Need to filter and collect water from a muddy stream - 50 gpm

[ddsgeotech]

We need to pull 50 gpm out of a stream for seal water for a pump on a short duration (3 year) project. There is no other realistic water source near our pump. The problem is sometimes the water in the stream is fairly dirty with suspended solids due to some disturbance upstream. My plan is to excavate adjacent to the stream and install a perforated manhole surrounded by sand and gravel to filter the water. I need to make sure 50 gpm will travel through this sand and gravel. I used Darcy's law and I also used the formula for a single well near a line source from UFC Dewatering and Groundwater Control (

http://www.wbdg.org/ccb/DOD/UFC/ufc_3_220_05.pdf).

Both methods show that we should be able to get 50 gpm with about 4' of drawdown. I did a quick check of flow through the orifices of an available seepage manhole and that does not appear to be the limiting factor. I can't really check filtration because I don't know what the qualit of the water in the stream is, and I don't really have a maximum allowable for the seal water use. I'm just figuring that sand will filter it sufficiently. Any thoughts on other ways to analyze or check?

Thanks for any ideas.

 

[bimr]

Have you considered using multiple wellpoints? One would think multiple wellpoints will be less expensive as well as more reliable. Wellpoints will also provide a better quality water.

You will need a filter for the water as the water will contain suspended solids.

You should also investigate the permitting requirements prior to construction. Permits will be required.

 

[dicksewerrat]

Call well drilling company that understans the local soils. Hve them design the sand filter. You may need a layer of gravel, then a layer of sand and a well screen.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[dik]

Check with Palo Alto Research and centrifugal/centrifical water purification... intended for third world dudes...

Dik

 

[MEM1]

I have seen these used at cattle feedyards in an effort to keep nozzles on center pivots from plugging. Probably a lot bigger than what you need, but might be worth looking at.

http://riverscreen.com/

 

[bimr]

Shore wells also known as infiltration galleries are shallow wells influenced by surface water and are installed near a waterbody in a shallow aquifer that is directly connected to surface water. Shore wells can also be shallow subsurface devices adjacent to a water body, installed to collect water through a covered stone-filled trench or similar arrangement that drains surface water to a storage well or tank. Soils surrounding shore wells provide minimal filtration. The risk of contamination of these water sources can be similar to those of surface water sources.

Here are a couple more options.

You can direct filter the river water. Use a strainer to protect the pump and a set of filters in series. The first filter is a roughing filter and should be operated at a low throughput of 2 gpm/sq ft. The second filter is a polishing filter and may be operated at a high throughput of 6 gpm/sq ft. This option is probably the least expensive.

The second option is to directionally drill under the river. Most wells are vertical shafts, but they can also be horizontal or at an inclined angle. Horizontal wells are commonly used in bank filtration, where surface water is extracted via recharge through river bed sediments into horizontal wells located underneath or next to a stream.