Size for a dry well?

How large a dry well would you recommend for a sump pump that will puts out atleast 2 gallons/min. for 5-6 days after a heavy rain? At peak times it will be putting out 3-4 gallons/min.

I've got a contractor who says he'd put in a 24' wide basin that's 2-3 foot deep with drainage at the bottom. Is that enough? It seems liked it'd quickly be filled.

One foot of depth in a 2 ft diameter basis is 3.14 cubic feet = 23.5 gallons. At 4 GPM that would fill in just under 6 minutes.

EDIT: I missed the FEET and was thinking of the sump for the pump.

mikrobmus said:

... a 24' wide basin that's 2-3 foot deep ...

Click to expand...

Is that 24' round, or 24' X what?

24' round X 3' deep = over 10,000 gallons, and your maximum numbers (6 days X 4 gpm) multiply out to a little over 8,000 gallons, yet how much rain will your otherwise-dry pond simultaneously receive all by itself? Also, your soil's percolation tests should/could be considered.

Just remember to put it down hill and far form the house.