remote sewer service application
remote sewer service application
(OP)
Hi All,
Here is the scenario: I am designing 2,400 LF of gravity sewer for a small on-mountain restaurant for a ski area. I have performed a hydraulic analysis and the flows/velocities, etc. suggest a 4-in diameter pipe is ample. Peak flows (with peaking factor of 4) are only 0.02-cfs (+/-8 gpm), velocities are less than 10 fps, and the max. depth is less than 1/2-inch. There are NO regulatory requirements (local or State) that dictate the pipe size/materials (eg. min. 8-in pvc w/ manholes).
We are tentatively recommending a 4-inch HDPE pipe system with clean-outs every 250-ft or so (based on local jetting limitations) using direct burial with screened material (the one-way trucking trip for imported gravel is over 1.5 hours). The heartburn I have is related to everyone's expectations for a traditional main-manhole system. Does anyone have any experience with using a 4-inch diameter pipe for long stretches for a hard-to-get-to location private application?
All comments are welcome. Thanks!
EG
Here is the scenario: I am designing 2,400 LF of gravity sewer for a small on-mountain restaurant for a ski area. I have performed a hydraulic analysis and the flows/velocities, etc. suggest a 4-in diameter pipe is ample. Peak flows (with peaking factor of 4) are only 0.02-cfs (+/-8 gpm), velocities are less than 10 fps, and the max. depth is less than 1/2-inch. There are NO regulatory requirements (local or State) that dictate the pipe size/materials (eg. min. 8-in pvc w/ manholes).
We are tentatively recommending a 4-inch HDPE pipe system with clean-outs every 250-ft or so (based on local jetting limitations) using direct burial with screened material (the one-way trucking trip for imported gravel is over 1.5 hours). The heartburn I have is related to everyone's expectations for a traditional main-manhole system. Does anyone have any experience with using a 4-inch diameter pipe for long stretches for a hard-to-get-to location private application?
All comments are welcome. Thanks!
EG





RE: remote sewer service application
RE: remote sewer service application
Can you please provide some background? Seeing your emphasis is structural (per your name), do you oversize beams regardless of your calcs? That is how I am feeling about this pipe...
EG
RE: remote sewer service application
RE: remote sewer service application
RE: remote sewer service application
- An 8" pipe will not tend to freeze as quickly as a 4" pipe. If you're at a ski area, this may be something to consider, particularly with your low flows.
- You may find there is not a significant change in the overall increase in costs to go from a 4" to an 8" pipe. In my area, sanitary sewer mains are designed with 7'-9' of cover, and often the pipe material costs are a small part of the overall construction costs (i.e. material/construction specs of bedding/backfill and excavation depths have a bigger impact on overall construction costs).
- Without manholes, it will be more difficult to identify the location of the line to repair breaks/failures.
- Have you considered whether this system can easily be slip-lined (in the future) without manholes?
- I've designed service lines (4") that are a few hundred feet long, but they have cleanouts every 90'-100'. 250' seems to be pushing it.
- The idea of a grinder pump is definitely a feasible option, and may be less expensive if you do not have to bury it as deep (for frost-protection).
RE: remote sewer service application
RE: remote sewer service application
Steve
RE: remote sewer service application
Also, I just returned from a meeting with the local sewer maintenance company. They said the main difference between the 4" and 6" pipes are related to the type of equipment and cameras they use for maintenance and inspection. For a 6" pipe, the camera is tractor mounted and they can go about 300-ft (600-ft between manholes in theory) while you have to push the 4" pipe camera by hand and the range is about 100-ft. Also, for flushing/jetting, the equipment is far more mobile for a 4" than a 6" and they could transport the equipment for the 4" via snowmobile (using sleds) and snow cat much easier than the heavier equipment. Access for the 6" camera requires a manhole or enlarged cleanout with wide sweeps...
It seems that if you used the grinder pump system, you would have challenges related to the maintenance and your QC would not include visual, just air leakage testing...no?
77JXQ - Thank you for the connection! That is very helpful.
EG
RE: remote sewer service application
RE: remote sewer service application
I still say you price out an 8" main with 5 manholes compared to a 4" pipe with 14 cleanouts. I think you will find the price increase to be fairly low. And I'll guess that both of these systems will be more expensive than a small force main with a grinder pump.
If there is bedrock at 4' depth, this will be a bigger issue for a gravity system. Unless I'm missing something...
RE: remote sewer service application
If you don't like that idea, the grinder pump/force main. You might consider a way to introduce fresh water into the wet well, just to keep the solids moving from one end to the other in a day. Water should be plentiful around a ski resort.
RE: remote sewer service application
RE: remote sewer service application
Ben-While I agree with adding water to the system to prevent buildup...
Because of water rights, most ski resorts (here in Colorado) are limited in the amount of surface water they can capture and use.
RE: remote sewer service application
Richard A. Cornelius, P.E.
WWW.amlinereast.com