The city of West Linn might have to help the city of Lake Oswego pay for a water transmission line to connect to Tigard's waterlines.
This is one of the solutions being considered by city officials to ensure water supply during an emergency, according to information provided the city by a consulting firm.
Recognizing that at least one pump station needs to be upgraded and storage capacity should be increased, the consultants and staff members gave the council an update at a recent work session.
But the update wasn't a complete picture. The consultants were looking for direction in order to be efficient in their continuing work to complete the master plan.
Consultants Chris Uber and Brian Ginter told the council that an emergency was not a fire on a hot day, because the water system should be designed to supply that need. Instead, an emergency could be caused by a pumping station shutdown.
With the possibility of a sizeable earthquake rupturing the I-205 bridge water transmission line from Oregon City, the city of West Linn is trying to build a solution into its water master plan as well as update its storage capacities.
A six-million-gallon water tie with Lake Oswego water had been designed to assist West Linn in the event that the supply from the South
Fork water treatment plant in Oregon City was interrupted, but Uber said he had heard from Lake Oswego officials that they would not be able to supply both cities in that type of emergency.
The plan the West Linn City Council preferred was offered along with two other options - both more expensive than the preferred plan.
West Linn is definitely in need of replacing the 100-year-old Bolton reservoir, Uber said, which holds just over two million gallons. Construction of a new reservoir has problems to overcome such as the instability of surrounding soil.
Since West Linn has an ultimate (at build-out) deficit of 6.4 million gallons of storage, Uber said, to simplify the solution all the city would need is to replace the Bolton Reservoir with 8.4 million gallons of storage.
Easier said than done, he said.
Another (expensive and difficult) solution would be to build a second river crossing (underground) to access water from the South Fork treatment plant in Oregon City.
And the third option given the councilors was to bolster the supply of water to Lake Oswego so that it would be able to supply West Linn needs in an emergency.
That plan, Uber said, would include connecting Tigard to a 36-inch supply line from a 50-million-gallon Portland reservoir, and then connecting Lake Oswego water lines to Tigard with gravity flow.
With the increased availability of water, Lake Oswego would be able to supply West Linn through its intertie near Hwy. 43.
Preliminary cost estimates include about $12 million to increase storage to 8.4 million gallons for the Bolton pressure zone. It would cost nearly the same amount to bring a new supply line from Oregon City under the Willamette River and replace the Bolton Reservoir with similar size.
But with the preferred option of tying into Portland water through Lake Oswego and Tigard, the approximate cost would be only about $3.5 million.
Councilor Mike Gates said he prefers the intertie to Tigard, but he also cannot see this type of upgrade helping in the event of a major seismic event.
'When that earthquake hits,' he said, 'we're not going to be the only ones suffering the same emergency. I can see just about every waterline in the region going down.'
Mayor Norm King pointed out that West Linn is very dependent on water being pumped, which means if electric power is interrupted, so is much of the water.
'Our intent tonight,' Uber said, 'is to get consensus on the approach we're taking. We haven't done a complete solution set development, but we have determined those in a preliminary manner. We will be looking at total storage capacity as well as other solutions.'
The update given councilors was simplified, the consultants said, and there are other places in the city's water system that need upgrades, including pumps, storage capacities and interties between the zones.
Assistant City Engineer Dennis Wright asked the council to give the consultants direction in their work.
'I am wondering if you want the consultants to continue with what we saw as the lowest-cost option or to pursue that as well as storage in each of the zones. We need that information to continue pressing through the master plan.'
Councilors' consensus suggested pursuing the option with the other cities to access Portland water, since it was the lease expensive.