Imagine the result Site Investigation Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington VCP ID: SW1182 July 29, 2013 Site Investigation Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington 1 Introduction and site Background 1 1.1 Site Description 1 1.2 Site Geology and Hydrogeology 2 1.3 Site History 2 2 Potential Constituents of Concern 5 3 Conceptual Site Model 6 3.1 Potential Constituent Sources 7 3.2 Potential Transport Mechanisms and Receptors 7 3.2.1 Ecological Receptors 9 3.3 Potential Exposure Pathways 9 4 Site Cleanup Levels 9 4.1 Method A Cleanup Levels 9 4.2 Points of Compliance 11 4.3 Applicable Relevant and Appropriate Regulations 12 4.3.1 Federal 12 4.3.2 State 13 5 Compliance with MTCA Statutes and Regulations 13 5.1 Soil 13 5.2 Groundwater 14 5.3 Surface Waters 14 5.4 Sediment 14 5.5 Soil Vapor 15 5.6 Ecological and Natural Resources 15 5.7 Cultural and Archaeological Resources 15 6 2013 Site Investigation Activities 16 6.1 Utility Clearance 16 6.2 Soil Boring Installation 16 i Site Investigation Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington 6.3 Soil Screening and Lithology 17 6.4 Soil Sample Collection 17 6.5 Monitoring Well Development 18 6.6 Groundwater Sample Collection 18 6.7 Investigation Derived Waste Management 19 6.8 Results 20 6.8.1 Soil Analytical Results 20 6.8.2 Groundwater Analytical Results 20 7 Current Site Conditions 21 7.1 Soil 21 7.2 Groundwater 21 8 Conclusion and No Further Action Request 22 9 References 23 Tables Table 1 Historical Soil Analytical Results Table 2 Groundwater Analytical Results – January 2011 and April 2013 Table 3 Soil Analytical Results – April 2013 Figures Figure 1 Site Location Map Figure 2 Aerial Map Figure 3 Site Plan with Historical Soil Boring and Soil Sample Locations Figure 4 Conceptual Site Model of Human Exposure Pathways Figure 5 Site Plan with Soil Boring Locations and Analytical Results – April 8- 11, 2013 Figure 6 Site Plan with Groundwater Analytical Results – April 17, 2013 ii Site Investigation Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington Appendices A Response to No Further Action Request, Ecology 2011 B Soil Boring Logs C Laboratory Analytical Reports and Chains-of-Custody D Monitoring Well Development Logs E Groundwater Sampling Field Data Sheets iii Site Investigation Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington Acronyms and Abbreviations ARCADIS ARCADIS U.S., Inc. bgs below ground surface BTEX benzene, toluene, ethylbenzene, total xylenes COCs constituents of concern CUL cleanup level Ecology Washington State Department of Ecology DRO total petroleum hydrocarbons - diesel range organics EDB Ethylene dibromide EDC 1,2-dichloroethane GRO total petroleum hydrocarbons - gasoline range organics HO total petroleum hydrocarbons - heavy-oil range organics LUST Leaking Underground Storage Tank mg/kg milligrams per kilogram MTBE methyl tertiary-butyl ether MTCA Model Toxics Control Act NFA No Further Action PID photoionization detector PVC polyvinyl chloride site ARCO Facility No. 6008 located at 212 15th Street, Washougal, Washington g/L micrograms per liter USEPA U.S. Environmental Protection Agency UST underground storage tank VCP Voluntary Cleanup Program iv Assessment Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington 1 Introduction and site Background On behalf of BP West Coast Products LLC, ARCADIS U.S., Inc. (ARCADIS) has prepared this Site Investigation Report and No Further Action Request (report) for ARCO Facility No. 6008, located at 212 15th Street in Washougal, Washington (site). On June 30, 2011, ARCADIS requested a No Further Action (NFA) determination for the site from the Washington State Department of Ecology (ARCADIS 2011). In response, the Washington State Department of Ecology (Ecology) determined that further site investigation was necessary prior to issuance of a NFA determination. The Ecology Determination Letter is included in Appendix A. Subsequently, in April 2013, ARCADIS conducted a site investigation to further delineate residual soil and groundwater impacts at the site. This report summarizes the installation and sampling of four soil borings (MW-1 [SB-4], MW-2, MW-3, and SB-5) at the site. Three of the borings were completed as monitoring wells. The objective of this investigation was to define the extent of impacted soil and groundwater exceeding the Model Toxics Control Act (MTCA) Method A cleanup levels (CULs) as presented in tables 720-1 and 740-1 of Washington Administrative Code (WAC) Chapter 173-340-704 (2007). A site location map and aerial map are presented on Figures 1 and 2, respectively. A site plan with historical soil boring locations is presented on Figure 3. 1.1 Site Description The site is located on the northeast corner of the intersection of 15th Street (Washougal River Road) and B Street (Main Street) in Washougal, Washington. The site is improved with one building that is currently operating as an AM/PM convenience store and ARCO-branded service station. Four 10,000 gallon double-walled, fiberglass gasoline underground storage tanks (USTs) are located on the north side of the site. A canopy covering four dual dispenser islands is located west of the station building, and a second canopy covering two dual dispenser islands is located south of the station building. The site is paved with asphalt and concrete. Figure 3 presents the site layout and features. According to the most recent (2012) zoning map produced by the City of Washougal Community Development Department, the site is located within an area zoned as Town Center Core (TCC). This designation provides for mixed commercial and residential use in mid-rise buildings (City of Washougal 2009). This zoning designation is not expected to change in the foreseeable future. 1 Assessment Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington Land use adjacent to the site is commercial and residential. The site is bounded to the north by C Street, to the east by a vacant lot and two residential properties. The site is bounded to the south by B Street and a residential property and to the west by 15th Street and residential properties. Surrounding properties to the east and south are zoned TC-C and to the west across 15th Street are zoned Town Center West Village (TC-WV), which allows for residential and public uses (City of Washougal 2009). 1.2 Site Geology and Hydrogeology The site is situated in the Willamette-Puget Trough, which is bordered by the Cascade Range to the east and the Pacific Coast Range to the west (Mundorff 1960). The site is located in a geographic area known as the Fourth Plains, where Pleistocene age alluvial deposits dominate the geology. These alluvial deposits form a layer ranging from a few feet to 200 feet in thickness. In regions where the alluvial beds are the thickest, groundwater drains out readily and the water table is deeper than in areas with thinner alluvial beds. The principal geologic formation in the region is the Troutdale formation, which consists primarily of sand and gravel in the upper member and silt and clay in the lower member (Mundorff 1960). The site elevation is approximately 50 feet above mean sea level, and the topography of the immediate area gently slopes toward the Columbia River, located approximately 0.2 miles to the south of the site. Soil encountered during previous site investigations has generally consisted of sand and cobbles to the maximum depth explored of 16 feet below ground surface (bgs) (Sweet-Edwards, 1991). During the site investigations conducted by ARCADIS in 2011 and 2013, soils encountered were predominantly gravel with some sand and silt to a depth of 50 feet bgs. 1.3 Site History In July 1989, four soil borings (B-1 through B-4) were installed by Brown and Caldwell on behalf of ARCO as part of a preliminary tank replacement assessment. The borings were installed adjacent to the first generation UST complex, which was located immediately north of the current UST cavity. Refusal was encountered at approximately 3 feet to 4 feet bgs in each of the borings. One soil sample was collected at 4 feet bgs from boring B-4. No total petroleum hydrocarbon (TPH) concentrations were detected in this sample. A photoionization detector (PID) was used to screen soil during boring installation. PID readings ranged from 18 to 190 ppm (Brown and Caldwell 1989). Historical soil analytical results are summarized in Table 1 and soil sample locations are presented on Figure 3. 2 Assessment Report and No Further Action Request ARCO Facility No. 6008 212 15th Street Washougal, Washington In January and February 1990, ARCO contracted Blakeley Construction, under the oversight of Sweet-Edwards/EMCON, to decommission two 4,000-gallon single walled steel construction gasoline USTs, two 6,000-gallon single walled steel construction gasoline USTs and associated product piping, and to install four new 10,000-gallon double walled fiberglass construction gasoline USTs. The former UST complex and the location south of the former UST complex (the new UST complex) were excavated to a depth of 16 feet bgs. The excavation was extended north of the former UST complex to construct a soil treatment gallery (Sweet Edwards/EMCON 1991). Impacted soils encountered during the excavation were found within the boundaries of the former and new UST complexes and were stored on-site pending treatment in the soil treatment gallery.