Draft Final Proposed Plan

Transcription

1 Draft Final Proposed Plan AOC 6 Penniman AOC Naval Weapons Station Yorktown Cheatham Annex Williamsburg, Virginia May Introduction This Proposed Plan 1 presents information that describes the preferred alternative of No Further Action for five (5) non-contiguous subareas within Area of Concern (AOC) 6, (also known as Penniman AOC), located at Naval Weapons Station Yorktown Cheatham Annex (CAX), in Williamsburg, Virginia. AOC 6 comprises five subareas related to the former Penniman Shell Loading Plant (PSLP). The five subareas together with the relevant environmental media addressed at each subarea by this Proposed Plan are as follow: 1918 Drum Storage Area (DSA) subarea (soil and groundwater); Waste Slag Material (WSM) subarea (soil, groundwater, and debris); Ammonia Settling Pits (ASP) subarea (only groundwater is addressed in this Proposed Plan; soil, sediment, and surface water are not); Trinitrotoluene (TNT) Graining House Sump subarea (only groundwater is addressed in this Proposed Plan; soil, sediment, and surface water are not); and TNT Catch Box Ruins subarea (only groundwater is addressed in this Proposed Plan; soil, sediment, and surface water are not) 2 As a result of previous site investigations and solid waste removal actions performed at these subareas of AOC 6, no further remedial action is necessary to address the above-referenced media at these subareas. The remaining potentially impacted media at these subareas, as outlined below, will be documented in a separate Proposed Plan: Soil, sediment, and surface water at the ASP subarea Soil, sediment, and surface water at the TNT subareas This Proposed Plan is issued jointly by the Department of the Navy (Navy), the lead agency for environmental restoration activities at CAX, and the U.S. Environmental Protection Agency (USEPA), the lead Mark Your Calendar for the Public Comment Period Public Comment Period June 2 to July 19, 2018 Submit Written Comments The Navy will accept written comments on this Proposed Plan during the public comment period. To submit comments or obtain further information, please refer to the names and contact information included at the end of Section 7. A blank sheet has been added at the end of the document for written comments; however, the commenter is not limited to the space provided. Attend the Public Meeting June 7, 2018 at 3:00 p.m. Yorktown Library 8500 George Washington Memorial Highway, Yorktown, VA The Navy will hold a public meeting to explain the Proposed Plan. Oral and written comments will be accepted at this meeting, as well. Location of Administrative Record File: Naval Facilities Command (NAVFAC) Atlantic 6506 Hampton Boulevard Norfolk, Virginia Phone: Or at the CAX Public website: 1 A glossary of key terms identified in bold print the first time they appear in this document is provided at the end of this Proposed Plan. 2 The Trinitrotoluene (TNT) Graining House Sump subarea and the TNT Catch Box Ruins subarea will hereafter collectively be referred to as the TNT subareas. 1 NG VBO

2 regulatory agency. The Navy and USEPA, in consultation with the Virginia Department of Environmental Quality (VDEQ), the support regulatory agency, will select the final remedy for AOC 6. This Proposed Plan will be available for public review and comment at the Yorktown Library (see the Attend the Public Meeting section in the right hand panel on the first page for location information) during a 45-day public comment period that includes a public meeting and fulfills participation responsibilities required under Sections 113(k)(2)(B), 117(a), 120(f), and 121(f)(1)(G) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), as amended, and Sections (f)(2) and (f)(3) of the National Oil and Hazardous Substances Pollution Contingency Plan. The Navy and USEPA, in consultation with VDEQ, will make the final decision for these specific media associated with the various subareas within AOC 6 after reviewing and considering all information submitted during the 45-day public comment period and may modify this Proposed Plan based on new information or public comments received. Information documenting all environmental investigations at AOC 6 are available to the public in the Administrative Record file for CAX. Details regarding the dates of the public comment period, the date and time of the public meeting, and the location of the Administrative Record are included in the righthand panel on the first page of this Proposed Plan that begins with Mark Your Calendar for the Public Comment Period. 2. Site Background CAX CAX is located in Williamsburg, Virginia, on the York- James Peninsula (Figure 1, inset). Portions of CAX were formerly the site of the PSLP, a large powder and shell loading facility operated by E.I. DuPont de Nemours & Company between 1916 and 1918, during World War I. Between 1918 and 1925, this facility was demolished and the property reverted to farmland until the Navy established CAX in June 1943 as a satellite unit of the Navy Supply Depot to provide bulk storage facilities. Today the mission of CAX is supplying Atlantic Fleet ships and providing recreational opportunities to military and civilian personnel. In January 2001, CAX was placed on the National Priorities List, which required all subsequent activities for Navy environmental restoration sites be conducted in accordance with CERCLA. 2 AOC 6 Five non-contiguous subareas comprise AOC 6, each less than 1 acre in size, and all related to the former PSLP. The PSLP operated as a TNT manufacturing plant beginning in approximately 1916, and subsequently added the loading of artillery shells for the war effort in In the CAX Federal Facility Agreement, the Navy, USEPA, and VDEQ agreed to investigate five subareas related to the former PSLP (1918 Drum Storage Area, Waste Slag Material, Ammonia Settling Pits, TNT Graining House Sump, and TNT Catch Box Ruins) (USEPA et al., 2005). These subareas comprise AOC 6, and are located within the vicinity of the former shell loading area, south of Sanda Avenue (formerly DuPont s G plant) on Navy property (Weston, 1999) (Figure 1) Drum Storage Area (DSA) The DSA subarea was identified by the USEPA from a 1918 overhead photograph. This subarea was once used for the storage of wooden barrels and/or drums of unknown content when the shell loading facility was active (ATSDR, 2004). The DSA subarea is currently a developed area, located south of Antrim Road, consisting mostly of open and maintained grassy areas and a parking lot (Figure 2). Waste Slag Material (WSM) The WSM subarea was originally identified during a Site Inspection of the former PSLP in 1999, and consisted of a pile of metallic slag material of unknown origin. It has been speculated that the waste slag may be the result of former railroad activities and may have been broken out of steam locomotive boilers and dumped along the tracks during the PSLP era (Weston, 1999). The waste slag pile was irregular in shape, covered an area of approximately 600 square feet, and measured up to 1.5 feet in height. The slag was embedded into the ground surface up to a few inches at some locations within the pile and readily discernible in texture and color from the adjacent soil. The waste slag pile and surrounding soil and debris (Figure 3) were removed as part of a solid waste removal action in October 2015 and disposed of offsite. The former pile location was regraded and seeded, and is currently a grassy area. Ammonia Settling Pits (ASP) While the specific history of the AOC 6 ASP subarea is unknown, it is assumed that wastewater from an ammonia finishing building was discharged through three ASPs into the tidal tributary of King Creek that

3 Figure 1 Site Map of AOC 6 Subareas and CAX 3

4 Figure 2 Drum Storage Area Subarea Sampling Locations 4

5 Figure 3 Waste Slag Material Subarea Sample Locations 5

6 existed before Penniman Lake was created. Currently, this subarea is wooded and situated near the banks of Penniman Lake and consists of what may be remnants of earthen ASPs that were part of the PSLP (Figure 4). TNT Graining House Sump and Catch Box Ruins (TNT) The specific history of the AOC 6 TNT Subareas is unknown. The TNT Graining House Sump subarea includes the concrete footprint of the former TNT Graining House, as well as the concrete-lined, open top pit believed to be the sump pit for the former TNT Graining House (Figure 4). The TNT Catch Box Ruins subarea consists of an earthen, brick-lined depression located immediately east and adjacent to the TNT Graining House (Figure 4). It is assumed that the TNT Catch Box was used to separate TNT particles from wastewater. Potential historical leakage or discharge from the former TNT Graining House Sump and/or TNT Catch Box are the sole known or suspected sources of contamination at the AOC 6 TNT subareas. Currently, the TNT subareas are wooded and situated near the banks of Penniman Lake. 2.1 Previous Investigations and Actions The extent of contamination at AOC 6 has been characterized as part of several investigations conducted since The investigations conducted for various media at AOC 6 are listed in Table 1 and summarized in the subsections below Site Inspection Narrative Report (Weston, 1999) In January 1999, soil, sediment, and/or surface water samples were collected from the 1918 DSA, the ASP, and the TNT subareas to assess potential sources of contamination associated with the PSLP and to support hazard ranking system evaluations. In addition, a sample of the metallic slag material was collected from the WSM. All samples were analyzed for volatile organic compounds (VOCs), semivolatile organic compounds, pesticides, polychlorinated biphenyls (PCBs), nitramines/nitroaromatics, and inorganic constituents. Analytical results indicated the presence in soil at concentrations exceeding the April 1999 residential soil risk-based concentrations of arsenic within the 1918 DSA, the WSM, the ASP, and the two TNT subareas; lead within the WSM and the two TNT subareas; and nitramines/ nitroaromatics within the TNT subareas. Constituent concentrations within the surface water and sediment samples collected in the vicinity of the ASP and TNT subareas did not exceed background sample concentrations. Site-specific risk assessments were recommended to evaluate the potential threat posed to human health by contaminants present in these subareas. 2.3 Site Inspection Report, AOCs 1, 2, 6, 7 and 8 (CH2M, 2012) To determine whether a CERCLA-regulated release had occurred and whether any release warranted further action at the 1918 DSA, ASP, and TNT subareas, soil and groundwater samples (and in the case of the ASP and TNT subareas, surface water and sediment samples) were collected (Figures 2, 3, and 4) and the results compared to human health and ecological screening criteria. Based on this comparison, the following recommendations were made: No further action for all media (soil and groundwater) at the DSA subarea. Conduct an expanded Site Inspection for groundwater at the ASP subarea. Conduct a Remedial Investigation and feasibility study for soil and groundwater at the TNT subareas. At the time of the SI Report, the Navy, USEPA, and VDEQ agreed further evaluation of explosives in sediment and surface water in the vicinity of the ASP and TNT subareas would be addressed as part of ongoing investigations at AOC 9 (Penniman Lake); however, it was later agreed that these media be evaluated in an addendum to the AOC 6 RIs (see Sections 2.6 and 2.8). 2.4 No Further Action Technical Memorandum (TM) for Soil and Groundwater at the AOC 6 WSM Subarea (CH2M, 2013a) The WSM subarea was not included in the 2012 Site Inspection, because the Navy generally does not consider waste associated with former railroad activities to be CERCLA-regulated. However, since this slag pile was included in the definition of AOC 6 within the CAX Federal Facility Agreement, surface and subsurface soil samples were collected to determine if metals may have leached from the waste slag pile to the surrounding soil (Figure 3). The results were compared to human health and ecological screening criteria. Based on the results of the risk screening, the Navy, USEPA, and VDEQ agreed that the soil at the Waste Slag Material subarea posed no potentially unacceptable risks to human or ecological receptors and posed no risk of leaching into groundwater (there is no sediment or surface water associated with this subarea). However, the Navy agreed to remove the waste slag pile at AOC 6 to l three ASPs into the tidal tributary of King Creek that prevent any potential for future contamination of the soil and groundwater. 6

7 Figure 4 ASP and TNT Subarea Sampling Locations 7

8 Table 1 - Documents Summarizing Previous Studies at AOC 6 Document Title/Milestone Author/Date AR Document Number Site Inspection Narrative Report Weston, C Federal Facility Agreement (CAX) USEPA et al., Site Inspection Report, AOCs 1, 2, 6, 7 and 8 CH2M, No Further Action Technical Memorandum for Soil and Groundwater at the Waste Slag Material Subarea of AOC 6 Consensus Letter for Soil and Groundwater at the Area of Concern Drum Storage Area Subarea CH2M, 2013a CH2M, 2013b Remedial Investigation Report, AOC 6 TNT Subareas CH2M, No Further Action Technical Memorandum for the Waste Slag Material Subarea of AOC 6 CH2M, 2016a Remedial Investigation Report, AOC 6 Ammonia Settling Pits Subarea CH2M, 2016b Consensus Letter for Soil and Groundwater at the Area of Concern Drum Storage Area Subarea (CH2M, 2013b) Based on the recommendations presented in the 2012 Site Inspection Report, a Technical Memorandum was prepared to support no further action at the DSA subarea. Baseline human health and ecological risk assessments were conducted using soil and groundwater data collected during the 2012 Site Inspection. With the exception of thallium in groundwater, no potentially unacceptable human health or ecological risks were identified for soil and groundwater at the DSA subarea (there is no sediment or surface water associated with this subarea). While thallium was identified as potentially posing an unacceptable hazard to future residents in groundwater, the Navy, USEPA, and VDEQ agreed that no further action was required because the maximum detected thallium concentration (0.078 micrograms per liter [µg/l]) did not exceed the USEPA maximum contaminant level (2 µg/l). 2.6 Remedial Investigation Report, AOC 6 TNT Subareas (CH2M, 2015) Based on the recommendations presented in the 2012 Site Inspection Report, a Remedial Investigation was conducted at the TNT subareas to determine the extent of soil and groundwater contamination and to assess the potential risks posed by exposure to contamination for human and ecological receptors (Figure 4). TNT subarea surface water and sediment were not evaluated in the Remedial Investigation; the Navy, USEPA, and VDEQ agreed to evaluate explosives contamination within Penniman Lake separately; therefore, sediment and surface water are 8 currently being evaluated under a Remedial Investigation Addendum. Potentially unacceptable human health risk was identified due to exposure to arsenic and iron in groundwater. No potentially unacceptable risk to aquatic ecological receptors was identified. While arsenic and iron were identified as constituents of concern in groundwater, as described in Section 5.4, no further action is necessary, as the Navy, USEPA, and VDEQ agree that the detected concentrations are attributable to naturally-occurring background conditions and not from historical leakage or discharge from the former TNT subareas. Potentially unacceptable risk to human health and the environment was identified due to exposure to soil. Since the unacceptable risks are likely attributable to historical leakage or discharge from the from the former TNT subareas, a Feasibility Study to evaluate remedial alternatives to address soil was recommended. A Feasibility Study will be completed to evaluate remedial alternatives for any contaminated media posing unacceptable risks (soil, sediment, and/or surface water) following the Remedial Investigation Addendum; therefore, soil, sediment and surface water data associated with the TNT subareas is not presented in this Proposed Plan. However, since no further action is necessary for groundwater, groundwater data associated with the TNT subareas is included in this Proposed Plan. 2.7 No Further Action Technical Memorandum for the Waste Slag Material Subarea of AOC 6 (CH2M, 2016a) As documented in the No Further Action Technical Memorandum for Soil and Groundwater at the WSM subarea of AOC 6 (CH2M, 2013a), soil at the WSM

9 subarea posed no potentially unacceptable risks to human or ecological receptors and posed no risk of leaching into groundwater. However, to eliminate any potential for future contamination of the soil and groundwater, the Navy agreed to remove the waste slag pile at the WSM subarea as part of a solid waste removal action. A total of 39 tons of non-hazardous soil and slag/debris were excavated, transported and disposed of offsite. The excavated area at the site was backfilled to original grade using approved, clean common fill and topsoil materials. Following the removal of the waste slag pile at the WSM subarea, the Navy, USEPA, and VDEQ agreed that the potential for future impacts to site media had been eliminated and that no further action for the WSM subarea was warranted and this was documented in the No Further Action Technical Memorandum (CH2M, 2016a). 2.8 Remedial Investigation Report, AOC 6 Ammonia Settling Pits Subarea (CH2M, 2016b) While the recommendations presented in the 2012 Site Inspection Report were to conduct an expanded site inspection for groundwater at the ASP subarea, the Navy, USEPA, and VDEQ agreed that a Remedial Investigation with additional soil sampling was more appropriate. As such, a Remedial Investigation was conducted at the ASP subarea to determine the extent of soil and groundwater contamination and to assess the potential risks posed by exposure to contamination for human and ecological receptors (Figure 4). As with the TNT subareas, ASP subarea surface water and sediment were not evaluated in the Remedial Investigation; the Navy, USEPA, and VDEQ agreed to evaluate explosives contamination within Penniman Lake separately; therefore; sediment and surface water are currently being evaluated under a Remedial Investigation Addendum. Potentially unacceptable human health risk was identified due to exposure to arsenic, chromium, cobalt, iron, and manganese in groundwater. No potentially unacceptable risk to aquatic ecological receptors was identified. While arsenic, chromium, cobalt, iron, and manganese were identified as constituents of concern in groundwater, as described in Section 5.3, no further action is required since the Navy, USEPA, and VDEQ agreed that the detected concentrations are attributable to naturally-occurring background conditions and not from historical leakage or discharges from the ASP subarea. 9 Potentially unacceptable risk to human health and the environment was identified due to exposure to soil. Since the unacceptable risks are likely attributable to historical leakage or discharge from the from the former ASP subarea, a Feasibility Study to evaluate remedial alternatives to address soil was recommended. A Feasibility Study will be completed to evaluate remedial alternatives for any contaminated media posing unacceptable risks (soil, sediment, and/or surface water) following the Remedial Investigation Addendum; therefore, soil, sediment and surface water data associated with the ASP subarea is not presented in this Proposed Plan. However, since no further action is necessary for groundwater, groundwater data associated with the ASP subarea is included in this Proposed Plan. 3. Site Characteristics The DSA is generally topographically flat and consists of open and maintained grassy areas and a parking lot (Figure 2), while the WSM, ASP, and TNT subareas of AOC 6 are generally topographically flat and are wooded and moderately-vegetated with trees and shrubs (Figures 3 and 4). All subareas of AOC 6 are located within the confines of CAX, where public access is restricted; however, Navy and Department of Defense personnel do have potential access. There are no current plans for any changes to the land use of the site. In general, soil at AOC 6 is predominantly brown silt and olive brown clay, underlain by yellow sand. The shallow aquifer underlying the ASP and two TNT, subareas is the unconfined Columbia aquifer. The primary groundwater flow direction at the two TNT and ASP subareas is southward, away from Penniman Lake and toward King Creek; under these conditions, Penniman Lake is recharging the Columbia aquifer in the vicinity of these subareas. However, this may be a transient flow pattern, such that there may be times when the primary flow direction is reversed and groundwater discharges into Penniman Lake (e.g., in times of drought when the lake level is lower). The shallow aquifer underlying the DSA and WSM subareas is the Yorktown-Eastover. The primary groundwater flow at the DSA is southeast toward Penniman Lake while at the WSM subarea, groundwater is anticipated to flow southeast toward King Creek. There is no current or expected future use of groundwater at AOC 6. Drinking water is supplied to CAX and the surrounding area by the City of Newport News Waterworks. However, the Commonwealth of Virginia regards all groundwater as a potential drinking water source.

10 3.1 Principal Threat Wastes Principal threat wastes are source materials considered to be highly toxic or highly mobile that generally cannot be reliably contained or would present a significant risk to human health or the environment should complete exposure pathways exist. There are no principal threat wastes at any of the AOC 6 subareas addressed in this Proposed Plan. 4. Scope and Role of Response Action CAX was placed on the National Priorities List in January Currently, five sites at CAX have a Final Record of Decision (ROD) or Decision Document describing and documenting the selected remedial alternative: Site 1 (OU 1) No Further Action (all media) Site 11 (OU 5) No Further Action (all media) Site 7 (OU 3) No Further Action (soil, debris, sediment, surface water) AOC 2 (OU 10) No Further Action (all media) AOC 7 (OU 12) No Further Action (all media) In addition to the AOC 6 subareas and specific environmental media addressed in this Proposed Plan, seven sites are being investigated under CERCLA at CAX: Site 4, Site 7 (groundwater), Site 9, AOC 1, AOC 6 (soil, sediment, and surface water at the ASP and TNT subareas), AOC 8, and AOC 9. A summary of how the Navy, in partnership with USEPA and VDEQ, is addressing all CERCLA sites at CAX is provided in the Site Management Plan, which is updated annually and available in the Administrative record file and at the Yorktown Library. The Preferred Alternative presented in this Proposed Plan is No Further Action for the following AOC 6 subareas and associated environmental media: soil and groundwater at the 1918 DSA subarea, soil, groundwater, and debris at the WSM subarea, groundwater at the ASP subarea; and groundwater at the TNT subareas. The remaining AOC 6 media (soil, sediment, and surface water at the ASP and two TNT subareas) are being addressed separately and will be presented in a future Proposed Plan. 5. Summary of Site Risks Results of the Human Health Risk Assessment (HHRA) and the Ecological Risk Assessment (ERA) conducted for AOC 6 were presented in the following reports: 1918 Drum Storage Area Technical Memorandum (CH2M, 2013b) Waste Slag Material Subarea Technical Memorandum (CH2M, 2013a) Ammonia Settling Pits Remedial Investigation (CH2M, 2016b) TNT subareas Remedial Investigation (CH2M, 2015) The conclusions and recommendations from these reports are summarized in the subsections below. Risk management decisions relevant to this Proposed Plan are also discussed. For general information regarding how human health and ecological risk evaluations are conducted, see the text boxes What is Ecological Risk and How is it Calculated? and What is Human Health Risk and How is it Calculated? Drum Storage Area Baseline human health and ecological risk assessments were conducted using soil and groundwater data collected during the 2012 Site Inspection (CH2M, 2013b). With the exception of thallium in groundwater, no potentially unacceptable human health or ecological risks were identified for soil and groundwater at the DSA subarea (there is no sediment or surface water associated with this subarea). While thallium in groundwater was identified as potentially posing an unacceptable hazard to future residents, the Navy, USEPA, and VDEQ agreed that no further action was required because the maximum detected thallium concentration (0.078 µg/l) did not exceed the maximum contaminant level (2 µg/l). 5.2 Waste Slag Material Subarea Based on the results of the risk screening (through Step 1 of the human health and ecological risk evaluations) (CH2M, 2013a), soil at the WSM subarea poses no potentially unacceptable risks to human or ecological receptors and poses no risk of leaching into groundwater. In addition, in order to eliminate all potential for future contamination of the soil and groundwater, the waste slag pile at the WSM subarea was removed in October 2015 as part of a solid waste removal action. 5.3 Ammonia Settling Pits Based on the results of the Human Health and the Ecological Risk Assessment (CH2M, 2016b), potential risk to hypothetical future residents exists due to exposure to arsenic, chromium, cobalt, iron, and 10

11 What is Human Health Risk and How is it Calculated? An HHRA, which estimates the likelihood of health problems occurring if no cleanup action was taken, consists of the following four-step process: Step 1: Analyze Contamination Step 2: Estimate Exposure Step 3: Assess Potential Health Dangers Step 4: Characterize Site Risk In Step 1, comparisons of the concentrations of site chemicals to scientific studies on the effects those chemicals have on people help identify which chemicals pose the greatest threat to human health. In Step 2, the Navy considers different ways people might be exposed to chemicals, the concentrations, how often, and how long they may be exposed in order to assess a reasonable maximum exposure scenario that portrays the highest level of human exposure that could reasonably be expected to occur. In Step 3, the Navy uses the information from Step 2, combined with toxicity information, to assess potential health risks. The Navy considers two types of risk: cancer risk and non-cancer hazard. The likelihood of any type of cancer resulting from a contaminated site is generally expressed as a probability: 1 in 10,000 chance (for every 10,000 people that could be exposed, one extra case of cancer may occur as a result of exposure). For non-cancer health effects, the Navy calculates a hazard index which is the ratio between the reasonable maximum exposure and the reference dose (the dosage at which no adverse health effects are expected). A threshold level (hazard index less than 1) exists below which non-cancer health effects are no longer predicted. In Step 4, the Navy calculates whether site risks are high enough to potentially cause health problems for people at or near the site. The results of the three previous steps are combined, evaluated, and summarized. The Navy adds up the potential risks from the individual contaminants and exposure pathways and calculates a total site risk. What is Ecological Risk and How is it Calculated? An ERA evaluates the potential risks to plants, animals, habitats, and communities, and is conducted using a step-wise process (as outlined in Navy and USEPA ERA policy and/or guidance) that includes decision points where agreement among stakeholders is reached to determine if the process should continue or terminate. The process continues until a final decision has been reached (i.e., remedial action if unacceptable risks are identified, or NFA if risks are acceptable). The process can also be iterative if data needs are identified at any step; the needed data are collected and the process starts again at the point appropriate to the type of data collected. An ERA has three principal components: 1. Problem Formulation, which establishes the goals, scope, and focus of the ERA and includes: Compiling and reviewing existing information on the habitats, plants, and animals that are present on or near the site. Identifying and evaluating area(s) where site-related chemicals may be found (source areas) and at what concentrations. Evaluating potential movement (transport) of chemicals in the environment. Identifying possible exposure media (soil, air, water, sediment). Evaluating if/how the plants and animals may be exposed (exposure pathways). Evaluating routes of exposure (for example, ingestion). Identifying specific receptors (plants and animals) that could be exposed. Specifying how the risk will be measured (assessment and measurement endpoints) for all complete exposure pathways. 2. Risk Analysis, which includes: manganese in groundwater. No other human health or ecological risks from exposure to groundwater were identified. However, for each of these constituents, the Navy, USEPA, and VDEQ agreed that the detected concentrations are attributable to naturally-occurring background conditions and not from historical leakage or discharges from the ASP subarea. For arsenic, the detected groundwater concentrations were all below the site-specific background concentration (Table 2). While concentrations of chromium, cobalt, iron, and manganese in groundwater exceeded their respective site-specific background concentration (where applicable), all detections of these metals in the overlying soil were below basewide background levels, indicating their concentrations in groundwater are not attributable to a site-related release and are likely the result of the natural reductive dissolution process. Exposure Estimate - An estimate of exposure concentrations. This includes direct exposures to lower trophic level receptors (organisms low on the food chain, such as plants and insects) and upper trophic level receptors (organisms higher on the food chain, such as birds and mammals), and indirect exposures (exposures via the food chain) for upper trophic level receptors. Effects Assessment - The concentrations of chemicals at which an adverse effect may occur are determined. 3. Risk Calculation or Characterization: The first two steps are used to estimate potential risk to plants and/or animals by comparing the exposure estimates with the effects thresholds. Also included is an evaluation of the uncertainties (potential degree of error) that are associated with the predicted risk estimate and their effects on ERA conclusions. 11

12 Table 2 Comparison of ASP subarea groundwater and soil metals concentrations to background concentrations Groundwater Soil Metals (Total) Maximum Detected Concentration (μg/l) Site-Specific Background Level (μg/l) Maximum Detected Concentration (µg/kg) 95 percent UTL Background Level (µg/kg) Arsenic ,000 5,540 Chromium ,000 33,700 Cobalt ,700 5,180 Iron 56,000 30,000 25,000,000 32,000,000 Manganese 1, , ,000 UTL = Upper Tolerance Limit 5.4 TNT Subareas Based on the results of the Human Health and the Ecological Risk Assessment (CH2M, 2015), potential risk to hypothetical future residents exists due to exposure to arsenic and iron in groundwater. However, elevated arsenic and iron concentrations have been attributed to naturally occurring background conditions reflective of the natural reductive dissolution process rather than to a CERCLA release based on the following: Monitoring wells located upgradient and sidegradient of the suspected release areas, as well as in areas with overlying soil concentrations below the background upper tolerance limits, had arsenic and iron concentrations higher than monitoring wells downgradient of the release areas. Therefore, arsenic and iron concentrations in groundwater from these reference wells are considered to be representative of the range of background concentrations present in this area of CAX. Both arsenic and iron concentrations in monitoring wells located adjacent to or downgradient of the suspected release areas were all below the ranges of representative background values. 6. Preferred Alternative Based on the findings of the DSA Technical Memorandum (CH2M, 2013b), the WSM Subarea Technical Memorandum (CH2M, 2016a), the ASP Remedial Investigation (CH2M, 2016b), and the TNT Subareas Remedial Investigation (CH2M, 2015), there are no unacceptable site-related risks to human health or the environment related to groundwater and soil for the DSA subarea, groundwater, soil, and debris for the WSM subarea, and groundwater for the ASP and two TNT subareas. Furthermore, the removal of debris at the WSM subarea, as well as surrounding soil, has eliminated any potential for a future source of exposure to contamination. Because there are no unacceptable site-related risks in these affected media at these AOC 6 subareas, no alternatives other than No Further Action were evaluated. Under this alternative, no further actions would be performed for groundwater and soil at the DSA subarea; for groundwater, soil, and debris at the WSM subarea; and for groundwater at the ASP and the two TNT subareas, and no restrictions on land use or exposure would be implemented as it pertains to these media. The Navy will take into consideration any public comments received with regard to the preferred alternative prior to remedy selection. Unacceptable risk to human health and the environment was identified due to exposure to soil at the ASP and TNT subareas and potential human health and ecological risk due to exposure to sediment and surface water at the ASP and TNT subareas are currently being evaluated. Therefore, this Proposed Plan does not present a preferred alternative for soil, sediment and surface water at these subareas. Following the surface water and sediment evaluation, a Feasibility Study will be prepared to evaluate potential remedial alternatives to address soil, as well as surface water and sediment as necessary. The preferred remedial alternative for these media will be presented in a separate Proposed Plan. 7. Community Participation The Navy and USEPA, in consultation with VDEQ, will make the final decision on the remedial alternative for these AOC 6 subarea media after reviewing and 12 NG VBO

13 considering all information and comments submitted during the 45-day public comment period. The public comment period for this Proposed Plan will extend from June 2 to July 19, 2018 and a public meeting to discuss the Proposed Plan will be held on June 7, 2018, beginning at 3:00 p.m. Details regarding the public comment period and public meeting are included in the right-hand panel in Section 1 entitled, Mark Your Calendar for the Public Comment Period. The Navy will summarize and respond to all comments submitted during the public comment period in a Responsiveness Summary that will be included in the final decision document, the Record of Decision, which will be prepared subsequent to the close of the comment period on this Proposed Plan. This Proposed Plan and the Record of Decision will become part of the Administrative Record file for CAX. Public participation is encouraged since the preferred alternative presented in this Proposed Plan may be modified or another alternative selected based on new information and/or public comments received. The public is encouraged to gain a more comprehensive understanding of AOC 6 and the Navy s Environmental Restoration Program by attending this and other public meetings advertised in the Daily Press and Virginia Gazette newspapers, and by accessing information included in the CAX public website ( which includes access to the CAX AR file. Minutes of all public meetings will be included in the Administrative Record file. 8. References ATSDR, Public Health Assessment, Naval Weapons Station Yorktown, Cheatham Annex, Williamsburg, York County, VA. September. CH2M, Final Site Inspection Report, Areas of Concern 1, 2, 6, 7, and 8, Naval Weapons Station Yorktown Cheatham Annex, Williamsburg, Virginia. May. CH2M, 2013a. Final No Action Technical Memorandum for Soil and Groundwater at the Waste Slag Subarea of AOC 6, Naval Weapons Station Yorktown Cheatham Annex, Williamsburg, Virginia. August. CH2M, 2013b. Final Consensus Letter for Soil and Groundwater at the Area of Concern Drum Storage Area Subarea, Naval Weapons Station Yorktown Cheatham Annex, Williamsburg, Virginia. August. CH2M, Final AOC 6 TNT Subareas, Remedial Investigation Report, Naval Weapons Station Yorktown Cheatham Annex, Williamsburg, Virginia. August. CH2M, 2016a. Final No Further Action Technical Memorandum for the Waste Slag Material Subarea of AOC 6, Naval Weapons Station Yorktown Cheatham Annex, Williamsburg, Virginia. April. CH2M, 2016b. Final AOC 6 Ammonia Settling Pits Subarea, Remedial Investigation Report, Naval Weapons Station Yorktown Cheatham Annex, Williamsburg, Virginia. April. USEPA, Commonwealth of Virginia, and United States Department of the Navy Federal Facility Agreement for Naval Weapons Station Yorktown Cheatham Annex. March. Weston, Final Site Inspection Narrative Report Penniman Shell Loading Plant, Williamsburg, Virginia. August. During the comment period, interested parties may submit written comments to one or more of the following addresses: Ms. Cecilia Landin NAVFAC Mid-Atlantic 9324 Virginia Avenue Bldg. N-26, Room 3300 Norfolk, VA Phone: (757) cecilai.landin@navy.mil 9. Glossary Mr. Brian Poe USEPA (Region III) 1650 Arch Street Philadelphia, PA Phone: (215) poe.brian@epa.gov Mr. Wade Smith Virginia Dept. of Environmental Quality 1111 East Main Street, 15 th Floor Richmond, VA Phone: (804) wade.smith@deq.virginia.gov Administrative Record (AR): A compilation of documents relied upon to select a remedial response. The AR is available to the public and is in the ERP Information Repository. 13

14 Area of Concern (AOC): An area of suspected or known contamination that warrants further study to determine if CERCLA-related risk to human health or the environment is present. Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA): A federal law, commonly referred to as the Superfund Program, which was passed in 1980 and subsequently amended. CERCLA provides for cleanup and emergency response in connection with existing inactive hazardous waste disposal sites that endanger public health and safety or the environment. Ecological Risk Assessment (ERA): An organized process used to describe and estimate the likelihood of adverse impacts on the environment from exposure to chemicals in the environment. Environmental Restoration Program: The Navy program charged with implementing environmental cleanups under CERCLA at Navy installations. The Navy, as lead agency, acts in partnership with USEPA and VDEQ to address environmental investigations at Navy facilities through the ERP. Federal Facility Agreement: An agreement between the Navy, USEPA, and VDEQ that ensures environmental impacts associated with the past and present activities at a site (e.g., CAX) are thoroughly investigated and the appropriate response action(s) is(are) taken under CERCLA as necessary to protect the public health, welfare, and the environment and that establishes a procedural framework and schedule for developing, implementing, and monitoring appropriate response actions at the site. Groundwater: Subsurface water that occurs in soil and geologic formations that are fully saturated. Human Health Risk Assessment (HHRA): An organized process used to describe and estimate the likelihood of adverse impacts on human health from exposure to chemicals in the environment. National Oil and Hazardous Substances Pollution Contingency Plan: The regulations that provide the organizational structure and procedures needed to prepare for and respond to discharges of oil and releases of hazardous substances, pollutants, and contaminants. National Priorities List: A list, developed by USEPA, of uncontrolled hazardous substance release sites in the United States that are considered priorities for long-term remedial evaluation and response. Polychlorinated biphenyls (PCBs): A class of organic compounds with 1 to 10 chlorine atoms 14 attached to a biphenyl group. PCBs were widely used in transformers and capacitors and as coolants. Production of PCBs was banned by the United States Congress in 1976 due to its known toxicity. Proposed Plan: A document that presents information and requests public input regarding a proposed cleanup alternative. Public Comment Period: The time allowed for the members of an affected community to express views and concerns regarding an action proposed to be taken by the Navy and USEPA, such as a rulemaking, permit, or Superfund alternative selection. Record of Decision (ROD): A legal document that describes the cleanup action or alternative selected for a site, the basis for choosing that alternative, and public comment on the selected alternative. Remedial Investigation (RI): Extensive technical study conducted to characterize the nature and extent of contamination present at a site. Sediment: Matter that settles to the bottom of a liquid. Semivolatile organic compounds: Manufactured chemicals that do not evaporate as easily as VOCs and are typically used in manufacturing materials such as adhesives and preservatives. Site Inspection (SI): Initial study conducted to characterize the nature and extent of risks posed by a site. Site Management Plan: Annual document generated in accordance with the Federal Facilities Agreement, which provides a 5-year plan for CERCLA Installation Restoration activities. Soil: The unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants. Surface Water: A body of water on the surface of the earth. U.S. Environmental Protection Agency (USEPA): The federal agency responsible for administration and enforcement of CERCLA (and other environmental statutes and regulations), and with final approval authority for the selected alternative. Virginia Department of Environmental Quality (VDEQ): The Commonwealth agency responsible for administration and enforcement of environmental regulations. Volatile organic compounds (VOCs): Compounds that easily vaporize and have low water solubility. Many VOCs are manufactured chemicals such as those associated with paint, solvents, and petroleum.

15 Please print or type your comments here 15

16 Mark Your Calendar for the Public Comment Period Public Comment Period June 2 to July 19, 2018 Submit Written Comments The Navy will accept written comments on this Proposed Plan during the public comment period. To submit comments or obtain further information, please refer to the names and contact information included at the end of Section 7. A blank sheet has been added at the end of the document to be used for written comments; however, the commenter is not limited to the space provided. Attend the Public Meeting June 7, 2018 at 3:00 p.m. Yorktown Library 8500 George Washington Memorial Highway Yorktown, VA The Navy will hold a public meeting to explain the Proposed Plan. Oral and written comments will be accepted at this meeting, as well Fold Here Place stamp here NAVFAC Mid-Atlantic Attention: Ms. Cecilia Landin 9324 Virginia Avenue Building N-26, Room 3300 Norfolk, VA