1515 132ND ST SE 2022-01-20 - Laserfiche WebLink

Element # 10: Control Dewaterina It is anticipated that dewatering will not be needed. If dewatering is needed the following guidance is provided. Discharge foundation, vault, and trench dewatering water that has similar characteristics to site stormwater runoff into a controlled conveyance system prior to discharge to a stabilized outfall location. Clean, non -turbid dewatering water, such as well -point groundwater, can be discharged to systems tributary to state surface waters, provided the dewatering flow does not cause erosion or flooding of receiving waters. These clean waters should not be routed through stormwater sediment ponds/tanks. Handle highly turbid or contaminated dewatering water from construction equipment operation, clamshell digging, concrete tremie pour, or work inside a cofferdam separately from stormwater at the site. Other disposal options, depending on site constraints, may include: • Infiltration • Transport off -site in vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters • Ecology approved on -site chemical treatment or other suitable treatment technologies • Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering Element #11: Maintain BMPs Temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with BMPs. Sediment control BMPs shall be inspected weekly or after a runoff -producing storm event during the "Dry Season" and daily during the ""Wet Season". The inspection frequency for stabilized, inactive sites shall be determined by the City based on the level of soil stability and potential for adverse environmental impacts. Remove temporary erosion and sediment control BMPs within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed and on the approval of the inspector. Trapped sediment shall be removed or stabilized on site. Permanently stabilize disturbed soil resulting from removal of BMPs or vegetation.