Thursday, July 18, 2013

Water Stays On In Prince George County

From Middlesex County
Last Thursday sensors that had just recently been installed on a water main began hearing the pings they were listening for indicating an imminent failure of a concrete water main in Prince Georges County. Washington Suburban Sanitary Commission, WSSC, immediately planned a shut-down and replacement of the section of piping that began Tuesday evening. WSSC announced that water in the affected area of Prince George’s County was expected to be out for several days as the concrete water main is replaced with a more durable steel pipe because the nearest valve that would have limited the shutdown had failed. However, two WSSC employees were able to repair the 48 year old valve in place and the repair held. Diminished water supply remains in Southwest Prince George County. Mandatory water restrictions remain in place for the area to preserve the reduced water supply to the system. WSSC had warned the public that there would be no water for up to 5 days. Though it was responsible to warn the public of that possibility, especially after the valve failures during the fourth of July water main replacement in 2010, they have impaired their credibility for future warnings.

This shut down is how the sensor system that cost more than $21 million over the past six years is supposed to work. If you will recall, one of these massive water mains in the WSSC system exploded back in March in Chevy Chase without warning despite sensors being present in that section of piping. According to the Washington Post the March 18, 2013 pipe explosion created a 50-by-70-foot crater in Chevy Chase Lake Drive and adjacent stream bank, and the lack of warning was because the failure occurred in a joint. In  2010 a water main needed to be replaced over the fourth of July weekend forcing water restrictions on Montgomery and Prince George counties as the replacement did not go smoothly due to valve failures. In addition, in late 2008, a concrete main 66 inches in diameter burst in Bethesda, causing a torrent of frigid water that stranded cars and drivers. Other large water-main breaks in the past several years have led to advisories to boil-water for homes, businesses and hospitals as well as the temporary closure of schools and day-care centers.

The WSSC has approximately 350 miles of concrete mains designed to carry high volumes of pressurized water. These concrete water mains came into use in the United States and other nations in the late 1950’s and continued in use for water systems into the mid 1970’s when they were found to suffer from early failures. Water systems are built by the lowest bid contractor. During the rapid growth during the 1960’s concrete pipes reinforced and wrapped with steel wire were the least expensive method to build out the water infrastructure in the rapidly expanding communities, and the only option at the time for the largest diameter pipes.

This type of steel reinforced concrete pipe has failed catastrophically across the nation decades before their promised 100-year life expectancy would have predicted. Though the actual failure rate is still small at fewer than 1,000 known incidents in the 28,000 miles of this type of pipe installed nationwide, it is expected to increase as these pipes age. Unfortunately, WSSC has the second largest number of miles of this type of piping in the nation. In addition, the low-bidder supplier, Interpace, may have produced inferior pipe- most of the recorded failures of this type of pipe were in the Class IV wire Pre-stressed Concrete Cylinder pipe manufactured by Interpace. The company was successfully sued by WSSC and others and is now out of business. Nine of the WSSC’s concrete mains have blown apart since 1996.

The large diameter concrete pipes are the trunk lines or backbone of the WSSC’s 5,600-mile water distribution system for Montgomery’s and Prince George’s counties. The large transmission mains carry water from the treatment plants and feed the smaller pipes that reach into neighborhoods, homes and businesses. The pressure in the mains keeps the water pure and flowing. WSSC estimated that it would cost $2.9 billion to replace all 350 miles of large diameter concrete mains and instead they installed the sensor system to warn of an imminent rupture.

Fairfax Water has 109 miles of concrete pipe and has experienced 3 breaks since 1996. Only a small fraction of their concrete pipe is the large diameter pipe supplied by Interpace. Fairfax Water replaced about five miles of concrete Interpace pipe a decade ago. Moreover, most of Fairfax Water’s concrete mains are three feet in diameter or less. Not only would failure would be far less catastrophic, but the smaller pipes have experienced less failure.

In June, the U.S. Environmental Protection Agency (EPA) released the results of their 2011 Drinking Water Infrastructure Needs Survey and Assessment. The survey showed that $384 billion in improvements are needed for the nation’s drinking water infrastructure through 2030 for systems to continue providing safe drinking water to 297 million Americans 24 hours a day 7days a week. That estimate only covers infrastructure needs to maintain current systems and excludes costs for raw water supply (dams and reservoirs), water system expansions necessary for population growth, and water system operation and maintenance costs. These costs are not included in the EPA estimate, but do appear as part of the estimates of the American Water Works Association, AWWA, who estimated that the cost would be significantly higher than the EPA estimate, and could top $1 trillion. In addition, AWWA believes that WSSC may have the largest problem of failed Class IV wire Pre-stressed Concrete Cylinder pipes in the nation, but certainly in the east. We can not take for granted 24/7 water, sewer and electricity, or we will not have them.

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