Planned Inverness water tanks will be smaller

02/08/2018

Two new steel tanks that will soon convey most of Inverness’s water will now hold less water than hoped for, after one tank’s foundation was discovered to encroach on a neighbor’s property. And after another neighbor complained about the tanks’ increased height, the Inverness Public Utility District is revising structural plans to accommodate shorter ones than were originally planned. On Wednesday, the district board voted unanimously to approve new plans for the replacement of the Tenney tanks, which Ken Eichstaedt, the general manager for the district, characterized as the “heart of our water system.” The 40-plus-year-old redwood tanks, located off Perth Way, convey 100 percent of the village’s treated water in the winter and 80 percent of its treated water during the rest of the year. Eleven different sources provide water for Inverness, and the majority of those are streams and creeks that flow from Mount Vision down into the district’s First Valley treatment facility; pulled by gravity, the water then travels to the Tenney tanks for storage. But those tanks are aging, and their redwood composition can contribute to the production of carcinogenic compounds. Replacing them with seismically safe, steel structures is part of a $2.2 million to $3 million capital improvement project that includes improving water storage capacity for a district that has to think about drought. Two other Inverness tanks, called the Stockstill tanks, were recently replaced and will likely come online in the next few weeks. Though the board approved the Tenny tank replacement plans last fall, two roadblocks later arose. First, the district discovered that the concrete foundation of one of the Tenney tanks encroached on a neighboring property, owned by the Wyman family, by four feet. Second, neighbors Tom and Sherry Baty, whose property is one of three that border the lot owned by the district, complained about the new tanks’ height, which was meant to increase by four feet. The Batys also expressed concern about the tanks blending into the surroundings and about the potential impacts on vegetation and the access road during construction. Now, the water district will move forward with tanks between 14.5 and 19 feet tall—each two feet shorter than originally planned and two feet taller than the current tanks. To address the property line issue, the district plans to shrink the diameter of the concrete foundation. As a result, the water tanks storage capacity will grow from its current 70,000 gallons to only around 88,000 gallons, as opposed to the 118,000 gallons the district had hoped for. So that the tanks were still strong enough to withstand a large earthquake, Mr. Eichsteadt said he had to make some adjustments to the tanks’ structure. “In order to comply with California building code, we have to leave space in the tanks to provide for the sloshing of stored liquid in the case of a large seismic event. We can lower the tanks and still be in compliance, however, if we focus on hardening the roof structure and increasing the strength of the foundation,” he explained. The district board made their approval contingent upon the approval of the contracted engineer and the tank manufacturer, and on an evaluation of any effects of the final plans, such as cost and liability. They also approved concessions to address the Batys’ concerns, agreeing to make sure the paint on the tanks blends into the surrounding, conduct any necessary repairs to the access road after construction, minimize impacts to vegetation and restore any other impacts after construction, which will begin by 2019.