ARCHIVED REPORTS_XR0002264 - Laserfiche WebLink

Home Browse Search

d� 1 . INTRODUCTION Pacific Gas and Electric Company (PGandE) retained EA Engine- ering, Science, and Technology, Inc. ( EA ) to carry out a soil vapor assessment ( SVA) at its service center in Tracy, California. The area to be investigated was the vicinity around a 1 , 500--gallon fuel tank. Field investigations were conducted by EA on 24 June 1987 under the technical direction of PGandE staff. 1 . 1 SITE DESCRIPTION The PGandE Tracy service center is located lust east of the Southern Pacific railroad tracks, approximately 1 /2 mile south of Grant Line Road. The facility is bordered on the west by the Southern Pacific tracks and the north by the PGandE Tracy sub- station. The land to the east and south is vacant. The service center yard is approximately 350 x 350 feet , with a 100 x 200 foot office building in the northwest quarter ( Figure 1 -1 ) . The northern side of this building is a covered work area. The northwest section of the yard is shown in Figure 1 -2 . The under- ground 1 , 500-gallon gasoline storage tank is approximately 25 feet west of the office building, opposite the work/storage area on the north side as depicted on Figure 1 -2 . 1 . 2 THEORY AND METHODS OF THE SOIL VAPOR ASSESSMENT The soil vapor survey technique takes advantage of the behavior of hydrocarbon mixtures and the physicochemical properties of the individual components in the subsurface . Following a subsurface release of hydrocarbon liquid, free product will migrate down- wards; some constituents will volatilize and some will be adsorbed to the soils . In the case of a spill of sufficient volume to exceed the soil binding capacity, free liquid will reach ground water, at which point it will float and may begin to vaporize and solubilize. 1