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' Aquifer Testing Work Plan • Formerrth GroBroadway Facility 1905 North Broadway Avenue - ' Stockton,California Sierra-Pacific Project No. 94-055.05 ' Yellowish-brown silty sand(SM)was intercepted from about 52 to 65 bgs,and clayey-sand(SC)from about 65 to 70 bgs. The clayey-sand sequence is underlain by a thin layer of reddish-brown clay (CL). ' The documented presence of fertilizer and pesticide compounds at 70 feet bgs indicates that these clayey ' stratigraphic units are laterally discontinuous and thus incapable of stopping possible downward migration of surface waters containing elevated levels of pesticide or fertilizer compounds. ' 3.2 Ground Water ' The facility lies within the confines of the lower San Joaquin River drainage. The terrain is flat, and surface waters generally flow westward. Most surface runoff in the east Stockton area ultimately reaches the San Joaquin River during periods ofheavy precipitation. The northwest-oriented Stockton Diverting Canal lies approximately 500 feet northeast of the facility. The unlined diversion canal is a major ' ground-water recharge area. Water levels measured at the subject site have risen as much as 30 feet since 1993 due to ground water infiltration along the Stockton Diverting Canal. The site has four monitoring wells. Six other monitoring wells, located west of the subject site, are ' included in the monitoring well array. The well array has been monitored quarterly since May 1993. Ground water moves laterally within discontinuous sandy formations. Discontinuous beds (layers) of ' clayey sediment tend to restrict vertical(downward)migration of ground water. ' 3.3 Surface Water The facility lies within the lower San Joaquin River watershed. The nearest body of surface water to the ' site is the unlined Stockton Diverting Canal. The Stockton Diverting Canal has flowed continuously since early 1995. Surface water flowing northwest in the canal either percolates to the uppermost saturated zone or continues to flow to the lower San Joaquin River near the Port of Stockton. Levees which confine the Stockton Diverting Canal are well above the level of the PureGro Stockton facility. ' Storm water runoff from the site can not enter the canal. The City of Stockton maintains a network of ditches and storm drains which ultimately discharge into the San Joaquin River. Shallow drainage ' ditches are present along the west boundary of the facility on both sides of Report Avenue. SIERRA-PACIFIC GROUP 4