Sediment Basins (Math Portion)

Question 1

A settling basin has the following dimensions: 200 feet long 50 feet wide and six feet average depth. What is the pond volume in million gallons?

200’ x 50’ x 6’ = 60,000 cf 60,000 cf x 7.48 (1 cf converted to 1 gallon) = 448,800 gallons to million gallons = _____ million gallons

Answer 1

0.45 million gallons

Question 2

A settling basin covers 5 acres and is 7 feet deep. How many cubic feet will it hold?

Volume - 5 acre x 43,560 sq feet (1 acre to sq feet is 43,560) x 7 feet =

Answer 2

1,524,600 cubic feet

Question 3

A rectangular concrete channel has a cross sectional area of 4.5 square feet. By use of a porable flow meter, it was determined that the average flow velocity was 0.6 feet per second. What was the flow rate in million gallons per day?

Flow rate = 4.5 sq feet x .6 feet/sec = 2.7 cubic feet/sec 2.7 cf/sec x 60 sec/min x 1440 min/day = 233,280 cf/day

233,280 cf/day x 7.48 gallon/cf x million gallon = _________

Answer 3

1.74 million gal/day

Question 4

I changed the force main pipe size from 4” PVC to 6” PVC. If they are flowing full at the same velocity, what would be the increase in the flow rate I can expect?

Pipe diameter increased 1.5 times, cross sectional area of the pipe was increased 2.25 (1.5 x 1.5), and if the velocity remains the same, the flow rate increased by __________ times.

Answer 4

2.25 times.

Question 5

An 8 inch pipe is flowing full at a velocity of 2.0 feet/sec. What is the flow rate in GPM?

[8/12)^2 (3.14/4] = 0.35 sf Flow rate = .35 sf x 2.0 feet/sec x 60 sec/min x 7.48 gal/cf = _________

Answer 5

314 gal/min