Geotechnical implications of subsurface cavities at Storeytown, New Brunswick

Abstract

The village of Storeytown, located approximately 80 km north of Fredericton, encountered problems during well drilling for a local water supply. There was loss of drill cuttings and water during the drilling process. This result suggested the occurrence of subsurface fractures or cavities resulting in a video investigation of the well. The video investigation revealed two locations of interest where the well appeared fractured. Published geology reports and local drilling history records were reviewed to identify previous occurrences of similar subsurface fractures. Water samples were collected at the well site and chemically tested by the Department of the Environment. Water testing indicated that Canadian Drinking Standard limits are exceeded for Manganese, iron, and sulfate. Manganese and iron were also found to increase at the fracture points in the well. Regional geology maps revealed a fault running approximately 2 km west of the Storeytown well location. A previous drilling project for coal exploration, the Carboniferous Drilling Project, revealed an elongated contoured high for Managanese following the local fault trend in the area. The fractures in the well are interpreted as being related to the regional faulting in the area. The high element concentrations at the points of discontinuity in the well, and the manganese contours, suggest the fault is open and the water is connected to a regional source. The occurrence of a large open fault in the area has implications for a seismic assessment.