1. Nitrate Challenges: The Lost Creek Alluvial Fan Laura Alvey Groundwater Remediation Program April 23, 2014

2. Stillwater River Lost Creek

3. Stillwater River Lost Creek

5. Lost Creek Fan Shallow (<150 ft) Potentiometric Surface Map (August 2008)

6. Lost Creek Fan Subsurface: Cobbles and boulders Sand lenses Highly permeable

7. What’s the Problem? MBMG Study

8. What’s the Problem? ?

10. Nitrate Source Identification (Where is it coming from?) Enforcement under MT Water Quality Act: responsibility based on causation Important for fate and transport analysis: – Where did nitrate enter the environment? – Who/what is being affected? – Where is it going? – What can we learn to better manage nitrate in future?

11. Challenge: Many Nitrate Sources

12. Center Pivots Septic Systems

13. Tools for Nitrate Source Identification Stable isotope analysis of NO 3 nitrogen and oxygen Analysis of co-contaminants – Pharmaceuticals, residential wastes (caffeine, artificial sweeteners) – Agricultural chemicals (herbicides, pesticides, other fertilizers) – Metals (boron) – Chloride, other major ions – Bacteria

14. General Findings Nitrate highest in shallow (<150 ft) wells Deeper wells have less nitrate (why?) Stabile nitrate levels between 2002-2011 Isotope results: no clear single source, but suggest fertilizer as a dominant source where nitrate is highest Co-contaminants: nitrate and chlorides trend together, other results inconclusive/mixed

15. Effective Nitrate Management: Permitting programs need to recognize susceptible resources Increased inspections of sensitive sites to ensure compliance

16. Effective Nitrate Management: Permitting programs need to recognize susceptible resources Increased inspections of sensitive sites to ensure compliance

17. Effective Nitrate Management Encourage Best Management Practices Soil moisture sensors Soil testing Crop selection Use of shallow versus deep aquifer

18. Effective Nitrate Management: Property owner education: fertilizers use, well testing, septic upkeep Require engineered septic systems in sensitive areas Require domestic wells completed in deep aquifer Require well completion to minimize cross-contamination

19. Effective Management Baseline monitoring important (MBMG, Ag, USGS) Track impacted groundwater (statewide?)

20. Questions/Comments?