RECORD OF DECISION - deq.state.or.us • Excavation and off -site disposal of sub-surface soil to a depth ... for excavation workers who might encounter soil or ... Record of Decision

Former Farmington Texaco Record of Decision May 6, 2011

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RECORD OF DECISION

SELECTED REMEDIAL ACTION FOR THE

FORMER FARMINGTON TEXACO SITE ECSI #5546

BEAVERTON, OREGON 1.0 INTRODUCTION AND PURPOSE This document presents the Oregon Department of Environmental Quality (DEQ) selected remedial action at the Former Farmington Texaco site located in Beaverton, Oregon. The remedial action was chosen in accordance with Oregon Revised Statute (ORS) 465.200 et. seq. and is based on the administrative record for this site. This staff report summarizes the more detailed information presented in the soil and groundwater remedial investigation reports and other documents in the administrative record. 2.0 SUMMARY OF SELECTED REMEDIAL ACTION The selected remedial action for site-related soil and groundwater contamination is:

• Excavation and off-site disposal of surface soil containing levels of petroleum contamination above recreational park user direct contact risk-based concentrations (RBCs).

• Excavation and off-site disposal of sub-surface soil to a depth of ten feet in the northeast corner of the site to remove source mass and address risk to excavation workers. As part of this work, a treatment compound will be applied to soil and groundwater to facilitate ongoing contaminant reduction.

• Recording of an institutional control with the property deed memorializing use of the site as a park, prohibiting use of groundwater, and requiring worker notification and/or protection measures for excavation workers who might encounter soil or groundwater contamination in the northeast site corner of the site and in the adjacent right-of-way.

A more detailed description of selected actions for soil can be found in Section 10: Selected Remedial Action. 3.0 SITE DESCRIPTION The Former Farmington Texaco site is located at 13660 SW Farmington Road in Beaverton (see Attachment 1). The approximate 0.5-acre site is bordered by SW Farmington Road to the north, SW Menlo Drive to the east and Eichler Park to the south and west. A closed culverted tributary to Beaverton Creek is immediately east of SW Menlo Drive, approximately 60 feet north and east of the site. The site is currently undeveloped, unpaved, and zoned by the City of Beaverton as General Commercial. This zoning allows for retail, professional services, parks and playgrounds, and urban residential housing. A site vicinity map is presented in Attachment 2. The Former Farmington Texaco site was previously used as a retail petroleum fuel facility and automotive shop that operated from 1963 to 1993. In February 1991, DEQ received complaints from


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local residents describing a petroleum odor and sheen entering a tributary of Beaverton Creek. DEQ required an investigation of the property to determine if a release of gasoline had occurred. Soil borings completed as part of the complaint investigation showed visual evidence of petroleum impacts. The site was entered into DEQ’s leaking underground storage tank (LUST) database and issued LUST # 34-91-0083 on February 8, 1991. Tualatin Hills Parks and Recreation Department (THPRD) is in the process of purchasing the property to expand the adjacent Eichler Park. A preliminary concept plan for the proposed park facilities includes the construction of a skate park (See Attachment 3). Geology and Hydrogeology The site topography is generally flat with little or no elevation change. Regional geology consists of Tualatin River Valley unconsolidated surficial alluvial silts, sands, and clays extending from the surface to an approximate depth of 150-300 feet below ground surface (bgs). Locally, the sediments overlie basalt flows of the Columbia River Basalt Group. Subsurface geology at the site consists of silts and clays to approximately 15 feet bgs, underlain by silty sands and silty gravels. Depth to first-encountered groundwater was identified during site investigations at approximately five feet bgs. Shallow groundwater flow is to the north-northeast. The nearest surface water body is a tributary to Beaverton Creek located in a closed culvert to the northeast of the site (See Attachment 4). A 48-inch storm sewer line runs north-northeast from the site, crossing SW Farmington Road where it joins the Beaverton Creek tributary culvert. From that junction, stormwater is confined to an underground closed storm sewer system that is bedded in a crushed gravel backfill. The culverted storm sewer system is largely underground until it permanently daylights and becomes surface water 0.5 miles northwest of the site. In places, the storm sewer temporarily daylights, with the closest location from the site being 0.25 miles north near the intersection of SW Whitney Way and SW 138th Way. Beneficial Land and Water Use The property is zoned for general commercial purposes which allows for retail, professional services, parks and playgrounds, and urban residential housing. Proposed future use of the property is expansion of the adjacent Eichler Park. A review of Oregon Water Resources Department (OWRD) well logs and water rights information and interviews with the City of Beaverton did not show a beneficial use of groundwater on or near the site. No domestic or community drinking water wells were identified within 0.25 miles of the site. The City of Beaverton provides drinking water in the immediate vicinity of the site and is expected to supply drinking water for the expansion of Eichler Park. 4.0 SITE INVESTIGATIONS Beginning in 1991, a series of environmental investigations were conducted at the site to determine the extent and magnitude of soil and groundwater contamination. A number of soil removal actions and groundwater remediation and removal actions have been performed at the site. A brief description of these actions is described below.


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February-March, 1991 Environmental Field Services (EFS) Investigation In response to a citizen’s complaint regarding observed sheen and odor on a tributary to Beaverton Creek, EFS advanced five hand-auger soil borings on the property, as well as across SW Menlo Drive between the site and the tributary to Beaverton Creek (see Attachment 4). Petroleum impacted soil was observed in borings B-1 through B-3, which were collected on the north, northeast and east sides of the property. No petroleum impacts were noted in borings B-4 or B-5 which were collected southwest of the station building and between the site and the tributary to Beaverton Creek. Based on the observed petroleum impacts, an extraction sump was installed at the southeast corner of the operating underground storage tank (UST) nest. A 30-inch deep trench was excavated from the sump to the southeast corner of the station building for the installation of an air stripper and carbon treatment system (See Attachment 4). Impacted groundwater was pumped from the sump and treated prior to discharge to the adjacent storm sewer under a National Pollutant Discharge Elimination System (NPDES 1500-J) permit. Recovered gasoline product from the treatment system was stored in a 500-gallon waste oil UST. As part of the EFS investigation, Petroleum Services Unlimited, Inc. (PSUI) inspected the UST product lines leading from the tank nest on the east side of the site to the dispenser island on the north side of the site. PSUI noted that the product lines were severely corroded and at least one fitting of the gasoline line had loosened under the east end of the dispenser island. PSUI removed petroleum-impacted soil and replaced the product lines. The site was entered into DEQ’s LUST database on February 8, 1991 and given LUST file number 34-91-0083. In March, 1991, a groundwater monitoring program was initiated and three monitoring wells were installed on the northwest, northeast, and southeast corners of the property to depths of 20 feet bgs (see Attachment 4). The groundwater sample collected from MW-2, located at the northeast corner of the site and immediately downgradient from the tank nest, contained benzene concentrations up to 12,000 ug/L. January 1993, ES&T Consulting, Inc. (ES&T) and Neil Shaw Consulting Geologist, Inc. On January 13, 1993, Neil Shaw Consulting Geologist, Inc. collected a water sample from a storm drain located at the intersection of SW Menlo and SW Farmington Road. The storm water sample analysis indicated the presence of benzene, toluene, ethylbenzene, and xylenes (BTEX). Due to the observed impact to the storm sewer, a collection trench was installed to a depth of 9 feet bgs between the UST nest and SW Menlo Drive. Recovered groundwater was treated using an on-site air stripper treatment system and discharged to the adjacent storm sewer system under a NPDES 1500-J permit. On January 16, 1993, ES&T decommissioned and removed five USTs and their associated piping from the tank nest located on the east side of the site. During the decommissioning, 50 to 100-gallons of separate-phase gasoline product was removed from the tank nest. Concentrations of total petroleum hydrocarbons-gasoline (TPH-Gx) to 3,700 mg/kg were identified in soil samples collected from the tank nest excavation, with the highest concentrations collected from the floor and southern sidewall. An air sparging (AS) system was installed at the bottom of the excavation between 12 and 13 feet bgs. Petroleum impacted soils from the excavation were returned to the tank nest following the UST decommissionings and installation of the AS. The complete duration of operation of the AS system is not known.


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March 1997, K&S Environmental, Inc. On March 31, 1997, K&S Environmental, Inc. installed eight soil borings (B-1 through B-8) on the north, northeast, and east sides of the site (see Attachment 4). TPH-Gx and benzene concentrations to 319 mg/kg and 6.28 mg/kg respectively, were detected in sample B-1 collected immediately downgradient of the former tank nest at a depth of 10 feet bgs. No groundwater samples were collected. June-September 2003, ES&T Consulting, Inc. Twelve soil explorations were advanced to depths of 20-25 feet bgs in June, 2003 (see Attachment 4). TPH-Gx was detected in soil at levels up to 1,080 mg/kg at SB-4, located on the eastern side of the former building. Groundwater samples collected immediately downgradient from the former UST nest contained TPH-Gx to 140,000 ug/L. In September, 2003 ES&T prepared a draft corrective action plan (CAP). The CAP was developed to evaluate: (1) the nature and distribution of TPH-Gx in soil and groundwater; (2) the seasonal elevation and direction of groundwater flow; (3) the expected public exposure to petroleum hydrocarbons from the site; and (4) evaluation of appropriate remedial activities. The CAP recommended an approach incorporating monitored natural attenuation, hydraulic control and groundwater recovery, and ex-situ groundwater treatment. The CAP stated that monitoring wells MW-1 through MW-3 were decommissioned by over-drilling in 2003. November 2007, Wohlers Envrionmental Services, Inc. Wohlers submitted an Environmental Site Assessment Report (ESA) on November 30, 2007. The ESA summarized previous environmental assessment and cleanup activities and presented recommendations for follow-up environmental assessment which included: (1) delineation and assessment of petroleum-impacted soil and shallow groundwater at and adjacent to the subject site; and (2) installation of one off-site and two on-site groundwater monitoring wells; and (3) a minimum of one year of consecutive quarterly groundwater monitoring. On August 21, 2008, DEQ provided a list of eight comments, data gaps, and future actions for the site that recommended:

(1) Delineation of the full vertical and horizontal magnitude and extent of site-related contamination. (2) Investigation of the source and/or pathway of gasoline originally discovered in the tributary to

Beaverton Creek. (3) Review of any other investigations or site reconnaissance performed along Beaverton Creek in

the vicinity of the site. (4) Review of previous investigations within or along the storm sewer lines adjacent to the site. (5) Further investigation in the area north of the former service island and the area near the eastern

property boundary. (6) Further investigation near the former 500-gallon used oil UST. (7) Review of current depth-to-groundwater measurements with those from previous investigations to

identify potential smear zone contamination. (8) A revised work plan to be submitted to DEQ for review and approval prior to implementation.

April 2009, Site Investigation (SI)Ash Creek Associates, Inc. On April 17, 2009, a geophysical survey was performed to identify USTs and other buried features that were not identified during previous site investigation activities and to verify the locations of the former tank nest, former fuel island and former dewatering trench and sump. The survey identified the waste oil


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tank (located on the northwest side of the former building foundation), and verified the locations of the tank nest, fuel island, and dewatering trench. Between April and May, 2009, Ash Creek collected soil and groundwater samples from 12 push-probe locations throughout the site (see Attachment 4). Results of the SI indicated petroleum impacted soil and groundwater in the vicinity of the former UST nest, former fuel island, and the northeast corner of the site. Specifically, elevated TPH-Gx and constituents were generally encountered near the soil-groundwater interface at approximately 7.5 feet bgs to 10 feet bgs at these locations. No separate-phase petroleum hydrocarbons were found in this investigation phase. The SI concluded that the majority of contamination and associated risks were present in the northern portion of the site and within the area of the former tank nest. Additional assessment was recommended to:

(1) Assess the risk associated with the volatilization to outdoor air pathway. (2) Evaluate the storm sewer-groundwater interactions to determine if a preferential pathway exists

for contaminant migration. (3) Assess soil conditions around the waste oil UST. (4) Determine the extent of petroleum hydrocarbons in surface soil. (5) Assess the area proposed for skate park development to determine if petroleum impacted soils

would be encountered during excavation. July 2009, City of Beaverton Sanitary Sewer Upgrade Between July 14, 2009 and July 28, 2009, Ash Creek assisted the City of Beaverton with soil management activities during trenching along SW Menlo Drive (see Attachment 4). During excavation, soil was excavated to an approximate depth of 10.5 feet bgs and was continuously screened with a photoionization detector (PID). In addition, two composite soil samples were collected from locations within the trench and submitted for laboratory analysis of petroleum impacts. No indication of petroleum impacts was noted with the PID or with laboratory analyses. In addition, groundwater that seeped into the bottom of the excavation showed no field evidence of petroleum hydrocarbons. May, 2010 through March, 2011, Ash Creek Ash Creek Associates, Inc. Ash Creek conducted additional SI activities in 2010 to resolve remaining data gaps that were identified during the 2009 SI and prepared an Analysis of Brownfield Cleanup Alternatives (ABCA). The ABCA contains a summary of all site information, risk screening using default DEQ Risk Based Concentrations (RBCs) and site-specific RBCs developed to evaluate future recreational uses, evaluation of possible corrective actions, and a recommendation for corrective action for the site. The ABCA contains all the elements of a Corrective Action Plan, as required by DEQ’s underground storage tank program. Sampling locations from the 2010 SI are presented in Attachment 5. Surface soil samples collected near the former fuel island verified that petroleum contamination is present over a limited area in surface soil at the site. Soil sample PP-16, collected south of the former fuel island, contained a TPH-Gx concentration of 5,300 mg/kg. All other surface soil sample concentrations were below RBCs for dermal contact, ingestion, and inhalation. Subsurface soil samples collected from the vicinity of the former fuel island and the northeast corner of the site contained petroleum contamination between five to 10 feet bgs, which corresponds to the uppermost portion of the water table. Petroleum hydrocarbons and their constituents were below direct contact RBCs for construction and excavation workers but above vapor intrusion RBCs for occupational use. The vertical and lateral extent of contamination at the former waste oil tank was defined with


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petroleum concentrations below applicable RBCs. No PCBs were detected in soil samples collected from beneath the waste oil tank. On and off-site ambient air samples were collected in May and June 2010. The on-site samples were collected from near the former UST nest on the east side of the property, while the off-site samples were collected 100 feet southeast of the property to assess background air concentrations. None of the detected concentrations of volatile organic compounds (VOCs) exceeded site-specific recreational park user outdoor air RBCs developed by DEQ. Historic groundwater elevations were reviewed and storm water samples were collected to evaluate if contamination had or was likely to enter nearby storm sewers, one located immediately north of the property in SW Farmington Road and the other to the immediate east beneath SW Menlo Drive. Storm water samples were collected from the SW Menlo Drive storm sewer in May, June, and October 2010; no petroleum hydrocarbons were detected. Storm water samples were not collected from the SW Farmington Road storm sewer because groundwater elevations were below the level of the sewer pipe in 2010 and 2011. A review of historic water table elevations indicated that while groundwater rises to within approximately 1-foot of the storm sewer, the water table historically does not contact the storm sewer. Concentrations of petroleum hydrocarbons in groundwater adjacent to the storm sewer system are present at levels that exceed DEQ screening values for ecological receptors. However, based on the sum of site information including stormwater sampling results, groundwater elevation data, and the absence of observed contamination in a sewer excavation downgradient of the site, contamination does not appear to be entering the storm sewer system. 5.0 NATURE AND EXTENT OF CONTAMINATION Contaminants of interest (COI) at the site are petroleum compounds and their constituents including TPH-Gx, TPH-Dx, TPH-heavy oil (TPH-HO), BTEX, 1,2,4 trimethylbenzene, naphthalene, lead, ethylene dibromide, ethylene dichloride, metals, polycyclic aromatic hydrocarbons (PAHs) and VOCs. All are apparently related to fuel or waste oil UST systems that were formerly present at the site. Soil. With the exception of the former fuel island area, the majority of the residual petroleum hydrocarbons in soil are located in the so-called groundwater “smear zone”. The smear zone is located in the range of five to ten feet bgs at the site, and is periodically inundated with water. The highest concentrations of petroleum hydrocarbons in soil are located in the former UST nest, the fuel island and the northeast corner of the property. Attachments 6 and 7 show the extent of petroleum hydrocarbons in surface and subsurface soil, respectively. The lateral extent of contamination in soil is estimated to extend approximately 10 to 15 feet into the SW Farmington Road and SW Menlo Road right-of-ways. Within soil, TPH-Gx and Dx are present to maximum concentrations of 5,300 mg/kg and 3,850 mg/kg respectively, while elevated constituent concentrations including benzene and ethylbenzene were detected up to 27 mg/kg and 37.5 mg/kg, respectively. With the exception of arsenic in the former waste oil tank area, detected concentrations of contaminants in soil are below direct contact RBCs for excavation and construction worker receptors. One surface sample location near the former fuel island contains TPH-Gx above the direct contact and volatilization to outdoor air site-specific recreational park user RBCs. Concentrations of benzene and ethylbenzene are also above occupational vapor intrusion RBCs in subsurface soils. Groundwater. Attachment 8 shows the approximate extent of petroleum-impacted groundwater. Petroleum-impacted groundwater is present in the vicinity of the former service island, former waste oil


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tank, and former UST nest. Groundwater contamination is estimated to be impacting SW Farmington Road to the north and SW Menlo Road to the east. TPH-Gx and benzene concentrations in groundwater are present at the northeast corner of the site to maximum concentrations of 140,000 ug/L and 23,000 ug/L, respectively. Groundwater concentrations of TPH-Gx, benzene and naphthalene exceed the direct contact RBC for excavation workers at multiple locations on the north and northeast sides of the property. Benzene concentrations exceed the occupational vapor intrusion RBC, however contaminant concentrations are below all site-specific recreational park user RBCs. Surface Water. Storm sewer sampling conducted in 1993 showed petroleum impact to the storm water system in SW Menlo Drive. Since that time, the UST system was removed, an air-stripper and sump pump were installed in the tank nest, and a groundwater interceptor trench was constructed in the northeast portion of the site (between contamination and the shallower sewer below SW Menlo Drive). Although benzene concentrations up to 13,800 ug/L are present at the northeast corner of the property, the results of the 2010 storm water evaluation did not show any concentrations of petroleum hydrocarbons in the storm sewer. Excavation work completed in 2009 in the street, downgradient of the site, did not identify impacts to soil or groundwater around the sewer prior to its point of discharge at (culverted) Beaverton Creek. Therefore, it appears that petroleum hydrocarbon migration into the tributary of Beaverton Creek, either within the sewer or in backfill around the pipe, is not occurring. 6.0 CONCEPTUAL SITE MODEL The property is zoned for general commercial purposes which allows for retail, professional services, parks and playgrounds, and urban residential housing. According to pending site owner THPRD, future use of the property will be a park. The site is currently located adjacent to a THPRD-owned park (Eichler Park), and redevelopment of the site will allow for expansion of the park. The following current and future potential human receptors were identified for risk-based screening:

• Recreational Park Users • Occupational Workers • Construction Workers • Excavation Workers

Urban residential uses were not included in the risk screening based on the proposed future land use. Urban residential use is allowed under current zoning, however the planned site use (park) does not include urban residential use. Under agreement with THPRD, the selected remedy will include recording an institutional control preventing the construction of habitable structures on the property. Aquatic ecological receptors in surface water could be potentially affected if petroleum hydrocarbons and constituents were to enter the storm sewer system. The following is a summary of each of the applicable exposure pathways for soil and groundwater: Soil

• Vapor Intrusion into Buildings: This pathway is considered potentially complete for occupational workers under a future use scenario.


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• Soil Ingestion, Dermal Contact and Inhalation: This pathway is considered complete for recreational users, occupational workers, construction workers and excavation workers under current and/or future use scenarios.

• Volatilization to Outdoor Air: This pathway is considered complete for recreational users, occupational workers, construction workers and excavation workers under current and/or future use scenarios.

Groundwater

• Vapor Intrusion into Buildings: This pathway is considered potentially complete for occupational workers.

• Volatilization to Outdoor Air: This pathway is considered complete for recreational users and

occupational workers.

• Groundwater in Excavation: This pathway is considered complete for excavation workers. Potable water is provided by the city in the immediate vicinity of the site and will likely continue for the forseeable future. Therefore, consumptive use of groundwater is not considered a complete exposure pathway. 7.0 RISK ASSESSMENT This section discusses human health and aquatic ecological exposure risk screening conducted for the site. Human health risk-based screening was conducted for the receptors and complete exposure pathways previously identified. The concentrations of contaminants of interest in the investigations were compared to either DEQ generic RBCs or site-specific RBCs for a recreational park user exposure scenario. To calculate the site-specific recreational park user RBC, exposure factors were modified from the default exposure factors for DEQ urban residential RBCs. The exposure factors that were modified are summarized in Attachment 9 and include the exposure frequency, exposure duration, exposure time, and the depth to groundwater. For potential ecological receptors, risk screening was completed by comparing storm water samples and groundwater samples from MW-6 to DEQ screening values for ecological receptors. A summary of risk screening conclusions for each applicable exposure pathway is presented below: Direct Contact with Soil and Groundwater

• Recreational park user direct contact risks in surface soil from elevated concentrations of TPH-Gx are present on the south side of the fuel island.

• Concentrations of petroleum hydrocarbons in soil do not result in direct contact risks for excavation or construction workers. The detected concentration of arsenic in subsurface soil exceeded the construction worker RBC in sample TP-2 (9.5 feet-10 feet bgs).


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• Excavation worker direct contact risks in groundwater are present in the vicinity of the former UST nest and the northeast corner of the site due to elevated concentrations of TPH-Gx, benzene and naphthalene.

Volatilization Pathways Soil, groundwater and ambient air data indicate that concentrations of benzene and/or ethylbenzene in subsurface soil exceeded RBCs for the occupational vapor intrusion pathway at the former fuel island, former UST nest and the northeast corner of the site. Naphthalene concentrations in ambient air also exceeded DEQ’s generic occupational air RBC. However, it should be noted that 1) concentrations of naphthalene and other petroleum hydrocarbons were present in the background sample collected at each ambient air sampling event, and 2) occupational exposure at the site is more appropriately evaluated using the site-specific recreational park user RBC given the proposed future use of the site as a park. Ambient air data for the site did not exceed site-specific RBCs for park users developed by DEQ. Ecological Exposure in Surface Water Concentrations of petroleum hydrocarbons in groundwater adjacent to the storm sewer are present at concentrations that exceed DEQ’s screening values for ecological receptors by several orders of magnitude. However, field screening and laboratory analysis of soil and groundwater conducted during sewer excavation activities downgradient of the site in 2009 did not identify contamination in soil or groundwater. Based on this and additional information generated at the site, DEQ has concluded that contaminant migration to Beaverton Creek and potential surface water receptors is not occurring and is not expected to occur in the future. Excess risk has therefore not been identified. Hot Spots Concentrations of petroleum contamination in soil and groundwater did not identify human exposure hot spots. Benzene concentrations up to 13,800 ug/L were found in groundwater, which exceeds the ecological exposure hot spot level of 1,300 ug/L. However, risk to ecological receptors on and downgradient from the site has not been identified. Without a complete migration pathway, hot spots are hypothetical and no additional action is required. 8.0 DESCRIPTION OF REMEDIAL ALTERNATIVES The evaluation of remedial action alternatives includes the following criteria:

• The requirement for a corrective action plan for underground storage tanks as per OAR 340-122-0250.

• The protectiveness of the alternative based on the standards of OAR 340-122-0040; • The feasibility of the alternative based on the balancing factors set forth in OAR 340-122-

0090(3); • Remediation of hot spots of contamination to the extent feasible based on the criteria set forth in

OAR 340-122-0090 (4). A brief discussion of each remedial alternative is presented below. Detailed cost estimates of the remedial options are presented in Attachments 10 through 13. In-situ groundwater treatment of the entire subsurface groundwater potential exposure area was not identified as a cleanup alternative due to the tight


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soil conditions and because the majority of the contaminant mass is located within the near-surface silts where groundwater movement is limited. Common elements of the final remedial actions include abandoning the three remaining site monitoring wells (MW-4, MW-5, MW-6) and implementing an institutional control. The institutional control would include a deed restriction that would prevent the use of shallow groundwater for consumptive purposes and the construction of habitable structures on the subject site. A soil management plan (SMP) would be developed to describe the procedures for management of subsurface soil and groundwater contamination if it is encountered during site redevelopment. The SMP would include information on worker notification for on-site utility work where contamination might be encountered, and the potential need for personal protective equipment if groundwater contamination is encountered. Alternative 1. Excavation and Landfill Disposal of Surface Soil Two areas of surface soil contamination are present to the north and south of the fuel island. Each of these areas is approximately 125 square feet. Accounting for a 3-foot excavation depth to remove petroleum contaminated soil, approximately 30 cubic yards of contaminated soil would require removal. The soil would be transported to a Subtitle D landfill for disposal. Other components of this alternative include site preparation (removing fuel island apron), excavation confirmation sampling, and costs to import and place backfill. The estimated cost for excavation and landfill disposal is $26,526. Alternative 2. Excavation and Land Farming Surface Soil Excavation and land farming of the two areas of surface soil contamination involve constructing a lined soil treatment cell, placing six inches of clean buffer soil on top of the liner to protect it from tearing, excavating the surface soil and placing it in the cell, and then repeated tilling of the soil to aerate and increase bioremediation of the soils. The cell would be constructed to dimensions of 40 feet by 40 feet and surrounded by a perimeter berm to contain the contaminated soil. A tractor/tiller would be used to aerate the soil. Four to six weekly tilling events would be required to remediate the soil. Other components of Alternative 2 include site preparation (removing fuel island apron), excavation confirmation sampling, remedial progress sampling, and costs to import and place backfill. The estimated cost for excavation and land farming of surface soil is $35,532. Alternative 3. In-Situ Land Treatment of Surface Soil In-situ land treatment of the two areas of surface soil contamination involves repeated tilling of the soil in place to aerate and increase bioremediation of the soils. The treatment would be conducted in place, so excavation and soil handling would not be required. A tractor/ tiller would be used to aerate the soil to a depth of three feet. Four to six weekly tilling events would be required to remediate the soil. Other components of this alternative include site preparation (removing fuel island apron), and remedial progress sampling. The estimated cost for in-situ land treatment of surface soil is $33,758.


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Alternative 4. Storm Sewer Protections This remedial action component includes surrounding the storm sewer pipe with a low permeability controlled-density fill (CDF) plug to seal the perimeter of the 48-inch storm sewer line, and lining the first 40 feet of the line to prevent migration of dissolved phase petroleum hydrocarbons in groundwater through joints and cracks in the pipe to the storm sewer line. Implementing this alternative would involve removing pavement from above the area to be excavated for the storm sewer plug and excavating soil to expose the storm sewer line. The plug would be constructed of CDF poured from a concrete truck, up to the subgrade level followed by repaving. Because the plug cannot be installed outside of the extent of groundwater contamination, the alternative also includes contingency for lining the first 40 feet of the storm sewer line. The need to implement the contingency would be confirmed with groundwater analyses that are completed at the time of the plug installation. The estimated cost for the storm sewer protection is $73,553. Alternative 5. Northeast Corner Source Excavation This alternative involves removing soils with petroleum hydrocarbons in the northeast corner of the site that are in close proximity to the storm sewer system and right-of-way. During backfilling, the soil would be amended with a passive oxygen delivery product such as Oxygen Releasing Compound (ORC) manufactured by Regenesis. A water storage tank and pump would be available at the site to recover heavy sheens or separate phase hydrocarbons, should these conditions be observed. The removal would also remove the residual petroleum hydrocarbons in soil and the corresponding groundwater contamination at the northeast corner of the site. Such an excavation would remove the closest source of petroleum hydrocarbons to the storm sewer system and right-of-way, and the downgradient portion of the groundwater area exceeding DEQ RBCs for excavation worker contact. Removal of source area soils and ORC amendment would promote the natural attenuation of residual petroleum hydrocarbons in soil and groundwater. Soils would be excavated from the area shown on Attachment 14. The excavation would remove soils to a 10 foot depth. Prior to excavation, MW-6 would be decommissioned. The north and east terminus of the excavation would be determined based on setbacks (minimum 10 feet from face of curb) from SW Farmington Road and SW Menlo Drive. The total excavation would be approximately 310 cubic yards. During backfilling, the soil would be amended with passive oxygen delivery product such as ORC. Use of this product will result in a cost effective means to further treat residual petroleum hydrocarbons that remain after the source removal. Excavation backfill materials will consist of soil borrowed from elsewhere on the site or imported low permeability soil, similar to native materials. The sidewalk would be replaced as the final step of the restoration. The excavation alternative described above assumes the source excavation can be completed without disturbing traffic flow on SW Farmington Road or SW Menlo Drive and that no excavation dewatering (other than removal of product or sheen) will be required. The excavation would be completed in the summer months when the groundwater level and precipitation rates are lowest. The estimated cost for the northeast corner source excavation is $76,346.


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9.0 EVALUATION OF REMEDIAL ALTERNATIVES The institutional controls will manage future potential vapor intrusion risks through a prohibition of structures across the remedial action area, rendering this pathway incomplete. A prohibition on groundwater use will similarly prevent exposure (note that groundwater use is considered unlikely by DEQ). The soil management plan, if properly implemented, will limit or prevent future worker exposure to groundwater in areas of excess risk, and ensure proper contaminated media management if petroleum contaminated media is encountered in the future. Each of the surface soil actions will effectively remediate soil within the surface interval. The primary contaminant in the vicinity of the fuel island is TPH-Gx. Benzene and other petroleum VOCs are also present. The physical properties of the TPH-Gx and constituents are amenable to both land farming and in-situ land treatment. The storm sewer protections, if implemented, would prevent migration of contaminants to surface water. The plug would ensure that contaminant migration in the trench backfill will not occur, and sealing of the first 40 feet of storm sewer line would prevent infiltration to the storm sewer from either the trench backfill or hydrocarbons in groundwater that have migrated beneath SW Farmington Road with groundwater flow. Because the storm sewer protections are an engineering control, no contamination mass will be removed from the site. [As noted above in Section 8.0, DEQ has determined that off-site migration is not occurring. This remedial option was included in the ABCA and is therefore presented for the sake of completeness. Note, however, that a storm sewer protection remedial option has not been carried forward into the final remedy]. The source excavation alternative would remove contaminated source soils from the area immediately adjacent to the storm sewer and right-of-way. This would remove a significant amount of the contamination mass available for possible migration in groundwater to the storm sewer and right-of-way. Use of the ORC or similar aerobic enhanced bioremediation product during excavation backfill would provide for an additional cleanup of residual petroleum hydrocarbons remaining after excavation. It is expected that natural attenuation would reduce residual hydrocarbons in groundwater within the treatment area, to below RBCs for excavations workers. Excess risk outside of the treatment area would remain. Land farming the excavated soil is feasible and slightly higher in cost that excavation and disposal. The time frame for remediation and safety risks associated with leaving an excavation open during the land farming treatment are greater with land farming than with disposal. The range of costs for the corrective action alternatives is $34,000 to $115,000. Each alternative and the corresponding cost is described in Attachments 10-14 and summarized below:

• Alternative 1 – Implement institutional controls, excavate and treat or dispose surface soil - $34,000;

• Alternative 2 – Implement institutional controls, excavate and dispose of surface soil, complete storm sewer protections - $107,000;

• Alternative 3 – Implement institutional controls, excavate and treat surface soil, complete storm sewer protections - $115,000;

• Alternative 4 – Implement institutional controls, excavate and dispose contaminated surface soils and area of subsurface contamination at northeast corner of site - $110,000;

• Alternative 5 – Implement institutional controls, excavate and land farm contaminated surface soils and area of subsurface contamination at northeast corner of site - $112,000.


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10.0 SELECTED REMEDIAL ACTION The remedial action selected for site contamination by DEQ is generally consistent with that identified in the ABCA and consists of the following:

• Excavation and off-site disposal of surface soil containing levels of petroleum contamination above recreational park user direct contact risk-based concentrations (RBCs).

• Excavation and off-site disposal of sub-surface soil to a depth of ten feet in the northeast corner of the site to remove source mass and address risk to excavation workers. As part of this work, a treatment compound will be applied to soil and groundwater to facilitate ongoing contaminant reduction.

• Recording of a institutional control with the property deed memorializing use of the site as a park, prohibiting use of groundwater, prohibiting the construction of habitable structures across the remedial action area and requiring precautionary measures for excavation workers that might encounter soil or groundwater contamination in the northeast site corner.

Excavation will consist of removal of soil from ground surface to 10 feet bgs in the area identified in Attachment 14 of this staff report. If gross contamination is observed during excavation in adjacent areas outside of the excavation, the potential for limited additional excavation will be discussed between DEQ and the property owner (and/or their consultant). Within the excavation, shallowest groundwater will be “daylighted” throughout the excavation (unless otherwise approved by DEQ), and observations made jointly by THPRD and DEQ as to whether free product, degraded free product, or a heavy TPH sheen is present. If such are observed, they will be pumped from the excavation and transported off-site for treatment and/or disposal. If removal of impacted groundwater is necessary, the excavation will be allowed to recharge at least once, and groundwater entering the excavation inspected prior to application of treatment amendment and backfilling. Any product, degraded product, or heavy sheen-impacted groundwater will be removed following this one recharge event. This selected remedial action provides a protective and cost-effective approach to remediating contaminated soil and groundwater that can be easily implemented, and has a long-term reliability. Protectiveness is achieved by excavation of surface and subsurface soil exceeding RBCs and the addition of ORC to the excavation and backfill material. The last element of the remedy will consist of an institutional control prohibiting the use of shallow groundwater, prohibiting the construction of habitable structures across the remedial action area, and requiring precautionary measures for excavations workers that might encounter soil or groundwater contamination at the site. The estimated cost for the selected remedial action is approximately $110,272. A Remedial Action Plan (or RAP) for implementation of the selected site remedy will be completed by the property owner or a designated agent after approval of the ROD by DEQ’s Northwest Region Administrator, and consistent with the remedial actions outlined in the site Record of Decision. Following the completion of excavation and submission and DEQ approval of a remedial action closure report, DEQ will draft an Easement and Equitable Servitude (EES) to be recorded with the property deed by the property owner. The EES will outline the nature and extent of remaining contamination at the site, restrict the use of groundwater for consumption, and restrict the construction of habitable structures on the site.


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The selected remedial action is protective of human health and the environment. The remedy achieves acceptable levels of risk, as defined by OAR 340-122-0115. A residual risk assessment included a qualitative assessment of the adequacy and reliability of engineering and institutional controls selected to address site risk. The selected remedy for soil achieves protection through a combination of removal (excavation and off-site disposal), in situ treatment and institutional (deed restriction) controls. No human exposure hot spots were identified in soil or groundwater at the site. Ecological hot spots in groundwater were identified due to elevated levels of benzene. However, risk to ecological receptors has not been identified due to the lack of evidence showing migration of contamination into downgradient storm sewers and backfill. This pathway is not considered complete. 11.0 PEER REVIEW SUMMARY A peer review team consisting of a staff hydrogeologist and toxicologist from DEQ’s Northwest Region was convened for this project. They reviewed and commented on all significant project reports, focusing on areas pertinent to their particular areas of expertise. 12.0 PUBLIC NOTICE AND COMMENT DEQ’s proposed remedial action for the site was presented in the Proposed Remedial Action Staff Report For The FORMER FARMINGTON TEXACO Site, ECSI# 5546, Beaverton, Oregon dated March 25, 2011. This Staff Report and supporting documentation of the Administrative Record were made available for public review starting April 1, 2011 at DEQ’s Northwest Region office in Portland. Pursuant to ORS 465.320 and OAR 340-122-0100, DEQ issued a public notice on April 1, 2011 requesting public comment on the proposed remedial action. The public notice was published in the Oregon Secretary of State’s Bulletin and The Portland Tribune newspaper announcing the availability of DEQ Staff Report and Administrative Record for public review during a 30-day period. A copy of the notice is included as Attachment 15. No public comment of any kind was received during the 30-day comment period. 13.0 FINAL DECISION OF THE REGIONAL ADMINISTRATOR The selected remedial action at the FORMER FARMINGTON TEXACO site is protective of present and future public health, safety, and welfare, and of the environment; is based on the balancing of the remedy selection factors; and addresses hot spots of contamination to the extent feasible and necessary. The selected remedial action, therefore, satisfies the requirements of ORS 465-315 and OAR 340-122-0040 and 0090. 13.1 DEQ Signature __________________________ ________________ Nina DeConcini, NWR Administrator Date Department of Environmental Quality


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APPENDIX A ADMINISTRATIVE RECORD INDEX

Ash Creek Associates, Inc. (Ash Creek), 2009a. Site Investigation Report, Metro Brownfields Recycling Program, Former Farmington Texaco, Beaverton, Oregon. June 30, 2009. Ash Creek, 2009b. Technical Assistance – SW Menlo Drive Sewer Trench, City of Beaverton, SW Menlo Drive and SW Farmington Road, Beaverton, Oregon. Project No. 1661-00. August 31, 2009. Ash Creek, 2010b. Field Brief for Phase II Investigation. April 29, 2010. Ash Creek, 2010a. Quality Assurance Project Plan (QAPP) for the Metro Brownfields Recycling Program. May 2010. Ash Creek, 2010c. Field Brief for Additional Activities. November 3, 2010. Ash Creek, 2011. Revised Analysis of Brownfield Cleanup Alternatives, Former Farmington Texaco. March 11, 2011. DEQ, 2002. Default Background Concentrations for Metals. Memorandum to ODEQ Cleanup Project Managers. October 28, 2005. DEQ, 2003. Risk-Based Decision Making (RBDM) for the Remediation of Petroleum-Contaminated Sites. Oregon Department of Environmental Quality – Environmental Cleanup and Tanks Program – Land Quality Division, Portland, Oregon. September 22, 2003. Updated (Spreadsheet) September 15, 2009. DEQ, 2008. Farmington Texaco, LUST Log 34-91-0083, Facility ID #4295, 13660 S.W. Farmington Road,Beaverton. Letter to Mr. Wahlid Mahmood. August 21, 2008. Environmental Field Service, 1991. Farmington Texaco Gasoline Release, Remedial Response and Site Assessment. March 20, 1991. ES&T Consulting, Inc., 2002. Draft Workplan: Soil and Groundwater Investigation Activities, Former Farmington Automotive Site, Beaverton, Oregon. December 8, 2002. ES&T Consulting, Inc., 2003. Draft Corrective Action Plan, Former Farmington Automotive Site, Beaverton,Oregon. September 23, 2003. K&S Environmental, Inc., 1997. Soil Sampling Results and Budget Cleanup Costs for Property Located at 13660 SW Farmington Road in Beaverton, OR. April 17, 1997. Neil Shaw Consulting Geologist, Inc., 1993. Investigation and Cleanup Activities for the Period 1/13/93 to1/21/93 at Farmington Road, Beaverton, Oregon. January 22, 1993. Wohlers Environmental Services, Inc., 2007. Environmental Site Assessment Report, Former Farmington Texaco, 13660 SW Farmington Rd., Beaverton, OR. November 30, 2007.


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APPENDIX B LIST OF ATTACHMENTS

ATTACHMENT 1: Site Location Map ATTACHMENT 2: Site Vicinity Map ATTACHMENT 3: Eichler Park Addition, Concept Plan ATTACHMENT 4: Site Plan with Historical Sample Locations ATTACHMENT 5: 2010 Phase II ESA Sample Locations ATTACHMENT 6: Extent of Petroleum Hydrocarbons in Surface Soil ATTACHMENT 7: Extent of Petroleum Hydrocarbons in Subsurface Soil ATTACHMENT 8: Extent of Petroleum Hydrcarbons in Groundwater ATTACHMENT 9: Calculation of Site-Specific RBC: Exposure Parameter Assumptions ATTACHMENT 10: Brownfield Corrective Action Cost Estimate: Surface Soil Corrective Action

Alternatives ATTACHMENT 11: Storm Sewer Protections ATTACHMENT 12: Brownfield Corrective Action Cost Estimate: Source Excavation ATTACHMENT 13: Brownfield Corrective Action Alternative Cost Estimates ATTACHMENT 14: Corrective Action Alternatives Summary ATTACHMENT 15: Public Notice of Proposed Remedial Action

Documents

RECORD OF DECISION - deq.state.or.us • Excavation and off -site disposal of sub-surface soil to a depth ... for excavation workers who might encounter soil or ... Record of Decision