Current Environmental Conditions
Investigations conducted by Emerson in 1996 and 1997 identified volatile organic compounds (VOCs) in soil and groundwater in two areas at the facility; one below the southwest portion of the former manufacturing building (Area of Concern [AOC] 1) and one to the east of the former manufacturing building (AOC 2). The VOC impacts were attributable to the historic use of degreasing solvents by previous owners. Based on these findings, in July 1998, Emerson applied to enter the site into the Maryland Voluntary Cleanup Program. In April 1999, MDE notified Emerson that its application had been accepted and indicated that a response action plans must be developed for the site to address the identified environmental impacts.
Previous Remedial Activities
The response action for AOC 1 involved installing a dual-phase extraction (DPE) and soil vapor extraction (SVE) system to recover VOCs in soil and the surficial aquifer. In conjunction with this remedy implementation, a former concrete well ring was identified below the building floor which was a source of VOCs and petroleum hydrocarbons to the subsurface. The well ring and immediately surrounding soil were excavated from the area and disposed offsite. In connection with the DPE/SVE system, Emerson submitted an application to the Maryland Department of Water Administration for a permit to discharge treated groundwater to Stony Run through an existing outfall. The discharge permit was approved with concurrence of the local civic association in April 2004, and the DPE/SVE remedy was subsequently started. A groundwater monitoring program was also implemented to evaluate changes in VOC concentrations in the groundwater. This remedial system operated through the fall of 2013.
Following cessation of manufacturing operations in 2012, supplemental sampling activities were performed in AOC 1 to assess the effectiveness of the DPE/SVE system. The sampling results indicated the continued presence of elevated VOC concentrations in the subsurface. Based on these findings and the fact that the building was vacant, source area removal activities were conducted in late 2013 and early 2014 to further reduce VOC mass in the unsaturated soil and reduce the potential for VOCs in soil to migrate to groundwater and indoor air. The remedial activities involved the excavation of VOC-containing soils to a depth of 15 feet below the building floor. The excavated soil was segregated into stockpiles, characterized, and either transported offsite for disposal (total VOC concentrations greater than 1 milligram per kilogram [mg/kg]) or reused as backfill in the excavations (total VOC concentrations less than 1 mg/kg). Detailed information concerning the soil removal is provided in the Response Action Completion Report. MDE issued a letter, dated July 16, 2014, stating that the soil removal had been satisfactorily completed.
In AOC 2, an in-situ technology was implemented that combined pumping and air stripping to treat VOCs in groundwater (referred to as UVB). Four UVB wells were installed within the surficial aquifer in 2001 to extract, treat, and return treated groundwater to the aquifer. The UVB well system was started in December 2000, and a groundwater monitoring program was implemented to evaluate trends in VOC concentrations in the groundwater. Results of the groundwater monitoring indicated no significant reductions in VOC concentrations were occurring; therefore, supplemental investigations were conducted to further evaluate if there was another source of VOCs in AOC 2. These investigations identified a VOC source area immediately east of the building and determined that VOC impacts were present in the deeper portions of the Lower Patapsco aquifer. In 2012, an offsite monitoring well was installed immediately south of the property that confirmed VOC’s were migrating offsite to the south in the Lower Patapsco aquifer.
A source area soil removal was conducted in late 2013 in AOC 2 that involved the excavation of VOC-impacted soils to depths ranging from 18 feet to 23 feet below ground surface (BGS). The VOC impacted soil was disposed offsite and the area was backfilled with clean fill. Following the source removal, emulsified zero valent iron (EZVI) was injected into the shallow groundwater zone in AOC 2 to further reduce VOC concentrations in the surficial aquifer. The EZVI creates a treatment zone in the shallow groundwater that can reduce VOCs for an extended period of time via in-situ abiotic dechlorination. Additional information concerning the AOC 2 soil removal and EZVI injection is provided in the Response Action Completion Report.
Recent Site Activities
With the completion of the onsite soil remediation activities, low concentrations of VOCs remain in the shallow soil (less than 10 feet BGS) in the southwest portion of the former manufacturing building (AOC 1). The planned site response actions for onsite soil involve the implementation of land use and engineering controls to prevent future exposure to soil containing VOCs in this area. Institutional controls will consist of filing a land deed notice restricting the property to non-residential use, and implementing a Soil Management Plan for any intrusive activities performed within the known VOC-affected area. Engineering controls will involve the incorporation of a vapor barrier and vapor collection system in each of the newly constructed warehouse buildings to prevent VOC-containing vapors from entering the structures and designation of a portion of the south warehouse building floor and immediately adjacent concrete pavement to serve as a cap for the VOC-containing soil in AOC 1.
In late 2014, Emerson underwent an internal reorganization, pursuant to which Emerson conveyed the facility property to a newly formed subsidiary named EMERSUB 16, LLC. EMERSUB 16 continued Emerson’s remediation of the site and, to formalize this arrangement, enrolled in the VCP in March 2015. In February 2016, EMERSUB 16 completed the sale of the facility property to TC Harmans Road, LLC. Harmans Road Associates LLC, the successor in interest to TC Harmans Road, completed the redevelopment of the property for use as commercial warehouse space in February 2017.
During the property redevelopment, EMERSUB 16 initiated the construction of a remedial system to address the VOC-affected groundwater in the multi-aquifer system at the site. The selected remedy involved the extraction and treatment of impacted groundwater to prevent the offsite migration of VOCs at concentrations exceeding applicable human health criteria and remove contaminant mass from the aquifers beneath the property. The installation of the groundwater system was completed in March 2017, and the remedy has been in continuous operation since that time.
In September 2016, EMERSUB 16 and U.S. EPA entered into an Administrative Order on Consent, the principal focus of which is the implementation of the onsite groundwater extraction and treatment system, and the institution of engineering controls and land use restrictions on the former facility property to eliminate potential human exposure pathways at the warehouse facilities. The remediation is thus currently occurring pursuant to this Administrative Order on Consent and the Maryland VCP. These activities are discussed in greater detail in the sections entitled "Onsite Groundwater and Response Action" and "Offsite Groundwater and Response Action."