Tuesday, August 11, 2020
Sinkhole Assessment

Project Location:
Eastern Pennsylvania

Converse Responsibilities:
Hydrogeologic Investigation, Groundwater Tracer

Our client sought to assess the hydraulic communication between a sinkhole and inflow to deep mine workings at their Pennsylvania limestone underground mine. Facility and local information was compiled and evaluated and Converse recommended the execution of a groundwater tracer study. The tracer methodology included the use of sodium fluorescein and passive granular activated carbon (GAC) absorbers to provide a qualitative assessment of the hydraulic communication issue.Brooks Sinkhole Assessment

A survey of local water supply wells, springs and other hydrologic features within an approximately 5-mile radius of the mine facility was performed. Down gradient groundwater discharge locations and potentially affected water users were evaluated. Permission to deploy tracer collector devices was obtained from the owners of local water supply wells and springs. Due to the presence of residential water supply wells and a large water supply spring at the Pennsylvania Fish and Boat Commission (PAFBC)’s nearby fish hatchery, the tracer study was designed to be conducted in two (2) phases, beginning with a low-level tracer injection and then following up with a higher-level tracer injection. Agency authorizations were obtained and notifications were made to PAFBC, PA Department of Environmental Protection (PADEP) and the local township.

Diffuse transmission of tracer was observed at down gradient springs. Strong tracer presence was observed at mine inflow points and direct hydraulic communication between the sinkhole and the deep mine workings was demonstrated.