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prohibited.At no time shall concrete be washed off into the footprint of an area <br /> where an infiltration BMP will be installed. <br /> i. Obtain written approval from Ecology before using any chemical treatment,with <br /> the exception of COz,dry ice or food grade vinegar,to adjust pH. <br /> j. Uncontaminated water from water-only based shaft drilling for construction of <br /> building, road,and bridge foundations may be infiltrated provided the wastewater is <br /> managed in a way that prohibits discharge to surface waters. Prior to infiltration, <br /> water from water-only based shaft drilling that comes into contact with curing <br /> concrete must be neutralized until pH is in the range of 5.5 to 8.5 (su). <br /> 10. Control Dewatering <br /> a. Permittees must discharge foundation,vault, and trench dewatering water, which <br /> have characteristics similar to stormwater runoff at the site, in conjunction with BMPs <br /> to reduce sedimentation before discharge to a sediment trap or sediment pond. <br /> b. Permittees may discharge clean, non-turbid dewatering water, such as well-point <br /> groundwater,to systems tributary to, or directly into surface waters of the State, as <br /> specified in Special Condition S9.D.8, provided the dewatering flow does not cause <br /> erosion or flooding of receiving waters. Do not route clean dewatering water through <br /> stormwater sediment ponds. Note that"surface waters of the State" may exist on a <br /> construction site as well as off site;for example,a creek running through a site. <br /> c. Other dewatering treatment or disposal options may include: <br /> i. Infiltration <br /> ii. Transport off site 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 chemical treatment or other suitable treatment <br /> technologies(See S9.D.9.i, regarding chemical treatment written approval). <br /> iv. Sanitary or combined sewer discharge with local sewer district approval, if <br /> there is no other option. <br /> V. Use of a sedimentation bag with discharge to a ditch or Swale for small <br /> volumes of localized dewatering. <br /> d. Permittees must handle highly turbid or contaminated dewatering water separately <br /> from stormwater. <br /> 11. Maintain BMPs <br /> a. Permittees must maintain and repair all temporary and permanent erosion and <br /> sediment control BMPs as needed to assure continued performance of their <br /> intended function in accordance with BMP specifications. <br /> b. Permittees must remove all temporary erosion and sediment control BMPs within <br /> 30 days after achieving final site stabilization or after the temporary BMPs are no <br /> longer needed. <br /> Construction Stormwater General Permit Page 30 <br />