Relations among water levels, specific conductance, and depths of bedrock fractures in four road-salt-contaminated wells in Maine, 2007–9

Many rural communities depend on bedrock wells as a primary water source, which raises the issue as to whether increasing amounts of salt application are affecting bedrock water quality and to what degree. Through wellbore profiling, this study investigated changes in specific conductance in two crystalline bedrock wells at the University of Connecticut in Storrs, CT, from 2003 to 2016, with particular emphasis on the impacts of increased salt application with a change in deicing practices at the university after 2009. Hourly specific conductance measurements were collected in 2014 to determine how water source may affect wellbore concentrations seasonally. Chloride was found to be highly persistent in the bedrock, with concentrations consistently increasing from 2003 to 2016 despite year-to-year variations in salt application. A dramatic increase in chloride occurred in the wellbores in response to the change in deicing practices, with an immediate response in fractures having a direct connection to the overburden. In light of the long-term implications of road salting on subsurface chloride contamination, this study argues that consideration be given to deicing management strategies to reduce road salt contamination.

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“…This relationship is comparable with those established in Harte and Trowbridge (2010) and Schalk and Stasulis (2012).…”

Section: Methodssupporting

confidence: 88%

Impacts of Road Salting on Water Quality in Fractured Crystalline Bedrock

2017

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“…In this study, we found no correlation between well depth and sodium and chloride concentration. However, the groundwater in our study was deep, bedrock groundwater (average = 88.3 m), which may be more influenced by the proximity to active fracture zones that can occur at any depth and that connect bedrock groundwater to surface features such as streams or the atmosphere (Schalk and Stasulis, 2012). …”

Section: Discussionmentioning

confidence: 93%

“…It is clear that substantial quantities of road salt can infiltrate the deep groundwater, threatening drinking water supplies (Schalk and Stasulis, 2012; Betts et al, 2015), and that it may take decades or more for the salt currently in groundwater to flush out should road salt use be curtailed or eliminated (Kelly et al, 2008; Novotny and Stefan, 2010; Betts et al, 2015; Gutchess et al, 2016). Our results indicate that groundwater sodium and chloride concentrations are not evenly distributed and are affected by specific landscape characteristics (Table 3).…”

Section: Discussionmentioning

confidence: 99%

The Distribution of Road Salt in Private Drinking Water Wells in a Southeastern New York Suburban Township

et al. 2018

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We used a GIS analysis of sodium and chloride concentrations in private water wells in a southeastern New York township to describe the pattern of distribution of road salt in aquifers tapped for drinking water. The primary source of road salt was sodium chloride, and sodium and chloride concentrations were significantly correlated ( = 0.80, < 0.01). Chloride concentrations in wells increased as the percentage of impervious surface cover (ISC) within a 250-m radius around wells increased ( = 0.87, < 0.01) and declined with increasing distance to the nearest road ( = 0.76, < 0.01). Wells that were located lower in elevation than the nearest road had higher concentrations of chloride than wells that were higher than the nearest road, but this occurred only when the nearest road was >30 m from the wells ( < 0.01). Chloride concentrations were not affected by well depth or adjacent road type (major or minor roads). Surface geology and hydrologic soil class had significant effects ( < 0.01) on chloride concentrations in wells, with porous surface geology types and well-drained soils having higher concentrations; these effects may be confounded by the fact that ISC was more likely to occur on these permeable surface geology and soil types. Hot and cold spot analysis revealed substantial unevenness in chloride concentrations. Results for sodium were similar to those for chloride. Overall, these results indicate that road salt contamination of groundwater is unevenly distributed and is affected by landscape factors that can be used to guide well testing and best management practices of deicing salt distribution.

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“…Many investigators develop linear regression models to estimate chloride concentrations from specific conductance by using the untransformed measured values (for example, Peters and Turk, 1981;Britton and others, 1983;Cain, 1987;Blasius and Merritt, 2002;Watson and others, 2002;others, 2007, 2008;Perera and others, 2009;Corsi and others, 2010a,b;Denner and others, 2010;Harte and Trowbridge, 2010;Trowbridge and others, 2010;Windsor and others, 2011;Morgan and others, 2012;McDonald and others, 2012;Schalk and Stasulis, 2012). All 14 of these reports have one or more equations with negative intercept values; these equations will produce negative chloride concentrations for a positive conductance value.…”

Section: Cationsmentioning

confidence: 99%

Methods for evaluating potential sources of chloride in surface waters and groundwaters of the conterminous United States

Granato¹,

DeSimone²,

Barbaro³

et al. 2015

Open-File Report

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vii 18. Graph showing range of chloride concentrations estimated from specificconductance values measured at 1-minute intervals in highway runoff during runoff events with one or more estimated values that exceed the 230-milligramsper-liter criterion continuous concentration for chloride in receiving waters at U.S. Geological Survey monitoring station 423027071291301 along State Route 2 in Littleton, Massachusetts, during the period from

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Relations among water levels, specific conductance, and depths of bedrock fractures in four road-salt-contaminated wells in Maine, 2007–9

Cited by 5 publications

References 24 publications

Impacts of Road Salting on Water Quality in Fractured Crystalline Bedrock

Impacts of Road Salting on Water Quality in Fractured Crystalline Bedrock

The Distribution of Road Salt in Private Drinking Water Wells in a Southeastern New York Suburban Township

Methods for evaluating potential sources of chloride in surface waters and groundwaters of the conterminous United States

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