Decisions made about Cooper Mountain, River Terrace and South Hillsboro in 2014 will impact creeks, forests, wetlands and the Tualatin River for the next century or more.
Removal of trees and increases in impervious cover on areas with steep slopes and shallow soils could mean the repeat of past mistakes that severely damaged local creeks. These negative impacts could be minimized if the master plans for these new urban areas included reasonable considerations for stormwater runoff and protecting tree groves.
Deforestation by private landowners has already begun on Cooper Mountain, and the city of Beaverton has no plans, no regulation and no incentives to prevent it. Removing forests means more erosive, polluted stormwater runoff entering creeks from the slopes of Cooper Mountain.
The financial benefits to the city of Beaverton and Clean Water Services of preserving trees for stormwater management far outweighs the lumber value of these trees, yet no one is making offers to these property owners to preserve their tree groves.
In contrast, the city of Tigard has identified tree groves in the River Terrace planning area and offers flexible development standards and incentives for property owners to protect these groves.
In the South Cooper Mountain Prospectus, the city promised low-impact development with zero effective impervious area, in other words no stormwater runoff. Yet soil surveys of South Cooper Mountain indicate it is unsuitable for stormwater infiltration required by many low-impact development techniques. It remains to be seen how and if Beaverton planners will eliminate runoff, considering their failure to protect tree groves.
Past development on Bull Mountain caused deep erosion in creeks and flooding downstream in areas of King City. Last year, The Times reported on one such washout on the southern slopes of Bull Mountain (Mike Meyers Bull Mountain washout by Barbara Sherman, Thursday, May 16, 2013). Will development of River Terrace on the western slopes of Bull Mountain cause similar problems?
One proposal involves piping stormwater runoff from River Terrace directly to the Tualatin River, bypassing creeks. While this may prevent some catastrophic erosion in Bull Mountain creeks, it is an unsustainable practice that wastes valuable energy and water and increases storm flows in the Tualatin River.
The city of Tigard injects about 275 million gallons of water piped from distant watersheds into the Bull Mountain aquifer each winter to be recovered in the summer. It is inefficient and wasteful to pump water from Bull Run and the Clackamas River while dumping water that falls on Bull Mountain into the Tualatin River.
Tualatin Riverkeepers has advocated long and loudly to avoid development on slopes, to create urban forestry plans to preserve groves and require zero runoff using low-impact development techniques. 2014 will be a watershed year, with new design and construction standards, a new municipal storm sewer permit and planning for four new urban areas. This will be a year when your voice for clean water must be heard.
You can learn more about these plans by attending the Tualatin River Watershed Council meeting tonight (Thursday) from 7 to 9 p.m. at Clean Water Services administration building, 2550 S.W. Hillsboro Highway, in Hillsboro.
Brian Wegener serves as the Tualatin Riverkeepers advocacy and communications manager.