Laserfiche WebLink
Page 4,c,P,ARCO mirm mart <br /> 3.0 SITE CHARACTERIZATION <br /> 3.1 Site Description <br /> The site is located in a relatively flat commercial area one block south of the major intersection of <br /> Pacific Avenue and March Lane McDonald's Restaurant is located adjacent to the site on the <br /> north, and an A & W Root Beer restaurant is located on the south side of Rose Marie Lane A <br /> commercial/office building, owned by Mr Wyatt, is located immediately west of the site <br /> 3.2 Surface Drainage <br /> f <br /> The nearest surface drainage to the site is the Calaveras River, two blocks to the south Runoff <br /> from the site drains tb storm drains on Rose Marie Lane and Pacific Avenue <br /> 3.3 Site Hydrogeology <br /> The site is underlain by a relatively uniform 4-layer sequence of silt, downward-coarsening sand, <br />' consolidated silt, and poorly sorted, medium-grained sand The upper silt layer is 15 feet thick It <br /> has relatively low permeability and has been dry since site assessment began in 1991 <br /> Hydrocarbon concentrations in this layer are generally low <br />' <br /> Beginning at 15 feet the silt layer coarsens downward to sand The sand is slightly weathered and <br /> oxidized, but weathering decreases downward and the sand coarsens to gravelly sand at <br /> approximately 35 feet In most borings, a downward increase in moisture content was noted <br /> during drilling, and the gravel lens appears to be a zone of perched water Hydrocarbon <br />' concentrations reach a maximum in the middle portion of the sandy layer, and the maximum <br /> lateral extent of vadose-zone contamination appears to occur in this layer <br /> Between 35 and 65 feet, much of the site is underlain by an unweathered, consolidated silt bed <br /> that drills slowly and is nearly impermeable This layer is dry Downward, it appears to coarsen, <br />' and may grade into an underlying sand layer <br />' The principal aquifer at the site was penetrated at a depth of 65 feet This unit consists of poorly <br /> sorted medium-grained sand at the top, no samples have been obtained deeper in the aquifer and <br /> its total thickness or extent are not known <br /> 3.4 Contaminant r <br /> iy Characteristics <br />' The principal contaminant at the site is unleaded gasoline, which has high volatility and mobility in <br /> permeable soil and is moderately soluble in groundwater According to laboratory reports, the gas <br /> chromatographs of soil samples suggest that the gas is relatively young and not degraded The <br /> vertical and lateral extent of this contamination and the flow rate and vapor concentrations <br />