Current Environmental Conditions
Onsite Groundwater and Response Action
Information on the groundwater quality at the former Kop-Flex facility has been gathered from the sampling of onsite monitoring wells. Evaluation of the historical monitoring data shows that concentrations of certain VOCs are present above the applicable groundwater standards in the surficial aquifer. The affected area forms a slightly elongate plume of VOC containing groundwater with the long axis oriented in a generally east-west direction consistent with the overall flow paths in this aquifer. Groundwater samples collected from wells along the western (i.e., hydraulically downgradient) portion of the site show that the surficial VOC plume does not extend beyond the property boundary. VOC concentrations above the groundwater standards have also been detected in samples from the deeper portion of the Lower Patapsco aquifer. In this part of the aquifer system, VOC impacts extend southward off the former Kop-Flex property.
Hydraulic containment via the pumping of VOC-containing groundwater was selected as the response action to address the impacted aquifers at the site under both the MDE VCP and the EPA Administrative Order on Consent. A network of shallow extraction wells installed within the surficial aquifer and deep extraction wells completed in the deeper portion of the Lower Patapsco aquifer would serve to contain the VOC-affected groundwater to the site. Surficial aquifer extraction wells would be located in the western portion of the site near the leading edge, or front, of the shallow VOC plume. Extraction wells to control VOC migration in the deeper portion of the Lower Patapsco aquifer would be located along the downgradient (south) property boundary. The combined flow from the extraction wells would be treated to remove the contaminants and the treated effluent discharged to Stony Run pursuant to a discharge permit issued by MDE.
Although potable water at the former Kop-Flex site is obtained from the municipal water system, there is no restriction on the use of groundwater at the site. However, such a restriction is required under the Administrative Order on Consent entered into by EMERSUB 16 and EPA. Therefore, a restrictive covenant will be enacted to prohibit the use of groundwater at the former facility property. The groundwater use restriction will be recorded in the county land records.
Groundwater System Construction and Start-up
Pre-construction activities for the groundwater extraction and treatment system included the abandonment of existing monitoring wells to facilitate the property redevelopment and completion of a field demonstration test for the proposed groundwater sampling method to be used for the response action. During January 2017, a total of 15 surficial aquifer monitoring wells and 5 deep wells were abandoned in-place in accordance with the Maryland well regulations. The Response Action Plan (RAP) proposed the use of a passive sampling device (HydraSleeve® sampler) to collect groundwater samples to monitor changes in the VOC concentrations during operation of the extraction and treatment system. A field demonstration test was conducted in the spring of 2016 to evaluate the applicability and performance of the proposed sampling device to collect representative groundwater samples from the site. Based on the field test results, it was concluded that VOC concentrations in the HydraSleeve® samples are similar to the concentrations detected in historical samples collected using traditional sampling methods. (A complete discussion of the sampling data evaluation is provided in the July 2016 HydraSleeve® Field Demonstration Study Report.) Given this finding, the use of the HydraSleeve® sampling device was recommended for the long-term groundwater monitoring program at the site. MDE and EPA provided conditional approval for the use of this sampling method at the Site, with final approval pending the collection and evaluation of additional groundwater sampling data.
Construction of the groundwater remedial system was initiated in mid-September 2016 and completed in early March 2017, in accordance with the engineering design described in the approved RAP. VOC-containing groundwater is extracted from three shallow extraction wells and two deep extraction wells. The extracted groundwater is routed via underground piping to the treatment system building. The treatment system includes equipment for the following processes:
- iron removal via the addition of an iron sequestering agent,
- suspended solids removal,
- adsorption of VOCs and 1,4-dioxane using a specialty synthetic resin,
- pH buffering via the addition of caustic soda, and
- in-line aerators to increase dissolved oxygen levels.
The treated water is discharged to Stony Run in accordance with the requirements specified in the National Pollutant Discharge Elimination System (NPDES) permit issued by MDE, which became effective in November 2016. Detailed information on the installation of the extraction wells, and water conveyance and treatment systems is provided in the Corrective Measures Implementation (CMI) Report.
Given the pre-construction abandonment of several monitoring wells, additional wells were installed during the system construction phase to augment the remaining well network. Five shallow and two deep monitoring wells were installed at the site in accordance with the RAP. The shallow monitoring wells were located in the western portion of the Site to monitor the conditions in the surficial aquifer in response to pumping. The deep monitoring wells were located on the southern portion of the site to monitor the aquifer response to pumping from the deep recovery wells.
Baseline groundwater samples were collected from the monitoring and recovery wells in December 2016 and January 2017 to characterize the pre-pumping conditions in the aquifer system. Groundwater samples collected from the shallow and deep monitoring wells had similar VOC concentrations to those collected during previous sampling events. Overall, lower VOC concentrations were detected in the groundwater samples from the wells screened in the deeper, (confined) portion of the Lower Patapsco aquifer compared to the surficial aquifer, with 1,1-dichloroethene (DCE) and 1,4-dioxane being the only VOCs present at levels above the applicable groundwater cleanup standards.in both aquifers. Evaluation of the sampling data indicates the distribution of 1,4-dioxane generally mimics that of 1,1-DCE within both aquifers. For the surficial aquifer, concentrations of 1,1-DCE and 1,4-dioxane decreased to trace and non-detect levels in samples collected from wells situated along the western (downgradient) Site boundary. No VOCs were detected at concentrations exceeding applicable cleanup criteria in samples from the shallow monitoring points near the downgradient property boundary. The baseline sampling results will be evaluated with respect to data obtained during the operation of the groundwater extraction and treatment system to assess capture of the VOC plumes and removal of contaminants from the aquifer system.
System start-up was initiated on March 10, 2017, with the groundwater pumping rate gradually increased over the first few weeks of operation while the treatment equipment and control settings were adjusted to optimize system operation. Continuous system operation began on March 29, 2017, with groundwater extraction from all five recovery wells.
Groundwater System Operation
Performance of the treatment system is monitored via the collection and analysis of water samples from various points in the treatment process. During the initial months of operation, no VOCs were detected in the treated water samples at concentrations above the method reporting limits. Comparison of these results with data for the untreated water indicates a 100% removal efficiency for these compounds. Therefore, the treatment system is achieving the necessary performance requirements with respect to the site contaminants. Evaluation of water level data obtained during continuous system operation indicates that groundwater extraction from the shallow and deep recovery wells at the current pumping rates should be able to capture the VOC plumes on the property and prevent any future offsite transport of site-related VOCs in the aquifer system.
EMERSUB 16 plans on continuing the extraction and treatment of VOC-affected groundwater from both the surficial aquifer and deeper portion of the Lower Patapsco aquifer in accordance with the requirements specified in the approved RAP. In conjunction with system operation, groundwater level and water quality monitoring activities will be regularly conducted to gather data for evaluating the effect of pumping on the aquifer system.