10725 19TH AVE SE 2023-04-07 - Laserfiche WebLink

EROSION CONTROL ELEMENT # 10 - Control De-Watering. Requirements—Control De-Watering 1. Foundation, vault, and trench de-watering water, which have similar characteristics to stormwater runoff at the site, shall be discharged into a controlled conveyance system prior to discharge to a sediment tmp or sediment pond. Channels must be stabilized, as specified in Element#8. 2. Clean,non-turbid de-watering water,such as well-point ground water,can be discharged to systems tributary to waters,as specified in Element#8,provided the de-watering flow does not cause erosion or flooding.These clean waters should not be routed through stormwater sediment ponds. 3. Highly turbid or contaminated dewatering water from construction equipment operation, clamshell digging,concrete tremie pour,or work inside a cofferdam,shall be treated separately from stormwater. Other disposal options,depending on site constraints,may include: 1. Infiltration 2. Transport offsite in a vehicle,such as a vacuum flush truck,for legal disposal in a manner that does not pollute surface waters, 3. Ecology-approved on-site chemical treatment or other suitable treatment technologies, 4. Sanitary sewer discharge with City and King County Wastewater Treatment Division approval. 5. Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering. The following Best Management Practices,(BMPs),the ones that the Contractor will implement on site,to meet the erosion control requirements listed above: ❑ Level Spreader—BMP C206 ❑ Other ✓ Not Applicable—See explanation below There will be no dewatering on this project. Dewatering, if any, will be discharged to the natural vegetated area at the rear of the property and through at least 50 feet of existing vegetated ground cover that will filter out any sediment. There will be no discharge to storm drains. 17