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
N
Topics1. Groundwater modeling as a management tool
– Delineating wellhead protection management areas– Evaluating public stormwater recharge projects
2. Conjunctively managing stormwater rechargeand groundwater quality– Regional facilities– Site‐scale facilities
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Wellhead protection areas delineated for production wells located in the Washington
portion of the SVRP aquifer(with model grid mesh in black)
State Line
Entities Involved• Spokane Aquifer Joint Board
– Consortium of 18 municipal water providers and 3 industries– Leads wellhead protection program
• Wellhead Protection Policy Coordinating Committee– Municipal planners, stormwater utilities, water providers
• Informal group facilitated by City of Spokane
– Purpose:• Obtain consistency in aquifer protection regulations• Raise public awareness, provide more certainty to the regulated public
– Focus:• Stormwater, reclaimed water, high‐risk land use activities
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Funding Provided By:
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Groundwater Model Objectives and Uses
A high‐resolution tool1. Support wellhead protection program2. Support other groundwater analyses
– Regional scale (resource management)– Local scale (wells, recharge facilities)
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¼ mile
2C 2B 2A
Bi‐State Model Square Grid Cells (Black)(MODFLOW)
(Finite‐Difference)
City/SAJB Model Flexible Mesh (Blue)
(MicroFEM®)(Finite‐Element)
Finite‐Element and Finite‐Difference Grids (Production Wellfield CID‐2)
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¼ mile
4A 4B 4C4D
CID‐4 Monitoring
Well
Finite‐Element and Finite‐Difference Grids (Production Wellfield CID‐4)
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Chester Creek Recharge Basins
Model ID #3
Model ID #7
WD#3 Browns Park
Modern Electric #9
Model ID #5
Model ID #1 and #6
WD#3 20th & Balfour
Finite‐Element and Finite‐Difference Grids (Wells and Recharge Basins)
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Drawdown Cones at Parkwater and Well Electric
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Well Electric (39,300 gpm)(375 ft from River)
Parkwater(63,000 gpm)(1,800 ft from River)
Flow Patterns at Parkwater and Well Electric
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Well Electric (39,300 gpm)(375 ft from River)
Parkwater(63,000 gpm)(1,800 ft from River)
Outside the Parkwater “Well House”
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Inside the Parkwater “Well House”
Two of Eight Pumps For This “Well” 16
Inside the “Well Electric” Pump StationOne 40‐Foot‐Diameter Well Down This Opening
Another 40‐Foot‐Diameter Well Down This Opening
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Water Table in Cross‐Sectional View
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ParkwaterDrawdown
Cone
Spokane River
Well Electric (39,300 gpm)(375 ft from River)
Parkwater(63,000 gpm)(1,800 ft from River)
Three‐Dimensional Groundwater Flowpaths (Plan View)
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Well Electric (39,300 gpm)(375 ft from River)
Parkwater(63,000 gpm)(1,800 ft from River)
Three‐Dimensional Groundwater Flowpaths (Cross‐Sectional View)
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Well Electric Parkwater
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Well Electric (39,300 gpm)
Parkwater(63,000 gpm)
Wellhead Protection Areas (Model View)
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0 5 10MILES N
Washington Idaho
Wellhead Protection Areas (GIS View)
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Managing Stormwater and Wellhead Protection
What Are The Effects Of Recharge On:
1. Capture Zone Alignment2. Groundwater Quality
Basins (large volumes of recharge) Drywells (smaller volumes of recharge)
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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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Effect of Recharging Seasonal Tributary Inflows from Adjoining Uplands
Chester Creek Recharge Basins Saltese Flats /
Shelly Lake Recharge Basin
Carnhope
WD3 Freeway
WD3 Boone & Lilly
HID 1&2
ESWD 3&4
Tributary Inflows at Aquifer Margins
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Yellow = No Tributary Inflow Recharge (Late Summer)Red = Peak Tributary Inflow Recharge (Spring)
Recharge Basin in North Spokane
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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?
WELL
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Answers
Greatest concern: First‐flush events (after extended dry periods)
‐ 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
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