Andy Tullis / The Bulletin fileConstruction work to mitigate the flooding problem in the Third Street underpass in 2013.

After the installation of a pumping station, piping, swales and basins along the Southeast Third Street corridor, city of Bend officials don’t expect the underpass to flood anytime soon.

Crews started work on the $3 million Third Street underpass project in May 2013, installing vegetated swales and planters on Northeast Fifth Street and Northeast Clay and Burnside avenues. A new pump system was installed near the underpass that connects to a larger collection pipe running under Southeast Third and Scott streets.

“There were drill holes on the bottom of it,” said Eric Forster, a city project manager. “We closed those and put in a pump, and now we pump it over to a regional stormwater pond over by the parkway.”

For several years, stormwater runoff would overwhelm the previous drainage facilities and cause repeated floods in the basin area, leading to road closures and traffic congestion. The swales and planters work together with catch basins along Third Street to filter water closer to its source and reduce the potential for flooding, Forster said.

“They work as interceptors and they flatten the peaks of storm events and they accept a certain amount of runoff,” he said. “They will not absorb all the runoff, but they significantly decrease the amount of water that reaches the underpass.”

Forster said instead of the water coming down all the way into the underpass, the catch basins allow the water to flow by gravity to the stormwater pond. Construction on the underpass, beneath the Burlington Northern Santa Fe Railway, is complete, though the city plans to close the underpass overnight in July to do permanent striping on the roadway.

The Third Street underpass was one of the city’s main priorities on the revised stormwater master plan, city stormwater program manager Wendy Edde said Friday.

“That was one of the major problem areas in town for a number of reasons,” she said. “It covers a huge area, 54 to 55 acres that drain into that basin, and a good portion of that area is in the groundwater protection zone. If a pollutant were to get into the system, it would make it to our wells soon after.”

Forster said there hasn’t been any flooding on the underpass since the project was completed.

“I know that when we started having some storm events, there was water showing up at the drainage pond,” he said. “But it should be dry as a bone down there.”

The city has planned pipe repairs, but it is still looking to fund a program to replace stormwater pipes that drain into the Deschutes River.

“From the west hills down, a lot of downtown, we would focus on that area first,” Edde said.

The 58 improvement projects on the revised stormwater master plan total $25.2 million over a 20-year period. For homeowners, a stormwater utility fee increase will likely come into play to finance these projects, ranging from $4.36 a month for a gradual rate increase to $5.80 a month for an accelerated increase. Rates will vary with businesses depending on site infrastructure, impervious surface amounts and the final rate structure decided by the city.

“After the master plan is adopted, we would work with the (city’s) finance department on specifics as far as the rates,” Edde said. “Do you go little, do you go big? When would we anticipate those being adopted? How would that affect the credit program we have with businesses? That would be a separate process.”

Master plan priorities include a drainage improvement plan that will focus on areas around Awbrey and Pilot buttes and use techniques such as planter boxes to break up hardscape areas, where runoff is accelerated, dry wells, new stormwater piping and detention to a regional pond. There is no timeline, but the city plans to commission a report to make sure current pipes are sized to standard for a 25-year storm, according to Edde.

The plan also calls for an integrated stormwater solution to fix flooding problems at two other problematic underpasses in Bend, at Franklin and Greenwood avenues.

“Is there one solution that could benefit both? We want to look at them from a global sense,” Edde said. “The planning would take into account what’s best that also provides cost savings.”

City of Bend operations crews have been doing ongoing maintenance on the Franklin Avenue underpass, mostly to clean clogged drainage systems and maintain drill holes down to 35 feet.

“Since they’ve done that, we have not seen any condition where that area is going underwater and keeping traffic from flowing,” said Tom Hickmann, city engineering and infrastructure director.

Hickmann said the plan is to look at capital improvement projects as a whole and try to prioritize and combine stormwater and street projects. But stormwater projects have to be funded directly, and the reserves are empty.

“We just spent pretty much all the money we had on the Third Street underpass project,” he said. “Obviously if we have a street project and a stormwater issue, we’re not gonna leave the stormwater issue, we’re gonna fix it. Maybe we can adjust some operational funds to cover it. If that doesn’t work, then we would go to City Council to get the funding necessary.”

The city is accepting public feedback on its website through June 24 regarding the revised stormwater master plan.

“I’m hopeful that (the) council will be able to consider it within a July/August time frame,” Edde said.

—Reporter: 541-633-2117, mwarner@bendbulletin.com