600 Stewart Street Seattle, Washington 98101 206.728.2674 June 14, 2016 Washington State Department of Ecology 3190 160th Avenue SE Bellevue, Washington 98008 Attention: Heather Vick, Site Manager, Toxics Cleanup Program Subject: Data Gaps Report and Request for NFA Opinion Letter_FINAL 8th and Thomas JVLLC – VCP # NW2976 777 Thomas Street Seattle, Washington GeoEngineers File No. 20341-001-03 OVERVIEW AND BACKGROUND GeoEngineers, Inc. (GeoEngineers) is submitting this letter on behalf of 8th and Thomas JVLLC (8&T JVLLC) to the Washington State Department of Ecology (Ecology) in response to Ecology’s letter dated May 13, 2016 regarding the completed cleanup action at the 777 Thomas Street property (the “Property”) performed by 8th and Thomas JV LLC pursuant to VCP Project No. NW2976. The Property is located in the South Lake Union neighborhood of Seattle. The Property is bounded by Thomas Street to the north, 8th Avenue North to the east, private property (a church) to the south and an alley to the west. The location of the Property is shown in Figure 1. The Property consists of four lots, referred to as Lots 1, 2, 3 and 4. Figure 2 shows the locations of the Lots relative to the surrounding features. The Property and any locations where contamination originating from the Property may have come to be located (the “Site”) was enrolled in Ecology’s Voluntary Cleanup Program (VCP #NW2976) in June 2015 following the cleanup action completed concurrent with redevelopment. The cleanup action consisted of remedial excavation of all contaminated soilduring removal of soil throughout the entire Property to a depth of at least 25 feet below original ground surface, with vertical sidewalls at each of the boundary lines of the Property. A seven story high-rise building with two levels of underground parking (“Mark on 8th”) has since been constructed on the Property. http://www.macfarlanepartners.com/projects/mark-on-8th/ Ecology reviewed the June 2015 VCP application and submittal materials and provided an advisory opinion letter dated May 13, 2016 requesting additional information. For ease of reference, a copy of Ecology’s May 13, 2016 letter is included in Appendix A. This response letter provides the additional information requested, and addresses the data gaps identified by Ecology in their May 13, 2016 letter. All actual and potential releases of contamination at the Site have been adequately characterized and appropriate remedial actions have been completed consistent with MTCA, as demonstrated by the information provided in this letter and attachments. The data confirms that conditions at, on and beneath Washington State Department of Ecology | June 14, 2016 Page 2 the Site no longer pose a threat to human health and the environment, and that a No Further Action (NFA) opinion is warranted. On behalf of 8th & Thomas JV LLC, we request that Ecology review the information provided and issue a No Further Action (NFA) opinion. ASSESSMENT AND CLEANUP ACTION REPORTS The following reports previously provided to Ecology summarize the environmental conditions and completed remedy at the Site: ■ “Subsurface Exploration, 8th and Thomas Site, 777 Thomas Street, Seattle, Washington 98109,” dated January 9, 2009. G-logics, 2009. ■ “Phase I Environmental Site Assessment, South Lake Union Office Building, 215 8th Avenue North, Seattle, Washington 98109, Tax Parcel 1991201100,” dated December 17, 2010. The Riley Group, Inc., 2010. ■ “Phase II Subsurface Investigation and Independent Cleanup Report, Former Holly Press Building, 215 8th Avenue North, Seattle Washington,” dated February 25, 2011. The Riley Group, Inc., 2011. ■ “Phase I and Limited Phase II Environmental Site Assessment, 777 Thomas Street, 223 8th Avenue North and 220 8th Avenue North, Seattle, Washington 98109,” dated December 22, 2011.” Geosyntec Consultants, 2011. ■ “Phase I and Limited Phase II Environmental Site Assessment, 215 8th Avenue North, Seattle, Washington 98109,” dated December 4, 2012. Geosyntec Consultants, 2012. ■ “UST Removal and Cleanup Action Report, 8th and Thomas Development, Seattle, Washington,” dated October 31, 2014. GeoEngineers, 2014. PROJECT DESCRIPTION Construction began for the Mark on 8th project, a seven-story multifamily residential building with two levels of underground parking, in 2014. Construction activities began with the installation of vertical soldier piles and timber lagging around the entire perimeter of the Property to allow mass excavation of all soil contained within the Property to a depth of approximately 25 to 31 feet below the original ground surface (e.g. street grade, which is PHOTO 1: November 11, 2014. Shoring installed around the perimeter of the property and approximately elevation 78 to 81). the beginning of mass excavation (soil removal). Photo 1 (taken on November 11, 2014) shows the shoring system in place and the beginning of mass excavation (soil removal) activities. During mass excavation activities all fill and native soil were removed from the ground surface to a depth ranging from 25 to 31 feet below ground surface (bgs) across the entire Property. No groundwater was encountered File No. 0000-001-00 File No. 20341-001-03 Washington State Department of Ecology | June 14, 2016 Page 3 during construction excavation down to 31 feet bgs. The depth to groundwater was deeper than the lowest elevation of the excavation. It was not necessary to perform any construction dewatering during mass excavation because no groundwater was present. At the time construction began, one 675-gallon heating oil UST had already been removed from Lot 4 (The Riley Group, 2010). Remaining environmental conditions of potential concern identified by the Phase I and II ESAs included two additional underground storage tanks (USTs; one on Lot 1 and one on Lot 3), and one hot spot of residual contaminated soil on Lot 4. The USTs were removed, and contaminated soil in the vicinity of the USTs along with the hot spot on Lot 4 were remediated during the mass excavation activities in 2014. The USTs and contaminated soil were excavated and transported off site for permitted disposal. Confirmation soil samples were obtained to confirm the successful removal of all contaminated soil from the Property (GeoEngineers, 2014). Following the completion of the mass excavation that resulted in the removal of fill and native soil across the entire subject property from ground surface to a maximum depth of 31 feet bgs, the seven-story multifamily residential building with two stories of underground parking was constructed. The completed building is shown in Photo 2. RESPONSE TO ECOLOGY COMMENTS PHOTO 2: Completed Mark 8 Project. Ecology listed ten bulleted comments in their May 13, 2016 letter and requested additional information. The ten comments are summarized below. Ecology’s comments are paraphrased in italic, bold font, followed by the requested information to address the data gap inbulleted paragraphs. Ecology Comments 1, 2 and 3: Historical information indicates the presence of potential sources of volatile organic compounds (VOCs), specifically tetrachloroethylene (PCE), on Lots 1 and 2, which was not investigated. ■ Response: Subsurface explorations were completed on Lots 1 and 2 in 2008 and 2011 by G-Logics and Geosyntec, respectively. Six soil samples obtained from five borings completed on Lot 1 (Figure 3) and three soil samples obtained from two borings on Lot 2 (Figure 3) were submitted for chemical analysis of VOCs. The data are presented in the G-Logics report dated 2009, and the Geosyntec report dated 2011. PCE was not detected in any of the soil samples tested (a total of nine samples).All other VOCs analyzed were not detected in any of the soil samples tested with one exception: 1,2,4-trimethylbenzene (0.067 milligrams per kilogram [mg/kg]) was detected in the soil sample B7-5. A cleanup level for 1,2,4-trimethylbenzene has not been established. In addition, one soil vapor sample was obtained from Lot 1 in 2011 and submitted for chemical analysis of VOCs. Neither PCE nor any other VOCs were detected in the soil vapor sample. Three soil-vapor samples were obtained from Lot 2 in 2011 and submitted for chemical analysis of VOCs. PCE was not detected in each of the soil vapor samples and other VOCs were not detected above screening levels with the exception of trichloroethene (TCE), which was detected at concentrations above the File No. 0000-001-00 File No. 20341-001-03 Washington State Department of Ecology | June 14, 2016 Page 4 screening level in two of the three soil vapor samples obtained on Lot 2. However, TCE was not detected in nearby soil samples and did not exceed criteria in deeper soil vapor samples. A summary of the soil and soil vapor samples obtained and chemical analytical results are presented in Table 1 below. The approximate locations of the historic sources of contamination and the 2008 and 2011 explorations tested for VOCs are shown in Figure 3. The locations of the explorations evaluated for VOCs, as well as the spatial distribution of the borings and the depths of the samples (see cross-section on Figure 3) tested are sufficient to assess for possible VOC releases and their potential impact. As demonstrated by the data, the investigation findings do not show evidence of a VOC release. TABLE 1 SUMMARY OF PRIOR VOC DATA FOR SOIL AND SOIL VAPOR SAMPLES Depth of Exploration Sample Exploration Exploration Sample Location on Sample ID (feet below VOCs ID Date Media Property ground surface) G1 10.17.2011 G-1/25-26 Soil 25-26 ND 12.08.2008 B4-4 Soil 4 ND B4 12.08.2008 B4-12 Soil 12 ND B5 12.08.2008 B5-7 Soil 7 ND Lot 1 B6 12.08.2008 B6-2 Soil 2 ND B7 12.08.2008 B7-5 Soil 5 ND1 <Screening SV1 10.27.2011 SV1/6.7 Soil Vapor 6.7 Levels G4 10.17.2011 G4/7-9S Soil 7-9 ND 12.08.2008 B3-1 Soil 1 ND B3 12.08.2008 B3-14 Soil 14 ND <Screening SV2 10.17.2011 SV2/17 Soil Vapor 17 Lot 2 Levels <Screening SV3 10.17.2011 SV3/7.5 Soil Vapor 7.5 Levels2 <Screening SV4 10.17.2011 SV4/6 Soil Vapor 6 Levels2 Notes: 11,2,4-trimethylbenzene was detected in B7-5 at a concentration of 0.067 mg/kg.