ARCHIVED REPORTS XR0013118 - Laserfiche WebLink

Home Browse Search

..y Mr. M. Scott Mansholt—ChevronTexaco January 13,2005 Soil and Groundwater Investigation Report—Pombo Property Page 5 of 8 (SB-6). BTEX compounds were non-detect in all grab groundwater samples. A phenanthrene ��✓✓✓ concentration of 0.4µ/L was detected in grab groundwater sample SB-1. PAHs were non-detect in all other grab groundwater samples. CONCLUSIONS Soil and grab groundwater samples were collected from 11 soil borings installed to further assess soil and groundwater impacts along the WSID easement,and to delineate the down gradient extent of petroleum- affected soil and groundwater along the WSID easement and in the residential housing development down gradient of the Pombo Property. The 2001 proposed percolation/retention pond footprint and approximate area of excavated of petroleum-affected soil are shown on Figure 2 as requested in the RWQCB letter, dated August 21,2003. The following conclusions are based upon the results of soil and groundwater analyses and a 2,000-foot radius well survey conducted during the current investigation. The extent of petroleum-affected soil down gradient of the Pombo Property has been delineated by borings SB-1 through SB-6. Concentrations of dissolved TPHd were detected in grab groundwater samples down gradient(SB-1, SB-2, SB-7,and SB-8)and crossgradient(SB-10 and SB-I 1) from the Pombo Property. Based upon dissolved TPHd analytical results,petroleum-affected groundwater north(down gradient)of the Pombo Property has been delineated by borings SB-8 through SB-9. The distribution of dissolved TPHd concentrations lateral to the Pombo Property along the WSID easement indicate that petroleum- affected groundwater may be impacted from areas not associated with the Pombo Property. The 2,000-foot radius well survey identified an industrial supply well(Map ID 4) located northeast(down gradient)of boring location SB-9 at a presumed distance of approximately 1,000 feet; information regarding well location and well construction was not specified. Boring SB-9 was non-detect for TPHd. All other identified wells were located cross gradient and up gradient to the Pombo Property. Analytical results from this investigation indicate low-and non-detect concentrations for constituents of concern (TPHd, BTEX and PAHs)in groundwater down gradient of the Pombo Property and serve to extend the analytical data set for the Pombo Property and its previous investigations. Based on the results of this and previous investigations, SAIC recommends a request for no further action and the preparation of a comprehensive site data summary addressing site closure for the Pombo Property. If there are any questions pertaining to the content of this report,please contact Douglas Umland at (510)466-7145. Sincerely, SCIENCE APPLICATIONS INTERNATIONAL CORPORATION Ellen Avery Douglas K. Umland,RG Staff Geoscientist Senior Geologist /\ tlr� t i)CivG1 As 1