ARCHIVED REPORTS XR0010966 - Laserfiche WebLink

Home Browse Search

gcokgicaI Teclu a fac. Page 4 City of Escalon Project No.: 750.2 May 16,2005 2.3 Site-specific Hydrogeology 2.3.1 Lithology and Soil Characteristics • Top two feet of the site appears to be backfill materials comprised of gravel and sand PP P • Brown, poorly sorted, sand from 5 to 10 feet bgs, which overlies a dry, light brown, silt f unit between 10 and 20 feet bgs L • The geology from 20 to 30 feet bgs consists of various layers of grey colored silt and sand • The predominant geology between 30 and 45 feet bgs is comprised of a buff color, poorly sorted sand containing some clasts greater than 1 centimeter in size • Grey silt and sandy silt layers were noted between 43.5 and 50 feet bgs t 1 • Sand characterizes the 50 to 55 foot interval —buff and well sorted at 50 feet bgs grading Ldown to brown and poorly sorted at 55 feet bgs A site map showing the locations of streets, structures, wells, and other site-related details is attached as Figure 2. 2.3.2 Groundwater Bearing and Gradient C Groundwater bearing and gradient data has been collected since April of 2000. The historical groundwater information for the site is as follows: • Average groundwater elevation is 56.71.AMSL L,'✓ • Average depth to groundwater is 62.67 feet below grade • Average bearing is N73°W • Average gradient is 0.0019 ft/ft 2.3.3 Vertical Groundwater Gradient The vertical gradient has been calculated using the MW-1/MW-101 pair. The vertical gradient is generally negative (a downward direction). However, it has been insignificant due to a near zero head difference between MW-1 and MW-101. The historical average vertical L groundwater gradient is—0.0039 ft/ft. 2.3.4 Average Groundwater Velocity The lithology at the COE site will be divided into four general layers for the purposes of calculating the average horizontal groundwater velocity(AHGV). o Layer 1 consists of silts and sands from 5-to 30-feet bgs o Layer 2 is primarily sand with some larger clasts from 30- to 45-feet bgs o Layer 3 is primarily silt from 45- to 50-feet bgs o Layer 4 is primarily sand from 50-to 70-feet bgs.