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  • 24 Jul 2014

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City seeing tainted water more often

Is it better testing or more contaminants landing in our water?


More contaminants have been found in Portland’s drinking water in recent years, and city officials don’t know why.

Water Bureau Director David Shaff thinks the increase may be related to a new, more sensitive testing method adopted by the city in 2007, but he cannot be certain.

Shaff says the bureau is taking several steps to improve water quality, but it remains to be seen whether they will be effective. The trend may not be reversed until all of the bureau’s open water reservoirs are replaced with sealed storage tanks — a project that is under way — but that is still years away.

The most highly publicized incidents have been the positive E. coli bacteria findings that resulted in three boil water notices in November 2009, July 2012 and May 2014. Despite the alarming nature of the notices, Shaff says there is no proof Portland’s water was dangerous to drink during the alerts.

“The Multnomah County Health Department received more phone calls than usual immediately after the (May 2014) boil water notice, but has not detected any increase in confirmed gastrointestinal illness,” Shaff says.

The same was true of the notices in 2009 and 2012.

E. coli was detected in both original and follow-up tests in 2009 and 2012, triggering the notices for west-side customers. The 2009 notice was the first one in Portland history.

Last month’s notice for all customers was triggered after E. coli was detected at three different locations on three consecutive days. It was ordered by the Oregon Health Authority and lifted after all of the follow-up tests came back negative for E. coli.

But E. coli is not the only bacteria being found in the water supply.

According to the Oregon Health Authority, total coliforms are not considered harmful. They are an “indicator organism” whose presence suggests that other microbiological contamination could be in the water, including some that could make people sick — including babies, the elderly and people with compromised immune systems.

The U.S Environmental Protection Agency has required testing for total colifoms since 1974. The water bureau says that since about 2009, total coliforms also have been detected five or six times a year, an increase from previous years.

The most recent positive coliform sample was taken on Thursday, June 5. Because follow-up tests came back negative, the bureau did not have to notify anyone. But in September 2013, the bureau was required to send letters to many west-side customers telling them that coliform bacteria had repeatedly been found in their drinking water.

No contamination source

Most of the time, the Water Bureau has been unable to confirm the source of the different kinds of bacteria.

After May’s boil water alert, two dead birds were found in Reservoir 5 on Mount Tabor. But E. coli also had been detected in Reservoir 1 on Mount Tabor, where no obvious source was found. E coli also was detected at a testing station at Southeast Salmon Street and Second Avenue, downstream from both reservoirs.

The sources of the contamination that triggered the boil water alerts in 2009 and 2012 were never found. Although E. coli was detected in Reservoir 3 in both of those cases, no dead animals or other obvious source was identified.

The source of the coliform bacteria in the west-side water supply in 2013 was never found, either. That part of the system is served by Reservoir 3 in Washington Park. No obvious source of contamination was found there at the time.

The situation is puzzling because Portland has not changed the source of its water or altered its treatment procedures since 2009. The Bull Run Reservoir is still the primary source of water, supplemented by the groundwater system along the Columbia River when it runs low near the end of each summer. And all of the open reservoirs are still being drained and cleaned every six months. Chlorine is still added to the water at several locations to kill contaminants such as bacteria. The amount recently was increased 14 percent in response to warmer weather.

“Our basic treatment has not changed, other than that we increased our chlorine dose. Our basic distribution system operations have not changed — in fact, we have taken some of our open reservoirs off line — and our sampling has not significantly changed since the start of the total coliform rule in 1990,” Shaff says.

The biggest change in recent years has been the kind of test used to detect coliform and E. coli bacteria. Until 2007, the bureau collected water samples in membranes that were sent to a laboratory to be cultured and examined. But since then, the bureau has switched to a test called Colilert-18, which claims to be quicker and more accurate.

Although bureau officials cannot be sure, they say the current test may do a better job of detecting contamination in the water that has always been there. But there is no way to know for sure.

“The Colilert test could be more sensitive to coliforms in our water than our previous analytical method. Membrane filtration is a more subjective test, requiring an analyst to look under the microscope at bacterial colonies, than the Colilert test, which looks for a change in color. Some tests might be better at detecting some total coliforms than other tests,” Shaff says.

Replacement water tanks

According to Shaff, the bureau is taking several steps to reduce the contaminants being found in the water.

“The Water Bureau has evaluated the situation and implemented several operational practices to improve water quality. This includes taking excess storage off line, deep cycling tanks, changing pumping operations, expanding its unidirectional flushing program and increasing water-quality monitoring,” Shaff says.

Bureau officials say the city’s five open reservoirs in Mount Tabor and Washington parks may be responsible for some, if not all, of the contamination. They are open to both people and animals, potential sources of coliform and E. coli bacteria. E. coli has been found in two of them during the past five years.

City officials have proposed replacing the open reservoirs with closed storage tanks for many years. Some neighborhood activists have adamantly opposed the idea, saying there is no proof anyone has ever become ill drinking Portland’s water. Now, after years of controversy, the water bureau is moving forward with plans to decommission and replace the open reservoirs. Projects estimated at around $285 million are either under construction or scheduled to begin.

A replacement 70 million-gallon underground storage tank is under construction at Powell Butte, where two covered reservoirs that can hold 50 million gallons of water already exist. After the new one is finished, the Mount Tabor Park reservoirs are expected to be taken off line starting in spring 2015.

In addition, a 10 million-gallon closed reservoir at Kelly Butte is scheduled to be replaced with a 25 million-gallon one by the end of 2015. And a new 15 million-gallon storage tank is scheduled to be built in the footprint of a reservoir in Washington Park that is empty. When it is finished, the remaining 16.4 million-gallon open reservoir there will be disconnected, possibly in late 2019.

Water bureau officials are hopeful that replacing the open reservoirs will reduce the frequency of the positive bacteria findings in the city’s water system, but they will not know for sure until after it happens.