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1 + <br /> I <br /> SECOR <br /> International Incorporated <br /> August 15, 2002 RIE <br /> Project 77TO 43870 00 0106 ef-evEn <br /> Mr Michael Infurna AUG <br /> San Joaquin County Public Health Services �Odz <br /> Environmental Health Division ENVIRAMENT <br /> PHESTH <br /> ERMIT <br /> 304 East Webber Avenue, Third Floor /S�RVjC� <br /> Stockton, CA 95202 <br /> Re. Addendum#2 to Work Plan for Additional Off-Site Assessment <br /> Circle K Store#1205 <br /> 16470 Cambridge Street <br /> Lathrop, California <br /> Dear Mr Infurna <br /> This letter, prepared by SECOR International Incorporated (SECOR) on behalf of Tosco <br /> Corporation (Tosco), a subsidiary of Phillips Petroleum Company, provides an <br /> addendum to the work plan for off-site groundwater investigation in the vicinity of the <br /> subject site (Figures 1 and 2) The purpose of this work plan addendum is to document <br /> a change in the construction of the proposed off-site wells <br /> PROPOSED SCOPE OF WORK <br /> As proposed in SECOR's Addendum to Work Plan For Additional Off-Sate Assessment <br /> dated July 16, 2002, which was approved by SJEHD on July 19, 2002, six groundwater <br /> monitoring wells (MW-10 through MW-15) will be installed at the locations shown on <br /> Figure 2 <br /> PROPOSED WELL CONSTRUCTION MODIFICATIONS <br /> As stated in the work plan above, soil borings will be drilled using 8-inch diameter <br /> hollow-stem auger Upon completion of drilling, a 2-inch diameter groundwater <br /> monitoring well will be installed in each boring Groundwater is anticipated at a depth <br /> of approximately 10-12 feet below ground surface (bgs) The wells will be screened <br /> from approximately 5 feet below ground surface to 10 feet below where groundwater is <br /> first encountered <br /> Contrary to the well construction details proposed in the field procedures for <br /> groundwater monitoring well installations provided in Attachment B of the July 16, <br /> 2002 work plan addendum, the wells will be constructed with a sand pack extending <br /> approximately I foot above the top of the screen (approximately 5 feet bgs), followed <br /> by a 2-foot bentonite seal The monitoring wells will then be completed with neat <br /> cement to ground surface The revised field procedures are included as Attachment A <br /> 3017 Kilgore Road, Suite 100, Rancho Cordova, CA 95670 916 861 0400 916 861 0430 Fax www secor com <br />