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Stockton Promenade—N.Ediso street USTs& Utility Corridors • Page 2 Underground Storage Tank Removal Report June 8,2009 - WKA No,1145.09 to the Stockton Channel. Available historical records indicated that these activities were conducted tfrom at least the late 1880s through the 1980s. The former N. Edison Street UST area consists of an approximately 40-foot(ft) by 50-ft area of vacant land located north of Weber Avenue and east of Interstate 5 in the City of Stockton, California(Figure 2 and 3). The site is situated within a predominantly commercial and industrial area of the City of Stockton, adjacent to the Stockton Channel and the Mormon Slough. The site is bordered by the Stockton Channel to the north and the WOTOA parking lot to the south. The former USTs were located within a 40-ft wide unpaved mounded area west of the end of Tuleberg Levee Road (Figure 3). The four USTs were removed from the unpaved mounded area in between the sidewalk and the parking lot. An existing concrete sidewalk along the seawall, and the paved portion of Tuleberg Levee Road, are approximately 4 to 5 feet lower in elevation then the WOTOA parking lot to the south. ' 1.2 Previous Assessment of the Stockton Promenade Several phases of subsurface investigation were conducted immediately west of the former N. Edison Street UST area between February 2007 and November 2007 in preparation for construction of the Stockton Promenade. These investigations included the excavation of numerous exploratory test pits and the collection and laboratory analysis of soil and grab groundwater samples for a variety of analytical parameters. Total petroleum-hydrocarbons as ' diesel(TPHd) and motor oil (TPHmo) were identified in shallow soils and groundwater immediately west of the former N. Edison Street UST area, which was the previous location of large-scale grain milling operations that may have included the use of heavy petroleum products and hydraulic operated equipment. rWKA's Subsurface Investigation Report, dated March 25, 2008, documented the results of soil assessment activities and analytical results, and identified areas warranting mitigation in advance of construction of the Stockton Promenade. As a result of the assessment findings and the proposed redevelopment plan, WKA submitted a Removal Action Plan (RAP) to the RWQCB on June 12, 2008. WKA later issued a letter titled Clarification on Promenade Removal Action on August 25, 2008, which proposed site-specific soil clean-up goals for the identified contaminants of concern. The RWQCB approved the RAP and proposed soil clean-up goals in a letter to the ' RDA dated September 5, 2008.