septic tank sizing/flows 1

[mrnico]

The local state enviro office is hassling us over the design flows for a small septic system we need at a local park. The bathroom will have 1 toilet/1 urinal/1 sink in the men's side ans 2 toilets/1 sink in the women's, plus a floor sink for the janitor.

She (state) is asking for volume calcs based on fixture units, specifically table 7-3 of the UPC, which I do not have.

I had used 7 fixtures x 31.1gal/day/fixture = 218 gal/day
2.5 day detention time = 544 gal min cap of tank. The local installers had a 900-gal tank as their smallest size, so I chose that. Now she (state)is saying that is too small!

Any ideas on how to 'properly' do the calculation? Thanks.

 

[PEDARRIN2]

Based upon normal flush rates of toilets with flush valves which is 1.6 gallons per flush, 218 gpd would be only 136 flushes in a day. Assuming normal operation during day light hours - say 12 hours, that would be about 12 flushes per hour or once every five minutes. That doesn't sound too outlandish especially if there is an event at the park or there are a lot of people there.

In the International Private Sewage Disposal Code, the minimum tank size is 750 gallons. Then you add volume for buildings other than residence.

For parks you add 5 gallons per person and assume 75 persons per acre. If you have only one acre, that would be an additional 375 gallons to add to your tank.

You might want to look at that approach, resize the tank and see what she says.

 

[dicksewerrat]

What about the leach field? Do you have room for that or are you going to pump out each day?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com