SAN ANSELMO FLOOD RISK REDUCTION PROJECT UPDATE

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1 SAN ANSELMO FLOOD RISK REDUCTION PROJECT UPDATE RossValleyWatershed.org Contact us: SAN ANSELMO TOWN COUNCIL MEETING 9/26/17

2 SAN ANSELMO FLOOD RISK REDUCTION PROJECT Agenda 1. San Anselmo Project Nursery 3000 SFD Blvd + Removal of Building at San Anselmo Avenue 2. Hydraulic Modeling Results 3. Project Update including Environmental Review San Anselmo Flood Risk Reduction Project September 26, 2017 Slide 2

3 San Anselmo Flood Risk Reduction Project Flood Diversion 3000 SFD Blvd- Fairfax Removal of Building at 634 San Anselmo Avenue Flood flow barriers Creek enhancement

4 Ross Valley Flood and Watershed Project Timeline Today Corte Madera Creek Flood Risk Management Project (US Army Corps) Corte Madera Creek Flood Risk Management Project Phase 1 San Anselmo Flood Risk Reduction Project Lower Corte Madera Creek Improvements (Phoenix Lake Grant Migration) Azalea Ave. Bridge Madrone Ave. Bridge Nokomis Ave. Bridge Winship Ave. Bridge Projects with Multiple Flood Reduction Elements Bridge Replacements and/or Modifications Environmental Review Complete Bridge Ave & Sycamore Ave./Center Blvd. Bridges

5 Peak Discharges at Ross Creek Gage San Anselmo Flood Risk Reduction Project September 26, 2017 Slide 5

6 Review of Hydraulic Modeling Maps 2 - DIMENSIONAL MODEL SHOWING FLOW IN CREEKS AND FLOODPLAINS

7 10 year flood event video EXISTING CONDITIONS VS WITH PROPOSED PROJECT

8 CHANGE IN HEC-RAS-SIMULATED INUNDATION EXTENT AND DEPTH BETWEEN SAN ANSELMO PROJECT AND EXISTING CONDITIONS FOR 10-YEAR FLOOD DOWNTOWN SAN ANSELMO AREA (UPPER) Summary of Results Any Flooding Increase downstream? Area in blue no longer floods during 10-year event Proposed project reduces depth of flooding by up to 2.1 ft. None shown in San Anselmo 8

9 CHANGE IN HEC-RAS-SIMULATED INUNDATION EXTENT AND DEPTH BETWEEN SAN ANSELMO PROJECT AND EXISTING CONDITIONS FOR 25- YEAR FLOOD DOWNTOWN SAN ANSELMO AREA (UPPER) Summary of Results Reduces inundation depth by up to 0.6 ft or 7.2 Any Flooding Increase Downstream? Limited near the Winship Bridge

10 CHANGE IN HEC-RAS-SIMULATED INUNDATION EXTENT AND DEPTH BETWEEN SAN ANSELMO PROJECT+ BRIDGES AND EXISTING CONDITIONS FOR 25-YEAR FLOOD DOWNTOWN SAN ANSELMO AREA (UPPER) Summary of Results Any Flooding Increase downstream? Reduces inundation extent by 26% Reduces inundation depth by up to 1.0 ft None

11 CHANGE IN HEC-RAS-SIMULATED INUNDATION EXTENT AND DEPTH BETWEEN SAN ANSELMO PROJECT AND EXISTING CONDITIONS FOR 10-YEAR FLOOD-Lower SAN ANSELMO AREA Summary of Results Nearly eliminates 10-year flooding in downtown San Anselmo None Any Flooding Increase?

12 CHANGE IN HEC-RAS-SIMULATED INUNDATION EXTENT AND DEPTH BETWEEN SAN ANSELMO PROJECT AND EXISTING CONDITIONS FOR 25-YEAR FLOOD-Lower SAN ANSELMO AREA Summary of Results Reduces inundation depth by up to 0.5 ft Any Flooding Increase? Slightly increases flood water elevations in the area between Winship and Barber Bridges

13 CHANGE IN HEC-RAS-SIMULATED INUNDATION EXTENT AND DEPTH BETWEEN SAN ANSELMO PROJECT+ BRIDGES AND EXISTING CONDITIONS FOR 25-YEAR FLOOD DOWNTOWN SAN ANSELMO AREA (Lower) Summary of Results Any Flooding Increase? Reduces inundation depth by up to 0.7 ft Limited just downstream of Winship Bridge

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16 634 San Anselmo Avenue-Open for Business UPDATE The Marin County Board of Supervisors approved an option to purchase the building at 634 San Anselmo Avenue for $1.75 million. Option to purchase contingent upon EIR being approved in Spring 2018 Businesses in downtown San Anselmo are operating as normal and will continue to do so for the foreseeable future. If businesses are required to move for the project, the District will provide ongoing financial and advisory assistance to the businesses to help with the move and set up in a new location. Every effort will be made to help those businesses who wish to remain in San Anselmo to find available commercial spaces in the Town - wherever possible. District staff will keep the public and business owners fully informed about the project on a regular basis. San Anselmo Flood Risk Reduction Project September 26, 2017 Slide 16

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18 San Anselmo Flood Risk Reduction Project Proposed view from corner of Tamalpais and San Anselmo Avenue Blasen Landscape Architecture

19 Oct 2016 San Anselmo Project Timeline Phase 1 Memorandum of Agreement between San Anselmo and District approved to perform CEQA and Feasibility Engineering Apr 20, 2017 Dec 17/Jan 2018 Project EIR Public Scoping Meeting Public Draft EIR Release-45 day review/comment period Apr 2018 Apr 2018 Apr 2018 Jan 2019 Dec 2020 Final Project EIR Public Hearing Final EIR certification at Board of Supervisors meeting (merits project approval meeting) Finalize design work for San Anselmo Project, secure permits, possible property acquisition and business relocation activities. Community outreach continues. Construction begins (planning for construction in either 2019 or 2020). Outreach continues during construction. Construction completed. Community outreach continues

20 Stakeholder and Community Input MEETINGS TO LEARN ABOUT PRELIMINARY DESIGN AND GATHER FEEDBACK Fairfax Town Council September 6 San Anselmo Town Council-Sept. 26 Ross Town Council-Oct 10 Flood Zone 9 Advisory board meeting-dec. 19 Draft EIR Public Hearing Jan San Anselmo Flood Risk Reduction Project September 26, 2017 Slide 20

21 Thank You! Rossvalleywatershed.org