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Phase II Environmental Site Assessment Investigation Report
<br />206 Sutter Street, Stockton, California
<br />Page 3
<br />3.2.1 Site Conditions and Observations
<br />On September 22 and 23, 2022, Condor advanced five (5) borings to various depths throughout the Site.
<br />Soil descriptions were annotated on boring logs and soil layers were identified in general accordance with
<br />the USCS. Borings were advanced to various depths: DP-1 was advanced to 60 feet bgs, DP-3 and DP-6
<br />were advanced to 35 feet bgs, and DP-4 and DP-7 were advanced to 45 feet bgs. Sandy clay was consistently
<br />encountered at 0-5 feet bgs; lean clay with silt was encountered at 5 feet bgs to where DP-1, DP-3, DP-6,
<br />and DP-7 borings were terminated. DP-4 encountered lean clay with silt from 5-35 feet bgs, silty sand with
<br />clay from 35-40 feet bgs, and sandy silt with clay at 40-45 feet bgs.
<br />Contamination was observed in the field by discoloration of soil, odor, and PID readings. PID readings
<br />were low in borings DP-4, DP-6, and DP-7; where DP-6 and DP-7 were associated with a brown soil color
<br />and DP-4 was associated with a brown soil color until 25 feet bgs when it was classified with a bluish tint.
<br />PID readings in DP-3 ranged from 0.0 to 2.3 parts per million (ppm) and was identified as medium brown
<br />except from 25-30 feet bgs where it was identified as bluish brown. At DP-1, PID readings were 15 ppm at
<br />10 feet bgs; 5.0 ppm and lower from 15-30 feet bgs; ranged from 50 ppm to approximately 200 ppm at 30-
<br />45 feet bgs; and from 5 ppm to 13 ppm at 45-60 feet bgs with the associated dark blue color. Petroleum
<br />odors were observed with samples associated with elevated PID readings. Groundwater was measured at
<br />an average of depth of 19.5 feet bgs. Geologic logs are included in Appendix C.
<br />3.2.2 Laboratory Analyses
<br />A total of seven (7) soil samples and five (5) groundwater samples were transported under chain-of-custody
<br />procedures for laboratory analysis. Soil samples were analyzed for VOCs, including benzene, toluene,
<br />ethylbenzene, and total xylenes (BTEX), Methyl Tert-Butyl Ether (MTBE), and oxygenated fuel additives
<br />by EPA Method 8260B, and total petroleum hydrocarbons (TPH) as gasoline (TPH-G), TPH Fuel
<br />Fingerprint, including TPH as diesel (TPH-D) and TPH as motor oil (TPH-MO) by EPA Method 8015Bm.
<br />Due to a mix up between documented requested analyses on the field chain-of-custody submitted to the
<br />laboratory and the laboratory staff, groundwater samples collected at DP-1 and DP-7 were analyzed for
<br />VOCs including BTEX, MTBE, and oxygenated fuel additives by EPA Method 8260B, VOCs (BTEX and
<br />MTBE) and TPH-G by EPA Method 8021B/8015Bm, and TPH-D and TPH-MO by EPA Method 8015B.
<br />Groundwater samples collected at DP-3, DP-4, and DP-6 were analyzed were analyzed for VOCs including
<br />BTEX, MTBE, and oxygenated fuel additives by EPA Method 8260B, TPH-G by EPA Method 8015Bm,
<br />and TPH-D and TPH-MO by EPA Method 8015B.
<br />4.0 LABORATORY ANALYTICAL RESULTS
<br />4.1 SOIL
<br />TPH-MO was not detected in any of the soil samples except for at DP-1 at 35 feet bgs at 20,000 milligrams
<br />per kilogram (mg/kg). TPH-G was detected in the soil samples at boring location DP-1 at 35 feet bgs, 45
<br />feet bgs, and 55 feet bgs at concentrations of 540 mg/kg, 330 mg/kg, and 3.3 mg/kg, respectively. TPH-D
<br />was detected in the soil sample at boring location DP-1 at 35 feet bgs and 45 feet bgs at concentrations of
<br />8,000 mg/kg and 2.7 mg/kg, respectively. Xylenes and 1,2,4-trimethylbenzene were detected at
<br />concentrations of 1.1 mg/kg and 0.97 mg/kg, respectively at DP-1 at 35 feet bgs. n-Butyl benzene and n-
<br />Propylbenzene were detected at concentrations of 0.21 mg/kg and 0.35 mg/kg, respectively at DP-1 at 45
<br />feet bgs.
<br />These results were compared to the U.S. Environmental Protection Agency’s Regional Screening Levels
<br />(EPA RSLs) for industrial soil. The TPH-D and TPH-G concentrations at sample location DP-1 at 35 feet
<br />bgs were detected above their respective US EPA RSLs for industrial soil.
<br />Detected laboratory analytical results for the soil samples are included on Table A, Appendix D.
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