Storm pump station design

[washark]

About to design a storm-water detention pump station. Any helpful hints or suggestions about how to match pre-existing condition flow, maintenance of pump station, pump type, how to calculate emergency overflow weir, water quality for first flush or TSS traping eff....

We have a copy of the DOT's Highway Stormwater Pump Station design manual, and we are currently looking into a chopper pump (

http://www.chopperpumps.com)-

pretty cool pumps. We have a verbal "go-ahead" from the local municipalities now we need to finilize our design keeping in mind maintenance and erosion control.

We started our design sizing our pond with orifices to match the pre-developed flow to determine our pond size, but I know this is not accurate. I am thinking that I will need to compare the outfall pre hydrographs to the pump curves??? We are thinking of using storm filters to keep the grit and sand to a minimum.

To make thigs more complicated, we are adjacent to a wetland. Like all developers, we are trying to fit 10lbs into a 5lb bag and our site is in the lowcountry.

 

[DJF]

Check out SRS Crisafulli (

http://www.crisafulli.com).

We used one of their products in lieu of a "traditional" pumping station to eliminate flooding at our municipal building. Very cost effective solution.

 

[KRSServices]

One hint regarding storm filters, I have found that the simplest design also proved to be the most effective and least costly to maintain. The design revolved around a sump and outlet pipe set with a curved pipe placed below the invert elevation of the inlet pipe. Hmmm...I don't know whether that's understandable, but it proved to be very effective in not only removing harmfult grit and sands (settled in sump) but also floating debris. Vac Trucks were used to clean it when necessary. Just a thought, because the system installed prior involved a screen filter system with rakes. But that proved to be more of a maintenance headache than useful system after a period of years. It is just a thought as to what worked for us, it may not be practical in your case. KRS Services

http://www.krs-services.com

 

[cvg]

http://www.fcd.maricopa.gov/Resources/HydraulicsManual.asp

try the above site - Chapter 9.

You may also look at some of the work that has been done in New Orleans area (Jefferson Parish).

http://www.jeffparish.net/pages/index.cfm?DocID=1189

 

[gibfrog]

Check out the manual of practice at WEF.org, written in conjunction with the AICE.

Clifford H Laubstein
FL PE 58662

 

[Berko]

Watch out for Chopper pumps, they invariably block.

This usually happens at the most inopportune time (i.e during the storm when all the debris has flushed through the drains to the pump station.

Have you looked at Hidrostal pumps. We have used them on Stormwater duties & they work really well (they do not block)

 

[washark]

Berko -

Do you work for Hidrostal Pump? I noticed that your other posts to this site have all been praising towards Hidrostal. What do you mean by blocking? Why would this happen?

 

[Berko]

WASHARK

No I don't work for Hidrostal pumps, but having spent a number of years in the waste water industry dealing with other pump brands that block/rag when the manufacturers claim otherwise, Hidrostal is the only manufacturer (in my experience) whose pumps do not suffer with blockage problems.

You say that you are looking at Chopper pumps, so I am assuming that this is because you will be seeing debris, rags etc in the Storm Water.

Over in NZ & Australia (where I have worked over the years), many councils will not accept Chopper or Grinder pumps due to the maintenance implications owning one entails.

I have never come across a Chopper pump which can fully macerate all the debris found in sewage or storm water (you may prove me wrong). If a few rags hit the pump suction at the same time, the cutters can't cope & blocking ensues.

They are normally, hydraulically inefficient & once wear takes place in the cutters (you mentioned that some grit will be present), they will be very susceptable to blockages (as they cannot cut properly any more).

This is my experience, I would look forward to hearing other peoples views on this chopper pump subject

Regards,

Berko

 

[cvg]

Recommend that you try to screen out all debris upstream of the wet well. Therefore screen design and hydraulic capacity of the screen is essential. Design should assume some percentage of the screen is blocked and still maintain the design capacity through the unblocked area. Maintenance is also important to remove debris periodically. Grit and other small material that makes it through the screen should not be a problem with the pump if it is designed to pass solids.

 

[dicksewerrat]

Do you need an impeller pump? what's the head and volume?

 

[washark]

The outfall is 5' from the 8' deep wetwell and the volume in the pond (10yr event) is 73,000 ft^3. The discharge line from the pump to the wetlands is 6".

We arrived at this by the inflow hydrograph area above a max pump rate that is below the 10 yr storm. Two 5hp pumps in parrallel at this head is around 3.5 ft^3/s, which is also lower than the 2yr pre-developed rate. We currently have a submersible pump wetwell with two pumps.

 

[dicksewerrat]

Would a small axial flow pump work better? It would pass the tennis balls and pop cans.

 

[NicSacco]

In regards to your statement about filters, I think what you are looking for can be found on RPA Process Technologies web site.

http://www.rpaprocess.com

They have one filter called the AFR which is self cleaning and can filter down to 2micron. It also fits in a 3ft by 3ft square and can handle high flows.

 

[ace003]

Not sure where you are on your project but I noticed some negative comments on chopper pumps getting blocked. I work for a manufacturer of pump stations and we quite often use the Vaughan Chopper Pumps and I have never seen one get blocked. As a matter of fact they are bcoming the standard in several states. We have had trouble with others that claimed to be chopper pumps not working but the Vaughan units are extremely reliable. If you would like drop me an email and I will send you a solidworks CAD file of the design we use with the chopper pumps. I can also forward your name to Vaughan so that they could send you one of their videos and you can see that they are very serious about chopper pumps.

aemery@pumptech.com

ACE003