MGS presented research at the 2018 Maryland Groundwater Symposium, September 27, 2018

Effects of Increased Withdrawals from the Aquia Aquifer on the Mayo Peninsula, Anne Arundel County, Maryland with an Evaluation of Water Quality

Tiffany VanDerwerker

ABSTRACT

The Mayo Peninsula in east-central Anne Arundel County, Maryland relies primarily on the Aquia aquifer for drinking-water supply. The deeper Magothy aquifer is also utilized but to a much lesser extent. The lifting of a building moratorium in 2017 on the peninsula associated with increased capacity for treating sewage effluent may result in the construction of up to approximately 630 homes. The potential effects of increased domestic water withdrawals to support the possible growth on water levels and on the brackish-water interface in the Aquia aquifer were evaluated. In addition, water quality of the Aquia aquifer, both natural and affected by anthropogenic contaminants that might constrain the use of the Aquia aquifer for domestic potable supply was also evaluated.

To characterize water quality of the Aquia aquifer, 24 wells were sampled during this study. Three wells with chloride concentrations between 284 and 386 milligrams per liter (mg/L) and a Cl:Br ratio between 249 and 392 were determined to be affected by brackish-water intrusion, located near the shoreline (less than 600 feet); Eight wells with chloride concentrations between 81 and 221 mg/L and a Cl:Br ratio greater than 529 were determined to be affected by road salt and; 13 wells were determined to be freshwater. The uppermost portion of the Aquia aquifer is weathered (maximum depth of approximately 60 feet below land surface) and produces water that may be acidic (pH less than 6.5). Cadmium and chloride concentrations tend to be greatest in that portion of the aquifer. The deeper Magothy aquifer, an alternative drinking water supply on the peninsula, is less susceptible to surface contamination and brackish-water intrusion; however, iron concentrations can range from 14.0 – 26.0 mg/L, requiring treatment for domestic supply.