I-5 Chemawa Interchange Plan at OTC This Week

The Oregon Transportation Commission meets in Ashland this week, and on the consent calendar is the I-5 Chemawa/Lockhaven interchange.

Formally it's a "Resolution to amend the Oregon Highway Plan and adopt the Interstate 5 /Chemawa Road Interchange Area Management Plan and Alternate Mobility Targets."

This process has been percolating for several years now (see the December 2012 date on the plan, for example), and it's late to have much to say. The plan mostly concerns Keizer, also, and following the City of Keizer closely has generally been beyond our scope here. So this is "Johnny come lately" for sure. You may know much more about the plan.

Phases for the preferred alternative (click to enlarge)

From an urban standpoint, widening Lockhaven, extending Verda Lane and Tepper Drive, seem like the big pieces. Both these and the highway widening would induce trips, also, and should be seen as inconsistent with greenhouse and climate goals. But of course that's not how ODOT rolls, and probably not how Keizer rolls. The "auxiliary lanes" for the highway at least superficially resemble those in the I-5 Rose Quarter project, and it would be interesting also to learn if Chemawa School has any concerns about increased particulates.

In the plan is a brief assessment of sidewalks and bike lanes.

"lack connectivity" and "have a substandard design"

The project dovetails a little with Keizer's desire to extend the UGB north, but is generally outside of 20-year planning horizons (from 2012), apparently. This is probably more wish list than actual plan.

Some improvements recommended in this IAMP are not reasonably likely to be constructed within the 2031 planning horizon; as such, they are not planned improvements that can be relied upon to support subsequent land use changes. Therefore, ODOT has identified alternative mobility targets for these intersections to make their expected performance through 2031 consistent with the existing adopted land use plans. ODOT will seek adoption of these AMTs by the OTC and, when adopted, they will replace the existing AMTs that were adopted in 1997 as part of the City of Keizer’s development of the Chemawa Activity Center.

The total cost of the identified recommended improvements in the Chemawa IAMP, except for right-of-way costs, is estimated at approximately $134 million.

The planning level estimate is almost certainly bunkum, and is reasonable just to double it off the top to $250 million or thereabouts. The nearby I-5 Woodburn project started with a $40 million estimate, and ended at $70 million, for example. There is zero reason to trust these planning level estimates.

ODOT's recent history of cost overruns on big projects
via BikePortland and Joe Cortright

As a footnote, there is in the plan the first instance I have seen of a discussion of margins of error in traffic modeling. It is in a March 2019 addendum to the December 2012 plan:

The analysis methodology used by ODOT typically strives to achieve and level of accuracy of about plus or minus 5-10%, meaning that on any given weekday at any specifc location, traffic volumes could several percentage points higher or lower than those forecasted, depending on the nature of the facility being assessed. Higher volume, higher classification roads are expected to have lower margins of error than collector roads.

For the moment this is just something to register and file away.  We will return to it.