20220525_ADI_Received

CAROLINA GEOLOGICAL SERVICES, INC
RECEIVED
April 21, 2022
MAY 2 5 2011
Mr. Adam Parr
NCDEQ LAND QUALITY
1612 Mail Service Center MINING PROGRAM
Raleigh, NC 27699-1612
Subject: Modification Thomas Borrow Pit, Permit # 16-83, ADI response
Dear Mr. Parr;
On behalf of Ralph Thomas, I am writing in response to your March 25, 2022 letter
requesting additional information on the above -referenced mining permit modification
application.
As you know from the proposed plan, water is to be pumped from the mining area into the
existing pond. The pond itself is a former sand pit with an earthen dam and spillway on the end
adjacent to the wetlands. It has been observed that the pond itself is slightly higher in elevation
than the mining area, and the soil comprising the banks of the pond are very sandy and will
readily absorb a large quantity of water. The dam and spillway serve to increase the amount of
water that can be retained by the pond, therefore the natural static water level in the pond is
several feet below the spillway outlet elevation.
In an effort to better understand to natural hydrology of the soils and the pond, and in
response to your questions, a series of observations were made on the pond. First the pond
was pumped down very low, discharging into the agricultural ditches. Then, water was pumped
back into the pond (from the ditches), at a rate that is expected to be similar to the proposed
mining activity. It is anticipated that the mine will run the pump 12 hours per day (likely
overnight), pumping 324,000 gallons per day. Once the pond was full, pumping stopped, and
the water level was measured to determine the rate of absorption. Based on the volume of
water measured by the fall in 24 hours, it was shown that the absorption rate of the pond is
approximately 150,000 gallons in 24 hours. To further observe a range of natural conditions, we
observed the pond levels during significant rain events. It was observed that the pond level
fluctuations did not appreciably change.
Therefore, in specific response to your letter:
1. During normal operations of the mine, it is anticipated that the mine will pump 324,000
gallons per day into the existing receiving pond. It has been determined that the pond will
absorb approximately 150,000 gallons into the soil. Therefore, the pond will crest and discharge
approximately 174,000 gallons per day into the adjacent freshwater wetlands. We are currently
considering raising the crest elevation of the discharge inlet by 3-4 inches, thus significantly
increasing the volume that can be absorbed before discharge. It is important to note that the
wetlands area is a 100 acre Freshwater Forested / Shrub habitat wetland, specifically a
Palustrine System, which is defined as nontidal wetlands dominated by trees, shrubs, persistent
emergents, emergent mosses or lichens. Any discharge of freshwater into the freshwater
wetlands will serve to add to the beneficial hydration of the wetland.
PO Box 429, GARNER, NC 27529

Page 2
Mr. Adam Parr
2. See above discussion on the observations and measurements of the quantity of water that
the pond has shown to absorb. Also note that the natural groundwater on this site is naturally
"high" year-round, with very little fluctuation. Since the elevation of the pond is higher than the
mining area, it serves as a buffer to any fluctuations in the water table.
3. As required in the NPDES application, alternatives for discharge were considered. There
are no local sewer systems that can feasibly accept the discharged water. With the relatively
high natural water table, it would not be feasible or environmentally sound to consider injection
wells. All of the surrounding property is relatively flat agricultural land (also with a high water
table), so any spray irrigation would pond onsite, damage the agricultural use, and likely flow
immediately back into the pit.
We trust that this information will allow you to complete your review of this modification
request. Please let me know if you need any additional information.
Sincerely,
James Izzell
Carolina Geological Services, Inc.