OSU-Cascades Geotechnical study

OSU-Cascades gets good news on pumice mine

Engineering firm says construction is possible

By Tyler Leeds / The Bulletin

OSU-Cascades has been given cautious approval to transform a former pumice mine into a university campus, with a geotechnical investigation finding no hazards that rule out development.

The old mine, which has been scorned by opponents of the university’s proposed location as impractical, is the second piece of OSU-Cascades’ planned expansion into a four-year university on Bend’s west side. Initial development will be focused on an adjacent 10-acre wooded plot, and plans for that are being evaluated by an independent hearings officer for the city. Although it hasn’t been purchased yet, the mine could potentially add 46 acres to the campus, allowing the university to grow in the long term to its target maximum of 5,000 students.

“There’s a lot of potential for this site, and it’s definitely doable,” said Jane Barker, senior project manager of the university’s campus expansion.

“We will be conducting a lot of due diligence to make sure we understand the full extent of the site conditions and the possible financial impacts. There’s a lot of work to be done prior to understanding all of our options, but this report has given us a range of remediation options we can use,” Barker said Wednesday.

The study by Carlson Geotechnical highlighted two aspects of the site the university will have to improve before development. One is the presence of “uncontrolled fill materials,” including “boulders up to four feet in diameter,” which would not provide a stable base for construction. The other is the presence of steep, tall walls on the sides of the mine, in some places reaching 80 feet. Carlson found no areas of significant instability but, nonetheless, said because of their steepness, the walls “are susceptible to slope instability and rockfall,” especially during seismic activity.

The report offers a range of possible fixes. To address the issue of unsuitable fill material, the report says the soil could be entirely removed and replaced, treated or even simply avoided during construction. For the walls, the report suggests options ranging from placing buildings and paths at a safe setback to regrading the wall slopes to reinforcing them with walls.

“There was nothing extraordinary about the site in terms of the level of mitigation needed,” said Brad Wilcox, a senior engineer and department manager with Carlson. “We identified some options in the report. As they develop a plan for the campus, some of the options will come to make more sense than others.”

Wilcox said some of the things his firm could have found that would have been red flags include soils that sink or swell with moisture or are prone to lateral movement during an earthquake.

“From our standpoint, development can certainly proceed,” he said.

According to OSU-Cascades Communications and Outreach Director Christine Coffin, the university has until Sept. 1, 2017, to purchase the site for $7.9 million from owners 4-R Equipment. The university had hoped to close on the 46-acre site by March .

Before any purchase, the university plans to have the Carlson report peer-reviewed by multiple firms in addition to having more tests assessing different options to address potential problems.

The university has made an earnest payment of $150,000 on the site, with plans for an additional $100,000 to be paid out in the next few months. Costs for improving the site could vary greatly depending on how the university is planned. Kelly Sparks, associate vice president for finance and strategic planning, said such planning has been “put on pause” as the university focuses on the 10-acre site.

The university has not set a limit on what it will pay to fix the site, according to Coffin. However, preliminary estimates place the cost of remediation between $1.5 million and $7.5 million.

OSU-Cascades isn’t the first major project in Bend to deal with the challenges of an old pumice mine. In 2005, the athletic field at Summit High School (which opened in 2001) collapsed after being built atop a mine. After the collapse, which required $7.2 million to fix, the nearby housing development, NorthWest Crossing, did extensive work investigating soil conditions for its Discovery Park development, a 34-acre project located in another former pumice mine.

“Last year we completed the work there, replacing about 600,000 cubic yards of material,” said David Ford, NorthWest Crossing’s general manager and a Central Oregon Community College Board member who serves as the college’s liaison to OSU-Cascades. “It was very unfortunate what happened to the school district, but one that has benefited property owners with similar conditions since, as we all now know what the best practices and methodologies are for dealing with former pumice mines.”

The fact the university development is possible isn’t likely to satisfy critics, who have questioned whether students will want to attend class in a former mining site. Barker disagrees, saying she believes developing a campus with 80-foot high walls offers unexpected benefits.

“I think some of the geology is quite beautiful, and we may take an approach that highlights significant geology,” Barker said. “There’s an appeal to the varied topography as opposed to a traditional university, like you see in Corvallis. At (the University of California-Santa Cruz), which is based within a rich variety of topography, there’s something special. Of course, we’ll make sure everything is graded so it is accessible to the entire community, too.”

— Reporter: 541-633-2160, tleeds@bendbulletin.com