Moses Lake Total Maximum Daily Load Groundwater Study
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Moses Lake Total Maximum Daily Load Groundwater Study February 2003 Publication No. 03-03-005 printed on recycled paper Publication Information This report is available on the Department of Ecology home page on the World Wide Web at http://www.ecy.wa.gov/biblio/0303005.html For a printed copy of this report, contact the Department of Ecology Publications Distributions Office and ask for Publication Number 03-03-005. Address: PO Box 47600, Olympia WA 98504-7600 E-mail: [email protected] Phone: (360) 407-7472 Author: Charles Pitz, Hydrogeologist Washington State Department of Ecology Address: PO Box 47600, Olympia WA 98504-7600 E-mail: [email protected] Phone: (360) 407-6775 This report was prepared by a licensed hydrogeologist. A signed and stamped copy of the report is available upon request. Any use of product or firm names in this publication is for descriptive purposes only and does not imply endorsement by the author or the Department of Ecology. The Department of Ecology is an equal-opportunity agency and does not discriminate on the basis of race, creed, color, disability, age, religion, national origin, sex, marital status, disabled veteran’s status, Vietnam-era veteran’s status, or sexual orientation. If you have special accommodation needs or require this document in alternative format, please contact Joan LeTourneau at 360-407-6764 (voice) or 711 or 1-800-833-6388 (TTY) Moses Lake Total Maximum Daily Load Groundwater Study by Charles F. Pitz, L.G., L.HG. Environmental Assessment Program Olympia, Washington 98504-7710 February 2003 Waterbody Number: WA-41-9250 Publication No. 03-03-005 printed on recycled paper This page is purposely blank for duplex printing Table of Contents Page List of Figures and Tables................................................................................................... ii Abstract.............................................................................................................................. iii Acknowledgements............................................................................................................ iv Executive Summary.............................................................................................................v Introduction..........................................................................................................................1 Study Purpose and Goals ...............................................................................................1 Physical Setting....................................................................................................................5 Study Area Description..................................................................................................5 Study Area Geology and Hydrogeology........................................................................6 Background Information....................................................................................................17 Phosphorus Fate and Transport Controls in Groundwater...........................................17 Natural Condition of Phosphorus in Area Groundwater..............................................18 Potential Anthropogenic Sources of Nutrients in Area Groundwater .........................20 Historic Estimates of Groundwater Loading to Moses Lake.......................................25 Methods..............................................................................................................................27 Monitoring Network ....................................................................................................27 Sampling and Analysis Procedures..............................................................................29 Quality Assurance........................................................................................................33 Results................................................................................................................................37 Hydraulic Gradient.......................................................................................................37 Groundwater Quality Results.......................................................................................37 Discussion..........................................................................................................................53 Hydraulic Conditions...................................................................................................53 Groundwater Quality Conditions.................................................................................53 Conclusions........................................................................................................................63 Recommendations..............................................................................................................65 References..........................................................................................................................67 Appendices A. Rocky Ford Springs Source Evaluation B. Sampling Procedures C. Field Water Quality Data D. Project Quality Assurance E. Piezometer Head and Gradient Data F. Estimates of Groundwater Loading of Phosphorus to Moses Lake Page i List of Figures and Tables Page Figures Figure 1. Location Map – Moses Lake, Washington..........................................................3 Figure 2. Study Area Map...................................................................................................7 Figure 3. Generalized Land Use Map .................................................................................9 Figure 4. Surficial Geology Map ......................................................................................10 Figure 5. General Stratigraphy and Conceptual Cross-Section Model of Groundwater Flow ............................................................................................11 Figure 6. Potential Point Sources of Phosphorus to Groundwater ...................................22 Figure 7. Sampling Station Location Map........................................................................28 Figure 8. Schematic of Measurement Method to Estimate Vertical Hydraulic Gradient at Study Piezometers ..........................................................................31 Figure 9. Estimated Vertical Hydraulic Gradient at Study Piezometers ..........................38 Figure 10. Nitrate-N Concentration – May, July, October 2001 ......................................43 Figure 11. Nitrogen Concentrations – May, July, October 2001......................................45 Figure 12. Orthophosphate Concentration – May, July, Oct. 2001 ..................................47 Figure 13. Orthophosphate Concentration in Groundwater..............................................49 Figure 14. TDS, Chloride, and Orthophosphate Concentration – May 2001 ...................50 Figure 15. TDS, Chloride, Iron, Manganese, Dissolved Oxygen, and Orthophosphate Concentration – July 2001 ....................................................51 Figure 16. TDS, Chloride, Iron, Manganese, Dissolved Oxygen, and Orthophosphate Concentration – October 2001 ..............................................52 Figure 17. Comparison of Vicinity Land Use to Orthophosphate Concentration ............61 Tables Table 1. Groundwater Quality Results..............................................................................39 Page ii Abstract Moses Lake has historically exhibited eutrophic or hypereutrophic conditions, and is on the 1996 federal Clean Water Act 303(d) list as an impaired waterbody. Phosphorus has been identified as the limiting nutrient for the lake. Based on characteristic uses of the lake, an in-lake total phosphorus concentration target of 0.050 mg/L has been proposed to manage water quality concerns. In order to develop an allocation strategy for phosphorus loading to the lake, a Total Maximum Daily Load (TMDL) study was conducted by the Washington State Department of Ecology (Ecology) Environmental Assessment Program, at the request of Ecology’s Eastern Regional Office. To better characterize the concentration and potential source of nutrients in groundwater directly discharging to the lake, 12 lake-bed piezometers were installed in the littoral zone of the lake along portions of the shoreline judged from regional data to be receiving groundwater discharge. Water quality samples were collected from the piezometers, as well as from one near-shore domestic well and two surface springs, during May, July, and October of 2001. Samples were analyzed for orthophosphate as P (OP), total dissolved phosphorus, nitrate+nitrite-N, ammonia- N, total persulfate nitrogen, chloride, total dissolved solids, and dissolved iron and manganese. The majority of stations (75%) exhibited groundwater OP concentrations above the 0.050 mg/L surface water target criteria. Concentrations of OP in groundwater generally increased from north to south, paralleling increases in concentrations of parameters that indicate anthropogenic (human-caused) impact to water quality. A statistically significant relationship was established between OP concentration and the relative percentage of urban development upgradient of each station. These findings suggest that urban releases of wastewater to the aquifer are the primary source of phosphorus entering the lake via groundwater discharge. Loading calculations predict an annual OP mass flux to the lake from approximately 400 to 40,000 kgop per year via groundwater discharge, with