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Kennedy/Jenks Consultants Section 2: Facility Description Musco submitted a Report of Waste Discharge for the Class II Surface Impoundments (ROWD) to the RWQCB in January 2004 (Kennedy/Jenks 2004). The two onsite surface impoundments and associated monitoring systems were described in that ROWD. The description is provided below. 2.1 Description of Title 27 Impoundment System The Class II Surface Impoundments were designed as a joint effort between Kjeldsen-Sinnock and Associates (KSA)and J.H. Kleinfelder &Associates (Kleinfelder). The impoundments were built in two stages; Pond A constructed in 1986 and Pond B constructed in 1991. The surface impoundment design is illustrated in cross section on Figure 4. 2.2 Impoundment Design Both surface impoundments were constructed with a Hypalon synthetic inner liner, a compacted native clay outer liner, a leachate collection and recovery system (LCRS), and a vadose zone/lysimeter monitoring system (LMS). The general design of both impoundments consists of 2:1 side slopes, ridges and valleys along the bottom with perforated piping to facilitate collection of any leachate, and two LCRS sumps. A more detailed discussion of the design elements is included in the following subsections. 2.2.1 Lysimeter Monitoring System A LMS was installed beneath the ponds to monitor the unsaturated (vadose) zone of soil. Soil Moisture Equipment Co., Series 1920 lysimeters were installed below the valleys of the surface impoundment bottoms at depths of five feet and ten feet below the clay liner (Figure 3). The lysimeters are 12 inches long with a porous tip, PVC body, and polyethylene tubing extending to the surface to convey collected fluid. 2.2.2 Clay Liner Geotechnical studies of the Class II Surface Impoundment site indicated the presence of a 2'/2 to 3 feet thick dark grayish-brown clay layer located at the surface underlain by approximately 2 feet of tan silty-clay. When the ponds were excavated, the dark brown clay layer was stockpiled and processed for later installation as the outer clay liner of the ponds. The foundations for the embankments consist of the tan silty-clay and were tied into the native soil by excavating and backfilling a keyway. The embankments were then constructed in four-inch lifts with the dark clay placed on the inside of the embankment and the tan silty-clay placed on the outside. The dark clay was placed along the cut slopes all the way to the bottom of the impoundment excavation to form a clay liner with a minimum thickness of 24 inches on the side slopes. A three-foot layer of the dark clay was then placed in the bottom of the impoundment excavation on the compacted subgrade. The clay was graded into ridges and valleys, sloped at two percent Work Plan for Improved Detection Monitoring Program Page 3 Musco Family Olive Company, Tracy, California e�-erowWnngobON20104 ao_mu wlweW mp OsWw 27_dmpW dmum.mlreport text-09-26.doc