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1 INTRODUCTION <br /> Dunn Environmental, Inc (DE) was retained by Nolte Associates and the City of <br /> Riverbank for the installation of two monitoring wells (MW-10 and MW-11) at the City <br /> of Riverbank Wastewater Treatment Plant (WWTP). The Monitoring Well Installation <br /> Work Plan dated March 2005 was approved by the Regional Water Quality Control <br /> Board (RWCQB). The RWQCB guidance for the preparation of a monitoring well <br /> installation work plan was used to develop the approved work plan. <br /> Riverbank Wastewater Treatment Plant is located north of the City of Riverbank in San <br /> Joaquin County, California. The WWTP site is located along Myer Road. The <br /> Stanislaus River is directly south of the site. Figure 1 provides the location of the site. <br /> The WWTP lies within Section 23 of Township 2 South Range 9 East of the Mount <br /> Diablo Baseline and Meridian. Wastewater treatment occurs in aerated lagoons (labeled <br /> T-1, T-2 and T-3), and disposal occurs within the percolation basins (labeled P-1 through <br /> P-4). <br /> i <br /> The City has converted the P-1 and P-2 ponds into lined treatment ponds. In order to <br /> monitor ground water quality beneath these ponds two monitoring wells (MW-10 and <br /> MW-11) were proposed for installation. This report presents the field and laboratory <br /> methods utilized. Activities under the DE scope included the oversight borehole <br /> drilling, installation of two monitoring wells, well development and initial sampling of <br /> newly installed monitoring wells. The approved work plan was used to guide all field <br /> activities. <br /> S <br /> 1.1 PHYSIOGRAPHIC AND GEOLOGIC SETTING <br /> l : <br /> + The City of Riverbank WWTP lies within the Great Central Valley, California. The <br /> i Central Valley is composed primarily of alluvial deposits from erosion of the Sierra <br /> Nevada Mountains located to the east and of the Coastal Ranges located to the west. <br /> Alluvium located east of the San Joaquin River is composed of high amounts of silica, <br /> volcanic, and granitic grains which reflect its origin from the igneous pluton of the <br /> Sierra Nevada Mountains. Alluvium located west of the San Joaquin River is composed <br /> of higher percentage of shale/clay and quartzite marine deposits which reflect its origin <br /> from the Coastal Ranges. In addition to the alluvial deposits that comprise majority of <br /> the geology within the Central Valley, lacustrine and marsh deposits also exist. <br /> City of Riverbank Wastewater Treatment Plant Monitoring Well Installation May 2006 <br /> DE Project No.:109-06 1 Rev.0 <br />