The Tennessee Department of Environment and Conservation (TDEC) issued a new multi-sector general permit (TMSP), known as the multi-sector permit, which has gone into effect July 1 of 2025. The TMSP covers discharges of stormwater associated with industrial activities in Tennessee.

The 2024 TMSP includes major changes compared to the last time the TMSP incorporated updates to the United States Environmental Protection Agency’s (EPA) Multi Sector General Permit (MSGP), in 2015. The new TMSP has adopted select provisions from the EPA’s 2021 MSGP while retaining certain state-specific requirements from the prior TMSP that TDEC has found appropriate.

Facilities with existing coverage should reapply for coverage under the new TMSP no later than September 30, 2025. The facility Stormwater Pollution Prevention Plan (SWPPP) should be updated to the new TMSP requirements by the date NOI is submitted. New facilities without TMSP coverage must submit their NOI at least 30 days before commencing discharge. All facilities are also required to keep a copy of the Notice of Coverage (NOC) confirming TMSP authorization for their discharges.

Major Permit Changes

Reorganization

The new TMSP has been substantially restructured. While sector-specific requirements, such as effluent limitations, coverage limitations, and monitoring requirements, remain organized by industrial sector, general requirements have been consolidated and placed at the beginning of the permit. This restructuring has resulted in modified general permit language and additional clarification of definitions and general requirements.

Electronic Reporting

The new TMSP requires Notice of Intent (NOI) forms to be submitted electronically to MyTDEC Forms, accompanied by an updated SWPPP. TDEC encourages facilities with existing coverage to submit their SWPPP alongside the NOI, however it is not required.

Stormwater monitoring is required by specific industry sectors. Annual submissions of Discharge Monitoring Results (DMRs) should be submitted electronically using NetDMR. Monitoring results, alongside any supporting data, should be submitted no later than March 31 of the following calendar year.

Facilities which have already sampled and submitted results for 2025 via forms and email should resubmit results via NetDMR by March 31, 2026.

Monitoring/Sampling Changes

The TMSP includes monitoring/inspection requirements, which apply to every authorized discharge point or outfall specified by the facility. Monitoring requirements include:

• Quarterly visual inspections;
• Annual comprehensive facility inspections;
• Annual benchmark monitoring;
• Annual stormwater sampling (sector specific):
  • Benchmark monitoring;
  • Effluent limitations.

Benchmark monitoring requires a comparison of stormwater samples to posted benchmark thresholds. Exceedances to benchmark thresholds are not considered violations but will result in a requirement to implement additional implementation measures (AIM). Some notable changes to benchmark thresholds to the new TMSP are listed below.

Additional Implementation Measures (AIM)

TDEC has implemented new monitoring corrective measures/ actions under the TMSP. Triggering events describe occurrences where one or more the following observations are indicated at an outfall:

• Floating, settled or suspended solids, scum, oil sheen, or other substances;
• Effluent discoloration;
• Accumulation of pollutants at the outfall; or
• Runoff results indicate an exceedance of corresponding monitoring values.

Should a triggering event occur, the facility must apply AIM to prevent further exceedance and lower the presence of pollutants in the specific discharge point. The requirements for AIM vary depending on the severity and frequency of exceedances.

Upon the first baseline exceedance of a benchmark value, the facility is required to initiate the following corrective actions within 30 days of receiving results:

• Conduct a comprehensive facility inspection, preferably under wet weather conditions, with a goal to identify source(s) of pollutant(s) of concern;
• Determine if SWPPP modifications are necessary to improve stormwater runoff quality;
• Initiate SWPPP modifications, if applicable;
• Update SWPPP with the findings; and
• Provide summary of actions with the NetDMR monitoring results submission.

If the following actions have been taken and the subsequent sampling results do not exceed the benchmark thresholds, then the facility returns to baseline status.

For subsequent or repeated benchmark/ELG exceedances of the same parameter at the same outfall, the facility must implement one of the two actions:

• Engage a licensed professional to conduct an evaluation of facility and recommend SCM improvements; or
• Increase stormwater runoff monitoring frequency to once per quarter. Increased monitoring frequency is limited to:
  • The pollutant(s) which exceeded benchmark values; and
  • The outfall(s) where exceedances were observed.

Additional Changes

The TMSP requires facilities to document the location of designated critical habitat and types of stormwater control measures that comply with the Endangered Species Act and National Historic Preservation Act. To determine whether designated critical habitat exists on the facility property, the following tools are recommended: US Fish and Wildlife Service (USFWS) free Arcgis mapping system and the USFWS Information for Planning and Consultation report.

The facility’s SWPPP should include a site map, which identifies locations of potential pollutant sources and stormwater discharge. The SWPPP site map should also include the following new requirements:

• Size of property in acres;
• Stormwater control measures (SCMs);
• Municipal separate storm sewer systems (MS4s)
• Identified exceptional Tennessee waters
• Substantially identical discharge points (SIDPs);
• Areas of designated critical habitat under the Endangered Species Act.

For any additional questions about the requirements of the new TMSP, contact Trinity’s Knoxville office at 865.326.2800 or email Ian Smith.