819 N BROADWAY WASHINGTON STATE UNIVERSITY 2018-05-11

Stormwater Pollution Prevention Plan 6.2 Stormwater Quality Monitoring The applicant will monitor for the parameter(s) of concern described in the sections below and document monitoring results in the site log book during construction. The applicant will manage stormwater and construction dewatering discharges such that the discharge is consistent with applicable water quality requirements. Where there is no off site discharge from the construction site during a calendar week, sampling is not required. Sampling is not required outside of normal working hours or during unsafe conditions. 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 2005 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 2005 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. 18