Wellhead Protection and Stormwater Recharge in the ... · PDF fileWellhead Protection and Stormwater Recharge in the Washington Portion of the Spokane Valley –Rathdrum Prairie Aquifer
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Wellhead Protection and Stormwater Recharge in the Washington Portion of the Spokane Valley – Rathdrum Prairie Aquifer
Prepared by
John Porcello, LHG and Matt Kohlbecker – GSI Water SolutionsLloyd Brewer and Doug Greenlund – City of Spokane
Prepared for
AWRA 2013 Annual ConferenceSession 82: Groundwater VIII. Artificial Recharge and Resource Evaluation
November 7, 20131
Spokane Valley – Rathdrum Prairie Aquifer
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Source:The Spokane Valley – Rathdrum
Prairie Aquifer Atlas2009 Updatewww.sajb.org
Spokane Valley – Rathdrum Prairie Aquifer
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Source:The Spokane Valley – Rathdrum
Prairie Aquifer Atlas2009 Updatewww.sajb.org
Spokane Valley – Rathdrum Prairie Aquifer
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Source: The Spokane Valley – Rathdrum Prairie Aquifer Atlas 2009 Updatewww.sajb.org
Coeur d’Alene Lake
Hayden Lake
Lake Pend d’Oreille
Spokane River
Newman and Hauser Lakes
Twin Lakes
Fernan Lake
LibertyLake
Little Spokane River
SpokaneRiver
Hangman Creek
Groundwater Elevation Contour Map
Washington Idaho
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0 5 10 MILES
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Topics1. Groundwater modeling as a management tool
Recharge Basin Contribution Inside a Wellhead Protection Area
Goal: Imported Recharge is No More than 20% of Well’s Capture Volume 27
Whitworth Well #2
Recharge Basin
Managing Stormwater and Wellhead Protection
What Are The Effects Of Recharge On:
1. Capture Zone Alignment2. Groundwater Quality
Recharge Basins (large volumes of recharge) Drywells (smaller volumes of recharge)
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Questions from the Wellhead Protection Policy Coordinating Committee
Stormwater Facility
How far away should regional‐scale or local‐scale facilities be sited to avoid water quality impacts to a production well ?
1. What is a desirable separation distance? 2. Does the separation distance affect in‐well water quality?3. Do these answers vary for different pollutants?
‐ Small to moderate amounts of recharge ‐ Unlikely to alter groundwater capture zones‐ Pollutant levels :
‐ Concern is untreated stormwater‐ Some attenuation in subsurface after recharge occurs
‐ Production wells with low pumping are at most risk
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Managing Stormwater and Wellhead Protection
Translation to Policy – Considerations1. Cost of groundwater quality protection
versus impact of losing water supply2. Increasing stormwater management costs3. Effect on the business community of existingversus new regulations
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Managing Stormwater and Wellhead Protection
Translation to Policy – Mechanisms(Draft – In Progress)
1. Adopt special wellhead protection areas (SWPAs)– Formal adoption by SAJB and local land‐use regulators– One‐year capture zone for each production well
2. Communication mechanisms for coordination– Land‐use regulators, stormwater utilities, water purveyors
3. Checks on proposed recharge facilities– Evaluate potential for adverse effects on production wells– Separate requirements inside versus outside SWPAs
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Managing Stormwater and Wellhead Protection
Translation to Policy – Mechanisms(Draft – In Progress)
4. Inside SWPAs:– No new direct injection of untreated stormwater– Injection of BMP‐treated stormwater allowed
(comply with local stormwater management manuals)– Development cannot increase inflows / drainage area
(unless a lack of adverse impact can be demonstrated)– Site injection facilities as far from supply wells as possible
» Within 100 feet: No injection allowed» Within 300 feet: BMP or equivalent treatment
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Managing Stormwater and Wellhead Protection
Translation to Policy – Mechanisms(Draft – In Progress)
5. Outside of SWPAs:Certain conditions require modeling evaluation
– Facilities infiltrating more than 44,000 cubic feet per day (0.5 cfs)
– Facilities directly upgradient of a SWPA that are within the 2‐year time‐of‐travel from the well
– Facilities near the outer boundary of the aquifer– Facilities handling runoff that includes perennial water
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Thank You
John Porcello, Matt Kohlbecker GSI Water Solutions, (503)‐239‐8799
Lloyd Brewer, Doug GreenlundCity of Spokane, (509)‐625‐6968