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7.B. - Page 62 2 Environmental Analysis <br /> Most of the proposed construction activity would occur adjacent to Redwood Creek,in areas of <br /> disturbed ruderal vegetation and compacted soils. The area beneath the US 101 bridge is barren with <br /> no riparian vegetation. Construction would avoid wetland vegetation along Redwood Creek except <br /> for approximately 0.01 acres of fragmented tidal salt marsh vegetation at either end of the US 101 <br /> undercrossing. Construction would also require dewatering a 175-foot by 15-foot area below the <br /> MHHW level under the bridge. The contractor would install a temporary cofferdam surrounding the <br /> dewatered area in Redwood Creek,which would prevent construction activity from affecting the <br /> nearby tidal marsh,a sensitive natural community. The City would also implement Best Management <br /> Practices (BMP's) to reduce erosion and sedimentation impacts to Redwood Creek and the tidal <br /> marshes (see the City's NPDES Compliance Checklist Appendix I). The BMPs listed above in <br /> Mitigation Measure BIO 7 include site management practices,restrictions on refueling and use <br /> hazardous materials, and erosion control measures,which would also reduce the potential for project <br /> impacts to tidal salt marsh to less than significant levels. (Less than Significant Impact with <br /> Mitigation Incorporation) <br /> c)Have a substantial adverse effect on federally protected wetlands as defined by Section 404 <br /> of the Clean Water Act(including, but not limited to, marsh, vernal pool, coastal, etc.) <br /> through direct removal, filling,hydrological interruption, or other means? <br /> The project would have temporary and permanent impacts to a small area subject to USACE <br /> jurisdictional as waters of the U.S. The joint-use path and retaining wall would be located on the <br /> creek bank above the ordinary high water mark,and the only permanent facilities within jurisdictional <br /> waters would be one 24-inch pipe for discharge stormwater, either polyvinyl chloride (PVC) or high- <br /> density polyethylene (HDPE) pipe, from the joint-use path and rock slope protection (RSP) below <br /> this pipe. Construction of the project, however,would require access to the bank slope below the <br /> ordinary high water line. The temporary cofferdam would confine the impacts to a small area and <br /> prevent them from affecting the surrounding waters. The location and extent of the temporary and <br /> potential impacts of the project to jurisdictional waters are as follows: <br /> Type of Square <br /> Activity Excavated/ Location Feet Volume Linear <br /> Fill Material (sq ft) (cy) Feet (10 <br /> Temporary Fill/ gravel Creek bank below US 101 875 260 175 <br /> cofferdam bags overcrossing <br /> One permanent Excavation Creek bank below US 101 47 10 14 <br /> stormwater and fill/bank overcrossing <br /> discharge pipe soils <br /> One permanent Fill/ PVC or Creek bank below US 101 2 2 13 <br /> stormwater HDPE pipe overcrossing <br /> discharge pipe <br /> 2-22 US 101 Pedestrian Undercrossing and Bair <br /> Island Road Storm Drain Pump Station Project <br />