20230503_Pumping_OM

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Pumping Operation
and Monitoring Plan
Firetower Road Sand Mine
Certificate of Coverage
NCG020***
Sunland Sand and Gravel
Fire Tower Road
Onslow County, NC
April 20, 2023
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This PUMPING OPERATION AND MONITORING PLAN was prepared in
accordance with the requirements specified in the National Pollutant Discharge
Elimination System (NPDES) General Permit for Mining (NCG020), and specifically
as applied in the Certificate of Coverage for this location:
Firetower Road Sand Mine
Certificate of Coverage
NCG020***
Sunland Sand and Gravel
Fire Tower Road
Onslow County, NC
April 20, 2023
This plan is designed to satisfy the requirements of Part G, Section b of the
NPDES General Permit NCG0200.

Background:
The NPDES General Stormwater Permit for Mining (NCG020000) addresses
impacts of mine dewatering wastewater pumping and discharge on surrounding areas,
including potential impacts to wetlands. The NPDES Permit requires that the mine have
a site specific plan for, 1) groundwater monitoring strategies to demonstrate the effect of
pumping and establish any pumping regime necessary to reduce potential impacts to
surrounding areas, and 2) detailed plans to maintain surrounding hydrology and
respective monitoring to demonstrate compliance.
In order to develop these plans, detailed studies must be done to understand the
site-specific parameters. First, any wetlands that may be potentially impacted must be
delineated according to US Army Corps of Engineers criteria. Second, a study of
potential impacts of groundwater levels must be conducted. This should include a
detailed examination of soil types, permeability, and various zones of groundwater within
the zone of influence. Third, based on the groundwater data, an assessment of potential
impacts to the wetlands by mine dewatering should be estimated. Finally, based on the
potential impact, a plan should be developed to limit as well as monitor the potential
impacts to the wetlands.
Site description:
The Firetower Road Sand Mine is located on Fire Tower Road, Onslow County,
NC It is located within the White Oak River Basin. The mine excavation will eventually
encompass 28 acres. Natural groundwater levels within the sand mine are within 5 feet
of the surface. The sand deposit being mined is an alluvial deposit consisting of
sediments, ranging from a silty fine to medium grained sand. The excavation will be
reclaimed as a pond. The Mine Plan as submitted for the Mining Permit Application is
attached.
Wetland description:
The wetlands adjacent to the Firetower Road Sand Mine were delineated in
November 2022 by Mr. John C Roberts, a NC Licensed Soil Scientist. This delineation
was reviewed and approved by Mr. Thomas Charles, of the US Army Corps of
Engineers. Natural hydration of the wetlands is accomplished by occasional flooding of
the low elevations, as well as natural surface drainage from rainfall. The wetland soils
differ from the upland soils by a dense clay/silt layer that tends to allow the surface water
to "pond" near the surface. It also restricts transmission of water vertically.

Pumping and mine dewatering:
This sand deposit is typical of other deposits in this area. The groundwater table
is several feet below the original ground surface, but above the total depth of the
excavation. Therefore, some groundwater is occasionally pumped from the mining area.
Goundwater and stormwater will be collected within a large sump area in the mined
area. The dewatering pump intake floats on the surface of the collected water,
preventing any sediment from leaving the mining area. Water is then pumped to the
adjacent 30 feet by 60 feet basin before being discharged into an existing drainage ditch.
Based on the volume of the pump and projected water levels, it is anticipated that a
maximum of 300,000 gallons per day maximum will be pumped from the pit.
Impact of dewatering on adjacent wetlands:
Based on the soil borings and investigations, the soils within the wetlands and
the soils in the mining area are very different. A dense and virtually impermeable clay
layer underlies the hydric soils within the wetlands, while soils in the sand mining area
consists of very permeable sand. The impermeable clay in the wetlands holds the near-
surface water in a concave "perched" condition, thereby supporting the wetland
vegetation and hydrology. This observation is supported by the remarkable difference in
the existing groundwater levels in the two areas. The "perched" water table in the
wetland areas is within 6 inches from the surface, while groundwater levels in the mining
areas are over 5 feet. Therefore, there appears to be no connection between the
groundwater in the sand mine and the near-surface groundwater that provides hydration
to the wetlands. The hydration of the wetlands is accomplished by surface water,
rainwater runoff, and occasional flooding of the wetland area, and not from the deeper
groundwater found in the sand mine. Therefore, the mine dewatering will have no
impact on adjacent wetlands. In addition, the water that is pumped from the mining area
will discharge into an existing drainage ditch. Since the ditch is adjacent to part of the
surrounding wetlands, the dewatering activity will actually enhance the wetland
environment, providing hydration even during dry periods.
Monitoring:
Based on the observed disconnection between the water within the mining area
and the surrounding wetlands, it is anticipated that any potential dewatering at this mine
will have no impact on the adjacent wetlands. In order to confirm that there are no
impact to the wetlands, a monitoring plan should be established as a precaution.
1. Mine dewatering wastewater discharges should be quantitatively and qualitatively
monitored according to requirements of the NPDES permit. See the "Monitoring
Requirements" in the Stormwater Pollution Prevention Plan.
2. The Discharge Point should be examined weekly to make sure that it is functioning as
designed and that no sediment has discharged into the ditch or adjacent wetlands.

3. A written record shall be kept of pumping times and rates. A record of rainfall shall
also be kept in the Stormwater Pollution Prevention Plan.
5. The wetland vegetation in the area between the pond and the mining area should be
inspected at least quarterly. If any vegetation appears to be distressed, an investigation
should be conducted to determine the cause.