WATER SUPPLY SCHEME



      GUIDELINES  FOR  PREPARATION  OF  DPR FOR  WATER SUPLY SCHEME

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GUIDELINES

REFERENCE

1.

Conducting topographical survey of the project area for which DPR is to be prepared and preparing contour plan 1m interval.

 

2.

Soil Investigation to be conducted at proposed WDS site and also for 10% of network length of project area along the roads

 

3.

Preparation of Base Map with Ground levels marking all the major roads, canals, rivers , monuments , TBM in Auto CAD format.

 

4.

Labelling junction points, roads meeting end points as Node numbers and roads as pipe numbers in the base Map. The node to node distance is also marked.

 

5.

Population Projection The population projection for the entire project areas is done based on the following methods recommended by CPHEEO.

  1. Arithmetical increase
  2. Geometrical progression
  3. Incremental increase method
  4. Method of Least square method
  5. Decreasing rate of Growth method
  6. Graphical Method
  7. Logistic Method
  8. Method of Density
  9. City Development Plan (CDP) growth rate (Generally CDP Growth rate is adopted)

 As pet the details collected from census department (At least three decade population is required) for projection of population for Base year, intermediate year and Ultimate year.

Base year is the year at which the designed system of the project area is put in to use.

(generally 4 years 6 months from the present year (preparation and approval DPR – 12months + tender process – 6 months + implementations – 21/2 years + effecting house service connections – 6 months).

Intermediate year is 15 years from base Year. Usually, the pumps are designed for intermediate year.

Ultimate year is 30 years which is the design period. 

CPHEEO, Page No. 7-9, Chapter 2, CI.2.2.7

6.

Zoning of project area is be done if necessitated based on the constraints like land availability for WDS construction and any physical barrier like canals/railways/major roads/Highways etc.  

 

* If there is elevation difference of 15 to 25 m between Zones, then each zone should be served by a separate system”

“The layout should be such that the difference in pressure.

Between different areas of the same zone or same systems does not exceed 3 to 5m”

CPHEEO, Page No. 360, Chapter 10,  10.2.3

6a.

Design norms

Per Capita water supply Considered for design of water supply is 150 lpcd as per CPHEEO norms.

 

Based on the recommended per capita water supply, the water demand for each node will be calculated.

 

1. Town provided with Piped water supply but without sewerage system.

 

2. Cities provided with piped water supply where sewerage system is existing /completed

 

3. Metropolitan and Mega cities provided with piped with piped water supply where sewerage system existing/completed  

CPHEEO, Chapter 2 ,  Table 2.1 Pg.11

 

 

 

 

 

70

 

 

 

135

 

 

150

 

6b

Peak factor

 

The water demand at each node is to be multiplied by the Peak factor recommended by the CPHEEO to arrive at Ultimate Peak flow (Qupf).

 

Population                                         Peak factor

 

Up to 50,000                                              3.00

 

Above 50,000 to 2,00,000                         2.50

 

Above 2,00,000                                         2.00

 

For small water supply

Schemes 9Where supply

Through stand post for)

CPHEEO,

Pg.No. 361, Chapter 10, 10.3.1

6c

Residual pressure

 

* Distribution system should be designed for the following minimum residual pressure at ferrule points”.

 

Single storey building  -  7m

Two storey building     - 12m

Three storey building   - 17m

CPHEEO,

Pg.No. 361, Chapter 10, 10.3.1

6d

Minimum pipe size of Distribution system

 

100mm – Population less than 50,000

250mm – Population above 50,000

CPHEEO,

Pg.No. 361,

Chapter 10, 10.3.4

6e

Location of Mains

CPHEEO,

Pg.No. 362,

Chapter 10,

 10.3.8

7

Design of Distribution System

LOOP

Design of distribution system is done using LOOP software. The ………….. such as nodal flew, G.I. Pipe length, minimum residual pleasure at  ……….. Maximum residual pressure, Reservoir Level, Hazen williama constant and cost of pipe per m.

 

Outputs:

Pipe diameters with coal, velocity, nodal pressure, pipe pressure.

 

Based on the output from Leep software, the detailed estimate and cost estimate will be prepared.

 

Generally DI pipes class k 7 are adopted for distribution system

 

8.

Valves

  1. ……… values should be located on at least three sides of every cross junction and at every kilometer on long main

Size of 8V

  1. For pipe sizes up to 300mm . Same size as pipe.
  2. For Pipe sizes greater than 300mm : About 2/3 of pipe size

 

Seour Valves

For all sizes : (d/2)+25mm

           Where d is the dia of main in mm

Air Valves

Commonly adopted  sizes are as follows :

 

Size of main             Type             Size of Air Valve

80 mm                     Single                             20mm

100mm                    Double                           40mm

125 - 200mm          Double                             50mm

250 - 350mm          Double                             80mm

400 - 500mm          Double                           100mm

600mm                    Double                           150mm

CPHEEO,

Pg.No. 362,

Chapter 10,

 10.3.9

 

 

 

 

 

 

 

Pg. No. 44, Handbook for Public health Engineers, by Indian Water Works Association.

9

ONT & UGT

  1. 1/3rd Intermediate peak demand is considered for calculating OHT Capacity
  2. 1 hour Ultimate peak demand is considered for UGT capacity.

Staging height of OHT considered is 17m.

 

 

The Structural design OHT UGT is done based on the soil investigation report and accordingly the detailed and cost estimate is prepared.

 

Feeder main and Conveying Main

The size of Feeder main from UGT to OHT is calculated based on economical design and Class of DI pipe is decided based on the surge pressure calculation.

 

Similar, the size and class of the conveying main from Tapping point to UGT is worked out on the basis of economical design and surge pressure calculation.  

 

10.

Pumps – Horizontal split casing centrifugal pump sets (2w +1 Standby)

 

Based on the size required for placing panel, office room, pumps, the size of pump house will be decided.

 

Based on the flows and pump size, the estimate for pumping machineries and allied works is prepared.

 

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