3 Retention ponds in series
3 Retention ponds in series
(OP)
Ok, this might be a retarded question because well, I like dealing with refineries, not ponds.
In the sketch I've provided there shows a series of 3 ponds. Ponds A and B are slightly above pond C. They all currently drain by gravity, there are butterfly valves between B and C and on the outlet of C which goes to the stream.
The Structure in the upper right is what our current discharge culverts look like 24" Plastic with a grate that feed 8" plastic pipe which drains to the next pond/stream.
THE PROBLEM: Pond C must be almost completely drained before we are able to get A&B to flow into it. Once A/B drain into C the level is too low. So without redoing the entire grading/piping, is there a way in which we could get A/B to flow into C while the level is higher.
PROPOSED SOLUTION: I suggested we put a sump pump near the exit of B which is piped directly into the 24" Plastic pipe and close the openings so the pressure from pump could over come the back pressure. Would this be ok? Obviously the Openings at the bottom of the drain would need to be closed, so the back flow isn't faster than the pump.
I realize i've probably left out some important details, please just inform me what else we need to know before we can come to a solution.
Thank you.
In the sketch I've provided there shows a series of 3 ponds. Ponds A and B are slightly above pond C. They all currently drain by gravity, there are butterfly valves between B and C and on the outlet of C which goes to the stream.
The Structure in the upper right is what our current discharge culverts look like 24" Plastic with a grate that feed 8" plastic pipe which drains to the next pond/stream.
THE PROBLEM: Pond C must be almost completely drained before we are able to get A&B to flow into it. Once A/B drain into C the level is too low. So without redoing the entire grading/piping, is there a way in which we could get A/B to flow into C while the level is higher.
PROPOSED SOLUTION: I suggested we put a sump pump near the exit of B which is piped directly into the 24" Plastic pipe and close the openings so the pressure from pump could over come the back pressure. Would this be ok? Obviously the Openings at the bottom of the drain would need to be closed, so the back flow isn't faster than the pump.
I realize i've probably left out some important details, please just inform me what else we need to know before we can come to a solution.
Thank you.





RE: 3 Retention ponds in series
Bottom of each pond
Desired "no flow" pool levels for each pond
Maximum water elevation for each pond
Stream elevation
Also, what are the flow rates you are dealing with during flow?
RE: 3 Retention ponds in series
Creek is Elev 0
Pond C is Elev +8 ft
Pond B is Elev +8.5 ft
Pond A is Elev +9 ft
They desire pond A and B to remain empty most of the time, apparently they hate cattails and want to avoid them growing
Maximum water elevation for A and B are about 4 ft while C is closer to 6 ft
Flow rates are only what is collected in the ponds during rain events, they are not used for anything but site drainage.
RE: 3 Retention ponds in series
Have you researched the original design/report?
What was the original intent of these ponds?
Are these ponds ment to be retention or detention?
What is your maximum allowable discharge to the stream?
RE: 3 Retention ponds in series
I think maximum allowable discharge is around 15 cfs, or that's the number i keep seeing. It's a smaller stream but that number still seems really small.
updates on elevations from site work drawings.
Pond A is A 849.5
Pond B is also 849.5 There is a ditch that drains into this pond from 850.65
Outlet of the TWELVE in culvert from B into C is at 849.08 and the outlet of Pond c is 848.93
I wasn't able to find the creek elevation but it's like 2 miles through 18 in culvert and a steady grade.
So looking at those, maybe they are simply meant to be kept empty? I guess I'll have to do more digging into how the ponds were originally intended to be used.
RE: 3 Retention ponds in series
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: 3 Retention ponds in series
You could separate a and b from c by permanently closing the valves and then pump the water from a and b into c as desired. i would recommend a separate discharge line rather than pumping into an existing HDPE gravity line. the gravity lines are not meant to be pressurized. Alternatively, deepen basin c and put the pump in basin c to discharge to the river.
RE: 3 Retention ponds in series
I get that currently they drain by gravity. Is a pump and line cheaper than just a pump to the existing HDPE gravity line? Obviously cost is a factor or i would just tell them to Dig pond C deeper, but they want to avoid a 30k USD project and may not even be willing to spend 10k.
So will a 5 ft riser in pond B and pump into the base of it work with existing culverts? I feel like i could then keep pond C deeper than current levels and wouldn't spend more than 5k.
RE: 3 Retention ponds in series
Gravity flow will work if you limit your pumping rate. build your riser just high enough to provide the head you need to:
a)overcome friction in the HDPE line
b)fill basin C to the top
RE: 3 Retention ponds in series
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: 3 Retention ponds in series
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: 3 Retention ponds in series
1) the creek drainage works as intended
2) The problem is keeping the level in pond C up while keeping Ponds A&B down.
I have attached another wonderful sketch to illustrate my proposed solution. Will this work in a general sense? as of right now the culvert is simply an opening.
And our current SOP to drain pond B is to allow pond C to drain almost completely, then shut off flow to the creek and open the butterfly between B&C and until B is nearly dry.
So will a sump pump and closed culvert work?
RE: 3 Retention ponds in series
If it is desirable for A & B to be dry, why is one wanting C to be wet ("keeping C up")?
If one wants these ponds to drain, why would one ever close the valves? If you just leave the valves open, they will all drain.
I would have to agree that you are having difficulty properly
RE: 3 Retention ponds in series
I am going to pose the question if it's worth any money to keep Pond C with sufficient level in it. or if we should just leave them all empty all the time. Because that is the easiest answer.
RE: 3 Retention ponds in series
your sketch shows the riser on the upstream side of the BV. this will not work, you need to put it on the downstream side
RE: 3 Retention ponds in series
RE: 3 Retention ponds in series
RE: 3 Retention ponds in series
RE: 3 Retention ponds in series
RE: 3 Retention ponds in series
I don't understand why my solution is that bad? I would only need a 2 inch line to the bottom of the riser, when I turn the pump on some would flow into c and perhaps some would overflow the riser, but I think it would mainly flow from B to C, without a check valve.
Of course once the level of C is higher than the riser it would flow backwards, but I intend to make the riser a good deal(3ft) Higher than what C can hold.
RE: 3 Retention ponds in series
RE: 3 Retention ponds in series
jesspo - it would be a lot simpler and less maintenance and problems to simply over excavate Pond C below the outlet elevation in order to acheive a pool for asthetics. Then, let everything equalize and drain by gravity.
RE: 3 Retention ponds in series
How is the riser closed off to pond B EXCEPT by pump inlet, not going to work? You say Ponds B&C will equalize if i leave the valve open, so if Pond C is connected to that riser drawn, with the only outlet the top and i pump water into the bottom, won't that work as well?
RE: 3 Retention ponds in series
RE: 3 Retention ponds in series
Gbam, are you saying the setup would work? I understand that there are alternative solutions, but i was told low cost, and easy installation/maintenance.
I have come to the conclusion that it will work, although not as well as excavation or just burying a dedicated line for a pump.
RE: 3 Retention ponds in series
RE: 3 Retention ponds in series
I think you still need to look at the Pump cost, initial dewatering and O&M costs for the pump alternative and compare that to the excavation alternative to find the most cost effective alternative. Simulate wet and dry cycles with your pump alternative to see if there is increased costs during certain times of the year. What is the ground water level and will these ponds continue to fill during the dry times?
Also make sure that you can continuously discharge to the stream with out fines etc...
RE: 3 Retention ponds in series
You mentioned a max allowable flow rate which suggests you have a permit for these ponds and their discharge. If you have a permit you want to find out if any of the ponds are allowed by permit to retain water beyond 48-72 hours after rainfall. If there are detention ponds then they are probably meant to be dry except with rain fall. If they are permitted as such you need to be sure you will not be in violation of your permit before you start keeping water in any of the ponds beyond the permitted time.
Just a thought.