Proposed Maryland NPDES Industrial Stormwater Permit Requires Treatment of 20% of Impervious Surfaces

The Maryland Department of Environmental Protection (MDE) is proposing to make significant revisions to its General Permit for Discharges of Stormwater Associated With Industrial Activities. These revisions go far beyond the requirements for implementation of Best Management Practices (BMPs), many of which have been non-structural and the core of the industrial stormwater permitting program as documented in a facility’s Stormwater Pollution Prevention Plan (SWPPP).  The proposed permit will require physical changes to a facility and will likely result in significant costs to the permittee.

The revised permit requires specific control measures in the SWPPP based on the facility type. When this permit is formally adopted, industries will have 90 days to file an application, fee payment, and SWPPP. Most significantly, the permit requires restoration of impervious surfaces using the updated Maryland Stormwater Design Manual or equivalent actions in order to address Maryland requirements for the Chesapeake Bay and local TMDLs. The requirement mandates that permit holders treat 20% of the impervious surfaces not currently treated to the standards of the Design Manual by the fifth year of the permit term. This might include construction of bioretention basins, conversion of paved areas to pervious paving, or installation of green roofs. An implementation plan and yearly updates are required to be submitted to the MDE.

The new General Permit application now requires more detailed information relevant to the permit conditions, such as local stream impairments or TMDLs, and calculated area of impervious surfaces. Also required is an electronic version of a SWPPP including a site map illustrating discharge locations and other information regarding activities of the applicant to protect waters of the state.

Another important change in this permit is the new monitoring requirements. These include new requirements to perform quarterly visual examinations of stormwater discharges. The proposed permit also allows the MDE to require monitoring and online electronic submission of Discharge Monitoring Reports in specific cases where local discharge is to an impaired water body. Furthermore, it requires monitoring without limits for benchmark parameters for some industrial waste sectors, including Agricultural Chemicals, Automobile Salvage, Scrap Recycling and Waste Recycling Facilities, and Fabricated Metal Products.

The MDE will be holding public hearings concerning the proposed revisions to the General Permit on November 26 and 30, 2012. For complete details visit the MDE Stormwater Permit webpage.

If you have questions regarding your Maryland NPDES Stormwater Permit, please call Jim Cinelli, PE, BCEE at 800.305.6019.