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Hydrogeology and Groundwater Quality of the UW-Platteville Pioneer Farm and Vicinity Jacob A. Macholl George J. Kraft July 2010.

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Presentation on theme: "Hydrogeology and Groundwater Quality of the UW-Platteville Pioneer Farm and Vicinity Jacob A. Macholl George J. Kraft July 2010."— Presentation transcript:

1 Hydrogeology and Groundwater Quality of the UW-Platteville Pioneer Farm and Vicinity Jacob A. Macholl George J. Kraft July 2010

2 Objectives Process geologic data borehole geophysical data Evaluate spatial and temporal trends in: Hydrogeology water-table configuration hydraulic gradients Groundwater quality nitrate, chloride, pesticide residues

3 Study Area NMVLH (MLRA 105) 22,209 mi² - 1/5 th of WI Unglaciated Well drained loess soils Predominantly agricultural Upper Fever River Watershed 3,357 ac. Representative of NMVLH Location of UWP Pioneer Farm

4 Instrumentation 12 boreholes at the Pioneer Farm Range from 42 to 254 ft below land surface

5 Instrumentation Nested piezometers (monitoring wells) Sample discrete interval - 5 to 10 ft Quality Hydraulic head 2 to 4 per borehole 37 total (2 usually dry) FLUTe Borehole LF port device 2 to 5 ft sample interval ~180 ft west of LF-465 LF-472 LF-465LF-466

6 Geology Geophysical logs Wisconsin Geological and Natural History Survey Interpret subsurface geology, structure Completed prior to piezometer installation Assisted placement Borehole LF-465 Deep well

7 ~300 ft of Ordovician dolomites and limestones - Sinnipee Group Overlies ft of older sandstones and carbonates Separated by Glenwood shale aquitard Geology

8 Fence Diagram – Transect Locations A A B C B C Pioneer Farm

9 A A B C B C Geology Fence Diagram Osp Ogs Op Ods Ogl Ogu

10 Geology Cross-section B-B Dissolution zone approximated from caliper, flow and optical logs

11 Hydrogeology Water-table Measured piezometer hydraulic head during sample collection Head varies: seasonally, annually with location Solid symbols: uplands Hollow symbols: lowlands and intermediate areas

12 Hydrogeology Water-table: Average Configuration Heads from June 2009

13 Hydrogeology Vertical Gradients Indicate direction of groundwater flow (up, down, horizontal) In the Sinnipee aquifer, gradients were: downward beneath uplands, upward near the Fever River, generally horizontal in-between Largest was 1.4 downward – across Glenwood shale Spechts Ferry shale and(or) Platteville Fm may play a role Groundwater flow is described with equipotential lines

14 Hydrogeology Equipotential Lines Groundwater flowpath

15 Groundwater Quality Groundwater Samples 733 samples from October 2006 to January 2010 Primary constituents Nitrate-N Chloride Conductivity pH Some samples of Pesticide residues, D.O., Metals, TKN, etc. Major agricultural pollutants

16 Groundwater Quality Average = 10.9 mg/L range <0.1 to 76.3 mg/L MCL = 10 mg/L 20 of 35 piezometers (57%) had median exceeding MCL 26 (74%) had at least one above MCL Few significant temporal trends (year or season) more data required to conclude if specific trends exist Spatial distribution remained relatively constant Nitrate-N

17 Groundwater Quality Nitrate-N: Map view

18 Groundwater Quality Nitrate-N: Cross-section Dissolution Zone

19 Groundwater Quality Chloride Average = 19.4 mg/L range <0.1 to 84 mg/L Significantly correlated to Nitrate-N Spatial distribution similar to Nitrate-N

20 Groundwater Quality Chloride: Map view

21 Groundwater Quality Chloride: Cross-section

22 Groundwater Quality Pesticide Residues Detected residues: Alachlor ESA Metolachlor ESA Acetochlor OA Metolachlor OA Atrazine and its degradate deethyl-atrazine ESA degradates account for 90% of cumulative concentration Metolachlor ESA: up to 10.5 µg/L Alachlor ESA: up to 4.7 µg/L Spatial distribution similar to other pollutants Most frequently detected

23 Groundwater Quality Pesticide Residues: Cross-section

24 Conclusions Dissolution zone is likely the major conduit for transport of groundwater and pollutants Degree of bedrock weathering important Borings show Sinnipee grades from: soil weathered bedrock dissolution zone (near water-table) competent bedrock Groundwater flows primarily from topographic highs down- gradient to Fever River. Groundwater basin similar to surface watershed BUT varies with changes in water-table elevation Hydrogeology Permeability decreases with depth

25 Conclusions High Nitrate-N common in groundwater Majority of piezometers (74%) contain nitrate-N above 10 mg/L MCL Chloride also elevated, up to 84 mg/L Pesticide residues detected during winter and summer Primarily ESA degradates of Alachlor and Metolachlor Higher concentrations detected in summer Pollutants greater in upgradient part of farm and in shallower part of aquifer Pollutants have not fully penetrated aquifer Yearly and seasonal trends not evident in groundwater Nitrate-N and Cl Suggests near steady state conditions during the study period Groundwater Quality

26 What Next? Continue groundwater quality sampling To identify trends Nitrate-N, Cl, pH, Conductivity: monthly Other constituents: at least annually Collect additional samples from deeper FLUTe ports LF-472-6, -7, and -8 Galena Decorah Platteville St. Peter Fill this gap

27 What Next? Continue groundwater quality sampling To identify trends Collect additional samples from deeper FLUTe ports LF-472-6, -7, and -8 Construct groundwater flow model Gain more insight into groundwater flow system Characterize hydraulic conductivity, important model parameter Slug tests Process new water level, temperature, conductivity data Groundwater response to events

28 Acknowledgments WGNHS Ken Bradbury Dave Hart Roger Peters Dan Hallau UWP Pioneer Farm Staff

29 Generalized Stratigraphy Study Zone

30 Aquitard Geology Detailed Stratigraphy and Hydrostratigraphy Unsaturated in UFRW


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