Historical records discovered during construction of a commerical building indicated that a deep well with steel casing was likely present within a portion of the project site. Regulatory officials halted construction and insisted that the presence (or absence) of the well be confirmed. If the well was present, it was required that the well be exposed so that it could be property abandoned. Because of earth work activity at the site, it was suspected that the well could be 5 to 10 ft below current grade.
GeoView performed a geophysical investigation across a one-acre area where the well was reported to be located. Because of the anticipated strong magnetic response created by the vertical steel casing of the well, a total field magnetics survey was chosen as the appropriate method. The survey was conducted using a Geonics G-859 cesium vapor magnetometer. This instrument is capable of detecting metal-cased wells to depths of several tens of feet below grade. The magnetic survey was conducted along transects spaced 5 ft apart with an integrated sub-meter GPS to eliminate the need for laying out a survey grid, thereby reducing project field time and cost. Survey data was processed and analyzed on site, so that final results were available within 1/2 hour of completing the field work. A strong positive magnetic anomaly was identified within the survey area. A wooden survey stake was emplaced to mark the center of the anomaly and positioning data was recorded. Subsequent excavation activity at the staked location confirmed the presence of the well at a depth of 8 ft below grade. The well was then properly abandoned and construction activity was allowed to commence.