By Midge Pierce
Excavation work needed to divert drinking water from Mt. Tabor continues on the park southside as part of the process to disconnect the decommissioned open air reservoirs. Most of the recent impact of heavy equipment and potholing has been below Reservoir 1 near Lincoln St. at its entrance near the off-leash dog park.
So far, work is moving forward on schedule to meet federal deadlines to cover or treat drinking water. A citizens committee continues to meet with PWB engineers to protect trees and historic structures and mitigate disruption to traffic, bikes and pedestrians. “We’ve put the water bureau on notice that we’re watching,” says neighborhood association member Bing Wong.
Updates and closures on construction work, now called the Mt. Tabor Adjustments project, can be found at portlandoregon.gov/water/64097. Signs are posted ahead of time. Residents can sign up for advance email notices of closures.
Even with the big dig underway, questions persist about why the closure is necessary. Critics claim the fresh air purification of open reservoirs is unmatched by the closed tank storage at the new Powell Butte facility and some ask whether the reservoirs might provide useful storage during future periods of low rainfall.
Water shortage is a non- issue and continued use of Mt. Tabor for potable water is not part of climate change plans, according to the PWB. Following this summer’s drought, the City’s Bull Run watershed refilled in a matter of days after the first torrents.
PWB spokesperson Jaymee Cuti says Portland is simply not at risk of the kind of water shortages felt elsewhere. Bull Run is rain, not snow fed, and therefore less vulnerable to warming temperatures, she claims, adding that Portland’s backup groundwater supply can be used to supplement water needs and increase the system’s resilience.
Cuti says that even in the face of a water shortage, Mt. Tabor is insufficient. “All of Mt. Tabor’s soon-to-be retired storage would amount to only one day of water by summer demand figures”.
She emphasizes that once the Mt. Tabor reservoirs are no longer connected to the distribution system, the water in the basins will no longer be considered potable.
As for using Mt. Tabor to store water during emergencies, she says that too is impractical since the basins do not meet current seismic standards.
“The major focus of the Portland Water Bureau for the last several decades has been to ensure that the water supply facilities can withstand seismic forces and be functional immediately after an earthquake. Newly-constructed reservoirs at Kelly Butte and Powell Butte and the future reservoirs at Washington Park were all designed to meet current seismic standards.
“The existing open reservoirs at Mt. Tabor were not,” she says, adding that any future use as reservoirs would still have to comply with federal rules.
“That means that either treatment plants and some sort of holding tank would be needed to achieve chlorine contact time at the outlets of uncovered facilities or the reservoirs would need to be covered.
“To comply with the rule, the reservoirs cannot be put back into use in their current state. Upgrading them at the Mt. Tabor site for any future drinking water purpose will be extremely expensive.”