REMOVAL 2009 - Laserfiche WebLink

Home Browse Search

0 • Limited Subsurface Investigation Report —_City of Ripon / Madsen Sunrise Dairy, Ripon, California September 30 2010 In Geoprobe GP -4, no detectable concentrations of TPHd were detected in samples GP -4-25 and G04-29. TPHd was detected in samples, GP -4-5 and GP -440 at concentrations. of 880 ppm and 9.9 ppm, respectively (reported by the lab to be higher boiling point hydrocarbons than typical diesel fuel). In sample GP -4-15, TPHd was detected at 2.4 ppm. In sample GP4-19.5, TPHd'was detected at 1.5 ppm (reported by the lab as discrete peaks in the diesel range). The analytical results from the soil samples are summarized in Table 1. 4.3 Groundwater Analytical Results Groundwater samples collected from Geoprobes GP -1 through GP4 did not contain detectable concentrations of TPHg, except for GP -3-W, in which a concentration 75 parts per billion (ppb) of TPHg was detected (reported by the lab as compounds not found in typical gasoline). TPHd was detected in groundwater samples GP -1-W, GP -2-W and GP -3-W at concentrations of 430 ppb, 260 ppb, and 420 ppb, respectively (reported by the lab to contain discrete peaks and higher boiling point hydrocarbons atypical for diesel). Groundwater sample GP -4-W, showed a concentration of 1,600 ppb diesel (reported by the lab to be higher boiling point hydrocarbons than typical diesel fuel). The analytical results of the grab groundwater samples are summarized in Table 2. 5.0 CONCLUSIONS AND RECOMMENDATIONS Based on the results of the grab groundwater samples collected during this investigation, minor hydrocarbon - impact to shallow groundwater is present at the site. Grab groundwater samples from Geprobes GP -1 through GP -3 showed low concentrations diesel range hydrocarbons. Chromatograms included in this report indicate the presence of diesel, higher boiling point hydrocarbons and unknown compounds in the diesel range (discrete peaks). The source of the high boiling point hydrocarbons and discrete peaks are unknown to GR. A trichloroethene peak in the TPHg chromatogram for sample GP -3-W is thought to be at least partially responsible for the concentration (75 ppb) of TPHg range hydrocarbons detected in this sample (personal correspondence with Kiff Analytical).. Soil samples GP -4-5 and GP -4-10, collected at shallow depths in Geoprobe GP4 contained diesel range hydrocarbons that are higher boiling point than diesel. These two samples were collected in artificial fill materials unexpectedly encountered at the location of GP4. Based on information received from the SJCEHD, it is possible that GP -4 was advanced through the former fuel UST pit referenced in paragraph one of Section 2.2 of this report. The source of the high boiling point appears to be the fill materials imported to the site and used as backfill In groundwater sample GP4-W, a concentration of 1,600 ppb of diesel range hydrocarbons was detected. The hydrocarbons detected in this sample are higher boiling point than diesel. A comparison of the chromatograms for soil samples GP4-5 and GP -4-10 and groundwater sample GP4-W reveal similar patterns suggesting that vertical cross -contamination may be at least partially responsible for the hydrocarbons detected in GP -4-W. The hydrocarbons detected during this investigation are in the diesel range and are primarily higher boiling point hydrocarbons heavier than diesel. These heavy hydrocarbons are non-volatile in nature and therefore GR does not considered them to be a potential source of vapor intrusion risk at the site. In addition, the vapor intrusion to indoor air is not applicable as the site is currently a vacant lot. 25-948223..1-3 4