Post Street Bridge’s historic arches will remain amid construction

The rising cost of steel worldwide and the historic value of concrete poured 100 years ago have led to an unexpected change in the project replacing the Post Street Bridge: Its historic arches will remain.

Dave McMullen, an engineer with the company replacing the bridge, told city officials last week the booming costs for steel made it difficult to replace the 333-foot span with an all-steel frame.

“It’s a real budgetary issue, going with steel right now,” said McMullen, a principal with KPFF Consulting Engineers.

Steel commodities reached a high of $744 in December 2017 and a record low of $273 in February 2016, according to TradingEconomics.com, a website that gathers economic data and stock market indexes. On Tuesday, they were priced at $625.

Good timing, considering the state Department of Archeology and Historic Preservation recently said the bridge was eligible for historic preservation. The state Department of Transportation, which is funneling federal money to the project, concurred. According to the National Historic Preservation Act, that means the city has to preserve the historic character of the bridge in some way to receive federal funding.

About $1.4 million in federal discretionary funding and $8 million in federal Surface Transportation Program funding is going to the project. The remaining cost of the $13.5 million project will be shouldered by the city utility department because of the bridge’s primary function supporting the city’s main sewer pipe.

McMullen said this week he couldn’t speak much about the project, which is in early stages, but reiterated the concerns he shared with the city.

“Those were the two major considerations,” he said. “Saving the arches was a consideration because it helped save on cost and met requirements for historic preservation.”

Megan Duvall, the city’s historic preservation officer, said there were some hiccups along the way, but it all worked out.

“The good news is that this isn’t a bad thing,” she said. “Since the city was planning on doing everything they could to preserve the arches, there really wasn’t an adverse effect on the bridge’s historic features. It works out fairly elegantly for everybody.”

Marlene Feist, the director of strategic development for the city’s public works and utilities department, said the city is glad the arches will be preserved.

“We just like the look,” she said. “We thought saving the arches makes a lot of sense, both aesthetically and the history of it.”

Though the current bridge has been standing for more than 100 years, it is far from the first span to cross the river at that point. That designation goes to “a man whose name is lost from the archives of the city’s engineer’s office,” according to a 1936 Spokane Daily Chronicle.

A wooden toll bridge was built in 1883. A few decades and a couple of bridges later, the current concrete crossing was built in 1917. It was widened in 1936 with a third arch to accommodate the growing auto traffic it carried, even as the widening did away with the streetcar lines it hosted for decades.

The wide bridge sufficed for 50 years, but as early as 1984, city engineers said the bridge needed to be replaced, even if its repair wasn’t yet critical.

Now, it’s critical to replace the bridge, which has had weight limits since 1995.

Mark Serbousek, the city’s bridge engineer, told City Council members at a presentation last week that many of the bridge’s arch columns have lost up to 20 percent of their load-bearing support. That has led engineers to reduce the weight limits on the bridge dating back several decades, requirements that Serbousek said frequently aren’t heeded.

“Any of the big trucks shouldn’t be going over this,” he said. “And we have a tough time keeping them off there. You see tour buses going over this all the time. We just can’t keep them off.”

A concrete design will allow the city to keep the historic arches on the bridge’s underbelly and reduce the costs of demolition while also addressing the major structural deficiencies in the bridge’s deck, he said. It will also make it easier for the city to leave the 54-inch sewer main that runs alongside the bridge’s supports to remain functional during construction.

The sewer pipe is the “the main interceptor that runs through town,” Feist said. “It carries the bulk of the sewage. Most of the sewage in the city comes to this one.”

Feist didn’t know how much sewage runs through the pipe in a day but estimated “better than half” of the 30 million to 34 million gallons of sewage treated daily at the city’s plant runs through the pipe.

“It’s a lot,” she said. “It is the main collection point.”

Current designs show the pipe tucked up beneath the bridge, out of sight and, perhaps, out of mind.