To encourage the reuse of waste tires, the California Department of Resources, Recycling, and Recovery (CalRecycle) has sponsored grants for the use of tire-derived aggregates (TDA). TDA is manufactured from waste tires by shredding into pieces. In recent years, DWMR has utilized TDA for landfill construction purposes, thereby creating a re-use market for waste tires. In these landfill construction projects, DWMR typically uses 3-inch TDA (Type A) or 6-inch TDA (Type B). Quantities of TDA can be expressed in “passenger tire equivalents" (PTE) to estimate the number of tires reused. CalRecycle has sponsored DWMR's use of TDA through the following grants:
DWMR Grant History
| Grant Period | Amount | TDA Quantity | PTE |
| 2012-2013 | $259,223 | 2,602 tons | 260,200 tires |
| 2015-2016 | $49,004 | 474 tons | 47,400 tires |
| 2018-2019 | $77,220 | 6,777 tons | 677,700 tires |
The County uses TDA for two purposes at the County-owned and -operated Kiefer Landfill (KLF). These uses apply to horizontal landfill gas (LFG) collection trenches and a component of the winterized access roads and tipping pads. TDA provides a permeable media for LFG collection trenches installed in the waste mass. Utilizing piping under vacuum, LFG is collected and transported to an onsite LFG-to-energy plant to produce electricity. Also, due to the unstable foundation characteristics of landfilled refuse, the access roads and tipping pads constructed each year on the landfill must be reinforced to withstand heavy traffic loading throughout the wet season on an elastic subgrade. TDA provides one component of the foundation for these roads and pads. As the landfill configuration changes over time, much of the materials used for temporary roads and pads are removed, and the materials replaced on new roads.
