Reso13 PC 13-24 2920 PC Reso-Adopt the Intitial Study MND - Undercrossing

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9 Project Description approxirnatelp 700 feet long and would pass under the US 101 fxeeway bridge between the northern bridge abutment and Redwood Creek. The joint-use path would connect the recendy completed Class I and II bike paths on Bair Island Road to the existing Class iI bike path on Main Street. There would be approximately 9 to10 feet of headspace between the path and the saffit of the bridge. A battexed tieback wall would be implemented on the a�utment side,and a cantilevered xetaining wall would be installed on the creek side of the path. The top porrion of the wa11 between the path and the creek would utilize a 1-foot high metal railing,which would allow passing pedestrians and bicyclists to have views of the creek. Landscaped retaining W�s would extend beyond both entrances to the path under i_TS 101. The base of the path would slope from an elevation of b.9 feet on the east end to 5.8 feet on the west end under US 101. A drainage system would captuxe and detain stotmwater as needed prior to discharge to Redwood Creek through one 24-inch drain pipe. In addition to the 14-foot wide joint-use path,the pxoject aiso includes enhancements on the City- owned patcel south of Convention Way including a 12-foot wide sidewalk,pedestrian lights, landscaping trees along the south side of Convention Way,and a scenic overlook with decorative seating loaking towaxd Redwood Creek. The path would have security access gates at each entrance ta the path and call boxes ]3nl�ed to City dispatch ar 911 at the west and east ends of the underpass. City maintenance staff would close the gates to the path duYing unsafe conditions, such as high water levels or seismic events. The proposed storm drain pump station would consist of two 90-h� submetsible pumps and a low flow pump in a wet well, a concrete vault,an emergency genexator, and interconnecting piping. The 2,900-cubic foat wet well would be appro�matelp 12 feet in diameter and approximately 26-feet deep with a concrete base atop one foot of compacted drain rack. The wet we3l would collect the water from the Bair Island drainage area,and the variable speed pumps woutd be able to discharge a peak flow up to 32.4 cfs. The 5-foot deep concrete vault would contain valves for controlling the flow from each pump. The 250-kW emergencp generator would be housed on an 8 foot by 1Q foot generator pad. A 500-gallon diesel sto�age tank would stote at least a 24-hou�fuel supplp for the standby generator. The pump station would have electrical service and an Advanced Digital Network for the Supervisory Control and Data Acquisirion (SCADA) system to monitor the operation of the pump station system. Ground level access hatches would cover the underground wet well and vault. The pump station would be�oca�ed approximately 130 feet east of the traffic circle on Bair Island Road,nort�of the alignment far the planned Blomquist Street extension. A paved dri�eway fxam Ba.ir Island Road to the new pump station would also be installed. Approxiz�nately 35 3ineax feet of new 42-inch storm drain ductile iron pipe (DIT') would be required to redirect the flow from the e�sting storm drain system within the 22.28-acre Bair Island Road area to the new pump station. Approxirnately 100 linear feet of 24-inch DIP would be used to convey the flow from the new pump station to the existing 24-inch pipe outfall that discharges into Redv�-ood Creek. The point of connection with the exisring drain line would depend on the condirion of the exisring 24-inch pipe. }-; US 10� Pede.rtrian U�tdercros.cirag and Bair Island Stor>Ja Dragm Pump Statinn Project