ARCHIVED REPORTS XR0012552 - Laserfiche WebLink

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hof 3-2 The site is located in the northwestern portion of the city of Stockton. The site is underlain by alluvial sediments, and the topography, shown on Figure 3-1, is relatively flat. The shallow -- groundwat" ,r of concern in this investigation occurs at depths of 11 to 13 feet below ground surface in the Riverbank Formation, a floodplain deposit of clay interbedded with discontinuous sand lenses. Most water wells in the Stockton area draw groundwater from the more continuous interbedded sands clays of the Laguna Formation at depths greater than 150 feet. ;LA At present, the groundwater at the site has a very flat natural gradient of approximately 0.003 foot per mile, with groundwater elevations varying less than 0.0005 foot across the site. Without ti.. the imposed stress of the site recovery well, the shallow groundwater flows generally to the east-northeast. A water well survey conducted by EMCON shows that nine water wells exist within a 1--mile radius of the site (Figure 3-2) , three of which lie within 1/2--mile of the site. None of these wells are drawing water from the shallow aquifer at the site. (EMCON's report is included in Appendix A, which includes available wells logs in its Appendix A.) Four of the nine wells in the site vicinity are used for drinking water. The nearest well is City Municipal Utility District (City) Well 20M2 located approximately 530 feet north of the site near the northeast corner of Benjamin Holt Drive and Plymouth Road. This well is perforated Erom 295 to 315 and 333 to 353 feet below the ground and has a san°tary surface seal to 55 feet below the ground surface in a clay interval that continues to a depth of 72 feet. The City - well is located in Swenson Park Golf Course, about 1/2--mile northeast of the site. This is a discontinuously perforated well from 85 to 403 feet below the ground level. information on the sanitary seal of this well was unavailable. The San Joaquin County Flood Control District (District) Well 20L1 is located 1/2-mile southeast of the site on Belmont Place. This well is perforated from 272 to 328 feet below the ground .and has a sanitary seal to 35 feet below the surface. The fourth drinking water well (26J1) , also run by the District, is located approximately l mile west of the site. No completion inEormation .was available on this well. The other five water supply wells within 1 mile of the site are r. used for ornamental and irrigation purposes. The four private wells (19L1, 19P1, 19P2, and 3081) , located in the Lincoln Village West area 3/4-mile west of the site, are used to fill an artificial lake during the summer. The Lincoln Village wells are perforated from between 108 to 190 feet below the surface. The Pacific Gas and Electric Company well (21M1) , approximately 1 mile south of the site, is used for lawn irrigation. `5