WashDOT Extends Pavement Life Through Patching and Sealing
Although departments of transportation (DOTs) know the importance of treating the right road at the right time with the right treatment, funding availability is often a deciding factor.
“Our pavement preservation funding is at 50% or less of what we actually need,” said Kim Schofield, state pavement engineer for Washington State DOT (WashDOT) during a recent webinar from the Transportation Research Board. “We were really struggling to fund everything we needed for rehabilitation projects.”
That’s why WashDOT started its one-touch policy in 2008, which is a plan to deliberately use proven pavement maintenance methods to extend the life cycle of the entire paving inventory for at least two years.
“We looked for cost effective alternatives to rehabilitating the entire roadway that could still hold that pavement together,” Schofield said, adding that the strategic preservation maintenance plan relies heavily on crack sealing, chip sealing and patching, performed either by WashDOT’s own maintenance forces or contractors.
For example, Schofield said, a 2-inch mill-and-fill patch may be all that’s needed to repair an area experiencing top-down cracking. “Instead of paying $150,000 per lane mile for a full mill-and-fill, we can patch in isolated locations to extend the entire pavement life if we don’t have a structural failure there,” she said. “Or, if the cracking isn’t so bad, we could even chip seal it instead to get some extended life from the pavement.”
This strategic preservation maintenance, Schofield said, grants pavements an extended life of anywhere from two to six years. WashDOT’s minimum pavement life extension, she added, is two years, “and everything we have been using is easily reaching that.”
For example, WashDOT has seen in its research and more than 10 years doing this type of work that crack sealing is extending pavement life a minimum of three to four years and sometimes as long as five or six years.
The Right Roads for Strategic Maintenance
To determine which pavements are most in need, WashDOT works closely with its regional materials engineers and pavement offices to look at its prioritization list, pavement distress data in its pavement management system, and the pavement itself.
“We also work hand in hand with our maintenance and roadway operations crews to make sure we’re doing what they’re seeing as issues,” Schofield said. “We’re not funding strategic preservation for reactive things, like a pothole here and a pothole there.” But, if there are enough potholes, and WashDOT thinks it can extend the life of that pavement, then the road becomes a candidate for strategic preservation.
It’s also a matter of cost, Schofield said. “What we do to gauge if [our strategic preservation treatments] are still cost-effective or not is figure out if they’re giving us an annualized cost that’s less than what we’d do for rehabilitation,” she added.
WashDOT’s data estimates an asphalt overlay lasts anywhere from 10 to 17 years and has a typical annualized cost of $18,000, while its strategic preservation maintenance extends pavement life by two to six years at typical annualized costs between $1,500 and $5,500.
However, those costs continue to increase. “Lately, we’ve been seeing our costs [for strategic preservation treatment] go up because the pavements are in such poor condition,” Schofield said. “But, even at these higher costs, we’re still seeing cheaper annualized costs of maintenance.”
WashDOT had a budget of $2.4 million for its one-touch policy when it began in 2008/2009. From 2021 to 2023, WashDOT has a budget of $30 million for strategic preservation.
“Part of the reason we’re spending that much money is because we don’t have enough money to do rehabilitation,” Schofield said. “Hopefully with the passage of IIJA, we will soon be able to switch this up a bit.”
Although WashDOT’s strategic preservation maintenance plan has proven to be a cost-effective method to extend pavement life while they wait for ample rehabilitation funding, the ultimate goal remains to rehabilitate the roads in need.