1001 N BROADWAY EVCC 2025-10-03 - Laserfiche WebLink

4. Sampling and Analysis Methods a. The Permittee performs turbidity analysis with a calibrated turbidity meter (turbidimeter) either on site or at an accredited lab.The Permittee must record the results in the site log book in nephelometric turbidity units (NTUs). b. The Permittee performs transparency analysis on site with a 1% inch diameter, 60 centimeter(cm)-long transparency tube. The Permittee will record the results in the site log book in centimeters(cm). Table 4 Monitoring and Reporting Requirements Parameter ` Unit Analytical Method Sampling Benchmark, Frequency Value Turbidity NTU SM21.30 Weekly, if 25 NTUs discharging Manufacturer Weekly, if Transparency Cm instructions,or discharging 33 cm Ecology guidance 5. Turbidity/Transparency Benchmark Values and Reporting Triggers The benchmark value for turbidity is 25 NTUs.The benchmark value for transparency is 33 centimeters(cm). Note: Benchmark values do not apply to discharges to segments of water bodies on Washington State's 303(d) list (Category 5)for turbidity, fine sediment, or phosphorus;these discharges are subject to a numeric effluent limit for turbidity. Refer to Special Condition S8 for more information and follow S5.F—Noncompliance Notification for reporting requirements applicable to discharges which exceed the numeric effluent limit for turbidity. a. Turbidity 26—249 NTUs, or Transparency 32—7 cm: If the discharge turbidity is 26 to 249 NTUs; or if discharge transparency is 32 to 7 cm,the Permittee must: i. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs, and no later than 10 days of the date the discharge exceeded the benchmark. if installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. ii. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. iii. Document BMP implementation and maintenance in the site log book. b. Turbidity 250 NTUs or greater, or Transparency 6 cm or less: If a discharge point's turbidity is 250 NTUs or greater, or if discharge transparency is less than or equal to 6 cm,the Permittee must complete the reporting and adaptive Construction Stormwater General Permit Page 14