.

Soil analysis of soils met in the trench for indication of corrosiveness. vii. Bedding or cushion to be provided at the bottom of the pipes depending on the type of soil met with. g. Service Reservoir The following particulars are to be collected i. Operational records to study storage requirements. ii. Highest elevation in the area of town are to be identified for locating the Service Reservoirs. iii. Spot levels at site proposed for the Service Reservoir. iv. Contours of the town for dividing the area into numbers of zones. v. Foundation details. vi. Trial pit particulars to assess the safe bearing capacity of soil at the site. vii. Maximum and minimum ground water levels. h. Distribution System The following particulars are to be collected. i. Town map in the scale of 1:200 showing all streets with names. ii. Number of houses in each street, prospects of further development, nature of houses, number of floors and height. iii. Kinds of roads. Such as concrete, BT, WBM roads iv. Town planning proposals. if any, with proposed approved layout. v. L.S. streets at 30m intervals. vi. Trail pit particulars at 500m intervals along the proposed alignments vii. A plan showing the existing distribution lines, if available with year of installation. viii The number of existing public fountains and existing house service connection. i. Land plans Survey Maps to be obtained from revenue authorities., SF Nos., Revenue classification of Land its ownership and cost of the land to be obtained for acquiring land for Service Reservoir, Pump house, treatment works. Project report The administrative sanction for a project is to be accorded by the authority considering only the project report. The project report should therefore be prepared with great care incorporating adequate particulars like need for the project, details of engineering survey carried out, the alternate project evolved, their cost and merits etc., The following details are to be included in the project report. A narrative report describing the project with the following aspects. i. Historical retrospect leading to the demand of the project. ii. Short description of existing water supply facilities.


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iii. iv. v.

Details of the different sources considered with their relative merits. Raw water quality of the different sources and treatment envisaged. Engineering features of the head works and layout of the components of head works. vi. Economic analysis for sizing of transmission main and Branch for the conveyance of the water from the source to the community using ECP and Branch 3 Software. vii. Capacity, and elevation and location of Service reservoirs. viii. Salient features of the distribution system like number of zones, ground level variations in each zone. ix. Comparison of costs of alternatives and project as recommended. The project report in a complete shape incorporating all the above details with estimates for installation of the project and for the annual operation and maintenance is to be submitted to the competent authority for according administrative sanction. Preparation of detailed plans and estimates. On receipt of the administrative sanction to the project detailed hydraulic design calculations for the distribution system using LOOP 4 Software and structural design calculations for the Service Reservoirs and other structures are worked out and the detailed working drawings are prepared in such a way that the construction of works are carried by the construction Engineers without any difficulty. The following plans are to be prepared. 1. Index plan to a scale of 1 cm= 2 km 2. Schematic diagram and flow chart. 3. Detailed plans to a scale of 1 cm = 20m 4. Land plan schedules for Land Acquisitions. 5. Pert chart 6. Quarry map The detailed bill of quantities, technical specification for each work, cost estimate for each component of works and abstract of total cost have to be prepared using COSTDAT and COMEST Software packages. For each estimate, a narrative report can be prepared and appended. The estimate is got technically sanctioned by the competent authority and only after the technical sanction, the project should be taken up for implementations. Conclusion The formulation of a water supply project involves many phases of preparation and appropriate steps taken in all the phases will result in an economical and viable project. (TWAD Board Technical News letter – July 1998 Manual on water supply & Treatment Chapter X of Manual for quality control on Water Supply works)


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3. DESIGN & PLANNING 3.1. Objective (Para 2.1 Of CPHEEO) The objective of a public protected water supply system is to supply safe and clean water in adequate quantity, conveniently and as economically as possible. The water supply projects formulated by the various state authorities and local bodies at present do not contain all the essential elements for appraisal and when projects are assessed for their cost benefit ratio and for institutional or other funding, they are not amenable for comparative study and appraisal. Also, different guidelines and norms are adopted by the central and state agencies; for example, assumptions regarding per capita water supply, design period, population forecast, measurement of flow, water treatment, specifications of materials, etc. Therefore, the CPHEEO Manual on Water Supply & Treatment specify appropriate standards, planning, and design criteria to avoid empirical approach. 3.2 Basic Design Considerations (Para 2.2 Of CPHEEO) Engineering decisions are required to specify the area and population to be served, the design period, the per capita rate of water supply, other water needs in the area, the nature and location of facilities to be provided, the utilization of centralized or multiple points of treatment facilities and points of water supply intake and waste water disposal. Projects have to be identified and prepared in adequate detail in order to enable timely and proper implementation. Optimization may call for planning for a number of phases relating to plant capacity and the degree of treatment to be provided by determining the capacities for several units, working out capital cost required, interest charges, period of repayment of loan, water tax and water rate. Uncertainties in such studies are many, such as the difficulties in anticipating new technology and changes in the investment pattern, the latter being characterized by increasing financing costs. 3.3

Design Period (Para 2.2.6 Of CPHEEO)

Water Supply projects may be designed normally to meet the requirements over a thirty year period after their completion. The time lag between design and completion of the project should also be taken into account which should not exceed two years to five years depending on the size of the project. The thirty year period may however be modified in regard to certain components of the project depending on their useful life or the facility for carrying out extensions when required and rate of interest so that expenditure far ahead of utility is Office of the Principal Accountant General (Civil Audit) Chennai


avoided. Necessary land for future expansion/ duplication of components should be acquired in the beginning itself. Where expensive tunnels and large aqueducts are involved entailing large capital outlay for duplication, they may be designed for ultimate project requirements. Sl No. 1 2 3

4 5 6 7 8 3.4

Items Storage by dams Infiltration works Pumping : i. Pump house (civil works ) ii. Electric motors and pumps Water treatment units Pipe connection to several treatment units and other small appurtenances Raw water and clear water conveying mains Clear water reservoirs at the head works, balancing tanks and service reservoirs (overhead or ground level) Distribution system Population Forecast (Para 2.2.7 Of CPHEEO)

Design period in years 50 50 30 15 15 30 30 15

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The design population will have to be estimated with due regard to all the factors governing the future growth and development of the project area in the industrial, commercial, educational, social and administrative spheres. Special factors causing sudden emigration or influx of population should also be foreseen to the extent possible. A judgment based on these factors would help in selecting the most suitable method of deriving the probable trend of the population growth in the areas or areas of the project from out of the following mathematical methods, graphically interpreted where necessary. a) Demograph Method of population Projection: This method takes into account the prevailing and anticipated birth rates and death rates of the region or city for the period under consideration. An estimate is also made of the emigration from and immigration to the city, growth of city area wise, and the net increase of population is calculated accordingly considering all these factors, by arithmetical balancing. b) Arithmetical Increase Method


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This method is generally applicable to large and old cities. In this method the average increase of population per decade is calculated from the past records and added to the present population to find out population in the next decade. This method gives a low value and is suitable for well-settled and established communities. c) Incremental Increase Method In this method the increment in arithmetical increase is determined from the past decades and the average of that increment is added to the average increase. This method increased the figures obtained by the arithmetical increase method. d) Geometrical Increase Method In this method percentage increase is assumed to be the rate of growth and the average of the percentage increases is used to find out future increment in population. This method gives much higher value and mostly applicable for growing towns and cities having vast scope for expansion. e) Decreasing Rate of Growth Method In this method it is assumed that rate of percentage increase decreases and the average decrease in the rate of growth is calculated. Then the percentage increase is modified by deducting the decrease in rate of growth. This method is applicable only in such cases where the rate of growth of population shows a downward trend. f) Graphical Method In this approach there are two methods. In one, only the city in question is considered and in the second, other similar cities are also taken into account. i) Graphical Method Based On Single City In this method the population curve of the city (i.e. the Population vs. Past Decades ) is smoothly extended for getting future value. This extension has to be done carefully and it requires vast experience and good judgment. The line of best fit may be obtained by the method of least squares. ii) Graphical Method Based On Cities With Similar Growth Pattern In this method the city in question is compared with other cities which have already undergone the same phases of development which the city in questions is likely to undergo and based on this comparison, a graph between population and decades is plotted. g) Logistic Method The 'S' shaped logistic curve for any city gives complete trend of growth of the city right from beginning to saturation limit of population of the city. h) Method of Density


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In this approach, trend in rate of density increase of population for each sector of a city is found out and population forecast is done for each sector based on above approach. Addition of sector-wise population gives the population of the city.

Final Forecast While the forecast of the prospective population of a projected area at any given time during the period of design can be derived by any one of the foregoing methods appropriate to each case, the density and distribution of such population within the several areas, zones or districts will again have to be made with a discerning judgement on the relative probabilities of expansion within each zone or district, according to its nature of development and based on existing and contemplated town planning regulations. Wherever population growth forecast or master plans prepared by town planning or other appropriate authorities are available, the decision regarding the design population should take into account their figures. Note: The calculation sheet for population forecast may be called for and the correctness of population forecast ensured. In TWAD Board, the population forecast was approved by CE concerned. A typical example is given in Annexure1. In circular No.17/F.11168/JE6/P&D/2005 Dt.29.04.2005. TWAD Board had prescribed the following modus operandi for population projection for water supply and sewerage scheme for Rural and Urban Areas. For Urban :The population forecast cannot be generalized for all towns. * The ground reality and present developmental activities of the town and future developments are to be considered during population forecast. * The population projection may be arrived through the following seven methods on minimum four decade population and the best suitable among the derivations may be approved by the competent authority. Different method to be adopted for population projection for Urban Town: i) Arithmetic Increase method ii) Incremental Increase method iii) Line of Fit Method iv) Geometrical Increase Method vi) Semi Log Method vii) Exponential Method viii) Decadal growth Rate Method for state / District average * For a normal town the projection arrived by exponential method is found is to be reasonable and this method may be considered. * Justification note should be appended by the approving authority.


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For rural :Base year population (2006) population Intermediate population (2021) Ultimate population (2036)

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= = =

1.03 time the 2001 census

1.10 time the 2006 population. 1.20 times the 2006 population.

Population Forecast before 2005:(TWAD Board Circular No. 3 P&D/JE-6/2002 dt.08.04.2002.) For Urban:Present population (2001) = population as per 2001 census Intermediate (2016) = to be arrived by different methods Ultimate (2031) with 2001 as the base year. For Rural:Present Population (2001) = population as per 2001 census Ultimate population (2031) = 1.30 times of the present population. 3.5 Per Capita Supply (Para 2.2.8 of CPHEEO) Basic Needs Piped water supplies for communities should provide adequately for the following as applicable: (a) Domestic needs such as drinking, cooking, bathing, washing, flushing of toilets, gardening and individual air conditioning. (b) Institutional needs. (c) Public purposes such as street washing or street watering, flushing of sewers, watering of public parks. (d) Industrial and commercial uses including central air conditioning (e) Fire fighting (f) Requirement for livestock; and (g) Minimum permissible Unaccounted for water (UFW) Recommended Per Capita Water Supply Levels for Designing Schemes.

Sl. No. 1 2

Classification of Towns/Cities Towns provided with piped water supply but without sewerage system Cities provided with piped water supply where sewerage system is existing / contemplated


Recommended Maximum Water Supply Levels (lpcd) Table 2.1 CPHEEO Manual 70 135


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Metropolitan and Mega cities provided with piped water supply where sewerage system is existing / contemplated

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150

Note: (i) In urban areas, where water is provided through public standposts,40 lpcd should be considered: (ii) Figures exclude “Unaccounted for Water (UFW)” which should be limited to 15% (iii) Figures include requirements of water for commercial, institutional and minor industries. However, the bulk supply to such establishments should be assessed separately with proper justification. Per Capita Water Supply Rate Prescribed by TWAD Board. 1 Rural habitations without house service connection (HSC)

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40 litres

2 Rural Habitation with HSC

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55

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3 Town Panchayats (both Rural & Urban )

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70

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4 Municipalities

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90

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5 Corporations

: 120

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3.6 Physical And Chemical Quality Of Drinking Water (Para 2.2.9 of CPHEEO) The physical and chemical quality of drinking water should be in accordance with the recommended guidelines. The Parameters are given in Annexure II Audit Approach •

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The objective of the Water Supply System is to supply safe and clean potable water in adequate quantity conveniently and as economically as possible. Para 2.1 of CPHEEO Manual and also guidelines of the Board prescribes the per capita water supply to the designed period of the population forecast. But while evolving the CWSS/WSS towns and habitations already covered fully for ultimate stage through separate water supply scheme were included in the CWSS. The inclusion of those area already covered under separate Water Supply Scheme in the CWSS was superfluous, involving extra cost on creation of excess size and capacity of pumping main, sump, treatment plants, pumps and motor, etc. By scrutinizing the details of the existing water supply to the towns, habitations included in the CWSS, we can notice the above type of audit observation. By examining the water requirement estimate statement, it could be seen that bulk provision of water was made for many towns and habitations which were already



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provided with Separate Water Supply Scheme and the ultimate stage of water supply had not been completed. In such cases, the necessity for such inclusion should be analysed. Many cases such bulk provisions were not warranted for and the provision of bulk provision remained unutilized which would increase the total requirement of water and ultimately increase the capacity of pumping main, treatment plant, sump, pump and motors, etc. involving extra cost. A town may already been provided with water Supply Schemes for ultimate stage. To meet the shortfall if any, bulk provision was made in another CWSS which was under execution. In the meantime, another separate water supply improvement scheme was sanctioned and executed under another scheme. Thus cost involved in execution of the latter improvement scheme except cost on creation of distribution system was wasteful. This type could be brought out by close study of various water supply schemes & CWSS sanctioned and executed. Duplication in creation of infrastructure due to formulating separate improvement scheme while existing scheme itself functioning well and had not completed its designed service life of 30 years (Ultimate stage). Para 2.2 of CPHEEO Manual stipulates that the water supply projects shall be designed to meet the requirement for the population forecast at the prescribed per capita supply over a period of 30 years after their completion and prescribes the methods of forecasting the population during the period of design on the basis of latest census. Instead of designing the Schemes as per the provisions of the Manual, Water Supply Schemes sanctioned upto 2002 were designed taking base year as 1996/1991 and ultimate year as 2026/2021. This resulted in utilisation of infrastructure created for period much lesser than the prescribed 30 years. Para 2.2.6 of CPHEEO Manual provides for designing Water Treatment units, clear water reservoirs at head works, balancing tanks (Sump) and Service Reservoirs of the Water Supply Projects for 15 years (intermediate Stage) to facilitate carrying out extensions when required and avoid expenditure far ahead of utility and interest on capital. But treatment plant, clear water sumps and service reservoirs were designed and constructed for 30 years (Ultimate stage). Thus creation of infrastructure far ahead of requirement was avoidable and wasteful. Appendix 6.5 of CPHEEO Manual and PWD Code stipulates that the life of electric motor and pump is 15 years. As the electric motors and pump would lose their efficiency after 15 years of service life, erection of pump and motor for ultimate stage was wasteful and cost involved on execution of pump and motor for ultimate stage become wasteful. Para 7.1 of CPHEEO Manual specifies the water treatment units which includes aerator, clariflocculator, filter, disinfector, softener, etc. The treatment plant constructed by Board comprised of those units. But they were constructed for ultimate requirements as against the intermediate requirements prescribed by CPHEEO Manual resulting in extra cost. Clear water is collected in a sump before it is pumped to Service reservoir (vide Para 6.3.7 of the Notes on Water Supply Scheme issued by CE, PWD Chennai in 1971). Intermediate sumps are also constructed to reduce the pressure in the transmission main. The sump shall be designed for intermediate stage and its capacity depends on the discharge into the sump and detention time (discharge in lpm x detention time in


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minutes). On a audit enquiry, the CE, TWAD Board, Southern Region, Madurai informed (November 2003) that the capacity of sump are designed generally for 30 to 60 minutes storage and storage period would vary depending on various factors such as hours of pumping, availability of power, and separate feeder main for power supply etc. Audit Scrutiny also disclosed that clear water sumps were designed for 15 to 180 minutes eventhough separate feeder main to provide 24 hours power supply was available and also constructed for the requirement of ultimate stage instead of intermediate stage involving extra cost. Para 10.4.2 and Appendix 10.1 of CPHEEO Manual prescribes guidelines for estimation of storage capacity of the service reservoirs which depends on hours of pumping, demand and hours of supply, and shall be constructed for intermediate stage only. Para 19.3 of Notes on Water Supply Schemes issued by the Chief Engineer (PWD) Chennai in 1971 also indicates that the capacity of Service Reservoir is fixed on the basis of hours of pumping and the peak rate of supply. The peak rate of supply is usually taken to be twice the average rate and the capacity of service reservoir is fixed at 8 hours or one third of a day’s supply. The guidelines issued by Board in December 1982 also stipulated that the capacity of overhead service reservoirs in rural areas of a CWSS should be 50 per cent of the ultimate daily requirement of the individual habitation considering the limited hours of power supply. As such the capacity of service reservoir shall be one third of a day’s supply for intermediate stage in urban areas and half of the day’s supply for intermediate stage in rural areas of CWSS. But it is noticed that service reservoirs were designed and constructed for the requirement of ultimate stage instead of intermediate stage. In rural habitation covered under CWSS, the service reservoirs were designed and constructed for ultimate stage adopting the norms prescribed by Board in May 1998. For construction of overhead tank (OHT), service reservoirs in rural water supply power pump scheme which prescribed the capacity of OHT/SR on the basis of ultimate population of the range 150-500, 501-1250 and 1251-2500 at 10000, 30000 and 60000 litres capacity respectively. Construction of SR for ultimate requirement and also not observing the norms resulted in extra cost on construction of Service Reservoirs of higher capacity. Para 2.2.8.3 of CPHEEO Manual recommends, per capita supply level for designing water supply schemes. The norms prescribed by Government of India under Rural Water Supply Schemes and also by Board in July 1998 stipulated for 40 lpcd. Whereas in case house service connection was provided for, it can be increased to 55 lpcd. But cases where all infrastructures were created adopting 55 lpcd, but house service connections were not effected subsequently. It should be verified whether specific undertaking was obtained from the local bodies before designing the CWSS adopting 55 lpcd. If not extra capacity involved could be objected to. Cases where water supply scheme was designed adopting 1991 population as base year and actual requirement of the water in the initial reaches was not correctly worked. At the time of completion of the Scheme, the people in the initial reach would draw more water than the designed level. Cases of non-estimation of the actual requirement of water to the intended habitation were also available. Consequently water could not reach the tail end or intermediatary reaches. This necessitates laying far separate feeder main, intermediatary sump to regulate water


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supply. The extra cost involved on this could be analysed and commented. This was due to poor investigation, defective design and execution and failure to assess the actual requirement before executing the work.

DESIGN: Appendix 11.1 of CPHEEO Manual stipulated for designing the pumping main for 23 hours of pumping considering loss of one hour due to tripping and other minor interruption. Para 19.1 of the Note on Water Supply Schemes issued by the Chief Engineer (PWD), Chennai in 1971 also stipulates that pumping main can be designed to discharge 24 hours if service reservoirs are provided. In June 2002, Board had also instructed to design the CWSS for 20 hours of pumping if separate feeder main for power supply was provided. But with a view to provide cushion, pumping mains were designed for 16 to 20 hours pumping eventhough separate feeder main for power supply to pumping station connected with industrial line having 24 hours power supply. Due to reduction in hours of pumping the size of pumping main, pump sets and sumps had to be designed and constructed for higher capacity/size. Had 23 hours of pumping adopted, the discharge for the ultimate requirement would be much lesser and the infrastructures viz. Pumping main, Pump sets and Sump could have been designed and constructed at lesser capacity. NOTE: Upto 1998-99, TWAD Board had prescribed unit rate for various items of work which was dispensed with from 1999-2000 and comprehensive common Schedule of Rates for each items . Hence it is not possible to work out the extra cost on creation of assets for ahead of the requirement easily. Hence the unit rate prescribed by Board is adopted as basis from which the proportionate cost is worked out on the agreement value adopting ratio of proportion which would give the cost of construction of the required capacity of assets. The difference would give the extra cost. In letter No.101/P&D/98 dated 29.9.1998, TWAD Board communicated unit rates for various items of work for preparation of outline proposals for various components of urban and rural water supply schemes for the year 1998-99.


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4. SOURCE OF WATER (Chapter 5 of CPHEEO Manual & chapter VII of Manual for Quality Control in Water supply works) The sources for the water supply scheme are generally of the following two categories; 1. Surface water sources 2. Sub surface water sources 1.Surface water source Surface Water sources are from rivers lakes and reservoirs. The water from these sources are drawn and supplied the beneficiaries after proper treatment. If the river is not perennial, the storage of water is necessary for supplying during the dry period. Generally surface water is preferred for the following reasons. 1. When quality of ground water available in and around the beneficiary is not potable. 2. When large quantity of water is required for the scheme. 2. Sub surface water source In geological nature, Tamilnadu State can be categorized as hard rock areas, and sedimentary areas. The hard rock areas cover 73% area of the state and the sedimentary formations cover the remaining 27% area of the state. The sub-surface water is being tapped from the following sources. 1. 2. 3. 4.

Open wells Bore wells Infiltration wells and Collector wells

2.1 Guidelines for location of infiltration well (TWAD Circular No 2/DO/P&D/2001 dt 5.2.2001) The following procedures are to be followed in geophysical investigation for fixing up the location of an Infiltration well.



1.Resistively survey with geophysical equipment are carried out in grid pattern in the river bed/bank to assess the apparent resistively of the sub-surface strata and fixing location. 2.After conducting geo survey, probing is to be done to assess the sand depth where the maximum is seen. 3. In the selected location of the probing where the maximum sand depth exist, the trial bore wells are to be drilled and soil samples analysed. The water sample should also be collected and analyzed for assessing the potability of water. 4. From the trial bore well, location of the proposed infiltration well have to be located. 5. At the selected point, the confirmatory bore well to be drilled not only at the centre of the infiltration well but also in the periphery atleast six borewells. 6. Lithology of the trial bore wells should be prepared and the depth of the saturated sand is analyzed. 7. The summer water level of the area of the investigation with reference to the saturated thickness is correlated. 8. The depth of the infiltration well depends on the saturated thickness of the area. 9. Yield from an infiltration well sunk for 3.5 m diameter in saturated aquifer of 4m depth for a draw down of 2m is computed approximately as 1000 lpm.

10. The location of the infiltration well should be located in such a way to avoid interference between structures

2.2 Design criteria for Collector Wells Collector wells with radial arms are generally proposed in river basins to tap maximum yield from deep saturated aquifer. This type of sources are proposed when the quantity of water requirement is very huge. Here also confirmatory bores have to be drilled to identify the depth of aquifer and to locate exact depth at which the radial arms to be driven. Design Criteria Diametre Thickness of well staining Number of laterals Length of laterals

-

Size of laterals

-


4 to 6 45 to 60cm 8 to 16 (in radial directions) 20 to 60m depending (upon the saturated thickness of aquifer) 200 to 300mm dia slotted pipes.

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Permissible velocity of flow in laterals 0.06 mps Slot in laterals 16% of the surface area of the laterals Note : The number, length and size of the laterals can be determined to obtain the required yield from the source.

3. Safe Yield In all type of wells after completion of the construction, yield tests have to be conducted and safe yield has to be arrived after applying the correction factors. Depending upon the yield the required number of wells may be decided to supply the quantity required for the scheme. The CPHEEO Manual prescribes two types of safe ;yield tests for determining safe yield of the well viz. Pumping (Discharge) Test & recuperation test. 3. 1 Safe yield in Bore wells (Datamatrix of TWAD Board Engineers) For power pump schemes, the following multiplication factors have been evolved to arrive safe yield for the borewells drilled in hard rock area. When the yield test is conducted during summer months i.e. April – August a factor of 0.9 may be adopted to the observed yield for determining the safe yield from borewell. For the yield tests conducted during other months a correction factor of 0.6 may be applied, for arriving at the safe yield. In case of Kanyakumari district the correction factor will be 0.9 for the months from March of June and it will be 0.6 for other months. 3.2.Pum ping Test (Discharge Test) Pumping test is the most accurate, reliable and commonly used method to evaluate the hydraulic parameters of an aquifier, efficiency of a well, safer operational rates of pumping and selection of suitable pump. The methodology of a pumping test is highly varying in its application. The objective is limited to determine the aquifer parameters such as transitivity (T), Storage co-efficient (S), hydraulic conductivity (K) and well performance and safe yield for execution of water supply scheme. To study the parameters of transitivity, storage co-efficient and hydraulic conductivity, generally a constant discharge pumping test (aquifier performance test) is conducted. An aquifer performance test consists of pumping a well at certain constant rate and recording the drawdown both in pumping well and in the near by observation wells at specific times. To analyze the well performance, the step drawdown test (well performance test) is carried out. In step drawdown test, the drawdown in a pumping well is recorded at variable discharge in steps.


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Efficiency of the well is the ratio of the critical drawdown (drawdown just outside of the casing) and actual drawdown measured in a well at a designed discharge of continuous pumping for a given period. Recuperation Test After the constant discharge test, when the pump is shut down, the water column in the well or borewell started rising. This rise in water column has to be noted in close intervals. The data collected on recouping water column will be useful to compute the aquifer parameters. Recuperation test are recommended for large diameter open wells. The bore wells/ open wells executed for major schemes are subjected to pumping tests. Pumping tests are also conducted before and after the hydro fracturing operations. Note:The result of discharge test of the well measured in ‘V’ notch would be recorded in the prescribed table and the specific yield in lpm per cm of draw down derived from the table. This would be verified from the pumping test report and ensure safe yield of the well. In a similar manner specific yield obtained from Recuperation test in the well should be ascertained and the safe yield adopted by comparing both the report. Minimum Distance of well from source of Contamination Contamination of Sources Building sewer Septic tank Disposal field Seepage pit Cesspool

Recommended distances (in metres) 15 15 30 30 45

Audit Approach •

According to the instruction of TWAD Board in B.P.No.75 dt.25.03.1990 various components of water supply scheme shall be executed after ensuring adequate quantity and quality of source. However, without ensuring the availability of adequate quantity of potable water, the pumping mains distribution system, overhead service reservoir etc work constructed resulting in unfruitful expenditure.

•

To ensure whether, sources (Borewell, collector well, infiltration well) created in conformity with the specification mentioned above. Analyze the failure to observe the guidelines and resultant financial and social objective implication.


19


•

Whether dependability and reliability of the source, quality of source ensured before creation of other infrastructures which ultimately resulted in wasteful expenditure on creation of infrastructures.

•

Whether proper investigation and test carried out to ensure reliable source to the designed quantity and factors affecting contamination of source which subsequently resulted in making the water not potable examined. The remedial measures proposed/taken has also to be analysed.

•

Whether permission was obtained from the District Collector/Water Utilisation Committee for drawal of water to the designed quantity.

5.Transmission of Water (Chapter 6 of CPHEEO Manual) Water supply broadly involves transmission of water from the sources to the area of consumption through free flow channel or conduits or pressure main. Pipe line normally follow the profile of the ground surface quite closely. Gravity pipelines have to be laid below the hydraulic gradient. Pipes are of Cast Iron, Ductile Iron, mild steel, Prestressed concrete, reinforced cement concrete, GRP asbestos cement, plastic, etc. 5.1 Hydraulic of Conduits ( Pipe ) (PARA 6.2. OF CPHEEO Manual) The design of supply of conduits is dependent on resistance to flow, available pressure or head allowable velocities of flow, scour, sediment transport, quality of water and relative cost.. Velocity:There are a number of formulas available for use in calculating the velocity of flow. However Hazen – William formula for pressure conduits and Manning’s formula for free flow conduits have been popularly used. a) The Hazen – William formula is expressed as V= 0.849 C r0.63 S0.54 For circular conduits, the expression becomes V= 4.567 x 10-3 C d 0.63 S 0.54 And Q = 1.292 x 10-5 C d 2.63 S0.54 Where Q = discharge in cubic metre per hour d.=diameter of pipe in mm V = Velocity in MPS r.= hydraulic radius in m or hydraulic mean depth in meter = water area wetted perimeter S = Slope of hydraulic gradeline C= Hazen-William co-efficient 5.2 Coefficient of Roughness (`C’ Value) (Para 6.2.2 of Cpheeo)


20


The co efficient of roughness (`C’ Value ) depends on Reynolds number and relative roughness. The Metallic pipes lined with cement mortar or epoxy and concrete pipe behave as smooth pipes. To reduce corrosion, increase smoothness and prolong the life of pipe materials, the metallic pipes are being provided with durable smooth internal lining. Unlined metallic pipes under several field conditions such as carrying water having tendency for incrustation and corrosion, low flow velocity and stagnant water under go substantial reduction in their carrying capacity with age. The value of the Hazen-William co-efficient `C’ value for new conduit materials and the value to be adopted for design purposes are given below. Hazen-Williams Co-efficient (Table 6.1 of CPHEEO Manual) Pipe Material Unlined Metallic pipes Cast Iron, Ductile Iron Mild Steel Galvanized Iron above 50mm dia Galvanized Iron 50mm dia and Below used for house service connections

Recommended `C’ Value New Pipes Design purpose 130 140 120 120

100 100 100 55

140 145

140 145

130

110

140 145 150 150

140 145 140 145

Centrifugally Lined Metallic Pipes Cast Iron, Ductile Iron and Mild Steel pipes Lined with cement mortar or Epoxy Upto 1200 mm dia Above 1200 mm dia Projection Method Cement Mortar Lined Metallic pipes Cast Iron, Ductile Iron and Mild Steel pipes Non Metallic pipes RCC spun concrete, prestressed Concrete Upto 1200 mm dia Above 1200 mm dia Asbestos Cement PVC, GRP and other Plastic pipes

5.3 Modified Hazen – Williams Formula (Para 6.2.4 Of Cpheeo) Hazen William formula has inherent limitation and under utilization. Hence the modified Hozen Williams formula has been derived from Darcy – Weisbach and Colebrook – white equations and obviates the limitations of Hazen – Williams formula. The modified Hazen Williams formula derived for circular conduits as V= 143. 534 CR r 0.6575 S 0.5525 H = [ L ( Q / CR) 1.81 ] / 994.62 D 4.81


21


In which, V = velocity of flow in m/s ; CR = pipe roughness coefficient; ( 1 for smooth pipe; < 1 for rough pipes); r = hydraulic radius in m; S = friction slope; D = internal diameter of pipe in m; H = friction head loss in m; L = length of pipe in m; and Q = flow in pipe in m3/ s. A nomograph for estimation of head loss by Modified Hazen - Williams formula is presented in the Appendix 6.3 of CPHEEO manual

5.4 Effect of Temperature on Coefficient of Roughness ( 6.2.5 of CPHEEO) Analysis carried out to evaluate effect of temperature (viscosity) on value of CR reveals that the maximum variation of CR for a temperature range of 10o C to 30o C is 4.5% for a diameter of 2000 mm at a velocity of 3.0 m / s In the light of this revelation, CR values are presented for average temperature of 20o C. 5.5 Experimental Estimation of CR Values ( 6.2.6 OF CPHEEO) The coefficients of roughness in various pipe formulae are based on experiments conducted over a century ago. The values of Hazen Williams, C, Mannings n and roughness k values in Moody’s Diagram have also been used on experimental data collected in early nineteenth century. There have since been major advances in pipeline technology. Both the manufacturing processes and jointing methods have improved substantially over the years and newer pipe materials have come into use. Continued usage of roughness coefficients estimated without recognition of these advances is bound to result in conservative design of water supply systems. Accordingly CR values of commonly used commercial pipe materials have been experimentally determined in a study conducted within the country. This study covered pipe diameters 100 to 1500 mm over a wide range of Reynold’s numbers ( 3 x 104 to 1.60 x 106 ) encountered in practice. The results indicate that centrifugally spun CI, RCC, AC and HDPE pipes are hydraulically smooth when new and hence, CR = 1 for these pipes. The use of Hazen Williams “ C” as per Table 6.1 results in under utilization of above pipe material when new. The extent of under utilization varies from 13 to 40 percent for CI pipes, 23 percent for RCC and AC pipes; and 8.4 percent for HDPE and PVC pipes. The `C’ Value is the main contributory factor for deciding the size of the pipe. In case the `C’ value is understated the size of the pipe would automatically increase. The increase in discharge quantity of lined CI pipe is 40/45 per cent when compared to unlined CI pipes. Since the quantity to be discharged in the design of a particular section of pumping main remains constant, there would be


22


scope for reduction in diameter of the pipes used in that section. If the quantity of discharge and head lose were kept constant, the diameter of the pipes would be reduced using Hazen-Williams formula. The following expression may be used to determine the reduced diameter of pipes when `C’ value is increased. .d1= [c/c1 d2.63]1/2.63 (derived from Hazen William formula) where d= Diameter of pipe in mm as adopted in the design d1 = reduced diameter when `C’ value is increased c= `c’ value adopted in the design c1= Correct `C’ to be adopted as per CPHEEO manual Illustration: Consider a pumping main with following parameters: Water to be discharged (k) = 4365 lpm Head loss (s) = 1/700 `C’ Value adopted ( C) = 100 Pipe used CI pipes (lined ) = 400 mm dia Velocity (v) = 0.579 m/sec Since `C’ value for lined pipes is 140 ,there would be scope for reduction in diameter of the pipe. It is to be noted that while reducing the diameter of the pipe we have to keep the Quantity of water to be discharged as constant. The hydraulic gradient may be kept constant or it may be increased. (1) Note: Hazen William formula : Q = 1.292 x 10-5x, cd2.63 x S0.54 If Q (Discharge) and S (hydraulic gradient are kept constant and C value is changed Then Q = 1.292 x 10-5 x C1d2.63 xS0.54 …….(2) (1) divided by (2) 1= cd2.63/c1d12.63 d12.63=c/c1 d2.63 : d1= [c/c1 d2.63]1/2.63 The hydraulic gradient should not be reduced as it would cause increased pressure head which necessitate higher capacity pump sets and consequent additional expenditure. Hence while attempting reduction of size of pipe by increasing the `C’ value, care should be taken to keep both quantity of discharge and head loss as constants. Adopting the formula d1 =[c/c1 d2.63]0.38 Diameter of the pipe for C value of 140 would be d1=[1/1.4 (400)2.63]0.38 (4980693)0.38=350.73 mm or 350mm Thus the dia meter of the pipe is reduced from 400 mm to 350 due to increase of C value from 100 to 140. However we must ensure that due to reduction of size of pipe, the velocity should not be increased beyond limits. For


23


this, another expression of Hazen William formula (i.e.) V= 4.567 x 10-3c d0.63 x s0.54 Where d=350 mm and s= 1/700 Therefore V = 4.567 x 10-3 x 140 (350)0.63 x (1/700)0.54 4.567 x 10-3 x 140 x 3500.63 x (1/700)0.54 = 4.567 x 10-3 x 140 x 40.06 x 0.029 = 0.745 m/sec which is within normal limits adopted by TWAD Board. A typical discharge table for different size of pipe is given in Annexure IV

5.6 Reduction in Carrying Capacity of Pipes with Age. ( 6.2.7 of CPHEEO) The values of Hazen – Williams “C” are at present arbitrarily reduced by about 20 to 23 percent in carrying capacity of pipes with age. Studies have revealed that chemical bacteriological quality of water and velocity of flow affect the carrying capacity of pipes with age. The data on existing systems in some cities have been analyzed along with the experimental information gathered during the study, to bring out a rational approach to the reduction in carry capacity of pipes with age. The CR values obtained in such studies have shown that, except in the case of CI and steel pipe while carrying corrosive water, the current practice of arbitrary reduction in “C” values as per Sec. 6.2.2. results in under utilization of pipe material to the extent of 38 to 71 percent for CI pipes for non corrosive water; 46 to 93 percent for RCC pipes and 2 to 64 percent for AC and HDPE pipes. 5.7. Design Recommendations for Use of Modified Hazen-Williams Formula ( 6.2.8 OF CPHEEO) The following design recommendations are made to ensure effective utilization of pipe carrying capacity. i) ii)

New CI, DI steel, RCC, AC and HDPE pipes behave as hydraulically smooth and hence CR of 1 is recommended. For design period of 30 years, no reduction in CR needs to be effected for RCC, AC, PVC and HDPE pipes irrespective of the quality of water. However, care must be taken to ensure selfcleansing velocity to prevent formation of slimes and consequent reduction in carrying capacity of these pipes with age.


24


iii)

For design period of 30 years, 15 percent reduction is required for unlined CI & DI pipes if non corrosive water is to be transported. The design must also ensure self cleansing velocity. iv) While carrying corrosive waters, unlined CI, DI and steel pipes will loose 47 and 27 percent of their capacity respectively over a design period of 30 years. Hence, a cost trade-off analysis must be carried out between chemical and bio-chemical correction of water quality, provision of a protective lining to the pipe interiors and design at reduced CR value for ascertaining the utility of CI, DI and steel pipe material in the transmission of corrosive waters. Recommended CR values are presented in Table 6.4 The use of the recommended values in conjunction with Modified Hazen-Williams formula or the nomograph will permit fuller utilization of pipe materials.

RECOMMENDED CR VALUES IN MODIFIED HAZEN-WILLIAMS FORMULA( AT 20 oC) Diameter (mm)

To

CR value when New

0.3

1.8

1.00

CR value for Design period of 30 years 1.00

600

0.3

2.0

1.00

1.00

20

100

0.3

1.8

1.00

1.00

100

1000

0.3

1.8

1.00

0.85*

100

1000

0.3

1.8

1.00

0.53 *

100

2000

0.3

2.1

1.00

1.00

100

600

0.3

2.1

1.00

1.00

15

100

0.3

1.5

0.87 (*)

0.74

Sl. No

Pipe material

From

To

1

RCC

100

2000

2

AC

100

3

HDPE and PVC

4 5

6 7 8

CI/DI ( for water with positive Langelier’s index) CI/DI ( for water with negative Langelier’s index) Metallic pipes lined with cement mortar or epoxy ( for water with negative Langelier’s index) SGSW GI ( for water with negative Langelier’s index)

Velocity ( m/s) From

(*) These are average CR values which result in a maximum error of + - 5 % in estimation of surface resistance. 5.8 Guidelines for Cost Effective Design of Pipelines. The cost of transmission and distribution system constitutes a major portion of the project cost. It is desirable to adopt the following guidelines. i) The design velocity should not be less than 0.6m /s in order to avoid depositions and consequent loss of carrying capacity.


25


ii) In design of distribution systems, the design velocity should not be less than 0.6m/ s to avoid low velocity conditions which may encourage deposition and / or corrosion resulting in deterioration in quality. However, where inevitable due to minimum pipe diameter criteria or other hydraulic constraints, lower velocities may be adopted with adequate provision for scouring. iii) In all hydraulic calculations, the actual internal diameter of the pipe shall be adopted after accounting for the thickness of lining, if any instead of the nominal diameter or outside diameters ( OD). iv)In providing for head loss due to fittings, specials and other appurtenances, actual head loss calculations based on consideration included in subsection 6.2.9. should be done instead of making an arbitrary provision.

5.9 Pipe Materials ( Para 6.3 Of CPHEEO) Pipelines are major investments in water supply projects. Therefore pipe materials shall have to be judiciously selected not only from the point of view of durability, life and over all cost which includes, the pipe cost, the installation and maintenance costs necessary to ensure the required function and performance of the pipeline throughout its designed life time. Choice of Pipe Materials Types of Pipes: The various types of pipes used are: a. Metallic pipes : C.I., D.I., M.S., G.I. i)Unlined Metalic pipes. ii)Metallic pipes lined with cement mortar or epoxy lining b. Non Metallic pipes i) Reinforced Concrete, Prestressed Concrete, Bar wrapped Steel Cylinder Concrete, Asbestos Cement. ii) Plastic pipes : PVC, Polyethylene, Glass Reinforced Plastic, etc. Selection of Pipes * Several technical factors affect the final choice of pipe material such as internal pressures, coefficient of roughness, hydraulic and operating conditions, maximum permissible diameter, internal and external corrosion problems, laying and jointing, type of soil, special conditions, etc.


26


*

Selection of pipe materials must be based on the following considerations: a)The initial carrying capacity of the pipe and its reduction with use, defined, for example, by the Hazen – Williams coefficient. C. Values of C vary for different conduit materials and their relative deterioration in service. They vary with size and shape to some extent. b) The strength of the pipe as measured by its ability to resist internal pressures and external loads. c)The life and durability of pipe d)The case of difficulties in transportation, handling and laying and jointing under different conditions of topography, geology and other prevailing local conditions. e)The safety, economy and availability or manufactured sizes of pipes and specials f)The availability of skilled personnel in construction and commissioning of pipelines. g)The ease or difficulty of operations and maintenance.

The life and durability of the pipe depends on several factors including inherent strength of the pipe material, the manufacturing process along with quality control handling transportation laying and jointing of the pipeline surrounding soil conditions and quality of water. Normally the design period of pipelines is considered as 30 years. Lined metallic pipelines are expected to last beyond the normal design life of 30 years. However, the relative age of such pipes depends on the thickness and quality of lining available for corrosion. The cost of the pipe material and its durability or design life are the two major governing factors in the selection of the pipe material. The pipeline may have very long life but may also be relatively expensive in terms of capital and recurring costs and, therefore, it is essential to carryout a detailed economic analysis before selecting a pipe material. The metallic pipes are being provided with internal lining either with cement mortar or epoxy so as to reduce corrosion, increase smoothness and prolong the life. Underground metallic pipelines may require protection against external corrosion depending on the soil environment and corrosive ground water. Protection against external corrosion is provided with cement mortar guiniting or hot applied coal-tar asphaltic enamel reinforced with fiberglass fabric yarn. The determination of the suitability in all respects of the pipeline for any work is a matter of decision by the Engineer concerned on the basis of the requirements for the scheme. It is necessary that a quantitative and qualitative assessment is made to arrive at the most economical and reliable pipe materials. The check list for selection of pipe materials prescribed in table 6.7 of CPHEEO is to be prepared to the facilitate the decision makers in selecting the


27


economical and reliable pipe materials for the given condition and it is strongly recommended for large and medium projects more than 15 mld. Risk factors should be identified clearly in the project report. Risk analysis should be carried out to arrive at the correct decision in selecting the pipe material. 1. Cast Iron (CI) Pipe (Para 6.4. CPHEEO) CI pipes are vertically cast or centrifugally cast. Vertically cast Iron pipe shall confirm to IS 1537 – 1976 and the centrifugally cast spun iron pipe shall confirm to IS 1536: 2001. Vertically cast Iron pipes has been largely superceded by centrifugally spun cast iron pipes. Centrifugally cast iron (spun) pipe is available and manufactured to a diameter of 80mm to 1050mm. The CI pipe have been classified as LA, A and B classes according to their wall thickness. Class LA pipe have been taken as the basis for classification of pipe Class A pipe more 10% and Class B have 20% increase in thickness over Class LA. Widely used because of its good casting qualities and continue to give satisfactory service even after a century of use. The pipes are Spigot and socket type Several type of joints such as rubber gasket joint known as Tyton joints, Mechanical joint and conventional joint know as Lead joints are used. used for carrying potable water, sewer main etc. 2. Steel Pipe ( Para 6.5 of CPHEEO) Manufacture of steel pipes shall be with mild steel plate grade Minimum tensile strength of 330 mpa, 410 mpa & 450 mpa confirming to IS 2062. ( Steel plate of Minimum tensile strength of 410 mpa is normally used) Larger size of pipe are made by welding together the edges of suitably curved plates as per IS 3589: 2001. IS 3589 : 2001 stipulates the nominal size of steel pipe ranging 168.3mm to 2540mm outer diameter with varying thickness of plate 2.6mm to 25mm. To be provided protection against corrosion. As against internal corrosion rich cement mortar or epoxy lining should be done internally by centrifugal process. The outer coating for under ground pipe line may be in cement - sand guiniting or not applied coal-tar asphaltic enamel reinforced with fibre glass fabric yarn. Small size of pipe having threaded ends could be joined with jointed materials like yarn.


28


3. Ductile Iron Pipes ( 6.6 Of CPHEEO) Ductile iron confirming to IS 8329 : 2000 specification prescribes standards for centrifugally cast ductile iron pipe ( DI pipe). DI pipes are available in the range of 80mm to 1000mm diameter and in length of 5.5 to 6m. DI pipes are normally provided with cement mortar lining at the factory by centrifugal process. DI pipe have excellent properties of machinability, impact resistance, high wear and tear resistance high tensile strength, ductility and corrosion resistance. Free from cracks. These pipes are approximately 30% lighter than conventional CI pipes. DI fittings are manufactured conforming to IS 9523 : 1980 and the laying and jointing done as in the case of CI pipe ( viz. rubber gasket etc.)

4. Asbestos Cement (AC) Pipes ( Para 6.7 of CPHEEO) A.C. pipes conforming to IS : 1592 – 2003 was made of a mixture of Asbestos paste and cement compressed by steel roller to form laminated material of great strength and density. AC pipe are manufactured from class 10 to 25 and nominal diameters of 50mm to 1000mm with test pressure of 10 to 25 kg / cm 2. AC pipes are classified as class 10,15,20 & 25 kg / cm 2 respectively. Working pressure shall not be greater then 50% of the test pressure for pumping mains and 67% for gravity main. AC pipes have two type of joints cast iron detachable ( CID) joints and AC coupling joints. 5. Concrete Pipe ( Para 6.8 of CPHEEO) Reinforced cement concrete ( RCC ) pipes are classified as P1, P2 and P3 with test pressure of 2,4 and 6 kg / cm2 respectively. For use as gravity main, the working pressure should be 2/3 of the test pressure and for the pumping main, the working pressure should not exceed half of the test pressure. Jointed with RCC collars with jute yarn rope dipped in Cement mortar. 6. Pre stressed Concrete (PSC) Pipe ( Para 6.9 of CPHEEO) The PSC pipes are ideally suited for water supply mains where pressure in the range of 6 kg / cm2 to 20 kg / cm2 are encountered. PSC pipes consists of a concrete lined steel cylinder with steel joint rings welded to its ends wrapped with a helix of highly stressed wire and coated with dense cement mortar or concrete.


29


PSC pipes are jointed with flexible rubber rings. Confirming to IS 784 : 2001 specification. PSC pipe competes economically with steel for pipe diameter of 600mm and above. The PSC pipes are classified as 4 KSC, 6 KSC, 8 KSC, 10 KSC, 12 KSC, 16 KSC, 18 KSC, and 20 KSC pipe and that denotes the working pressure excluding surge pressure and the site test pressure will be 1.5 times of the above working pressure vide IS 784 : 2001. 7. Bar Wrapped Steel Cylinder Pipes (BWSC Pipes) (Para 6.9.4 Of CPHEEO) (IS: 15155-2002) Bar wrapped cylinder pipes (BWSC pipes) are being manufactured as per IS 15155-2002. BWSC pipe is a modified version of PSC pipes with steel cylinder embedded in it. The joints are welded and covered with cement mortar coating. The joints are more reliable than conventional rubber ring joints. The O&M expenditure would be less. It is advantagements to use BWSC pipe in water supply and sewerage projects on grounds of good hydraulic properties, long life better corrosion resistant properties etc., The BWSC pipe have been introduced as approved pipe material in TWAD schedule of rates for the year 2004-05, In Circular NO.43/AC/P&D/2005 Dt.04.10.2005, TWAD Board directed that the use of BWSC pipe has to be encouraged in water supply and sewerage projects in view of its techno economic advantage and lesser O&M cost. The technical committee instructed to consider BWSC pipe as are of the alternative in water supply and sewerage projects with Techno economic consideration. 8. Plastic Pipes ( Para 6.10 Of CPHEEO) Poly Vinyl Chloride ( PVC ) pipe conforming to IS 4898 – 1988. PVC pipe have advantages of resistance to corrosion, light weight, toughness, rigidity, economical in laying, jointing and maintenance, case of fabrication. Available in size of outer dia 20 to 315mm at working pressure of 2.5, 4, 6, 10 kg / cm2. Superior compared to conventional pipe especially AC. Jointing of PVC can be made by solvent cement, rubber ring joint, flanged joints, threaded joints. For bedding pipe trench is filled with sand and compacted by tapping with wooden stick. Note: In Circular No.42/DO/P&D/2005 Dt.04.10.2005. TWAD Board instructed to considered PVC pipe upto 315 mm OD as one of the alternative in water supply and sewerage projects with techno economic consideration. 9. Polyethylene Pipes ( Para 6.11 of CPHEEO) • High density polyethylene pipe ( HDPE) has excellent free flowing properties.


30


• Required for water distribution system ranging from 15-150mm dia and occasionally upto 350mm Conforming to IS 4984 – 1987. They can withstand movement of heavy traffic HDPE pipes can be jointing by welding. 10. Medium Density ( MDPE) PIPE ( para 6.11) Manufactured conforming to ISO 4427 specification for carrying potable water. The pipes are supplied in coil. 11. Glass fibre reinforced plastic (GRP)Pipes ( 6.12 of CPHEEO) GRP pipes are now manufactured in India conforming to IS 12709. The diameter range is from 350mm to 2400mm. The pressure class is 3,6,9,12 & 15 kgs / Sq.cm. The factory test pressures are 4.5,9,13.5, 18, 22.5 kg / sqcm. The factory test pressures are 6, 12, 18, 24 and 30 kgs / sq.cm. Standard length are 6 and 12 meter. Widely used in foreign countries. GRP pipes are corrosion resistant and have smooth surface and high strength, lighter in weight. Pipes are jointed by using double bell coupling. 12. G.I. Pipe. The pipe shall be galvanized mild steel not finished seamless or welded or screwed and socketed conforming to the requirement of IS 1239 (Part.I) for medium grade Shall with stand a test pressure of 50 kg / cm2 Normally used for hill areas. 5.10.Structural Requirements ( Para 6.13.1) Structurally closed conduits must resist a number of different forces singly or in combination. a) Internal pressure equal to the full head of water to which the conduit can be subjected ( ie. Hydrostatic Test pressure). b) Unbalanced pressure at bends, constructions and closures which have been discussed in 6.16.18 of CPHEEO Manual. c) Water hammer d) External load in the form of back fill, traffic and their own weight between external supports (Piers or hangers). e) Temperature induced expansion and contraction. Internal pressure including water hammer creates transverse stress or hoop tension. Bend and closures as dead ends of gates produce unbalanced pressures


31


and longitudinal stress. When conduits are not permitted to change length, variations in temperature like wise create longitudinal stress. External loads and foundation reactions ( Manner of support ) including the weight of the full conduit and atmospheric pressure produce flexural stress. 5.11 Depth of Cover: ( 6.13.4 Of CPHEEO) One meter cover on pipeline is normal and generally sufficient to protect the pipe lines from external damage. When heavy traffic is anticipated, depth of cover has to be arrived at taking in to consideration of the structural and other aspects as detailed in 6.13.2 CPHEEO Manual. When freezing is anticipated 1.5m cover is recommended. 5.12. Testing of the Pipe Line ( Para 6.4.4. Of CPHEEO) After laying and jointing, the pipe line must be pressure tested to ensure that pipes and joints are found enough to withstand the maximum pressure likely to be developed under working conditions.

The yield test pressure to be imposed should be not less than the maximum of the following. 1 ½ times the maximum sustained operating pressure. 1 ½ times the maximum pipeline static pressure. Sum of the maximum sustained operating pressure and the maximum surge pressure. Sum of the maximum pipeline static pressure and the maximum surge pressure subject to a maximum equal to the work test pressure for any pipe fitting incorporated. The field test pressure should wherever possible be not less than 2/3 work test pressure appropriate to the class of pipe except in the case of spun iron pipes and should be applied and maintained for atleast four hours. Where the field test pressure is less than 2/3 the work test pressure, the period of test should be increased to atleast 24 hours. The test pressure shall be gradually revised at the rate of 1 kg / cm2/minutes. In case of gravity pipe, maximum working pressure shall be 2/3 work test pressure. The hydrostatic test pressure at works and at field after installation and the working pressure for different classes of pipes are given in Annexure 5 5.13 Water Hammer (Surge Pressure ) (Para 6.17 CPHEEO) Occurrence If the velocity of water flowing in pipe is suddenly diminished, pressure would be develop in the pipe line due to frictional resistance and wave propagation. This pressure rise or water hammer is manifest as a series of shocks,


32


sounding like hammer blows, which may have sufficient magnitude to rupture the pipe or damage connected equipment. It may be caused by the nearly instantaneous or too rapid closing of a valve in the line or by an equivalent stoppage of flow which would take place with the sudden pressure. The pressure wave due to water hammer travels back upstream to the lintel end of the pipe, where it reverses and surges back and forth through the pipe , getting weaker on each successive reversal. The Velocity of the wave is that of an acoustic wave in an elastic medium, the elasticity of the medium in this case being a compromise between that of the liquid and the pipe. The excess pressure due to water hammer is additive to the normal – hydrostatic pressure in the pipe and depends on the elastic properties of the liquid and pipe and on the magnitude. Causes for Water hammer The Causes of water hammer are i) rapid closure of valves ii) Sudden shut off or unexpected failure of power supply to centrifugal pump. iii) Pulsation problems due to hydraulic rams and reciprocating pumps. Computations for Water Hammer Maximum water pressure (which occurs at the critical time of closure Tc or any time less than Tc ) is given by the expression. H max = C Vo G Where, H max = maximum pressure rise in the closed conduct above the normal pressure in m, C = Velocity of pressure wave travel in m/sec., G = acceleration due to gravity, 9.81m/Sec2 Vo = normal velocity in the pipeline, before sudden closure. in m/sec. C = 1425 1+kd ECt Where, k = bulk modulus of water (2.07 x 108 kg/m2) d = diameter of pipe in m Ct = wall thickness of pipe in m and E = modulus of elasticity of pipe material in kg/m2 Table below gives of E that may be adopted for different materials. Values of ‘E’ for Different Materials


33


34

Material Polyethylene – soft Polyethylene – hard PVC Concrete Asbestos Cement Reinforced Cement Concrete Prestressed Concrete Cast Iron Ductile Iron Wrought Iron Steel

2

E (kg/m ) 1.2 x 107 9 x 107 3 x 108 2.8 x 109 3 x 109 3.1 x 109 3.5 x 109 7.5 x 109 1.7 x 1010 1.08 x 1010 2.1 x 1010

If the actual time of closure T is greater than the critical time Tc, the actual water hammer is reduced approximately in proportion to Tc/T. Water hammer wave velocity may be as high as 1370 m/s for a rigid pipe or as low as 850 m/s for a steel pipe and for plastic pipes may be as low as 200m/s. Control Measures The internal design pressure for any section of a pipeline should not be less than the maximum operating pressure or the pipeline static pressure obtaining at the lowest portion of the pipeline considering any allowance required for surge pressure. The maximum surge pressure should be calculated and the following allowances made: (a) If the sum of the maximum operating pressure or the maximum pipeline static pressure which ever is higher and the calculated surge pressure does not exceed 1.1 times the internal design pressure, no allowance is required. (b) If the sum exceeds 1.1 times the internal design pressure, then protective devices should be installed and (c) In no case sum of the maximum operating pressure and the calculated surge pressure should exceed the field hydrastatic test pressure. (d) Effect of water hammer could be controlled by (i) installing special devices in the pipe lines (automatically controlled quick closing valves, bypasses and pressure relief valves. (ii) employing surge tank- simplest of form of surge tank is a stand pipe placed at the end of the line next to the point of velocity control. 5.14 Economic Size of pumping :



The economical size of pumping main is based on analysis of the following factors. i) Design period or period of loan repayment ii) Quantities to be conveyed during different phases. iii) Different pipe sizes against corresponding hydraulic slopes. iv) Different pipe materials and relative costs as laid v) Recurring cost on power. vi) Cost replacement of pump sets at an intermediate stage of design period. Duty capacity and installed costs of pump sets required against corresponding sizes of pipeline considered 5.15. Structural Loads on Rigid Pipes (Data matrix of TWAD Board Engineer)

Structural loads on Rigid Pipes are due to (i) fill material (ii) concentrated load and (iii) superimposed uniformly distributed load. Elaborate procedure has been developed by Matson for calculation of structural loads under conditions of pipes in trench, which will be worked out by the designers.

5.16 Strength of Pipes for various Bedding The manner in which the pipe is supported in trench and the nature of the backfill material affect the distribution of load and the internal stresses. Load factor of bedding and several type of bedding are indicated below It is customary to use two-thirds of the effective strength as design strength. Load Factor Type of bedding Ordinary bedding 1.5 First Class bedding 1.9 Concrete cradle bedding 2.25 to 3.4 Example: Let the load on a pipe (of certain diameter laid at required depth and trench width) due to fill material, concentrated moving load and superimposed uniformly distributed loads worked out in according with Matson’s formula be 10000 kg/metre length. Let the three edge bearing strength of pipe be 7500 kg/metre. With a factor of safety of 1.50, safe permissible load = 7500/1.5 = 5000 kg/metre load factor required = 10000/5000 =2.0 Hence concrete bedding should be selected. For the same pipe with a structural load of 5000 kg/metre, the load factor is 1.0 and ordinary bedding will be sufficient. Thus the choice of the bedding to be selected depends on the structural load on the pipes calculated in terms of the procedure outlined above.


35


Audit Approach PIPE •

•

• • • •

According to Para 6.3.1 of CPHEEO Manual, the cost of the pipe materials and its durability are the two major governing factors in the selection of pipe materials and the exercise prescribed in Ttable 6.7 of the ibid Manual the selection of pipe materials had to be carried out for selecting the economical and reliable pipe materials. The Manual also stipulates that selection of pipe for water supply works should be done economically as it involves major part of the project cost and designed on the basis of procedure stipulated in Appendix 6.5 –Design for Economic Size of pumping main of ibid Manual. But while selecting the pipe materials for pumping main and conveying main of water supply schemes, techno-economic selection of pipe materials stipulated in the CPHEEO Manual was not adopted involving extra cost. Cases will be available in designing pumping main adopting MS Pipe/CI Pipe/DI pipe instead of adopting PSC Pipes by erroneous adoption co-efficient of roughness (C value) for both metallic pipe lined with cement mortar or epoxy and prestressed concrete (PSC) pipe (ie. Value in both cases is 140). Para 6.9 of ibid Manual also stipulates that PSC pipe competes economically with metallic pipe for diameter 600 mm and above and ideally suited for water supply main where pressure is in the range of 6 kg/cm2 to 20 kg/cm2. Cases for adoption of DI pipe instead of CI pipe or MS pipe where the designed pressure of pumping main is much below the working pressure of CI or MS Pipe. According to TWAD Board Circular of February 1999, AC class 15 pipes upto to size of 300 mm dia could be used for pumping main. But cases of using PSC pipes/CI pipes/DI pipes could be identified and commented. While designing the pumping main it would be verified whether intermediary sump was at higher ridge point so as to reduce the pressure head was provided so that comparatively lesser class of pipe could be used for the pumping main Failure to provide intermediary sump and suitable device to control surge pressure resulting in frequent burst and leakage of pumping main leading for interruption in power supply. Such defective design and cost involved on rectification work had to be analysed and commented. NOTE: While objecting use of metallic pipe the Board used to contend that the metallic pipe was used to avoid illegal tapping of water from main, to complete the work within the time schedule and prevalency of rocky reaches. Those contentions were not tenable due to the fact that illegal tapping was not possible in PSC pipes also and the Board had allowed the same time for manufacturing, supplying, laying, jointing PSC Pipes and MS pipes. Further Board used PSC Pipes in pumping main even for hard rock reaches in other similar water supply


36


schemes by providing sand cushion or refilling the trenches as stipulated in the Standard IS Specification. • Even where higher class of pipes are used than the actual requirement to withstand the designed pressure on the pumping and distribution main, cases of leakages were noticed. Consequently, water could not be pumped to the designed level and supply effected. This was due to distortion at flexible joint. Thus due to defective joints, water could not be supplied. This could be commented. On non achievement of the objective due to defective execution of work • Cases where PSC/CI/DI Pipe is used instead of AC Pipes on the ground that the pipeline has to be laid on heavy traffic area. This contention is not correct. According to Para 6.13.4 of CPHEEO Manual one metre cover on pipeline is normal and generally sufficient to protect the pipeline from external damage. When heavy traffic is anticipated, depth of the cover had to be arrived at taking into consideration of the structural and other aspects as detailed in Para 6.13.2 of CPHEEO Manual. In as much as the pipe line are laid along the road side, the question of increase in stress on the pipe causing damage would not arise. Besides the Board has not worked out extra cover if any required for.

6. SELECTION OF PUMPS (Chapter 11 of CPHEEO Manual) 1. In a water supply system pumping machinery serves the following purposes: a) lifting water from the source (surface or ground ) to purification works or the service reservoir; b) boosting water from source to low service areas and to the upper floor of the storied buildings; and c) transporting water through treatment works, draining of settling tanks and of treatment units, withdrawing sludge, supplying water especially water pressure to operating equipment and pumping chemical solutions to treatment units. While deciding the type of pump for the specific requirements, it is necessary to analyze different type of pumps and their suitability to meet the requirements. 2.

The following pumps are generally used in water supply schemes. a. Centrifugal pumps b. Jet pumps c. Turbine pumps (oil lubricated or water lubricated vertical pump) d. Submersible pumps.


37


3. The selection of pump sets for different types of sources and conditions are as follows: 4.1. Borewells (Chapter 7 of Quality Control Manual) Sl.No. Site condition Preferable Pump Selection i. 100mm dia Bore well Jet pumps (Packer type ) Ii

150 mm dia Bore well(not straight)

Jet Pumps (Packer type )

Iii

150mm dia Bore well with yield less than 50 lpm

Jet Pumps (Packer type )

Iv

150 mm dia Bore well(with yield more than 50

Submersible pumpsets

lpm in urban area) V

150 mm dia Bore well in rural area a. yield between 50 & 100 lpm

Jet (with jet setting 20 m )

b. yield more than 100 lpm

Submersible pumpsets.

4.2.Wells and Other Sources Sl. No. I Ii Iii Iv

V Vi Vii Viii Ix X

Site Condition Inside the river one or more number of Infiltration wells. Inside the river one/more Infiltration wells with foot bridge arrangements. Collector well connected the bank with foot bridge Low lift raw water pumping, dry well built in the river / dam bank with suction head not to exceed 6m For the above site condition when suction head exceeds 6m Clear water ground level reservoir / sump

Preferable pump selection - Submersible pumpsets - Turbine pumps - Turbine pumps - Centrifugal pumps

- Turbine pumps

- Centrifugal/Turbine pumps Clear water/raw water booster pumping station. - Centrifugal pumps Line booster (small discharge < 1000 lpm) - Centrifugal pumps Line booster (large discharge ) Not desirable (sump has to be constructed ) Open well with suction head less than 6m in - Centrifugal pumps or


38


the lean period Xi

xii

xiii

xiv

open well submersible pumps - Jet / open well subersible pumpsets.

Open well with the water level goes down and the discharge is less than 50 lpm (both urban & Rural areas) For the above site condition when the dischartge is more than 50 lpm and the depth of well is more than 15m Jet pumps (HP not to a. Rural areas exceed 20) b. Urban areas For the above site condition with the depth of well is more than 15m and there is possibility of flooding.

Turbine pumps -

a. Urban areas

Submersible pumps

b. Rural areas

Jet Pumps (Not exceeding 20 HP) - Turbine / Centrifugal pumps.

Major schemes.

Note 1 For major urban schemes, only centrifugal or turbine pumpsets (1500 RPM or 1000 RPM) should be selected. In no case open well submersible pump sets should be selected of turbine pump owing to higher speed (3000 rpm) and lesser efficiency. 2. While selecting centrifugal pumps, the net positive suction head available for the particular condition should be indicated. 3. As for as the pumps are concerned, the following terms are very relevant in their usage. Duty of pump set The duty of pump set is the discharge in liters per minute against the total dynamic head (static head, friction losses and other losses ) to which each pump has to be operated. Shut off head Shut off head is the maximum head developed in the pump against zero discharge. Net positive suction head (NPSH ) a. NPSH required


39


This is the energy head destroyed in the suction passage of pumps during entry. b. NPSH available This is the head available after deducting from the atmospheric pressure the sum of static head, friction loss and vapour pressure at the attitude Always NPSH available should be more than NPSH required. 5. Life of Pump and Motor The life expectancy of electrical pumping machineries is 12 years as per TNPWD Code Appendix VII-A . The pump set and motors will start losing it efficiency year by year. However by doing upkeep preventive measures and doing necessary special repairs, the efficiency can be maintained with extension of life period upto 15 years. If they are replaced after 15 years, the advantages of latest technology available at that time of replacement can be made use of which will improve the efficiency of the system. (vide CE/SR/MDU Letter 15.12.2003 ) Appendix 6.5 of CPHEEO Manual stipulates the life of electric motor and pump are 15 years.

6. Criteria for Pump selection (Para 11.1.3 of CPHEEO) Prior to the selection of a pump for a pumping station, detailed consideration has to be sent to various aspects, viz., a. Nature of liquid, may be chemicals or if water, then whether raw or treated b. Type of duty required, i.e. Whether continuous, intermittent or cyclic. c. Present and projected demand and pattern of change in demand d. The details of head and flow rate required e. Type and duration of the availability of the power supply f. Selecting the operating speed of the pump and suitable drive/ driving gear. g. The efficiency of the pumps/s and consequent influence on power consumption and the running costs. h. Various options possible by permuting the parameters of the pumping system, including the capacity and number of pumps including standbys, combining them in series or in parallel. i. Options of different modes of installation, their influence on the costs of civil structural constructions, on the case of operation and maintenance and on the overall economics.


40


41

7. Types of Head affecting pumping system (Para 11.6 of CPHEEO Manual) A pump or a set of pumps has to satisfy the needs of the pumping system. Hence one had to first evaluate the head needed to be developed by the pump for delivering different value of flow rate. The following head affect the pumping system. a) Static Head This is the difference between the level of the liquid in the suction-sump and the level of the highest point on the delivery piping, obviously the static head is more at the low water level (LWL ) and less at the high-water level (HWL). b) Friction Head This is sum of the head-losses in the entire length of the piping, from the foot value to the final point of delivery piping, also the losses in all the valves i.e. the foot valve, non-return (reflux) valve and the isolating (generally, sluice or butterfly ) valves, and the loss in all pipe-fittings such as the bends, tees, elbows, reducers, etc. c) Velocity Head At the final point of delivery, the kinetic energy is lost to the atmosphere. To recover this loss, a bell-mouth is often provided at the final point of delivery. The kinetic energy the final point of delivery has also to be a part of the velocity head. 8. Parameters and Suitability of Pump (Para 11.1.7 of CPHEEO) Based on the considerations of parameters of head, discharge and speed in the selection of a pump as envisaged in Para 11.1.4 and consideration of the suction lift capacity laid in para 11.1.5 of CPHEEO a summary view is compiled of the application-parameters and suitability of pumps of various types and presented in Table below However, these are general guidelines . Specific designs may either not satisfy the limits or certain designs may exceed the limits. APPLICATIONS OF PUMPS Pump Type

Centrifugal, Horizontal end suction Centrifugal horizontal axial split casing Centrifugal, horizontal multistage Jet-centrifugal, combinations Centrifugal, vertical turbine

Suction capacity to lift Low Mediu High 3.5m m 6m 8.5m

Head range Mediu High m 10above 40m 40m Ok No

Discharge range Low Mediu High upto 30 m upto above L/s 500 L/s 500L/s Ok Ok No

Ok

Ok

Ok

Low upto 10m Ok

Ok

No

No

Ok

Ok

No

No

Ok

Ok

Ok

Ok

No

No

Ok

Ok

Ok

Ok

No

Ok

Ok

No

Ok

No

No

Ok

Ok

Ok

Ok

Ok

Ok

When limitations of suction lift are to be overcome. When suction lift is to be avoided



Centrifugal, vertical submersible Positive displacement pumps

When suction lift is to be avoided Normally self priming

Ok

Ok

Ok

Limited only by the pressure which casing can withstand

Ok

Ok

Ok Ok No Easy adoptation for dosing or metering

9. Drive Rating: (Para 11.1.9 of CPHEEO) After the operating point of a pump is decided as discussed in Clause 11.17 of CPHEEO, the efficiency of the pump can be estimated from figure 11.1 ibid. (TWAD issued orders to adopt 60% centrifugal pump and 70% for turbine and submersible pump). The rating of the drive should be such that it would not get overloaded when the pump would be delivering the high discharge as with HWL and the suction-sump. Also, the drive rating should be adequate to provide for negative tolerance on efficiency and the positive tolerance on discharge applicable for variation and actual pump performance from the rated performance. The power needed to be input to the pump is the power to be output by drive i.e., the pump shaft. Since most drives are coupled direct to the pump, the power at the pump shaft denotes brake power of the drive (or brake horse power). All drives are rated only as per their brake power capacity often quoted in Brake Kilowatt (BKW) or Brake Horse Power (BHP)

To provide margin over BKW or BHP at the operating point so that the overloading would not be happen as HWL, the following margins are recommended: BKW/BHP required at the operating point BHP

BKW

Upto 2 2 to 5 5 to 10 10 to 20 20 to 100 Above 100

Upto 1.5 1.5 to 3.7 3.7 to 7.5 7.5 to 15 15 to 75 Above 75

Multiplying factor for deciding motor HP 1.5 1.4 1.3 1.2 1.15 1.1

Note: 1 kilowatt = 1.34 Horse Power After multiplying, the next available range of motor HP has to be selected. BHP= Quantity to be lifted in lpm x total head in m 60x76.06xEfficiency in percentage Office of the Principal Accountant General (Civil Audit) Chennai

Ok 42


43

7. TREATMENT Treatment of water (Chapter 7 of CPHEEO Manual & Data Matrix) a. Aim : To improve the raw water quality to the drinking water standards and stop water borne transmission of epidemics . b. Methods of treatment : Depends on the nature of source and its water quality . Subsurface source Generally Chlorination will be sufficient except where iron is present . Surface source : Aeration ( if required) Pre chlorination ( optional ) Sedimentation – either plain or with coagulation and flocculation , and post chlorination . 1. Aeration Aim : i. to remove objectionable tastes and odours . ii. for expulsion of carbon dioxide, hydrogen sulphide . iii. to precipitate impurities iron and manganese present. iv. For increasing the dissolved oxygen content to water for imparting freshness. Types of aeration i. Spray – Type Office of the Principal Accountant General (Civil Audit) Chennai


ii. Multiple tray or water fall iii. Cascade type iv. Diffused air aerators v. Mechanical aerators 2 Pre – Chlorination Aim : i. to prevent biological growth in raw water ii. for reduction of colour . iii. for destruction of some taste & odour producing compounds . iv. for oxidation of iron, manganese and hydrogen sulphide . v. to aid coagulation. vi. for minimizing post-chlorination dosage . Dosage : 1 to 5 ppm depending on the degree of pollution . 3. Plain Sedimentation Aim : To separate suspended impurities from water by gravitation . Detention period :

Loading rate:

One to several days for sedimentation without subsequent filtration to 4 hours for sedimentation in conjunction with filters .( much longer settling time for basins preceding slow sand filters than for rapid sand filters ) . 2.4 to 24m3 / day / m2

4 Chemical dosing Aim : i. For coagulation, flocculation . ii. disinfection and softening . iii. algal and corrosion control . iv. for fluoridisation . Types

:(i) Dry feed . (ii) Solution feed .

Strength of solution :To be not more than 5% for manual feed and not more than 10% for mechanical feed. Alum is the most common coagulant used and economical. Lime is also added when PH and alkalinity are low Dosage for alum : 20-100 mg / 1 (1-5 grain / gallon ) Dosage for lime: About one third that of alum Density of lime = 670 kg / m3 Density of alum = 980 kg / m3 5 Flash mixing Aim :

To disperse the coagulant evenly in the water. Generally used when flow exceeds 300 Cu.m / hour. Head loss : 0.20 – 0.60 m of water


44


45

Ratio of tank dia. To height : 1.1 to 3.0 6. Coagulation and Flocculation Aim

:The addition of a coagulant like alum promotes the formation of micro floes which are the nuclei for the absorption of turbidity and colour causing particles. During flocculation, the micro floc particles formed during rapid mixing are brought together to aggregate into larger rapidly settle able floes by controlled agitation of water .

Detention Period

:15-30 minutes in flocculation zone .2-3 hours in settling or clarifier zone .

Dosage

:To be decided by Jar Test .

7. Sedimentation Aim: To remove readily settling sediments such as sand, silt, coagulated impurities such as colour and turbidity and precipated The range of surface loadings and detention periods for average design flow for different types of sedimentation tanks are as follows:

Tank type

Plain Sedimentation Horizontal flow, circular Vertical flow (upflow) clarifier

Surface loading m3/m2/d@

Detention period

Range

Typical value for design

Range

Typical value for design

Upto 6000

15-30

0.01-1.5

3-4

25-75

30-40

2-8

2-2.5

40-50

1-1.5

Particles normally removed Sand, silt & clay Alum and iron floge Flocculant

8. Filtration Aim i. to separate the suspended and colloidal impurities in the water . ii. to produce sparkling and aesthetically attractive water free from disease producing organism . Types : Slow sand filters, Rapid sandfilters



a. Slow Sand Filters :

Slow sand filters can provide a single step treated for polluted surface waters of low turbiding (< 20 Ntu)

Filtration rate

Normal operation: 0.1 m/hr Maximum overload rate:0.2 m /hr . : 0.6 to 1.3 m .

Allowable head loss Depth of filter sand

: initial 1.0 m Final (minimum) 0.4 m

Depth of gravel

: 30cm thick in 3 to 4 layers graded from 2 to 45 mm .

Depth of water over sand : 1.0 m. Free board

: 20 cm.

Depth of filter box

: 2.7 m

Effluent weir level above sand level

:

20-30 mm

Recommended Number of slow sand Filter : Area in m2 required. Minimum Area upto 20 m2 20-249 m2 250-649 m2 650-1200 m2 1201-2000 m2

Number

of

bed

2 2 3 4 5 6

b. Rapid Sand Filters :

The rapid sand filter comprises of a bed of sand serving as a single medium granular matrix supported on gravel overlaying an under drainage system.

Filtration rate

80-100 lpm/m2 or 4.8-6m/hr at normal rate :10 m/h at max..prudent arrangement would be at 4.8 m/hr

Head loss allowed :

1.8 to 2.0 m .

Depth of sand

:

Depth of gravel

: Gravel is placed between the sand and the under drainage system to prevent sand from entering the under drains and to aid distribution of waste water.

60-75 cm thick


46


Varying from 25 to 65mm at bottom and 2 to 5 mm at top with a depth 0.45m. Depth of water over sand :1.0-2.0 m. Size of Filter bed

:100 m2 (max ) for a single unit comprising Two halves 50 m2 each .

No. of Units

:4 ( min ) and 2 for small plants .

Overall depth

: minimum 2.6 m including a free board of 0.5 m

Ratio of length to width

: 1.25-1.33

9. Wash water Gutter

:Horizontal travel of dirty water over the surface of filter shall not be more than 0.6 to 1.0 m before reaching the gutter . Bottom of gutter should clear the top of Expanded sand by 50 mm or more . Upper edge of gutter should be placed as far above the surface of the undisturbed sand surface as the wash water rises in 1 minute .

10. Back wash .

Back wash should be arranged at such a pressure that the sand expands to about 130 to 150 of its undisturbed volume or 5 m head of water as measured in under drain. Normally the wash water is applied at 36 m (600 lpm/m2) for a period of 10 minutes

11.Pressure Filters Same principle as gravity type rapid sand filters; but water is passed through the filters under pressure. Disadvantages: pumping.

(i).

Tank axis may be vertical or horizontal. Pretreatment is not possible without secondary

(ii) (iii) (iv) (v)

Complicates effective feeding mixing and flocculation. Adequate contact time for chemicals not possible Observance of effectiveness of back was not possible Difficult to inspect clean and replace.

Advantages :

i. Secondary pumping is avoided for treated water. ii. Filter backwash is less complicated. iii. Suitable for small industries and swimming pools. 12.Post Chlorination


47


Aim :

For disinfection of potable water by the use of gaseous chlorine or chlorine compounds to destroy bacteria through the germicidal effects of effects of chlorine; may be done at head works / treatment works and supplemented by additional chlorination in loose pockets of distribution system.

Dosage:

When prechlorination is adopted relatively small doses will be required generally 1 to 2mg/l.

Contact period

: 30 minutes (minimum).

Residual Chlorine

: 0.2-0.8 ppm throughout the distribution system.

PH Value

:

Residual or free Available chlorine In ppm :

6-7

7-8

8-9

9-10

10-11

0.2

0.2

0.4

0.8

0.8

Quantity of chemical required in kg/day: Dosage in mg/1 X Quantity of water to be treated in mld. Specific gravity of Chlorine : 2.49 Density of Chlorine

:

3.214 g/litre.

8. TERMS AND CONDITIONS OF SUPPLY OF ELECTRICITY BY TAMIL NADU ELECTICITY BOARD Definitions a) Average Demand: - for the month means the ratio of the total kilowatt – hours in the month to the total hours in the month. b) Maximum Demand: – in a month means the highest value of the average kilovolt – amperes delivered at the point of supply of the consumer during any consecutive thirty minutes in the month. c) Permitted Demand: – means the demand permitted by the competent authority of the TNEB taking into account the constraints in the TNEB’s electricity grid. d) Sanctioned demand or Contracted demand - means the demand sanctioned by the competent authority of the TNEB and specified in the agreement. II. Load a) Connected Load: – means the aggregate of the manufacturers’ ratings of all equipments connected in the consumer’s installation and of all the portable equipments.


48


This is expressed in KW or HP. If rating is in Kilovolt (KVA), it is converted to KW by multiplying it by a power factor of 0.85. If the rating is in HP, it is converted to KW by multiplying it by 0.746. Note: 1) Standby motors’/pump sets’ capacity should also be taken into account for the purpose of connected load. 2) In case of water supply and drainage works, the standby motors’/pump sets’ capacity need not be taken into account for the purpose of connected load. The local bodies may be permitted to install standby motors in their L.T. services for water works and drainage pumping works. The local bodies should provide double throw change over switch or inter locking arrangement so that only one motor could be operated at a time. This should be ensured by the field officers.( Memo No.SE/RE&S(D)/DE/SS/A1/C.3315-1/85 Technical Branch dated 16.3.85 & SE/IEMC/EE.3/AEE.2/D.708/93 dt.21.9.93) b) Load Factor: – means the ratio of the Average Demand for the month in kilowatts to the Maximum Demand for the month in kilowatts.

III)

Power Factor

a) Power Factor means the ratio of the real power to the apparent power. Real power is expressed in KW and the apparent power expressed in KVA. Average Power Factor means the ratio of the kilowatt – hours to the kilo volt – ampere hours consumed during the month. IV.

Voltage

a) Low Voltage – means a voltage which does not exceed 250 volts under normal conditions subject to the percentage variation allowed under the Indian Electricity Rules 1956. b) Medium voltage – means a voltage which is higher than 250 volts but which does not exceed 650 volts under normal conditions. c) High voltage means a voltage which is higher than 650 volts but which does not exceed 33 KV. d) Extra High Voltage means a voltage which is higher than 33 KV under normal conditions. V. System of Supply a)

Low Tension Supply


49


Alternating current – 50 Hertz or cycles 1) Single – phase 240 volts between phase and neutral. 2) Three – phase 415 volts between phases. b) High Tension Supply Alternating current – 50 Hertz or cycles Three phase 11 KV or 22 KV between phases. VI Categories of Supply a) Single – phase, 2 – wire, 240 volt for :1) General supply not exceeding 4000 watts of – connected load, (including power loads), the capacity of any individual motor should not exceed 1.5 HP. b) Three – phase, 4 - wire, 445 volts between phases and 240 volts between phase and neutral for :1) General supply exceeding 4000 watts 2) Power load exceeding 1.5 HP upto 130 HP c) Three phase, 3 wire, 11 KV and above between phases for power installations exceeding 130 HP or 97 KW connected load.

N.B. : 1) A consumer shall avail only. Low Tension supply if the connected load is 75 HP (56 KW ) or below, 2) A consumer shall avail only. High Tension supply if the connected load exceeds 130 HP ( 97 KW) 3) When the connected load is between 75 HP and 130 HP, the consumer has the option to avail either Low Tension or High. Tension supply. In calculating the connected load for the purpose, the lighting load upto the permissible limit as laid in the Tariff Notifications will be excluded. General Normally for High Tension Service, H.T. metering will be provided on the H.T. side. In case where L.T. metering is provided for a H.T. service, the average losses in the transformer would be calculated as follows and this would be added to the energy consumption indicated by the meter, when the transformer capacity is above 50 KVA. 720 x 1.0 x KVA of the transformer / 100 units per month. Similarly the following percentage will be added to the recorded maximum demand on the L.T. side to arrive at the equipment H.T. demand. 1% of the transformer capacity for transformer above 50 KVA 1


50


For all L.T. service Electricity Board will provide L.T. metering on the consumer’s premises at a suitable place. Installation of Capacitors All L.T. consumers with a connected load of motors of 25 HP and above (Total of the ratings of the installed motors) all L.T. consumers using welding transformer (irrespective of their rating) shall install capacitors of rating not less than these specified below : (Clause 17.01) Rating of motor (HP)

Rating of capacity KVAR 3 5 7.5 10 15 20 25 30 40 60 75 100 125

1 2 3 4 6 8 9 10 15 20 24 30 39

If the L.T. consumers with a connected load of 3 HP & above do not install capacitors as required above, they will be charged a compensation amount at 10% of the current consumption charges for the two preceding assessment periods i.e., four months. If still capacitors are not provided within 2 nonths, services will be disconnected. In respect of H.T. service connections, the average power factor of the consumer’s installation shall not be less than 0.90 lag. Where the average P.F. of a H.T. service connection is less than the stipulated limit of 0.90 lag, compensation charge at the rate of 1% of the current consumption charges of that month for every 0.01 reduction in P.F. will be levied 9(Clause 17.04). In the event of the average P.F. of H.T. service connection going below 0.70 lag consecutively for three months, in addition to the levy of compensation charges at the above rate, the service connection will be disconnected after giving seven days’ notice. The service connection will be reconnected after the P.F. correction is carried out. An discount of 1% for maintaining power factor above 0.95 lag is allowed to the consumers by TNEB. Tariff & Billing


51


a) Water supply & drainage come under Tariffs II LT & HT b) The maximum demand charges for any month and at the point of supply shall be based on the KVA demand recorded in that month or 100% of the sanctioned demand (Now 90% of the sanctioned demand) whichever is higher, In addition, for exceeding the sanctioned maximum demand, the charges per KVA exceeded shall be at double normal rate (Clause 18.02)

Audit Approach The following points could inter alia be seen • Whether pumpset designed for 15 years. •

Whether higher capacities of pumps and motors were installed. This can be verified with the designed capacity with actual capacity used over a period of time.

•

Whether the recorded demand was more or less equal to the contract demand. If wide variation collect the recorded demand for the past period (say 1 to 3 years) and comment the excess with financial implication.

•

Verify the current consumption bill and ensure whether penalty paid for low power factor if so it may be commented with money value on the part of failure to improve the stipulated power factor with suitable capacitors.

9. DISTRIBUTION SYSTEM (Chapter 10 of CPHEEO Manual) The purpose of the distribution system is to convey wholesome water to the consumer at adequate residual pressure in sufficient quantity at convenient points. Water distribution usually accounts for 40 to 70% of the capital cost of the water supply project. As such proper design and layout of the system is of great importance. Metering is recommended for all cities. •

In the continuous system of supply, water is made to consumer all the twenty-four hours a day, whereas in the intermittent system, the consumer gets supply only for certain fixed hours(a few hours in the morning and a few hours in the evening). The intermittent supplies system suffers from several disadvantages and does not promote hygiene and hence wherever possible, intermittent supply should be discouraged and is uneconomical.

•

To ensures equalization of supply of water throughout the area Zoning in the distribution system is essential. The zoning depends upon (a) density of population (b) type of locality (c) topography and (d) facility of isolating for assessment of waste and leak detection. If there is an average elevation


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difference of 15 to 25m between zones, then each zone should be served by separate system. The neighboring zones may be interconnected to provide emergency supplies. The valves between the zones, however, should normally be kept closed and should not the partially opened. The layout should be such that the difference in pressure between different areas of the same zone or same system does not exceed 3 to 5m. •

water could be conveyed by gravity or by pumping, or gravity-cumpumping. Any of these three modes could be selected based mainly on the elevation of the source of supply with respect of the town

•

The location of service reservoirs is important for regulation of pressures in the distribution system as well as for coping up with fluctuating demands. In a distribution system fed by a single reservoir, the ideal location is a central place in the distribution system, which effects maximum economy on pipe sizes, Where the system is fed by direct pumping as well as through reservoirs, the location of the reservoirs may be at the tail end of the system. If topography permits, ground level reservoirs may be located taking full advantage of differences in elevation. Even when the system is fed by a central reservoir, it may be desirable to have tail end reservoirs for the more distant districts. These tail end reservoirs may be fed by direct supply during lean hours or booster facilities may be provided.

General Design guide lines for Distribution System (Para 10.3 OF CPHEEO) 1.Peak Factor: The per capita rate of water supply indicates only the average consumption of water per day per person over a period of one year. In the design of water supply distribution system, it is to be recognized that consumption varies with the season, month, day and hour. As far as the design of distribution system is concerned, it is the hourly variation in consumption that matters. The fluctuation in consumptions accounted for, by considering the peak rate of consumption ( which is equal to average rate multiplied by a peak factor) as rate of flow in the design of distribution system. The following peak factors are recommended for various population figures: For population less than 50,000 3.0 For a population range of 50,000 to 2,00,000 2.25 For population above 2,00,000 2.0 For Small Water Supply Schemes (Where supply is effected through standposts for only 6 hours) 3.0


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54

Note Fire demand can be assessed as per the norms given in section 2.2.8.3. Reference can also be made to IS 9668-1980 2. Residual Pressure: Distribution system should be designed for the following minimum residual pressures at ferule points: Single storey building = Two storey building = Three storey building =

7m 12m 17m

Distribution system should not ordinarily be designed for residual pressures exceeding 22 meters. Multistoried buildings needing higher pressure should be provided with boosters. 3.Minimum Pipe Sizes Minimum pipe sizes of 100mm for towns having population upto 50,000 and 150mm for those above 50,000 are recommended. For dead ends, less than 100mm can be considered. If it is a grid, less than 100mm can be used in situations where no further expansions contemplated.

4. Elevation of Reservoir The elevation of the service reservoir should be such as to maintain the minimum residual pressure in the distribution system consistent with its cost effectiveness. The hydraulic gradient in the pipe should normally be between 1 and 4 per thousand at peak flow. A suitable combination of pipe sizes and staging height has to be determined optimization of the system. The staging height of service reservoirs is normally kept as 15-20m. 5. Boosting: For distant localities, boosters may be provided instead of increasing the size of mains or height of the reservoir unduly for maintaining the required pressure. 6. Service Reservoirs ( Para 10.4 Of Cpheeo) •

The service reservoirs provide a suitable reserve of treated water with minimum interruptions of supply due to failure of mains, pumps etc. They also enable meeting the widely fluctuating demands when the supply is by intermittent pumping. They are also helpful in reducing the size of the mains which would otherwise be necessary to meet the



peak rates of demand. They can serve as an alternative to partial duplication of an existing main as the load on the main increased. •

The capacity of the service reservoir to be provided depends upon the better economic alternative amongst various options. A system supplied by pumps with 100% standby will have less storage capacity than that with less standby provision. Similarly a system divided into interconnected zones will require less storage, capacity for all the zones except for the zones at higher elevations.

•

The minimum service or balancing capacity depends on the hours and rate of pumping in a day, the probable variation of demand or consumption over a day. The estimation of demand in a day for a town is determined based on household survey.

•

Typical example on estimation of storage capacity is given in Appendix. 10.1 of CPHEEO.

•

Capacity of Storage reservoir i) Power is not available from 6 AM to 10 AM daily a) 16 hours pumping during 10 pm to 6 am and 10 am to 6 pm=39% daily demand b).8hours pumping during 4 am 6 am and 12 noon to 6 pm =46 % daily demand ii) Power is available throughout 24 hours a) 16 hours pumping during 4 am to 12 noon and 1pm to 9 pm= 15% daily demand b) 8 hours of pumping during 4 am to 8 pm and 2 pm to 6 pm = 33% daily demand

•

The capacity of service reservoir is fixed on the basis of hours of pumping and the peak rate of supply . The peak rate of supply is usually taken to be twice the average rate and the capacity of service reservoir is fixed at 8 hours or one third of days supply. (para 1.9.3. of notes on water supply schemes issued by Chief Engineer, PWD, Chennai in 1971.)

•

The ground level reservoir is generally preferred as storage reservoir which is circular or square or rectangular in shape. The economical water depth for reservoirs with flat bottom upto 1000m3 capacity is between 3 and 5.5m. The reservoirs should be covered to avoid contamination and prevent algal ladders, Suitable provisions should be made for manholes, mosquito-proof ventilation, access ladders, and


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overflow arrangements, water level indicator, and if found necessary, lighting arresters. 7.Balancing Reservoirs (Para 10.5 of CPHEEO) The tank is said to be “floating on the line” when connected by a single pipe to source and the distribution system. When the rate of supply exceeds the demand, water flows into the tank. When demand exceeds supply, water flows through the same pipe from the tank. The relation between rate of supply, rate of demand and tank capacity is based on a study the service required as in case of service reservoirs. When the balancing tank floating on the line is designed for the full service storage based on a study of the hydrograph of demand, its location and altitude is governed by the same conditions as are applicable to the service reservoir. Where the distribution system designed for direct pumping into the system it is advantageous to provide a balancing tank at the end of the system with a nominal capacity ( 1 or 2 hours) to provide pressure relief and improve the tail end distribution. The balancing reservoir has the advantage of minimum of pipe work and operational maintenance. 8.House Service Connections (Para 10.9 of CPHEEO) The supply from the street main to the individual buildings is made through a house service connection. This consists of two parts viz., the communication pipe which runs from the street main to the boundary of the premises and the service pipe which runs inside premises. The communication pipe is usually laid and maintained by the local authority at cost of the owner of the premises while the service pipe is usually laid by the consumer at his cost. The water supply in a building may be through one of the following or combinations both depending upon the intensity of pressure obtained in the street main and the hours supply. a. Direct supply system, and b. Down take supply by time with or without sump and pump Under Down take supply system, the supply may be delivered directly to the overhead storage tank or to the ground level storage tank. Separate tanks should be provided for flushing and other purposes. The capacity of the overhead and ground level storage tanks are decided by the local bye-laws. Generally a capacity of 50% of the daily requirement is provided in the level storage tank. For overhead tanks directly receiving water from public mains, the capacity should take care the total daily requirement, which could be reduced to 75% if supply is pumped from the ground level tank. The pumps shall be designed for peak rate at 3 times the average over 24 hours; or average rate of the 50% of the daily requirement over the actual hours of supply, whichever is cater. A standby pump set of equal capacity shall be provided.


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The down – take system of water supply in high rise buildings may be one or a combination of the following systems viz., overhead storage system, break pressure tank system and hydro-pneumatic system. 9. Clear Water sump (Datamatrix of TWAD Engineers) Capacity : If point of supply is near the filter plant, clear water reservoir may be a service reservoir of 8 hours storage capacity, if gravity is possible or of 30 minutes storage in case of continuous pumping. If pumping is intermittent, the capacity should be such that the filtrate could be drawn during non-pumping hours from a continuously worked filter. If point of supply is at a distance from the filter plant, capacity of clear water reservoir may be for 30 minutes storage either for gravity or for pumping if the transmission main carries average discharge of 24 hours basis. Otherwise the capacity should be increased to absorb the difference between the rate of inflow and rate of draw down in the clear water reservoir. At Head works / Treatment works site, a storage capacity varying from 2 to 12 hours is recommended depending on length and size of main and nature and frequency of power failures. Note : Distribution system should be designed economically since it involves more than half the cost of water works. Distribution system should not be designed for residual pressure more than 22m. Distribution by direct pumping is to be avoided.

Fire hydrants should be located at required points in the distribution system in consultation with the agency in charge of fire service. Special care should be taken to have an adequate horizontal and vertical separation between water mains and sewer lines. The lateral separation should be a minimum of 0.3m while the bottom of the water main should be atleast 0.5 m above the top of the sewer line. A water main should neither pass through nor come in contact with any part of a manhole.

Audit Approach •

Whether the distribution system is created to the designed level of water supply. Cases where pumping main, etc. were designed adopting 55 lpcd and distribution system created adopting 40 lpcd in CWSS may be identified analysed and the extra cost on creation infrastructures may be commended.


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•

Pumping system, pumping main created under separate scheme, but distribution system not created for long time or partially created resulting in under utilisation of assets.

•

Service reservoirs constructed adopting the norms for individual power pump schemes with higher capacity whereas as per norms prescribed by CPHEEO, the capacity is comparatively much lesser with reference to power supply and hours of pumping.

•

In case of the distribution system were designed adopting 55 lpcd, in Rural area, it should be ensured house service connection was envisaged and specific undertaking from local bodies obtained thereof.

Cases where

distribution system designed adopting 55 lpcd without providing HSC may be identified and commented.

10. RURAL WATER SUPPLY SCHEME Rural Water Supply Distribution System ( Para 10.8 of CPHEEO Manual) The water supply in rural areas is effected by one of the following two methods . (i) Shallow well or deep bore well fitted with hand pump (ii) Piped water supply with or without house connection through over head tank and standpipes located at strategic points within the community . • Piped water supply is distributed through the distribution system. The elevation of the over head tank is fixed by taking into consideration the residual pressure to be maintained at a farthest end of the distribution system and the length of the connecting pipe. When water is supplied only through stand posts, the tank is generally constructed with a staging height 6 m for communities with population upto 1500 and with a staging height of 7.50m for communities with population greater than 1500 . • When house connections are also provided, the height of staging may be suitably increased to ensure minimum prescribed terminal pressure. The distribution system for rural water supply scheme is designed for the peak demand which is assumed to be four times the average demand (duration of supply is


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6 hours) Techniques are available for the optimization of rural water supply distribution system. Background Drinking water supply is a state subject. In the Forth Five Year Plan, Government of India provided assistance to the States to carry out identification of problem villages and to accelerate the pace of coverage of problem villages. In 197273, GOI introduced the Accelerated Rural Water Supply Programme (ARWSP) to assist the State and Union Territories with 100% grants in aid to implement the schemes in such villages with the introduction of Minimum Needs Programme (MNP) during the Fifth Five Year Plan (from 1974-75), it was withdrawn. ARWSP was however, reintroduced in 1977-78 when the progress of supply of safe drinking water to the identified problem villages under MNP was not found to be satisfactory. The entire programme was given a mission approach when Technology Mission on Drinking Water and Related Water Management also called National Drinking Water Mission (NDWM) was introduced as one of five Social Mission in 1986. NDWM was renamed as Rajiv Gandhi National Drinking Water Mission (RGNDWM) in 1991. ARWSP was continued till 1998-99. But the objectives of the programme could not be attained as envisaged due to lack of sufficient funds and re emergence of not covered habitations etc. In March 1999, GOI approved Major Policy changes for implementation of Rural Water Supply Programme during the 9th Plan period and Sector Reforms Project (SRP) was launched on a pilot basis in the year 1999-2000 with the objective of institutionalizing community participation in capital cost sharing, operation and maintenance and water quality monitoring and surveillance in identified pilot district. 67 districts in 26 States were selected under SRP. The SRP was slightly improved and is being now launched as `Swajaldhara’ from 25th December 2002.

Programmes of RGNDWM (w.e.f. April 1, 1999) Funds are provided to the States by the Rajiv Gandhi National Drinking Water Mission under the following programme a) Accelerated Rural Water Supply Programme (ARWSP) To supplement the efforts of the States Governments in providing access to safe drinking water to all rural habitations of the country - implementing agencies for the programme may be decided by the State (viz Rural Development Department/Panchayat Raj Department, etc.) - implementation should be entrusted to one single department for better implementation, monitoring etc. - Panchayat Raj Institutions should also be involved in the implementation - Nodal department in the State Government will have the overall responsibility for planning, implementation, supervision and monitoring


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-

In case the implementation is entrusted to District Rural Development Agency (DRDA) there should be a close co-ordination between the State Nodal Department and the DRDA so as to ensure avoidance of duplication of efforts and dovetailing of the activities with the normal schemes under MNP and ARWSP. - To provide potable drinking water to the population at 40 litre per capita per day (lpcd) for humans to meet the following requirements Purpose Quantity (LPCD) Drinking 3 Cooking 5 Bathing 15 Washing utensil & house 7 Ablution 10 - Dual Water supply Policy may be adopted for rural habitation facing acute water quality problem. In these habitation even if safe water is provided upto 10 lpcd which would be sufficient for drinking and cooking purposes it may be considered as a habitation with a safe source of drinking water. For other activities like washing ablution etc., water available from unsafe source can be utilised without any problem. - Criteria for identification of problem habitation categorized as Not covered (NC), No Safe Source (NSS), Partially covered (PC) and Safe Source (SS) habitation NC: Public drinking water source does not exists within 1.6 km in plains or 100 metre elevation in hilly area. NSS: Habitations where quantum of available safe water is not enough to meet drinking and cooking need, Water source affected with salinity, iron, fluoride, etc. PC: Habitation having safe water but the level of supply ranged from 10 lpcd to 40 lpcd. • Priority for coverage 1. Coverage of NSS habitation. Among them priority be given to SC/ST habitation 2. Quality affected habitation 3. Upgradation of level of supply to 40 lpcd 4. Coverage of schools and Angan wadis. •

Funding—allocation of Central assistance under ARWSP is subjected to the matching provisional expenditure by the States under State Sector MNP. Releases under the ARWSP would not exceed the provision for Rural Water Supply made by the State Government under their MNP. The shortfall if any during previous year will be


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• •

deducted from the instalment of ARWSP funds for the current financial year. 25% of ARWSP fund should be earmarked for SC habitation and another 10% for ST habitation and 10% funds for O & M. Operation & Maintenance: upto 15% of the funds released every year under ARWSP to State may be utilised for operation & Maintenance of assets created subject to ceiling of matching grant provided by the State out of the MNP provision and the approved norms –funds earmarked for O&M of assets is not to be permitted for creation of capital assets.

b)Sector Reforms Project (SRP) • Institutionalising Community Participation in the rural water supply programme sharing capital cost, operation and maintenance , monitoring etc. • 20% of annual outlay of ARWSP Central outlay will be earmarked for SRP • Funds will be released directly to the District Water and Sanitation Mission which will have their own separate Bank account (SBI or its associates banks) to receive and disburse the fund for project implementation • At least 10% capital cost sharing and 100% sharing of O & M cost by the user (Community). This contribution can be in the form of cash or kind (labour, land or material) and cash compound should be atleast 50% of the contribution. Institutional Set up: (i)

Constitution of Water and Sanitation Mission (WSM) at the State level which consist of an Apex Committee headed by Chief Secretary and an Executive Committee headed by an officer of the department concerned with rural water supply, not below the rank of Joint Secretary-responsible for overall policy guidelines. (ii) Constitution of WSM at District level –District Water Sanitation Mission (DWSM): Constituted in the district and registered under Society Act—responsible for formulation, management and implementation (iii) Village Water and Sanitation Committee (VWSC): set up in each Gram Panchayat for implementation of Water supply scheme of their own choice with active participation of villagers—ensuring community participation and decision making in all scheme activities, arranging community contribution to capital cost both in cash and kind


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(land, labour or materials), planning of water and sanitation activities, procuring materials, selection of contractors, supervision of construction activities, signing of all completed works and community development activities, commissioning and eventual take over of completed water supply and sanitation works, managing and financing of O & M of the services on a sustainable basis. - Role of Women—to create awarness on handling and management of water supply - Training activities to equip the villagers for implementation and operation and maintenance and management of schemes of their choice—Departmental level, District level and NGOs – village level c. Sub mission Project: Submission Projects are undertaken by the States for providing safe drinking water to the rural habitations facing water quality problem like Fluorosis, Arsenic Brackishness excess Iron, etc and also for ensuring source sustainability through rain water harvesting , artificial recharge, etc. No separate fund released for implementation of sub mission Projects. Upto 20% of the ARWSP funds are to be earmarked and utilized for submission projects.

d. Support Services The following are support services S.No 1 2

3 4

Name of Service

Funding pattern

Water quality monitoring 100% funding as per the approved norms surveillance by GOI Rigs and Hydrofracturing units GOI and State Government share the cost an 50:50 basis on purchase of rigs on a very selective basis for remote and difficult access area. The expenditure will however be counted as matching provision for central assistance under ARWSP Human Resource Development 100% assistance from GOI Information Education & 100% assistance from Central funds Communication


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5 6 7 8 9

Monitoring and Investigation The expenditure will be borne by Centre Units and State on 50:50 basis Monitoring and Evaluation 100% financial assistance to State for carrying out evaluation Management Information System 100% Central assistance for all MIS activities Research and Development Mission would provide necessary assistance to the State Provision of Drinking water in The expenditure would be shared by State Rural School and Centre on 50:50 basis

e. Swajaldhara The Sector Reforms Project has been slightly improved and is launched as Swajaldhara on 25th December 2002. Swajaldhara will have two streams. First (Swajaldhara I) will be for a Gram Panchayat (GP) or group of GPs or intermediate Panchayat at Block level and the Second (Swajaldhara II) will have a district as the Project area and is being implemented by respective agencies. Specific proposals under Swajaldhara I will be sanctioned by the District Water and Sanitation Committee (DWSC). The District is the unit for implementing the reforms initiative under Swajaldhara II. In order to avail funds under Swajaldhara I & II, the State Govt. would enter into Memorandum of Understanding (MOU) with the Department of Drinking Water supply, Ministry of Rural Development, GOI.

•

The Minimum phase of community contribution for 40 litres per capita per day (lpcd) service level will be 10% of the estimated capital cost of the project and funding by Government of India would be restricted to 90% of the capital cost.

•

In case of all habitations fully covered in the States with 40 lpcd drinking water facilities the service level can be improved to 55 lpcd with 20% of the capital cost to be borne by community. In such States, in case of water supply schemes providing more than 55 lpcd, the additional cost would have to borne by the community/panchayat raj institution/State Govt. Funding by GOI would be restricted to 80% of the capital cost of 55 lpcd scheme only.


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•

The community contribution towards capital cost of the scheme could be in the form of Cash/kind/labour/labour or combination of those. However atleast 50% of the community contribution will have to be in cash.

In case

community contribution is more than 10% of the

scheme cost, the excess amount shall be taken into operation and maintenance fund. •

Operation, maintenance and management cost of the water supply scheme will have to be fully borne by the concerned community/user group/village water and sanitation committee (VWSC)/ panchayat Raj Institution

•

GOI may provide upto 10% of the Capital cost as a one time incentive to the O & M Fund created by the Panchayat Raj Institution/user group and the State Government should also make an equal matching contribution to the O & M Fund.

•

Institutional set up as in the same set up of Sector Project

•

Training programme etc as in the same manner of SRP

11. CERTAIN GUIDELINES OF TWAD BOARD /GOVERNMENT OF TAMIL NADU AND GOVERNMNET OF INIDA

1.Investigation and preparation of outline Proposal: In Major water supply schemes the preliminary investigation and detailed investigation should be conducted thoroughly without leaving any vital field details. The period of investigation should not exceed normally more than one year for water supply scheme and 1½ years for drainage scheme. As soon as the project estimates are administratively approved the competent authority should get the detailed estimates prepared and accord technical sanction to all the components within a period of 3 months. Before taking up any sub works of the project a PERT CHART should be prepared after thorough inspection of the site and discussion with the field officers in charge of the work – Activities on various sub heads of the sanctioned project should be initiated in accordance with the PERT CHART.


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Wide publicity and proper time should be given for all the major tenders before fixing up the contracts. The source creation shall take precedence over all other sub heads of the sanctioned project in the normal courses. There were instances, where Service Reservoir and distribution system are ready but the source is not created. Unless it is satisfied with the existence of a proper source with adequate quantity and quality to cater the needs there is no point in rushing up with the other components of the project. (G.O. Ms. No. 644 PWD dt: 31.3.80 read with B.P.Ms.No. 75 TWAD dated: 25.3.90) 11.2. Guidelines for adoption in preparation of Rural, Urban and Combined Water Supply scheme. (TWAD Board Lr. No. F. HOTC / AE-9/ P&D / 2001 dt: 7.6.2002 and Technical committee meeting held on 30.5.2002) Population Forecat: Revised provision please sees in chapter 3.4 Demand Projection: After arriving at required quantity of water based on the per capita supply level. Provision may be made for industrial and commercial requirement at a minimum of 10% of total requirements. In places where there are only industries, this can be increased to actual requirements based on committed requirements from the industries. Transmission losses at 10% of total requirement may be provided. Water available from existing other water sources may be deducted from the calculated requirements after ascertaining the sustainability of the quality and quantity of source from Hydrological reports. Yield from the existing hand pumps need not be taken into account for demand projection. While designing a new river water based project, all the wayside habitations irrespective of their status are to be included in the scope. The per capita supply to be adopted for the wayside habitations are as detailed below. For fully covered habitation -15 lpcd For partially covered habitation - The extent to which shortage in level of supply. For not covered habitations -as per norms. Source As far as possible source with sustainable quality and quantity for the design period of the project should be selected. The selected source shall not be susceptible to pollution and damage due to sand quarrying at any


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point of time. In case of insufficient supply of potable water dual water supply system may be adopted. While locating the infiltration wells, overlapping shall be avoided. Infiltration well shall be proposed only where saturated sand depth of not less than 5m is available. This should be ensured through probing. Confirmatory boring and study of lithology of soil strata. The selected site should be identified with reference to the standard bench mark on the bank. Recharge structures will be proposed wherever required for the sustainability of the drinking water source. Power pumps to the borewells to be fixed only when the yield from the borewell is more than 45 lpm and the water available is potable. Hours of Pumping: The norms for hours of pumping prescribed for Individual power pump schemes under RWS – 8 hours. Individual power pump schemes under urban water supply scheme – 16 hours. Combined Water Supply schemes –16 hours. If separate electrical feeder main is proposed then hours of pumping increased to 20 hours. Transmission main: Surge analysis ( Water Hammer ) should be made for all the cases of pumping mains. Size of main may be decided in the economic size calculation. The following pipe materials may be adopted for transmission main. Upto 160mm - PVC / UPVC Above 150 to 300mm - AC / UPVC Above 350 to 900mm - PSC / CI / DI Above 900mm - Steel / PSC / BWSP In Hilly terrain, G.I. pipe may be used. PVC pipe upto 315 mm OD is to be adopted as one of the alternative for water supply and sewerage project with techno economic consideration (TWAD Circular No.42/DO/P&D/2005 dt.04.10.2005. The TWAD Board in circular No. 29 / AE2/ P&D /2003 AE-5 / dt:30.06.2005, directed to adopt AC Cl.15 from pipe size of 200 mm above and AC class 10 for pipe size below 200 mm. AC pipes should be avoided within the Urban limits where heavy traffic is anticipated. While designing a combined water supply scheme uniform residual head at all delivery points (Service Reservoirs and sumps) should be maintained. Sufficient number of air valves, scour valves and line valves should be provided in the pipe line based on terrain, fixed by LS plan drawn at 30 metre intervals.


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Air valves may be introduced at every 1000m for pipe lines upto 600mm dia. For pipe line with size of main above 600mm dia air valves may be introduced at 500m intervals. To prevent pollution and damage to air valves by the public, air valve may be fixed above a 2.75m standard DF pipe and the DF pipes may be encased with concrete. Scour valves should be provided at valley points with facility for easy disposal of scoured water. For diameter more than 300mm the size of line valves may be fixed at 2/3rd of pipe diameter. For line valves of diameter 500mm and above by pass and gears arrangements and air valves on either side should be provided for easy operation. Provision of reflux valves may be restricted to the bearest minimum. By pass valves should be provided across the reflux valves. Air valves should be provided on either side of the reflux valve in the transmission main. Economical size of pumping main factor to be adopted ( on 15 years loan with rate of interest 12.5%) Capital cost factor - 0.153 Equivalent cost factor - 0.165 Annuity factor 0.153 Pumping Plants ( Sump & Pump sets) Detention time for sump with an inflow of less than 1 mld may be taken as 8 hours subject to a minimum of 30000 litres. For inflow more than 1 mld the sump capacity may be fixed at 4 hours storage subject to a maximum to 50 lakh litres. The sump need not be circular shape. Suit to site condition. Priority may be given for constructing the pump house over the sump. For centrifugal, turbine and submersible pump 50% stand by may be adopted except in the case of borewells. Efficiency of pumps for design purpose may be taken as 60% for centrifugal pump and 70% for turbine pump and submersible pumps. Inside the pumping, plant butterfly valves with valve actuators may be provided for valves of size 300mm and above. For pumping plants with 100 HP and above provisions may be made for SCADA with sensor for water level flow and pressure for collection of field operating information and control from the central location. Treatment Plant: The treatment plant should be designed based on raw water quality. Slow sand filter are easy to operate and maintain. These plants can be maintained even by local bodies with unskilled labours. The operating cost will be less when compared to rapid and sand filter. Even in places with limited land availability feasibility of providing multi- storeyed filters may be examined.


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In case of raw water with turbidity level less than 100, preference shall be given for provision of slow sand filters. For turbidity level between 60 and 100, a settling tank of 3 to 4 hours detention time may be provided. For water drawn from hill sources an aerator has to be provided. Service Reservoir (SR): The capacity of Service Reservoirs may be fixed on the following lines (i)For Rural habitations Population - ultimate Less than 150 - 5000 lit. GLSR with spot supply 151 to 500 - 10000 lit. OHT 6m staging. 501 to 1250 - 30000 lit. OHT 6m staging. 1251 to 2500 - 60000 lit. OHT 7.5m staging. 2501 to 5500 - 100000 lit. OHT 7.5m staging. Above 5000 as per requirement subject to a maximum of 1.50 lakh lit. with suitable staging height. (ii) For Urban Areas. The capacity of Service Reservoir may be fixed at 1/3rd of daily requirements. The staging height has to be fixed in such a way that a minimum residual head of 8m is available in the distribution system. Whenever the ground terrain of the town area varies more than 8m – zoning may be resorted to proposing separate Service Reservoirs for each zone or providing more than 1 outlet from the Service Reservoir.

Note:

1) The distribution system, service Reservoir and pumping main etc. in rural area were designed for 8 hours considering limited hours of power supply. 2) The capacity of over head Service Reservoir for comprehensive water supply scheme are to be designed not less 50% of the ultimate daily requirements of the individual habitation ( TWAD Circular Memo. No. 45997 / RWS/ 1113 / 82-3 / dated: 24.12.1982). Distribution System: The length of distribution system may fixed on the following norms for rural habitations. Population ( Ultimate) Upto 300 - 750 m 301 – 750 - 1500m


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751 – 1500 - 2250m 1501 – 3000 - 3000m above 3000 - 3750m The above norms are maximum limits. The distribution system length should be restricted to actual street length. As house service connections are proposed in the rural areas also , one public fountain for every 250 population ( present ) may be provided. In case of SC/ST areas the above norms may be relaxed. For urban areas, the distribution system should be designed for ultimate stage requirements to supply the requirements in 24 hours. The following peak factor may be adopted for arriving the design discharge. Population ( Ultimate) Upto 50000 - 3 50001 – 2 lakh - 2.5 Above 2 lakh -2 Rural areas ( Where water supply is effected through stand post : 3 only) Per capita cost: The following per capita norms may be followed for sanction of estimate by Chief Engineer/Superintending Engineer/Executive Engineer. In plains - Rs. 1750/In hilly areas - Rs. 2000/Cost per litre - Rs. 20/Implementation of the project Land required for different project components should be identified and availability ensured before finalising the project. . For implementation, the source creation work should be completed first before commencement of other components. Field particulars All field particulars have to be furnished for preparation of detailed estimate. The alignment plan should be drawn with reference to FM sketches or plain table survey or compass survey. 11.3. House service connection ( HSC) New water supply schemes may be taken up in rural habitations only after obtaining a firm commitment from the respective panchayat for giving House Service Connection to atleast 30% of the house holds in the habitation. ( MD/ TWAD Lr.No. 1202/ AE3/PM/R/2002/ dt: 21.6.2002) 11.4.Water utilization committee All water supply schemes and irrigation schemes involving drawal of water of less than 1 mgd (million gallon daily) shall be approved by the District


69


Collector concerned. 1 mgd and above shall be placed before the water utilization committee and the clearance obtained. ( G.O.Ms. No. 543 / PWD dt: 24.3.1980.) 11.5. Sustainability of water-designing infrastructure to wayside habitation of cwss. The existing level of supply should be assessed and its sustainability should be certified by the Deputy Hydrogeologist of the respective Circle. The per capita supply may be reduced from the 55 lpcd to the extent of sustainable present level of supply for which sustainability certificate has been issued by Deputy Hydrogeologist. If the present level of supply is not at all sustainable, a per capita supply of 55 lpcd may be adopted for designing the scheme. (TWAD Circular No.60/ DO / P&D / dated: 8.8.2002) 11.6. Guidelines for improvements and augmentation of existing water supply facilities. ( TWAD circular No. 38/ PO / P&D / 2001 / dt; 22.4.2002) Improvements and augmentation of the existing water supply facilities should be considered whenever there is failure of potable source, prevalence of inadequate supply and there is an actual need for augmentation / improvements. On the contrary in the several cases it has been noticed that habitations/town with sufficient level of potable water supply with level sources are being considered under river bed water supply project just to facilitate river water supply to the fully covered habitations / town. This practice not only results in unnecessary expenditure on the limited budgetary allocation, but also cuts the supply intended for other needy areas. Hence water supply scheme should be designed to benefit the actual needy areas and should be implemented mainly to benefit the needy population.

Similarly, the improvements / augmentation should be considered only after taking into consideration the following aspects. Present level of supply and quality of water should be ascertained with reference to the existing source. Actual requirements based on the population forecast should be properly derived. Existing condition of the infrastructure like head works, pumping main service reservoir, Pump rooms, Distribution system should be examined with reference to the suitability for the improvement proposed. It should be ascertained that the supply intended for the beneficiary in the original scheme has not been diverted to other areas necessitating the improvements / augmentation.


70


The improvements for augmentation should be designed to serve the beneficiary on a long term basis and should not be to get over the present crisis alone. 11.7. Guidelines for Accelearated Urban Water Supply Programme (AUWSP) (revised by GOI, Ministry of Urban Development Poverty Alleviation in letter No. Q 12045/23/92 CPHEEO dated 27.8.2001) General Guidelines: 1 The population of the towns should be less than 20000 as per 1991 census. For this purpose, the documents published by the Registrar General, Census Department shall be the basis. 2 95% dependability and reliability of the raw water source shall be established by the implementing agency, for which a certificate to the effect may be obtained from the competent authority of the nodal agencies responsible for the surface and ground water resources and included in the DPR, so as to ensure availability of water as per the demand through out the design period of the scheme. The location of the proposed source should be finalized in consultation with the nodal agency and the concerned urban local body. 3 A commitment from the implementing agency for maintenance of separate account of the scheme may be included in the DPR. 4 The following stipulation are fulfilled in the detailed project report (DPR) and it should contain a resolution of municipality/urban local body/O&M agency • Consent of the urban local body for execution of the scheme through the State Implementing Agency • Commitment for contribution of 5 % of the project cost from the urban local body. • Acceptance of the scheme for taking over after completion and commissioning for operation and maintenance and implementation of the tariff, as proposed in the DPR so as to ensure sustainable O & M mechanism and sustainable tariff system, duly approved by the State Government. • Commitment for creation of adequate infrastructure with urban local body for trouble free O & M of the scheme, regular exercise for leak detection survey & repairs to control underground leakage with the help of the State Implementing Agency and adequate training to the O & M staff of urban local body by the executing agency during the implementing of the scheme. • Certificate regarding the availability of land required for construction of the scheme may be appended with the DPR. In case Government land is made available, a certificate from the competent authority is desirable. In case the land is to be acquired from a private party, an advance action should be initiated and the Action Taken Report should be appended with the DPR.


71


5.

The State Land Selection Committee (SLSC) may monitor/review from time to time the physical and financial progress of the schemes already approved by GOI before selecting new towns so as to assess/identify the shortcomings and suggest remedial measures to complete the schemes as per the schedule. 6. While selecting project towns by SLSC, priority must be accorded to towns with special problems like: a) Very low per capita supply b) Very distant or deep water source c) Drought-prone area d) Excess salinity, fluoride, iron content in the water source e) High incidence of water born diseases 7. Priority is to be given by the SLSC to rehabilitation and augmentation schemes rather than new schemes 8. No change/alteration in the priority list of towns selected by the SLSC will be permitted. 9. The DPR should contain: • A commitment to launch the scheme immediately after receiving technical approval of Government of India/Administrative Approval of the scheme by the State Government with necessary budgetary provision • Commitment from the State Power Department / Statement Electricity Board to ensure interrupted power supply to the scheme • A certificate/commitment to the effect that, the works for different components of the scheme included in the DPR have not commenced and no expenditure has been booked. • Whether any Government of India fund from any other Central Development Programme was obtained during the last five years/proposed to be obtained or not. If yes, details may be indicated in the DPR. • Details of the total annual and expenditure of the agency responsible for O&M for the last 5 years in order to assess their financial soundness to take over the scheme for O&M after its commissioning. • Permission/action initiated to obtain permission from various departments, e.g. Revenue, Water Resources, Forest, Rural, Highways, Railways, etc. wherever necessary, for implementation of the scheme. Technical Guidelines: 2. While preparing the DPRs, technical guidelines stipulated in the revised Manual on Water Supply & Treatment published in May 1999 by this Ministry may be considered in addition to AUWSP guidelines. 3. The design period for 20 to 25 years as per guidelines of AUWSP may be considered for the scheme. In addition, a gestation period of 2 to 3 years may be adopted to decide upon the base year, intermediate stage and ultimate stage of the scheme.


72


4. The demand of per capita water supply may be considered as below: - 70 lpcd for the population to be provided with house service connection - 40 lpcd for the population to be provided with Public Stand Post (upto a maximum of 30% of the population) - In addition, losses/unaccounted for water (UFW) to a maximum limit of 15% of the total demand may be considered. - The aforementioned per capita supply levels include requirement of water for commercial, institutional and minor industries. However, in case of bulk demand for industries, commercial areas and institutions, the same should be assessed separately with proper justification. The proportionate cost for such bulk demand must be borne by the respective organisation/establishment. A commitment to the effect may be obtained from such organisation/establishment, duly recommended by the urban local body and incorporated in the DPR. Pattern of Finance AUWSP will be funded on grant basis by the Central Government 50% and the State Government 50% including 5% beneficiaries/town contribution. In case of Union Territories 100% financing is available from Central Share. Release of Fund: • 25% of the Central Share will be released to the State Government or the designated agency on selection of the scheme • Second installment of the Central Share (i.e. 50% of the eligible Central Share) will be released on (i) release of the first installment of the State Share, (ii) completion of ground work for execution of the scheme including award of contracts, (iii) utilisation of atleast 50% of the amount released for the scheme (ie. including state share), (iv) submission of detailed project report and its approval. • Third and final installment amounting to 25% of Central Share will be released on (i) release of second installment of State Share (ii) utilisation of 80% of the total funds released for the scheme. 11.8. Exemption from Central Excise & Customs Duty In notification 91/2002 cus, 92/2002 cus, 93/2002/cus and 47/2002 CE dated 6th September 2002 Government of India have been issued orders to extend exemption of Customs and Central Excise duties in respect of water treatment project and pipes needed for delivery of water from its source to the plant and from there to the storage facilities for supply of drinking water for human and animal consumption. Pre-requisite site for claiming exemption : (i) Should have water treatment. Office of the Principal Accountant General (Civil Audit) Chennai

73


(ii)

Specific certificate by District Collector / District Magistrate in which the treatment plant located in produced to the Excise Department having jurisdiction over the manufacture products used for the water supply scheme. Explanation: for the purposes of this exemption, water treatment plants includes a plant for desalination, demineralization or purification of water or for carrying out any similar process or processes intended to make the water fit for human or animal consumption but does not include a plant or plant supplying water for industrial purpose.

12. MISCELLANEOUS 12.1. Preventive maintenance (Para 10.10 of CPHEEO Manual): Preventive maintenance of water distribution system pipelines assures the twin objectives of preserving the hygienic quality of water in the distribution mains and providing condition for adequate flow through the pipe lines. Some of the main functions in the management of preventive aspects in the maintenance of mains are assessment, detection and prevention of wastages of water from pipe lines, maintaining the capacity of pipe line and cleaning of pipe line . a) Wastage: Wastage is due to leakage in water mains due to corrosion, fracture, faulty joints, ferrule connection, service pipes and fittings inside the consumer’s


74


premises due to joints corrosion faulty washers on glands in valves and taps, abandoned service pipes and ferrule connections in mains; and failure to turn off taps in premises willfully or inadvertently. b) Leakage Detection : Leakage detection survey is confined only to the areas with heavy leakages as arrived at by the waste assessment survey. The survey consists of : i) Finding leaks in the pipes by visual determination of surface; and ii) Traversing the sub – zone in the night by sounding rod, or electronic leak locator for pinpointing of leaks in pipes . C. Cleaning of pipes The necessity for systematic and periodic cleaning of pipelines is borne out by the fact that the carrying capacity of the pipes gets reduced due to growth of slimes, incrustation deposits. Flushing and swabbing of pipes, which are simple and inexpensive can go a long way in maintaining the capacity. The old cast iron and steel pipes which are cleaned can be protected from further incrustations or corrosion by cement lining. Insertion of a plastic pipes has also practiced with success . d. Protection against pollution near sewers and drains A water main should be laid such that there is at least 3 m separation, horizontally from existing or proposed drain or sewer line. If local conditions prevent this lateral separation of water main may be laid closer to a storm or sanitary sewer, provided that the main is laid by separate trench or on an undisturbed earth shelf located on one side of the sewer at such elevation that the bottom of the water main is at least 0.5m above the top of the sewer.

In situations where water mains have to cross house sewer; storm drain, or sanitary sewer then it should be laid at such an elevation that the bottom of the water main is 0.50 m above the top of the drain or sewer with the joints as remote from the sewer as possible. This vertical separation should be maintained for a distance of 3 m on both sides measured normal to the sewer or drain it crosses . Where conditions prevent the minimum vertical separation set forth above, or when it is necessary for the water main to pass under a sewer or drain, the water main should be laid with flanged cast iron pipe, with rubber gasket joints for a length on either side of the crossing to satisfy the lateral separation of 3 m. A vertical separation of 0.50m between the bottom of the water main and the top of the sewer should be maintained with adequate support for the larger sized sewer lines, to prevent them from settling on or breaking the water main. In making such crossings, it is preferable to have the sewer also of casting flanged pipe with


75


rubber gasket joints and both the water and sewer mains pressure tested to assure water tightness before back fillings. Where a water main has already been laid and where a new sewer is to be laid, the above aspects may also be taken into consideration and the water main may be realigned, when it is not possible to lay the sewer consistent with the above recommendations. Since water expands nearly about 10% in volume with an irresistible pressure, freezing solid conditions should not be allowed in any pipe system to avoid interruption of service and prevent damage to the pipes . 11.2. Method of raising revenue (Para 17.4 of CPHEEO Manual) The sources of revenue are the funds received by general taxation such as water tax or a portion of the general property tax which is realized by assessment on all taxable property and water rates paid by those who use the water, more or less in proportion to the amount consumed . Water tax Since the provision of a water supply to a town enhances the value of the property, a water tax is justifiable on the annual rental value of the property. This may be a separate tax or included in the general property tax but it is desirable that the revenue under this head is earmarked for water supply purpose . Water rates The revenue from the sale of water or water rates recoverable from parties actually consuming the water such as for domestic purposes or for commercial and industrial purposes is utilized to meet the annual recurring cost of operation and maintenance and to provide for a reserve for meeting the capital expenses for future improvement to the system . Any major augmentation of the system should, however, be dealt with by the new scheme for which the capital is to be raised in the usual manner .

The most equitable method will be based on metering of all the supplies. The quantity actually accounted for by the meters is invariably less than the quantity produced since there is a considerable wastage as unaccounted water, which should also be considered in fixing the water rates. The water rates are to be carefully fixed taking into account the following: i) The rate should be high enough to fetch the necessary revenue and not excessive as to discourage consumers from making needed use of the water for domestic needs and for personnel hygiene in particular . ii) The rate should be such as to make the amenity more or less self paying and worked on a no – profit – no – loss basis . iii) The rate should be such as to provide for generating source for expanding the system to take care or increasing requirements .


76


It is desirable that water supplies at least to all cities having a population of one lakh and more are metered. 11.3. Water supply management (Para 17.5 of CPHEEO Manual) Efficient and effective management of water supply systems is most essential for their proper functioning. A water supply organization should be treated as a business enterprise involving managerial skills and engineering knowledge to make it successful in service, in safety and in financial considerations. The quality of water supplied should be the prime consideration for any water supply organization as the safety and health of the people depend upon it. The technical and engineering problems involved in the running of a water supply organization call for a qualified Public Health Engineer as the head of the management . Scope A good management of a water supply system includes a number of functions such as (i) Provision and maintenance of adequate facilities : (ii) Good and smooth operation : (iii) Efficient and economical maintenance : (iv) Establishment of sound fiscal methods : (v) Development of equitable water tax and water rates : (vi) Efficient control of equipment and supplies : (vii) Keeping the wastage of water to a minimum : (viii) Good public relations and satisfactory service to consumers: and (ix) Development of technical and financial plans for future expansion .

11.4. Project appraisal of water supply projects (Para 17.6 of CPHEEO Manual) Project appraisal is the analysis of costs and benefits of a proposed project with an aim of obtaining a rational allocation of scarce resources among alternative investment opportunities in view of achieving certain specified goals in the National Development Programme. A project carefully analysed and revised in the light of this analysis has a much improved chance of being implemented on time and of yielding the desired benefits. In projects analysis, there is a critically important distinction to be kept in mind between two complementary points of view viz . (i) Economic analysis ; and (ii) Financial analysis .


77


Economic analysis is concerned with the total return or productivity or profitability to the whole economy of all the resources committed to the project regardless of who in the society contributes them and regardless of who in the society receives the benefits. The social cost benefit or economic analysis aims at evaluating the profitability according to the impact on the society as a whole, while the financial cost benefit analysis tries to assess the profitability to the operating entity . On the other hand, financial analysis is concerned with the individual financial entities which participate in a project, viz. entrepreneurs, businessmen, farmers, public agencies, etc., which is interested in the return to the equity capital one contributes. Project appraisal is very important for the developing countries which are in the process of achieving stupendous task of recycling of financial and other resources for productive purposes and welfare of the poor people . The analytical techniques employed for Economic and Financial appraisal comprise deriving valves for the net present worth ( NPW ), internal rate of return ( IRR ) and the benefit cost ratio ( B/C). These are defined as follows. Net present worth ( or Net present value ) : ( NPW / NPV ) This is defined as the present worth of the net benefits of a project discounted at the opportunity cost of capital . i.e. Net present worth = ( Present worth of benefits – Present worth of costs ) Internal rate of return : IRR This is defined as that discounted rate at which the present worth of benefits, is equal to the present worth of costs. This measure represents the return over the life of the project to the resources engaged in the project . To determine IRR the NPW is first calculated at two different discounting rates ( r1 and r2 ) being the higher and lower discounting rates ) TRR = r2 + (r1-r2) NPW2 NPW2 – NPW1 Benefit Cost Ratio : ( B.C. Ratio ) This is defined as the present worth of benefit divided by the present worth of cost 11.5. Project cycle (Para 17.6.2 of CPHEEO Manual) Any project has to under go the following project cycle : (i) Identification The first phase of the cycle is concerned with identifying projects that have a high priority with reference to the set objectives and needs of the country . (ii) Preparation The next stage is project preparation which should cover the full range of technical, institutional, economic and financial conditions necessary to achieve the project objectives. A critical element of preparation is identifying and comparing technical and institutional alternatives for achieving the project objectives. This has to be


78


followed by a more detailed investigation of the most promising alternative and the most satisfactory solution is finally worked out . (iii) Appraisal As the project takes shape and studies are nearing completion, the project is scheduled for appraisal. It is a critical stage of the project cycle because it is the culmination of the preparatory work, provides a comprehensive review of all aspects of the project, and lays the foundation for implementing the project and evaluating it when completed . Appraisal consists of four parts viz ., (a) Technical (b) Institutional (c) Economic (d) Financial Technical appraisal is necessary to ensure that the project is designed in a sound manner as least – cost solution following all the accepted engineering norms. The various technical alternatives considered and the solution proposed are part of technical appraisal. This also includes appropriateness of technical standards adopted, reality of the implementation schedule, likely hood of achieving the expected results, review of capital cost and operating cost estimates and engineering and other data, proposed procurement arrangements etc . Second part is the appraisal of the institutional aspects of the project which also includes recognition of the need for a continuous re – examination of the institutional arrangements with an open mind to accept new ideas and adopt a long term approach that may extend over several projects . Third is the economic appraisal which aims at assessing the contribution of the project to the development objective of the country and this remains the basic criterion for project selection and appraisal . The fourth and the last one is financial appraisal which has several purposes viz, to find out whether the project is financially viable to meet all its financial obligations including debt servicing, to generate adequate working capital, to generate funds from internal sources, to earn a reasonable return on its assets in operation and make a satisfactory contribution to its future capital requirements. The financial review often highlights the need to adjust the level and structure of prices charged to the project . It is the objective of economic analysis to identify whether projects have Net Present Worth which will be a positive quantity and fulfill the prescribed Benefit – Cost ratio. Negotiations with the Financing institutions Negotiations is the stage at which the lending institution and the borrower endeavour to agree on the measures necessary to assure the success of the project. These agreements are then converted into legal obligations, set out in the loan documents . Implementation and Supervision


79


Implementation by the borrower and supervision by the lender form the next stage. Progress reports followed by field visits constitute part of supervision . Evaluation and Feed Back This is the last stage of the project cycle and provides lesson of experience which are built into subsequent project identification, preparation, and appraisal work. 11.6. Financial appraisal (Para 17.6.3 of CPHEEO Manual) Financial Appraisal of Water Supply Scheme is necessary : (i) To ensure that the project is financially viable, whether the project will meet all its financial obligations including debt servicing, whether there will be adequate working capital ; whether the project can generate funds from its internal resources to earn a reasonable return on its assets in operation and make satisfactory contribution to its future capital requirements . (ii) To adjust the level and structure of prices charged, when need arises ; and (iii) To ensure recovery of investment and operating costs from the project beneficiaries . The finances of a project are closely reviewed through projections of the balance sheet, income / expenditure statement, and cash flow. Where financial accounts are inadequate a new accounting system has to be established with technical assistance financed out of the loan . The economic appraisal of a project aims at assessing the contribution of the project to the development objective of the country whereas the financial appraisal aims at ensuring the financial viability of the project . Two important factors which lead to the distinction between financial analysis and economic analysis are : (a) Exclusion inclusion of some costs and benefits in the appraisal of a project and (b) Valuation of costs and benefits and market prices or some other prices .

In the Project Appraisal Technique , the costs and benefits of the project in financial / economic terms are evaluated. It is easy to identify costs and benefits in financial terms where as it is difficult to identify in economic terms. The project incurs expenses on capital investment, such as machinery and equipment, operation and maintenance cost, purchase of raw materials, payment of wages and import of goods and services etc. In addition the projects has to pay taxes, import duties, fees, repay the loan with interest and allow for the depreciation of fixed assets . The project gets its return from the sale of goods and services and also receives subsidy, if allowed by the Government, which reduces the costs or add to the income .


80


Two types of costs and benefits are encountered in the appraisal of a project – one involves the use of resources, and the other which does not involve use of resources, but it is a transfer of resources from the project to the Government or any other institution / individual ( taxes, fees, duties, loan repayment and interest ) or vice versa ( subsidies ). Audit approach on Implementation Failure to conduct proper investigation and identifying a reliable, sustainable dependable source to meet the ultimate requirements necessitating the formulation of another scheme even during the execution of the former scheme or before completion of the designed service life. The costs involved in execution of the latter scheme especially headworks, pumping main, Booster Station, sump etc. are avoidable. According to the orders of the Board in March 1990, various components of water supply schemes shall be executed only after ensuring adequate quality and quantity of water sources. However without ensuring the availability of water for the ultimate requirements, pumping main, distribution system were constructed for ultimate requirement resulting in unfruitful extra expenditure. A few type of cases are listed below: (i) Failure to create reliable and dependable source before creation of infrastructure rendered the entire infrastructures unutilized. (ii) Creation of infrastructure for larger discharge than the yield available. (iii) Due to public objection required designed level of water could not be extracted, but pumping main constructed for the original design involving higher size of pumping main. Failure to revise the design on the basis of actual yield resulted in extra cost on creation of higher size of pumping main. Avoidable delay in execution of the work resulted in non-achievement of objective. This was due to : a) delay in obtaining permission from Highways department for laying pumping main b) delay in execution of work • The cause etc. thereof has to be analysed critically and commented. • Water supply scheme designed with drawal of source from another water supply scheme. Though all infrastructures were created for supply of water, the scheme held up due to non completion of the scheme from which source was proposed to be drawn. • Under utilisation of the completed water supply schemes The work of construction of head work, treatment plant, pumping main, clear water reservoir, transmission main, feeder main with all facilities to supply water to the intended habitations completed much earlier. But the infrastructures to supply water to the group of habitation was either not completed or work not taken up. Hence the assets created to supply water to designed level could not be Office of the Principal Accountant General (Civil Audit) Chennai

81


put into optimum use. Head works, pumping main completed which provided for bulk provision of water to supply various other habitations. But evenafter commencement of the water supply scheme, the work of distribution system was not sanctioned and taken up for execution, to those habitations for which bulk provision was made for.


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83

ANNEXURE 1

Estimation of future population Problem The population of a town as per the Census records are given below for the years 1921 to 1981. Assuming that the scheme of water supply will commence to function from 1986, it is required to estimate the population 30 years hence, i.e. in 2016 and also the intermediate population 15 years after 1986, i.e.2001. Year 1921 1931 1941 1951 1961 1971 1981

Population 40,185 44,522 60,395 75,614 98,886 1,24,230 1,58,800 Total Average

Increment 4,337 15,873 15,219 23,272 25,344 34,570 1,18,615 19,769

Solution Arithmetical Progression Method Increase in population from 1921 to 1981 i.e. in 6 decades = 1,58,800 -40,185 1,18,615 or increase per decade =1/6 x 118,615 = 19769 Population in 2001 =Population in 1981 + increase for 2 decades = 158,800+2 x 19769 =158,800 + 39538 =198,338 Population in 2016 =Population in 1981 + Increase for 3.5 decades = 158,800 + 3.5 x 19,769 = 227,992 2. Geometrical Progression Method Rate of Growth (r) = 4337/40185= 0.108 Per decade between 1931 and 1921 1941 and 1931 = 15873/44522= 0.356 1951 and 1941 = 15219/60395= 0.252 1961 and 1951 = 23272/75614= 0.308 1971 and 1961 = 25344/98886= 0.256 1981 and 1971 = 34570/124230=0.278 _____________________________________ 6 | 0.108 X 0.356 X0.252 X 0.308 X 0.256X0.278



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Geometric mean, rg = Assuming that the future growth follows the geometric mean for the period 1921 to 1981 rg = 0.2442 Population in 2001 = Population in 1981 x ( 1 x rg)2 = 245,800 = 158800 x (1.2442)2 Population in 2016 = Population in 1981 x (1+ rg)3.5= 1.58,800 x (1.2442)3.5=3,05,700 Methods of Varying Increment or Incremental Increase Methods In this method a progressively decreasing or increasing rather than a constant rate is adopted. This is a modification over the Arithmetical Progression method. Year

Population 1921 1931 1941 1951 1961 1971 1981

Increase (x)

40,185 44,522 60,395 75,614 98,886 1,24,230 1,58,800 Total

4,337 15,873 15,219 23,272 25,344 34,570 1,18,615

Incremental increase (Y

11536 654 8053 2072 9226 30233

Average = 1/6 x 118615= 1/5 x 30,233 = 19769

=

6047

Pn =P1+ nX + n(n+1)Y 2 P2001 = P1981 + 2x 19769 + 2x3x6047 2 = 158800 + 39538 + 18141 = 216479 P 2016 = P1981 + 3.5.x 19769 + (3.5 x 4.5 x 6047) /2 = 158800 + 699192 + 24,188 = 252180



85 ANNEXURE II Recommended guidelines for physical and chemical parameters. Sl. Characteristics * Acceptable ** Cause No. Rejection 1 Turbidity (NTU) 1 10 2

Colour(Units on Platinum Cobalt scale)

5

25

3

Taste and Odour

Unobjectionable

Objectionable

4

PH

7.0 to 8.5

<6.5 or >9.2

5

Total dissolved solids)mg/1)

500

2000

6

Total hardness (as CaCO3 ) (mg/1)

200

600

7

Chlorides (as C1) (mg/1)

200

1000

8

Sulphaters (as SO4) (mg/1)

200

400

9

Fluorides(as F)(mg/1)

1.0

1.5

10

Nitrates(as NO3)(mg/1)

45

45

11

Calcium(as Ca) (mg/1)

75

200

12

Magnesium(as Mg) (mg/1)

530

150

for

If there are 20 mg/1 of sulphates, Mg content can be increased to a maximum of 12 mg/1 with the reduction of sulphates at the rate of 1q unit per every 2.5 units of sulphates. 13 Iron (as Fe) (mg/1) 0.1 1.0 14

Managanese (as Mn) (mg/1)

0.05

0.5

15

Copper (as Cu) (mg/)

0.05

1.5

16

Aluminimum (as A1) (mg/1)

0.03

0.2

17

Alkalinity (mg/1)

200

600

18

Residual Chlorine (mg/1)

0.2

>1.0

19

Zinc (as Zn) (mg/1)

5.0

15.0

20

Phenolic compounds (as Phenol)(mg/1)

0.001

0.002

21

Anionic detergents (mg/1)(as MBAS)

0.2

1.0

22

Mineral Oil (mg/1)

0.01

0.03

Toxic materials 23

Arsenic (as As) (mg/1)

0.01

0.01

24

Cadmium (as Cad) (mg/1)

0.01

0.01



25

Chromium (as hexavalent Cr) (mg/1)

0.05

0.05

26

Cyanides (as CN ) (mg/1)

0.05

0.05

27

Lead (as Pb) (mg/1)

0.05

0.05

28

Selenium (as Se) (mg/1)

0.01

0.01

29

Mercury (total as Hg) (mg/1)

0.001

0.001

30

Polynuclear

aromatic

hydrocarbons 0.2

0.2

(PAH ) (mg/1) 31

Presticides (total, mg/1)

Absent

Refer to WHO guidelines for drinking water quality Vol.I.-1993

Radio activity + 32 Gross Alpha activity (Bq/1)

0.1

0.1

33

1.0

1.0

Gross Beta activity(Bq/1)

NOTES * The figures indicated under the column ‘Acceptable’ are the limits upto which water is generally acceptable to the consumers. ** Figures in excess of those mentioned under ‘Acceptable’ render the water not acceptable, but still may be tolerated in the absence of a alternative and better source but upto the limits indicated under column “Cause for Rejection” above which the sources will have to be rejected. + It is possible that some mine and spring waters may exceed these radio activity limits and in such cases it is necessary to analyze the individual radio-nuclides in order to assess the acceptability or otherwise for public consumption.

b) Bacteriological Guidelines The treated water should be bacteriologically in good quality and any trace of bacteria of any kind must not be detectable in any 100 ml sample.


86


87 ANNEXURE III Unit cost

1. Unit cost at 1998-99 rate for Ground Level Service Reservoirs (sump) (including pipe connections) S.No

Description of work

Rate for 1998-99

1

Upto 5000 litres

10.20 per lit.

2

Above 5000 litres and upto 10000 litres

7.40 per lit.

3


5.80 per lit.

4


4.85 per lit.

5


4.20 per lit.

6


3.40 per lit.

7


2.85 per lit

8


2.55 per lit

9

Above 1000000 litres

1.75 per lit

2. Unit cost as per 1998-99 rates for RCC elevated Service Reservoirs (including pipe connections) S.No.

Description of work

1

10000 litres 6 m staging

Rate per 1998-99 Per litre 11.70

2


9.90

3


7.40

4


8.90

5

50000 litres 7.5 m staging

6.60

6


7.00

7

60000 litres 7.5 m staging

5.60

8


6.30

9

1 lakh litres 7.5 m staging

5.40

10

1 lakh litres 12 m staging

6.60

11

1.5 lakh litres 12 m staging

5.30

12

2.0 lakh litres 12 m staging

4.60



13

Above 2 to 5 lakh litres 12 m staging

4.20

14


3.85

15


3.50

16


3.45

17

Above 20 lakh litres 12 m staging

3.40

88

3. Unit cost at 1998-99- rate for Treatment works Sl. No

Description of work

Rate per 199899 per litre

1

Upto 2 mld

5.72

2

Above 2 mld and upto 5 mld

4.85

3


3.30

4


1.90

5


1.75

6


1.65

7


1.55

8


1.45

9

Above 200 mld

0.90

4. Unit cost at 1998-99 rate for pipe including anchoring arrangements Pumping Plants S.No. I

Description of Work

Rate per 199899 per HP

Pumpsets including cost of pipes, pipe connection works transformer, etc. BHP 1 to 2

12650

BHP 3 to 5

10350

BHP 6 to 10

8625

BHP 11 to 15

7475

BHP 16 to 35

6325

BHP 36 to 50

5750

BHP 51 to 100

5175

Turbine pumpsets above 100 HP

13800

Centrifugal pumpsets above 100 HP

11500



89 II

Standby Pumpsets (Rate for only pumpsets for jet, centrifugal and turbine pumpsets) 1 to 2 HP

4025

6 to 10 HP

3800

11 to 15 HP

3450

16 to 35 HP

3400

36 to 50 HP

3275

51 to 100 HP

3225

above 100 HP

3100



ANNEXURE IV

90

Discharge in pipes flowing full (Discharge in liters per minute ( diameter in millimeter) grade 1 over 80 10 15 25 35 50 75 100 150 200 250 300 350 400 500 600 700 800 900 1000 1250 1500 1750 2000 2500 3000 Note : 1)

2) 3)

628 505 383 319 263 212 181 146 125 111 100 92 86 76 69 63 59 55 52 42 36 29

100

125

150

200

250

2031 3280 907 1631 2635 5616 10100 689 1238 2000 4263 7687 574 1032 1667 3555 6393 474 851 1375 2932 5272 381 684 1105 2355 4236 326 586 946 2017 3626 262 470 760 1620 2914 224 403 651 1387 2495 199 357 577 1229 2211 180 324 523 1114 2004 166 298 481 1025 1844 154 277 448 954 1716 137 246 397 846 1521 124 223 360 766 1378 114 205 331 705 1268 106 191 308 656 1180 100 179 289 616 1108 94 169 273 582 1046 242 515 927 75 136 219 467 840 202 430 773 65 116 188 400 719 166 355 638 52 93 151 321 578

300

350

400

450

12390 10330 8517 6842 5859 4707 4030 3572 3238 2979 2771 2457 2226 2048 1905 1788 1690 1498 1357 1249 1162 1030 934

15490 12779 10260 8786 7058 6043 5357 4835 4467 4157 3684 3339 3072 2859 2682 2534 2247 2035 1874 1743 1545 1404

22010 18150 14580 12480 10030 8588 7612 6900 6348 5906 5235 4744 4365 4061 3812 3600 3193 2893 2662 2477 2196 1990

29980 24730 19860 17010 13670 11700 10370 9399 8648 8046 7132 6465 5947 5534 5193 4906 4349 3941 3626 3375 2990 2771

This table is prepared using Hazen – Williams formula, taking the Hazen – Williams Coefficient ‘C’ as 100 Adopt the appropriate Value for C particular pipe material. The head loss factor and discharge factor for various values of ‘C’ are as follows : value of ‘C’: 80 100 120 130 140 Head Loss Factor : 1.511 1.000 0.713 0.615 0.536 Discharge Factor : 0.80 1.00 1.20 1.30 1.40

Explanation: The initial pressure with which water is pumped in a pumping main would get reduced due to friction. This pressure loss due to friction is termed as ‘head loss’ and normally expressed as head loss as 1 m over a distance. For instance if the head loss due to friction is 1m over a distance of (ie length of pumping main) 1000 m it is expressed as 1/1000 or 1 over 1000.



91

ANNEXURE V Hydrostatic test pressure OF Pipe

S.No

1 1

2

Cast Iron IS:1537-1976

LA A B

A-dia(mm) Upto 600 600-1000 1000-1500

20 15 10

B-dia (mm) Upto 600 600-1000 1000-1500

25 20 15

Usual Dia in mm

Pipe IS No

2 Spun Iron IS:1536-1989 3114-1985

Test Pressure at works Kg/Cm2 =10m of water 5 35 35 35

Pipe &

Pipe

3 80,100,125, 150-50-500 600,700,750, 800,900,1000 1050 80,100,125 15050-500 600,700,750 800-100-1200 1500

Class

4

3

AC Pressure Pipes IS:1952-2003

50, 65, 80,100, 125, 150-50-500 , 600

10 15 20 25

10 15 20 25

4

RC Pipes 1988

80,100,150 250-50-500100-1200

P1

2

80,100,150, 250-50-500600,700,800, 900,1000

P2

4

80,100,150,250, 300,350,400, 500,600,700,800 20 mm to 315 mm OD

P3

6

Cl.2.5 4 6 10

5 8 12 20

5

PVC Pipe

IS:458-


MPA 1.0 1.5 2.0 2.5

Maximum working pressure at field kg/cm2 6 12 18 24

Not less than 2/3 of the works test pressure maintained for the field test pressure are less, the period of test should be atleast 24 hours, the test pressure being gradually raised at the rate of 1kg/cm2/min Maximum working pressure will be half the test pressure in each case For use on gravity mains only working pressure not to exceed two-thirds of test pressure For use in pumping mains working pressure not to exceed half the test pressure. 2.5 4 6 10


92 6

Steel cylinder RC pipes IS 1916-1963

200-50-500, 600 700,900,1100, 1200-200-1800

7

Prestressed concrete pipes IS 784-2001

80,100,125,15050-500-1001200-200-1800

8

MS Tubes 1239 (part I) 1982

9

Electrically Welded steel pipes IS:35892001

6-100 6-150 6-150 200-2500

10

Ductile Iron IS:8329:2000

Pipe

80-2000

1 2 3 4 5 4 6 8 10 12 14 16 18 20 Light Medium Heavy 1 2 3

5 10 15 20 25 1.5 times design pressure

K7 K9 K10

Separately given

50 50 50 15 20 25

4 6 8 10 12 14 16 18 20

Depending upon thickness of steel plate & tangible strength given separately As applicable to CI/DI pipe

Note: 1. S.No. 1,3,4,5,7 & 9 are commonly used 2. Normal working pressure excludes surge pressure 3. Normal working pressure plus surge pressure not to exceed field test pressure 4. RCC P. pipe shall be for use on gravity main only 5. Except for CI and Steel pipes, the normal working pressure shall be generally half of the work test pressure for pumping mains and two thirds for gravity mains 6. The sizes indicated against PVC pipes are outer diameter. Electrically welded steel pipes - Hydraulic Pressure Test The IS 3589 : 1981 has been revised and a third revision was issued in IS 3589 : 2001. In this revised publication, number of changes had been made and one of the major change was in Hydraulic Pressure Test which is worked out by the following formula. P = 2ST/D Where P = Hydraulic test pressure in Mpa D = Specified out side diameter of pipe in mm. T = Specified thickness of the tube in mm. S = Stress 60% of the specified minimum yield in Mpa.



93

The maximum test pressure to be limited to 5 mpa where over applicable. Hence the scheme designed from 2001, the above formula may be adopted for working out the hydraulic test pressure for the specified steel grade used for manufacturing the steel pipe where as in the earlier code (VTL IS 3589:1981) the value of ‘S’ who considered as 40% of the yield stress in mpa. Besides IS – 35891:2001 also prescribe 3 steel grade with different tensile strength as detailed below. Steel grade Fc 330 Fc 410 Fc 450

Tensile strength in mpa. 330 410 450

The Hydraulic test pressure of different size of MS pipe adopted by TEAD board is worked out given below for ready reference.



94

Sl. No

1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Outer Specified diameter of thickness the pipe in in mm (t) mm (D) 2 460 462 510 512 560 562 612 614 712 714 764 766 814 816 864 866 916 920 1016 1020 1066 1070 1116 1120 1166 1170 1216 1220 1270 1272 1320 1322 1370 1374 1420

3 5 6 5 6 5 6 6 7 6 7 7 8 7 8 7 8 8 10 8 10 8 10 8 10 8 10 8 10 10 11 10 11 10 12 10

Stressing Mpa (60% of minimum tensible strength (S) for Steel of minimum strength of different grade say 330 410 450 mpa mpa mpa 4 5 6

198 Mpa


246 Mpa

270 Mpa

Hydraulic test pressure in Mpa P = 2st/D For steel of minimum tensile strength of 330 mpa 7 4.304 5.143 3.882 4.641 3.536 4.228 3.882 4.515 3.337 3.882 3.628 4.136 3.405 3.882 3.208 3.658 3.459 4.304 3.118 3.882 2.972 3.701 2.839 3.536 2.717 3.385 2.605 3.246 3.118 3.425 3.000 3.295 2.891 3.459 2. 789

410 mpa 8 5.348 6.390 4.824 5.766 4.393 5.253 4.824 5.609 4.146 4.824 4.508 5.138 4.231 4.824 3.986 4.545 4.297 5.348 3.874 4.864 3.692 4.598 3.527 4.393 3.376 4.205 3.237 4.033 3.874 4.255 3.727 4.094 3.591 4.297 3.465

450 mpa 9 5.870 7.013 5.294 6.328 4.821 5.765 5.294 6.156 4.551 5.294 4.948 5.640 4.644 5.294 4.375 4.988 4.716 5.870 4.252 5.294 4.053 5.047 3.871 4.821 3.705 4.615 3.553 4.426 4.252 4.670 4.091 4.493 3.942 4.716 3.803


36 37 38 39 40

1424 1470 1474 1520 1524

12 10 12 10 12

3.337 2.694 3.224 2.605 3.118

4.146 3.347 4.005 3.237 3.874

4.551 3.673 4.396 3.553 4.253

Ductile Iron Pipe ( IS 8329:2000) ( In mpa pressure head) Size pipe mm

of Allowable operating in excluding surge K7

80 100 125 150 200 250 300 350 400 450 500 600 700 750 800 900 1000 1100 1200 1400 1500 1600 1800 2000

.8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8 .8

pressure Allowable maximum test pressure

K9 6.4 6.4 6.4 6.4 6.2 5.4 4.9 4.5 4.2 4.0 3.8 3.6 3.4 3.3 3.2 3.1 3.0 2.9 2.8 2.8 2.7 2.7 2.6 2.6

K10 7.7 7.7 7.7 7.7 7.4 6.5 5.9 5.4 5.1 4.8 4.6 4.3 4.1 3.9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 3.2 3.1 3.1

1 Mpa

=

10.2 Kg / cm2

1 Kg/cm2

=

10m pressure head


K7 1.7 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75 1.75

K9 9.6 9.6 9.6 9.6 7.9 7.0 6.4 5.9 5.6 5.3 5.1 4.8 4.6 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.7 3.7 3.6

K10 9.6 9.6 9.6 9.6 9.6 7.8 7.2 6.6 6.3 5.9 5.8 5.4 5.1 4.9 4.8 4.7 4.6 4.3 4.3 4.2 4.1 4.1 4.1 4.0

95


Hydrostatic test for Bar Wrapped Steel Cylinder (BWSC) pipe (IS 15155:2002) The hydrostatic pressure is determined by the following formula: 2Sty P= D yi Where, P = Minimum hydrostatic test pressure in N/mm2 S = Stress in pipe wall during hydrostatic test in N/mm2, which shall be 0.75 times the specified minimum yield stress of the steel used, or as specified by the purchase; ty = Cylinder thickness in mm; and D y i = Inside diameter of steel cylinder in mm. Note: Normally the specified minimum yield stress of steel used for BWSC pipe Fe = 250 N/mm2 The Hydrostatic test provision is worked our adopting minimum yield stress of steel Fe = 250 N/mm2 Factory test pressure = 75% of the minimum yield strength of steel used in the cylinder or stress not exceed 187 N/mm2 Site test pressure = 66% of the minimum yield strength of steel used in the cylinder or stress not exceed 165 N/mm2 Working pressure = 50% of the minimum yield strength of steel used in the cylinder or stress not excess 125 N/mm2 Clause 7.31 of IS 15155: 2002 Nominal Internal Diameter, Minimum wall thickness (t min) and Minimum thickness of the Cement Mortar Lining (t i min) , Inside diameter of steel cylinder ( Dyi) in mm factory test pressure, working pressure for difference size of pipe is given below Nominal Internal Diameter of Pipe

t min Minimum wall thickness

250 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

40 40 40 45 45 45 45 45 45 50 50 50 50 50 50

t i min Minimum thickness of the cement mortar lining 15 15 15 20 20 20 20 20 20 22 22 22 22 22 22

Minimu m Cylinder Thickne ss 1.6 1.6 1.6 1.6 2.0 2.0 2.0 2.5 2.5 4.0 4.0 4.0 4.0 4.0 4.0


Minimum Thickness of Joint Rings 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 7.0 7.0 7.0 8.0 8.0 8.0 8.0

Inside diameter of steel cylinder (Dyi) 280 330 430 540 640 740 840 940 1040 1144 1244 1344 1444 1544 1644

Factory test pressure N/mm2

Working pressure N/mm2

2.1429 1.8182 1.3953 1.1111 1.1719 1.0135 0.8929 0.9973 0.9014 1.3112 1.2058 1.1161 1.0388 0.9715 0.9124

1.4286 1.2121 0.9302 0.7407 0.7813 0.6758 0.5952 0.6649 0.6010 0.8741 0.8039 0.7440 0.6925 0.6477 0.6083

96


97 2

2

2

Note:- (1) N/mm = mpa, N/mm x 10.2 = Kg/cm

(2) Pipe with internal diameters other than those mentioned in this table and pipes for working pressure higher than 28 Kg/ Cm2 can be supplied by mutual agreement between the purchaser and the manufacturer.



ANNEXURE VI

98

Economic Calculation of Pumping Main Table . I Frictional loss Size distance mm* m intermediate stage Qty. Grade frictional 1pm Loss

Ultimate stage Qty. Grade frictional 1pm Loss

• The initial choice of pipe size is with reference to the velocity range normally between 0.3 and 0.6m/sec • Table II Total head Size mm

Static Lift * m Intermediate stage Frictional Other. Total

Ultimate stage Frictional

Other.

Total Loss

Losses Head

Loss

Losses Head

* Static head is the difference in level between foot value level of pumping installation at Head works and hydraulic level at reservoir at 2m above the maximum water level of reservoir or maximum ridge in the pumping main alignment, whichever is higher.

Table III Horse power Size Mm

Intermediate stage Oty Head BHP* 1pm m

Ultimate stage Qty Head BHP* 1Pm m

* BHP (For 50% Qty . to lifted in 1pm X total head in m x 2 Efficiency) = 60 X 76.06 Table IV-cost of pump sets Size mm

Intermediate stage

Ultimate stage

Total Cost

1

BHP Rate/ HP Amt 2 3 4

BHP Rate/ HP Amt. Eq.Cost 5 6 7 8

9 (4+8)

Col.8 = Col.7x Equivalent cost factor (for 15 years at the prevailing rate of interest)



99 Table V Electrical Energy Size mm 1

* ÷

Intermediate stage

Ultimate stage

Total Cost

BHP Units Cost Capitalized* 2 3 4

BHP Units Cost Capitalized*Eq.Cost 5 6 7 8 11 (5+10)

Capitalized cost = Cost ÷ annuity factor for 15 years . Equivalent = capitalized cost X Equivalence factor for 15 years.

Note : 1 In calculating the electrical energy, the average working hours should be taken into account, for example : if the working hours or pumping hours is 16

Average working hours during intermediate stage

Present population 16 + ------------------------- x 16 Intermediate. Population ------------------------------------------2

Intermediate Population 16 + ------------------------------ x 16 Ultimate population -------------------------------------------2 2. HT Supply shall be availed when connected load as per table III is 75 HP and above and LT supply shall be availed when connected load as per table III is less than 75 HP Average working hours at ultimate stage

3. The head loss due to friction in pipe line is calculated by referring to velocity discharge table or using the following formula Frictional loss per m length of pipe as per Hazen Williams formula .hf = 1.13 x 109 Q1.85 C1.85 d4.87 Where .hf = frictional loss inm Q = discharge in m3/hr .d= diameter of pipe in mm c = Hazen-William Co-efficient of smoothness Table VI. Size of main mm

Cost of Pumping Main

Length of main m


Rate Rs/m

Amount Rs.


Table VII. Size of main mm

Cost of pumping main (Amount from Table VI)

1

100

Cost of Installation

2

Cost of pumpset (Total Cost)

Total Cost of installation

from Table IV) 3

4 (2+3)

Table VIII. Cost of Installation and Maintenance Size of Main mm

Total cost of installation (from Table VII) 1

2

Cost of electrical energy (Total cost From Table V) 3

Total cost of installation and maintenance

4 (2+3) The size corresponding to minimum cost from the Table VIII is the most economical size of the pumping main.

NOTE: 1. Now the Economic calculation of Pumping /Conveying/gravity main is designed using computer software 2. The software package now being used in TWAD Board prescribed for total head required at each reaches of the pipeline. Where as the size, class and type of pipe of is adopted for the particular discharge and slope manually. While choosing the pipe, the size and class and type of pipe is used to inflate by them. This could be examined with discharge table for CI Pipe using C value 100 is given in AnnexureIV



ANNEXURE VII

101

Earth work calculation for pipe laying. Earth work excavation for pipe line works on linear measurement basis (TWAD Board Schedule of Rate) Type

CI CI CI CI CI CI CI CI CI CI CI CI CI CI CI CI CI CI CI ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL15 ACCL10

Dia in mm Width of Depth of trench at bottom of bottom in pipe m below GL in m 80 0.75 1.05 100 0.75 1.05 125 0.75 1.05 150 0.75 1.05 175 0.75 1.05 200 0.80 1.10 225 0.80 1.10 250 0.80 1.20 300 0.80 1.35 350 0.90 1.45 375 0.90 1.45 400 0.90 1.55 450 1.00 1.70 500 1.00 1.85 525 1.00 1.85 600 1.10 2.05 675 1.20 2.30 700 1.20 2.30 750 1.25 2.45 80 0.75 1.05 100 0.75 1.05 125 0.75 1.05 150 0.75 1.05 175 0.75 1.05 200 0.80 1.10 250 0.80 1.20 300 0.80 1.35 350 0.90 1.45 400 0.90 1.55 450 1.00 1.70 500 1.00 1.85 600 1.10 2.05 80 0.75 1.05


Outer dia Earth of the pipe work quantity

Refilling quantity

0.098 0.118 0.144 0.170 0.170 0.222 0.222 0.274 0.326 0.378 0.378 0.429 0.48 0.532 0.532 0.635 0.738 0.738 0.790 0.104 0.124 0.151 0.178 0.178 0.235 0.286 0.340 0.396 0.452 0.502 0.559 0.658 0.104

0.780 0.777 0.771 0.765 0.765 0.841 0.841 0.901 0.997 1.193 1.193 1.251 1.519 1.628 1.628 1.938 2.332 2.332 2.573 0.779 0.775 0.770 0.763 0.763 0.837 0.896 0.989 1.182 1.235 1.502 1.605 1.915 0.779

0.79 0.79 0.79 0.79 0.79 0.88 0.88 0.96 1.08 1.31 1.31 1.40 1.70 1.85 1.85 2.26 2.76 2.76 3.06 0.79 0.79 0.79 0.79 0.79 0.88 0.96 1.08 1.31 1.40 1.70 1.85 2.26 0.79


ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 ACCL10 PVC PVC PVC PVC PVC PVC PVC PVC PSC PSC PSC PSC PSC PSC PSC PSC PSC GI GI GI GI GI GI GI GI GI GI GI

100 125 150 175 200 250 300 350 400 450 500 600 40 50 63 75 90 110 125 140 350 400 450 500 600 700 800 900 1000 15 20 25 32 40 50 65 80 100 125 150

0.75 0.75 0.75 0.75 0.80 0.80 0.80 0.90 0.90 1.00 1.00 1.10 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.90 0.90 1.00 1.00 1.10 1.20 1.25 1.40 1.50 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75

1.05 1.05 1.05 1.05 1.10 1.20 1.35 1.45 1.55 1.70 1.85 2.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.45 1.55 1.70 1.85 2.05 2.30 2.45 2.60 2.70 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05


0.124 0.149 0.175 0.175 0.229 0.281 0.333 0.389 0.436 0.486 0.541 0.648 0.04 0.05 0.063 0.075 0.09 0.11 0.125 0.14 0.464 0.514 0.564 0.614 0.724 0.824 0.934 1.054 1.164 0.02 0.03 0.03 0.04 0.05 0.06 0.07 0.09 0.11 0.14 0.16

0.79 0.79 0.79 0.79 0.88 0.96 1.08 1.31 1.40 1.70 1.85 2.26 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 1.31 1.40 1.70 1.85 2.26 2.76 3.06 3.64 4.05 0.788 0.788 0.788 0.788 0.788 0.788 0.788 0.788 0.788 0.788 0.788

0.775 0.770 0.763 0.763 0.839 0.898 0.993 1.186 1.246 1.515 1.620 1.925 0.629 0.628 0.627 0.626 0.624 0.621 0.618 0.615 1.136 1.188 1.450 1.554 1.844 2.227 2.378 2.768 2.986 0.787 0.787 0.787 0.786 0.786 0.785 0.784 0.781 0.778 0.772 0.767

102

Water Supply Hand Book

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