This summer crews will begin what could be a six-year project to repair DuPont’s buckling sidewalks and prevent more damage from thousands of improperly planted street trees.
The DuPont City Council unanimously approved spending $1.1 million of the city’s $2.5 million in stormwater utility reserve funds on the first phase of work, which will include the replacement of about 10 percent of the problem trees.
The whole project is expected to cost $2.2 million, far less than the city would have paid to replace the sidewalks. Instead, DuPont is using a piece of machinery called The Big Sidewalk Sucker that lifts concrete sidewalk panels, allowing crews to remove roots, install root barriers and replace the panels without destroying them.
“This is an $18 million problem,” City Administrator Ted Danek said. “Using the sidewalk sucker is going to save millions of dollars.”
The situation has been decades in the making. The culprits are sweetgum trees planted by Weyerhaeuser — the timber giant founded in Tacoma in 1900 — as it built the Northwest Landing planned community, beginning in the 1990s.
A hardwood tree, the sweetgum is common in the Southeast and Mexico. Its roots tend to spread horizontally and close to the surface if planted in soils that drain poorly. About 6,000 trees have been lifting and cracking the sidewalks as their roots stretch below.
City officials say the repair project — which will allow the city to save most of the mature trees — is a good use of stormwater funds because each tree diverts 860 to 2,380 gallons of water per year from the city’s street drains.
“Trees are remarkable to reducing stormwater,” Danek said.
Under city law, homeowners are required to cover the cost of maintaining the sidewalks in front of their home. But DuPont does not plan to seek reimbursement from homeowners, Danek said. City staff determined that homeowners were not liable for the damage the trees did to the sidewalks.
For the second phase of the project, which will cost another $1.1 million, the city might again tap stormwater funds, or it could draw from real estate excise taxes. Staff also might seek grants, according to city documents.
The City Council is expected to decide how to pay for the second phase in fall 2018. DuPont will continue to try to persuade Weyerhaeuser and the company that now owns its former real estate arm to chip in, Danek said.
Michael Simpson: 253-597-8670, @mlintonsimpson