TERRAIN CONDUCTIVITY INVESTIGATION OF THE DAM AT ALPINE LAKE, WEST VIRGINIA

In this study, terrain conductivity surveys were undertaken over an area bordering the dam at Alpine Lake in Terra Alta, West Virginia. The sudden development of a spring some 600 yards from the dam raised local landowners’ concerns that the dam might be leaking. Spring effluent was significant enough to wash out a large ditch and threatened to undercut a local road just a few feet away.

Terrain conductivity surveys were undertaken near the spring using the Geonics EM31 terrain conductivity meter. Initially, stations were occupied every 20 feet in a 300 foot by 80 grid centered up-gradient of the spring. There are two possible sources for this leak. A high conductivity zone associated with subsurface drainage was mapped in the nearby area, but did not lead in the direction of the dam. Eventually the survey grid was expanded to include 4 additional survey grids so that high conductivity regions between the dam and spring could be accurately followed. Individual survey grids ranged in size from 300 feet to 440 feet in length by 140 feet to 300 feet in width.

A magnetic survey was also conducted in the vicinity of the dam to evaluate the possibility that terrain conductivity anomalies might be associated with buried metallic sources. The magnetic survey confirmed that terrain conductivity anomalies were associated with conductive groundwater, rather than from metallic debris.

Initially, there appeared to be two possible source areas for the spring. The first, and most obvious source was the dam. The second possibility was associated with an old stone quarry. The old quarry high wall bordered the re-contoured mine spoil, which now serves as a golf course. Contour maps of the terrain conductivity data indicate that the newly developed spring can be traced beneath the golf course to the base of the old stone quarry high wall. Inspection of the area confirmed that springs near the base of the high wall were the most likely source of the newly formed spring.

The combined use of terrain conductivity and magnetic surveys proved to be a low cost and effective approach to identify the source of this newly developed spring.