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Home My WebLink About04. Lower Walnut Creek Channel Flood Control Project4. LWC Sediment Texture Dredged Area ®- Sediment Texture (2009) Likely extent of 3 1` fluvial sediment silty clay/coarse sand deposition clay/gravel - silty sand CAQUATIC CENTER Source: Hultgren-Tillis Engineers 2009, CCCFC&WCD 2009, SFEI observations 2015 Sediment 1lhansect 95+00 _ p s V N V 0 N j F— HEC -RAS Sta 94+87.588 � � 1962 -Pre Corps Project �n Diked former tidal Marsh a to raw oe t to Io0 0 100 200 ?00 400 Soo 600 700 Source: USACE, 1985: MBK, 2012 HEC -RAS Stationing (ft) _ p s V N V 0 N j F— o � � sediment Transect 95+00 HEC -RAS Sta 94+87.588 30 — 1962 - Pre Corps Project — 1965 - Post Corps Project r _ - - 25 -- — 1972 - Pre -Dredge ---1973 - Post -Dredge (Design) --1995(To"ilb 20 `- 2005 tTowill) s, V. Aw. —2015 (ESA) Long Term? 1s s, n� ------------ 0 gw.ee.s — — - -2110 IOu 0 100 200 300 400 500 600 7W Source: USACE, 1965; MBK, 2012 HEC -RAS Stationing (fu Restoration Increases Channel Conveyance Iuu-R.unmrinn Ic. u..nroxh or la ,nvl ru.,nry e.r.,a„�n rkalniw� I mw .. IKrme�n WUHi L,..1 � ti.ruy.runJI ['.ylv,�y.we /�.uH'k A 1 A• w� faJ-w�wwo �. r.J.n rvnJly A(a nv c=y►" Fluvial flood protection Initial configuration Flood control chaA Source: Environmental Science Associates (ESA) Fluvial flood protection Immediately after construction Water level de reases Floodplain storage and ................................................................ conve ance increase Source: Environmental Science Associates (ESA) 4 Fluvial flood protection Long-term Tidal scour Sea level rise increases increases downstream water levels channel Sedimentation reduces floodplain conveyance conveyance and storage Source: Environmental Science Associates (ESA) Potential IT, FM 172.TZTM Project Measures i Channel - Berm or Levee - -- Central Sanitary Outfall - Poorly Drained Basin c S t District Property DRAFT t•�, For Discussion 5 Pacheco Marsh Existing Conditions t Channel Berm or Levee Central Sanitary Outfall Poorly Drained Basin District Property Project Measures Channel Berm or Levee -•-- Central Sanitary Outfall Poorly Drained Basin District Property Enhance/Restore Habitat Berm/Levee Lowering New Channel DRAFT For Discussion DRAFT For Discussion rel Pacheco Marsh ; Restoration Plan (PWA and HT Harvey, 2004) e +, Lege�a t'` Cut and fill to create tidal marsh, transition zones, and upland habitats Tidal habitat elevations Nletlampiard I I TrasAonal I Hid I Zone j Marsh I MiEke Marsh Extreme HHW MHHW Source: Environmental Science Associates (ESA) Low Marsh MUMM Sup: MHW MLLW +1' ML_:: 7 Ecotone / Upland transition • Aka "horizontal levee" • Sea level rise accommodation • Can be enhanced by beneficial reuse of treated wastewater f Source: Peter Baye Project Measures • Central Sanitary Outfall — continue access and ability to maintain Dutch Slough Sewer Line Relocation FEW TLIL � 1W� IrnMSHpnJl']Ej SEW EN __._ 4EW RM�PHN )� I �P'ISTNC LF'EE NH i NEW MGH UTION .<F£F Mv l t t CW LN¢ 1/ PIPE- SA [ �P \ FEG'RSOM LF VFF MPROVFMf. N'�8 0.�Zr�iY.t[� J Y.CHO MGRB�a CRGGK n• '^�EMKfWG $AYl11h SEWFF Source: Environmental Science Associates (ESA) M. Waterfront Road and UPRR Continue flow path with Channel -- -- Berm or Levee Central Sanitary Outfall Poorly Drained Basin District Property Project Measures G • Continue flow path with bridge, culverts or partial causeway at Waterfront Road • Targeted dredging at UPRR bridge to improve conveyance. compatible with more sustainable geomorphology DRAFT For Discussion Source: Environmental Science Associates (ESA) 721.4-7 1 9 Restoration Measures Channel - Berm or Levee Central Sanitary Outfall Poorly Drained Basin District Property BNSF to Pacheco Creek Area Existing Conditions Channel - - Berm or Levee --- Central Sanitary Outfall Poorly Drained Basin District Property Proposed Conco Yard Expansion t r♦ Proposed Conco Yard Expansion low rte_, l Baker landfill" (hazardous material) ,.., DRAFT For Discussion DRAFT For Discussion 10 BNSF to Pacheco Creek Area Levee Setback on District Property - Channel Berm or Levee - - - - Central Sanitary Outfall Poorly Drained Basin District Property - Enhance/Restore Habitat Berm/Levee Lowering New Channel ,; feVees"y, R ` a sed Conco Yard New. cpansion Be s dosed R Baker Landfill ;. [dous materiao i f Additional Measures • Beneficial re -use of treated wastewater Planting Invasive species management Others? IV] Channel ----- Berm or Levee - - --- Central Sanitary Outtall Poorly Drained Basin District Property DRAFT For Discussion DRAFT For Discussion rp.T...d Sustainability with SLR Inundation Extent Monthly high tides Existing and with SLR Marsh geomorphology Marsh sedimentation will at least partially keep pace with SLR Edge erosion Preliminary 12