To better understand ground water, it’s important to visualize the rock layers, most of which serve as drinking water aquifers, which exist under Dodge County, moving from deepest to shallowest. Source: Minnesota DNR

Let’s cut through the rock layers and expose them from a side view.

EllingtonConcordMilton WEST EAST SOIL, SAND & GRAVEL GALENA LIMESTONE DECORAH SHALE ST. PETER SANDSTONE PRAIRIE DU CHIEN DOLOMITE/SANDSTONE Miles Generalized Geographic Formations Underlying Ellington, Concord and Milton Townships Subsurface Geologic Cross-Section Elevation Above Sea Level (ft) In general, the thicker soils in the western portion of the county provide more protection from surface contaminants reaching the rock layers. Source: Dodge County Environmental Atlas

Generalized Geographic Formations Underlying Ellington, Concord and Milton Townships Subsurface Geologic Cross-Section SOIL, SAND & GRAVEL GALENA LIMESTONE DECORAH SHALE ST. PETER SANDSTONE PRAIRIE DU CHIEN DOLOMITE/SANDSTONE Miles Elevation Above Sea Level (ft) MiltonConcordEllington WESTEAST ~60% of all wells ~15% of all wells ~ 10% of all wells Shallow Well, < 50 Ft. to Bedrock Deep river valleys in the eastern portion of the county can erode the protective shale layer, exposing the layers below to contamination. Source: Dodge County Environmental Atlas

ClaremontWasiojaMantorville EAST SOIL, SAND & GRAVEL GALENA LIMESTONE DECORAH SHALE ST. PETER SANDSTONE PRAIRIE DU CHIEN DOLOMITE/SANDSTONE Miles Subsurface Geologic Cross-Section Generalized Geographic Formations Underlying Claremont, Wasioja, and Mantorville Townships WEST Elevation Above Sea Level (ft) Source: Dodge County Environmental Atlas

GALENA LIMESTONE DECORAH SHALE ST. PETER SANDSTONE PDC SOIL, SAND & GRAVEL Subsurface Geologic Cross-Section Elevation Above Sea Level (ft) Generalized Geographic Formations Underlying Ripley, Ashland, and Canisteo Townships WEST RipleyAshlandCanisteo EAST Source: Dodge County Environmental Atlas

GALENA LIMESTONE DECORAH SHALE ST. PETER SANDSTONE PDC Elevation Above Sea Level (ft) WEST WestfieldHayfieldVernon EAST CEDAR VALLEY-MAQUOKETA LIMESTONE SOIL, SAND & GRAVEL Generalized Geographic Formations Underlying Westfield, Hayfield, and Vernon Townships Subsurface Geologic Cross-Section Miles Source: Dodge County Environmental Atlas

MN Dept. of Health Drinking Water Standard – 10mg/L Levels Beyond 10 mg/L Cause Health Risks to Infants and Expectant Mothers Source: Minnesota Dept. of Health; Dodge County Environmental Services

Presence of Coliform Bacteria in Well Water Indicates Surface Contaminants and Disease-Causing Organisms May be Present. E. Coli is a More Serious Disease-Causing Type of Coliform Bacteria. Source: Minnesota Dept. of Health; Dodge County Environmental Services

High nitrate wells occur most frequently in the Highly Sensitive Groundwater Area, where depth-to-bedrock is less than 50 ft, or where underground sand lenses exist. Source: Minnesota DNR; Dodge County Environmental Services

AQUIFER - NITRATE SUMMARY FOR WELLS TESTED NITRATE LEVEL AQUIFER0-1 mg/l1-10 mg/l10+ mg/l GALENA LIMESTONE 75 %17 %8 % ST. PETER 89 %11 %0 % PRAIRIE du CHIEN JORDAN 100 %0 % Nitrate levels > 1 mg/l in the St. Peter Sandstone are a reason for concern. Source: Dodge County Environmental Services

Areas of Dodge County where the St. Peter Sandstone is shallow and vulnerable to surface contamination. Source: Minnesota DNR

Comparative Surface Water Nitrogen Load by Subwatershed Source: MPCA – Draft Zumbro Watershed WRAPS Document 2015

Source: MPCA - Nitrogen in Minnesota Surface Waters June 2013

Statewide Nitrogen Sources to Land Source: MPCA - Nitrogen in Minnesota Surface Waters June 2013

MN Nutrient Reduction Strategy Source: MPCA – Minnesota Nutrient Reduction Strategy December 2014

Phophorous & Nitrogen Goals for the Mississippi Basin

Reducing Nitrogen Losses Source: MPCA – Minnesota Nutrient Reduction Strategy December Fertilizer and Tillage Practices 2 Drainage Practices 3 Cover Crop Practices

Dodge County Volunteer Nitrate Monitoring Network A grant-funded network operating across SE MN since Approximately 100 private well owners participate in Dodge County, sampling their wells every 6 months. The Dodge County network is sub-divided into one baseline, and three targeted, groups. The targeted groups are: 1)Wells monitoring areas near known high-nitrate wells. 2) Wells monitoring areas near existing sinkholes. 3) Wells monitoring the region along the Decorah Edge. Nitrate-Related Ground Water Projects:

Source: Dodge County Environmental Services

Dodge County Volunteer Nitrate Monitoring Network Results Nitrate Level (mg/l) MN Dept. of Health Drinking Water Limit = 10 mg/l 0 – 1 mg/l is considered back- ground level The recent upward trend in nitrate level may be due, in part, to recent near-drought conditions, which tend to concentrate nitrate in the drinking water aquifers. Source: Dodge County Environmental Services

Nitrate-Related Surface Water Programs & Projects: BeforeAfter Dodge County 50-Foot Stream Buffer Program Buffers provide a deterrent to the movement of soil and nutrients into the stream.

Date Nitrate Level (mg/l) Field tile drainage is diverted through the woodchips, where a high percentage of nitrate is removed. Source: Dodge County Environmental Services

Using Saturated Buffers for Nitrate Removal Field tile water runs through a perforated tile parallel to the buffered ditch or stream, allowing limited drainage through the buffer, which reduces nitrate levels. Source: Dodge County Environmental Services

Dodge County Saturated Buffer MN-4: 2014 Results Nitrate Levels (mg/L) Source: Dodge County Environmental Services

Edge-of-Field Monitoring Stations Water samples are gathered and analyzed, providing accurate information to producers on nutrients that leave their fields during snow-melt and runoff events. Discovery Farms SiteMN Dept. of Ag. Grant Site Source: Dodge County Environmental Services

Source: MPCA – Swimmable, Fishable, Fixable? April 2015 Most Recent Pollution Results for Minnesota Waters

Source: MPCA – Swimmable, Fishable, Fixable? April 2015 Most Recent Pollution Results for Minnesota Waters

Source: MPCA – Swimmable, Fishable, Fixable? April 2015 Most Recent Pollution Results for Minnesota Waters