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` Monitoring Well Installation and Destruction Report City of Stockton RWCF Page 2 Modify the monitoring program to eliminate or relocate MW-4 because it did not provide a representative groundwater sample. Ir • Construct one new down gradient well east of the Secondary Treatment Plant to characterize nitrate migration in this area. L • Modify the sampling frequency to twice per year because no significant water quality impacts or temporal trends were observed. I Condor began conducting quarterly groundwater monitoring at the Site during the fourth quarter 2004. At Lr the request of Mr. Stephen Gittings(MUD), Condor prepared the Monitoring Well Installation Work Plan (MWIWP), dated April 27, 2005, to describe the construction of two additional monitoring wells. Conditional approval to the MWIWP was provided in an e-mail dated May 25, 2005, from Mr. George Lockwood of the Regional Water Board to Mr. Jeff Willett of Condor. Groundwater monitoring wells MW-17 and MW-18 were constructed on June 10, 2005. Monitoring well installation and development details for MW-17 and MW-18 are provided in Condor's Monitoring Well Installation Report, dated August 4 2005. Monitoring activities at MW4 were suspended as per the Regional Water Board MRP Order No.R5-2008- 0154, (Order) issued October 23,2008.At the request of Mr. Stephen Gittings of MUD, Condor prepared 6• the Work Plan and Time Schedule for Analyses of Background Groundwater Quality (Work Plan), dated March 11, 2009, to describe testing needed to characterize background groundwater quality conditions to evaluate compliance with Groundwater Limitations V.B.1.b and c of the Order. Work Plan activities L included the installation of four additional groundwater monitoring wells (MW1S, MW2S, and paired monitoring wells MW-19/19S)Monitoring wells MW-1S, MW-2S, and MW-19S were designed to allow for comparisons with monitoring well data from MW-IS (shallow background well). Deeper monitoring ` well MW-19 was designed to allow for comparisons with MW-19S and vertical trends. The Work Plan was approved in letter dated July 20,2009 from Ms. Gayleen Perreira of the Regional Water Board to Mr. Stephen Gittings (MUD) (Attachment B); authorization to proceed was provided in an e-mail dated April L 14, 2010 from Ms. Gayleen Perreira to Mr. Frank Girardi of SJCEHD. Groundwater monitoring wells MW-IS,MW-2S, and paired monitoring wells MW-19/19S were installed on April 22 and 23, 2010. Condor prepared the Monitoring Well Destruction Work Plan, dated August 4, 2009, for MW4 which 6 was subsequently approved in a letter dated August 17, 2009, to Mr. Stephen Gittings (MUD) from Ms. Gayleen Perreira of the Regional Water Board (Attachment B). Monitoring well MW-4 was properly destroyed on April 23, 2010 in accordance with San Joaquin County guidelines and State Bulletins 74-81 V and 74-90. 3.0 MONITORING WELL INSTALLATIONS, DEVELOPMENT,AND SURVEYING 10 This section includes a description of the Site preparation, drilling procedures, monitoring well installation procedures, well development, and surveying techniques. L 3.1 FIELD PREPARATION Condor submitted a monitoring well installation permit application to the SJCEHD and received the ` permit(Attachment B)prior to initiating fieldwork. The proposed monitoring well locations were marked with white paint and/or stakes and flagging and Underground Service Alert (USA)was notified 72 hours in advance of the fieldwork to locate and identify underground utilities in and near the work area. The SJCEHD was notified of the fieldwork schedule at least 72 hours in advance of the fieldwork. V s The Order replaces previously established Order No.R5-2002-0083 which expired on April 1,2007. V Ak4_ A V il� CONDOR