COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

oFeu, BVI E M O R A N D U M Cal/EPA CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL... VALLEY REGION r tlpn ouiT�� (916)255-3000 • CALNET 8-494-3000 • FAX(916)255-3015 Pete Wilson,Governor TO: Wendy L. Cohen l L� _ FROM: G. Arnold Inouye Senior Engineer, SLIC Unit Sanitary Engineering Associate DATE: 14 November 1997 SIGNATURE: SUBJECT: JUSTIFICATION FOR NO FURTHER ACTION, CHEVRON PIPELINE COMPANY, MOUNTAIN VIEW TOWN HOMES SITE, TRACY SAN JOA 0 UIN CO UNTY History In 1995, the Mountain View Town Home site consisted of a three-acre vacant lot at 415 Mount Diablo Boulevard in Tracy. This site corresponds to mile post 215 of Chevron Pipeline Company's former Waite-Mendota-Richmond(WMR)pipeline. The WMR pipeline conveyed crude oil through two 8-inch steel lines between 1902 and 1935. Between 1935 and 1958, fuel oil (Bunker C) was transported through one of the two WMR pipelines. The records are not clear whether the line that ran through the subject property ever conveyed the Bunker C fuel oil. The pipeline was unused between the late 1950's and May 1995 when it was excavated by the Chevron Pipe Line Company in support of a planned affordable housing development by the Rural California Housing Commission (RCHC). Evidence of petroleum-contaminated soil in the subsurface was discovered at seven locations along the 350-foot length of pipeline removed from the site. Investigation The removal of the pipelines and petroleum-contaminated soils from the site were accomplished between 1 May to 24 May 1995. The contaminated soils were disposed of at an appropriate site. Raney Geotechnical (Raney) representing the RCHC was onsite to observe the removal of the pipe lines and collect soil samples. Of the 59 soil samples submitted for analysis, 38 samples contained detectable concentrations of petroleum hydrocarbons ranging from 1 to 4,500 parts per billion. On 26 September 1995, EMCON, consultants for Chevron conducted soil and shallow water sampling at the site. After evaluation of the data from the initial sampling event, EMCON completed additional soil borings to further assess soil and ground water impacts. Xylenes and ethylbenzene were detected at low concentrations in soil samples taken from boring GP-6. No other BTEX constituents were detected in any other soil or ground water sample taken. Of the 16 soil samples taken, polynuclear aromatic hydrocarbons (PAHs)were detected in two samples, one taken from GP-6 and the other from GP-16. No other PAHs were detected in the soil samples. Total purgeable petroleum hydrocarbon (TPPH) was not detected in any of the ground water samples taken. However, TPPH was detected in a soil sample taken from GP-16. Significant levels of total extractable petroleum hydrocarbon (TEPH)were detected in borings GP-6, GP-12, GP-16, and GP-17 completed in the vicinity of an area designated Area 4 by Raney. A discontinuous layer of floating petroleum hydrocarbons was present in a ground water sample collected from GP-6. The summary of the data indicates that the extent of the ground water impact is confined to the immediate area around GP-6. No detectable concentrations of TEPH or BTEX were detected in soil or groundwater samples taken GP-15 which is downgradient of Area 4 . This indicates that hydrocarbons have not migrated downgradient of Area 4.