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' 1.0 INTRODUCTION On behalf of Valley Showcase Company, JJW Geosciences, Inc., (JJW) has prepared this ' Site Closure Request Report for the Valley Showcase facility located at 901-921 West Fremont Street, Stockton, California. The purpose of this report is to present a brief summary of site description, background, previous site investigations, remediation and groundwater monitoring activities conducted to date and, to discuss rationale for closure. 1.1 Site Location and Description ' The subject property is a former display manufacturing business located on the northwest corner of the intersection of West Fremont and Stockton Streets in Stockton, California ' (Figure 1). The property consists of a commercial building situated on several parcels totaling approximately % acre. Adjoining properties include a light industrial and commercial complex, restaurant, and residential neighborhood. The Stockton Deep Water Channel is located approximately 600 feet south of the site, Stockton City Hall is approximately 0.7 miles to the ' east, and Interstate 5 is approximately 0.4 miles to the west. A single, 500-gallon underground fuel storage tank had apparently been Used to store leaded ' gasoline for use in the company vehicles. The tank was located at the northeast rear of the building (see Figure 2). ' 1.2 Geology and Hydrogeology The site is located near the southern end of the Sacramento Valley, a sub-province of the Great Valley of California. The Sacramento Valley is composed of in excess of 25,000 feet of sediments derived from erosion, reworking, and uplift of the Sierra Nevada Batholith to the east. The sediments range in age from recent to Cretaceous and possibly older, and consist ' of sands, gravels, silts, and clays produced by repeated reworking of the outwash from the Sierras. According to the 1952 publication issued by the University of California, Berkeley, the soil in this area is known as the Stockton Adobe Clay. It is dark gray to brown alluvial soil ' derived as outwash from basic igneous sources, (i.e., the Sierra Nevada Batholith). It is considered to have imperfect drainage, having hardpan subsoil layers generally underlain with unconsolidated material. ' Relief in the vicinity of the site is relatively flat, 5-feet/mile or less, with drainage to the west- southwest towards the Sacramento/Stockton Delta area. The Stockton Deep Water Channel ' is approximately 600 feet to the south. The depth to groundwater was approximately nine feet below ground surface (bgs) during the May 2002 groundwater monitoring event. The groundwater flow direction is toward the north (N 9 E) with a gradient of approximately 0.0046 ft/ft. 2.0 PROJECT HISTORY The Valley Showcase Company was a display manufacturing business that expanded during the past fifty years. A 500-gallon underground storage tank (UST) was installed at the ' property in 1960 and the commercial building was built in 1961. The UST, located at the • northeast rear of the building (Figure 2), was used to store leaded gasoline for use in company vehicles. During removal of the UST from the site on 11 February 1988 it was noted ' that there was a small hole near the bottom bung of the tank. Subsequent environmental investigations determined that soil and groundwater beneath the site had been impacted with ' 1 JJW GEOSCIENCES Inc.