Existing Flat Sewer
Existing Flat Sewer
(OP)
I have a new project for a school that will build a 2,000 seat arena at an existing campus. The arena will generate 310 Fixture Units, or about 0.25 cfs during peak use.
The sanitary tie in will be a private 4" lateral, currenty serving a maintenance building and baseball concession stand (low use). After having the lateral exposed and shot for location and elevation, I calculated it is 900-feet at 0.1% slope to the tie in public manhole.
The mannings capacity for the pipe is a quarter of expected peak flow, at about 0.06 cfs.
The question for me is do I just design 900 feet of new bipass line down an existing road, or propose a connection to the undersized (and old) line.
For the second option, I would propose a new sanitary manhole. Flows above existing downstream capacity could surcharge the manhole temporarily until catching up.
Normally I wouldn't consider anything but a new bypass line, however the arena's peak use will be limited to a few times a year at best (basketball games).
Any opinions?
The sanitary tie in will be a private 4" lateral, currenty serving a maintenance building and baseball concession stand (low use). After having the lateral exposed and shot for location and elevation, I calculated it is 900-feet at 0.1% slope to the tie in public manhole.
The mannings capacity for the pipe is a quarter of expected peak flow, at about 0.06 cfs.
The question for me is do I just design 900 feet of new bipass line down an existing road, or propose a connection to the undersized (and old) line.
For the second option, I would propose a new sanitary manhole. Flows above existing downstream capacity could surcharge the manhole temporarily until catching up.
Normally I wouldn't consider anything but a new bypass line, however the arena's peak use will be limited to a few times a year at best (basketball games).
Any opinions?





RE: Existing Flat Sewer
I would suggest replacing all of the sewer with a properly sized and sloped gravity line or an ejector system and force main.
RE: Existing Flat Sewer
One rule of thumb is to assume that 25% of the patrons will use the restroom during an intermission. That would calculate to an estimated sanitary flow of around 50 gpm. That is about 1/2 of what you estimated.
Sure you may save a few dollars to skip the installation of a new lateral, but how much of an embarassment would it be to have a sewer overflow on a brand new project?
The existing sewer line is inadequate and should be increased in capacity.
RE: Existing Flat Sewer
RE: Existing Flat Sewer
I had a project where we had to add a second grinder pump station to handle PEAK FLOWS for the concession/snack bar/bathroom out building at a high school sport field.
RE: Existing Flat Sewer
I just don't think it is worth the risk, so I am proposing a bipass sanitary line.
If the owner needs to start cutting costs after bids come in, I could propose that to them as an option. At least then it would be easier for me to explain the risks involved and let it be their decision.
RE: Existing Flat Sewer
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Existing Flat Sewer
RE: Existing Flat Sewer