dry well design

[ECUBA]

Hello, I have a project where the Bldg. Dpt. require to design a dry well for a 15 CF/H condensate drain from AH in a commercial bldg.

Does somebody can help me with this?

 

[dicksewerrat]

you will have to test the soil to see how much water it will drain away per sq. ft. then you need to see if you have enough area to drain your 15 CF each hour for as long as the unit runs. this may be a very large area.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[ECUBA]

Dear dicksewerrat: I did the calculation and I have the following new flow 0.714 CFH.

The civil engineer say that the HYDRAULIC CONDUCTIVITY (K)=7.93E-04 (acording Percolation Test Report)

How I know the FRENCH DRAIN dimentions required?

THANK YOU

 

[CarlB]

here's a link to a study and a tacoma design guide that may help....

http://www.wsdot.wa.gov/Research/Reports/500/589.1.htm

and

http://www.cityoftacoma.org/Page.aspx?hid=951

(Vol 5 Chap 7)

 

[harboe]

Less than 0.714 cubic foot per hour is not very much so that is good. What are the units on the K value? ft/hour? cm/sec? Probably a good place to start would be to get a copy of the soil report, assuming your project has one (ask civil engineer), and look at the boring logs. Looking at the soil strata you will need to put the outlet of the drywell in an area of the soil matrix that appears to be the most condusive to infiltration, i.e. SAND. For example, if there is clearly a sand layer from 5feet to 10 feet below the surface you will probably want to sink your drywell down to 6-7 feet below the ground. You will want to check in with the geotechnical engineer and get their okay that you are infiltrating. They usually do not recommend any infiltration near the building footrpint.

Since you are dealing with such a small amount you may be able to use a frech drain too. With a french drain you can locate a perforated drain pipe in a 3'W 3'H X'L trench backfilled with gravel wrapped in filter fabric. Size the bottom of the trench area (3'xL) so that 0.714ft3/hr drains at the rate of the K value (7.93E-04 Ft/s? ft/hr?).