Weather is a little odd here in Pima County.
Summer brings blistering heat, along with wild swings between daytime highs and nighttime lows. On the heels of the hottest month, the region is pummeled by weeks of monsoon downpours and accompanying hail, flash floods and gale-force winds. And while heat is what Tucson is known for, below-freezing temperatures are not uncommon in the winter.
All this is to say that our pavement puts up with things that roadways in climatically gentler parts of the country donβt have to endure.
Nevertheless, much of the data that exists on different roadway materials is based on national numbers, which may be out of step with Tucsonβs reality.
Thus, the county has set out an asphalt experiment southwest of Tucson on San Joaquin Road, which runs northwest from the Ajo Highway near the Tucson Trap & Skeet Club. It was selected in part for its consistent traffic levels.
This summer, the county will have a dozen 1,000-foot segments installed, each with a different treatment, asphalt mix or other repair. Those include six inches of roller-compacted concrete, a rubberized chip seal over the current roadway, Kevlar-like fibers mixed in with the standard PAG 2 asphaltic concrete mix and even the local Green Asphalt product this column explored several weeks ago.
The second half of the 4.3-mile stretch will get a regular 2-inch mill and fill.
Some of those treatments β like chip-sealing β are significantly cheaper out of the gate. Others, like the roller-compacted concrete, can be more expensive at first, but much cheaper over the long term due to lower maintenance costs.
The data gleaned from San Joaquin Road will allow the county to know how all of them hold up in Tucsonβs challenging climate.
βItβs not just looking for alternatives,β said Yves Khawam, the countyβs chief deputy transportation director. βItβs comparing ... life-cycle costing of treatments across time.β
With a lot of uncertainty surrounding transportation funding, the county is also hoping to have a better sense of the relative merits of cheaper alternatives, βthat we may have to go if a sales tax isnβt approved,β Khawam said, referencing the shaky prospects of such a measure.
The county likely wonβt have to wait long to get actionable data from the experiment.
There will be regular testing of the segments, the results of which can be compared to national data on the different materials.
The experiment will be paid for with a portion of $16 million in 1997 HURF bonds recently reallocated by the Board of Supervisors for arterial and collector road repair. The work was estimated to cost roughly $930,000, but those estimates were based on doing a standard 2-inch mill and fill the length of the road. Khawam said the experimental portions make it difficult to provide a good cost estimate, but several of the treatments are significantly cheaper than standard ones, and there is the possibility of some materials donations.
DOWN THE ROAD
- Park Avenue north of Grant Road will be closed Monday to accommodate the removal of a water line. That means no through traffic on Park at Grant, and no westbound right turns or eastbound left turns at the intersection. The work will be take place between 6 a.m. and 5 p.m.
- There will be some lane and ramp closures this week on Interstate 10 near Avra Valley Road to allow for guardrail repairs.
On Monday, westbound I-10 will be reduced to two lanes from 7 a.m. to noon. The eastbound Avra Valley Road onramp will be closed from 9 a.m. to noon on Tuesday.
Eastbound I-10 will be reduced to two lanes from 9 a.m. to noon on Tuesday and from 9 a.m. to 1 p.m. Wednesday.
