To build a good highway, start at the bottom
From District 6 newsletter, Six Bits
That's good advice for a career and good advice for building a highway, too. The foundation comes before the pavement. Substructure comes before superstructure.
But what of the ground beneath? Is it firm enough? Will it hold up the structure for its life span?
Enter five guys – not the restaurant, but Materials and the Materials Section.
The Right Materials
There’s no use building on “goo.”
Man of Steele
Each type of foundation must be designed with ground conditions in mind. The Materials Section determines the stability of subsurface rock and soils (“materials”) to identify foundation needs.
“Spread footings” or steel piles driven into bedrock may be necessary for bridges, while extra crushed rock (“base”) or gravel (“borrow”) may be necessary for roads.
If subsurface characteristics pose a risk that foundation adjustments can’t alleviate, Paul may recommend that offending soils be removed or somehow bridged, or that the proposed road or bridge be moved to a different location.
“If a proposed roadway traverses a landslide, we recommend rerouting it,” Paul says. Who better than Steele to ensure a solid foundation?
Plumbing the Depths
Shawn may start an investigation by looking for geologic indicators above ground such as “fault scarps,” which are steep cliffs formed by movement along one side of a fault. “Basalt,” “stratographic column,” “lava tubes,” “phi angle” roll off his
But Shawn is down to earth. A feet on-the-ground sort of guy. Awhile back, he led a statewide effort to record boring (drill) logs in a database for future reference.
“Material I drill today likely will be the same 100 years from now,” he observes.
Donning a lab apron, he goes to work. Technicians in Boise also test samples for rock strength, degradation rate and other properties.
Korby also tests samples of contractor test strips for proper blend and compaction of plant mix (asphalt and crushed rock) pavement.
“Korby’s expertise allowed us to be the first district to run its own test strips,” Paul announces.
Results Don’t Lie
Recommendations may fine-tune early estimates of the Planning and Project Management Section (2PM). Results beget results.
Into the Abyss
The region does not have extensive limestone deposits or salt domes, which can dissolve in water. Residents thus need not worry about sinkholes appearing to swallow buildings, vehicles and people.
Southeast Idaho is not bedeviled by such terrors. No unsettling settling here.
Over the Top
Depending on traffic, soils and climate, a good road may consist of 6 to 10 inches of pavement (6 inches of asphalt or 8 to 10 inches of concrete) on 8 inches of crushed rock (“base”) on 2.5 feet of gravel (“granular borrow”), creating a roadway about 3.5 feet deep.
Three and one-half feet of road depth generally gets you below the frost line, Shawn says. Insufficient road base of crushed rock and gravel invites upheaval, since water can’t drain. This water freezes, expands and pushes up pavement.
Then it melts, contracts and abandons the pavement, inviting slumps.
Fifty years ago, crews did not add enough crushed base and gravel under pavement, Shawn explains.
Meanwhile, Paul walks the pavement in search of cracks, rutting and patching – “stresses.”
Crews from ITD Headquarters run a falling-weight deflectometer across the road to determine base strength.
Paul and Shawn analyze findings to ascertain the type of footings required for a bridge and the type of base and pavement required for a road.
“Analyzing the data is fascinating,” Paul says.
“I try to propose the best solution possible, given material characteristics
Start to Finish
He randomly audits ITD and contractor testing of materials to ensure that correct procedures are followed and that accurate results are obtained.
“Results must be reliable,” he says. “Procedures need to be followed, and equipment must be properly calibrated. Federal funding depends on it.”
Testing testers is challenging, Paul explains.
“It is sensitive work that requires a seasoned professional – and one with tact.
“In some districts, IAI is the enemy. In District 6, Bruce maintains a good rapport with contractors. He’s there to help.”
Bruce established ITD’s first functional lab database, Paul explains. He sets the standard.
“Bruce and Korby are excellent technicians,” Paul states. “I would rather have them test my asphalt than anyone else in the state.”
Last Shall Be First
A “source” is a gravel pit.
District 6 has 90 sources.
“I search out, acquire, maintain, reclaim and dispose of state sources,” Eric says. That covers it. His job is (a) ensuring contractors reshape slopes of pits and remove garbage before leases expire, (b) making certain operators comply with all environmental regulations, and (c) helping cities, counties and private contractors obtain certification.
Source owners must recertify their sources every two years, Eric explains. Only certified sources qualify as sources of “material” for state and federal highway projects.
“He does a great job as our source manager and as a good assistant in road and bridge sampling,” Paul says.
The Right Stuff
It’s a strong team. All self-starters and proficient, with a sense of humor that makes work fun and engaging.
Discern water content and drainage. No dirt is faultless. Once you know about the subsurface, you can design the right foundation, be it road or bridge. It’s supportive work.
It takes five guys.