1. Long-Term Nitrate Monitoring in Sensitive Sand and Gravel Aquifers in Minnesota
Jim Stockinger, Erin Eid,
Jennifer Maloney and Mike Trojan
Minnesota Pollution Control Agency
Ground Water Monitoring and Assessment Program

2. Purpose of Presentation
Proposal for Statewide Ambient Monitoring
Midwest GW Conference provides:
Outlet to get information out, build support and gain cooperators
Source of valuable feedback

3. Objectives for a Statewide Ambient Program
Is Minnesota’s Ground Water Getting Better or Worse?
Evaluate the Effectiveness of Ground Water Programs
Impacts from Human Activity

4. STATEWIDE BASELINE ASSESSMENT OF GROUND WATER QUALITY (1992-96)
CHEMICALS/AQUIFERS OF CONCERN
HUMAN EFFECTS (LAND USE STUDIES)
LONG-TERM, TREND MONITORING
EFFECTIVENESS OF BMPS

5. Nitrate-Sensitive What is a Nitrate-Sensitive Aquifer?
An aquifer in which nitrate will not be denitrified.
Based upon the following criteria:
Eh > 250 mV
Dissolved Oxygen > 1 ppm
Iron < 0.7 ppm

6. Location of Nitrate-Sensitive Aquifers
Glacial
Bedrock
Hydrogeology Sensitive
Nitrate Sensitive

7. Why the Sand and Gravel Aquifers?
18% of Wells Sampled from Nitrate-Sensitive, Sand and Gravel Aquifers Exceed the Nitrate Standard of 10ppm
Important Source of Drinking Water
Economically Feasible to Study Them

8. Objectives to Ambient Monitoring of Nitrate
Determine if Nitrate Concentrations are Increasing or Decreasing with Time
Determine if a Correlation Exist Between Land Use and Nitrate Concentrations in Shallow Ground Water
Determine if Contamination of Shallow Ground Water Represents a Drinking Water Risk.

9. Study Design Domestic Wells Network of 100 Domestic Wells
Screened deeper within the aquifer
Represents drinking water supply (receptor)
Network of 100 Domestic Wells
6 land use categories
Irrigated and Non-Irrigated Agriculture, Sewered and Unsewered Residential, Commercial, and Undeveloped

10. Study Design Shallow Monitoring Wells Nested Monitoring Wells
Screened across water table
Represents most recent and vulnerable water
Nested Monitoring Wells
Screened 10 feet below water table
Allows for a profile of the aquifer

11. Monitoring
Wells
Domestic
Well
Infiltration

12. Implementation Selection of Candidate Wells Sampling
Compile list of candidate domestic wells
Obtain permissions for well owners
Sampling
Sample up to 200 domestic wells
Field verify land use

13. Implementation Selecting Monitoring Locations
Uniformed Land Use within a 1/2 Mile
Cooperative Land Owner
Selecting Monitoring Well Locations
Monitoring wells located within a 1/4 mile of the Domestic well

14. Typical Site Layout

15. Sampling Schedule and Parameters
Sample Annually
Between July 1st and August 15
Period of 20 or more years
Field Parameters
Oxidation-reduction potential
Dissolved oxygen
Reduced iron and manganese
Laboratory Analysis
Nitrate, Chloride, TOC

16. Focus Areas Watershed Level Address local land use issues
Area actively implementing BMPs
Surface water component can be added

17. Local Land Use Issues Septic systems Manure storage Irrigated agriculture Row crop agriculture Land application of manure Conversion of CRP land Residential fertilizers

18. WATERSHED LEVEL Residential development along rivers
Row crop agriculture
Currently not threatened
Primarily bedrock aquifers
Irrigated agriculture; residential
development

19. Focus Areas Areas of On-going Studies
Incorporate existing monitoring wells
Existing data

20. Manure management studies
Land use studies
Septic system studies
Manure management studies
Geochemical studies
Agricultural BMPs
ON-GOING STUDIES

21. Additional Benefits of Study
Compilation of Existing Ground Water Data Bases
GIS Coverages
Land use, land use changes, geologic and hydrogeologic

22. Resources GWMAP Can Provide Resources Needed Analytical Dollars
Data Analysis / Reporting
Resources Needed
Assistance with locating study sites
Dollars for installing monitoring wells
Assistance with sampling

23. Time Frame Domestic Well Network Monitoring Well Network
1 month to identify candidate wells
2 months to obtain permissions and sample
Monitoring Well Network
Several years to install entire network
Install 15 to 20 well nest per year