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�� Carldno° <br /> ATC <br /> Shaping the rvWra <br /> 1117 Lone Palm Avenue <br /> Suite 201 B <br /> Modesto,CA 95351 <br /> Phone +1209 579 2221 <br /> Fax -1209 579 2225 <br /> www.cardno.com <br /> w .cardnoatcxom <br /> June 1, 2015 <br /> 54.62583.0001 <br /> Ms. Lori Duncan <br /> San Joaquin County <br /> Environmental Health Department <br /> 1868 East Hazelton Avenue <br /> Stockton, California 95205 <br /> Subject: Letter Workplan for the Replacement of MW4, Diamond Foods, Inc. 1050 South <br /> Diamond Street, Stockton, California <br /> Dear Ms. Duncan: <br /> Cardno ATC on behalf of Diamond Foods, Inc., has prepared this brief letter workplan for the <br /> subject site (Figure 1). <br /> INTRODUCTION <br /> Cardno ATC's groundwater monitoring activities in October of 2011 suggested that monitoring <br /> well MW4 (shown on Figure 2) had become obstructed. Subsequent examination of the well <br /> using a camera indicated that approximately 20 feet of the well was filled with what appeared to <br /> be coarse-grained material suspected of being either coarse sand or ground walnut shell related <br /> to on-site processes. <br /> In Cardno ATC's Pilot Study Workplan, Diamond Foods, Inc. 1050 South Diamond Street, <br /> Stockton, California, dated November 7, 2014, Cardno ATC recommended the installation of an <br /> additional nested well near MW3 in support of a remediation pilot study. This Workplan <br /> Addendum recommends replacing MW4 during the same mobilization. <br /> Groundwater Monitoring Well Replacement <br /> Cardo ATC recommends the overdrilling and replacement of monitoring well MW4. Drilling and <br /> well construction will be carried out by a State C57 licensed driller. The existing damaged well <br /> will be overdrilled to a depth of 65 feet bgs and a new well will be constructed in the same <br /> borehole. The well will be constructed with 2-inch Schedule 40 PVC casing to approximately 65 <br /> feet bgs. The screened interval of the well will be positioned from approximately 45 feet bgs to <br />