Presentation of Phase 2 Engineering Report Feasibility Evaluation

Presentation of Phase 2 Engineering Report - Feasibility Evaluation for the Sand City Desalination Project Monterey Peninsula Water Management District March 31, 2004 Presentation: Michael Gray, CDM 1

Presentation Outline n MPWMD Sand City Desalination Project Overview n Phase 2 Evaluation Overview n Findings of Phase 2 Investigation n Questions 2

Sand City Desalination Project Overview n EIR Goal of 7. 5 MGD (8, 400 AFA) Treated Water Production. Up to 10 MGD (11, 000 AFA) Production Assessed Former Ford Ord Sand City Plant Sites Seawater Intake Collector Sites Brine Disposal Sites Seaside 3

Seawater Collection Overview n Seawater Collector Wells – Need 15 MGD seawater for 7. 5 MGD (8, 400 AFA) treated water production – Seawater source is Dune formation onshore or offshore n Collector Well Options – Radial collector well – Offshore horizontal directionally drilled (HDD) collector wells – Onshore HDD collector well 4

Radial Collector Well 5

Offshore HDD Well (Perpendicular to Shoreline) Blind Hole Method of Construction (Single Entry and Exit Point) 6

Offshore HDD Plan View Ocean Beach 7

Onshore HDD Collector Well (Parallel to Shoreline) Ocean Pull Through Method with Separate Entry and Exit Points + 150’ Beach + 2, 500’ 8

Brine Disposal Overview n Two Options Evaluated in EIR – Offshore HDD Disposal Wells at Former Fort Ord l Similar concept/layout as collector wells – Use of Outfall at Regional Wastewater Treatment Plant l Pipeline from plant through former Fort Ord to regional outfall 9

Presentation Outline n Sand City Desalination Project Overview n Phase 2 Evaluation Overview n Findings of Phase 2 Investigation n Questions 10

Phase 2 Evaluation Elements n Prepare Project-Level EIR for Desalination Plant n Conduct Engineering Investigation to Confirm Feasibility and Yields for Collector and Disposal Well Options 11

Phase 2 EIR Evaluation n Project-Level EIR for 7. 5 MGD Sand City Desalination Plant (8, 400 AFA) n Seawater Collector Options – Radial well and offshore HDD collector wells (preferred alternative) evaluated in detail – Onshore HDD well identified as a modified HDD technology option but not evaluated in EIR n Brine Disposal Options – Offshore HDD disposal wells and regional outfall (preferred alternative) evaluated in detail 12

Phase 2 – Engineering Evaluation n Field Investigations to Characterize Onshore and Offshore Conditions n Engineering Evaluation – Interpret field results and assess feasibility – Numerical modeling to assess potential yields n Feasibility Report 13

Phase 2 – Field Investigations n Hydrogeologic Investigation – Constructed four test borings in Sand City & former Fort Ord – Provides detailed hydrogeologic information at specific drilling locations n Geophysical Investigation – Onshore and offshore geophysical methods to characterize seabed bathymetry and subsurface conditions 14

E Area of Investigation A E Offshore Survey Lines Former Ford Ord D D C B C Sand City Onshore Survey Areas Seaside A Test Borings B 15

Presentation Outline n Sand City Desalination Project Overview n Phase 2 Evaluation Overview n Findings of Phase 2 Investigation n Questions 16

Previous Picture of Subsurface n Clay Layer Separating Dune Sand aquifer from Paso Robles Drinking Water Aquifer n Uncertainty in Onshore and Offshore Extent of Dune Sand Aquifer – limited coastal data Sand Dune Sea Level Dune Sand Aquifer ? ? ? Clay Layer Paso Robles (Drinking Water) 17

Revised Picture - Sand City Area n Dune Sand aquifer eroded offshore n Replaced with unconsolidated marine sediments n Suitable for onshore collector n Not suitable for offshore collector Sand Dune Sea Level Dune Sand Aquifer Silt/Sand Marine Sediment Clay Layer Paso Robles (Drinking Water) 18

Revised Picture - Fort Ord n Clay Layer Absent Beneath Former Fort Ord n Onshore collector options feasible n Brine disposal infeasible due to aquifer connection with lower Paso Robles aquifer Sand Dune Sea Level Dune Sand Aquifer Silt/Sand Marine Sediment Paso Robles (Drinking Water) 19

Seawater Intake Options – Radial Wells n Construction Feasible - Land-based operations n Collector Yield: Up to 10 MGD (11, 200 AFA) using intake from four collectors – Supports 5 MGD plant producing 5, 600 AFA treated water n Expansion on former Fort Ord possible to get additional 2, 800 AFA (8, 400 AFA) production or more 20

Seawater Intake Using Offshore HDD n Collection Infeasible at Sand City – Unsuitable drilling conditions with high potential for drilling muds escaping to Monterey Bay – Yield for Offshore HDD not estimated 21

Seawater Intake Options – Onshore HDD n Collection Feasible - Land-based operations, where drilling muds can be contained n Collector Yield: 15 MGD (16, 800 AFA; supports 7. 5 MGD Plant producing 8, 000 AFA) – 2500 -foot long collector – Need additional length or modified configuration to provide 8, 400 AFA year-round n Expansion Beyond 8, 400 AFA Considerations – Extend to north - potential contamination from former landfill? – Construction more complex due to limited beach width 22

Implications for Brine Disposal Using Wells n Offshore HDD Disposal Wells at Former Fort Ord – Technically feasible due to thicker Sand Dunes formation but limited to area beneath dunes – Potentially institutionally infeasible -- brine disposal in aquifer connected to drinking water aquifer n Brine disposal through regional outfall best option (possibly only option) 23

Summary n Onshore HDD well at Sand City plant production of 8, 000 AFA – Expansion on Fort Ord or re-configuration needed to get 8, 400 AFA firm capacity or more n Radial wells in Sand City plant production of up to 5, 600 AFA – Expansion on Fort Ord to get 8, 400 AFA firm capacity or more 24

Summary - Continued n Expansion to 10 MGD (11, 000 AFA) would require hybrid Project with combination onshore HDD and radial wells or onshore HDD wells n Brine discharge likely limited to single option using outfall at regional wastewater treatment facility 25

Next Steps n District Staff to review CDM final report n Submit report based on District review in mid-April 26

Presentation Outline n Sand City Desalination Project Overview n Phase 2 Evaluation Overview n Findings of Phase 2 Investigation n Questions 27