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Herman&Helen's Marina—Work Plan Additional Soil and Groundwater Investigation 1 Surface Water Sampling May 27,1998 Page-3- The Geoprobes will be hydraulically advanced using 2-inch diameter push rods and a conical bit. The rods and bit will be thoroughly cleaned before each borehole is drilled using laboratory grade, non- phosphate detergent and hydrocarbon free water and double rinsing with hydrocarbon free water. The ' Geoprobes will be advanced to the groundwater surface. Groundwater is anticipated to be encountered at 3 to 6 feet below the ground surface(bgs). ' 3.2.2 Hand Auger Borings The terrain where the additional investigation is proposed could best be described as a peat bog. Some areas may be inaccessible by four wheel-drive vehicles. Therefore, some of the proposed Geoprobe borings may be replaced by hand augured borings. When necessary, a four-inch diameter hand auger will be advanced to the desired sampling depth or to a maximum depth of three feet below the capillary fringe (for groundwater sampling). Soil samples will be collected by driving a remote sampling device ' into native soil at the bottom of the boring. The remote sampling device will be fitted with a clean 2- inch diameter brass tube and be prepared as discussed in Section 3.3, below. The auger and down-hole sampling equipment will be thoroughly cleaned as described in Section 3.2.1. Upon completion of the drilling and sampling, all boreholes will be grouted with cement slurry containing 3 to 5 percent bentonite. The slurry will be tremied into the boreholes to avoid bridging. ' There is a potential for artesian flow at proposed boreholes located below the levee. If artesian flow is encountered, the borehole will be backfilled immediately with bentonite chips to within two feet of the ' ground surface. The remaining borehole will be backfilled with a cement slurry containing 3 to 5 percent bentonite. No additional borings will be installed in the immediate vicinity of any location where artesian flow is encountered. t3.3 SOIL SAMPLING Soil samples will be collected from the Geoprobe borings using a three-foot long sampler fitted with ' acetate liners at three-foot intervals, or at significant lithologic changes, in the vadose zone. The soil sampling equipment will be cleaned prior to collecting each sample as discussed in Section 3.2.1. Discrete soil samples will be collected for analysis by cutting a six inch long segment from the desired portion of the soil filled acetate liner. A portion of the liner contents will be used for geological logging and organic vapor analyzer-photoionization detector (OVA-PID) measurements. The samples selected for analysis will be prepared, as described below, for shipment to the laboratory. The samples will be logged according to the Unified Soil Classification System. Drilling logs will be prepared and will include field observations such as estimated moisture content, color,and odor. ' Selected soil samples collected from each borehole will be sent to the laboratory for chemical analysis based on field observations and OVA-PID measurements. At least one soil sample from the vadose zone of each boring will be analyzed. Each sample will be retained, undisturbed, in the acetate liner or brass tube, sealed at the ends with Teflon tape, capped, wrapped with duct tape,and labeled. The samples will be stored in a cooler chilled with ice and delivered within 24 hours of collection, under chain-of-custody ' procedures, to GeoAnalytical Laboratories, in Modesto, California (a California State Certified laboratory). The soil samples will be analyzed using U.S. EPA Methods and California-approved methods following quality assurance measures. Laboratory analyses are discussed in Section 3.5. �� CONDOR