Design Oversight Committee March 17, 2017 1 Agenda 1. Welcome and - PowerPoint PPT Presentation

Design Oversight Committee March 17, 2017 1

Agenda 1. Welcome and Introductions - Tully 2. Meeting Purpose - Sam 3. Report Summary - Peter Dam Removal Concepts • Water Supply Mitigation Options • 4. Project Funding and Project Completion Pathways – Sam 5. Dam Removal Concept Discussion and Selection - Peter 6. Next Steps – Tully 7. Closing - Tully 2 of 34

Dam Removal Concepts Evaluation 3 of 34

Background • Contract Management Team – VCWPD – CMWD – NOAA – SCC – Surfrider – BOR 4 of 34

Dam Removal Concept Descriptions Six Initial Options narrowed down to three alternatives during the September 2014 Design Oversight Group/Technical Advisory Committee Meeting The Three Short-listed Dam Removal Concepts (DRCs) 1. DRC-1: Containment Berm with High Flow Bypass 2. DRC-2: Uncontrolled Orifices with Optional Gates 3. DRC-3: Temporary Upstream Storage of Sediment 5 of 34

DRC-1: Containment Berm with High Flow Bypass Overview: Bypass storms less than flushing storm of Flow bypass system • 3,000 cfs peak (1,700 around reservoir fine cfs average daily flow) sediment (tunnel + cofferdam) Temporary • containment berm downstream of the dam Single-phase dam • removal Minimal sediment • handling 6 of 34

DRC-1: Containment Berm with High Flow Bypass 7 of 34

DRC-1: Containment Berm with High Flow Bypass Construction Cost Project Categories (2015) Low (-30%) High (+50%) Mobilization $3,500,000 Site Preparation $11,800,000 Sediment Components $0 Slurry System Components $0 Dam Removal Components $9,200,000 Site Restoration $2,500,000 Subtotal $27,000,000 Contingency (30%) $8,100,000 Subtotal $35,100,000 Construction Contingency (15%) $5,300,000 Total $40,400,000 $28,300,000 $60,600,000 0 to 3-year waiting period • Resulting in 3 to 6-year construction • schedule 8 of 34

DRC-2: Uncontrolled Orifices with Optional Gates Overview: Construct IO-02 • Installation of • gates, as needed Dam Removal • 9 of 34

DRC-2: Uncontrolled Orifices with Optional Gates 10 of 34

DRC-2: Uncontrolled Orifices with Optional Gates ( 2A – no gates) Construction Cost Project Categories (2015) Low (-30%) High (+50%) Mobilization $1,600,000 Site Preparation $900,000 Sediment Components $0 Slurry System Components $0 Dam Removal Components $8,000,000 Site Restoration 1,900,000 Subtotal $12,400,000 Contingency (30%) $3,700,000 Subtotal $16,100,000 Construction Contingency (15%) $2,400,000 Total $18,500,000 $13,000,000 $27,800,000 Note – The ROM construction cost of each additional orifice would be $1,000,000. 0 to 3-year waiting period • Resulting in 2 to 5-year construction • schedule 11 of 34

DRC-2: Uncontrolled Orifices with Optional Gates ( 2B – add gates) Construction Cost Project Categories (2015) Low (-30%) High (+50%) Mobilization $1,800,000 Site Preparation $1,900,000 Sediment Components $0 Slurry System Components $0 Dam Removal Components $8,000,000 Site Restoration 1,900,000 Subtotal $13,600,000 Contingency (30%) $4,100,000 Subtotal $17,700,000 Construction Contingency (15%) $2,700,000 Total $20,400,000 $14,300,000 $30,600,000 Note – The ROM construction cost of each additional orifice with gate would be $2,100,000. Two 0 to 3-year waiting period • Resulting in 3 to 9-year construction • schedule 12 of 34

DRC-3: Temporary Upstream Storage of Sediment Overview: Excavate channel • (1.6M CY) Disposal material • placement (1.6M CY) Removal of dam • 13 of 34

DRC-3: Temporary Upstream Storage of Sediment 14 of 34

DRC-3: Temporary Upstream Storage of Sediment 15 of 34

DRC-3: Temporary Upstream Storage of Sediment Construction Cost Project Categories (2015) Low (-30%) High (+50%) Mobilization $4,400,000 Site Preparation $3,600,000 Sediment Components $15,000,000 Slurry System Components $0 Dam Removal Components $8,000,000 Site Restoration $2,200,000 Subtotal $33,200,000 Contingency (30%) $10,000,000 Subtotal $43,200,000 Construction Contingency (15%) $6,500,000 Total $49,700,000 $34,800,000 $74,500,000 16 of 34

Dam Removal Concepts Evaluation Evaluation Summary 17 of 34

Evaluation Summary Evaluation Criteria: Evaluation Category Evaluation Criteria Description A. Biological Resources Steelhead Passage Time to reach steelhead passage through dam/reservoir area Steelhead Health Scale of severity of impacts for suspended sediment to steelhead Ecological Health Acres of vegetation communities impacted by actions at dam/reservoir Ecological Health Acres of future vegetation communities within reservoir area of impact B. Technical & Implementation ROM Construction Cost Rough Order of Magnitude Construction Cost Risk Management Flexibility to manage risk and react to unanticipated conditions C. Sediment Transport & Water Quality Water Supply Wet cycle percent reduction in Lake Casitas water storage levels Water Supply Dry cycle percent reduction in Lake Casitas water storage levels 18 of 34

Evaluation Summary Steelhead Passage: Dam Removal Concept Implementation Duration (years) 1. Construction Duration DRC-1 3 to 6 2. Flush Waiting Period DRC-2A/B 2 to 5 / 3 to 9 DRC-3 2 to 5 3. Post-Flush Passage Establishment 19 of 34

Evaluation Summary Steelhead Health: Dam Removal Concept Phase I Severity Score 1. Function of magnitude and duration DRC-1 13 DRC-2A 13 of TSS during Phase I and II erosion DRC-2B 13, but second flush possible with gate DRC-3 minimal Fish Response to Suspended Sediments for Adult Salmonids (using the empirically generated model of Newcombe and Jensen, 1996) 20 of 34

Evaluation Summary Ecological Health Impact: Impacts (acres) Vegetation Community DRC-1 DRC-2 DRC-3 1. Acres of existing vegetation Mixed Chaparral 0.6 0.4 1.3 Freshwater Marsh 1.9 1.6 2.5 communities impacted by project Oak Woodland 1.0 0.0 3.5 Riparian Scrub 7.2 5.7 15.5 Riparian Woodland 14.2 12.0 37.0 Coastal Sage Scrub 0.5 0.2 2.1 Total 25.5 19.6 69.0 21 of 34

Evaluation Summary Ecological Health Benefit: DRC-1 DRC-2 DRC-3 1. Acres of proposed Vegetation community (acres) (acres) (acres) Herbaceous Riparian 7.4 7.4 7.9 vegetation communities Riparian Scrub 17.5 17.5 15.8 Riparian Woodland 26.3 26.3 14.4 (riparian of highest Oak Woodland 21.5 21.5 28.9 Coastal Sage Scrub 59.2 59.2 53.6 value) Mixed Chaparral 22.1 22.1 39.3 Total 154.0 154.0 159.9 22 of 34

Evaluation Summary ROM Construction Cost: • Alt. 4B (2015) cost is approximately $113,000,000 – not including downstream improvements – other costs (engineering, admin & legal, construction management, operations and maintenance, etc.) Range of Magnitude Construction Cost (ROMCC) DCR (-30%) Estimate (+50%) $28,300,000 $40,400,000 $60,600,000 DRC-1 3 $13,000,000 $18,500,000 $27,800,000 DRC-2A 1 DRC-2B $14,300,000 $20,400,000 $30,600,000 2 DRC-3 $34,800,000 $49,700,000 $74,500,000 4 23 of 34

Evaluation Summary 24 of 34

Evaluation Summary Key Points: DRC-2 (without gate) ranks first overall, primarily due to having the lowest cost, • risk, and impact to existing vegetation. In addition, it does not rank last in any category. Gate could be added as a contingency measure (to adaptively manage fine sediment), given considerations from evaluation (potential for subsequent temporary impact to aquatic health) DRC-3 ranks second, with its high impact to existing vegetation (large footprint), • high cost and lower long-term vegetation habitat benefit, pulling it below DRC-2 in overall score. DRC-1 ranks third given the selected criteria, primarily due to the fact that it • only ranks first in one of the criteria, generally failing to significantly differentiate itself from the other concepts, but carrying the greatest risk and relatively high cost. 25 of 34

Water Supply Mitigation Concepts Evaluation 26 of 34

Mitigation Options Mitigation Options Selection • A total of 23 different options were evaluated • Options were grouped into four categories: – Diversion Replacement – Replacement Supplies – Re-use & Conservation – Treatment Alternatives • Evaluated based on cost, environmental, technical feasibility, and adaptability considerations • 8 options are being recommended for further analysis 27 of 34