7301 HARDESON RD 2019-01-11 - Laserfiche WebLink

6.2 Stormwater Quality Monitoring The construction site is greater than one acre in size, and does not discharge to an impaired water body, and is therefore subject to the general water quality monitoring requirements set forth in the 2016 Construction Stormwater General Permit(Appendix D). Turbidity sampling and monitoring will be conducted during the entire construction phase of the project. Samples will be collected per the monitoring plan at the monitoring locations noted in the TESC plans in Appendix A. If there is no flow in these locations,the attempt to sample will be recorded in the site log book and reported to Ecology in the monthly Discharge Monitoring Report(DMR) as "No Discharge". 6.2.1 Turbidity Sampling Monitoring requirements for the proposed project will include either turbidity or water transparency sampling to monitor site discharges for water quality compliance with the 2016 Construction Stormwater General Permit(Appendix D). Sampling will be conducted at all discharge points at least once per calendar week. Turbidity or transparency monitoring will follow the analytical methodologies described in Section S4 of the 2016 Construction Stormwater General Permit(Appendix D). The key benchmark values that require action are 25 NTU for turbidity(equivalent to 32 cm transparency) and 250 NTU for turbidity (equivalent to 6 cm transparency). If the 25 NTU benchmark for turbidity(equivalent to 32 cm transparency) is exceeded, the following steps will be conducted: 1. Ensure all BMPs specified in this SWPPP are installed and functioning as intended. 2. Assess whether additional BMPs should be implemented, and document revisions to the SWPPP as necessary. 3. Sample discharge location daily until the analysis results are less than 25 NTU (turbidity) or greater than 32 cm(transparency). If the turbidity is greater than 25 NTU(or transparency is less than 32 cm)but less than 250 NTU (transparency greater than 6 cm) for more than 3 days, additional treatment BMPs will be implemented within 24 hours of the third consecutive sample that exceeded the benchmark value. Additional treatment BMPs to be considered will include,but are not limited to, off-site treatment, infiltration, filtration and chemical treatment. if the 250 NTU benchmark for turbidity(or less than 6 cm transparency) is exceeded at any time, the following steps will be conducted: 1. Notify Ecology by phone within 24 hours of analysis (see Section 5.0 of this SWPPP for contact information). UNDERWOOD GARTLAND JOHNSON 63,LLC April 2017 Stormwater Pollution Prevention Plan Page 16