Reports
Hydrogeology and stratigraphy of a 1,515-foot test well drilled near Princess Anne, Somerset County, Maryland
1990, Hansen, H.J. and Wilson, J.M.
Open File Report 91-02-5
Abstract
Well Som-Ce 95 was drilled on the grounds of the Eastern Correctional Institution, a State prison located near Princess Anne, Maryland. At present (1990) pumpage at the prison is solely from the Manokin aquifer. Som-Ce 95 was drilled to a depth of 1,515 feet with the purpose of identifying and testing a deeper aquifer that could potentially serve as an alternate water source.
A review of drilling, sampling, and geophysical logging data indicated that an upper Patapsco aquifer, stratigraphically equivalent to the Elk Neck Beds (Upper Cretaceous Palynozone III), offered the best alternate source of ground water at the site. A 6-inch diameter well screen was installed in fine to medium sand between, 1,135 feet and 1,200 feet below land surface. The well had a 24-hour specific capacity of 4.2 gallons per minute per foot at a pumping rate of 393 gallons per minute. Analyses of drawdown and recovery water-level data suggested an aquifer transmissivity of 1, 575 ft2/day to 1,650 ft2/day. The static water level was 7.15 feet below land surface or about 5.85 feet above sea level. A continuous water level hydrograph recorded during November 1989 showed small, semi-diurnal (about 0.1 feet) tidal fluctuations superimposed on broader fluctuations of less 0.5 feet.
A water sample was obtained during the pumping test and analyzed for major ions. The water has a total dissolved solids content of 829 mg/L and a specific conductance of 1,350 µS/cm. The water is a sodium (330 mg/L) bicarbonate (800 mg/L) type. Chloride (37 mg/L), sulfate (37 mg/L), and silica (12 mg/L) are relatively low. The fluoride concentration (3.6 mg/L) exceeds the second maximum contaminant level. The pH is 8.2 and temperature at discharge was 27.3°C.
Several Patapsco aquifers occurring below the tested interval were logged in Som-Ce 95 between 1,346 feet and 1,492 feet. These fine to medium sands record deep induction log resistivities (Ro = 13 to 18 ohm-m) similar to the sampled aquifer. The similar log resistivites suggest that the aquifers contain water of comparable quality.
