Benchmark Monitoring Requirements Under MDE Draft Industrial General Permit

Maryland Department of the Environment (MDE) is issuing a draft General Permit Number 12-SW of 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. The final permit is expected to be issued in early 2013.

Read a summary of the key changes to the Maryland General Permit.

Information about Maryland General Permit SWPPP Template and Compliance Plan

One of the key difference in the draft permit compared to the EPA MSGP is that 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:
1. perform corrective actions, and conduct an additional 4 quarters of monitoring until the average value is below the benchmark, or
2. 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.

Caltha LLP provides expert consulting services to public and private sector clients nationwide to address Stormwater Permitting and Regulatory Support, Stormwater Pollution Prevention Plans (SWPPP), Stormwater Monitoring and Stormwater Training.
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