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Page 27 of 46 <br />£ BMPs shall be used to prevent or treat contamination of stormwater iunoff by pH <br />modifying sources. Thesc sources include, but are not limited to: bulk cement, <br />cement kiln dust, fly ash, new concrete washing and curing waters, waste streams <br />generated from concrete grinding and sawing, exposed aggregate processes, <br />dewatering concrete vaults, concrete pumping and mixer washout waters. <br />Permittees shall adjust the pH of stormwater if necessary to prevent violations of <br />water quality standards. <br />e. Permittees shall obtain written approval from Ecology prior to using chemical <br />treatment, other than CO� or dry ice to adjust pH. <br />10. Control De-Watering <br />a. Foundation, vault, and trench de-H�atering water, which have similar characteristics <br />to stormwater runoff at the site, shall be discharged into a controlled conveyance <br />system prior to discharge to a sediment trap or sediment pond. <br />b. Clean, non-turbid de-watering water, such as well-point ground water, can be <br />discharged to systems tributary to, or direcdy into surface waters of the state, as <br />specified in S9.D.8, provided the de-watering flow does not cause erosion or <br />flooding of recciving waters. Clean de-watering water should not be routed through <br />stormwater sediment ponds. <br />c. Other de-watering disposal options may include: <br />i. infiltration <br />ii. transport offsite in a vehicle, such as a vacuum flush truck, for legal disposal in <br />a manner that does not pollute state waters, <br />iii. Ecology-approved on-site che�.�ical treatment or other suitable treatment <br />technologies, <br />iv. sanitary sewer dischar�e with local sewer district approval, if thece is no other <br />option, or <br />v. use of a sedimentation bae with outfa// to a ditch or swale for small volumes of <br />localized de-watering. <br />d. Higlily turbid or contaminated dewatering water shall be handled separately from <br />stormwater. <br />11. Maintain BMPs <br />a. All temporary and pennanent crosion and sediment control BMPs shall be <br />maintained and repaired as needed to assure continued performance of thcir <br />intended function in accordance u�th BMP specifications. <br />b. All temporary erosion and sediment control BMPs shall be removed within 30 days <br />after final site stabilization is achieved or after the temporary BMPs are no longer <br />nccdcd. <br />