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Nitrate Challenges: The Lost Creek Alluvial Fan
Laura AlveyGroundwater Remediation Program
April 23, 2014
Stillwater River
Lost Creek
Stillwater River
Lost Creek
Lost Creek Fan Shallow (<150 ft) Potentiometric Surface Map (August 2008)
Lost Creek Fan Subsurface:• Cobbles and boulders• Sand lenses• Highly permeable
What’s the Problem?
Jun-94 Oct-95 Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04 May-05 Oct-06 Feb-080
10
20
30
40
50
60
Nitrate Trends in Selected Wells
84527
137876
84486
84528
LaChapSh
Time
Nit
rate
(m
g/L
-N) Homeowner sample
DEQ InvestigationMBMG Study
What’s the Problem?
Jun-94 Oct-95 Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04 May-05 Oct-06 Feb-080
10
20
30
40
50
60
Nitrate Trends in Selected Wells
84527
137876
84486
84528
LaChapSh
Time
Nit
rate
(m
g/L
-N) ?
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?
Challenge: Many Nitrate Sources
Center Pivots
Septic Systems
Tools for Nitrate Source Identification
• Stable isotope analysis of NO3 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
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
Effective Nitrate Management: • Permitting programs need to recognize susceptible resources• Increased inspections of sensitive sites to ensure compliance
Effective Nitrate Management: • Permitting programs need to recognize susceptible resources• Increased inspections of sensitive sites to ensure compliance
Effective Nitrate Management Encourage Best Management Practices • Soil moisture sensors• Soil testing• Crop selection
• Use of shallow versus deep aquifer
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
Effective Management
• Baseline monitoring important (MBMG, Ag, USGS)
• Track impacted groundwater (statewide?)
Questions/Comments?