Management of Stormwater at Cement Plant with Exposed Ash/Limestone Piles 2

[Steven Reed P.E.]

I have recently been looking into a project where an ash facility, where the limestone comes shipped in already wet, and also is exposed to precipitation. There was a stormwater collection "french drain" system installed a few years ago which, of course, already clogged, which was originally intended to manage stormwater. The sump pump forcemain is already clogged, which currently outlets to a evaporating pond. How do these systems typically handle water with such a high concentration of fine sediments without clogging? I was thinking about getting a grain-size distribution on the limestone to figure out the minimum velocity needed to prevent settling in the conveyance systems, and potentially adding sumps where needed which may need to be cleaned out almost daily. But I can't find any good guidance for what is typically done and I don't want to re-invent the wheel here. Does anyone know of how these types of systems are typically designed and if there is any type of design guidance out there?

 

[SlideRuleEra]

The coal storage piles at our electric generating stations seem similar to what you describe.

Coal storage area is sloped for surface drainage to flow into a dedicated pond (coal pile runoff pond) located immediately adjacent to the coal storage area. This dedicated pond allows most solids to precipitate out. Water is pumped from the dedicated pond to a larger "bottom ash pond" where the water can be treated before release. Solids in the coal pile runoff pond are routinely dug out and deposited in the bottom ash pond.

 

[Steven Reed P.E.]

SlideRuleEra: That's very interesting; do you have any schematics or drawings you can share? I don't know if they have room for something like that, but we might have to make it work. We need to come up with something because their current system is constantly clogging and flooding the site, causing sediment flow everywhere, and they might get shut down.

 

[Ekenny_G]

I think adding sump or forebays with baffles is a good start. Maintenance is usually an issue as you mentioned.

 

[SlideRuleEra]

Steven Reed P.E. - The best I can do is a satellite photo of the setup at one of our plants. The land is very flat, so the coal pile runoff pond is shallow, about 3 feet deep, as I recall. Since retiring, I see the company has stopped using the large bottom ash pond at the top-right and is now recovering bottom ash for sale as a byproduct. Note the scale of the photo at the bottom right.