SU0006850 SSCRPT - Laserfiche WebLink

Home Browse Search

LFR Inc. 6.1.4 Subsurface Features The Site is located within the Great Valley Geomorphic Province, an alluvial plain about 50 miles wide and 400 miles long in the central part of California. The Great Valley is an asymmetrical synclinal trough with its axis off center to the west. Sediments have been deposited in this trough almost continuously since the Jurassic period (about 160 million years ago). Lithology beneath the Great Valley is composed of alluvial sediments known as the Great Valley Sequence, comprised of interbedded sedimentary units. These sedimentary units are composed primarily of eroded rock from the Sierra Nevada Mountains. The syncline was previously underwater; therefore, some of the sediments are of marine origin. The thickness of the Great Valley Sequence exceeds 25,000 feet in some areas. The lowland of the Great Valley is referred to the Central Valley consisting of the northern Sacramento Valley and the southern San Joaquin Valley. The Site lies within the San Joaquin Valley. Generally, near surface lithology in the Central Valley is comprised of unconsolidated Pleistocene and recent sediments (Norris &Webb, 1976). According to the EDR report, the surficial soils at the Site are part of the Jacktone Soil Series. The Jacktone Soil Series is characterized as somewhat poorly drained clay loams with slow infiltration rates and low hydraulic conductivity. The Jacktone Soil Series are reported to have horizons that impede downward movement of water. Therefore, wet soil is found high in the soil profile. According to EDR, Jacktone soil meets the requirements for a hydric soil. A hydric soil is defined as a soil that forms under conditions of saturation, flooding, or ponding with water retention long enough to develop anaerobic conditions. A hydric soil is one of three required criteria for a wetland designation. The other two required criteria include hydrophilic vegetation and hydrology criteria. It should be noted that LFR has not drilled soil borings at the Site, and the local and regional geologic conditions described herein are based solely on available literature regarding the area. 6.1.5 Groundwater Characterization Based on surface topography as shown on the USGS 7.5-Minute Series Topographic Map of the Lodi South, California Quadrangle (USGS 1968 photorevised 1976), groundwater in the Site vicinity is anticipated to flow to the southwest. Groundwater at the Site varies in depth as a result of seasonal variations and municipal and agricultural withdrawal. The database report prepared by EDR listed several wells located within a 1-mile radius of the Site. Depth-to-water measurements reported in these wells ranged from 29 feet below ground surface (bgs) in 1961 to 59.20 feet bgs in 1974. Based on information obtained from the San Joaquin County Environmental Health Department, the average depth to groundwater in the site vicinity is between 35 and 40 feet bgs. 003-0924600_LowerSeer .I.Rwd_H.Ho=s_Pha I ESA:cIb Page 15