This Summer, SLO's Higuera Street Project Opens Up a Creek and a History
BY STEVEN T. JONES
Mention the Higuera Street Bridge and a fair number of San Luis Obispo residents will scratch their heads and wonder just what the hell you're talking about. A bridge? On Higuera Street?
They'll picture Higuera Street, that one-way lifeline of the downtown, searching with their mind's eye for a bridge along that familiar urban terrain.
You might even get an "Oh, OK" or mistaken flicker of recognition when their brains have made it almost to the freeway and cross San Luis Obispo Creek over the Marsh Street Bridge.
Longtime locals know about the Higuera Street Bridge, our hidden bridge, the one that looks like any city street but functions more like a tunnel, guiding San Luis Creek under the downtown before it cheerfully emerges into Mission Plaza.
You really can't blame the newcomers for their ignorance, for even city officials have long tried to ignore our hidden bridge, contributing to its current dilapidated condition with girders rusted through and portions of the deck ready to collapse.
But this summer, when construction crews remove the 450-foot-long deck between Court Street and the front of Thai Classic restaurant, our hidden bridge will be impossible to ignore.
Although city officials have pledged to minimize the impacts of the project to downtown businesses–keeping at least two lanes of traffic open during business hours, using an expensive precast concrete deck to speed up the project, giving $25,000 to the Downtown Association for project-related advertising–there will still be impacts.
Yet any problems caused by the $4.5 million project, which is set to begin June 1 and end Nov. 1, are certainly better than what engineers and regulators say are the very real potential consequences of doing nothing: The weakened deck alongside Mo's Smokehouse BBQ could give way or, during a moderate-to-strong earthquake, entire sections of the bridge could collapse.
"If we had a massive quake today, there is a chance the walls would give way," said Barbara Lynch, the city's civil engineer who is heading the project.
"If there were a moderate seismic event, you could have problems throughout the bridge because of the unreinforced masonry walls," said Ron Rivett of Martin & Kane Inc., the Roseville-based bridge consulting firm hired by the city for the project.
Even when the project is completed, those same old granite-and-mortar walls will continue to serve as the foundation for our hidden bridge.
"Confining Our Riotous Nuisance"
Back when Marsh Street used to be a soggy marsh, back before the coming of the railroad brought prosperity and a building boom to sleepy downtown San Luis Obispo, San Luis Creek was the bane of downtown property owners.
City leaders set out to tame the wild and unpredictable San Luis in the early 1890s with the construction of tall granite-and-mortar walls along the creek's banks.
On Nov. 4, 1892, the Tribune wrote of the "interested crowd gathered around the busy workmen who, under the skillful direction of the contractors, Messrs. Healy, Tibbets & Co. of San Francisco, are finishing up the job of confining our riotous nuisance of a creek within its splendid granite walls."
"Without any fuss or parade they have quietly proceeded and produced solid and substantial results which will be a monument to their skill long after this generation shall have been forgotten. The outcome will be solid iron bridges on Osos, Court and Morro streets of an almost imperishable character, and the entire transforming of all that section of the city."
The account proved somewhat prophetic. Although the old iron bridges didn't last long, the walls proved solid enough to last throughout the 20th century, and with a little help this summer they are likely to make it through this century and beyond.
But it wasn't the trio of iron bridges that transformed that section of the city as much as the steel and concrete decks that were built around 1910, sealing the waters of the San Luis away from public sight and consciousness.
Except for those who ponder the emergence of San Luis Creek from under Chorro Street into Mission Plaza, or for male visitors to McCarthy's Irish Pub who can peer through the steel grate of the restroom window to see the creek daylight near Morro Street, most people hardly realize the creek is there.
Reports on the bridge indicate that a lack of regular painting of the steel girders contributed to their deterioration, yet mostly this is just an old bridge made of materials with a finite life that was just going to have to be replaced at some point.
"California doesn't have many steel bridges," Rivett said. "The only thing you can have happen with steel is deterioration. This has definitely lived out its life."
Discovering Deterioration
The beginning of the end for the existing Higuera Street Bridge came in November 1993 when the California Department of Transportation wrote a letter to the city prohibiting heavy trucks from using the bridge and indicating that it would have to be replaced.
Caltrans made that discovery as part of its federally mandated bridge inspection role. Because of a combination of aging infrastructure, more heavy truck traffic, and growing knowledge of seismic safety, the federal government in the 1970s created a nationwide bridge inspection program.
The first piece came in the early-’70s when the federal government required each state's department of transportation to do biennial inspections of all state bridges.
In 1978, that inspection mandate was extended to include local bridges, and almost all local jurisdictions in California have Caltrans do their bridge inspections. Caltrans now inspects about 12,000 state bridges and another 12,000 local bridges every two years.
"We didn't get into the local bridge inspection business until 1979," said Tom Rutt, the Caltrans division chief in charge of the Structure Maintenance and Investigation Division.
Although the Higuera Street Bridge had been showing signs of deterioration for years, Rutt said the agency's concern was heightened in 1993 when San Luis Obispo finally gave Caltrans the original bridge plans, showing the deck wasn't connected to the walls and the walls weren't connected to the bedrock.
In previous years Caltrans had signed off on the bridge, assuming that those connections were there, Rutt said, even though that couldn't be verified by visual inspection.
"We had made some assumptions about that bridge," Rutt said. "But when we got the as-built plans, we learned the deck was just laid on top of the girders without any attachment."
While the unreinforced masonry walls supporting the Higuera Street Bridge could cause the most catastrophic problems in a serious earthquake, it is the weaknesses in the deck that have created an urgency for the project.
"It's deteriorating and will continue to deteriorate until it won't be able to handle even the loads it's posted for," Rutt said.
The weakest spot is in the Court Street parking lot right next to Mo's Smokehouse BBQ, where the supporting beam has completely rusted through and the city was forced to remove a planter and cordon the area off from parking.
"Conceivably, that area could fail," Lynch said. "I don't know how many football players jumping up and down it would take."
Yet enough pressure could definitely break through a slab of concrete that is just five inches thick at the site–a slab now unsupported by girders–and create a dangerous 20-foot fall into the creek below.
Another weak spot in the deck is the sidewalk area right in front of Woodstock's Pizzeria. Lynch said a failure there probably couldn't be caused by pedestrians, "but I wouldn't want to put a churning concrete truck there."
The Walls
A few months after the initial Caltrans letter, the city posted and starting enforcing load limits for Higuera Street and began studying what could be done with the bridge.
The first study on the bridge, completed in September 1995, indicated that the walls would probably have to come down, or at the very least some new foundation for the deck would have to be built.
"Based upon the voided conditions and the general lack of mortar observed in the exterior of the north wall, it is concluded that the walls should not be relied upon for the foundation of the bridge," wrote Dennis Shallenberger, an engineer with Earth Systems Consultants, which did studies for the city.
Yet follow-up studies and field testing by the city have found that the walls can be made stable enough to serve as the foundation for the bridge, a conclusion with which Shallenberger says he now agrees.
To shore up the walls the project will include three-inch-wide holes drilled into the top of the walls every nine feet and extending 10 feet into the bedrock.
Then, three-quarter-inch steel rods will be placed in the holes, followed by an industrial grout that will be pumped under pressure into the hole. Lynch said the idea is that the grout will fill not just the hole, but will expand to fill whatever cracks or cavities there are in the existing mortar.
Such a technique was applied to a test portion of the wall last October, she said, with impressive results. While the walls are in good shape considering their age, Lynch said the work will make them stronger than ever.
"They'll be solid as a rock," she said.
A Unique Bridge
Although Lynch is confident that the city will have all the needed federal approvals for creekbed work by the time the project is set to begin, the project has seen delays before.
Hopes of getting the project under way last summer were dashed when the State Office of Historic Preservation deemed the bridge a historically significant structure and required it to be preserved or some mitigation to be developed to offset its loss.
After many months of negotiations, it was agreed that extensive photography will be done on the entire structure and through the replacement project, and those photos will be kept at the Library of Congress for scholarly uses.
Lynch also disputed the opinion that the nearly seven years it will have taken to replace the deteriorated bridge is unreasonably long: "With the state involved there are just extra approvals you have to get."
Much of the Higuera Street Bridge's historic significance comes from the fact that few bridges in California that completely covered urban creeks have survived urban renewal efforts of the last 40 years, which have stressed opening up creeks.
"What's unusual is it's still there with the city built up around it," said Caltrans supervising bridge engineer Tom Harrington, who performed the first Caltrans inspection on the Higuera Street Bridge in 1980.
Rutt said there are few bridges like the Higuera Street Bridge in California. It is unique not so much for its length–Stockton has an even longer channel running under its downtown–but because of its longevity and the piecemeal way it was done.
"It's really several different bridges connected together," Rutt said, "and that it continues for several city blocks."
What Rutt says is true. Even though the city project only concerns itself with the 450-foot section known as the Higuera Street Bridge, the actual San Luis Creek channel under downtown is even longer.
The creek first goes underground just past Marsh Street, curving left past a graffitied underground hangout for young hooligans, where it is joined by an underground storm culvert built in 1989.
After traveling the long, dark straightaway under Higuera Street, illuminated occasionally and barely by Higuera's storm drains, it curves to the right under Mo's, behind which it daylights before heading back under Morro Street, private businesses, and Chorro Street before remaining above ground.
Public Project
Only the portion of the Higuera Street Bridge contained in the city right of way will be included in the project, although the bridge also supports private buildings and businesses, including Thai Classic and Mo's.
Matt Quaglino, who owns the building housing Mo's, said the bridge under that building is actually newer than the portion in the street and is far more structurally stable.
"That building was built as a bridge across the creek," he said. "It's sound. The bottom of it is concrete.... It is not is the same conduit as the rest of the bridge."
Thai Classic does sit on the original bridge. Although a rear decking portion at the bridge's edge was reinforced in recent years, the bridge under Thai Classic could still be weak. Lynch said the city has not researched that area because it is outside the city right of way, and the city has no authority to order the building owners to fix the bridge at this point.
"Their loading is different, so I'm not sure it needs the same support the street does," Lynch said.
As to whether the unreinforced masonry walls that support the bridge could prove unstable in an earthquake, such questions won't even be addressed until the year 2017 for many of San Luis Obispo's 109 buildings on the seismic retrofit list, that is, buildings considered unsafe in an earthquake. Thai Classic is on that list.
Chief building official Tom Baasch said building owners are only required to bring buildings up to current seismic standards if they want to put on a new roof, if the occupancy classification of a business changes (such as from restaurant to retail store), or by the year 2017.
Only when the city investigates what a building would need to meet seismic standards would it look into the seismic strength of the walls supporting Thai Classic's portion of the Higuera Street Bridge.
"We would ask that question when one of those triggers occurs," Baasch said.
For their part, the building owners aren't planning to address what's under their building at this point.
"We have no intention of doing any work down there because we don't think there's a problem," said part-owner Joseph Delucia, who also doesn't believe the building belongs on the list of buildings that will ultimately need seismic retrofitting, citing recent testing on the building's walls.
Mo's is also on the seismic retrofit list, and Quaglino said the disruptions from either the Higuera Street Bridge project or a subsequent development project at Court Street might be the best time to do that work.
"We had a seismic evaluation done and we have a plan. We could pull permits now," Quaglino said. "It might be an opportunity to do that work."
Transforming Downtown Again
Downtown San Luis Obispo was transformed by the 1892 walling of San Luis Creek, and again by the 1910 placement of the current deck over that wall.
This year, the Higuera Street Bridge will again transform the downtown, but local business people are hoping the short-term effects of that change aren't too damaging.
"Our concern is the health of the downtown while it's going on," said Mike Stanton, president of the Downtown Association. "The association has been very adamant that it have minimal interruptions. That's people's livelihoods we're talking about."
To accommodate that concern, Lynch said the city has pledged to keep at least two lanes of traffic on Higuera Street open during business hours throughout the project.
Minimizing project impacts on the area was also a big reason why the city decided to use prefabricated, prestressed concrete decks, rather than the more time-consuming–but cheaper–pouring of decks on site.
The street will need to be shut down on a few occasions while the decks are being brought in and placed, but Lynch said that work will most likely be done late at night, allowing Higuera Street to remain open during the day.
Stanton said the Downtown Association is pleased with the city's effort to minimize project impacts, but he noted, "It will still be difficult for the people in that area."
To help keep the public informed that the upper downtown area is still alive and thriving, the city has given the Downtown Association an advertising budget of $25,000 to offset project impacts.
At least some of that money will be used for outreach to radio stations, said Stanton, who said many downtown business owners were unhappy with local radio disc jockeys during the Marsh Street renovation project two years ago, when DJs would routinely warn listeners to avoid the congested downtown areas.
"We don't want to go through that again," Stanton said.
Once the bridge replacement is complete, and the sidewalks in the area have been redesigned as more pedestrian-friendly, the Higuera Street Bridge will have transformed downtown again.
And most hope it will be the last transformation for a long, long time. Æ
New Times staff writer Steven T. Jones has firsthand knowledge that anyone walking under Higuera Street Bridge will get wet up to their thighs.