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2021.04.05_YMCA_Mineral_Lake_Pumping_Test_Methods_and_Results MEMORANDUM Project No. 190559 March 1, 2020 To: Meredith Cambre, YMCA of Seattle From: Matthew M. Lewis, LHG Project Hydrogeologist mlewis@aspectconsulting.com Jill Van Hulle, CWRE Associate Water Rights Specialist jvanhulle@aspectconsulting.com Re: YMCA: Mineral Lake Pumping Test Methods and Results An existing well (Well 1) on the YMCA property was tested by Aspect Consulting, LLC (Aspect) to assess aquifer feasibility in supplying future water needs for the camp. The testing supports Lewis County Department of Environmental Health source approval and the Washington State Department of Ecology (Ecology) water right permitting. This technical memo details the field methods, data analysis, and findings from the aquifer testing. Aquifer Characterization Well 1 is in the NW ¼ NE ¼ Section 4, Township 14 N., Range 5 E.W.M (Ecology ID BBN-866; see Figure 1). Based on review of the Ecology well log, the well is 249 feet deep and interpreted to be completed in a fractured bedrock aquifer. A 6-inch-diameter steel casing extends from the surface to 54 feet below ground surface (bgs). A 4-inch-diameter PVC liner was installed from 29 to 249 feet bgs with perforations between 239 and 249 feet bgs. The static water level was reported at 26 ft bgs at the time of completion in June 2010. The well log is included as Attachment A. A step-rate pumping test was conducted by an Aspect hydrogeologist to estimate aquifer parameters and assess the efficiency of the well. The testing method, analysis, and results are described below. Test Procedure Aquifer testing at each well included installing a 3-inch-diameter Grundfos submersible pump and a downhole pressure transducer to monitor and record water levels. Prior to testing, the test well earth +w ater Aspect Consulting, LLC 710 2nd Avenue Suite 550 Seattle, WA 98104 206.328.7443 www.aspectconsulting.com YMCA of Seattle MEMORANDUM March 1, 2021 Project No. 190559 Page 2 was initially sounded to establish static depth to groundwater before placing the pressure transducer and pump near the bottom of the well (within the well screen). After stabilization of the groundwater level (from the displacement of the pressure transducer and pump), the pump was started and the pumping rate adjusted to produce a continuous flow. Water produced during pumping was discharged 400 feet away from the well to avoid potential interference. The pressure transducer monitored and recorded drawdown during pumping and a totalizing flow meter was read periodically to determine pumping rates. The pump discharge line was equipped with a check valve to prevent water from flowing back down the line and into the well after pump shut-off. Manual water level measurements were also collected using a sounding tape and recorded on field sheets. Once water levels in the well stabilized on the final step, the pump was stopped, and water level recovery was recorded by the pressure transducer. However, the transducer cable was severed during pump removal and was not able to be retrieved from the well. Therefore, manual water level measurements were relied upon for aquifer analysis. Once the groundwater level was nearly fully recovered to static pre-test conditions, the pump and testing equipment were removed from the well. Pumping rates were gradually increased in four steps: 7.8 gallons per minute (gpm), 11.2 gpm, 15.5 gpm, and the final step at 19.3 gpm. The water level drawdown at the end of the test was 19.5 ft below static after about 4 hours of pumping. Each step lasted between 35 minutes and 2 hours to ensure stabilization before moving to the next step. A hydrograph for the test is shown as Figure 2. A pressure transducer was also installed in the closest nearby well about 350 feet southwest to evaluate aquifer response. No response was noted in the observation well during pumping; this is consistent with the low yield of the test well and suggests low transmissivity (the ability of the aquifer to transmit water per unit width) within the aquifer. Test Results The Cooper-Jacob method (1946) was used to analyze drawdown data from the final step of the pumping test, as shown on Figure 3. Aquifer transmissivity was estimated to be about 310 square feet per day (ft2/d), which is consistent with the lithology described in the well log. Well efficiency and long-term drawdown was estimated by applying the well and aquifer metrics described in the preceding sections to the Theis equation (Krusemann and de Ridder, 2001). Specific capacity is a measure of the pumping rate (gpm) divided by the drawdown measured after continuously pumping for a certain period (often 30 minutes) and is a useful metric for estimating the capacity of a well. The specific capacity and well efficiency estimates are presented in Table 1. Table 1. Step-Rate Test Summary of Results Step # Pumping Rate (gpm) Drawdown (feet) Specific Capacity (gpm/ft) Well Efficiency (%) 1 7.8 5.5 1.4 69% 2 11.2 8.5 1.3 61% 3 15.5 13.8 1.1 53% 4 19.3 19.5 1.0 48% YMCA of Seattle MEMORANDUM March 1, 2021 Project No. 190559 Page 3 Estimated water levels during long-term continuous pumping at the test well is shown on Figure 4. The predicted drawdown for the test well assumes that the well screen remains fully saturated and that pump assemblies are not installed within the screen assemblies in a manner that restricts flow. The drawdown from pumping at 40 gpm is predicted to be approximately 79 feet, which places the pumping level at about 100 feet bgs. This leaves about 100 feet above the assumed pump intake, suggesting that the well has some additional capacity not utilized in this pumping test. However, pumping this additional capacity may be limited by the 4-inch-diameter liner in the well which restricts the size of pump that may be installed. For the primary Phase 1 buildout of the camp, the YMCA assumes water will be required for 500 people (400 campers and 100 staff members.) If an average demand of 45 gallons per day (gpd) is assumed per person, a total of 22,500 gpd will be needed. A constant pumping rate of 40 gpm (or up to 58,000 gpd) from the well will provide sufficient supply for the camp at the Phase 1 buildout. Based on our evaluation of the site, and assuming the wells are sufficiently spaced, we anticipate that any additional wells needed for the project can be expected to produce similar quantities as the camp continues to expand into full buildout. References Cooper, H.H. and C.E. Jacob, 1946, A Generalized Graphical Method for Evaluating Formation Constants and Summarizing Wellfield History, Am. Geophys. Union Trans., Vol. 27, pp 526-534. Kruseman, G.P., and N.A. de Ridder, 2001, Analysis and Evaluation of Pumping Test Data, ILRI Publication 47, 2nd addition, ISBN 90 70754 207.K-D, 2000. Limitations Work for this project was performed for the YMCA of Seattle (Client), and this memorandum was prepared in accordance with generally accepted professional practices for the nature and conditions of work completed in the same or similar localities, at the time the work was performed. This memorandum does not represent a legal opinion. No other warranty, expressed or implied, is made. All reports prepared by Aspect Consulting for the Client apply only to the services described in the Agreement(s) with the Client. Any use or reuse by any party other than the Client is at the sole risk of that party, and without liability to Aspect Consulting. Aspect Consulting’s original files/reports shall govern in the event of any dispute regarding the content of electronic documents furnished to others. Attachments: Figure 1 – Site Map Figure 2 – Step-Rate Test Hydrograph Figure 3 – Transmissivity Analysis Hydrograph Figure 4 – Long Term Pumping Rates Attachment 1 – Well Log V:\190559 YMCA Mineral Lake\Deliverables\Mineral Lake Pumping Test Methods and Results.docx FIGURES !> N is q u a l ly River A ld er L ake Mineral LakeUV7 UV706 LEWIS COUNT YTHURSTON COUNTY LEWISCOUNTY PIERCECOUNTY 3000'2500'2000'2500'2 0 0 0' 3 000' 2500' 2500' 2000' 1500'2500' 2 0 0 0' 2 5 0 0 '2 0 0 0 '2500' 2000' 1500'2500'2000'2000 ' 1500' 2000' 1500' 3500'2500'3000'3500'3000' 1500' 2000' 2 0 0 0 '2 000'2000'1500' 1500' Well 1 FIGURE NO.1FEB-2021 PROJECT NO.190559 BY:JVH / TDR REVISED BY:- - - Site MapYMCA Mineral LakeMineral Lake, Washingon Basemap Layer Credits || Airbus,USGS,NGA,NASA,CGIAR,NCEAS,NLS,OS,NMA,Geodatastyrelsen,GSA,GSI and the GIS User CommunityCopyright:(c) 2014 Esri2019 Imagery © Pictometry & Lewis County GIS Path: T:\projects_8\YMCA_MineralLake_190559\Delivered\01 Site Map.mxd || Coordinate System: NAD 1983 StatePlane Washington South FIPS 4602 Feet || Date Saved: 2021-02-24 || User: trulien || Print Date: 2021-02-240 3,500 Feet !>Well Parcels Purchased Elbe ! ! ! #! ! ! ! W A S H I N G T O N Bellingham Olympia Port Angeles Seattle Spokane Tacoma Wenatchee YakimaSITELOCATION !( Aspect Consulting 2/23/2021 S:\YMCA of Seattle\Report Drafts\Draft\Figures\YMCA_Hantush-Bierschenk_Solution_DRAFT Figure 2 Step-Rate Test Hydrograph YMCA: Mineral Lake Pumping Test Methods and ResultsYMCA: Mileral Lake, King County, WA 0 5 10 15 20 250 5 10 15 20 25 10 100 1000 Pumping Rate in gpmDepth to Water (ft btoc)Elapsed Time (min) Series1 Drawdown Analysis Flowrate T = 310 ft2/d Aspect Consulting 2/23/2021 S:\YMCA of Seattle\Data\Analyses\PumpingTest032020_repair Figure 3 Transmissivity Analysis Hydrograph YMCA: Mineral Lake Pumping Test Methods and Results YMCA: Mileral Lake, King County, WA Aspect Consulting 2/23/2021 S:\YMCA of Seattle\Report Drafts\Draft\Figures\YMCA_Hantush-Bierschenk_Solution_DRAFT Figure 4 Long Term Pumping Rates YMCA: Mineral Lake Pumping Test Methods and ResultsYMCA: Mileral Lake, King County, WA Attachment 1 Well Log