Drainage design

Here is a example of drainage design done by us for pali village of kheda district;gujarat;india.

To design drainage of any area following steps may become useful to you

1)FIRST TAKE THE R.L.READINGS OF THE AREA
We taken the RL of area with the help of dumpy level

2)CALCULATE HOUSE HOLD PER STREET AND FINALLY FOR WHOLE AREA

As per NBC code in rural area 70 to 100 lpcd are supplied for various purpose. Now we assume 70 % total waste water generated from supplied water.

Following figure shows number of houses per street and we assumed average 5 household per house. The black line in following fig. representing the direction of main sewer line based on RL of the points.

3)DECIDE THE DIRECTION OF DRAINAGE LINE AND CALCULATION OF DIAMETER FOR PIPE

So, now following are the calculation for total discharge of the bazar area.

Total number of house hold at y point are 399.

So, total population of it= 399*5=1995

Now we predict the future population by geometric increase method….

Growth rate=17.28

P2021= 1995(1+17.28/100)

= 2340

Now take extra 5 % for commercial shops and other common facilities like schools, hospitals etc.

Total population=2340+117=2457

Now take 100 lpcd supply in the village as per NBC code. And total 70 % of it is generated as waste water.

Amount of water=2457*70=171990 lpcd

= 0.0239 M3 /S

Assume velocity=0.7 M/S

Q=VA

A=0.0239/0.7=0.034125 M2

D=20.84 cm for circular pipe.

So provide main pipe of 20 cm diameter from point j to y and provide 15 cm pipe from x to point all other pipes are of 10 cm diameter.

DESIGN OF SEDIMENTATION TANK:

Assume detention time=3 hr

.

Volume of tank = flow* detention time

= (171990*10-3 *3)/24

=21.498 M3

So provide 25 M3

Assume depth of tank=1.5 m

Surface area=25/1.5=16.66 m2

Provide 18 m2

Assume L/B = 3.

SO L = 3B

A = 3*B*B

18 = 3*B*B

B = 2.449 M

L = 3*B=7.347

So, provide L=7.5 m B= 2.5 and D=1.5+0.2=1.7 m

Provide extra 0.2 m depth for sludge accumulation

After sedimentation treatment water should be given to the field to grow the grass. And this grass will earn some revenue for village.

DESIGNED BY : AKSHAYKUMAR B. ARDESHANA 

                                                                  &

                               RACHIT R. SITAPARA