adjustable stand pipes / low flow pipes - detention pond
adjustable stand pipes / low flow pipes - detention pond
(OP)
i oringally posted this under the general forum but it may get more hits here..........thanks
a local municipality has requested that we design an adjustable stand pipe for an existing detention pond. the stand pipe would act as a low flow pipe in order to recharge a downstream detention pond. since the site is not developed yet and relatively large, the stand pipe needs to be adjustable (i.e. standpipe's inlet would need to be raised in the future such that the head would be reduced). anyone have any experience with tsomething like this or recommend a typical detail to start out with? (don't want to reinvent the wheel). the calcs will be a challenge since we need to accomdate this flow in the pipe to the pond's release rate...but trying to start with a detail
first response by slideruleera:
The standpipe material, diameter and unsupported length (intitial & final) will have a lot to do with the detail. Have you make any decisions on these factors? Also, does the standpipe need to have variable length, or would a few discrete steps be acceptable?
zzmarkzz (Civil/Environme) Oct 5, 2004
the low flow pipe would likely consist of 6" diameter PVC, the stand pipe would be 6" PVC with a 2" restrictor inside of it. we would need standpipe to have a variable length....currently the site is undeveloped so the standpipe would be relatively short (±0-1' high). once the site is developed, there will be more flow into the ponds and the elevation of the standpipe will need to be increased (±2-4' high) in order to decrease the flow of the low flow pipe (by lowering head). again, its a unique design requested by the municipality and their thought is that this low flow pipe will recharge an existing downstream retention pond which has recently dried up.
a local municipality has requested that we design an adjustable stand pipe for an existing detention pond. the stand pipe would act as a low flow pipe in order to recharge a downstream detention pond. since the site is not developed yet and relatively large, the stand pipe needs to be adjustable (i.e. standpipe's inlet would need to be raised in the future such that the head would be reduced). anyone have any experience with tsomething like this or recommend a typical detail to start out with? (don't want to reinvent the wheel). the calcs will be a challenge since we need to accomdate this flow in the pipe to the pond's release rate...but trying to start with a detail
first response by slideruleera:
The standpipe material, diameter and unsupported length (intitial & final) will have a lot to do with the detail. Have you make any decisions on these factors? Also, does the standpipe need to have variable length, or would a few discrete steps be acceptable?
zzmarkzz (Civil/Environme) Oct 5, 2004
the low flow pipe would likely consist of 6" diameter PVC, the stand pipe would be 6" PVC with a 2" restrictor inside of it. we would need standpipe to have a variable length....currently the site is undeveloped so the standpipe would be relatively short (±0-1' high). once the site is developed, there will be more flow into the ponds and the elevation of the standpipe will need to be increased (±2-4' high) in order to decrease the flow of the low flow pipe (by lowering head). again, its a unique design requested by the municipality and their thought is that this low flow pipe will recharge an existing downstream retention pond which has recently dried up.





RE: adjustable stand pipes / low flow pipes - detention pond
I've seen something similar here with a weir gate that would be raised and lowered throughout the year in order to control the water level in the pond. Something similar should work for you since you could just raise the "weir" as required instead of trying to adjust a standpipe.
David
RE: adjustable stand pipes / low flow pipes - detention pond
the adjustable weir is a good option, however, the municiaplity wouldn't likely allow it (concrete lined weirs are required)
RE: adjustable stand pipes / low flow pipes - detention pond
1. Construct the standpipe full heigth but put a 6" PVC union in the horizontal line, just before the 90 deg. elbow to the standpipe.
2. Then you could rotate the standpipe (roll it over to one side) to make the vertical height component any value desired.
3. When your project is fully developed, the stand pipe would be positioned "permanently" vertical.
Six inch PVC unions appear to be available, here is a link to a typical source:
http://12.107.25.236/smcweb/eINM022.pgm?Book=80-1&...
RE: adjustable stand pipes / low flow pipes - detention pond
RE: adjustable stand pipes / low flow pipes - detention pond
RE: adjustable stand pipes / low flow pipes - detention pond
RE: adjustable stand pipes / low flow pipes - detention pond
RE: adjustable stand pipes / low flow pipes - detention pond
http://www.dep.state.pa.us/dep/deputate/watermgt/w...
on pages 43-44 describes methods to size orifices on a Basin Skimmer. Note it is intended to be a temporary E&S control design, but with some affordable peripherals (guide rails, etc.), it could possibly be made permanent. Use a smaller orifce during initial conditions. Later, pull it in from the bank by hand, and using hand tools, drill a bigger orifice.
Use care, the Skimmer is PVC which is notorious for embrittlement after prolonged sunlight exposure.
RE: adjustable stand pipes / low flow pipes - detention pond
Because you are considering a 6" PVC with a 2" orifice I would recommend just installing a ditch inlet catch basin with a mounting for a steel plate with an orifice cut into it over the outlet pipe. Then you could replace the steel plate with one with a smaller orifice anytime you wanted.
David
RE: adjustable stand pipes / low flow pipes - detention pond
how the 2" pipe in standpipe will really work without getting easily clogged, that's the challenging design i'm trying to come up with (i.e. a 2" pipe with a couple 90 degree bends coming out of the 6" standpipe and likely having to drain the pond in the future (or union idea) to raise the stand pipe??)
RE: adjustable stand pipes / low flow pipes - detention pond
RE: adjustable stand pipes / low flow pipes - detention pond
RE: adjustable stand pipes / low flow pipes - detention pond
This design addresses clogging by positioning the orifices on a downturned elbow. Floatables/oil/grease can collect above the orifice, and a sump collects grit.
Orifices provide tighter flow control (for more a greater range of events) than a weir, but a weir can usually handle high flow rates with less head.
http://www.wsdot.wa.gov/EESC/Design/designstandard...
RE: adjustable stand pipes / low flow pipes - detention pond