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CLEARWATER <br /> G R O U P, I N C <br /> 1.0 INTRODUCTION <br /> This report presents the results of well installation, pilot testing, and soil and <br /> groundwater sampling activities conducted by Clearwater Group, Inc (Clearwater) at <br /> the Conrady property located at 1002 North Yosemite Street in Stockton, California <br /> (Figure 1). The tasks performed were , <br /> • Installed one offsite groundwater monitoring well <br /> • Installed two soil vapor extraction (SVE) wells and two air sparge wells <br /> • Advanced one soil boring using cone penetrometer testing (CPT) equipment <br /> • Conducted quarterly groundwater monitoring for the tbard quarter of 1995 <br /> ' Conducted a pilot test of the SVE and air sparge wells <br /> '4 <br /> ' 1.1 Site Description and Background <br /> No structures are currently present at the subject location, it is a vacant lot <br /> surrounded by a chain-link fence Records indicate that the site was used as a <br /> gasoline service station from 1961 to 1978, and that the underground fuel storage <br /> ' tanks (USTs) were removed in 1980 An environmental assessment conducted in <br /> 1990 by Evax Technologies, Inc consisted of a limited soil gas survey The purpose <br /> of their investigation was to identify any po+tential subsurface contamination in the <br /> ' vicinity of the three former USTs. The soil gas survey indicated, the possible <br /> presence of petroleum hydrocarbons in the soil <br /> Following this initial discovery, GeoAudit was retained to conduct a more , <br /> I <br /> comprehensive subsurface investigation The investigation consisted of drillingsix , <br /> soil borings to depths between 29 5 and 36 5 feet below ground surface (bgs), and <br /> collecting soil samples at five ;foot intervals. Laboratoryanalysis of soil samples <br /> collected by GeoAudit indicated the presence of relativelyow levels of eth lbenz <br /> I y ene i <br /> in the soil around the western edge of the property Subsequeritly, San Joaquin <br /> ' 'County Public Health Services Environmental Health Division (PHS) directed the <br /> property owner to install monitoring wells and to begin quarterly sampling <br /> In accordance with PHS directives, GeoAuditl completed installation and sampling Ilii ` '{ <br /> of three groundwater, monitoring wells (MwW-1 through,+MW-3) in October 1993 G�I' I <br /> The 'highest concentrations' 'of volatiles ere] found,i!in I'groundwater samples , <br /> I � 4 11 II I i <br /> collected,from MW-2, located near the former,UST area ,i'A detailed presentation of <br /> t l I ,, l 1 I � l ,,, I , I I <br /> the uutial site assessment +is,presented) inn IGeoAudit's November 1993` Monitoring <br /> I� Well Installation)land Quarterly Report li���li i �`i� <br /> I I I + <br /> I lit <br /> 4l b101 PAR/3,4/PIIOTf{ ��� l IIS <br /> , ! <br /> t I <br /> '� ���II � � I i � it (��l '�,�� �I'I I I��i i �,I�`II i �� +� I i � �, �k + Il�d'� � ►I�IE� I''�I' � I�'I' ! , � i I Ik1� <br /> ,f I I I i�qudlli I�It I fit I �iil��ll Ii,J`}i' <br />