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Irr <br /> Site Background Information:-Vasco Truck &Auto Laza <br /> Page 4-of.6 <br /> serving-as a preferred migration route, and could­potentially allow migration of large <br /> contarninant-masses over great distances. <br /> The model presented•is interpretational and will be Modified as more data is collected.The <br /> eight vertical zones are identified as follows (depths are approximate and:can vary by <br /> several feet-across the site)! <br /> I <br /> Vadose/First Water Zone This zone extends from urface grade to approximately 20 feet <br /> bsg,,Static water.-is at 20 feet bsg in the monitoring Neils, however;the-first saturated soil <br /> samples were collected at,30 feet.bsg. This indicat Las.that-the water table is confined-by <br /> the overlying fine-grained materials. This zone is characterized by moderate pore <br /> pressures. <br /> Hydrogeologic Unit 1 (HU1) Extending from 20 feet to approximately 30 feet bsg, HU1 is <br /> comprised predominantly of sandy silt,, clayey Silt;_L and silt:L Dominant hydraulic <br /> conductivities,based on CPT-soil behavior types(S 7s),grange between 1 x 10 and 1 x 104 <br /> centimeters per-second (cm/s)for silty to clayey ty e soils. This interval is characterized <br /> by generally moderate pore pressures. <br /> Hydrogeologic Unit 2 (HU2)-At-the top of the current-saturated zone, HU2 extends from <br /> 30 feet to,approximately 38°feet bsg and-pis comp sed of xsilty sand,to sand,type soils. <br /> Hydraulic conductivities for�HU2 typically vary betmeen 1x10"2 and 1x10.s cm/s. HU2 is <br /> characterized by generally lower pore pressures afid,js classified as a flow unit. <br /> Hydrogeologic Unit 3 (HU3)- HU3 extends from 38 feet-to approximately 45 feet bsg and <br /> is composed primarily of stiff;fine-grainedsoils, clalfey silts,silts,and,silty clays. Hydraulic <br /> conductivities for-these soil types-generally.-range :between 1 x10-4 and 1 x 10-8 cm/s for. <br /> clays, silts, and stiff;fine-grained soils. HU3 is characterized by varying pore pressures <br /> ranging between moderate and high and is identifi -as a confining.layer. <br /> Hydrogeologic Unit 4 (HU4)- HU4..extends from 45 feet bsg to approximately.50 feet bsg <br /> and is composed of silty sand to sand type soils.Hydraulic conductivities for HU4'generally <br /> range between 1 x 10-2 and 1 x 10-5 cm/s: HU4,,is aracterized by generally lower pore <br /> pressures and is classified as a flow unit: <br /> Hydrogeologic Unit-5 (HU5)- Extending from 50 fe4 t to approximately 70 feet bsg, HU5 is <br /> composed predominantly of stiff;fine-grained clay y silts, silty clays, and clay. A thin silty <br /> sand to sand type soil is encountered at,appro imately 58 to 62-feet,-bsg;.and has <br /> characteristically low hydraulic conductivity. Hy raulic conductivity generally ranges <br /> between 1x'10-5 and 1 x 10-'5 cm/s for-clays, silts and stiff, fine-grained soils. HU5 is <br /> characterized by varying pore pressures varying from moderate to very high, and is <br /> identified as a confining layer. <br /> Advanced CeoEnvironmental,Inc. <br />