20080868 Ver 2_Staff Comments_20081103

PCS and Groundwater monitoring
Prepared by DWQ staff for PCS consideration
November 3, 2008
Version 1.0
The 401 Certification rules (15A NCAC 2H .0506(b)(3) and (c)(3) require that the
401 Certification process only certify projects if the project "does not result in the
degradation of groundwaters...". DWQ staff believe that the best approach for PCS to
follow is to supplement the existing groundwater monitoring that is being done on the
PCS tract in order to address this 401 requirement with respect to the degradation of
groundwater standards. Wetland staff have consulted with staff of the Division of Water
Resources, Waste Management Branch and Aquifer Protection Section in the
Washington Regional Office in order to determine what existing groundwater monitoring
is being done in order to supplement that existing work.
Existing monitoring includes monitoring of 21 wells in association with the
Recycle System at PCS for chloride, sulfates, total P, TDS, pH, water level, Na, Total
Organic Carbon (TOC) and annually for heavy metals (including Cd and FI) and Volatile
Organic Carbon (VOC) (Permit Number W000001105). In addition, the Division of
Water Resources requires groundwater monitoring mostly for water quantity for the
Capacity Use Permit using a series of wells at the periphery of the mine. Finally, the
Hazardous Waste Section of DHHS has some responsibility for groundwater monitoring
as well in and near the PCS site.
The 401 Certification involves approval for the mining of wetlands and streams
and therefore any groundwater degradation must relate to that mining. In that context, it
would probably be necessary for PCS to report all the groundwater monitoring data to
DWQ Wetland staff for review on an annual basis in a format designed to readily
determine if groundwater standards are being protected. In addition, monthly sampling
of the dewatering water as the mine advances for the constituents outlined in the
Recycle System permit (with the addition of total Nitrogen) would be appropriate.
Alternatively instead of monitoring the dewatering wells, PCS could establish monitoring
wells at the periphery of the mining area as the mining area advances in order to
examine any possible groundwater degradation due to the mining operation. In addition,
PCS would need to make certain that sufficient data exist on pre-mine areas in order to
establish an undisturbed baseline. Finally, heavy metals and VOC should be sampled
annually with the exception of monthly sampling of Cd and FI which are known to be
present at times in the discharge from PCS. This general approach to groundwater
monitoring would supplement the existing data being collected and allow DWQ to assure
that groundwater degradation was not occurring.
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