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 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, except for one, were decommissioned and the homes connected to the municipal water system. For the other residence, 1,1-DCE is present at concentrations that could pose a health risk unless the water is treated to remove this compound. This residence previously installed a whole-house water treatment system that is capable of removing 1,1-DCE to a level below the applicable groundwater quality standard. Additionally, 1,4-dioxane has been detected at concentrations below the risk-based action level; however, the existing treatment system cannot remove this compound from the water. Given the presence of site-related VOCs in the well water, quarterly sampling is conducted to monitor VOC concentrations in the untreated and treated water and ensure the water is safe for potable use.
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 EPA conditionally approved the installation of the replacement well in January 2017, provided the new well is completed in the shallow (uncontaminated) portion of the aquifer system and sampling indicates 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.
Evaluation of the available well information shows the residential wells in the areas south of Route 100 are primarily screened in water-bearing sand deposits within the Lower Patapsco aquifer. The Lower Patapsco aquifer is characterized by a regionally extensive clayey layer with overlying and underlying zones comprised of sand or inter-layered sand and clay. The deeper sand zone represents the primary interval for the migration of VOCs from the Site. The presence of VOCs concentrations exceeding the groundwater quality criteria appears to be related to the well construction, particularly the placement of the screen interval within the portion of the aquifer serving as the primary zone for contaminant transport.
Groundwater Monitoring Activities
Additional groundwater investigation activities have been conducted to further assess the offsite VOC distribution. These investigation activities involved the installation of nine monitoring wells in five different areas during the summer of 2014. Following installation, the offsite monitoring wells were sampled quarterly, with the first sampling event conducted in September 2014.
No site-related VOCs have been detected in the samples from the two offsite monitoring wells screened in the upper-most unconfined zone of the Lower Patapsco aquifer. Chlorinated VOCs and 1,4-dioxane associated with the Kop-Flex site are limited to the sand deposits present in deeper (confined) portions of this aquifer.
An iso-concentration map showing the 1,1-DCE distribution within the impacted interval of the Lower Patapsco aquifer in both onsite and offsite areas is shown in Figure 1. In the area south of Maryland Route 100, levels of 1,1-DCE above the groundwater quality standard have been detected in samples from the paired wells - MW-25D-130 and MW-25D-192 - in the Harmans Woods residential area, with lower concentrations in the samples from the deeper well (MW-25D-192). Additionally, the concentration of 1,4-dioxane in both well samples 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 very low concentrations of the site-related VOCs. The concentrations of 1,4-dioxane detected in samples from MW-33D-295 are slightly above the MDE risk-based action level. Overall, the areal extent of VOC-affected groundwater in the Lower Patapsco aquifer downgradient of the former Kop-Flex facility is generally delineated by the offsite monitoring well locations. 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. A statistical evaluation of the sampling data for these wells suggests stable or decreasing trends in the concentrations of site-related VOCs, indicating some degree of stability concerning the extent of the VOC plume in the area.
Based on evaluation of the sampling data, the deep sand zone in the Lower Patapsco aquifer represents the primary interval for the migration of VOCs from the former Kop-Flex facility. The regional southeastward dip of this and other hydro-stratigraphic units within the aquifer results in a corresponding increase in the depth of the VOC plume in the downgradient (southeast) direction. Another characteristic is the vertical extent of VOC-impacted groundwater, with the highest concentrations occurring in the upper portion of the sand unit near the MW-25 location and the lower portion of this unit further southeast at the MW-33 location. The apparent ‘diving’ of the VOC plume core is believed to reflect the variations in the permeability of the aquifer materials and the downward seepage of ‘clean’ water from overlying portions of the aquifer sequence to the deep sand zone.
Additional groundwater monitoring wells are to be installed in the residential areas south of Maryland Route 100 in accordance with the Offsite Groundwater Monitoring Plan (Offsite GWMP) approved by MDE and EPA. Since these wells are to be installed in public road right of ways, the Anne Arundel County Department of Public Works needs to issue a Right-of-Way (ROW) permit for each location before conducting the well installation activities. Upon issuance of the ROW permits, EMERSUB 16’s consultant will oversee the installation of the additional monitoring wells and initiate the groundwater monitoring program specified in the Offsite GWMP for the new and existing offsite wells.