Colorado Department of Public Health and Environment (CDPHE) recently issued the renewed Industrial Stormwater General Permit for Non-Extractive Industries (COR900000) became effective on July 1, 2024. CDPHE incorporated various changes to the stormwater permit including the addition of Per- and Polyfluoroalkyl (PFAS) requirements, revisions to benchmarks and corrective actions, and the institution of Additional Implementation Measures (AIM). An additional modification of the permit was released on March 14, 2024, to clarify various requirements. The March 2024 modifications are primarily administrative in nature, aimed at improving understanding and implementation of permit requirements without altering water quality impact. The new stormwater permit changes are addressed in detail below.
Per- and Polyfluoroalkyl (PFAS) Requirements
Following current regulatory practice, CDPHE has incorporated standards and requirements related to PFAS into the Industrial Stormwater General Permit. Also known as “forever chemicals”, PFAS are bioaccumulative and can cause serious adverse health effects including decreased fertility, developmental effects, and increased risk of some cancers. The US Environmental Protection Agency (EPA) has issued a PFAS Strategic Roadmap and instructed EPA regional directors to address PFAS discharges. According to CDPHE, PFAS have been detected in waters along the Front Range.
Due to the widespread use of aqueous film forming foams (AFFF) containing PFAS and data showing PFAS contamination at airports, CDPHE is imposing automatic monitoring requirements for Sector S airports in Colorado. The renewed permit will require airports to monitor and report PFAS once per quarter until 4 samples are obtained. Similarly, landfills (Sectors K and L) will also be required to conduct automatic monitoring since PFAS may be present as a result of the wastes accepted by landfills. Landfills that accept only coal ash and have no sources of PFAS at the facility are exempt from PFAS monitoring.
In addition to landfills and airports, CDPHE has identified additional higher risk industrial sectors:
- Sector A – Timber Products
- Sector B – Paper and Allied Products
- Sector C – Chemical and Allied Products Manufacturing, and Refining
- Sector E – Glass, Clay, Cement, Concrete, and Gypsum Products
- Sector N – Scrap Recycling and Waste Recycling Facilities
- Sector O – Steam Electric Generating Facilities
- Sector P – Land Transportation and Warehousing (SIC code 5171 only)
- Sector AA – Fabricated Metal Products
- Sector AC – Electronic and Electrical Equipment and Components, Photographic and Optical Goods
Operators in these sectors will receive a survey from CDPHE and if a response is not received within 60 days, CDPHE will presume PFAS are used and released at the facility; PFAS monitoring requirements will be added to the permit certification. Due to the cost of PFAS monitoring, CDPHE will allow for use of substantially identical outfalls, provided samples are rotated among representative outfalls. In this case, each outfall that has a discharge during the permit term must be sampled for PFAS at least once.
The renewal permit also includes new practice-based effluent limits to minimize the discharge of PFAS in stormwater. CDPHE will require that facilities take reasonable steps to identify whether materials on site (such as firefighting foams) contain PFAS, but they will not include numeric limits for PFAS in permit certifications under this permit term.
Benchmarks
In addition to PFAS requirements, CDPHE also revised benchmarks in the renewed General Permit. CDPHE continues to follow EPA’s approach by establishing benchmarks at levels to protect aquatic life. Benchmarks generally reference acute toxicity. Benchmark level revisions include copper, aluminum, cadmium, lead, total recoverable iron and magnesium, and selenium. A selection of revised benchmarks is shown in the table below. A complete listing of benchmark revisions is provided in CDPHE’s Stormwater Permit Fact Sheet.
| Pollutant | 2012 COR900000 Benchmark | Renewal COR900000 Benchmark | Difference or Change |
| pH | 6-9 | 6-9 | Extended to Subsector E2 (Concrete and Gypsum Product Manufacturers) |
| Cadmium (mg/L) | 0.0021 total recoverable | 0.0021, dissolved | CO standard is expressed as dissolved instead of total recoverable |
| Cyanide (mg/L) | 0.022, total recoverable | 0.005, free | CO criterion is more protective |
| Lead (mg/L) | 0.082 | 0.082, dissolved | CO standard is expressed as dissolved instead of total recoverable |
| Magnesium (mg/L) | 0.064 | Removed | Benchmark was removed |
| Selenium (mg/L), total recoverable | 0.005 | 0.0015 (lentic) or 0.0031 (lotic) | EPA’s new acute criterion for Selenium |
| Silver (mg/L) | 0.0032 | 0.002, dissolved | CO criterion more protective due to conversion factor |
Additional Implementation Measures (AIM)
In addition to benchmark changes, the renewed General Permit includes a tiered system of Additional Implementation Measures (AIM) that apply when a benchmark level is exceeded. The goal of AIM is to reduce pollutant discharges. AIM Levels 1, 2, and 3 will be required if exceedances occur and continue. At each subsequent level, more robust control measures and Best Management Practices (BMP) apply. For example, Level 1 status requires an extra site inspection to ensure control measures are operating as designed, while Level 3 status requires additional measures or treatment to remove pollutants.
CDPHE will consider up to four quarters of sampling results collected prior to the renewal permit issuance to determine AIM status for existing permittees. Previously unpermitted facilities will start with no AIM requirements. The renewed permit allows for a facility to avoid AIM requirements if a demonstration is made showing exceedances are due to natural background pollutants.
Coal Tar Sealant (Poly Aromatic Hydrocarbons, PAH)
Due to PAH presence in stormwater and its link to coal tar sealant, CDPHE is adding a new limitation on coverage to address stormwater runoff from areas where coal tar has been applied. Discharges of stormwater from areas with coal tar sealant applied after the effective date of the permit will be ineligible for coverage under the new permit. This limitation does not apply to areas of the site that are not included in the permit, such as employee parking areas for which drainage is not mixed with industrial runoff. Asphalt-based sealants are recommended as an alternative to coal tar sealants. PAH concentrations are an order of magnitude lower in asphaltic sealants compared to coal tar sealants and are affordable substitutes.
Discharge Preparation Plans
The renewal permit will require facilities that experience no discharge in the first four quarters of the permit term to develop a Discharge Preparation Plan. This is a one-time requirement that will determine conditions that are likely to produce a measurable storm event. The Plan must be reported to CDPHE in the annual report.
For a detailed review of how the renewed Stormwater General Permit may impact your facility, please email Libby Hyde in Trinity’s Denver office or call 720.638.7647.
