Laserfiche WebLink
Shell Site Investigation Report <br /> Section 1.0 Introduction <br /> Conestoga-Rovers&Associates (CRA)is submitting this Site Investigation and Well Destruction Report on <br /> behalf of Shell Oil Products US (Shell)to document the recent field work related to the Former Shell <br /> Central Valley Crude Oil Pipelines located at Cordes Ranch in Tracy, California (Figure 1). In May 2014,a <br /> geotechnical investigation was conducted by a third party,which was related to the approved Cordes <br /> Ranch Development Plan. CRA observed the geotechnical drilling activities and collected samples from <br /> geotechnical borings near the former pipelines for chemical analysis. In June 2014, CRA conducted site <br /> assessment work detailed in our March 7, 2014 Site Investigation Work Plan,which the CV-RWQCB <br /> approved in their May 15,2014 letter to Shell. The purpose of this investigation is to delineate crude oil <br /> impacts in the vicinity of monitoring well MW-15 and soil boring B-109. Also in June 2014,CRA <br /> destroyed all site monitoring wells and vapor probes in support of the pending Cordes Ranch <br /> development work. CRA followed the scope of work presented in our May 23, 2014 Well Destruction <br /> Work Plan,which was approved by the Central Valley—Regional Water Quality Control Board <br /> (CV-RWQCB) on May 28, 2014 email correspondence to CRA. The CV-RWQCB work plan approval letter <br /> and email are provided as Appendix A. <br /> 1.1 Site Background <br /> The site is located within a farmed field and topographically slopes toward the northeast. Based on <br /> previous investigations,three water bearing zones (designated as zones A, B,and C) have been <br /> identified and are monitored. <br /> Zone Depth Depth to Groundwater Elevation Typical Groundwater <br /> Interval Groundwater Range (ft MSL) Flow Direction <br /> (fbg) Range (ft bgs) <br /> A 10 to 50 31.84 to 38.65 85.60 to 88.79 North-Northeast <br /> B 105 to 125 24.63 to 36.63 83.84 to 92.79 Northwest <br /> C 160 to 177 50.99 to 57.56 63.30 to 67.81 East <br /> ft bgs=feet below ground surface;ft MSL=feet relative to mean sea level <br /> Soils underlying the site consist of clays and silts and to a lesser extent, sands and gravels that have been <br /> deposited as alluvial fans. <br /> The Central Valley Crude Oil Pipelines carried crude oil from the Central Valley to the Bay Area. The <br /> pipelines are located in the western portion of the Central Valley and the subject site is located near <br /> Tracy, California. Shell operated two pipelines (8 inch and 10 inch diameter)that traversed the site, <br /> oriented in a northwest to-southeast direction through agricultural land. The current site boundaries <br /> encompass approximately 2 miles of former crude oil pipeline ROW located south of Highway 205 <br /> northwest of Hansen Road and north of Schulte Road (Figure 1). The area is primarily undeveloped <br /> , CONESTOGA-ROVERS <br /> 060]]3(35) ' $ASSOCIATES <br /> September 2014 1 <br />