Submerged Outfall
Submerged Outfall
(OP)
I have discovered that several outfalls into a main Harbor were designed below Mean Low Water (several feet in some cases). This of course results in a completely submerged pipe outfall.
Is this a common practice in low areas? We do have problems with standing water but I'm surprised that there isn’t more. The design is from 1971 and was built as shown on the construction drawing.
Is this a common practice in low areas? We do have problems with standing water but I'm surprised that there isn’t more. The design is from 1971 and was built as shown on the construction drawing.
RE: Submerged Outfall
in order to gravity drain and maintain minimum cover over pipes, the outfalls often end up submerged.
your design may want to consider the tailwater level to be something higher than mean low water. How about mean high water plus a storm surge?
RE: Submerged Outfall
RE: Submerged Outfall
RE: Submerged Outfall
RE: Submerged Outfall
RE: Submerged Outfall
In our local tidal areas, we have frequently had a problem with some inlets flooding due to unusually high tides or storm surge. (This can really be a problem if it's salt water and asphalt pavement!) We have found some success with the installation of tide flaps at the outfall or at a large junction inlet just before the outfall. Just need to make sure that your system has enough head to ensure positive flow during a storm event, although the newer flaps don't need very much.
Good Luck
lsp_pe
RE: Submerged Outfall
flap gates are good is they can be maintained. it is more common for them to be forgotten and then get leaks rendering them pretty much useless. if they are in a location where it is difficult and costly to access there could be issues in the future.
secondly submerged outfalls are sometimes useful to disperse the fresh water from the cathment into the salt water of the harbour. it can look shocking in the harbour if there is a plume of fresh water (usually with suspended sediment) shooting out across the harbour.