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SECTION 1 Introduction and Background This work plan describes well destruction activities that will be performed at the Koppel Stockton Terminal in Stockton, California (also called the Site). The Koppel Stockton Terminal is located west of Ventura Avenue, between the extensions of Hazelton Avenue and Sonora Street, and approximately 1 mile west-southwest of the Interstate 5/Highway 4 interchange.The locations of the Site monitoring wells and piezometers are displayed on Figure 1-1 (Figure 1-1 is presented at the end of this work plan). 1 .1 Site Background The Koppel Stockton Terminal is a former dry fertilizer warehouse and bagging facility with associated infrastructure.There is a warehouse at the Site where fertilizers and various agricultural products were temporarily stored,sold, and distributed from the 1950s through the 1990s.The warehouse is currently used to store fly ash. In 2000, phytoremediation was selected to be the remedial action for soil and groundwater at the Site to treat nitrogen-related constituents. It was implemented in accordance with the Remedial Action Plan (CH2M HILL, 2000)and subsequent conditional approval of the Remedial Action Plan from the Regional Water Quality Control Board, Central Valley Region (Water Board)(Water Board, 2000a). Additional remedial action is now being implemented in the former bagging plant area;a summary of this ongoing work was presented in the 2013 Annual Groundwater Monitoring Report(2013 Annual Report) (CH2M HILL, 2013a).The Request for No Further Action for Portions of the Koppel Stockton Terminal(CH2M HILL,2013b) was submitted to the Water Board to request concurrence that no further action is appropriate for all portions of the Site except the former bagging plant area.As described in a January 8,2014 letter,the Water Board agreed to consider no further action for the stormwater pond area (Water Board,2014). The original test grove,turnaround area,stormwater pond,former bagging plant,and north of warehouse planting locations are shown on Figure 1-1.Sampling of the monitoring wells and piezometers shown on Figure 1-1 has been performed since July 1996 to assess shallow and deep groundwater conditions and to evaluate whether past Site activities have affected local groundwater quality.Sampling data also help to establish trends in nitrate reduction due to phytoremediation at the Site.Water levels and groundwater quality have historically been monitored quarterly to assess local seasonal variations.As required by Monitoring and Reporting Program (MRP) No. R5-2004-0835 (Water Board, 2004b),groundwater samples are analyzed in a laboratory annually for nitrate as nitrogen (nitrate-N)and ammonia as nitrogen (ammonia- N).The Water Board approved suspending groundwater quality monitoring for monitoring wells KP-7S, KP- 7D,and KP-8S because of the low nitrogen concentrations at these wells (MRP No. R5-2004-0835;Water Board, 2007). Monitoring wells KP-7S, KP-7D,and KP-8S were destroyed in October 2013, as documented in the 2013 Annual Report(CH2M HILL, 2013a). As shown on Figure 1-1,seven shallow monitoring wells(KP-1R, KP-2, KP-3, KP-4, KP-9S, KP-125,and KP-10S-R),two deep monitoring wells (KP-4D and KP-6D), and five piezometers (TG-1,TG-2,TG-3,TG-4,and TG-5) are now used to monitor groundwater quality at and around the Koppel Stockton Terminal. 1 .2 Work Plan Objective The objective of this work plan is to describe the approach for destroying monitoring wells KP-4, KP-4D,and KP-6D,as requested by the Water Board(Water Board,2014). Water Board approval of this work plan is needed to proceed with well destruction and for compliance with the MRP (Water Board,2007). RDD/140100001(NLH494/.DO X) 1-1 ESIMB1311472MOD