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Virginia Beach Driller |
Problem: Virginia Beach is a rapidly growing city in southeastern Virginia with a limited supply of fresh water. Most of the city’s drinking water comes by pipeline from Lake Gaston, more than 100 miles to the west by way of Norfolk’s Western Reservoir System. Before 1998, Virginia Beach purchased up to 30 mgd (million gallons per day) from the city of Norfolk.
The Lake Gaston pipeline supplies water for most of the northern half of the city, but some northern neighborhoods and the southern half of the city relies solely on ground water. Privately owned wells provide ground water from shallow depths (generally less than 200 ft) in Virginia Beach. Supplies of ground water are limited, however, by poor quality in places. The taste of water from wells can be unpleasant to undrinkable in places because of chloride, iron, and (or) sulfide ions. At depths greater than approximately 200 ft, the water is generally too saline to drink. Most high production wells pumping from the shallow aquifers have resulted in salt-water contamination.
The city of Virginia Beach wants to preserve the limited supply of usable ground water in the shallow aquifers beneath the city for drinking water, irrigation, heat pumps, and possibly desalination. Toward that end, the hydrogeologic framework of the shallow aquifer system needs refined, patterns of ground-water flow need better definition, and the general quality of the shallow aquifers needs to be further defined.
To meet these objectives, the USGS in cooperation with the City of Virginia Beach has recovered continuous cores and down-hole geophysical logs from 7 test holes approximately 200 feet deep. Ten observation wells were installed at 5 of those sites. Water from these and other wells will be analyzed and the hydrogeologic framework of the shallow aquifer system will be refined. Numerical modeling and particle tracking methods will be used to simulate ground-water flow and flow paths beneath the southern watersheds of the city.