Groundwater threats and private wells
Session Chair: John Peckenham, Mitchell Center, UMaine
Session abstracts:
Impacts to Water Supply Wells from Closed Municipal Landfills in Maine
Richard Heath, Richard Behr and Robert Birk
Maine Department of Environmental Protection, Augusta, Maine
Maine has approximately 414 municipal landfills including 15 currently licensed operating sites, 388 closed sites, and 11 inactive sites which have not undergone an approved closure. Many municipal landfills began operation in the 1950’s and 60’s. Hundreds of these unlined attenuation landfills continued operation until the early 90’s Today many of these inactive or closed landfills threaten ground and surface water quality because of inappropriate siting, inadequate design or improper operation. In 1988 the Maine Legislature created the Landfill Closure and Remediation Program to oversee the closure and maintenance of landfills that pose threats to public health and the environment. Investigations performed under this program have revealed numerous instances where water supply wells have been impacted by landfill related contamination. Recent residential development of properties near closed landfills pose a threat to newly installed private water supplies.
Several case studies are presented where contaminants including volatile organic compounds, arsenic, and other landfill related constituents were present at private water supply wells. Remediation of these impacts included point of entry filtration, extension of public water supply lines, and purchase of properties.
Investigation of road-salt constituents in bedrock aquifers in Maine
Charles Schalk and Joshua Katz
U.S. Geological Survey, Augusta, ME
Data collected in the past by Maine Department of Transportation (MDOT) indicate that road-salt constituents in bedrock aquifers do not behave the same as those in unconsolidated aquifers. Studies have shown that road-salt constituents tend to flush through unconsolidated aquifers relatively quickly and predictably, whereas the MDOT data seem to show that road-salt constituents move much more slowly through bedrock aquifers (at best) or accumulate in these aquifers (at worst).
Hypothesizing that transmissive fractures are playing a significant role in the persistence of road-salt constituents in bedrock aquifers, the U.S. Geological Survey (USGS) and MDOT began investigation of the timing and mechanisms of flow and road-salt transport in bedrock aquifers adjacent to State highways in Maine. Data being collected include continuous water levels, specific conductance, and water temperature in as many as eight wells; some of the data are being reported in real time. Borehole geophysical investigations, begun in the autumn of 2007 and scheduled to be completed in the spring of 2008, will be used to identify transmissive fractures and, consequently, appropriate sampling depths for road-salt constituents in the wells. The data-collection effort will span two winters and one summer. USGS and MDOT anticipate that data collected throughout the winter of 2007-08 will provide a good basis for conceptual models of the interactions among fractured bedrock, concentrations of road-salt constituents, and recharge events.
Salt Contamination of Private Wells: It’s Not as Simple as It May Seem
Keith Taylor 1and Robert G. Gerber2
1 St.Germain & Associates, Westbrook, Maine
2 Sebago Technics, Inc., Westbrook, Maine
Salt contamination of private wells is familiar to many, but the simple scenario of a salt pile leaching to a nearby private well may be the exception rather than the rule. Case studies from Raymond, Windham, and Brunswick show salt contamination from road spreading rather than storage piles, and neither the geology nor topography were obvious clues as to the source. In two cases, bedrock topography and structure combined to make the private wells highly susceptible to contamination. The solutions to road salt contamination are similarly not always as simple as drilling a new well. An understanding of subsurface geology was critical to solving the contamination problem at these sites. Other case studies from Windham and Scarborough show salt contamination of private wells whose origin may have little or no connection to road salt. Mineralized discharges from a water softener and trapped glacial-era seawater were identified as a contributor to or the primary source of the salt contamination rather than storage piles or road applications. Identifying the source of road salt contamination requires a comprehensive assessment of geology, topography, land use, and geochemistry.
A Case Study of Microorganisms Associated with Private Wells with High Levels of Arsenic Located in Northport, Maine
Jennifer M. Weldon (student) and Jean D. MacRae
Dept. of Civil and Environmental Engineering, University of Maine, Orono, ME
Consumption of arsenic laden drinking water can cause a variety of health effects. In Maine, approximately 40% of residents obtain their drinking water from private wells. Many of these wells contain arsenic in excess of the EPA limit of 10 ppb. Since there is no requirement to test private well water, thousands of Mainers may unknowingly be exposed to high arsenic concentrations.
For arsenic to occur in groundwater it must be present in aquifer materials and conditions must be favorable for arsenic release. Many microorganisms are capable of accelerating natural weathering processes in groundwater as well as altering arsenic speciation in groundwater. Microorganisms can reduce arsenate, As (V) to the more toxic and mobile form arsenite, As (III), via respiratory and detoxification mechanisms. Other microorganisms can alter the iron oxyhydroxides that coat aquifer materials and bind arsenic to the surfaces, causing the arsenic to be released. As the redox potential of the groundwater is lowered, these microbial activities that can result in an increase in total arsenic as well as an increase in arsenite are favored.
The microbial populations in groundwater taken from four wells with different arsenic concentrations from a single aquifer in Northport, ME were identified using molecular biological techniques. A comparison of microbial sub-groups and water chemistry parameters is providing new insight into the relationships between microorganisms and chemicals in the subsurface. The wells were also sampled 5 months apart and temporal variations in the microbial communities are being examined.
MtBE After the Ban
James M. Tarr and
Adam M. Galonski
Corporate Environmental Advisors, Inc., Concord , NH
Recent groundwater contaminant concentration data from twenty-five (25) active retail gasoline stations in New Hampshire were compared with historic data from the same sites to evaluate the overall impact of the State of New Hampshire banning the use of methyl tertiary butyl ether (MtBE) on January 1, 2007 as a part of its Oxygen Flexible Reformulated Gasoline (OFRFG) program. The data was statistically evaluated to determine the efficacy of eliminating MtBE from supply tanks. Preliminary findings will be discussed as well as outlining the long term study plans.
Spatial Patterns of Rural Water Quality Derived from Wells in Three Maine Communities.
Teresa Thornton1 and John Peckenham2
1
Mount Saint Mary’s College, Newburgh, NY
2
Mitchell Center, University of Maine, Orono, ME
About 40 percent of the people in Maine drink water from private water wells. There is a growing concern that communities will not have the water resources needed to support future populations. Private drinking water supplies are of a particular interest because they are neither regulated nor tested frequently. Development and commercial land-uses may affect both the quantity and quality of groundwater. Although the regulatory environment is set-up to protect groundwater resources, varied approaches to management and enforcement may not be sufficient to ensure future potability. Current research is quantifying how land-use affects groundwater quality on a town scale (kilometers). The test case has studied how gravel mining has affected water quality in towns in Hancock and Waldo Counties . Three years of data collected from private wells in collaboration with students in grades 5 to 12 will be presented that show changes in spatial patterns of water quality. Preliminary conclusions include evidence of elevated risks from road salt and nitrates. However, the road salt risk is most strongly associated with roads relative to other types of land uses.
Bedrock Geology Control of Domestic Well Water Radon and Uranium Concentrations in Greater Augusta , Maine , USA
P.E. Smitherman1, C.T. Hess1, Y. Zheng2, M. C. Loiselle3, C. W. Culbertson4
1 Dept. of Physics and Astronomy, UMaine, Orono, ME
2 Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY
3 Maine Geological Survey, Augusta, ME
4 USGS, Maine Water Science Center, Augusta, ME
A collaborative study with Columbia University and the University of Maine Department of Physics collected well water samples from 1130 private residences in the Augusta , Maine area in 2006 and 2007. Radon concentrations for both years were analyzed at the University of Maine . Uranium concentrations for the 2006 sample set were analyzed by ICP-MS by the Columbia team at CUNY. The radon and uranium data are both lognormally distributed with geometric means of 2780 pCi/L for radon and 1.02 µg/L for uranium. Maximum concentrations of 208,600 pCi/L for radon and 484 µg/L for uranium were measured. Radon and uranium concentrations in well water are mapped together with township, granite pluton and metamorphic grade information showing a confirmation of the correlation of radon concentration with granite plutons, with a geometric mean of 5460 pCi/L on the plutons. Uranium is similarly correlated with a geometric mean of 4.68 µg/L on the plutons. Both radon and uranium concentrations are shown to be higher on the higher metamorphic grades of bedrock. Radon is also correlated with uranium with a Pearson correlation of 0.39 and a slope for the regression fit of 0.25. A secular equilibrium calculation shows theoretical radon concentrations using the measured concentrations of uranium. This calculation gives supported radon concentrations much lower than the observed concentrations. Current work is focused on correlations between high chloride and high radium in the water samples. Radium is being measured by delayed recounting of the high radon and high uranium samples.
