Laserfiche WebLink
02 March 2023 AdvancedGeo <br /> Project No. 23-7124 An Employee-Owned Company <br /> Page 5 of 14 <br /> These deposits are heterogeneous mix of generally poorly sorted clay, silt, sand, and <br /> gravel with some beds of claystone, siltstone, sandstone, and conglomerate. Most of the <br /> fresh groundwater in the Central Valley is contained in the post-Eocene-aged continental <br /> rocks and in the Holocene-aged River deposits consisting of gravel, sand, silt, and minor <br /> amounts of clay. In general, these geologic materials comprise a major widespread <br /> aquifer extending hundreds of feet deep and occasionally containing individual confining <br /> layers. The Modesto, Riverbank, Turlock Lake Formations and overlying recent alluvium <br /> are the principal source of domestic groundwater in the 13,500-square mile San Joaquin <br /> Valley Groundwater Basin (Basin 5-22). This basin is drained primarily by the San <br /> Joaquin River, which is approximately three miles west of the subject property. The <br /> nearest surface water feature to the site is the South San Joaquin Irrigation District Ditch, <br /> which is adjacent to the western property boundary of the subject property. <br /> 4.1. GROUNDWATER DESCRIPTION FOR THE GENERAL AREA <br /> According to the State of California Department of Water Resources (DWR) Sustainable <br /> Groundwater Management Act (SGMA) Data Viewer, Seasonal Report for Spring 2022, <br /> depth to groundwater at the site is approximately 25 to 30 feet below surface grade (bsg). <br /> Between 2013 and 2022, depth to groundwater at the site has fluctuated between <br /> approximately 15 and 35 feet bsg. Groundwater flow direction locally appears to be <br /> toward the northeast. Groundwater was not encountered in the 36-inch-deep percolation <br /> test hole advanced on 18 April 2019. <br /> 4.2. GROUNDWATER CONTAMINATION IN THE AREA OF THE SITE <br /> The immediately adjacent and outlying land use for the parcel is commercial/industrial, <br /> miscellaneous, residential, and agricultural. Potential groundwater contamination can <br /> occur from several sources including leaking underground storage tanks, septic systems, <br /> agricultural activities, dairies, and stormwater infiltration. <br /> A review of the California Department of Toxics and Substances Control (DTSC) <br /> EnviroStor Database and the California Geotracker Web site did not reveal any Leaking <br /> Underground Storage Tank (LUST) sites or other environmental investigations within <br /> 0.5 miles of the site, except for the UPRR — Lathrop Intermodal Facility located at <br /> 1000 East Roth Road and the Former Suprema Cheese Wastewater Pond Site located <br /> at 2455 Airport Way. The following is a brief summary of the investigations. <br /> • In November 2021, approximately 50 gallons of diesel were reportedly released <br /> from a locomotive engine compartment at the UPRR— Lathrop Intermodal Facility. <br /> Between November 2019 and October 2021, approximately 115 tons of diesel- <br /> impacted soil were excavated and removed from the property, several soil borings <br /> were advanced, and soil samples were collected to confirm removal of the <br /> impacted material. Diesel-impacted soil was left in place to the criteria established <br /> in the Underground Storage Tank Low Threat Closure Policy (LTCP). The Central <br />