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Stormwater Pollution Prevention Plan <br /> v a <br /> ■ If discharge is occurring during a storm event equal to or greater than the <br /> ' 10-year, 24-hour event, the allowable discharge rate is the peak flow rate <br /> of the 10-year, 24-hour event. <br /> ■ Discharge to a stream should not increase the stream flow rate by more <br /> than 10 percent. <br /> ' ■ If the discharge is directly to a lake, a major receiving water listed in <br /> Appendix C of Volume 1, or to an infiltration system, there is no discharge <br /> flow limit. <br /> ■ If the discharge is to a municipal storm drainage system, the allowable <br /> discharge rate may be limited by the capacity of the public system. It may <br /> ' be necessary to clean the municipal storm drainage system prior to the <br /> start of the discharge to prevent scouring solids from the drainage <br /> system. <br /> ■ Runoff rates shall be calculated using the methods presented in Volume <br /> 3, Chapter 2 for the pre-developed condition. If no hydrologic analysis is <br /> required for the site, the Rational Method may be used. <br /> ' Monitoring <br /> The following monitoring shall be conducted. Test results shall be recorded on a daily log kept <br /> on site: <br /> Operational Monitoring <br /> ■ pH, conductivity (as a surrogate for alkalinity), turbidity and temperature <br /> of the untreated stormwater <br /> ■ Total volume treated and discharged <br /> ■ Discharge time and flow rate <br /> • Type and amount of chemical used for pH adjustment <br /> • Amount of polymer used for treatment <br /> ■ Settling time <br /> Compliance Monitoring <br /> ' ■ pH and turbidityof the treated stormwater <br /> ' • pH and turbidity of the receiving water <br /> Biomonitoring: Treated stormwater shall be tested for acute (lethal) toxicity. Bioassays shall be <br /> conducted by a laboratory accredited by Ecology, unless otherwise approved by Ecology. The <br /> ' 16 16580.006.doc <br />