Maryland Department of the Environment (MDE) is issuing a draft General Permit Number 12-SW for stormwater discharges from industrial facilities. MDE has chosen to base the state’s permit on the EPA’s Multi-Sector General Permit (MSGP).
The draft permit will replace the General Permit Number 02-SW that was issued for a five-year term on December 1, 2002. The General Permit 02-SW expired on November 30, 2007 but was administratively continued for facilities that were covered under the permit at the time it expired. In 2012, over 800 facilities held 02-SW permits in the state, and over 100 facilities were exempted as having industrial activity but verified none exposure.
MDE has made several important changes from the MSGP including:
Design Manual as Guidance in Restoration of Impervious Surfaces
The permit references specific Design Manual for Stormwater Management and additional implementation guidance. Permittees are required to implement the restoration of impervious surfaces on 20% of the untreated impervious surface at their facility, or equivalent actions.
Electronic Systems for Reporting Monitoring Data
Permittees required to perform the quarterly benchmark monitoring are required to submit Discharge Monitoring Reports (DMRs) to MDE electronically through NetDMR.
Water Quality-Based Effluent Limits
The draft permit contains new, specific WQBEL requirements applicable to impaired waters and antidegradation policies:
- ·Discharges to Impaired Waters – The permit contains requirements for new and existing discharges to impaired waters with or without EPA approved or established TMDLs. New dischargers are only eligible for discharge authorization if they demonstrate that there is either no exposure of stormwater to the pollutant for which the water is impaired, or the impairment pollutant is not present at the facility, or that the discharge is not expected to cause or contribute to a water quality standards exceedance. For existing discharges to impaired waters with State approved or established TMDLs, MDE will determine if more stringent requirements are necessary to ensure that the permittee is discharging consistent with the TMDL and applicable WLA.
- ·Antidegradation Requirements – MDE has clarified its expectation of operators to meet antidegradation requirements as part of the permit authorization process as well as to comply with permit provisions after authorization to discharge is received. If an NOI indicates that an operator is seeking coverage for a new discharge to a Tier 2 water, MDE will determine if additional requirements are necessary to be consistent with the applicable antidegradation requirements, or if alternatively, an individual permit application is necessary. New dischargers are no longer eligible for coverage under this permit for discharges to waters designated as Tier 3 for antidegradation purposes.
Permit provisions specify the types of conditions at the site that trigger corrective action requirements, what must be done to eliminate such conditions or conduct further inquiries into their cause, and the deadlines for completing corrective action. A summary of all corrective actions initiated and/or completed each year must be documented in the annual comprehensive site inspection report and kept with the SWPPP.
Benchmark Monitoring verses Volume Reduction
MDE chose to focus on reducing stormwater volume rather than on benchmark monitoring for specific pollutants. MDE evaluated the full list of benchmark monitoring requirements in the MSGP, and narrowed the selection down to three industries that have the highest potential for metals in their stormwater,
1) Subsector C1 – Agricultural Chemicals for (SIC 2873-2879), part of Sector C – Chemical and Allied Products Manufacturing, and Refining (Nitrate plus Nitrite Nitrogen at 0.68 mg/L, Total Lead at 0.014, Total Iron at 1.0 mg/L, Total Zinc at 0.04 mg/L and Phosphorus at 2.0 mg/L).
2) Sector M – Automobile Salvage Yards (Total Suspended Solids (TSS) at 100 mg/L, Total Aluminum at 0.75 mg/L, Total Iron at 1.0 mg/L, Total Lead at 0.014 mg/L).
3) Sector N – Scrap Recycling and Waste Recycling Facilities (Chemical Oxygen Demand (COD) at 120 mg/L, Total Suspended Solids (TSS) at 100 mg/L, Total Recoverable Aluminum at 0.75 mg/L, Total Recoverable Iron at 1.0 mg/L, Total Recoverable Lead at 0.014 mg/L, Total Zinc at 0.04 mg/L, Total Recoverable Copper at 0.0038 mg/L).
4) Sector AA – Fabricated Metal Products (Nitrate plus Nitrite Nitrogen at 0.68 mg/L, Total Zinc at 0.04 mg/L)
Benchmark monitoring must occur during the first 4 full quarters of permit coverage after the permittee is granted access to NetDMR. If the average of the 4 quarters of monitoring values exceeds the benchmark, the permittee is required to either:
- perform corrective actions, and conduct an additional 4 quarters of monitoring until the average value is below the benchmark, or
- determine that no further pollutant reductions are technologically available and economically practicable and achievable in light of best industry practice to meet applicable effluent limits, and continue to monitor once-per-year.
Permittees are required to evaluate the stormwater runoff from their facility in an annual report that includes the findings from their annual comprehensive site inspection report and a report detailing any conditions triggering corrective action and the status of those actions taken in response.
Industry Sector-specific Requirements
The draft permit contains provisions that require industrial facilities in 26 different industrial sectors yo implement control measures and develop site-specific stormwater pollution prevention plans (SWPPP) to comply with NPDES requirements