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1 11 1 1 u 0 13.0 CLOSURE AND POSTCLOSURE PLAN All closure and postclosure maintenance activities for the site will conform to an approved closure and postclosure maintenance plan. The plan will be prepared in accordance with RWQCB and recently adopted CWMB requirements. The RWQCB and the CWMB will be notified at least 180 days before beginning any partial or final closure activities, and within 30 days after their completion. All closure activities will be observed and documented by a registered civil engineer or a certified engineering geologist. Closure activities will be documented in a written report. This section describes the proposed closure and postclosure maintenance plan for the site. 13.1 LANDFILL SLOPES AND FINAL COVER Final landfill slopes will be constructed no steeper than 12 percent. Minimum fi- nal surface slopes of 3 percent (after settlement) will be used to provide sufficient slope for surface -water runoff. Drainage swales will be constructed and main- tained at a minimum 2 percent slope to divert surface drainage away from cov- ered wastes. The completed landfill will be covered with at least 4.5 feet of cover material con- sisting of the following: • A minimum 24 -inch foundation layer of compacted soil placed over waste fill • A minimum 12 -inch layer of clayey soil compacted to achieve a hy- draulic conductivity of 1 x 10-6 cm/sec or less, placed over the foundation layer A minimum 18 -inch layer of vegetative cover soil placed over the low -permeability layer The vegetative soil cover will be fertilized, as necessary, and seeded with mod- erately rooted. erosion -resistant vegetation native to the surrounding area. Veg- etation that will germinate without irrigation and require minimum maintenance will be selected. Final cover slope and drainage details are shown on Drawing 4. PJ9 9390219A.00W 53 Rev. 0 July 19, 1989