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PHASE 1I ENVIRONMENTAL SOIL SAMPLING <br /> AT&T MICROWAVE RELAY FACILITY <br /> 90 WEST TURNER ROAD,SACRAMENTO,CALIFORNIA <br /> CONFIDENTIAL AND PRIVILEGED <br /> EXECUTIVE SUMMARY <br /> At the request of the AT&T, ATC Associates Incorporated (ATC), performed a Phase II - Environmental Soil <br /> Sampling investigation of the AT&T Microwave Relay Facility located at 90 West Turner Road, Lodi, California <br />' (Subject Property) (See Figures I and 2) The purpose of the investigation was to evaluate the potential for soil and <br /> groundwater contamination at the Subject Property related to the presence of a former underground storage tank <br /> (UST) The investigation is in accordance with an authorization to proceed from AT&T, dated May 6, 1999 <br />' Ten soil borng s were drilled on the Subject Property, and 15 soil samples and 8 water samples were collected and <br /> i <br /> submitted selectively for laboratory analysis for total petroleum hydrocarbons — diesel fuel (TPH-D), benzene, toluene, <br /> ethylbenzene, and total xylenes (BTEX), and methyl tert-butyl ether(MTBE) Figure 3 shows the locations of the soil <br /> borings Soil and water samples were collected from bonngs dnlled in the vicinity of the former UST <br /> Based on the results of laboratory analyses of soil samples collected as part of this Phase II investigation, and <br /> analytical results from the previous UST removal investigation, diesel impacted soil appears to be confined to the <br /> Immediate vicinity of the former UST excavation in an area of approximately 25 feet long by 25 feet wide The limits <br />' of diesel fuel impacted soil are presented in Figure 4 Soil boring B 1 encountered diesel fuel at a concentration of 490 <br /> ppm at a depth of 26 feet below ground surface (bgs), just above the depth to groundwater Diesel fuel was not <br /> encountered in the soil bonngs surrounding the former UST (B4, B5, B2, or B7) to a depth of 32 feet bgs Therefore, <br /> it is likely that diesel fuel is present in the soil in the depth interval from 12 feet bgs (the depth of the slab beneath the <br /> former UST) to approximately 27 feet bgs (the depth to groundwater) <br /> Analytical results of groundwater samples indicate that diesel fuel in the groundwater has migrated from the former <br /> UST excavation to the south and east The diesel fuel contaminated groundwater appears to be laterally confined to an <br /> area approximately 60 feet long by 35 feet wide The limits of diesel fuel impacted groundwater are presented in <br /> t Figure 5 Diesel fuel is found at a maximum reported concentration of 150 ppb in boring B2 and attenuates to a <br /> concentration of 58 ppb in boring B3, 20 feet farther to the south No BTEX or MTBE was detected in the <br /> groundwater samples collected from the borings, with the exception of total xylenes detected in the sample from boring <br />' B2 at 12 ug/L <br /> The majority of soils encountered in borings appeared to be fine to medium sand and silty fine sand The silty fine to <br /> medium sand with some gravel encountered in boring B 1 is interpreted as fill material related to the backfilling of the <br /> t UST excavation <br /> Based on laboratory analytical results and field observations, ATC recommends that three groundwater wells be <br /> installed in the vicinity of the former UST in order to further define groundwater gradient and diesel fuel <br /> concentrations It is anticipated that after one year of monitonng, a risk-based analysis will be performed on the site in <br /> order to obtain regulatory closure Additionally, research should be performed on the two groundwater production <br />' wells on site in order to determine the depth of the screened intervals and the potential for impact from the former UST <br /> i <br />