Laserfiche WebLink
1 <br /> ' REPORT <br /> PHASE II SITE ASSESSMENT <br /> ' ALDEN PARK AREA <br /> CHEVRON PIPE LINE COMPANY <br /> TRACY, CALIFORNIA <br /> ' EXECUTIVE SUMMARY <br /> ' In accordance with a scope of work initially developed by Chevron Pipe Line <br /> Company, Dames 6 Moore performed a Phase II Site Assessment at the site of a <br /> ' former locomotive oil storage reservoir facility in the Alden Park area of <br /> Tracy, California in order to: confirm the location of the buried concrete <br /> ' reservoir lining; evaluate the areal extent and concentrations of oil and grease <br /> under residential properties; identify and sample locations of former sumps; <br /> ' evaluate whether liquid oil is present beneath the concrete slab and the extent <br /> of liquid oil outside the slab; evaluate the concentration of dissolved hydro- <br /> carbons just outside the area where oil is visible; and evaluate the direction <br /> and gradient of the water table. <br /> ' The circular concrete reservoir lining was found to underlie almost the <br /> entire area of Alden Park at an approximate depth of 6 feet below ground. The <br /> ' slab location was confirmed by means of five soil probe transects performed at <br /> the slab perimeter. Excavation of two backhoe trenches at the edges of the slab <br /> and one in the middle of the park suggest that in general, the concrete slab is <br /> ' intact. However, at two locations within the perimeter of the slab, probes were <br /> advanced without encountering concrete, suggesting that the concrete is not <br /> everywhere intact. Oil was not found to be pooled at the surface of the slab; <br /> however, soils both above and below the slab do contain visible oil. <br /> ' The distribution of oil and grease in soil above the water table was <br /> investigated by means of 131 shallow probe borings advanced to a depth of 9 feet <br /> ' in the yards of 109 residences in the Alden Park area. Two types hydrocarbon <br /> accumulations were observed; a hard, dry, asphalt-like variety which accumulates <br /> ' in soil at the near-surface (2-3 foot depths) and a liquid oil contained within <br /> the soil matrix, found at the near surface or deeper. Samples from depths of 2, <br /> ' 4, and 8 feet were analyzed for oil and grease content. Concentrations of oil <br /> and grease up to 97,000 mg/kg (ppm) were found at the immediate perimeter of the <br /> ' BFA9/AO <br /> ' Dames S Moore <br />