Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW...
Transcript of Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW...
![Page 1: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/1.jpg)
Christine Miller, Tammy Swinney, Erinn Zindt, Torie Haraldson
MT Section AWRA Conference, October 10th, 2014
Gallatin Groundwater Project: Assessing Cumulative
Impacts to Groundwater in High Density
Septic System Areas
![Page 2: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/2.jpg)
Background
• Between 1990 and 2009, the population of Gallatin County, Montana increased by approximately 79% (U.S. Census Bureau, 2007)
• Some subdivision areas have been developed with individual septic systems for each home
• Wastewater effluent from areas of high septic system density can negatively impact groundwater and surface water quality
Photos: A. English
![Page 3: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/3.jpg)
Background • ~13,350 active septic systems discharging about 4 million gallons per day
of effluent into groundwater in Gallatin County (English, Assessment of Current
Wastewater Treatment and Disposal in Gallatin County, 2010)
• All treated wastewater from these septic systems as well as from municipal and public systems in Gallatin County is discharged to either groundwater, surface water, or applied to the land surface
• Many residents in the Gallatin Valley rely on groundwater as their drinking water source
![Page 4: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/4.jpg)
Project Goal
• In the Gallatin Local Water Quality District, assess whether individual septic systems and public sewage systems in high density development areas are negatively impacting water quality.
![Page 5: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/5.jpg)
1) Are areas of high density septic systems and public sewage systems measurably and negatively impacting groundwater quality?
2) Have historical nitrate levels increased down-gradient of subdivisions characterized by high density septic systems and public sewage systems?
3) Are nitrate levels trending upward for public water supplies down-gradient of developed areas?
Project Questions
![Page 6: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/6.jpg)
![Page 7: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/7.jpg)
Groundwater flow is generally to the northwest in the Gallatin Valley
Wells sampled in subdivision focus
areas are generally shallow (<100’) and in alluvial aquifers
![Page 8: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/8.jpg)
Methods
- Groundwater sampling of eight subdivision areas for various analytes
- Nutrients (nitrate, orthophosphate)
- Wastewater tracers (boron, chloride, specific conductivity)
- Nitrate isotopes – can help identify source
- Gathered historical nitrate data
- Gathered data from nitrate sensitivity analyses from non-degradation reports
- Gathered Public Water Supply nitrate data
![Page 9: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/9.jpg)
Results – Nitrate-N in 2013 Samples
< 2 mg/L 47.8%
2-4.99 mg/L 32.8%
5-10 mg/L 15.9%
>10 mg/L 3.5%
Elevated nitrate is not a widespread problem in the wells sampled
![Page 10: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/10.jpg)
0
5
10
15
20
25
30
(mg
/L)
Mean Nitrate-N
Mean Chloride
Results - Mean Nitrate-N and Chloride for Subdivision Focus Areas
![Page 11: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/11.jpg)
Results - Mean Orthophosphate-P and Boron for Subdivision Focus Areas
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
(mg
/L)
Mean Orthophosphate
Mean Boron
![Page 12: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/12.jpg)
Results – Nitrate Isotopes
-20
-15
-10
-5
0
-5 5 15 25
δ1
8O
-NO
3-
δ15N-NO3-
High K, River Rock
Hyalite Heights/Lazy TH
Western Drive
Mountain View
Middle Creek
Jackrabbit
Baxter/Wylie
Wheatland Hills Manure and Septic Waste
Fertilizer and Precipitation NH4
+
Soil NH4
+
![Page 13: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/13.jpg)
One subdivision area with elevated nitrate is located in an area of higher
soil organic matter
![Page 14: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/14.jpg)
Results – Historical vs. 2013 Nitrate
1.60 2.58
9.37
5.88 5.30 3.20
41.00
4.97
2.11 2.90
17.40
7.27
12.80
6.16
10.10
6.40
0
5
10
15
20
25
30
35
40
45
Max
Nit
rate
-N (
mg
/L)
Max Historical Nitrate-N
Max 2013 Nitrate-N
![Page 15: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/15.jpg)
Non-Degradation and Nitrate
1.08 1.12
1.97
1.41 1.29
1.87
3.10
2.65
3.28
2.61
3.35
5.20
1.41 1.70
3.48
2.07
2.84
4.93
0
1
2
3
4
5
6
Nit
rate
-N (
mg
/L)
Mean Background Non-Degradation Nitrate
Mean Non-Degradation Expected Nitrate
Mean 2013 Nitrate
![Page 16: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/16.jpg)
Results – Nitrate Trends in Public Water Supplies near Subdivision Focus Areas
Example:
Slope of linear trend lines compared (increasing or decreasing )
0
2
4
May-70 Nov-75 Apr-81 Oct-86 Apr-92 Sep-97 Mar-03 Sep-08 Mar-14
Nit
rate
-N (
mg
/L)
Nitrate Trends in PWS Near Middle Creek Focus Area Four Corners Baptist Church
Garden Center Subdivision + -
![Page 17: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/17.jpg)
Conclusions
• Widespread cumulative effects from septic systems on groundwater currently not observed
• Localized areas of concern
• Nitrate source: septic/animal waste and/or soils, fertilizer in some areas
• Increasing nitrate levels in groundwater, expected to continue
• Some public water supplies show an increase in nitrate
![Page 18: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/18.jpg)
Recommendations
• Educational Efforts
• Maintain septic systems (pumping, inspections)
• Appropriately fertilize lawns and gardens – (Minimize additional nutrient additions to groundwater)
• Avoid excessive watering (reduce nitrate leaching)
• Continue to encourage community water and wastewater systems
• Especially in Source Water Protection (SWP) areas
• Regular monitoring required
• Problems pinpointed and more easily remedied compared to diffuse contamination from array of septics
![Page 19: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/19.jpg)
Recommendations Cont’d
• Encourage installation and sampling of down-gradient monitoring wells for new developments • Early identification of water quality problems or wastewater
treatment system problems
• Long term water quality data sets created
• Annual testing of domestic drinking water • Protect health of Gallatin Valley residents consuming water from
private domestic wells
• Long term water quality data sets created
![Page 20: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/20.jpg)
Thank you to: – Montana DEQ 319 Grant Funding
– Gallatin County Planning Department
– Gallatin City-County Environmental Health Services (EHS)
– Gallatin County GIS Department
– Homeowners and residents who allowed GLWQD staff to
sample their domestic wells – Gallatin County/MSU Extension
![Page 21: Gallatin Groundwater Project: Assessing Cumulative Impacts ...accpg.org/docs/Undated/Gallatin GW Project... · Hyalite Heights/Lazy TH Western Drive Mountain View Middle Creek Jackrabbit](https://reader034.fdocuments.net/reader034/viewer/2022051808/600bf57e44fc000b0f78a66b/html5/thumbnails/21.jpg)
Thank you!
Questions?