Current Environmental Conditions
Offsite Groundwater and Response Action
Private Well Monitoring
Based on the finding of VOCs in the well installed immediately south of the former Kop-Flex facility in 2012, water samples have been collected from approximately 190 private water-supply wells to the south of the former Kop-Flex facility and Maryland Route 100 during four separate sampling phases. Detectable levels of VOCs were found in 150 water samples collected from these water-supply wells. Most of these detections consisted of trace to very low concentrations of methyl tertiary-butyl ether, an additive formerly used in gasoline, and/or trihalomethanes (especially chloroform), which are common byproducts in the disinfection of well water using chlorine. These VOCs are not associated with the Kop-Flex Site.
Site-related constituents of concern, (chlorinated VOCs and 1.4-dioxane) were detected in 22 of the well samples, with the majority of these wells located north of Reece Road. Water samples from ten wells screened in the deep aquifer zone along Twin Oaks Road and Old Camp Meade Road had site-related VOC concentrations above either federal or state groundwater quality standards, or state risk-based criteria. All of these wells have been decommissioned and the homes connected to the municipal water system. Chlorinated VOCs and 1,4-dioxane detected in water samples from wells not screened in the deep confined aquifer zone that extends to the south and east from beneath the Former Kop-Flex facility are related to contaminant sources other than the former Kop-Flex property.
The compound 1,1-DCE was also detected above the applicable groundwater quality standard in the sample from a well in the Andorick Acres neighborhood. Given the lack of public water mains in this residential community, EMERSUB 16 proposed installing a replacement well on the property to provide a new source of potable water. The MDE and USEPA conditionally approved the installation of the replacement well in January 2017, provided the new well is completed in the upper, uncontaminated portion of the Lower Patapsco aquifer system and sampling indicated the absence of site-related VOCs in the well water. In late February 2017, the replacement well was installed and connected to the residence and the exiting VOC-impacted well abandoned on the property. Subsequent sampling of the well water by the Anne Arundel County Bureau of Environmental Health and EMERSUB 16's consultant indicated that the treated water met the applicable water quality criteria and was safe for domestic use. A Conditional Certificate of Potability for the replacement well was provided to the homeowner by Anne Arundel County in early June 2017.
Review of the available well information shows that residential wells in the areas south of the former Kop-Flex property are completed in both the shallow and deep aquifer zones of the Lower Patapsco aquifer system. As mentioned above and depicted in Figures 1 and 2, the direction of groundwater flow is to the north and west in the shallow aquifer zone and south and east in the deep confined aquifer zone. Given the nature of groundwater flow within the aquifer system, the presence of VOCs related to the former Kop-Flex facility is limited to private wells screened within the deep confined aquifer zone that extends to the south and east from beneath the Former Kop-Flex facility, because this portion of the aquifer system afforded a pathway for the migration of contaminants southward from the onsite area. VOCs detected in water samples from private wells completed in other portions of the Lower Patapsco aquifer system are unrelated to releases and historical operations at the former Kop-Flex property.
Groundwater Monitoring Activities
Since 2014, groundwater investigation activities have been conducted to further assess the offsite contaminant distribution. These investigation activities involved the installation of three monitoring wells in the shallow aquifer zone, 12 wells in the deep aquifer zone, and 2 wells in the deeper Patuxent aquifer. These wells are located between 100 feet and 1.5 miles from the former Kop-Flex facility. At present, the offsite monitoring wells are sampled on a semi-annual schedule.
No site-related VOCs have been detected in the samples from the offsite monitoring wells screened in the shallow aquifer or the Patuxent aquifer, which is separated from the deep aquifer zone where site-related VOCs are believed to be present by a thick, predominately clayey unit (Arundel Clay). Chlorinated VOCs and 1,4-dioxane associated with the Kop-Flex site are limited to the sand deposits present in the deep confined aquifer. This data suggests that any VOC-contamination in offsite wells in the shallow aquifer stems from other source(s) and not from releases at the former Kop-Flex facility property.
In the area south of Maryland State Route 100, levels of 1,1-DCE above the groundwater quality standard have been detected in samples from the paired deep aquifer monitoring wells MW-25D-130 and MW-25D-192 in the Harmans Woods residential area, and well MW-30D-273 at the intersection of Twin Oaks Road and Old Camp Meade Road. Additionally, the concentration of 1,4-dioxane in samples from these deep aquifer monitoring wells exceeded the MDE risk-based action level. The sampling data for the deep monitoring wells located further to the south and east contained either non-detectable or low concentrations of the site-related constituents. The concentrations of 1,4-dioxane detected in samples from MW-33D-295 are slightly above the MDE risk-based action level. Other than the detections of 1,4-dioxane in the groundwater samples from well MW-33D-295, no site-related VOCs have been detected above the applicable groundwater quality criteria in any of the recent samples from the other downgradient monitoring points in the deep aquifer zone. A statistical evaluation of the sampling data for the wells indicates stable trends in the concentrations of site-related constituents, indicating some degree of stability concerning the extent of the VOC plume in the area. Overall, the extent of affected groundwater in the deep aquifer zone downgradient of the former Kop-Flex facility is delineated by the offsite monitoring well network.
Based on evaluation of the sampling data, the deep aquifer represents the primary interval for the migration of VOCs from the former Kop-Flex facility. The regional southeastward dip of the sandy and clayey layers within the Lower Patapsco aquifer system results in a corresponding increase in the depth of the VOC plume in the downgradient (southeast) direction.