Wetlands Excavation and Restoration
In June 2000, a Release Notification Form (RNF) was submitted regarding the release of metals, polychlorinated biphenyls (PCBs), and polynuclear aromatic hydrocarbons (PAHs) for the wetlands area of the site. The area of the wetlands affected was located at a historical combined wastewater and stormwater outfall for the former Raytheon facility. Raytheon completed excavation of impacted wetland soil/sediment and restored the excavation area between October 2003 and February 2004. Approximately 7,955 cubic yards of sediment was excavated and transported off-Site for treatment. Verification samples were collected and analyzed demonstrating that target clean up goals were achieved. Average residual concentrations were below the target remedial concentrations, surpassing the required clean up goals.
Wetlands restoration activities included the planting of approximately 63,000 plants in February 2004 and implementation of a five-year monitoring program. Annual monitoring was conducted from 2004 through 2008. A final Annual Wetland Monitoring Report was submitted to the Massachusetts Department of Environmental Protection (DEP) on 29 January 2009. Additionally, a Request for Certificate of Compliance was submitted to the Town of Wayland Conservation Commission on 30 January 2009.
Southern Area In Situ Chemical Oxidation (ISCO)
Raytheon conducted ISCO remedial pilot studies that were successful in significantly reducing trichloroethene concentrations in groundwater in the southern portion of the Site (aka the Southern Area). In situ chemical oxidation is a process whereby a chemical, in this case permanganate, is injected into soil and groundwater to react with and break down chlorinated solvents to form harmless end products, such as carbon dioxide, water and chloride. Results from pre-remedial characterization activities and the pilot studies were used to design large-scale ISCO programs throughout the Southern Area of the Site. ISCO programs to date include;
- May to July 2004 - Approximately 21,700 gallons of a 12% sodium permanganate solution were applied to 44 injection points inside the main building. Immediately outside of the building, an additional 19,050 gallons of sodium permanganate (at the same concentration) were applied through 39 injection points;
- November 2007 – Approximately 37,000 gallons of a 0.74 to 1.5% potassium permanganate solution were applied to 15 injection points in the MW-33 Area outside of the main building;
- January 2008 - A vertical profiling program was conducted in the Main Building Area to confirm the lateral and vertical extents of chlorinated solvent impacts in the subsurface and to aid in the design of the April to May 2008 ISCO injection inside the building;
- April to May 2008 – Approximately 7,500 gallons of a 12.5% sodium permanganate solution were applied to 15 injection points within the main building and 59,000 gallons of a 1.2% potassium permanganate solution were applied to 29 injection points also in the main building. At the same time approximately 13,000 gallons (at the same concentration) of potassium permanganate were applied to 8 injection points in the MW-202 Area south of the main building.
RTN 3-13302 is currently in Remedy Operations Status (ROS) of the Massachusetts Contingency Plan process. Quarterly groundwater monitoring is ongoing and is summarized in the semi-annual ROS submittals.
In 2002, during evaluation of relatively minor impacts to groundwater (i.e., in well MW-TP-3) in the northern portion of the site (hereafter referred to as the Northern Area), additional chlorinated solvent impacts to groundwater were identified. The Waterloo Profiler was used to delineate the horizontal and vertical extents of impact and a monitoring well network was installed to evaluate groundwater quality over time.
In response to this apparent release condition and the presence of other newly identified impacts to Site groundwater, a Release Notification Form (RNF) was submitted to the Massachusetts Department of Environmental Protection (DEP) in December 2002. This RNF addressed chlorinated volatile organic compounds (CVOCs) in groundwater in the Northern Area, arsenic in groundwater beneath the wetland (i.e., the Western Area), and methyl tertiary butyl ether (MTBE) in groundwater in the Southern Area. The DEP issued a Notice of Responsibility (NOR) and Release Tracking Number (RTN) 3-22408 on 16 January 2003 for the RNF, and later issued a Tier IB Permit (W045278).
To evaluate the potential for CVOCs in groundwater in the Northern Area to adversely affect Wayland’s Baldwin Pond Wellfield, an extensive Waterloo Profiler investigation program was conducted in 2004 on Conservation Commission land between the Site and the Baldwin Pond Wellfield. Over 1,600 vertical feet were drilled at 15 locations and over 120 groundwater samples were collected and analyzed. Based on the results of this program, there is a low likelihood that groundwater impacts from the Site will impact the wellfield.
To support selection and design of an appropriate remediation technology to clean up the Northern Area CVOCs source area, a detailed source area investigation was conducted in 2005 using a Membrane Interface Probe (MIP) and Waterloo Profiler. During 2005, the Northern Area monitoring well network was expanded to further evaluate groundwater quality over time, including installation of three nested wells in the wetlands to define the downgradient extent of impact. The Phase II Comprehensive Site Assessment report submitted in December 2005 details these investigation activities.
In August 2005 a RNF was submitted for the detection of toluene above the applicable reportable concentration (RCGW-1) in a single vertical profiler sample collected from the Northern Area. This detection was identified during Phase II investigation activities for CVOCs. Toluene has not been detected above its RCGW-1 standard in groundwater samples collected from monitoring wells located in the Northern Area. The absence of additional groundwater monitoring data to support the detection of toluene above RCGW-1 leads to the conclusion that this detection is not representative of Site conditions.
After multiple investigations a Downgradient Property Status (DPS) Opinion was submitted for MTBE in Southern Area groundwater on 19 November 2007. The DPS Opinion presented a technical evaluation of the hydrogeologic conditions under which MTBE has migrated via advective groundwater flow from an upgradient source area located at a nearby retail petroleum dispensing facility. On 1 May 2008 the DEP withdrew the MTBE release from RTN 3-22408 and assigned new RTN 3-27651. Raytheon is no longer the responsible party associated with the MTBE release.
In addition to the DPS Opinion, a Class B-1 partial Response Action Outcome (RAO) was submitted for the detections of arsenic in Western Area groundwater on 19 November 2007. The RAO provided a technical evaluation of the conditions causing naturally occurring arsenic present in soil to mobilize as a result of the natural reducing conditions in the wetlands bordering the Sudbury River. As of June 2009, no response has been received from the Department regarding this RAO.
Northern Area Source Area Soil Excavation
Soil in the Northern Area of the Site was impacted primarily by CVOCs at levels above Reportable Concentrations for Category S-1 soil (RCS-1) as defined by the Massachusetts Contingency Plan. The presence of CVOCs in low hydraulic conductivity fine sand and silt soils represented the source of dissolved-phase impacts to groundwater in the Northern Area. A feasibility study was conducted to define an appropriate remedial approach to treat chlorinated solvent impacts to source area soil and groundwater within the downgradient dissolved-phase plume. The feasibility study results are presented in the Phase III – Remedial Action Plan report, submitted in December 2005. Excavation and off-Site disposal of impacted soil was selected as the preferred remedial action for abatement of the Northern Area source area and in situ bioremediation transitioning to monitored natural attenuation (MNA) was selected for treatment of the dissolved-phase plume.
The following activities were completed in 2007 to remediate the Northern Area chlorinated solvent source area soil:
Summary of Major Regulatory Submissions:
- Construction of an 80-foot diameter circular cofferdam to access impacted soils;
- Excavation and off-Site disposal of saturated source area soils (approximately 4,600 tons of soil) exceeding the MCP Method 1 GW-1/S-2 soil standards (cleanup goals) based on pre-characterization analytical data;
- Installation of an infiltration gallery for application of remedial additives as part of groundwater remediation activities;
- Re-establishment of pre-existing grades; and
- Wetland restoration and monitoring.
Northern Area Wetlands Restoration
The goal of the Northern Area wetland restoration was to construct 1,339 square feet of vegetated wetland to replace the 543 square feet disturbed by the source area excavation (a replication ratio of roughly 2.4:1). Wetland restoration and monitoring activities included regrading, resoiling, and revegetation. The 2008 Annual Wetland Monitoring Report (29 January 2009) revealed that hydrologic functions and values of this wetland have been restored since excavation activities, and the area now exhibits a diversity of native plant species, with no invasive species observed. Findings of the monitoring program indicate the project currently meets the criteria established by the OOC (90 percent survival of planted stock) and Massachusetts Wetlands Protection Act (75 percent coverage of native, wetland species). Ongoing ecological monitoring as required by the Order of Conditions will continue through the end of 2010.
Fall 2008 Lactate Injection
Bioremediation via enhanced reductive dechlorination of the downgradient dissolved-phase chlorinated solvent plume in the Northern Area commenced in August 2008. Nine injection wells were installed in two transects across the Northern Area. Following installation, approximately 1,500 gallons of 2,000 mg/L sodium lactate solution were applied to each injection well and an additional 20,000 gallons of solution were applied to the infiltration gallery. In November 2008, six additional injection wells were installed in two transects followed by the application of 1,500 gallons of sodium lactate (at the same concentration used previously) at each injection well. The next lactate injection in the Northern Area is tentatively scheduled for Summer 2009.
In February 2008 the applicable Reportable Concentration (RCGW-1) for 1,4-dioxane was reduced from 1,000 micrograms per liter (µg/L) to 3 µg/L. Given the historical use of dioxane as a solvent stabilizer, a subset of Site monitoring wells was selected for 1,4-dioxane analysis. An initial round of monitoring was conducted in May and June 2008 and is described in the Phase IV Completion Report (RTN 3-22408) and the December 2008 Remedy Operation Status (ROS) Submittal. To continue the monitoring program, samples were collected from 12 wells from 13 to 17 April 2009. Four wells located in the Northern Area dissolved-phase chlorinated solvent plume contained 1,4-dioxane at concentrations above the RCGW-1 standard. Annual monitoring of dioxane in Site groundwater is ongoing.
RTN 3-22408 Linked to RTN 3-13302
Currently, the Response Actions related to RTN 3-22408 are in ROS, which is also the case for the other active RTN (i.e., 3-13302) associated with the Site. Therefore, RTNs 3-22408 and 3-13302 will be linked to simplify the administrative requirements of managing the Site. From this point (June 2009) forward all Site activities will be tracked under RTN 3-13302.