Inverness residents have long been engaged with their village’s water supply. Intrepid locals helped wrest control of the district from a private company in the late 1970s and spoke out against sourcing water during dry spells from the North Marin Water District in the 1980s. But some may not be aware that the Inverness Public Utility District, known as IPUD, is on the cusp of improving the water that is shuttled through the pipes and tanks around town and welcomed into homes with the twist of a faucet knob or the pull of a shower handle.
The district recently started testing a filtration system to reduce levels of potentially toxic compounds without compromising the water with more chemicals or disinfectants. The nanofiltration technology, originally used in food processing to lighten the color of soy sauce, could be installed throughout the district sometime this spring, according to IPUD General Manager Scott McMorrow.
Over a decade ago, in 1996, IPUD installed a new filtration system to comply with environmental regulations, which included eliminating disease-causing parasites like giardia. The Memcor filters remove particulates larger than a one-fifth of a micron after the water flows through chicken wire at the creeks to remove sticks and other debris, but before the water is disinfected.
In the past couple of years, however, a new problem arose. Despite no changes in the district’s operations, employees tracked an increase in the amount of disinfection byproducts (DBP’s) in the water system, at times surpassing Environmental Protection Agency (EPA) limits. DBP’s result from the interaction of a disinfecting agent required by law—in IPUD’s case, chlorine—and dissolved material that passes through the current filtration system.
Experts emphasize that people should welcome disinfectants in their tap water. Michael Plewa, professor emeritus of genetics at the University of Illinois at Urbana-Champaign, who has done extensive research on DBP’s, called water disinfection “the most important public health achievement of the 20th century.” It prevents potentially deadly diseases like cholera. But in the 1970s, he said, improved tracking equipment revealed an unintended consequence.
Mr. McMorrow explained, “So you’ve got chlorine, you’ve got organic matter, and then sometimes, not all the time, but sometimes they’ll combine and create a thing called a disinfectant byproduct.”
While establishing why DBP’s began to rise in Inverness water is neither possible nor necessary, IPUD employees have a theory. They believe sudden oak death, a disease found on the central and northern California coast as well as a few locations in Oregon, could be the culprit. Though IPUD cannot test that belief, the disease, which first hit West Marin in 2004, could have led to an increase in organic material in the creeks, Mr. McMorrow said. University of California, Berkeley professor and scientific advisor to the California Oak Mortality Task Force Matteo Garbelotto told the Light in a phone interview that in West Marin, sudden oak death hit Inverness particularly hard.
Dr. Plewa, who called water-borne diseases a “scourge,” emphasized that the risks posed by untreated water vastly outweigh the risks associated with DBP’s. But Dr. Plewa, who is also the associate director for interdisciplinary research at his university’s Global Safe Water Institute, said that studies have connected long-term DBP exposure to bladder cancer and, to a lesser extent, to colo-rectal cancer. One type of DBP, haloacetic acids (HAA5’s), had been linked to birth defects in mice, he said.
Water districts address the DBP problem in different ways. Some have replaced chlorine with chloramine—a combination of chlorine and ammonia—because the latter results in fewer DBP’s that the EPA regulates, namely total trihalomethanes (TTHM’s) and HAA5’s. But Dr. Plewa said that chloramine can actually produce other, more toxic DBPs not currently regulated by the EPA and added that more “enlightened” districts seek instead to reduce the presence of organic material in the first place, which has been IPUD’s path. Jim Fox, chief of operations for the district, said he believes more and more DBP’s will eventually be regulated by the EPA, saying it’s just a question of when.
The most current DBP regulations, finalized by the EPA in 1998, reduced the allowable maximum presence of specific DBP’s: TTHM’s from 100 parts per billion (ppb) to 80 and HAA5’s from 80 to 60.
Between 2008 and the middle of 2010, IPUD exceeded EPA limits for TTHM’s, which during that period reached a high of about 125 ppb. After that peak, levels fell and were within compliance, but the California Department of Health requires districts to deal with those highs.
The district tested different tactics to remove the dissolved material, or “color.” Aeration, or simply spraying the water to remove compounds, helped but did not go far enough. Employees tried a granular activated carbon system—basically a water district’s version of a Britta filter—but it was cost prohibitive and didn’t work as well over time as hoped. Mr. McMorrow said he is adamantly opposed to using chloramine.
IPUD was almost at the end of its rope. Then consultant and former employee Jonathan Van Bourg—who worked at IPUD in the early 1980s, eventually moved to a water district in Maine for about two decades and retired in West Marin in recent years—found an elegant solution: just use a finer filter.
Mr. Van Bourg explained to the Light that the nanofiltration system IPUD is testing—the same one that was created to make soy sauce lighter—removes the color causing the DBP’s.
In fact, the nanofilter has made a considerable difference. In the first half of 2012, TTHM levels hovered around 60 ppb and HAA5’s around 55 ppb. At the Third Valley treatment plant, where a rented filter has been installed since October for testing, levels for both types of DBPs fell to 10 ppb, according to Mr. McMorrow.
During a tour of IPUD’s facilities, Ken Fox, who spends much of his day driving to various sites around IPUD to test the water and monitor equipment, offered the Light a close-up look at what the new filtration system had accomplished. He held up for display a vial of Memcor-filtered water. Though clear to the naked eye, the colorimeter—an instrument that looks roughly like a calculator, with a slot at the top where vials of water are tested—betrayed the presence of color.
Mr. Fox, clearly happy to exhibit this newest success, then plucked a vial of nanofiltered water. The transparent liquid looked just the same but measured virtually no color. Mr. Fox pointed to a green pipe low to the ground nearby. It filled a small cup with Budweiser-colored liquid, which was the backwash from the nanofilter—the color the nanofilter managed to remove from the water Inverness residents drink.
The nano unit, which is so fine that it requires a prefilter, currently filters the water after it passes through the Memcor unit. Pending another round of tests to confirm the nano’s effectiveness and preliminary board approval, IPUD’s next big step would be to release requests for proposals to purchase the system. Funds from the 2009 water rate increases have been squirreled away for the project. Mr. McMorrow hopes to have units in First and Third Valley treatment plants by May.
Mr. McMorrow emphasized that, in his role as “head bean counter,” he will investigate whether there is a way to reduce costs with a different prefilter. This attention to economy tracks with other ways in which the even-keeled general manager has kept a close eye on IPUD finances since taking the job in 2010. He says he has made sure employees aren’t working overtime and that IPUD’s second treatment plant is only in use when necessary.
After the DBP issue is in hand, the next major project would be replacing the remaining four redwood tanks with steel tanks. IPUD has seven tanks at five sites, the intermediary points between the treatment plant and people’s homes. Though they work well when they are full—water makes the wood expand, keeping the tank tight—low tank levels cause the wood to contract, causing leaks. Steel tanks also have a longer life.
The water system
IPUD pulls water from First Valley Creek, Second Valley Creek and on occasion from a well. At First Valley Creek, a series of three tiny dams called diversions—square concrete structures built into the creek—flow from one to another. A pipe at the third diversion relays babbling creek water down the hill and into the mechanical hum and roar of the First Valley treatment plant, IPUD’s primary plant. During a tour, Mr. McMorrow and Ken Fox pointed out the colorful pipes that fetch water from the diversions and export it out to the holding tanks. “Green means raw and blue means treated,” Mr. McMorrow explained. The “raw” or untreated water is funneled to the Memcor filter, comprised of floor-to-ceiling vertical grey tubes, each about five or six inches in diameter. The water flows up and down these tubes, each containing membranes with 10,000 hollow strand-like filters that are as thin as needles. This removes those tiny particulates.
As filtered water leaves the plant, it is spritzed with a small amount of chlorine. IPUD must ensure that at any given point—from when water leaves the plant to when it arrives at the homes of Inverness residents—there is a chlorine residual, meaning that it contains a minimum amount of disinfectant. Since the level degrades as it travels through the system, IPUD rechlorinates at some points in the system. After the nanofilter was installed IPUD has used less chlorine because the disinfectant has less with which to bind, although Mr. McMorrow did not yet have hard data on the reduction.
Once the water is “finished,” or treated with chlorine, some of it flows down to Tenney Tank, a redwood barrel that feeds some homes, and to the steel Colby Tank, lower down the hill, which supplies other houses. Gravity does substantive work for IPUD; it is only at two tank sites in Seahaven that water must be pumped up to the tanks, where a four-inch pipe carries the water back down the hill to faucets.
Typically, IPUD’s other treatment plant, the Third Valley plant, operates only during the drier summer months, when water demand rises. But this year is an exception; it is currently the test site for the nanofilter. This second plant at Third Valley is small, about 10 by 20 feet. They had to remove the doorframe to squeeze in the Memcor filter when it was installed in the 1990s.
Local control
Mr. McMorrow emphasized what he believes is the importance of local control of water resources, and he is not alone in his conviction. In 1979, residents overwhelmingly approved a ballot measure to allow IPUD to buy the private Inverness Water Company, which was owned by Citizens Utilities.
Local control proponents at the time claimed that the parent company allowed the system to become “rundown” and “deficient.” After the 1982 storms, IPUD built an emergency water line that connects to North Marin Water District in times of disaster. But a subsequent proposal to contract with North Marin to supply water during dry spells, as an insurance policy of sorts, raised the heckles of local water champions once again.
Some IPUD directors said the connection would only serve Inverness during dry spells and could only supply at maximum 20 percent of the annual supply, and a vocal coalition supported the connection. But others feared outside water would encourage bad water habits, shift the conversation away from conservation and encourage too much development. In 1987, the Light reported that residents were getting multiple calls per day from both camps. Then an engineer’s report found that there was enough water in Inverness to get through dry spells and the measure was eventually defeated at the ballot box.
While there have been times in the past 34 years when the vocal citizenry has vexed the utility district, Mr. McMorrow, who hails from the East Coast, said, “The community is wonderful here. And this does not happen elsewhere, I’m convinced of it. So if there’s a leak somewhere,” he said, “people will call and say, ‘Hey, my neighbor’s sink is leaking.’ I’m amazed by this all the time.”