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11f[MICX�-IfRXER 3.0 GROUNDWATER AND SOIL INVESTIGATIONS On 7 October 1993, three shallow groundwater monitoring wells were constructed at the request ' of the County The monitoring wells (MW-1, MW-2, and MW-3) were constructed of 2-inch diameter PVC pipe and screen at the locations shown on Figure 1 using the hollow stem auger flight drilling method Soil samples were collected at five-foot intervals using a modified California Split Spoon sampler containing three 2-inch diameter brass tubes Because groundwater was encountered at a depth of approximately b feet below ground surface, the soil sample collected a the 5-foot depth in each boring was selected for laboratory analysis, as it was collected immediately above the groundwater surface Following development of the monitoring wells, the first groundwater samples and water level measurements were collected from each well on 19 October 1993 Information developed from the October well construction and groundwater analysis activities is summarized in the Helmick & Lerner Inc reported dated 30 November 1993 Conclusions presented in the November report included ' • Total petroleum hydrocarbons as diesel, benzene, toluene, ethylbenzene, and total xylenes were not detected in the soil samples collected above the shallow ' groundwater surface at concentrations greater than their method detection limits of 0 005 mg/Kg, 0 005 ug/Kg, 0 005 ug/Kg, 0 005 ug/Kg, and 0 015 ug/Kg, respectively • Calculation of the shallow groundwater flow direction and gradient, based on measured water levels, revealed that the monitoring well locations were adequate for monitoring of groundwater quality downgradient of the former UST location • Total petroleum hydrocarbons as diesel, benzene, toluene, ethylbenzene, and total ' xylenes were not detected in the groundwater samples collected from each of the three monitoring wells at concentrations greater than their method detection limits of 50 ug/L, 0 3 ug/L, 0 3 ug/L, 0 3 ug/L, and 0 9 ug/L, respectively ' A second set of groundwater samples was collected from the three shallow monitoring wells on 31 March 1994 The samples were collected at the request of the County to confirm that ' chemicals were not detectable in shallow groundwater On 29 April 1994, a fourth soil boring was drilled at the request of the County for the purpose of collecting a soil sample from soil immediately beneath the former location of the UST The County requested that this sample be ' collected from a depth of ten feet and analyzed to evaluate whether diesel remained in soil Information developed from the March 1994 groundwater sampling and the April 1994 soil sampling is summarized in the Helmick & Lerner Inc report dated 1 June 1994 Conclusions presented in the June 1994 report included 3