the affects to groundwater caused from sand mining

[codymack]

I'm reviewing a set of plans that's proposing a 400 acre sand mining pit excavating down to a depth of 50 to 60 feet below ground water. my question is, will this have cause a lowering of ground water on adjacent properties affecting neighboring wells, streams and environmentally sensative wetlands?

 

[LCruiser]

Most probably, especially with a size of 400 acres. You may also have an extremely difficult time just *getting* to a depth of 50 or 60 feet below groundwater, depending on the sand. Another big problem you may have is headcutting up the channel if an adequate drop structure is not built. What is the flow of the channel, or is it adjacent to a channel and not actually in it?

 

[fattdad]

If there is a clayey overburden and there is some sand and gravel resource at depth, there may be negligable affect on neighboring wetlands if they are supported by perched water directly recharged by rainfall only.

While the plans may call for up to 400 acres for total development, it is unlikely that all 400 acres will be dewatered at once. Chances are much more likely that there will be a system of cuts that may result in an acre of so of total disturbance at any given time. You'd want to get some idea on the extraction method to best evaluate the distance for influence to the water table.

Fundamentally, there will be some affect to the water table from the dewatering. The amount of this affect will depend on the transimssivity of the sand layer. I'd want to do some research on that before I got too worked up.

One thing to consider: Just because there are well users in the vicinity of the quarry, you need to find out whether the wells are using the water from the unconfined water-table aquifer. If it's like the Coastal Plain of Virginia, many of the wells go to the underlying confined aquifers, so even though there are wells in the "area of influence" these wells are not in the "area of influence" because they are in lower aquifers that are not in communication with the water table.

Hope this helps.

f-d

¡papá gordo ain’t no madre flaca!

 

[civilperson]

Probably no effect on neighboring water levels if the water level is left as is on the sand pit. Just pumping a cutter head dredge to mound up sand will leave the water basically unchanged.

 

[LCruiser]

What civilperson says is true - I was thinking you were dewatering. Sounds like a new pit in Irwindale or something (?)

 

[codymack]

yes this is a new pit and will not be excavated over any kind of flow channel. also the excavation is for silica sand and will occur over a 10 to 15 year period. thanks for the input