Impacts Demo 1: Private Well PFAS by County
Demo Question: How does private well PFAS testing vary by county in Maine, and what percentage of tested wells have results over 20 ppt?
Use Case Area: Assess and Map Potential Impacts
This demo combines private water supply testing data with well and county information to compare PFAS testing across Maine counties. It shows the extent of testing represented in the available data, summarizes measured concentrations, and compares the proportion of tested wells with results above 20 ppt.
What This Demo Connects
Private Water Supply Testing
PFAS observations and results from private water supply well sample points.
Wells
Located wells represented in SAWGraph and used to provide county-level context for the testing results.
Counties
Maine counties used to aggregate, compare, and map well and PFAS testing data.
Demo Results
One way to assess potential impacts is to aggregate sampling data by administrative regions such as counties or county subdivisions. Regional aggregation also makes it possible to compare represented features, such as wells, with sampled features even when records from different source datasets do not use matching identifiers.
This demonstration uses county aggregation to summarize three measures from the data returned by the SAWGraph queries: the percentage of represented wells associated with private water supply testing, the maximum measured PFAS concentration returned for private water supply samples, and the percentage of tested wells with results above the 20 ppt threshold used in this demonstration.
The table and maps show county-level results based on the datasets currently represented in the graph. Results therefore reflect the scope and version of those datasets, as well as the conditions of the queries.
The well totals used in this demonstration currently reflect wells that can be spatially located from the available data. The resulting percentages therefore summarize the data represented in the demonstration rather than all private wells in each county.
County Summary
The table provides the county-level results used in the analysis, including total represented wells, tested wells, maximum measured concentration, wells and samples with results above 20 ppt, percent tested, and percent of tested wells above 20 ppt.
| County | Total Wells | Tested Wells | Max Concentration | Wells Over 20 ppt | Samples Over 20 ppt | Percent Tested | Percent Over 20 ppt | |
|---|---|---|---|---|---|---|---|---|
| 0 | Sagadahoc County, Maine | 3425 | 53 | 218.310 | 7 | 25 | 1.55 | 13.21 |
| 1 | Aroostook County, Maine | 3231 | 87 | 2290.000 | 17 | 39 | 2.69 | 19.54 |
| 2 | Cumberland County, Maine | 11779 | 146 | 285.000 | 22 | 34 | 1.24 | 15.07 |
| 3 | York County, Maine | 10917 | 172 | 644.000 | 26 | 48 | 1.58 | 15.12 |
| 4 | Hancock County, Maine | 7295 | 49 | 106.000 | 13 | 19 | 0.67 | 26.53 |
| 5 | Knox County, Maine | 3312 | 15 | 265.000 | 5 | 7 | 0.45 | 33.33 |
| 6 | Androscoggin County, Maine | 5952 | 99 | 382.000 | 7 | 29 | 1.66 | 7.07 |
| 7 | Penobscot County, Maine | 6005 | 130 | 3650.000 | 55 | 254 | 2.16 | 42.31 |
| 8 | Kennebec County, Maine | 5880 | 296 | 36000.000 | 106 | 720 | 5.03 | 35.81 |
| 9 | Washington County, Maine | 4577 | 43 | 1674.873 | 29 | 167 | 0.94 | 67.44 |
| 10 | Somerset County, Maine | 2539 | 506 | 54100.000 | 224 | 2288 | 19.93 | 44.27 |
| 11 | Oxford County, Maine | 4985 | 23 | 2560.000 | 3 | 13 | 0.46 | 13.04 |
| 12 | Waldo County, Maine | 3554 | 297 | 23900.000 | 108 | 368 | 8.36 | 36.36 |
| 13 | Lincoln County, Maine | 5213 | 74 | 339.000 | 22 | 34 | 1.42 | 29.73 |
| 14 | Franklin County, Maine | 2955 | 8 | 83.300 | 1 | 1 | 0.27 | 12.50 |
The county summary can also be mapped to compare testing coverage and the prevalence of results above the selected 20 ppt threshold across Maine.
The maps are interactive. Pan and zoom to explore the results and select counties for additional information.
Private Well Testing Coverage by County
This map compares the number of private water supply sample points represented in the testing data with the number of located wells represented for each county.
The resulting percentage provides a county-level measure of testing coverage within the represented data. The records from the testing and well datasets are aggregated by county rather than matched well by well.
Tested Private Wells with Results Above 20 ppt
This map compares Maine counties based on the percentage of tested private water supply sample points with at least one concentration result above the 20 ppt threshold used in this demonstration.
This percentage is calculated within the testing data by comparing sample points with results above 20 ppt with all tested private water supply sample points represented for each county.
Code and Query Resources
View the notebook used to run the queries, calculate the county summaries, and generate the interactive maps.
Additional Information
For current information about PFAS investigation, testing, and standards in Maine, visit the Maine Department of Environmental Protection.