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pumping and mixer washout waters. (Also refer to the defmition for"concrete <br /> wastewater" in Appendix A--Definitions.) <br /> g. Adjust the pH of stormwater or authorized non-stormwater if necessary to <br /> prevent an exceedance of groundwater and/or surface water quality standards. <br /> h. Assure that washout of concrete trucks is performed off-site or in designated <br /> concrete washout areas only. Do not wash out concrete trucks or concrete <br /> handling equipment onto the ground,or into storm drains, open ditches, streets, <br /> or streams. Do not dump excess concrete on site, except in designated concrete <br /> washout areas. Concrete spillage or concrete discharge to surface waters of the <br /> State is prohibited. <br /> i. Obtain written approval from Ecology before using any chemical treatment, <br /> with the exception of CO2 or dry ice used 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 <br /> wastewater is managed in a way that prohibits discharge to surface waters.Prior <br /> to infiltration,water from water-only based shaft drilling that comes into contact <br /> with curing concrete must be neutralized until pH is in the range of 6.5 to 8.5 <br /> (su). <br /> 10. Control Dewatering <br /> a. Permittees must discharge foundation,vault,and trench dewatering water, <br /> which have characteristics similar to stormwater runoff at the site, into a <br /> controlled conveyance system before discharge to a sediment trap or sediment <br /> pond. <br /> b. Permittees may discharge clean,non-turbid dewatering water, such as well- <br /> point ground water, to systems tributary to,or directly into surface waters of the <br /> State, as specified in Special Condition S9.D.8,provided the dewatering flow <br /> does not cause erosion or flooding of receiving waters. Do not route clean <br /> dewatering water through stormwater sediment ponds.Note that"surface waters <br /> of the State"may exist on a construction site as well as off site; for example, a <br /> 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 <br /> disposal in 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 <br /> approval). <br /> iv. Sanitary or combined sewer discharge with local sewer district approval, <br /> if there is no other option. <br /> Construction Stormwater General Permit <br /> Page 34 <br />