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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- t 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[a] ) • 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 effects on the underly- ing ground water as a result of landfill operations. • Lack of nearby, permanent surface-water bodies PJ9 9390209A.00D 17 ' Emofl Associates