THE EFFECTS OF JOINTING ON CONTAMINANT TRANSPORT IN THE NOSE OF AN ANTICLINE NEAR MOUTAIN TOP, LUZERNE COUNTY, PENNSYLVANIA

Trichloroethylene (TCE) contamination exists in residential wells in Mountain Top, Pennsylvania, which lies just SE of the axis of the Berwick anticline in the Appalachian Valley and Ridge physiographic province. The area is underlain by units of the Devonian Catskill Formation to depths of approximately 450 meters. The area has been glaciated, mantling the bedrock with up to 30 meters of mixed till and outwash deposits. A nearby industrial facility that used TCE as a degreaser is the most likely source of the contamination. TCE-contaminated water could have traveled over the ground surface, through the glacial material or through the underlying bedrock. Slope analyses in ArcGIS indicate surface contamination would have flowed to the northwest, but no TCE has been detected in samples of surface water or sediment NW of the facility. Water traveling through the glacial material would likely follow local groundwater flow south of the facility to a stream that runs WSW sub-parallel to strike. However, TCE traveled past the stream to reach the residential area, suggesting deeper flow paths may extend into the underlying bedrock. Bedrock is composed of fine- to medium- grained crossbedded sandstone, some interbedded siltstone and occasional conglomerate of the Duncannon Member of the Catskill formation. Because bedrock joints could potentially act as preferred pathways, joint orientation measurements were collected at various outcrops in and around Mountain Top using a Brunton compass and located using both GPS and topographic maps. The two prominent joint sets could be the result of a conjugate system that accommodated extension during the folding process, or they may reflect a combination of early Lackawana-phase deformation, followed by main Alleghanian-phase jointing. Jointing may also control stream orientations in multiple locations as inferred from topographic maps and orthophoto images. Based on our fracture measurements and the location of the TCE contamination, we suggest joints control deep groundwater flow. By overlaying the joint system on a topographic map and assuming the contaminant traveled from the site of known TCE contamination along the strike of the 045 trending joints, the TCE would end up in the contaminated residential areas.