Staff Report for Former ANG Coos Head Recommendation for Partial No Further Action for Groundwater at AOC C

Transcription

1 Staff Report for Former ANG Coos Head Recommendation for Partial No Further Action for Groundwater at AOC C Project Name: Former ANG Coos Head AOC C Groundwater Project Address: Coos Head Road, Coos Bay, Oregon (See Figure 1) Location: Lat , DEQ Project Manager: Norman Read Project Manager Approval Toxicologist Approval Norman Read Susan Turnblom Date: March 8, 2017 ECSI Number: 3833 Responsible Party: US Air National Guard 1. Background and Scope of Environmental Work and NFA Determination DEQ recommends that the former Air National Guard (ANG) Coos Head Area of Concern (AOC) C Groundwater receive No Further Action (NFA) determination. The groundwater at AOC C and for the entire site has now been determined to be safe for any use and therefore an NFA is being issued. All other contaminated areas of the site have already been successfully addressed, including AOC B (Wash Rack Area), AOC C (Outfall 1), AOC C (Outfall 2), AOC C (Building 13 soils), and AOC K (Fire Training Area), The primary soil objectives for those areas of concern were: A. AOC B - removal and off-site disposal of benzo (a) pyrene-contaminated soil exceeding the mg/kg remedial action goal from the former wash rack drain area. B. AOC C (Outfall 1) - excavate and dispose offsite Outfall 1 soils contaminated with arsenic, benzo (a) pyrene, and heptochlorodibenzo-p dioxin (HpCDD) which exceeded the remedial goals of 6 mg/kg, mg/kg, and 4.4 X 10-6, respectively. C. AOC C (Outfall 2) - excavate and dispose offsite Outfall 2 soils contaminated with arsenic and benzo (a) pyrene which exceeded the remedial goals of 6 mg/kg and mg/kg respectively. Page 1 of 33

2 D. AOC C (Building 13 Soils) - demolish Building 13, excavate the underlying contaminated soil, and dispose the volatile organic compounds (VOC) - contaminated soils off-site. E. The AOC K (Fire Training Area) excavate and dispose off-site the benzo (a) pyrenecontaminated soils which exceeded the mg/kg remedial action goal. These areas of concern have already been issued an NFA. The completion of the remediation work at AOC C Groundwater is addressed in this staff report. The NFA for groundwater concludes the remediation work for the entire Coos Head property owned by the Confederated Tribes of the Coos, Lower Umpqua, and Siuslaw Indians (Confederated Tribes). 2. Documentation used as basis for NFA decision: The basis for the NFA recommended in this Staff Report is the December 2016 No Further Response Action Planned Decision Document, Groundwater at AOC C Building 13/Multiple Former Underground Storage Tanks Former 104th Air Control Squadron, Coos Bay, Oregon. Most of the information in this Staff Report is provided from that document. 3. Remedial Investigation Site Background Site location: Coos Head Road, Coos Bay, Oregon. See attached Figures 1 and 2. The site is located approximately one-half mile west of the city of Charleston, Oregon, and about 5 ½ miles southwest of the city of Coos Bay. Site Description: No water supply wells are reported to be on-site. Future land uses at the site will be community and residential. The Naval Ocean Processing Facility (NOPF) lies adjacent to AOC C. It is an active facility that is still owned and operated by the US Navy. Ownership and operating history Coos Head is in the ancestral territory of the Confederated Tribes. It has been occupied and administered by the US military from the 1874 until The Coos Head location was first developed by the US Government when it was withdrawn from public domain by the Bureau of Land Management for military use on June 14, Until recently, Coos Head was used by the both the Air National Guard and US Navy. The Coos Head military base has been closed since In 2005, the United States deeded the 43-acre Air National Guard portion of Coos Head to the Tribes. The NOPF is a small compound within Coos Head adjacent to AOC C, and it remains under the ownership and control of the US Navy. The Confederated Tribes intend to use Coos Head for housing for tribal members, as administrative offices, and as an interpretive center. Page 2 of 33

3 Environmental Setting Climate information: There are two distinct seasons, a warmer drier season from May through September, and a wet season from October through April. About 60 inches rainfall occurs annually, primarily between October and April. Topography: The top of Coos Head is nearly level, and the head itself is elevated about 100 to 130 feet above the sea. Sandy bluffs on the west and north sides of Coos Head lead down to the beach zone. Coos Head slopes gently down to the east. Surface water hydrology: The closest significant surface waters are the Pacific Ocean and Coos Bay, lying to the west and north of the Coos Head, respectively. Several small springs or seeps are present on Coos Head, but not in the study area of AOC C. Regional and site geology and soils: Coos Head is mostly composed of poorly indurated sandstones or silty sandstones. Soils at the site are mainly sand or sandy loam. Hydrogeology: Depth to groundwater at Coos Head ranges from 12 to 69 feet bgs, and groundwater is often found to be perched upon a bed of shaley siltstone. No water supply wells are known to exist on-site. Locality of the Facility The locality of the facility for groundwater is shown on Figure 2. It encompasses the area that could possibly be affected by the groundwater contamination. Land and Water Use Determinations Current and future land use: Coos Head is not currently occupied (except for a security guard and his family), however, the Confederated Tribes have plans to use the site for any uses. The site is intermittently occupied by workers who come to check on automated equipment. Beneficial use of water: Surface water has not been and has not been impacted by contaminants at the site. No groundwater supply wells are in the area. However, the Confederated Tribes intend to maintain the right to use groundwater in the future. Public water is supplied to the subject properties. The property is owned by the Confederated Tribes, who intend to use it for a variety of purposes, including residential. Page 3 of 33

4 4. Description of Selected Remedy The September 2012 Record of Decision (ROD) presented the selected remedies for AOC C and the remedial goals for the contaminants of concern in groundwater. The remedy selected for AOC B, AOC C Outfall 1, AOC C Outfall 2, and AOC K was excavation and offsite disposal. The remedy selected for soils at AOC C Building 13/Multiple USTs included excavation and offsite disposal for soils in the source area. The remedy selected for AOC C groundwater was in situ air sparging of the groundwater plume. The Record of Decision (ROD) identified four groundwater COCs (benzene, ethylbenzene, naphthalene, and TCE), and the following remedial action objectives (remedial actionos): Reduce COC concentrations in groundwater to levels that allow for future unrestricted use. Prevent human exposure to COCs present in soil and groundwater at concentrations exceeding acceptable risk levels for the residential ingestion, dermal contact, and inhalation exposure pathways. Reduce COC concentrations in soil to levels that protect human and ecological receptors and future groundwater use as a drinking water source. The December 12, 2013 DEQ staff report describes the soil cleanup efforts. Achievement of the acceptable risk level for soil was done at each soil AOC by extending the excavation bounds to or beyond clean sample locations. Post-excavation confirmation samples showed that the actual excavation bounds exceeded the design bounds. The soil remedial goals were achieved as specified by the ROD. A range of remedial action alternatives were developed in the Final Corrective Action Plan in 2012 to address contaminated soil and groundwater associated with AOC C Building 13/Multiple Former USTs. Based on the comparative evaluation of remedial action alternatives, open pit and in situ air sparging was identified as the preferred alternative for treatment of groundwater with COC concentrations exceeding DEQ residential tapwater RBCs. The major components of the preferred alternative as described in the corrective action plan included the following: Open-Pit air sparging. Conduct air sparging in the AOC C Building 13/Multiple Former USTs excavation for 2 days following removal of the contaminated soil. Air sparging was done by attaching a perforated pipe to the excavator arm/bucket and hydraulically pushing the pipe below the water table surface. Then compressed air was injected through the pipe, sparging the exposed soil and groundwater. Concurrent with the air sparging step, the excavator bucket was used to mechanically agitate water saturated soil and groundwater. In situ air sparging. Air sparging was done in the groundwater plume as follows: A design test was done to confirm the radius of influence (ROI) for a typical air sparging well at varying air flow rates/injection pressures. Use the information from Page 4 of 33

5 the design test to develop the air sparging system design and implementation strategy. This work was completed as described in the Remedial Design Investigation Results report (ANG, 2013a). Install an air sparging system, including an array of vertical well points to treat the groundwater plume in accordance with the ROD and results of the remedial design investigation, and the remedial design drawings and specifications. Perform operation and maintenance (O&M) on the air sparging system. Conduct quarterly groundwater monitoring to assess air sparging treatment performance, and continually optimize the implementation strategy. Evaluate and present monitoring results in semiannual progress reports. In the event that remedial goals were not achieved and it was no longer costeffective or technically feasible to continue operating the air sparging system, the ANG as the lead agency, in consultation with DEQ, Confederated Tribes, and the Navy, evaluated the feasibility of implementing other technologies, including monitored natural attenuation for the portion of the plume where the remedial goals were not achieved. The elements of the remedial action objectives related to soil were achieved through completion of the soil remedial action as described in December 12, 2013 DEQ staff report and in the Final Remedial Action Completion Report for Source Area Soil at AOC B Drain Line, AOC C Outfalls 1/2, AOC K Fire Training Area, and AOC C Building 13/Multiple Former USTs (ANG, 2013b). The remedial action objectives were developed based on the current and reasonably anticipated future land and groundwater use. As described in the December 12, 2013 DEQ staff report and in the Final Remedial Design Report/Remedial Action Work Plan for AOC B Drain Line, AOC C Outfall 1/Outfall 2, AOC K Fire Training Area, and AOC C Building 13/Multiple Former Underground Storage Tanks, Former 104th Air Control Squadron, Coos Bay, Oregon (ANG, 2012e), the air sparging system was designed to be operated for a period of up to 2 years; until remedial goals were achieved or the system was no longer effective, or the O&M costs were disproportionate relative to the levels of risk reduction realized. In 2016, an Explanation of Significant Differences (ESD) (ANG, 2016) was prepared in accordance with Section 117(c) of CERCLA and Code of Federal Regulations Title 40 Part (c)(2)(i), to document a significant difference to the groundwater portion of the remedy for AOC C Building 13/Multiple Former USTs by incorporating updated toxicity and exposure information that modifies the remedial goals specified in the ROD for the COCs. These changes were necessary to incorporate the following: The current COC toxicity factor and exposure parameter information that changed since the ROD was issued in This information was obtained from DEQ and U.S. Environmental Protection Agency (EPA) risk assessment guidance. Consideration of central tendency exposure (CTE), per Oregon Administrative Rule (OAR) (1) (g) and Human Health Risk Assessment Guidance Page 5 of 33

6 (DEQ, 2010) requirements, when remediation to remedial goals based on reasonable maximum exposure (RME) RBCs is impractical. Modification of the remedial goals for the groundwater COCs does not change or restrict groundwater use at the Site, and still allows for unrestricted use of the land and/or groundwater per the ROD. Based on current toxicity factors and the CTE scenario, the remedial goals specified in the ROD were updated in the ESD, as shown in following table. Details of the CTE remedial goals are as follows: COC Remedial Goal a Basis for Clean Up AOC C Building 13 and Multiple Former USTs Groundwater (µg/l) Benzene 1.3 CTE Residential RBC for ingestion and inhalation of tap water Ethylbenzene 5.1 CTE Residential RBC for ingestion and inhalation of tap water Naphthalene 0.48 CTE Residential RBC for ingestion and inhalation of tap water TCE 0.89 CTE Residential RBC for ingestion and inhalation of tap water Risk at Remedial Goal 1 in 1,000,000 1 in 1,000,000 1 in 1,000,000 1 in 1,000,000 a Values shown are the lowest of (a) residential exposure (soil ingestion, dermal contact, and inhalation) or (b) residential leaching to groundwater. µg/l micrograms per liter TCE trichloroethene 5. Analytical Results Sampling and analysis of groundwater samples collected from the monitoring wells located in the vicinity of AOC-C Building 13/Multiple Former USTs, where the air sparging remedy was operated from March 2014 to March 2016, shows that the concentration of the site-related COCs identified in the ROD have been reduced to a level that allows for site closure as demonstrated by the residual risk assessment presented in this document. The laboratory analysis results for the groundwater samples collected during the February 2016, May 2016, and August 2016 events are presented in Table 3, and the results for each of the four COCs summarized in the following subsections. Changes in COC concentrations observed between the August 2012 baseline event and August 2014 reflect changes attributable to pulsed air sparging operations, whereas COC concentration changes observed between August 2014 and February 2016 are attributable to continuous air sparging operations. Concentrations present in the May 2016 and August 2016 events show groundwater quality under high and low elevation conditions, respectively, following shutdown of the air sparging system on 17 March Page 6 of 33

7 Overall remedial progress to date is shown by the concentration reductions that have occurred between the baseline monitoring event in August 2012 and the most recent August 2016 event. Several monitoring wells were installed or incorporated into the long-term monitoring network after August Therefore, at these wells which include MW-029 through MW-033 and TMW-02, November 2013 is used for the baseline condition. Laboratory analysis for benzene, ethylbenzene, and TCE was performed using U.S. Environmental Protection Agency (EPA) Method SW Analysis for naphthalene was performed using EPA Method SW Benzene As shown on Figure 3, the initial site groundwater contaminant plume in 2012 was characterized by three lobes extending west-northwest (downgradient) from AOC C with elevated benzene concentrations present in the southernmost lobe in the vicinity of wells MW-024, MW-014, TMW-02, and MW-032. During the February 2016 event, just before air sparging system shutdown, benzene concentrations were present at only 1 of 20 well locations at well TMW-02 (1.99 µg/l). Between the February and May 2016 sampling events, benzene concentrations decreased at well TMW-02 from 1.99 µg/l to 0.70 µg/l. Between the May 2016 (high groundwater elevation conditions) and the August 2016 (low groundwater elevation conditions) events, benzene concentrations increased at TMW-02 from 0.70 µg/l to 1.79 µg/l. Benzene concentrations also increased between the May 2016 and August 2016 events at well MW-024 from 0.36 µg/l to 2.31 µg/l and at well MW-028 from less than 0.15 µg/l (i.e., non-detect) to 1.40 µg/l. The average benzene concentration in groundwater samples collected from the AOC-C Building 13/Multiple Former UST monitoring wells, calculated using the laboratory analysis results from the four most recent monitoring events spanning a one-year climate cycle, ranged from 0.08 to 1.3 µg/l. Ethylbenzene Ethylbenzene concentrations were present at one of the 20 well locations sampled during the August 2012 and November 2013 baseline events. Ethylbenzene, was detected at well MW-032 during the May 2014 event at a concentration of 38.3 µg/l. This detection was co-located with an elevated benzene concentration also observed at this same location in May By August 2014, the concentration had declined to non-detect, where it has remained through August Ethylbenzene concentrations observed during the February, May, and August 2016 events ranged from less than 0.15 µg/l to 0.77 µg/l. Naphthalene As shown on Figure 3, the initial site groundwater contaminant plume was characterized by three lobes extending west-northwest (downgradient) from AOC C. Elevated naphthalene concentrations were initially present at wells MW-024 (0.63 µg/l), MW-017 (5.4 µg/l), and MW-031. Well MW-031 is located on the Navy property (Figure 3). Naphthalene concentrations observed at well MW-031 are associated with residual contamination from the Page 7 of 33

8 historical Navy underground petroleum storage tank on the adjacent US Navy property (DEQ LUST # ) decommissioning activities. Naphthalene concentrations observed at the AOC-C monitoring wells during the February, May, and August 2016 events (Figure 3-4) ranged from less than µg/l to 0.25 µg/l. The average naphthalene concentration in groundwater samples collected from the AOC-C monitoring wells, calculated using laboratory analysis results from the four most recent monitoring events spanning a one-year climate cycle, ranged from 0.01 to 0.24 µg/l. At well MW-031, which was only sampled in February 2016, a naphthalene concentration of 0.95 µg/l was detected. The Navy and DEQ are currently addressing petroleum hydrocarbon contamination present on the Navy property including that detected at well MW-031. Groundwater sampling and analysis at well MW-029 (Figure 1-2), which is located just beyond the southwest corner of the Navy property downgradient of well MW-031. Site investigation work on the US Navy property, has shown naphthalene concentrations ranging from less than µg/l to µg/l. The results indicate that there is no significant naphthalene migration beyond the Navy property boundary. Trichloroethene As shown on Figure 3, the initial site groundwater contaminant plume was characterized by three lobes extending west-northwest (downgradient) from AOC C, with TCE concentrations initially present in the middle lobe at wells MW-014 (0.9 µg/l), MW-012 (1.53 µg/l), and MW-025 (1.22 µg/l). TCE concentrations observed during the February, May, and August 2016 monitoring events (Figure 3-5) ranged from less than 0.15 µg/l to 0.62 µg/l. The average TCE concentration in groundwater samples collected from the 20 AOC-C monitoring wells, calculated using the laboratory analysis results from the four most recent monitoring events spanning a one-year climate cycle, ranged from 0.08 to 0.59 µg/l. 6. Remedial Action The groundwater remedy identified in the ROD was open pit and in situ air sparging. In situ air sparging was chosen to remediate dissolved COCs in groundwater by accelerating the natural biological degradation process and reducing the duration of treatment and performance monitoring. Between August 5, and September 5, 2013, 59 air sparging wells were installed. The remedial implementation was summarized in the Final Remedial Construction Report for the In Situ Air Sparge System AOC C Building 13/Multiple Former UST Groundwater (ANG, 2014a). Air for the air sparging wells was supplied by two different blowers. Each blower was capable of supplying up to 150 standard cubic feet per minute of flow. One blower supplied air to the low submergence zone wells (Zones 1 through 5) and the second to the high submergence zone wells (Zones 6 through 10). The system was equipped with data-logging, remote access, and camera surveillance capability. The air sparging blower system, instrumentation and controls, and air distribution manifolds were housed in a 40-foot-long, trailer-mounted container. Page 8 of 33

9 In September 2014, the air sparging air injection strategy was modified from pulsed to continuous operation. Under this strategy, all 10 zones were open, allowing airflow to all 60 wells, thereby increasing the volume of air injected into the aquifer. The change in operational strategy was made following observations of airflow distribution and aquifer response during the 6 months of pulsed air sparging operations. In a continuing effort to optimize air sparging system performance and accelerate achievement of remedial goals, a targeted sparging strategy was implemented in April Targeted sparging consists of reducing the number of air sparging wells operating, to maximize the effectiveness of the air sparging system, by directing the majority of the airflow to zones where COCs still exceeded remedial goals. This was accomplished by closing individual wells or entire zones in areas where remedial goals had been attained. The change reduced the number of operating air sparging wells from 60 to 31. In addition to maximizing airflow to other wells, the targeted air sparging approach allowed concentration rebound in areas or zones where remedial goals had been attained to be assessed. Following 2 years of operation, the air sparging system was shut down in March 2016, meeting the requirement of the ROD. 7. Residual Risk Human Health The groundwater remedial goals presented in the 2012 ROD were set based on the DEQ acceptable risk level of 1 x 10-6 for carcinogenic COCs and were adapted from DEQ s published RBCs. RBCs periodically change in response to new contaminant toxicity and exposure information. The ROD presented numeric RBCs for each of the four groundwater COCs, corresponding to the 1 x 10-6 acceptable risk level for residential exposure, based on the exposure assumptions and chemical toxicity values published in In November 2015, the DEQ updated its RBCs to reflect current toxicity and exposure information. The November 2015 RBCs are based on the latest DEQ published values for the RME scenario. The RME scenario uses health-protective default values for exposure duration, frequency, and the water ingestion rate. The RME scenario is considered to represent a high-end exposure scenario. DEQ cleanup rules require that CTE also be considered to provide the risk manager with added perspective especially where it is infeasible to remediate to the acceptable risk level based on RME values (Human Health Risk Assessment Guidance, DEQ, 2010). CTE and the COC exposure concentrations are based on average (i.e., the arithmetic mean) versus high-end exposure assumptions. CTE is designed to provide a more realistic exposure scenario for typical exposure conditions and is considered more applicable for the Coos Head site. The primary difference between the RME and CTE exposure scenarios are the exposure duration and the water ingestion rates for adults and children. To demonstrate that COC concentrations in AOC C groundwater meet the 1 x 10-6 acceptable risk level, the excess lifetime cancer risk was calculated at each of the AOC C monitoring wells using the CTE scenario and the average COC concentration present at the monitoring well over the most recent four quarters. Page 9 of 33

10 Since the actual excess lifetime cancer risk is less than or equal to 1 x 10-6, the acceptable risk level has been achieved per OAR (1) and Tables 4 through 6 present the risk calculations for benzene, naphthalene, and TCE and show the achievement of the acceptable risk level at all 20 AOC C groundwater monitoring wells. Achievement of the acceptable risk level in groundwater, in conjunction with the previous soil NFA determination, restores the Site to an unrestricted use condition. Because an unrestricted use condition is achieved, land or groundwater use restrictions are not required at a site. Ecological There are no risk factors for ecological impacts associated with the subject property. Specifically, there are no known threatened or endangered species present at the site. There is no proximal discharge of groundwater to surface waters, and there is no likelihood for groundwater to contact aquatic sediments. Furthermore, groundwater has been remediated to a level that would have no adverse ecological impact. Level I and Level II Ecological Risk Assessments have been completed. 8. Public Outreach The Confederated Tribes has been closely involved with the cleanup process and have been involved with crafting the decision documents. Therefore, a separate public comment period was deemed to be unnecessary, since Confederated Tribes are the relevant public in this case. 9. Conclusions Based on the information available to DEQ, the remediation process at the Coos Head site has been completed. DEQ supports a No Further Action recommendation for this site and will send a No Further Action letter to Confederated Tribes and ANG. The land and groundwater at Coos Head can be used without restriction. 10. Site Reference Material Most of the pertinent information regarding this staff report can be found in the January 2017 No Further Response Action Planned Decision Document Groundwater at AOC C Building 13/Multiple Former Underground Storage Tanks Former 104 th Air Control Squadron, Coos Bay, Oregon. Additional site references are as follows: 1. Air National Guard (ANG) Preliminary Assessment/Site Inspection Report, Building 13/Multiple Former USTs. November Air National Guard (ANG) Remedial Investigation Analytical Data and Quality Assurance/Quality Control Evaluation Results. February Air National Guard (ANG) Air National Guard Investigation Guidance. September. Page 10 of 33

11 4. Air National Guard (ANG) Final Remedial Investigation Report for Multiple Sites, 104th Air Control Squadron, Coos Head Air National Guard Station, Coos Bay, Oregon. February. 5. Air National Guard (ANG) Final Site Assessment Report for Former Underground Storage Tanks P2, Q, R, S, T and Five Soil Stockpiles. April. 6. Air National Guard (ANG). 2012a. Final Corrective Action Plan for Former Underground Storage Tanks P2, Q, R, S, T and Five Soil Stockpiles. February. 7. Air National Guard (ANG). 2012b. Final Proposed Plan for Further Action Sites and No Further Action Sites at the Former 104th Air Control Squadron, Coos Bay, Oregon. February. 8. Air National Guard (ANG). 2012c. Final Record of Decision for Further Action Sites and No Further Action Sites for the Former 104th Air Control Squadron, Coos Bay, Oregon. September. 9. Air National Guard (ANG). 2012d. Final Building 13 Demolition Report Former 104th Air Control Squadron, Coos Bay, Oregon. December. 10. Air National Guard (ANG). 2012e. Final Remedial Design Investigation Work Plan Former 104th Air Control Squadron, Coos Bay, Oregon. June. 11. Air National Guard (ANG). 2013a. Final Remedial Design Investigation Results at AOC B Drain Line, AOC C Outfalls 1/2, AOC K Fire Training Area, and AOC C Building 13/Multiple Former USTs. Former 104th Air Control Squadron, Coos Bay, Oregon. February. 12. Air National Guard (ANG). 2013b. Final Remedial Design Report/Remedial Action Work Plan for AOC B Drain Line, AOC C Outfall 1/Outfall 2, AOC K Fire Training Area, and AOC C Building 13/Multiple Former Underground Storage Tanks, Former 104th Air Control Squadron, Coos Bay, Oregon. June. 13. Air National Guard (ANG). 2013c. Final Remedial Action Completion Report for Source Area Soil at AOC B Drain Line, AOC C Outfalls 1/2, AOC K Fire Training Area, and AOC C Building 13/Multiple Former USTs. Former 104th Air Control Squadron, Coos Bay, Oregon. October. 14. Air National Guard (ANG). 2014a. Remedial Construction Report for the In Situ Air Sparge System AOC C Building 13/Multiple Former USTs Groundwater. 15. Air National Guard (ANG). 2014b. First Semiannual Groundwater Remedial Action Progress Report AOC C Building 13/Multiple Former USTs Groundwater. September. 16. Air National Guard (ANG). 2015a. Second Semiannual Groundwater Remedial Action Progress Report AOC C Building 13/Multiple Former USTs Groundwater. April. 17. Air National Guard (ANG). 2015b. Third Semiannual Groundwater Remedial Action Progress Report AOC C Building 13/Multiple Former USTs Groundwater. July. 18. Air National Guard (ANG). 2015c. Fourth Semiannual Groundwater Remedial Action Progress Report AOC C Building 13/Multiple Former USTs Groundwater. November. 19. Air National Guard (ANG) Explanation of Significant Difference AOC C Building 13/Multiple Former USTs Groundwater. August. 20. Battelle Air Sparging Design Paradigm. 21. (DEQ) No Further Action (NFA) Determination for LUST # Naval Ocean Processing Facility 4300 Coos Head Road, Charleston. DEQ Letter to Mr. Ken Patterson/U.S. Department of the Navy. July 29, Page 11 of 33

12 22. (DEQ) Human Health Risk Assessment Guidance. 23. (DEQ) Letter from OR DEQ to OR ANG and ANG/CEVR Regarding No Further Action for Radar Hill, Stockpile 1, AOC H, AOC F, and AOC G. June (DEQ) Partial No Further Action (NFA) Determination for Former Coos Head Air National Guard Station Coos Head Road, Coos Bay, Oregon ECSI ID No October U.S. Army Corps of Engineers (USACE) In Situ Air Sparging Manual. Engineering Manual January. 26. U.S. Environmental Protection Agency (EPA) A Guide to Preparing Superfund Proposed Plans, Records of Decision, and Other Remedy Selection Decision Documents. July. Page 12 of 33

13 Figures Page 13 of 33

14 Figure 1 Site Vicinity Map Page 14 of 33

15 Page 15 of 33 Figure 2

16 Figure 3 Page 16 of 33

17 Figure 4 Site Cross Section Page 17 of 33

18 Figure 5 Groundwater Elevation Hydrograph Page 18 of 33

19 Figure 6 Page 19 of 33

20 Figure 7 Page 20 of 33

21 Figure 8 Page 21 of 33

22 Tables Page 22 of 33

23 Table 1: Former Underground Storage Tank Description Page 23 of 33

24 Table 2: Remedial Goals for Groundwater Contaminants of Concern Page 24 of 33

25 Table Table 3 Contaminants Contaminants of of Concern Concern Lab Lab Analysis Analysis Results Results Page 25 of 33

26 Table 3 Contaminants of Concern Lab Analysis Results Page 26 of 33

27 Table 3 Contaminants of Concern Lab Analysis Results Page 27 of 33

28 Table 3 Contaminants of Concern Lab Analysis Results Page 28 of 33

29 Table 3 Contaminants of Concern Lab Analysis Results Page 29 of 33

30 Table 3 Contaminants of Concern Lab Analysis Results Page 30 of 33

31 Table 4: Residual Risk Calculation for Benzene Page 31 of 33

32 Table 5: Residual Risk Calculation for Naphthalene Page 32 of 33

33 Table 6: Residual Risk Calculation for TCE Page 33 of 33