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0 P!,P.inary Environmental Assessment Report Pittman Elementary School,Stockton,CA December 10,2003 Page 2 • is located within the Stockton Gas Field with several plugged and abandoned gas wells located in the vicinity of the site. Condor reviewed five aerial photographs dated 1938, 1952, 1963, 1975, and 1983 of the site and surrounding area at the San Joaquin County Surveyor's Office. Aerial photographs indicate that land use in Stockton in the vicinity of the site has been urban since at least 1938. The northwestern portion of the site appears to have been used as a lawn-covered park area continuously since 1938. The lawn areas on the northern portion of the site and surrounding many of the structures on the southern portion of the site may be impacted by residual pesticides and herbicides. 3.0 APPARENT PROBLEM The primary objectives of the PEA conducted for the site were to evaluate potential contamination issues and contaminant exposure levels associated with historical land use practices, possible lead-based paint, a leaking UST site located immediately east of the site, a former UST site located north of the site, and the site's position in a known oil and gas field. As stated in Section 2.0, the site was primarily used as a mental health facility since at least 1895. Recently, various buildings on the site have been used as alcohol and drug rehabilitation centers, child abuse prevention centers, or general storage. Potential exposure pathways at the site include inhalation, absorption, and ingestion. 4.0 ENVIRONMENTAL SETTING The land surface in the vicinity of the site is nearly level. The elevation of the site is approximately 20 • feet above the National Geodetic Vertical Datum of 1929. The site is located in the northern San Joaquin Valley in the Great Valley Geomorphic Province. The Great Valley Geomorphic Province is a northwest-trending, westward dipping geosyncline that has been filled with up to six vertical miles of lithified non-marine and marine and unlithified non-marine sediments. Regionally, the upper 3,000 feet of Great Valley alluvial sediments are derived from the Sierra Nevada granitic basement rocks to the east and, to a lesser degree, the Coast Range marine and non-marine sediments and Franciscan and granitic basement rocks to the west. According to published geologic maps,surface deposits underlying the site consist of alluvial sands belonging to the Modesto Formation. These sand deposits are estimated to be more than 9,000-years-old and are underlain by more than 1,000 feet of Cenozoic alluvial sediment. The unconsolidated alluvial sediment rests upon several thousand feet of upper Cretaceous marine sedimentary rock belonging to the Great Valley Sequence. Soils encountered in the immediate vicinity of the site are identified as belonging to the Jacktone-Urban land complex, 0 to 2 percent slopes. The Jacktone-Urban land complex is characterized as being approximately 50 percent Jacktone clay and 35 percent Urban land. The Jack-tone soil is somewhat poorly drained with slow permeability and is formed from alluvium derived from mixed rock sources. The surficial soils observed at the site appeared to be generally similar throughout the site. 4.1 POTENTIAL EXPOSURE RELATED TO SOIL PATHWAYS The site is a portion of a developed property. Grass and trees are present on the approximately 14.5-acre site. Stressed vegetation was not observed during the course of the PEA. Stained areas were not noted at ow IL 4) CONDOR