ARCHIVED REPORTS_1999 - Laserfiche WebLink

Home Browse Search

Section 2 Investigation ethods The following section discusses the field procedures and analytical methods used during the implementation of the contaminant plume characterization investigation. Field activities were performed under the direct supervision of a California Certified Engineering Geologist. Site personnel were trained in accordance with the Code of Federal Regulations,Parts 29 Section 1920.120(29 CFR 1920.12c). The investigation activities were performed in general accordance with the Investigation Work Plan dated September 1997 except as noted in Section 2.4. 2.1 Regulatory Permitting and Notification CDM obtained soil boring permits for the installation of temporary soil borings from the San Joaquin County Environmental Health Division(SJCEHD)prior to beginning drilling activities. CDM also obtained an encroachment permit for the installation of temporary soil borings from the San Joaquin County Environmental Department of Public Works(SJCDPW)prior to beginning site activities. Because the work was performed over a period of several months,this permit was renewed as needed to complete the work. An additional encroachment permit was obtained in order to install a temporary culvert for access to soil boring location ARL-3B. CDM notified Underground Service.Alert a minimum of 48 hours prior to initiation of intrusive activities on the site for each mobilization. Copies of the approved SJCEHD soil boring and SJCDPW encroachment permits are included as Appendix A. 2.2 Drilling and Soil and Groundwater Sampling Between December 10, 1997 and June 12,1998,CDM personnel and its drilling subcontractor,HEW Drilling,completed seven temporary exploratory borings as described in the Workplan and as depicted in Figure 2-1. The boreholes were drilled to depths of 66.5 to 180 feet below ground surface(bgs)using a hollow stem auger drilling rig(Central Mine Equipment-95). Groundwater samples were collected using the Hydropunch sampling method in all of the borings at various depths,as shown in Table 2-1. Groundwater samples were analyzed for one or more of the following analyses: volatile organic compounds using EPA Method 8010,dissolved organic carbon using EPA Method 9060,nitrate using EPA Method 352.2,and total iron and manganese using EPA Method 6010. Soil samples were collected in six of the seven boreholes for total organic carbon (TOC)using EPA Method 9060 and grain size analyses using ASTM D421/422. Table 2-1 summarizes date,depth and sample information for all of the boreholes drilled. All samples were submitted to APDL Laboratory for analytical testing. Due to inclement weather,the drilling occurred in several phases. The first four borings(ARL-IA, 1B,2A,and 3A)were drilled in two mobilizations during December 10-18 and January 12-16,but both events were hampered by persistent rain. The winter was unusually wet,so further drilling was delayed. Two more borings,ARL-1C and ARL-4A,were drilled from May 19 to 22, 1998. The CDM Camp Dresser&McKee CS 010762 2-1 W.\REPORTS\STOCKTOMARLPLUME.98GSEC2.WPD CitY of Stockton 190855-0006