Quarry Drainage

I'm a curious sort of guy. I'm wondering if anyone can explain what goes into keeping an active Quarry dry. I know there is a pump, many times a deep lagoon, and related piping but how exactly does the Quarry keep the pit from filling up? And where are the pipes that take the water out-burried? And as the Quarry goes deeper, does personel have to rearrange the piping. I suppose a related issue is how the pipes are protected from the constant rumblings of shots.

Conversely, when a Quarry is abandoned, and the pumps are turned off, the Quarry generally floods. I have always thought of these pits as giant bath tubs. Yet, I've never seen a locality where the water has overflowed the lip so to speak. Rivers and lakes flood. Do some of these giant pits ever flood the surrounding area? Is there any magic in keeping the generally huge volume of water contained?

Those are all the questions I have.

You might get some surface runoff into the pits, but the main problems arrive when the bottom of the pit ends up below the water table. You can keep things more or less dry if you have wells that can pump enough water to create a "cone of depression (of the water table)" below the floor of the pit.

While mining in areas below the local water table we always planned ahead and shot in and dug a sump equipped with pump(s) to keep the water below the working floor.If we were in an area where we expected differing amounts of water inflow ,which is usually a seasonal thing we had as many as 5 to 6 pumps .We would run the pump or pumps as needed . The foregoing was calculated using projected rainfall amounts,rock porosity/permeability and quarry surface area where possible.This pumping had to be permitted in the U.S. to allow water to be discharged into a catch basin or stream and the water quality was constantly monitored where water flowed into a natural stream.
At various times we would get so much water that a lower level would be temporarily flooded but we offset this by developing several benches where possible,otherwise we had to upgrade pumping capacity.
When a quarry is shut down that was opened below the water table , the quarry fills again and will stop at the local water table so will be filled only partially.The final water level will be the local water table.



Edited 1 time(s). Last edit at 11/08/2009 09:25PM by Milton Dye.

Sometime the pumps can't keep up with the water. On our recent trip to the syenite quarries in Arkansas, the lower levels of all the quarries were flooded. They had over 20 inches of rain in the area preceding our visit. The haul trucks don't have much trouble, but we were reluctant to venture into the shallower areas since we couldn't see hidden rocks! Made for an interesting trip.

Henry Barwood
Troy University
Troy, Alabama USA

Thank you Milton. That addresses some of the questions I had, especially why a pit will fill to only a certain level. I'm still not straight on where all the plumbing is located and how the water is carried out to wherever it is being discharged. The installation of subterannean piping seems as massive an undertaking as quarrying itself. I understand how my basement is drained-the water gathers in the sump and then is pumped through a pipe out onto my driveway where it runs downhill into a sewer. Generally speaking, is there a pipe that runs from a Quarry's lagoon to the river or other body of water where it is discharged? Or does the lagoon have some other function?

I know in 17th and 18th century mining, an adit or tunnel was drilled to drain the areas being mined. I don't think it's that simple in the case of a quarry. And when a Quarry is abandoned, I recognize that the pumps are turned off, but is the associated piping blocked in some fashion to prevent further discharge or does the very fact of the pump's inoperation render the piping useless and of no concern?

David,most of the operations that I worked with had to move the main sump from time to time this being due to quarry advance and deepening. Due to this the piping from the pump was simply run up the quarry wall in a temporary fashion and into the basin or stream pumped to.I have only seen one quarry where piping was actually placed below ground or in rock that had been drilled for this purpose.This operation was a very old quarry that had the sump developed deep enough and had large amounts of water to pump.Drilling in rock in order to place piping is very expensive so if this is done it is expected the sump is deep enough and that there are enough reserves to mine for some time before the stone reserves are depleted or the pump will be moved.
As a quarry is developed the sump,pump(s) and piping are moved to allow for advance where necessary.Many times when a quarry becomes inactive and has pumped water the pump is removed and the piping that is easily reached is removed.Once the pump has been removed the piping no longer is used and is not blocked simply because the lack of a pump renders the piping useless.
There are many operations that do not have a pump but allow gravity to move water from the working face to levels lower than the quarry but that is another story!