Bridge opening on busy Pierce County trail delayed due to unstable soil

The replacement of a major bridge on the Foothills Trail will be delayed by another two to three months, Pierce County officials announced Tuesday.

Construction to replace the Spiketon Ditch Bridge — located on a section of the Foothills Trail between South Prairie and Buckley — began on April 7. The county had previously expected to open the bridge for public use by July 1.

Ted Yoder, the bridge’s project manager with Pierce County, told The News Tribune Wednesday that crews discovered unstable soil on the north side of the bridge location while drilling for the structure’s footing on April 28. He said the bridge is now expected to open in August or September, but could not yet give an exact date.

Additional geotechnical drilling on May 6 and analysis of the new samples confirmed the project would need new reviews of permit changes and structural plans before continuing, Yoder added. The unstable soil could pose a safety issue if unaddressed, he said.

“It’s a much more cumbersome and involved process than originally expected, but it means the structure will be a lot safer,” he said.

The bridge has been closed since November 2023 and was demolished in June following an inspection that found damage to the structure’s top chord and an engineering report that found extensive pest and water damage. There is no detour available around the missing bridge, meaning the closure has blocked visitors from crossing that section of the Foothills Trail for 18 months.

Permit changes will take about three to four weeks to submit, but should be approved within a couple days after that, Yoder said, adding that multiple structural engineers will review and sign off on the changes.

“After those changes, then we should be able to remobilize and get rolling on this,” Yoder said.

The additional construction and delays will incur additional costs in the tens of thousands of dollars to the $1.4 million project, Yoder said, although he added he could not yet give specific estimates without further review from structural engineers.

Yoder said although the project had drilled test holes during the permitting process that indicated stable soil samples, once the larger excavation began for the north footing of the bridge, the soil was found to be unstable in other areas. However, the south side of the bridge’s footing has not faced the same issue and is ready to pour, he added.

“We had done geotechnical drilling but had hit good soils, but unfortunately, you don’t know until you start digging down,” he said.

Previously, the new Spiketon Ditch Bridge was expected to require excavation of only about eight feet into the ground, Yoder said, but with the new findings, some areas of the footing will have to reach up to 25 feet into the ground.

Yoder said materials for the bridge’s main structure were expected to arrive last week but were put on hold following the soil discovery. That delivery will be scheduled to come in within seven days after the concrete footing is poured — then the bridge should take about three weeks to install, giving the concrete a full 28 days to cure during that process, Yoder added.

The main bridge’s design will be unaffected by the new footing plans, he said.

This story was originally published May 29, 2025 at 11:00 AM.