Tuesday, November 25, 2008

MPCA Industrial Stormwater - Key Elements of Draft Permit

UPDATE: On July 6, 2009, MPCA is scheduled to release its proposed Multisector Industrial General Stormwater Permit. In July, Caltha LLP will be hosting seminars in several cities across Minnesota to provide information on the proposed permit and rule changes, and steps facilities can take to reduce their impact.

For more information, go to:

MPCA SWPPP Permit - Industrial Stormwater Permit Reissue Seminars


The Minnesota Pollution Control Agency has been drafting its revised general permit for stormwater discharges from industrial sites. The current general permit was written in 1997, and the upcoming revision will reflect major changes in stormwater permitting requirements.

A partial draft permit was released on November 20, 2008. This draft did not contain some important sections of the permit – most significantly, it did not include any SECTOR SPECIFIC requirements which will be incorporated into the final permit. All sections of the draft are subject to further revision; this article provides a briefing on some of the key elements of the draft permit.

Some key requirements in the draft permit are:

Requirements for Designated “Special” Waters. MPCA intends to have additional requirements for stormwater discharges to a number of different types of special waters, such as trout streams, wetlands and others. The nature of these additional requirements has not been released.

Facility Inspections. Facility inspections will need to be conducted on a monthly basis. All employee(s) performing inspections must be trained.

Maintenance of BMPs. If BMPs/structural controls are found to be not functioning properly, repairs should be made within seven days. Anyone performing installation, inspection, maintenance and repair of BMPs must have appropriate training.

Mercury Minimization Plan. Each permittee must evaluate their facility to determine if any sources of mercury are potentially exposed to stormwater. If mercury sources or devices are found, a Mercury Minimization Plan must be developed.

Stormwater Monitoring. The most important change compared to the current MPCA general permit is the requirement to sample stormwater discharges. All permittees will collect and analyze at least four quarterly samples during Year 2 of permit coverage. Depending on the results, further samples may need to be collected in Year 4 and 5, and corrective actions may be required. Additional reporting and evaluations will be required for dischargers who continue to exceed benchmark concentrations.

Related Links:
Flowchart of Draft MPCA Stormwater Monitoring Requirements
Further information on stormwater benchmarks
Comparison of stormwater benchmarks to typical discharge data

Further information on selecting stormwater monitoring techniques

Special Requirements for Stormwater Infiltration. MPCA intends to include specific requirements for the design and operation of infiltration BMPs. For some industry sectors, infiltration will be prohibited.

For further information contact Caltha LLP at
Caltha LLP Website

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