1. B AINBRIDGE I SLAND ’ S A QUIFER S YSTEM J UNE 18, 2015 Cami Apfelbeck, M.S. Geological Sciences Groundwater Management Program Manager 1

2. T HE A QUIFER S YSTEM Perched Aquifer-Qva (4% wells – domestic) Semi-Perched Aquifer-QC1i (25% wells - domestic) Sea Level Aquifer-QA1 (53% wells – domestic & production) Glacio-marine Aquifer-QA2 (2% wells – production) Fletcher Bay Aquifer-QA3 (1% wells – production) Bedrock Aquifer-BR (<1% wells – domestic) 6/18/15 2 ( Conceptual Model and Numerical Simulation of the Groundwater-Flow system of Bainbridge Island, Washington, USGS, 2011)

3. S OLE S OURCE A QUIFER D ESIGNATION Federal Program (EPA) ( Safe Drinking Water Act 1974) Supplies at Least 50% of the drinking water No Alternative Sources (Physically, legally, and economically) 6/18/15 3 Sole Source Aquifer Program  Section 1424(e) definition “…the sole or principal drinking water source for the area and which, if contaminated, would create a significant hazard to public health.”  EPA definition  Supplies at least 50% of the drinking water consumed in the area  No alternative drinking water source(s) which could physically, legally, and economically supply all those who depend upon the aquifer  Federal (EPA) program authorized under the Safe Drinking Water Act of 1974

4. S OLE S OURCE A QUIFER D ESIGNATION Protects Water Quality Promotes Awareness EPA Review of Federally- funded Projects 6/18/15 4 Sole Source Aquifer Designation  Protective measures  Designed to protect water quality – prevent contamination of the aquifer system from overlying land use  Promotes education and awareness about drinking water supply vulnerability and our dependence upon it  Requires additional EPA scrutiny of federally-funded projects (but only federally-funded projects)

5. S OLE S OURCE A QUIFER D ESIGNATION Does not Exempt from Growth Management Act Provides Limited Protection 6/18/15 5 Sole Source Aquifer Designation  Provides limited protection  Does not exempt from Growth Management Act  Not a comprehensive groundwater protection program  Use in conjunction with local wellhead protection and contaminant source control and pollution prevention  Other protective measures  Designating critical aquifer recharge areas as Conservation Areas  Developing multi-stakeholder Islandwide Groundwater Management Plan (includes Water Conservation Plan)

6. S EAWATER I NTRUSION Some Aquifers have Contact with Saline/Marine Water (Puget Sound is saltwater) Freshwater less dense than saltwater (Freshwater “floats” on top of saltwater) Zone of Diffusion/Zone of Mixing (Freshwater/Saltwater Interface) Recharge, flow, mixing, and discharge holds Zone of Diffusion in Stationary Position (Significant change in any of these parameters can cause Lateral Seawater Intrusion.) 6/18/15 6 ( Seawater Intrusion Topic Paper, WRIA 6 Watershed Planning Process, Island County, Washington, 2005)

7. S EAWATER I NTRUSION Drawdown Cone (Pumping lowers water levels near the well.) Upconing (Under pumping conditions, the saltwater/freshwa ter interface will rise up toward the well screen.) 6/18/15 7 ( Seawater Intrusion Topic Paper, WRIA 6 Watershed Planning Process, Island County, Washington, 2005)

8. G ROUNDWATER M ANAGEMENT PROGRAM Monitoring Network Early Warning Levels (EWLs) Management Responses Recommendations 6/18/15 8

9. C URRENT A CTIVITIES Monthly Groundwater Level Measurements Annual Chloride Sampling Aquifer System Modelling Reporting 6/18/15 9  Monthly groundwater level measurements  46 public and private wells Islandwide  All six aquifers  EWL – >½ foot water level decline per year over 10 years  Annual chloride sampling  ~30 public and private wells  Aquifers and wells susceptible to seawater intrusion  EWL - >100 mg/L or any 4 consecutive samples showing an increasing trend Groundwater Management Program

10. C URRENT A CTIVITIES Monthly Groundwater Level Measurements Annual Chloride Sampling Aquifer System Modelling Reporting 6/18/15 10  Aquifer system modelling  Periodically re-assess/modify the model to fit current needs  Recalibrate and utilize Groundwater Management Program

11. C URRENT A CTIVITIES Monthly Groundwater Level Measurements Annual Chloride Sampling Aquifer System Modelling Reporting 6/18/15 11  Reporting  Summaries of water level monitoring and chloride sampling results  Program updates/technical memorandums  Website updates/Water Resources listserv  Education/outreach Groundwater Management Program

12. W ORK IN P ROGRESS Data assessment Model Evaluation Model Improvements Model Recalibration Model Utilization 6/18/15 12  In-depth hydrogeologic assessment of recent monitoring data against EWLs  Model evaluation  Assess model design  Identify potential improvements  Implement necessary improvements  Recalibrate the model  Run the model in support of Comp Plan Update and Water Utility Management Groundwater Management Program

13. T HANK YOU 6/18/15 13