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19 May 2021 AdvancedGeo <br /> Project No. 21-6435 An Employee-Owned Company <br /> Page 4 of 14 <br /> ADDRESS: 26210 Thornton Road <br /> LOCATION: Adjacent property to North <br /> SEPTIC SYSTEM: 1) Permit date January 1953; installation of 500-gallon grease pit with <br /> one compartment; a filter trap consisting of three 4-foot-deep rock filled holes; and a 12- <br /> foot-deep seepage pit lined with brick. 2) Permit date June 1978; installation of 1,200- <br /> gallon concrete grease trap with two compartments. 3) Permit date March 1995; repair <br /> and addition of existing sewer line to septic tank. <br /> 3.6. PROPOSED MAXIMUM SEPTIC TANK USAGE ON SITE <br /> The current residences on the property have a total of six (6) bedrooms and utilize the <br /> existing septic system 365 days per year. The average and reasonable maximum usage <br /> of wastewater for six bedrooms is 100 gpd for the first bedroom and 50 gpd for each <br /> additional bedroom for a total of 350 gpd. <br /> The existing septic system will also service the proposed research facility. The hours of <br /> operations for the research facility will be between 9:00am and 5:00pm, Monday through <br /> Friday. The average and reasonable usage of 5 to 10 gpd per person is typical for an <br /> individual to the site setting, and a maximum usage of 15 to 20 gpd per person is typical <br /> for an individual to the site setting. The septic system will be utilized by the research <br /> facility 260 days per year by a maximum of six (6) full-time employees. The reasonable <br /> or maximum usage of wastewater for the facility is 20 gpd per person for a total of 120 <br /> gpd. <br /> 4.0. GROUNDWATER INFORMATION - REGIONAL HYDROGEOLOGY <br /> The Geologic Map of California, published in 1966 by the California Department of <br /> Conservation Division of Mines and Geology, shows the site area within the Great Valley <br /> Syncline (GVS), a large, elongate, northwest trending structural trough. The GVS is <br /> subdivided into two major divisions designated the Sacramento and San Joaquin Valleys, <br /> which have been filled to the present elevation with thick sequences of sediment ranging <br /> in age from Jurassic to present day, creating a nearly flat-lying alluvial plain extending <br /> from the Tehachapi Mountains in the south to the Klamath Mountains in the north. The <br /> western and eastern boundaries of this province are comprised of the California Coast <br /> Range and the Sierra Nevada, respectively. Geologically, the area around the property <br /> generally consists of Holocene-aged flood-basin deposits of clay, silt, and sand. Miocene <br /> to Holocene age-units are located in the surrounding area. <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 (1986). Most <br /> of the fresh groundwater in the Central Valley is contained in the post-Eocene-aged <br /> continental rocks and deposits and in the Holocene-aged river deposits consisting of <br /> gravel, sand, silt, and minor amounts of clay. In general, these geologic materials <br /> comprise a major widespread aquifer extending hundreds of feet deep and occasionally <br />