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the subsurface materials. The EM-61 measures the induced radio frequency (RF) of the anomaly. Often, buried electrical and telephone utilities radiate their own electromagnetic field and can be readily detected using the RF receiver without inducing a current. By detecting the maximum signal strength at several locations, the surface trace of an underground utility can be determined. The EM-61 equipment is used to induce an RF signal in conductive objects buried to depths as great as 4.6 in (15 feet)bgs. 4.3 Soil Borings Caltrans designated the locations for surface sample collection and specified the sampling protocols. The direct-push and hand-auger soil boring locations were selected by Caltrans following the completion of the visual, GPR and EM surveys. The approximate soil boring locations are shown on Figure 2. 4.3.1 Soil Sampling Procedures Soil borings DPI through DP8 were advanced to a maximum exploration depth of 3.66 in (12 feet)bgs utilizing a truck mounted Geoprobe direct-push rig. Soil samples were collected from the borings utilizing a hydraulically driven soil sampler, equipped with acetate liners. Hand-auger boring HAI was advanced to a depth of 1.07 in (3.5 feet). Soil samples were collected from the hand-auger boring using a sliding hammer equipped with stainless steel sample tubes. After collection, the soil sample tubes were sealed with plastic end caps and silicon tape; labeled; and stored in a cooler chilled with ice pending delivery to the laboratory following standard chain-of-custody protocol for chemical analyses. 4.4 Laboratory Analyses Twenty-seven soil samples were submitted to Creek Environmental Laboratories for the following analyses under standard ten-day turn-around time: • Total petroleum hydrocarbons as diesel (TPHd) and motor oil (TPHmo) by Environmental Protection Agency(EPA)Test Method 8015 Modified. • Soil pH by EPA Test Method 9045 (two soil samples). • Four soil samples were analyzed for Title 22 metals by elements scan using ICAP EPA Test Method 6010 for Total Threshold Limit Concentration (TTLC) metals. The Waste Extraction Test (WET) sample preparation method was performed on three samples which exceeded ten times the soluble threshold limit concentration (STLC) for chromium followed by analysis using EPA Test Method 7000. Title 22 metals include antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum,nickel, selenium, silver, thallium, vanadium, and zinc. One equipment blank was obtained by pouring deionized water over the sampling device and into a laboratory container. The equipment blank was analyzed for TPHd and TPHmo as a means for monitoring the efficacy of the decontamination procedures. Project No S8475-06-70 -6- July 9,2003