TMDL Impact on Companies Through Their Stormwater Permits: Effluent Limits & Penalties

Rachel Hill, PE is a project engineer here at Mapistry and our in-house expert on TMDLs with her unique background as a current law student and Masters degree in civil engineering ( see her previous blog on TMDLs).

In our latest Coffee & Compliance webinar, she shared what is happening with TMDLs and the California Industrial Stormwater General Permit (IGP). For companies in California under the IGP, these TMDL requirements went into effect on July 1st, 2020 and could have huge impact on operations due to numeric effluent limits (NELs).

For companies outside California, as Rachel mentioned on the webinar, other states are starting to incorporate TMDLs and having effluent limits (e.g. NELs) in a stormwater permit versus action levels or benchmarks means great regulatory and legal risk.

For companies managing more than one location we have been helping them get ahead of this trend by using software to track sampling results through out the year and analyze trends plus look at leading indicators such as inspection completion and corrective actions to mitigate the risk of exceedances of NELs or effluent limits.

With TMDLs, companies need to be on their toes even more than before and raise awareness across the company for the requirements and what can be done before exceedances (e.g. timely inspections, finding corrective actions, and quickly closing them out)

Some of Rachel takeaways on TMDLs:

1. Identify your watershed and if TMDLs are applicable, especially for the California Annual Report (new questions beyond this version)

2. Look at the options for compliance, including alternative compliance, Time Schedule Order (TSO) or no discharge, to mitigate your risk of exceedances

3. Compare your potential pollutant source assessment with the parameters identified in your TMDL to determine potential applicability