AEM 2.0 RESULTS MONTEREY SUBBASIN GROUNDWATER SUSTAINABILITY PLAN - PowerPoint PPT Presentation

AEM 2.0 RESULTS MONTEREY SUBBASIN GROUNDWATER SUSTAINABILITY PLAN (GSP) MONTEREY PENINSULA WATER SUPPLY PROJECT (MPSWP) 25 FEBRUARY 2020 PREPARED ON BEHALF OF MARINA COAST WATER DISTRICT

2019 AEM RESULTS MPWSP Monitoring Well ! DWR Groundwater Basins  Provide updated information in MCWD Service Areas Monterey Subbasin regarding location Former Fort Ord of fresh groundwater and extent of salt water intrusion:  Critical to understanding Hydrologic Conceptual Model for preparation of Groundwater Sustainability Plan for Monterey Subbasin (GSP)  Siting of future production wells/potential projects  Identifying critical data needs  Provide updated information regarding distribution of freshwater/saltwater in vicinity of MPWSP 2

Groundwater meeting Beneficial Use Standard (20-75 ohm-m) MPWSP Proposed Slant Well Site 180/400 Foot Aquifer Subbasin Monterey Seaside Subbasin Subbasin 3

CROSS-SECTION LOCATIONS 4

CROSS-SECTION A (Coastline) A A’ 500 Salinas River Perched Shallow Dune Sand Upper 180-Foot / Aquifer Feet above Mean Sea Level Aquifer 180-Foot Aquifer 0 Lower 180-Foot Aquifer -500 400-Foot Aquifer -1,000 0 1,000 2,000 3,000 Groundwater Feet from Beginning of Section meeting Beneficial Use Standard (20-75 ohm-m) 5

CROSS-SECTION B MCWD 180/400 Foot Production Wells (Coastline) B B’ Upper 180-Foot / 500 Dune Sand 180-Foot Aquifer Aquifer Feet above Mean Sea Level 0 Lower 180-Foot Aquifer 400-Foot Aquifer -500 -1,000 0 1,000 2,000 3,000 Groundwater Feet from Beginning of Section meeting Beneficial Use Standard (20-75 ohm-m) 6

CROSS-SECTION C C’ C Salinas River 500 Dune Sand Feet above Mean Sea Level Aquifer 0 Upper 180-Foot / 180-Foot Aquifer Lower 180-Foot Aquifer 400-Foot Aquifer -500 -1,000 0 1,000 2,000 3,000 Groundwater Feet from Beginning of Section meeting Beneficial Use Standard (20-75 ohm-m) 7

VOLUME OF GROUNDWATER MEETING BENEFICIAL USE STANDARDS Aquifer 2019 AEM Survey Volume of Groundwater Meeting Beneficial Use Standards (a) Perched A / Shallow Aquifer (b) 1,000 acre-ft Dune Sand Aquifer 220,000 acre-ft Salinas Valley Aquitard 23,000 acre-ft Upper 180-Foot Aquifer (c) 131,000 acre-ft Intermediate 180 Aquitard 13,000 acre-ft Lower 180-Foot Aquifer 39,000 acre-ft 180-400 Ft Aquitard 4,000 acre-ft 400-Foot Aquifer 7,000 acre-ft 400-Foot Aquitard 1,000 acre-ft TOTAL 438,000 acre-ft a. Beneficial use standard (<3,000 mg/L TDS). Assumes 20% porosity and estimated for the 2017 AEM Survey area. b. The Perched A / Shallow Aquifer only exists north of the Salinas River. c. The Upper 180-Foot Aquifer includes (1) the Upper 180-Foot Aquifer where the Intermediate 180 Aquitard exists, and (2) the entire 8 180-Foot Aquifer elsewhere.

2019 AEM RESULTS/MPWSP  Provide updated information regarding distribution of freshwater/saltwater in vicinity of MPWSP:  Confirm relatively fresh groundwater exists in Dune Sand Aquifer and Upper180-foot Aquifer immediately upgradient of the MPWSP  Consistent with 2017 AEM Results and 2018 Fort Ord TDS Groundwater sampling results  Aid understanding hydrogeologic conditions and potential impacts of MPWSP  Establishes pre-project baseline MPWSP Monitoring Well ! DWR Groundwater Basins ± 0 2 4 (Approximate Scale in Miles) MCWD Service Areas New Fort Ord TDS Data Former Fort Ord 9

2019 COASTAL COMMISSION INDEPENDENT HYDROGEOLOGIC IDENTIFIES POTENTIAL CAPTURE AREA FOR MPWSP Dune Sand Aquifer  Concludes that if the conceptual site model suggested by recent data is accurate:  Slant well fresh water capture area could cover 7 sq miles in the Dune Sand Aquifer where AEM and Fort Ord Data show Fresh Water is present  Recommends additional modeling and data collection Weiss Associates Area with TDS <3,000 mg/L identified by AEM (Source of Drinking Water) Area with TDS <1,000 mg/L Estimated Dune Sand Fresh Water Fort Ord (Source of Drinking Water) Capture Area = 7 Square Miles 10

MODELING WILL ASSESS Upper 180-Foot Aquifer  Quantity of fresh groundwater MPWSP will take from Dune Sand Aquifer  If slant well capture zone will extend into the area where groundwater from Dune Sand recharges Upper 180 foot aquifer zone 11

East Side Subbasin Groundwater meeting Beneficial Langley Sub-basin Use Standard (20-75 ohm-m) 180-400 Ft Aquifer Subbasin Monterey Subbasin Seaside Subbasin MPWSP Site Fresh Water Capture Zone Boundary DRAFT 2019 AEM Resistivity Data (1-75 ohm-m) 2019 Survey Area Full 3D Voxel Depth: Surface to 1,230 ft bgs

Groundwater Meeting Beneficial Use Standard (20-75 ohm-m) Monterey Subbasin MPWSP Site Fresh Water Capture Zone Boundary 2019 AEM Resistivity Data DRAFT 2017 Survey Area Dune Sand Aquifer

Groundwater Meeting Beneficial Use Standard (20-75 ohm-m) Monterey Subbasin MPWSP Site 2019 AEM Resistivity Data DRAFT 2017 Survey Area Upper 180-Foot Aquifer

2 16 35 54 80 Thickness (m) Highway 1 180-400 Ft Aquifer Subbasin Thickness of Groundwater MPWSP Within Dune Sand Aquifer Site With TDS <1,000 mg/L Source: 2019 AEM Resistivity Data Fresh Water Capture Zone Boundary DRAFT Seaside Subbasin Monterey Subbasin

2 16 35 54 80 Thickness (m) Highway 1 180-400 Ft Aquifer Subbasin Thickness of Groundwater MPWSP Within Upper 180-Foot Aquifer Site With TDS <1,000 mg/L Source: 2019 AEM Resistivity Data Monterey Subbasin DRAFT Seaside Subbasin

NEXT STEPS  MCWD has provided AEM data, new Fort Ord TDS data, as well as other information for utilization in Coastal Commission assessment  Coastal Commission-Hydrolgeologist to provide scope of work for completion which will include updated modeling of Project Impacts  AEM Data will be further evaluated and incorporated into GSP 17