0509 presentation to_rwqcb

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0509 presentation to_rwqcb

  1. 1. Sea Water Intrusion in the Los Osos Groundwater Basin Presentation to the Central Coast RWQCB by the Los Osos Water Purveyors
  2. 4. Sand Spit Downtown Creek Upper Aquifer (Zone C) Lower Aquifer (Zone D) Lower Aquifer (Zone E) Bedrock 0 -700
  3. 5. Los Osos Drinking Water <ul><li>Three water suppliers: LOCSD, GSWC, and S&T Mutual </li></ul><ul><li>Much of the upper aquifer is high in nitrates, blending or treatment is required </li></ul><ul><li>The lower aquifer currently supplies 77% of the water delivered by these suppliers </li></ul><ul><li>All pumpers are exceeding the yield of the lower aquifer by over 40% </li></ul>77 % Lower
  4. 6. Lower Aquifer Ground Water Elevations - 2001 Morro Bay Estuary Creek Valley At Sea Level 5’ below 10’ below
  5. 7. Area of Sea Water Intrusion into Lower Aquifer LOCSD Palisades Well
  6. 8. Ocean Sand Spit Downtown Creek Upper Aquifer (C) Lower Aquifer (D) Lower Aquifer (E)
  7. 9. Sea water is the unwanted source in the lower aquifer (values derived from 2002 Seawater Intrusion study) Sea Water Intrusion Upper aquifer leakage Los Osos Creek
  8. 10. Current actions to combat seawater intrusion <ul><li>Purveyors: reduction of water use (pumping) by approximately 15% </li></ul><ul><li>Purveyors: shift in lower aquifer pumping from west to east </li></ul><ul><li>SLO County: retrofit-upon-sale ordinance </li></ul><ul><li>Purveyors: attempting to shift to upper aquifer through blending and nitrate treatment </li></ul>
  9. 11. Results of purveyor actions <ul><li>Sea water intrusion estimated in 2002 study: </li></ul><ul><li>560 acre feet per year </li></ul><ul><li>Current estimated sea water intrusion: </li></ul><ul><li>420 acre feet per year </li></ul>
  10. 12. ISJ Agreement <ul><li>February 2004 - Basin adjudication initiated by LOCSD </li></ul><ul><li>September 2007 - Water Purveyors and the County of SLO entered into an Interlocutory Stipulated Judgment (ISJ) </li></ul><ul><li>August 2008 – ISJ approved by court </li></ul><ul><li>Current – Conducting technical studies & negotiating Basin Management Plan (BMP) </li></ul>
  11. 13. BMP Components <ul><li>Hydrologic assessment of the basin </li></ul><ul><li>Strategy for maximizing reasonable and beneficial use of the basin </li></ul><ul><ul><li>Balancing basin under current development and build-out </li></ul></ul><ul><ul><li>Protect environment influenced by the basin </li></ul></ul><ul><li>Quantification of water rights </li></ul><ul><li>Water conservation goals </li></ul><ul><li>Well abandonment and construction program </li></ul><ul><li>Equitable sharing of costs </li></ul><ul><li>Coordination with LOWWP </li></ul>
  12. 14. Current Work Program <ul><li>Task 1 </li></ul><ul><ul><li>Update steady state hydraulic model </li></ul></ul><ul><ul><li>Adjust build-out projections of the basin water demand, including water conservation </li></ul></ul><ul><ul><li>Preliminary evaluation of nitrate treatment unit </li></ul></ul><ul><ul><li>Assess the potential of the upper aquifer before and after the wastewater project </li></ul></ul><ul><li>Task 2 </li></ul><ul><ul><li>Evaluate and determine creek compartment safe yield </li></ul></ul><ul><ul><li>Perform sampling analysis for water quality of creek compartment </li></ul></ul>
  13. 16. Future Work Program <ul><li>Task 3 </li></ul><ul><ul><li>Prepare Groundwater Basin Infrastructure Master Plan </li></ul></ul><ul><ul><li>Evaluate groundwater recharge opportunities </li></ul></ul><ul><ul><li>Evaluate options for beneficial reuse of reclaimed water </li></ul></ul><ul><ul><li>Prepare a Basin Management Plan </li></ul></ul><ul><li>Task 4 </li></ul><ul><ul><li>Prepare a transient, dual-density hydraulic model of the groundwater basin </li></ul></ul><ul><li>Task 5 </li></ul><ul><ul><li>Annual groundwater monitoring </li></ul></ul><ul><ul><li>Transient model updates every 2 years </li></ul></ul>
  14. 17. Los Osos Wastewater Project <ul><li>Balancing the Los Osos basin will be difficult </li></ul><ul><li>The long term sustainability of the groundwater basin must be a priority for treated effluent produced by the LOWWP </li></ul><ul><ul><li>Quantity: Enact cooperative management agreement to return treated effluent to the groundwater basin </li></ul></ul><ul><ul><li>Quality: Enact cooperative management agreement to address long term management of salt, nutrients and other contaminants </li></ul></ul><ul><li>Potential future hurdles include brine management/disposal and agricultural constraints </li></ul>
  15. 18. Questions?

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