3 Retention ponds in series 2

[jesspo]

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.

 

[TerryScan]

To fully understand your problem, it would be helpful to get some elevation data:
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?

 

[jesspo]

Well the elevation drawings are not readily available, so i'll make close estimations.
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.

 

[gbam]

jesspo - Additional questions:
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?

 

[jesspo]

Well I have all the documents at my disposal, but i haven't been able to glean what original intent was, although I assume they are more retention ponds in case of a spill, than detention ponds.

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.

 

[dicksewerrat]

Open all these valves. Clean the pipes with a jet truck. Then clean the pipe from Pond C to the creek. MY guess is they are all partially plugged. Is this creek 2 miles away? What is the surface elevation of the ponds when full?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[cvg]

your basins drain by gravity or by hydraulic gradient. In other words the water surface in your upper ponds must be above the water surface in the lower pond for flow to occur. Given time, all three ponds will equalize to the same water surface elevation unless valves are closed to separate them or the valve into the stream is opened to drain.

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.

 

[jesspo]

the pipes may be slightly plugged but that isn't the problem, and the creek is just under 2 miles away. The depth of all 3 ponds as of right now is pretty low because they desire ponds A and B to remain pretty dry, as in, they want them dry the day after a big rain.

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.

 

[cvg]

it realy depends on the desired pump flow rate and capacity of your existing drain whether 5 feet is high enough or if you need a pressure discharge line.

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

 

[dicksewerrat]

All these lines are nearly flat. The line to the crrek has about 8 feet of fall in 10,000 feet. that is a slope of .00076 feet per foot. For a plastic pipe, HDPE or PVC smooth interior you will get about 4 cfs max through the pipe. You will have to increase the diameter of the pipe to the creek or put in a pressure main to get anywhre near your 15 cfs. What is the volume of the ponds A and B. I would get the volumes, add them and figure out if 4 cfs will take the volume in one day. Otherwise A and B are not going to be dry in the one day.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[beej67]

This is a complicated issue that involves multiple reservoir hydrology. You need to establish what the required and intended design criteria for the system were, then delineate the watersheds and route the system for all applicable design cases. If you don't feel comfortable doing that yourself, consider hiring a hydrologist. If you come up with a 'solution' on your own without fully investigating its implications, you could very easily end up getting your client sued.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[jesspo]

Ok I have come to think that I'm incapable of describing the situation and problem we are having.

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?

 

[TerryScan]

jesspo,

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

 

[jesspo]

well The management wants the pond so the plant site "looks nice" SO basically it's purely aesthetics.

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.

 

[cvg]

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.

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

 

[jesspo]

why not CVG? I understand I'd have to open the butterfly valve for it to flow into C... but wouldn't raising the water column on the Pond B side of that culvert make it flow into pond C?

 

[cvg]

you can't raise the water surface level to the top of the riser without either a)shutting the valve and pumping water in or b) filling pond B. The way you have shown it you are pumping water out of B into the riser where it flows back into pond B and repeat...

 

[jesspo]

So when I turn on the pump and open the valve, wouldn't it flow into C because it would have to be a higher level to overflow the riser?

 

[cvg]

you would need a check valve or better yet, just put the riser on the correct side and leave the valve closed

 

[jesspo]

If I put the riser on the Pond C side of the culvert, i would need to pressurize the entire line from B to C, which is a 12 inch culvert?

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.