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Stormwater Pollution Prevention Plan <br /> Treatment shall be indicated on the Notice of Intent for coverage under the General <br /> Construction Permit. Chemical treatment systems should be designed as part of the <br /> Construction SWPPP, not after the fact. Chemical treatment may be used to correct <br /> problem sites in limited circumstances with formal written approval from Ecology and <br /> the Local Permitting Authority. <br /> The SEPA review authority must be notified at the application phase of the project review (or the <br /> time that the SEPA determination on the project is performed) that chemical treatment is <br /> proposed. If it is added after this stage, an addendum will be necessary and may result in <br /> project approval delay. <br /> See Appendix II-B for background information on chemical treatment. <br /> Criteria for Chemical Treatment Product Use <br /> Chemically treated stormwater discharged from construction sites must be nontoxic to aquatic <br /> organisms. The following protocol shall be used to evaluate chemicals proposed for stormwater <br /> treatment at construction sites. Authorization to use a chemical in the field based on this <br /> protocol does not relieve the applicant from responsibility for meeting all discharge and <br /> receiving water criteria applicable to a site. <br /> • Treatment chemicals must be approved by EPA for potable water use. <br /> • Petroleum-based polymers are prohibited. <br /> ■ Prior to authorization for field use,jar tests shall be conducted to <br /> demonstrate that turbidity reduction necessary to meet the receiving <br /> water criteria can be achieved. Test conditions, including but not limited <br /> to raw water quality and jar test procedures, should be indicative of field <br /> conditions. Although these small-scale tests cannot be expected to <br /> reproduce performance under field conditions, they are indicative of <br /> treatment capability. <br /> • Prior to authorization for field use, the chemically treated stormwater shall <br /> be tested for aquatic toxicity. Applicable procedures defined in <br /> Chapter 173-205 WAC, Whole Effluent Toxicity Testing and Limits, shall <br /> be used. Testing shall use stormwater from the construction site at which <br /> the treatment chemical is proposed for use or a water solution using soil <br /> from the proposed site. <br /> • The proposed maximum dosage shall be at least a factor of five lower <br /> than the no observed effects concentration (NOEC). <br /> • The approval of a proposed treatment chemical shall be conditional, <br /> subject to full-scale bioassay monitoring of treated stormwater at the <br /> construction site where the proposed treatment chemical is to be used. <br /> 14 17576.003.doc <br />