ARCHIVED REPORTS_[REV] MAY & JULY 2014 RCSI

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2-14 permeability of both these soils are low, the available water-holding capacity is moderate, the shrink-swell potential is high, and the water erosion potentials are low. The general water bearing characteristics of the surface soils, separated into clay, silt, and sand components are presented in Table 1. Typical uses of these soil types include irrigated cropland, orchards, vineyards, and sometimes irrigated pasture and urban development. (2) The Forward site is located in the San Joaquin hydrologic basin. Based on groundwater elevation contours published by the San Joaquin County Flood Control and Water Conservation District, the regional groundwater in the vicinity of the site is now t yp ically 10 to 25 feet below mean sea level (bmsl)was 20 to 30 feet NGVD (approximately 60 to 70 feet below ground surface (:!lg§gbs)) and appeared to be flow §ffig to the north-northeast in Spring, 1990. The sediments have been divided into three large groups based on gross lithology and pervasive distinctions in color. Although several strata can be recognized in the logs, for purposes of this report they were grouped into the following three larger groups: Group A Surface to approximately 28 to 40 feet below ground ; highly interbedded sandy silt, clayey silt, silt, and clay. A few layers of sand are present. Generally sands are fine grained. Most of the sediments have an oxidized appearance, showing an orange brown color. Group B Top -approximately 28 to 40 feet deep to. gQottom ~-_approximately 55 to 75 feet deep (25 to 35 feet thick); interbedded sand, silty sand, silt, and a little clay. Sands are fine grained. Overall, this layer is a little sandier than Group A. Sediments are distinctly less oxidized than Group Ai showing a grey brown color. Group C Top -approximately 55 to 75 feet deep .. ..-B...,Qottom to 10'o\'est avai lable data (approximately 110 feet deep k Sediments dominated by saM, fine:--to: medium grained sand ; some coarse grained or gravelly layers. A few layers of silt and clay material occur. Color is generally light brown to yellow brown. Grains are large enough to assess and conclude that the sediments appear to be granitic in origin. Surface Soils. The surface soils are mainly composed of two soil types typical of Victor Formation sediments. The two soils, as mapped by the U. S. Soil Conservation Service, are known as Clear Lake clay (CL) and Jacktone clay (ST). These soils are similar in composition ... ; they 'Nere being formed from alluvium. The Jacktone and Clear Lake cla ys are equally pervasive at the site with the Clear Lake clay more prevalent in the northern and southern portions of the site and the Jacktone clay more prevalent through the middle portion. These soils are sub ject to rare flooding in years of abnormally high rainfall over short durations. The most widespread soil type on the site is the Jacktone clay (ST), which covers the nearly flat terrain approximately 100 to 200 feet from the South Fork. Typically, this soi l type is found on 0 to 2 percent slopes forming a moderately deep hardpan of somewhat poorly drained soil made up of generally dark gray clay about 2 inches thick, underlain by light gray clay loam, followed by hardpan of 3 inches. Permeability is low, the available water-holding capacity is moderate, the shrink-swell potential is high, water may be perched on top of the Forward Compostlng Facility SWT Engineering Report of Composting Site Information -May 2014 z:\projects \allied waste \forwardVesource recovery facility\5 yr permit rvw 2013-14Vcsi 2014\text\sec 2 -revtr.d oc