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soil moisture remaining with the vegetated cover soil profile can be estimated monthly by accounting for gains from precipitation and losses from evapotranspiration. Since leachate production at sanitary landfills is a major environmen- tal concern, every effort is made to minimize or eliminate it. This can be achieved by properly installing final cover, as modules are filled to final grade, in accordance with Subchapter 15 of the CAC. Table 2 projects no infiltration into the completed landfill with a properly constructed final cover, thus impeding leachate production. 4.6 BASE LINER AND LEACHATE CONTROL FACILITIES The North County Sanitary Landfill has been sited to meet the require- ments of Section 2533(b)(1) of Subchapter 15; thus, placing a single clay liner with permeability of 1 x 10-6 cm/sec or less is not planned. As presented in this report and the geologic and hydrogeo- logic report (see Appendix A), the following factors indicate that existing conditions will protect the ground water in the unlikely event that leachate is produced: - • Low average annual rainfall of 16.27 inches • Low -permeability (1 x 10-6 to 1 x 10-8 cm/sec) clay/silt deposits in the unsaturated zone underlying the site • Depth to ground water, which is historically greater than 40 to 50 feet and currently greater than 125 feet • Availability of on-site, low -permeability soils for use in construction of final cover that conforms to Sub- chapter 15 requirements (Section 2581[x]) • Existence of very good quality ground water underlying the site with no signs of existing contamination. This is supported by the results of the ground -water solid waste assessment test (SWAT) conducted at the existing Harney Lane Sanitary Landfill (approximately 2 miles away), which indicated no adverse effect= on the underly- ing ground water as a result of landfill operations. • Lack of nearby, permanent surface -water bodies PJ9 9390209A.00D 17