5200 EVERGREEN WAY 2019-05-29 - Laserfiche WebLink

Former Brien Ford Property Everett, Washington Phase II Supplemental Site Investigation Analytical Results The assessment and cleanup of contaminated sites in Washington State is regulated by the MTCA cleanup regulation, Washington Administrative Code (WAC) 173-340. Concentrations of contaminants detected in the soil and ground water samples obtained during our supplemental site investigation were evaluated with respect to MICA Method A cleanup levels for unrestricted land use. The soil sample results for petroleum hydrocarbons and VOCs are summarized in the attached Table 1. VOCs were non-detect (less than the laboratory reporting limit) in the two soil samples analyzed from the historic dry cleaning building. Petroleum hydrocarbons were non-detect or below the MICA Method A cleanup levels in the soil samples obtained from borings GP-14, GP-15, GP-17, GP-20, GP-22, GP-23, GP-24, GP-25, GP-26, and GP-29. GRPH were detected at concentrations exceeding the MTCA Method A cleanup level in one or more soil samples obtained from borings GP-16, GP-18, GP-19, GP-21, GP-27, and GP-28. The sample obtained from GP-13 at a depth interval of 9 to 10 feet bgs exceeded MTCA Method A cleanup levels for DRPH and ORPH. The sample obtained at a depth interval of 7 to 8 feet bgs from boring GP-16 had concentrations of DRPH and GRPH that exceeded the MICA Method A regulatory cleanup levels (Table 1). However, the detected DRPH concentration in the GP-16 soil sample was flagged by the laboratory as not resembling the chromatographic pattern of the fuel standard for DRPH. The reconnaissance ground water sample results for petroleum hydrocarbons are summarized in the attached Table 2. Petroleum hydrocarbon concentrations were non-detect or below regulatory cleanup levels in the ground water samples obtained from borings GP-15 and GP-24. The GRPH and DRPH concentrations detected in the boring GP-16 ground water sample exceeded the MTCA Method A cleanup levels. Conceptual Site Model The current understanding of the nature and extent of the petroleum-contaminated soil indicates that the contaminants originated from releases from the former USTs and associated piping. The former gasoline fueling facility operated as part of the service department for the former dealership and the tanks were removed in 1989. The release from the tanks appears to have migrated north under the historic dry cleaner building and east toward Evergreen Way. Three subsurface cross-sections were prepared to develop a conceptual model for the site and assist in future remedial excavation design. The cross-sections are presented in Figures 3 through 5. The locations and orientations of the cross-sections are shown on Figure 2. Geologic Cross-Section A-A' (Figure 3) spans the former UST excavation area oriented approximately east-west, perpendicular to Evergreen Way. As shown on Figure 3, the area of known contamination includes soils underlying and directly adjacent to the former UST March 31,2017 ASSOCIATED EARTH SCIENCES,INC. TWL/Id-20160594V002-2-Projects\201605941KVlWP Page 5