Idaho Transportation

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Districts enter new era of design exceptions;
Practical Design will save time, money

Two projects scheduled to begin next year will do more than realign a highway and extend the width of travel lanes. They literally will help pave the way for a more streamlined approach to project design that bases decisions on the context in which the projects will fit.

Design exceptions are not new; they have been used when projects deviate from national or established department standards without compromising quality or safety. The one-size-fits-all approach to designing highway projects isn’t always practical or efficient.

This summer ITD Director Pam Lowe challenged districts to re-evaluate their projects and determine whether smaller or simpler will suffice. She encouraged districts to adopt the “Practical Design” concept that tailors project designs to their intended use and to expedite the process at the local level.

“Why build a Cadillac when a Chevy will do,” a Missouri Department of Transportation representative asked rhetorically when explaining Practical Design at the 2007 Project Development Conference in Boise.

All of the districts have been working on Practical Design plans and have submitted proposals that, when implemented, will save Idaho taxpayers millions of dollars, according to the director.

“The districts have all done an exceptional job pulling these plans together. This effort is going to be successful because of the work that the districts have done,” Lowe said.

“Most of the Practical Design changes do not need a design exception. However, for the ones that do, we have implemented a new process, where the district approves the design exception. For projects on the National Highway System or the interstate, the district will recommend the design exception, and Headquarters will forward the district’s recommendation onto FHWA.”

District 2 was the first to take advantage of the new philosophy when it forwarded two projects for design exceptions under Practical Design. The first will reconstruct and realign a one-mile segment of U.S. 95 north of Riggins – an area vulnerable to major rock slides. The other is a widening project planned for a 23-mile stretch of U.S. 12 east of Kooskia.

Planners forwarded the requests, along with detailed rational according to Practical Design guidelines, to Roadway Design at Headquarters for a cursory review. With minimal delay, the requests were sent to the Federal Highway Administration for design exception approval, explains District 2 Design Engineer Curtis Arnzen.

'You’ve got some very innovative people working in the districts who will come up with excellent
in-house designs..'

– Jim Carpenter, D-2 Engineer

Because there is little room for modifying the proposal under Practical Design, district staffs must be even more vigilant in preparing the projects, said District 2 Engineer Jim Carpenter. “It requires a heightened awareness – the need to be even more accurate and to make a good case,” he said.

Carpenter is a firm believer in the benefits of the Practical Design concept. They include:

  • Greater flexibility to tailor designs to the environment
  • Project streamlining without compromising quality of the end product
  • Cost savings that result from an expedited process, and
  • Ability to apply cost savings to other district projects that improve travel and safety

It makes sense to do as much of the work at the district level, Carpenter says.

“You’ve got some very innovative people working in the districts who will come up with excellent in-house designs.”

He offers District 2’s proposals as prime examples.

From submission to approval, the process took about six weeks; normally it occurs in a matter of months.

Syringa to Tumble Creek is a 23-mile project planned for the summer of 2008 that considers the unique aesthetics of the U.S. 12 corridor east of Kooskia. The route is part of the Northwest Passage National Scenic Byway System and follows a nationally designated wild and scenic waterway – the Clearwater River.

Owned by the U.S. Forest Service and managed by ITD under the jurisdiction of the Federal Highway Administration, the highway is clearly visible from a large number of river users, primarily rafters and kayakers. Narrow and windy, the road also presents challenges for drivers and winter maintenance.

ITD has agreed to add guardrail only when absolutely necessary for travel safety. It also will limit cuts and fills along the route and will add retaining structures on steep slopes, where appropriate, to contain falling rock.

Because of the horizontal alignment challenges and the narrow right-of-way, it would be extremely difficult to meet AASHTO’s standards for curves. Practical design and the exceptions granted will enable ITD to adjust the radius without compromising safety, Arnzen said.

The $15 million project will widen U.S. 12 from 24 to 28 feet where possible. Construction is expected to take two seasons. Ken Helm is the project manager while Doug Langley is the lead designer and Bud Henson is the transportation staff engineer assigned to the project, along with Arnzen.

The 210 Slide north of Riggins on U.S. 95 also faces unique design challenges. At the foot of a steep slope that is prone to rock slides, the highway will be realigned slightly to the west. Moving the centerline normally would have required the highway to meet current AASHTO width standards, but the adjacent Salmon River makes it difficult to conform to those standards.

ITD asked for, and received, a design exception under Practical Design to incorporate a five-foot shoulder, rather than the eight feet required by AASHTO standards. The $4.5 million project should be completed late next summer, Arnzen said. Kevin Dammon is the lead designer; Henson and Arnzen also helped with the in-district design.

“I am impressed with the District 2 design exception documentation,” Lowe said. “They are leading the way in demonstrating how quickly and efficiently ITD can work. We have shared what District 2 did with the other districts, and I expect we will have more in the future.”

“Again, the districts all have done a great job putting together their Practical Design plans.”



Published 11-09-07