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September Ranch Subdivision Project Water Supply & Availability Final EIR July 2006

September Ranch Subdivision Project Water Supply & Availability Final EIR July 2006. Leslie L. Chau Kennedy/Jenks Consultants 26 July 2006. EIR Conclusions. The September Ranch (SRA) and Carmel Valley Aquifers (CVA) appear to be two separate aquifers.

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September Ranch Subdivision Project Water Supply & Availability Final EIR July 2006

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  1. September Ranch Subdivision ProjectWater Supply & AvailabilityFinal EIR July 2006 Leslie L. ChauKennedy/Jenks Consultants 26 July 2006

  2. EIR Conclusions • The September Ranch (SRA) and Carmel Valley Aquifers (CVA) appear to be two separate aquifers. • The westernmost 35% of the SRA is classified as co-located with a small wedge of CVA Subunit 3. • The SRA is hydraulic connected to the CVA but has limited groundwater exchange with the CVA • Limited groundwater exchange is inferred with evidence of: A) low permeability barrier at the western end of the SRA; and B) separate sources of recharge. • No groundwater exchange with below normal rainfall • The two aquifers appear to be efficient in recharge during extended drought periods.

  3. Reduction of groundwater exchange during extended dry periods(e.g. 1987 to 1991) - EIR Conclusion • 270 AF over five years – based on 57.21 Acre-feet per year of proposed Project usage • 71.5 AF over 19 months – based on recoveries of groundwater levels in the Carmel Valley, 1987 to 1991 • Zero or “very little” groundwater exchange – based on separate sources of recharge and neutral groundwater gradient

  4. September Ranch and the Carmel Valley Aquifer Subunits

  5. September Ranch Watershed and Drainage Patterns

  6. September Ranch Aquifer Surface Impression Source: Kleinfelder 2004

  7. Top of Bedrock (Monterey Shale Tm) SR Aquifer Source: Kleinfelder 2004

  8. Top of Older Alluvium (Qoa2) SR Aquifer Source: Kleinfelder 2004

  9. Older Alluvium (Qoa2) Subsurface Extent SR Aquifer Source: Kleinfelder 2004

  10. Extent of Alluviums (Qoa1 & Qoa2) SR Aquifer K= 28 gpd/f2 K=1.4 – 0.14 gpd/f2 K= 0.17 gpd/f2

  11. Water Levels in September Ranch Aquifer Water Wells Source: September Ranch Project, 2004

  12. September Ranch Groundwater Gradient or flow into the CVA (across M-M’), during normal rainfall and below normal precipitation periods.

  13. Data from Water Wells Used in this Analysis Source: Monterey County Water Resources Agency, 2004

  14. Water Levels in Carmel Valley Water Wells Source: Monterey County Water Resources Agency, 2004

  15. Reduction of groundwater exchange during extended dry periods(e.g. 1987 to 1991) - EIR Conclusion • 270 AF over five years – based on 57.21 Acre-feet per year of proposed Project usage • 71.5 AF over 19 months – based on recoveries of groundwater levels in the Carmel Valley, 1987 to 1991 • Zero or “very little” groundwater exchange – based on separate sources of recharge and neutral groundwater gradient

  16. Conclusions Revisited • The September Ranch (SRA) and Carmel Valley Aquifers (CVA) appear to be two separate aquifers. • The westernmost 35% of the SRA is classified as co-located with a small wedge of CVA Subunit 3. • The SRA is hydraulic connected to the CVA but has limited groundwater exchange with the CVA • Limited groundwater exchange is inferred with evidence of: A) low permeability barrier at the western end of the SRA; and B) independent sources of recharge. • No groundwater exchange with below normal rainfall • The two aquifers appear to be efficient in recharge during extended drought periods.

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