ARCHIVED REPORTS PHASE II FIELD INVESTIGATION AND LNAPL MOBILITY EVALUATION REPORT

Home Browse Search

ARCADIS Phase II Field Investigation and LNAPL Mobility Evaluation Report Union Pacific Railroad Company ' Former Maintenance Facility Tracy, California Analytical data are summarized in Table 3 and presented on Figure 8. CPT logs ' are included in Appendix A. 3.3 TPCA Pond Investigation On November 11, 2009,ARCADIS supervised Gregg advancing two LIF/CPT borings (LIF-33 and LIF-34) and collecting grab groundwater samples at three locations (HP- 11, HP-16, and HP-18) in the TPCA pond. The bottom of the TPCA pond is lower in elevation than the rest of the Site because the TPCA pond was not backfilled following excavation. The elevation difference was surveyed on February 18, 2010 and was determined to be 10 feet. LIF/CPT borings were advanced with a track-mounted drill rig to approximately 15 feet below the bottom of the TPCA pond (approximately 25 feet bgs). LIF-34 was hand augured to 5 feet logs to clear for underground utilities.A strong petroleum odor was noted while hand auguring was performed. LIF-33 was hand augured to just 1 foot in ' attempt to collect LIF data from the shallow depths. While soil cuttings at LIF-33 had a slight petroleum hydrocarbon odor, the LIF registered fluorescence consistent with site- specific background fluorescence suggesting that residual LNAPL is not likely present ' in the TPCA pond. Grab groundwater samples were collected from approximately the bottom surface of ' the TPCA pond to 5 feet below the bottom of the TPCA pond (approximately 10 to 15 feet bgs), which is consistent with the elevation of the A-Zone groundwater sampled throughout the Site. Samples were collected and analyzed for TEPH-d and VOCs ' following the methods used during the HP/CPT investigation.Analytical results from HP locations advanced in the TPCA pond are summarized in Table 3 and presented on Figure 8. ' Groundwater samples collected from beneath the TPCA pond area indicated high TEPH-d concentrations (maximum of 8,900,000 micrograms per liter[ug/L]at HP-11 as shown on Table 3), indicating the TPCA pond as a potential source area, however, ' the TPCA pond was excavated historically(excavated soil was treated at the nearby biotreatment beds).As mentioned previously, the LIF data did not indicate the ' presence of LNAPL in soil beneath the TPCA pond. mwwr+�waro�momx��izazo�al-aoc 1 8