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PROJECT DESCRIPTION AND SCOPE OF WORK <br /> 400 E. Main Street, Stockton, California, Dewatering Project <br /> 16 May 2024 <br /> This document describes the proposed work associated with the installation and testing of <br /> an initial dewatering system at the site. The intent of the well installation and pump testing <br /> is to facilitate design of a more permanent dewatering system at the site to lower <br /> groundwater levels to below the lower-level parking garage floor, which is currently flooded <br /> with up to an inch of standing water. <br /> Location of Project Site (lure U <br /> 400 E. Main Street <br /> Stockton, California <br /> Current Site Use: <br /> The site is an eight-story professional office building with 2 below-ground parking levels and <br /> a street-level loading dock bay. The work is to be conducted in the lower level of the parking <br /> garage (level P2), which is currently not in use due to the presence of standing water. <br /> Hydro geology: <br /> Alluvial sediments. Dominated by clays and silts, discontinuous sand units of varying <br /> thickness, based on geologist's lithologic log and CPT logs collected to 50 feet bgs, plus one <br /> location to 90 feet bgs (under permit No. WP0044672), in the public right-of-way <br /> surrounding 400 E Main St. In addition, three groundwater monitoring wells have been <br /> installed in the public right-of-way adjoining the property (under permit No. WP0044673). <br /> • In January 2024, groundwater around the perimeter of the parking structure <br /> occurred approximately 1 to 2 feet above the P2 floor elevation. <br /> • Site groundwater quality: up to approximately 200 to 300 micrograms per liter (ug/L) <br /> of total chlorinated volatile organic compounds (VOCs) (tetrachloroethene [PCE], <br /> trichloroethene [TCE] and dichloroethene [DCE] isomers) have been reported in <br /> samples near the southwestern corner of 400 E. Main St. <br /> Well Installations <br /> Malcolm Drilling, a C-57 licensed drilling contractor, shall install test wells and piezometers <br /> in the of floor of the P2 garage, which is at an elevation of approximately 5.5 feet below <br /> mean sea level. <br /> Malcolm shall drill, core sample, construct, and develop: <br /> • Nine (9) piezometers (for water level measurement; see Figure 2 - Piezometer <br /> Diagram Vertical Profile) <br /> • Twenty (20) test wells (see Figure 3 - Phase I Test Well Diagram Vertical Profile) <br /> • Test well and piezometer locations are shown on Figure 4 <br /> 1 <br />