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d ` FROM : GRD PHONE NO. : 209 267 5370 Mar. 09 1999 11:47AM P4 s I I Field observations and analytical results of samples collect after removal of the USTs indicated soil and groundwater in the vicinity of the USTs has been i acted with petroleum hydrocarbons. Sohl samples collected from the limits of the UST basin conta ned total petroleum hydrocarbons (TPI) as diesel (TPHd) raging from 170 to 1140 milligraml ger kilogram (mg/kg), TPH as gasoline Cnft) ranging from 300 to 1800 mg/kg, benzene ra 1ging from 880 to 2400 micrograms per kilogram(ugft)and metixyl tertiary-butyl ether(MTBE) concentrations ranging from 610 to 21000 ug/kg The UST basin soil samples also contained cowAm rahons of other BTEX compounds ranging flam 82 to 180000 ug/kg. Total lead conations in e UST basin soil samples ranged from 1.6 to 4.5 mg/kg. The groundwater sample contained it TP concentration of 120 milligrams per liter (mg/L), a TPft Concentration of 100 mg/L, a benzem concentration 5100 micrograms per liter (ug/L), and an MTBE concentration of 37000 ug/L. The groundwater sample also contained concentrations of other BTEX compounds ranging fr m 1600 to 7800 ug/L., other oxygenate compounds ranging from less 200 to 7300 ug/I.and a tctal lead concentration of 0.01 m9d, IV. REGIONAL GEOLOGY"ANIS HYDROGEOLOG.. The site is located in the central portion of the Great V0 geomorphic province of California in the eastern San Joaquin-Sacramento Delta region. The province is a north-northwest-trending asymmetrical sedimentary trough measuring approximate y 400 miles long by 50 miles wide. Surma sediments in the site area,generally consist of unconsolids ed Quaternary flood and delta plain at and sand deposits. Groundwater in the delta region is typicallf shallow. Groundwater at the site has been measured at approximately nine feet below ground surface (bgs) in the UST excavation. Groundwater flow directions in the site area are generally westward toward the delta but can vary locally. i I i V_ SCOPE OF WORK The following scope of work is designed to obtain perfinent hydrogeologic information and to investigate the nature and extent of petroleum hydrocarbons in soil and groundwater. The work includes: U drilling of soil borings and collection of soil samples ❑ conversion of the soil borings to groundwater monitoring wells; ❑ monitoring well development; v measurement of static groundwater levels and coil on of groundwater sarnpies; and ❑ data evaluation and compilation in a report. iE � I A. "s of it and Col i n of Soil S es. 'E t All appropriate permits for the drilling of soil borings and the installation of monitoring wells shall 11r0RICPL4.N FOR LIMITED SOIL AND GRO WDWATER INYE,S17GATION SUNNY,SIDE PRODUCE, THORNTON, CAL.I ORAM PAGE 2 �i iE