The Iowa Community Private Well Study: Random Sampling

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The Iowa Community Private Well Study Random
Sampling

• Peter Weyer
• Center for Health Effects of Environmental
  Contamination
• The University of Iowa

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Private Well Water Quality

• No regulatory mechanism for sampling
• Safe Drinking Water Act applies only to public
  water systems
• Population at risk ?
• generally shallow alluvial wells vulnerable to
  proximate point / nonpoint contaminant sources
• Iowa population using groundwater as drinking
  source
• 1.5 M served by community water supplies
• 240,000 use private wells

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Statewide Rural Well Water Survey (SWRL)

• 1988-89 sampling of 856 private rural wells
• nitrate, bacteria, pesticides
• Nitrate (NO3-N)
• 18.3 of rural private wells statewide 10mg/L
• 35 of wells 10 mg/L
• 130,000 rural Iowa residents use well water
  with high nitrate
• Atrazine
• 8 of wells statewide had atrazine detection
• mean 1.14 ppb max 7.71 ppb
• varied by region and well depth

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Iowa Community Private Well StudyRandom Sampling

• One time sampling of 103 randomly selected
  private wells in 50 Iowa communities without
  public water systems
• Conducted from June 2002 - January 2003
• Funded by Iowa Department of Natural Resources,
  U.S. Geological Survey, UI Hygienic Laboratory,
  CHEEC
• Conducted by CHEEC, UHL, USGS, UI Environmental
  Health Sciences Research Center

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Well Sampling Design

• Incorporated communities without public water
  systems
• initially 124 communities eligible
• Weighted by number of households within a
  community
• assumption each household has private well
• Random number generation selected 120 wells
• 57 communities total rural water in 7
  communities

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Well Sampling Locations
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Well Sampling Design

• Orthophoto maps used to identify community
  boundaries
• polygon drawn around boundary
• ARCView GIS randomly selected points within
  polygon based on number of samples to be taken

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Community Contact and Risk Communication

• Communities notified by letters and press
  releases sent to local newspapers
• County sanitarians visit study communities
• identify sampling locations
• collect water samples
• administer well construction / contaminant site
  survey
• Follow-up letters to well owners
• detections, health effects information
• Regional meetings to discuss results

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Water Sample Analyses

• Water samples analyzed at UHL
• total and fecal coliform bacteria
• nitrate nitrite as NO3 ammonia nitrogen as N
• nitrogen-containing herbicides and
  organophosphate/carbamate insecticides
• regulated, unregulated discretionary VOCs
• arsenic
• 10 duplicate sample and analysis by USGS

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Herbicide Detections Random Sampling

Min level Max level MCL
Detects Detects (ppm) (ppm)
(ppm)   Acetochlor 1 1.0
0.00081 0.00081 - Alachlor
1 1.0 0.00051 0.00051
0.002 Atrazine 20 19.4
0.00043 0.00005 0.003 Cyanazine 1
1.0 0.000057 0.000057
- Desethylatrazine 29 28.2
0.000058 0.00068 - Desisoproylatrazine
4 3.9 0.000092 0.00026
- Metolachlor 4 3.9
0.00017 0.0009 - Prometon 3
2.9 0.000093 0.00024 -
103 wells
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Inorganics and Bacteria Detections Random
Sampling

Min level
Max level Detects Detects
(ppm) (ppm) Inorganics Nitrate
nitrite as N 59 57.3 0.5
27.3 Total arsenic 27 26.2
0.001 0.061
 
Bacteria E. coli 4 3.9
Enterococci 9 8.7
Fecal coliform 4 3.9
Total coliform 31 30.1   (
103 wells) Presence of organisms

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Disinfection By-products / VOC Detections Random
Sampling

Min level Max
level Detects Detects (ppm)
(ppm) Chloroform 3
2.9 0.0007 0.0033 Bromodichloromethane
1 1.0 0.0022 0.0022 Dibromochlorometh
ane 2 1.9 0.0005 0.0016
 
Carbon tetrachloride 1 1.0
0.0006 0.0006 Dichlorofluoromethane
1 1.0 0.0005
0.0005 Tetrachloroethene 1 1.0
0.0005 0.0005 (103 wells)
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Contaminant Detections and Well
CharacteristicsRandom Sampling
Desethyl- Well depth Atrazine
atrazine Nitrate Ammonia
Arsenic   ? 50 feet (32) 28
47 94 16
16 ?50 feet (44) 13 14 30
59 32 Unknown (27) 18
30 59 41 30      
Cased Well Yes (58) No (21) No
info (24) Nitrate 10 ppm 10 43
37   Sand point well Yes (38) No
(42) No info (23)  Nitrate 10 ppm 34
17 22
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SWRL and ICPWS Random SamplingStatewide
Comparison
 
ICPWS SWRL Contaminant
(n103) (n686) Atrazine
2.9 4.4 Desethylatrazine
18.4 3.5 Desisopropylatrazine 2.9
3.4 Total atrazine 19.4
8.0   Nitrate 10ppm 23.3
18.3   Detection limits atrazine 0.00013 ppm
desethylatrazine and desisopropylatrazine
0.0001 ppm
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SWRL and ICPWS Random SamplingRegional
Comparison
 
ICPWS SWRL
N. East E. Central N. East
E. Central Contaminant
(n24) (n60) (n88)
(n219) Atrazine 0
5.0 3.4 4.1
Desethylatrazine 16.7 25.0
2.3
3.7 Desisopropylatrazine 0
5.0 1.1 2.7 Total atrazine
16.7 26.7 4.2
7.7   Nitrate 10ppm 25.0
23.3 9.2 11.6   Detection limits
atrazine 0.00013 ppm DEA and DIA 0.0001 ppm

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Conclusions

• Nitrate continues to be a problem
• 23 of wells 10 ppm
• Atrazine/metabolite detections have increased
• 19 atrazine, 28 DEA
• Arsenic prevalent
• 26 detections
• Well depth / construction important factors

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Recommendations / Future Research

• Recommendations
• team approach sanitarians, geologists,
  epidemiologists
• model for prospective studies
• Future research
• sampling wells in unincorporated areas
• SWRL sampling frame 20 annually

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Research Collaborators

• Fall Plowing by Grant Wood
• Courtesy of the Deere Art Collection, Moline,
  Illinois
• Iowa County Environmental Health Specialists
• Jessica Ferrie UI Dept of Occupational
  Environmental Health
• Michael Wichman, Lorelei Kurimski , Terry Cain
  UI Hygienic Laboratory
• Brent Parker, Mary Skopec, Robert Libra Iowa
  Dept. Natural Resources
• David Osterberg UI Environmental Health Sciences
  Research Center
• Douglas Schnoebelen, Robert Buchmiller U.S.
  Geological Survey
• David Riley, Jiji Kantamneni, Zheng Fang Feng
  CHEEC