7400 HARDESON RD 2018-01-02 MF Import

4.3.3 Mitigating Impacts on Streams, Fish, and Fish Habitat Areas with soils suitable for large scale infiltration should be protected. Due to the construction of new impervious surfaces, stormwater volumes will increase significantly. Base flow redu:.tions can only be mitigated by the use of infiltration systems for collected stormwater. Infiltration systems will be required whenever feasible, as detecmined by the Public Works Department, particulazly for rooftop runoff. This study area, however, has few areas of soils suitable for large scale infiltration. (SEPA Water, Plant and Animal, and Land and Shoreline Use Yolicies) 2. Where mitigation for impacts :o streams is required, the applicant shall consider the following potential mitigation measures: • Evaluate fish access to the Puget Sound streams bearing or potentially bearing anadromous fish, including Japanese Gulch, Merrill and Ring Creek, Glenwood Creek, Powder Mill Gulch, and Pigeon Creek #2, and improve where appropriate. (SEPA V��ater, Plant and Animal, and Land and Shoreline Use Policies) • Restore the riparian vegetation immediately adjacent to Japanese Gulch stream north of Mukilteo Blvd. Peak flow rates &om the Boeing complex aze partly mitigated by a series of detention ponds and biofiltration systems above Seaway Boulevard. Nevertheless, high flow rates have accelerated channel and bank erosion in Powder Mill Gulch stream. In the event that Boeing requests a permit for additional impervious surface, the City may require better regulation of outflow from the Boeing detention facility to reduce channel erosion rates in Powder Mill Gulch. Improve the habitat within the lower section of Merrill and Ring Creek by the addition of woody debris to the channel to�reate large pools and by importing scarcc spawning gravels to this reach. in addition, evaluate anadromous fish access and improve, if appropriate. , • Provide mitigation credit for the purchase and long term protection of headwater azeas that �vould otheRvise be developed. If the headwaters continue to be protected, Glemvood Creek is likely to maintain its trout population. Implement KCM's recommendations for habitat improvement for Pigeon Creek #2 within Howarth Park. These recommendations call for stream restoration, including creating a more sinuous channel and more pool habitat within the pazk as well as bank revegetation in spccific locations. These improvements, along �vith initial stocking of salmonids and improvement of access, could create a small salmonid fishery in this stream. (SEPA Plant and Animal and Land and Shoreline Use Policies)