Reports
Summary of hydrogeologic data from a test well (1,725 ft.) drilled in Tuckahoe State Park, Queen Anne's County, Maryland
1987, Andreasen, D.C. and Hansen, H.J.
Open File Report 87-02-3
Abstract
Test well QA-Ef 29 was drilled to a depth of 1,725 feet during the spring of 1986 at the site of a proposed fish (striped bass) hatchery in Tuckahoe State Park, near Queen Anne in southeastern Queen Anne's County, Maryland. The test well demonstrated that the Magothy and upper Patapsco aquifers could produce ground water in sufficient quantity (1 to 1.5 million gallons per day) and of suitable quality to meet the requirements of the hatchery operation.
At the well site the Magothy aquifer consists largely of gray to tannish white, fine to medium grained, occasionally coarse, quartzose sand interbedded with dark gray clayey and organic-rich layers. The upper Patapsco aquifer is characterized by light gray to tan, medium to coarse grained, quartz sand interbedded with tough mottled clays; layers of cemented sandstone occur chiefly within the lowest screened sand.The pilot hole was converted to a production well by setting five sections of 8-inch diameter well screen from 1,110 feet to 1,120 feet and from 1,135 feet to 1,180 feet in the Magothy aquifer. In the upper Patapsco aquifer screens were set from 1,195 feet to 1,210 feet, 1,230 feet to 1,270 feet, and 1,285 feet to 1,315 feet. A total of 140 feet of screen was set.
The aquifer properties of the combined Magothy and upper Patapsco sands screened in QA-Ef 29 were estimated by a 24-hour pumping (and recovery) test. A constant discharge rate of about 700 gallons per minute resulted in a water-level decline of 164.5 feet from a pre-pumping static water level 62.5 feet below land surface. The 24-hour specific capacity of the well was 4.3 gallons per minute per foot of drawdown with a well efficiency of approximately 70 percent. The transmissivity of the screened sands was 1,585 ft2/day calculated from water-level data measured during the recovery phase of the test .
Over a 5-week period the static water level in the well fluctuated between about 0.6 and 1.0 foot below sea level and exhibited a close correspondence to changes in barometric pressure. The barometric efficiency of the well was determined to be 39 percent and was used to calculate an approximate aquifer storage coefficient (0.00021). Smaller, semidiurnal variations of less than 0.05 foot were also observed and may be caused by either earth or ocean tides.
The quality of water from the Magothy and upper Patapsco aquifers is generally good. It is low in chloride (2 mg/L) and sulfate (18 mg/L), slightly acidic (pH = 6.2), soft (hardness = 12 mg/L) and relatively low in dissolved solids (124 mg/L, predominantly sodium bicarbonate). The dissolved iron concentration (0.55 mg/L ) is slightly above the recommended level (0.3 mg/L). The water contains no dissolved oxygen. The geothermal gradient was about 1.53°F/100 feet with a well head water temperature of 77°F (25.1°C). For optimum hatchery operation the water must be aerated to provide dissolved oxygen. Aeration may also be an effective treatment for raising the pH due to carbon dioxide degassing and for decreasing dissolved iron concentrations by ferric hydroxide precipitation.
