Inverness water tanks could face total replacement

David Briggs
WATER: Decades ago, the Inverness Public Utility District bought two used redwood tanks that together can hold 40,000 gallons. The tanks could be replaced in a capital improvement program.  
03/09/2017

The Inverness Public Utility District is preparing plans to replace two aging redwood tanks in Seahaven—the first step in a capital improvement program to replace many or all of the system’s 11 tanks with seismically safe designs. Loans and a rate increase are likely components of the program, which is likely to cost between $2.2 million and $3 million. 

The program is in its early stages. The district recently commissioned a geotechnical survey of each of its five tank sites, and designs for the first tank replacements were presented at a board meeting in February. In January, the board directed its general manager, Ken Eichstaedt, to develop a rate increase strategy, according to board minutes.

“I am kind of trying to move us into the 21st century,” Mr. Eichstaedt told the Light.

The capital improvement program was spearheaded by Mr. Eichstaedt, who replaced Scott McMorrow last summer. The new director has a few key concerns about the tank system, which is comprised of seven redwood tanks and four steel tanks collectively holding about 425,200 gallons of water for 515 connections and firefighting efforts. 

None of the tanks are strapped to their foundations and their couplings, where water comes in and out, are inflexible. These facts mean the district faces significant risks in the event of an
earthquake.

“I don’t want to scare people,” Mr. Eichstaedt said, “but we’re in earthquake country.” According to the United States Geological Survey, there is a 72 percent probability that one or more earthquakes with a magnitude of 6.7 or higher will occur in the Bay Area between 2014 and 2043. 

Redwood tanks can also require more chlorine than steel tanks, so eliminating them could curb disinfection byproducts, which are considered carcinogenic and limited by the Environmental Protection Agency. They also have a longer lifespan.

Board president Ken Emanuels said it seemed “beyond question” that the redwood tanks were approaching the end of their useful life. “They’re still working, but obviously they’re not going to last forever, so it’s a good idea to start a program,” he said this week.

The first two tanks slated for replacement—the Stockstill tanks, in Seahaven—are over 60 years old. The redwood tanks have rotting underpinnings, the steel straps that hold the tanks together are corroded and ferns are growing out of them. As a bonus, they’re also two of the most easily accessible tanks.

Mr. Eichstaedt said the tanks are also important for firefighting, given their proximity to Tomales Bay State Park.

The two tanks would be replaced by a single steel tank that would hold the same amount of water. New design standards that require extra “free board”—or sloshing room—could also be a boon for fire protection, since that extra room could be filled in an emergency.

And though steel tanks don’t have some of the issues that redwood tanks have, their interiors need to be recoated periodically. Mr. Eichstaedt said the cost of relining one is about $100,000, or about a third the cost of a tank replacement. 

Given their other problems and the fact that some are nearing the end of their roughly 50-year estimated lifespan, it makes more sense to just replace them, too, he said.

All the new tanks would have flexible couplings so they can move without breaking during earthquakes, and would be anchored to their foundations.

The district can pay for the Stockstill tank out of its reserves, which total $1.5 million—a number Mr. Emanuels said was a credit to Mr. McMorrow’s careful budgeting. But given the costs of the entire program and the fact that board policy requires keeping roughly $870,000 in reserves, the district must find other funds.

Mr. Eichstaedt said grants are out of the question because Inverness’s average income is too high. He has been investigating loans available through a state revolving fund, the California Special Districts Association and the United States Department of Agriculture, to which Mr. Eichstaedt recently gave a tour.

But a rate increase also seems likely. 

“I’m predicting that we’ll have to combine [loans] with some water rate increases as well,” Mr. Emanuels said. “We’ve had constant water rates for a long time.” The specifics of an increase would depend on loan terms.

The district last raised rates in 2009, but it still boasts low rates compared to other West Marin providers. According to a 2016 comparison compiled by the North Marin Water District, water in Inverness costs the average customer $783 a year. That number in Bolinas is $1,662; in Stinson Beach, it is $1,238 and for North Marin Water District customers it’s $735.