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CDMCamp Dresser&McKee Inc. consulting One Walnut Creek Center , engineering 100 Pringle Avenue,Suite 300 con eroWalnut Creek,California 94596 operations TeL 925 933-2900 Fax:925 933.4174 October 1,2001 �� '�J t 5 pff Mr.Mike Infurna San Joaquin County Environmental Health Services 304 East Weber Avenue,third Floor Stockton,California 95201-4041 Subject: Work Plan to Abandon Piezometer B-1/PZ-1 at the Brookside Pump Station,Stockton,California CDM Project No. 2500-29248-Abandon Dear Mr. Infurna: On behalf of the City of Stockton,Camp Dresser&McKee Inc. (CDM),has prepared this Work Plan,in order to describe the activities involved in abandoning piezometer B-1/PZ- 1,at the Brookside Pump Station located in Stockton,California(Figure 1). The City of Stockton pians to replace a deteriorating wall on the south side of the existing Brookside Pump Station(Figure 2). The wall has failed due to corrosion of the reinforcing steel and degradation of the concrete. During construction of the new wall,temporary shoring will be needed in order to cast a new wall in front of the existing wall. The area in front of the south wall will be excavated to a depth of 30 feet below ground surface (bgs),to facilitate the temporary shoring and wall construction. Piezometer B-1/PZ-1 is within the area of proposed excavation,and extends approximately 12 feet below the lower limit of the proposed excavation(Figure 3). The piezometer was installed on April 13,2001 as part of a geotechnical engineering investigation at the south wall of the Brookside Pump Station. B1/PZ-1 will be abandoned in a manner that will prevent the migration of groundwater through the borehole annulus following excavation and construction of the new pump station south wall. Abandonment methods will be in accordance with State of California and San Joaquin County Environmental Health Division(SJCEHD) guidelines. Well abandonment tasks will consist of the following activities: ■ Coordinate with City of Stockton Public Works Department: CDM will coordinate access to the Brookside Pump Station with the City of Stockton. The work will be performed at a time when maintenance is not going on at the pump station. Underground utilities have previously(April 2001)been located and marked in the field by Underground Service Alert(USA) and the City of Stockton personnel.