Beneficial Uses of Tire Chips
Recycled Tires Can Be Used in Septic Systems

Most car owners probably do not think much about what happens to old tires after they are replaced.  You can see piles of old tires at landfills and in recycling yards, or illegally dumped in random places, especially along rural roadsides.   Scrap tires take up space and are breeding grounds for disease carrying mosquitoes and rodents.

Since 1985, states have been working to enact laws for managing scrap tires.  Today, 48 states have some sort of waste tire law.  Alaska and Delaware are the only states that do not.  Most states have focused on three areas:

• program management for scrap tires.
• creation of markets.
• stockpile abatement programs.

38 states ban whole tires from landfills, 35 states allow shredded tires to be placed in landfills, 11 states ban all scrap tires from landfills, 17 states allow processed tires to be placed into monofills, and 8 states have no landfill restrictions.   Markets for waste tires may include tire-derived fuel, playground cover, running surfaces, soil amendments, flooring and matting, roofing shingles, rod-fill applications, rubber-modified asphalt, and an alternative to gravel for septic system drain fields.

A number of states have approved the use of tire chips as aggregate in septic systems, including South Carolina (which was the first), Iowa, Arkansas, New Mexico, and Virginia. This past summer, DNREC joined in approving the use of tire chips as a substitute for aggregate that is normally used to construct the drain fields in septic systems.  This followed extensive groundwater testing by DNREC's Division of Water Resources at three demonstration septic systems utilizing the tire chips.   One of the first systems to have tire chips rather than gravel as the aggregate in the drain field was in Kent County, north of Milford.

Delaware has more than 3.5 million waste tires and produces another 750,000 annually.  Using tire chips in standard septic systems requires chips from over 1000 tires.  It all adds up to providing a viable recycling/reuse solution for a major waste issue.  A working group including experts from DNREC, DelDOT, Delaware Solid Waste Authority, the University of Delaware Civil Engineering Department, and the Delaware Auto and Truck Recyclers Association was formed by Senator David McBride to tackle the issue of scrap tires and to develop practical and widespread uses for recycled tire products.

Under DNREC's approval for use in septic systems, only tire chips from specific suppliers who have utilized a higher level of quality control and met minimum specifications established by DNREC can be used.  Tired chips can only be used in standard gravity type septic systems, pressure dosed full depth, and pressure dosed capping fill treatment and disposal systems.

Tire chips increase the drain field storage capacity by 30 percent because the void space between tires chips is greater then void space for gravel.  Drain field size is unaffected.   The cost of using tire chips rather than gravel in Delaware results in savings of up to 50%.  The actual amount depends on several variables including, how plentiful gravel is, freight costs (distance and weight), and distributor's selling price.  A cubic yard of gravel weighs about 2800 pounds, compared with only 800 pounds for a cubic yard of tire chips.  Where a ton of gravel is used for every seven feet of trench; a ton of tire chips will cover 21 feet.   Tire chips can save the homeowner money and improve the installer's margins.

For more information contact Bruce Bagley, DNREC Division of Water Resources, (302) 739-4762; or read this article in the National Small Flows Clearinghouse publication, Small Flows Quarterly, Fall 2003 issue .