MPCA Benchmarks Compared to Past Stormwater Monitoring Data

Industrial Stormwater Benchmarks – Comparison of New Minnesota Benchmark Concentrations To Historic Industry-specific Testing Results

Conclusions:

• Benchmarks more likely to be exceeded are:
  Total suspended solids (TSS)
  Metals, especially iron
• All industrial sectors are equally likely to exceed benchmarks for TSS
• For toxic chemicals and metals, volume of use or storage on-site is not a good predictor of meeting benchmarks
• Certain industrial sectors are more likely to exceed other benchmarks
  Food sector – COD, BOD
  Sawmills – COD
  Primary metals/foundries – Fe, Cu
  Concrete plants – Fe
  Salvage yards – Al, Fe
• Improving chance of meeting benchmarks requires active prevention program
• Resampling without corrective action does not improve chances of meeting benchmarks
  

Link to presentation slides

Abstract:
In 2010, the Minnesota Pollution Control Agency (MPCA) reissued the Multi-Sector General Permit (MSGP) for industrial stormwater discharges. The reissued permit included significant changes to stormwater discharge requirements for permitted sites, which are now divided into 29 industrial sectors. One of the most significant changes was the requirement for sampling stormwater and reporting results to MPCA. Each sector has been assigned sector-specific stormwater benchmark concentrations. Beginning in June 2011, all sites permitted under the MSGP will have to collect stormwater samples and have samples analyzed for their sector-specific benchmark parameters. If one or more benchmarks are exceeded, sites will be required to upgrade their pollution prevention measures and will need to do further stormwater monitoring.

Since the 1980s, the U.S. Environmental Protection Agency (USEPA) has collected industry-sector data on stormwater discharge. The linked presentation provides a comparison of these historic industrial stormwater results to the current MPCA stormwater benchmark concentrations. The results are discussed in context of which stormwater benchmark parameters have a higher potential for exceedance of benchmark values. The paper also discusses which of the industrial sectors have a higher potential for exceedance of their specific benchmark values.

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