Monday, January 4, 2010

Washington Mandatory BMP and Industrial Stormwater Requirements

The revised Washington Department of Ecology industrial stormwater general permit became effective on January 1, 2010. The revised permit has numerous substantive changes compared to the previous industrial stormwater permit. Some highlights of these changes include:

Stormwater Pollution Prevention Plan (SWPPP) Requirements

Mandatory BMPs must be implemented no later than July 1, 2010. The facility may omit individual BMPs if site conditions render the BMP unnecessary, infeasible, or the Permittee provides alternative and equally effective BMPs; and justifies the omission in the SWPPP. The mandatory BMPs include:

Operational Source Control BMPs:

  • Vacuum paved surfaces with a vacuum sweeper once each quarter.
  • Minimize stormwater contamination from dust. Inspect and maintain bag houses monthly.
  • Keep all dumpsters under cover or keep dumpster lid closed when not in use.
  • Clean catch basins when at capacity.
  • Inspect all equipment and vehicles for leaking fluids. Take leaking equipment and vehicles out of service or prevent leaks until repaired.
  • Store all chemical liquids, fluids, and petroleum products on an impervious surface with containment that is capable of containing 10% of the total enclosed tank volume or 110% of the volume contained in the largest tank, whichever is greater.
  • Prevent precipitation from accumulating in containment areas.
  • Locate spill kits within 25 feet of all stationary fueling stations, fuel transfer stations, and mobile fueling units.
  • Facility personnel can not lock shut-off fueling nozzles in the open position, or “top-off” tanks being refueled.
  • During fueling, facility personnel must block, plug or cover storm drains that receive runoff from areas where fueling.
  • Use drip pans or equivalent containment measures during all petroleum transfer operations.
  • Maintain a spill log that documents chemical and petroleum spills.
Structural Source Control BMPs:
  • Use grading, berming, or curbing to prevent runoff of contaminated stormwater flows and divert run-on away from manufacturing, processing, and material storage areas.
  • Perform all cleaning operations indoors, under cover, or in bermed areas that prevent stormwater runoff and run-on and capture any overspray. Drain wash water to a collection system for further treatment or storage.

SWPPP Signature/Certification

The Permittee must sign and certify the SWPPP and any revisions.

Benchmark Monitoring / Sampling

Facility must sample each distinct point of discharge off-site each calendar quarter; except “substantially identical outfalls”. Sampling must occur within the first 12 hours of stormwater discharge or as soon as practicable after the first 12 hours. Facilies must sample the stormwater discharge from the first fall storm event, after October 1st. “Consistent attainment” requires that four consecutive quarterly samples be equal to or less than the benchmark value; or for pH, within the range of 5.0 – 9.0.

Benchmarks and Effluent Limitations
Click here to review new stormwater benchmark concentrations

Discharges to 303(d)-Listed Waters

Numeric effluent limits now apply to facilities with discharges to 303(d)-listed impaired waterbodies (Category 5).


Qualified personnel conduct and document visual inspections of the site monthly. Dry season and annual comprehensive inspection eliminated.

Corrective Actions

Permittees that exceed benchmark value (for a single parameter) for any two quarters during a calendar year complete a Level 2 Corrective Action (Structural Source Control BMPs). Permittees that exceed benchmark value (for a single parameter) for any three quarters during a calendar year complete a Level 3 Corrective Action (Treatment BMPs).

Facilities must revise their SWPPP and complete installation by September 30th the following year. All corrective actions must be documented in Annual Report. A licensed professional engineer, geologist, hydrogeologist, or certified professional in storm water quality (CPSWQ) must design and stamp the portion of the SWPPP that addresses (Level 3) stormwater treatment structures or processes.

Caltha LLP provides expert consulting services to public and private sector clients nationwide to address Stormwater Permitting & Regulatory Support, Stormwater Pollution Prevention Plans (SWPPP), Stormwater Monitoring and Stormwater Training.

For further information contact Caltha LLP at
Caltha LLP Website

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