NPDES Permit update—what you should know

NPDES Permit update—what you should know

The South Carolina Department of Health and Environmental Control (SC DHEC) recently issued an updated version of the National Pollutant Discharge Elimination System (NPDES) General Permit for Discharges Associated with Nonmetal Mineral Mining Facilities. Several noteworthy revisions were included.

The updated permit applies to facilities that mine the following: sand, gravel, clay, fill dirt, kaolin, vermiculite, dimension stone, and/or crushed stone. They are mines that may discharge water as a result of mine dewatering, storm water, mine process wastewater, mine equipment wash water, or suction dredge water.  About 600 mines in South Carolina will be covered by the revised general permit.

SC DHEC posted a draft of the permit for public comment.  SC DHEC did not receive any comments during the 30-day period, which closed September 10. The permit, issued on September 29, 2017, will become effective January 1, 2018.  Storm water pollution prevention plans (SWPPPs) must be revised by May 1, 2018, and facilities must update their storm water monitoring procedures by June 30, 2018, to meet the new requirements.

All facilities that fall under the NPDES permit requirements should closely review the revised permit and take note of the changes, a number of which are outlined below.

Construction activities
The updated general permit defines construction activities as including “any land disturbance or construction related activities integral to the development and operation of the mine.  Those activities and associated stormwater discharges, unless otherwise prohibited, are covered by this permit, e.g. building of access roads, stormwater controls, construction of scale houses, shops, offices, etc.
The updated general permit has new technology-based effluent limits for construction activities.  Those effluent limits are extensive and include measures to minimize erosion and sediment tracking, increase site stabilization, minimize disturbance of steep slopes, restrict discharges, prevent pollution, and increase inspection requirements.

Training requirements
The updated general permit includes greater specificity about training employees responsible for the following:

  • Design, installation, maintenance, and/or repair of controls (including pollution prevention measures)
  • Storage and handling of chemicals and materials that could become contaminants in storm water discharges
  • Conduction and documentation of monitoring and inspections
  • Taking and documenting corrective actions

Specific training depends on a person’s job responsibilities, but all training should include at least an overview of the SWPPP;  spill response procedures, good housekeeping, maintenance requirements, and material management practices; the location of all controls on the site required by this permit, and how they are to be maintained; the proper procedures to follow with respect to the permit’s pollution prevention requirements; and when and how to conduct inspections, record applicable findings, and take corrective actions.

pH flexibility
The updated General Permit expands the concepts of pH flexibility.  Currently, if the pH of a receiving stream is less than 6.0 standard units (6.5 for SFH, SA, and SB waters), discharge pH may be less than 6.0 standard units (6.5 for SFH, SA, and SB waters) only if the discharge pH is not less than the stream pH by a difference of more than 0.2 standard unit.  The stream pH must be analyzed on the day of the discharge.  In the updated permit, SC DHEC allows permittees to request that stream pH sampling be conducted quarterly.  If the request is granted, the stream pH for the purpose of the calculation above shall be determined by the most recent quarterly analytical pH result.
In addition to the potential for reduced monitoring of pH in streams (when pH levels are proven to be lower), the permit allows SC DHEC to increase the maximum pH limit to 9.0 standard units from 8.5 standard units.  To receive that allowance, the permittee must submit information that demonstrates one of the following:

  • The receiving stream flow is significantly greater than the average of the effluent flow.
  • A bench scale test shows that a proportional mixture of effluent and the receiving stream does not exceed a pH of 8.5 standard units.