NCG020089 H1 East Exceedance Letter 20240318

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VIRONMENTAL
March 18, 2024
N.C. Department of Environmental Quality
Division of Water Resources
Attn: NC DEQ Mooresville Regional Office
610 East Center Avenue, Suite 301
Mooresville, NC 28115
Re: Imerys Mica Kings Mountain
NCG 020089
H1 East Tier 2 Response
To Whom It May Concern:
Analytical sample results for the first sampling period of 2024 at the H1 East stormwater outfall
potentially exceeded a benchmark value for turbidity and total suspended solids (TSS). The
laboratory result for turbidity was 450 NTU and the permit references a stream and surface
water turbidity benchmark of 50 NTU in section F-5. The laboratory result for TSS was 195
mg/L and the permit references a benchmark of 100 mg/L in Section F-2. The outfall is located
near the Northern boundary of the mine adjacent to Dixon Dairy Road. The outfall flows from
the culvert at the outfall, under Dixon Dairy Road and to the roadside ditch, which then flows
generally West through a field and private property, before reaching the nearest receiving water
which is an unnamed tributary to Long Branch. The flow path from the outfall to the nearest
receiving water is approximately 2,560 feet. The unnamed tributary is located on private
property and Atlas has attempted to contact the property owner for access with no response.
Due to the receiving water being located on private property, and not having landowner
permission, it is not possible to collect samples upstream and downstream to demonstrate no
rise in turbidity of the receiving water. However, due to the long flow path before reaching the
nearest unnamed tributary, Atlas believes it is unlikely that the rain event resulted in an increase
of turbidity in the receiving water. This exceedance does mark two consecutive exceedances at
the H1 East outfall and has resulted in a Tier 2 response.
Details:
Mine: Moss
Site: H1
Outfall: H1 East
Sample Type: Stormwater
Sample Date: March 06, 2024
Lab Results Date: March 08, 2024
General Timeline:
Continuously: Exceedance has been documented in SWPPP.
Within 2 Weeks: Notify NC DEQ Regional Office in writing (This letter: March 18, 2024).
Conduct inspection (By March 22, 2024).
Within 1 Month: Select course of action by April 08, 2024.
Within 2 Months: Implement selected feasible action by May 08, 2024.
Begin monthly monitoring after implementing action.
ATLAS Environmental, Inc.
338 S.Sharon Amity Road #411 Charlotte, North Carolina 28211
704-512-1206(o)/828-712-9205(m)
www.atlasenvi.com/Offices in Asheville and Charlotte

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I.ONMENTAL
Cause of Exceedance:
The cause of the exceedance is unknown however it has been attributed to runoff from the
stockpile area and the intensity of the rainfall event. The material consists of fine non-cohesive
sediment which does not rapidly settle. The basin associated with outfall H1 East appeared to
be in good condition and no maintenance or repairs were identified.
Remedial Action Plan:
The remedial action plan includes removal of the H1 East outfall by modification of the mine
permit. The ground surface will be graded so that all surface water sheet flows into the existing
mine pit. The water will then be pumped from the pit to a settling basin before gravity flowing
into the H1 West basin. Atlas and Imerys have been coordinating with State Mining Engineer
Adam Parr regarding the outfall removal and it is planned that Atlas will submit the mine permit
modification in June or July 2024.
Please let me know if you have any questions.
Best regards,
ieetkqe^dRidet.
Jennifer L Robertson, President
ATLAS Environmental, Inc.
338 S.Sharon Amity Road #411 Charlotte, North Carolina 28211
704-512-1206(o)/828-712-9205(m)
www.atlasenvi.com/Offices in Asheville and Charlotte