Maple Leaf's endangered water tower is too low (and no good in an earthquake)

We’ve had more discussion on the plight of our empty water tower than on anything we posted since Maple Leaf Life launched. The city has no plans to return the 60-year-old neighborhood landmark to service, and no one knows if the tower will remain or be torn down.

There are opinions on both sides (including the innovative idea of turning it into a lookout tower for the new reservoir park), but Pablo wondered: ” How are we continuing to get adequate water pressure without this tank?”

We asked Seattle Public Utilities. Here’s what we learned:

* For the past 55 years, parts of Maple Leaf never have had adequate water pressure. Our water pressure depends on gravity, and the tower is too low.

* We’ve had better water pressure since last fall, when the  tower was emptied and we started getting water from a reservoir that’s 20 feet higher than our tower.

* The tower, which when full holds 8 million pounds of water 100 feet in the air, isn’t up to earthquake standards.

We spoke this morning with Bill Wells, a water quality and treatment manager, and Jon Ford, a senior civil engineer. Both are with Seattle Public Utilities.

Ford said in 1949, when the Maple Leaf tower and the tank on top were built at an elevation of 530 feet, they were at the north edge of the city and could serve homes to Northeast 85 Street. North of there (starting at about the Reservoir Bar & Grill and Art Tile) the homes are higher and at the time were outside the city.

But five years later that area annexed to Seattle, and suddenly the water tower was too low to supply the minimum “design pressure” there (which is 30 pounds per square inch, for those interested).

Late last summer, as work to bury the Maple Leaf Reservoir was to begin, “we looked at the pressure being low in this area,” said Wells, the manager. “We could have ended up keeping the tank and keeping the pressure lower,”  but that would have required expensive maintenance and finding a way to earthquake proof the structure. “The tank would certainly have needed a seismic upgrade,” said Ford.

“The most cost-effective solution,” Ford said, “was to decommission the tank, disconnect it from the system, and connect instead to the Lake Forest Reservoir” several miles to the north and at an elevation of 550 feet. That gives a pressure boost of an extra 9 pounds per square inch.

Today that higher pressure is serving Maple Leaf roughly east-west from Interstate 5 to Lake City Way, and north-south from Thornton Place to the Roosevelt Reservoir. It also serves higher elevations in Wedgwood and View Ridge.

As for the earthquake danger, Ford said with the tank empty of water, “that’s 8 million pounds you don’t have 100 feet in the air. The seismic issue was for a full tank, not an empty one.”