When the Metro Council expanded the region's urban growth boundary in 2011, it did so with some expectation of how many homes those UGB expansion areas could have.
Faced with a state mandate to accommodate 20 years of new growth, the council agreed that the UGB expansion areas should support about 16,000 new homes, be they houses, apartments or condos. That worked out to about 15 units for each buildable acre added to the boundary.
Or so councilors thought.
One of those UGB expansion areas, in Beaverton, may not have as many buildable acres as councilors thought in 2011, and Beaverton planners are trying to figure out how to balance out the regional building requirements from 2011 with market realities and infrastructure costs as they plan out the South Cooper Mountain area.
At the time, Metro thought that area had about 310 acres available for homes, discounting real estate that'd be used for roads, schools, parks and other infrastructure. But a closer look at South Cooper Mountain shows that hillsides that can't be developed, and wetlands that must be protected, are cutting into the buildable acreage in the area.
But Metro's 2011 urban growth boundary expansion didn't call for 15 units per buildable acre – it called for South Cooper Mountain to hold at least 4,651 homes.
That's still possible, said Valerie Sutton, a planner in the Beaverton Community and Economic Development department. She said her department is just starting work developing two or three visions for the South Cooper Mountain area, near the intersection of Scholls Ferry and Roy Rogers roads southwest of the city.
Those scenarios will be run through computer models to study how well they'd meet regional housing objectives, the cost of infrastructure and the feasibility of implementation.
Once those scenarios are run, they'll be reviewed by citizens, the Beaverton Planning Commission and the Beaverton City Council, Sutton said.
It's possible that 4,651 homes might not be feasible in South Cooper Mountain – some estimates have the number closer to 3,100 homes.
"We're not backing off from trying to achieve the 15 units per acre," Sutton said. "We recognize that's what the (Metro) Council expected and that's what we are working toward."
Metro Councilor Craig Dirksen was mayor of Tigard when the Council expanded the UGB in 2011. Now on the regional board, his district includes the South Cooper Mountain area.
He said he'd be willing to be flexible if Beaverton finds it can't get close to the 4,651 unit threshold.
"If Beaverton were to come back and say 'We really don't want to put that many units here and this is why,' I would want them to be able to say 'We can take the rest of the capacity that we don't think fits well here, and put it somewhere else so we still end up with the same capacity,'" Dirksen said.
Metro Councilor Kathryn Harrington, who was one of six councilors to vote in favor of the South Cooper Mountain expansion in 2011, said part of the reason for planning is to learn more about the area being planned. She pointed out that there are a variety of issues that go into planning new expansion areas.
"You have to have enough capacity so the product will sell, meet community needs and the finance plan will work," Harrington said. Homes have to be affordable, but cities have to collect enough in construction fees from homes to pay for things like pumps to bring water to homes on hillsides.
Not enough homes and you can't afford the pumps; too many homes and the pumps have to be bigger and more expensive.
At the end of the day, Harrington said, the discussions are all about protecting the region's farm and forest land to preserve quality of life and contribute to the traded-sector economy.
Beaverton hopes to have a plan approved for South Cooper Mountain in about a year.
Note: An earlier version of this story inaccurately described Metro's role in reviewing the planning for South Cooper Mountain. This version has been corrected.