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Additional Site Assessment Work Plan - Addendum <br />WEST CLAY PROPERTIES <br />639 West Clay Street, Stockton, California <br />1.0. INTRODUCTION <br />At the request of West Clay Properties-KRC, Advanced GeoEnvironmental, Inc. (AGE) <br />has prepared this Additional Site Assessment Work Plan - Addendum for the site located <br />at 639 West Clay Street, Stockton, California (site). <br />The scope of work includes: <br />Advancement of three soil probe borings off-site, towards the northeast of well <br />MW-29 for the collection of deep groundwater samples from Hydrogeologic Unit 2 <br />(HU2: 40-60 feet below surface grade bsg) and Hydrogeologic Unit 3 (HU3: 62-90 <br />bsg) to define the down-gradient lateral and vertical extent of petroleum <br />hydrocarbon-impacted groundwater in HU2 and HU3; <br />Installation of one deep-screened (75-85 feet bsg) groundwater monitoring well in <br />HU3 to define the vertical and down-gradient extent of petroleum hydrocarbon- <br />impacted groundwater in the vicinity of MW-29. <br />The work plan provides a description of the scope of work and procedures to be used for <br />soil probe and pilot boring advancement, groundwater sample collection and analysis, <br />monitoring well development and survey, and probe boring abandonment. A location map <br />depicting the site and surrounding area is provided in Figure 1; a site map depicting site <br />features and proposed soil boring and monitoring well locations is presented in Figure 2; <br />and well construction details are presented in Table 1. <br />The work plan was prepared as directed by California Regional Water Quality Control <br />Board (CRWQCB) letter, dated 26 July 2016 (Appendix A). Additionally, this work plan <br />was prepared in accordance with guidelines issued by the CRWQCB for investigation of <br />underground storage tank (UST) sites. <br />2.0. BACKGROUND <br />The site is located in the western-central portion of Stockton, CA, in an area of mixed <br />residential and business. The site is located 130 feet west of the intersection of West Clay <br />Street and Harrison Street and is one parcel out of the seven adjacent parcels that are <br />owned by the Knife River Corporation (Figure 2). <br />Shallow soil remediation was previously performed in two separate phases at each UST <br />area; primarily during the UST removals and subsequently during deeper excavations of <br />impacted soils extending to the upper portion of the water table. <br />,4dvanced GeoEnvironmental Inc.