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Stockton Promenade—N. EdisonSfreet USTs& Utility Corridors • Page 15 Underground Storage Tank Removal Report June 8,2009 WKA No. 1145.01 TPHg was not established for the Promenade, TPHg was detected in seven of the eight soil samples collected from beneath the former USTs ranging from 2.5 mg/kg to 920 mg/kg. Nine soil samples were collected and analyzed from exploratory test pits and GeoProbe locations surrounding the former UST area. Six of the nine soil samples had TPHd concentrations in excess of the 500 mg/kg cleanup goal for soil, but none of the samples contained TPHmo concentrations in excess of the corresponding TPHmo cleanup goal of 500 mg/kg. TPHg was detected in eight of the nine soil samples collected surrounding the former UST area and ranged ' from 270 mg/kg to 1,600 mg/kg. Although site-specific soil cleanup goals for TPHg range petroleum hydrocarbons were not previously established for the Stockton Promenade project, the majority of detected TPHg concentrations in soil collected during this assessment were in soil samples collected to the east and south of the former UST area, away from the footprint of the former USTs. The complex distribution of petroleum hydrocarbon-affected soil in this area of the site where there has been significant land use changes over time complicates the identification and characterization of prior petroleum release sources. However, the higher presence of distribution of petroleum hydrocarbon-affected soil to the east and south of the former USTs suggests that ' historical land use activities may have resulted in prior petroleum releases. Further soil sampling and analysis conducted by WKA to the east of the N. Edison Street UST area, as part of ' Promenade underground utility line trenching, also identified similar range petroleum hydrocarbon impacted soil,which suggests other historical release sources not directly associated with the prior presence of the four former USTs. Documentation of these additional soil 1 assessment, excavation, and removal activities will be reported to the RWQCB as part of the Stockton Promenade construction project. Soil Analytical Results—Heavy Metals Soil excavated from each UST location was temporarily placed back into each excavation, after a demarcation liner was installed. Analytical results for the soil sample collected of the contents of Tank#2 and beneath the former UST identified elevated concentrations of cadmium and zinc as compared to the other soil samples analyzed for heavy metals. This finding is consistent with the galvanized coating of Tank#2. Analytical results for soil samples collected beneath Tank#1, #3, and#4 and stockpile disposal profile samples from material excavated around Tank#1 did not exceed applicable regulatory cleanup criteria.