Storm and Sanitary sewer grade conflict - options needed
Storm and Sanitary sewer grade conflict - options needed
(OP)
Hi everyone,
I am working on project, in which we have a grade issue with storm and sanitary sewers. At the crossing of the two sewers, the 12" sanitary will be going exactly through the center of the 42" storm sewer. There is no room to adjust the grades of either sewer. I need to come up with a creative solution. Has anyone ran into a similar problem, and what was your solution?
So far I have come up with the following solutions:
1. Install sanitary sewer through a storm manhole structure to where the two cross. The sanitary sewer pipe could be installed through a pipe casing that is fixed the the MH structure. I would have to prove the sanitary pipe going through the MH does not impact the flow capacity of the storm. This method is definitely not ideal, but would be cost effective.
2. Inverted siphon of the sanitary under the storm. Due to low sewer flows and maintenance issues, this is my least preferred option.
3. Install a pump station and forcemain to pump the santitary flows above (or below) the existing storm. Continue by gravity after that point.
It will be a challenge to get options 1 and 2 approved by the city.
Attached is a very crude sketch of my 3 options.
Thanks,
Dan
I am working on project, in which we have a grade issue with storm and sanitary sewers. At the crossing of the two sewers, the 12" sanitary will be going exactly through the center of the 42" storm sewer. There is no room to adjust the grades of either sewer. I need to come up with a creative solution. Has anyone ran into a similar problem, and what was your solution?
So far I have come up with the following solutions:
1. Install sanitary sewer through a storm manhole structure to where the two cross. The sanitary sewer pipe could be installed through a pipe casing that is fixed the the MH structure. I would have to prove the sanitary pipe going through the MH does not impact the flow capacity of the storm. This method is definitely not ideal, but would be cost effective.
2. Inverted siphon of the sanitary under the storm. Due to low sewer flows and maintenance issues, this is my least preferred option.
3. Install a pump station and forcemain to pump the santitary flows above (or below) the existing storm. Continue by gravity after that point.
It will be a challenge to get options 1 and 2 approved by the city.
Attached is a very crude sketch of my 3 options.
Thanks,
Dan





RE: Storm and Sanitary sewer grade conflict - options needed
RE: Storm and Sanitary sewer grade conflict - options needed
RE: Storm and Sanitary sewer grade conflict - options needed
cvg, as always, has some good comments concerning system hydraulics and debris issues from the conflict manhole. It is, however, probably the best way to do it from a maintenance point of view.
If you go to the website of your nearest large utility, they will probably have a design standard drawing for such a manhole. If your local doesn't you can find one by searching jea.com. I'd attach a copy but my computer is broken and I can't get to my library.
RE: Storm and Sanitary sewer grade conflict - options needed