Reports
Compilation and review of GIS-based ground-water quality data from multiple databases for Garrett County, Maryland
2014, Bolton, D.W., Quinn, H.A. and Andreasen, D.C.
Administrative Report 14-02-02
Key Results
An ArcGIS database of ground-water quality data was constructed for Garrett County, Maryland. Data sources included the Garrett County Health Department PatTrac database and radon records, the U.S. Geological Survey National Water Information System, the Maryland Department of the Environment Public Water Supply database, and the Maryland Geological Survey methane database. Data were obtained from more than 2,200 sites (including both wells and springs). Four parameters— arsenic, chloride, manganese and radon—were selected for a more focused review and analysis by both geographic information system (GIS) and statistical methods. These and other constituents were examined with respect to regulatory levels. Key results from this project are as follows:
- Arsenic concentrations exceeded the Maximum Contaminant Level of 0.010 milligrams per liter in about 7 percent of sites sampled. About 20 percent of sites in the Hampshire Formation exceeded the Maximum Contaminant Level; the exceedance rate was less than 8 percent for the other geological formations.
- Chloride concentrations of sites exceeded the Secondary Maximum Contaminant Level of 250 milligrams per liter in about 3 percent of all sites.
- Manganese exceeded the Secondary Maximum Contaminant Level of 0.050 milligrams per liter in about 55 percent of all sites. The highest percentage of manganese exceedances was from the Pottsville Formation (about 70 percent), and the lowest was from the Hampshire Formation (39 percent). Manganese and iron concentrations were positively correlated.
- Radon exceeded 4,000 picocuries per liter in samples from three sites, with a maximum of 32,800 picocuries per liter.
- Maximum Contaminant Levels were exceeded at a small number of sites for barium, fluoride, lead, nitrate, nitrite, gross alpha-particle activity, and radium-226-plus-radium-228. Many of these exceedances were from monitor or observation wells, rather than water-supply wells.
- Additional data review and/or water-quality testing is recommended for sites where very high concentrations of regulated water-quality constituents were observed.
- Lack of information on sampling, collection, and analytical procedures limits the amount of interpretation possible on the combined data set.
- Baseline water-quality testing is recommended for private wells prior to the development of the Marcellus Shale for natural gas. This would provide a basis for determining if ground water has been altered by gas-development activities.
- Garrett County should consider conducting a sampling program to test a representative number of private wells for regulated chemical constituents that are not currently tested in order to better assess and characterize concentrations of these chemicals in ground water in the county. This is recommended regardless of whether the Marcellus Shale is developed or not.
- Additional documentation and refinements of the Garrett County Health Department PatTrac database could help facilitate construction of a more robust geographic information system-based information system. This includes addition of data fields for water-sample type and source, and more information on location and elevation data, well-permit number, constituent units, and verification of property information.
- The databases used in this study, which were derived from different county, state, and federal government sources, required extensive reformatting in order to link them to one another. Data interoperability would be greatly enhanced by developing and implementing strategies for better linkages between databases.
