TUCSON, Ariz.-A retired professor may have found a way to solve two environmental problems at once using scrap tires. This summer, Stuart Hoenig, professor emeritus with the University of Arizona, began installing scrap passenger tires in a gully near the Anvil Ranch outside Tucson to slow the rushing waters that cause massive erosion during the Southwest's rainy season.
Mr. Hoenig said on July 16 the tire dam he is building on an arroyo southwest of Tucson was only 60 percent complete when heavy rains a few days earlier tested the design.
``It held up pretty well,'' he said.
The performance surprised Mr. Hoenig since the dam's side fastenings were not complete and rocks were supposed to be put in the tires the previous weekend.
``There was 4 1/2 feet of water there,'' he said.
The retired electrical and mechanical engineering professor said the dam will use about 1,500 tires, filled with gravel and tied together with industrial-grade plastic straps.
The dam is about 30 feet long, 25 feet wide and 5 feet high, with another 4 feet buried to anchor the structure.
The dam is not supposed to retain the water. It is designed to slow water down and pool it long enough so that the sandy soil it carries is deposited behind the structure.
So far there is about 2 feet of sand-that's 2 feet less soil that will block the only main road west of Tucson during heavy rains, and 2 feet of land that rancher John King gets to keep at his Anvil Ranch.
Just as important to the state, the dam represents 1,500 fewer scrap tires sitting in heaps acting as a fire hazard or mosquito breeding grounds.
The scrap tires were provided by Pima County, which delivered them free of charge to the gully on Anvil Ranch.
Under state law, Arizona counties collect scrap tires and are required to find a way to recycle or discard them.
Pima County collected 490,000 scrap tires last year, according to Warren Whitehead, a recycling program coordinator with the county's Solid Waste Management Department.
The programs are financed from a 2-percent surcharge on new tires, not to exceed $2 per tire.
Mr. Hoenig said the dam already has sparked a lot of interest in the area.
``I think it can be useful in the entire Southwest,'' he said.
Part of the initial popularity may be the cost. A typical concrete dam runs about $40,000, Mr. Hoenig estimated.
He said Arizona built a couple of cement dams in arroyos but found the costs prohibitive.
According to Mr. Hoenig, the tire dam cost about $7,000-most of it for the gravel tire fill and for heavy equipment rental.
The tires were free, as was the labor. Pima County provided a crew of people on probation to perform the work.
Money for the project came from two companies: tire maker Goodyear gave the engineers $5,000; Phelps Dodge Copper Co. donated $2,000.
``We were interested in getting tests done (on a scrap tire dam),'' a Goodyear spokeswoman said. ``And the only way to test is to build one.''
Goodyear sees the idea as one part of the solution to the problem of scrap tires.