Wednesday, November 14, 2018

Like some oil changes, I-90 ramp project in Spokane gets a bit more complicated

By Beth Bousley

Have you ever dropped off your car for an oil change and had it turn into a lengthier and more expensive car repair? Once in a while, our construction projects go the way of that oil change.

Take the westbound I-90 Hamilton on-ramp repair project in Spokane. When our contracted crews removed the overlay of the on-ramp, which was built in the early 1970s, they found that the bridge deck needed more repairs than originally anticipated. That meant the on-ramp could have been closed through the winter. Instead, we’re expediting the work to open one lane hopefully before the snow flies.

Why now?
Most bridges will last 75 years until they need to be replaced but since bridge decks get worn down from traffic and weather, they usually need rehabilitation after about 30-40 years to keep them strong and safe. That, along with the fact that it’s about ten times less expensive than replacing the entire structure, is why we are resurfacing the Hamilton on-ramp now.

No easy task
There’s lots involved in repairing an onramp and the Hamilton Avenue/I-90 project is no exception, with its own added complexities and time constraints:
Workers clean up a segment of roadway after hyro-demolition.
A close look at the damaged rebar
that needs to be chipped out
by hand to have appropriate
overlap with new rebar.

  • Like many structures, the Hamilton on-ramp needs to be repaired and resurfaced section by section to maintain its strength – and that involves time.
  • Deteriorated concrete in the overlay of an on-ramp can be removed using hydro-demolition or high-pressure water. This is a cost-effective way to remove old concrete, but it doesn’t work well when the temperatures drop below freezing. What we can’t get done now has to wait until the spring, because there’s no skating allowed on on-ramps!
  • After the overlay of an on-ramp is removed, new reinforcing steel – or rebar – is added to the old rebar to strengthen the structure. In the case of the Hamilton on-ramp, we found that the old rebar was more worn than anticipated, which meant more time was needed to strengthen the structure with additional new rebar.
  • Remaining concrete is chipped out by hand before the concrete is poured; a time intensive process. 
  • To get one lane open to traffic, we will be applying hot mix asphalt (HMA) as temporary pavement. HMA is hard to work with when temperatures drop since the colder the ground, the faster the asphalt loses its heat, making it almost impossible for it to stabilize. So we’re racing the clock (and the snow) to get the one lane paved and open.

The pink paint shows where workers hand-tie wire to secure old and new rebar.

Workers use hand tools to chip out the damaged rebar, marked by orange paint. Lots of orange paint equals lots of time.

Just like cars, it’s important to maintain our highways, bridges, and on-ramps to keep them in good repair for years to come.
Preparing to pour concrete on the new road deck.

Know before you go
We work hard to deliver high quality projects on time and budget and when projects change and delays happen, we still try to get travelers back on the road as quickly and safely as possible. The best advice is to know your alternate routes and check the construction scheduled to make sure you know the best way to go - and arrive safe.