By Ann McCreary
Twisp residents are confident that when they turn on a faucet, they’ll get clean, safe drinking water. A new program instituted by the town aims to keep it that way.
Under certain situations, unintentional changes in water pressure can cause liquids to flow from homes or businesses back into the municipal water lines, potentially contaminating the public drinking water supply.
This reverse flow, called “backflow,” will be prevented through a new initiative that will identify and control potential situations that could jeopardize Twisp’s water supply.
For instance, a garden hose submerged in a hot tub or swimming pool, or connected to an insecticide sprayer, could siphon the material back into the water mains if pressure in those mains dropped unexpectedly and created a reverse flow.
A pressure drop could be caused by a break in the water main, for example, or if a large volume of water were withdrawn from fire hydrants to fight fire, said Andrew Denham, Twisp public works director.
The potential source of contamination is called a “cross connection” — the point in a plumbing system where the public potable water supply could be connected to potential contaminants. The risk can be eliminated by installation of backflow prevention devices at those connection points.
Twisp residents will soon be learning about the town’s new Cross Connection Control Program through fliers and other public information provided by the town. The Town Council recently adopted an ordinance calling for surveys of potential cross connections and installation of backflow prevention devices in homes and businesses to prevent backflow into the town water system.
Twisp’s municipal water supply is provided by two wells and is untreated, making it more “vulnerable” to potential contamination through cross connection, said Denham.
“Being an untreated water system, the consequences of a cross connection are just too high. We have to be very proactive in operations and maintenance as well as enforcement of a cross-control plan,” Denham said.
“It’s my understanding that there’s a common desire by town residents that the water supply remain untreated and I’m going to do everything I can to protect that,” Denham said.
“If we’re not able to effectively protect the integrity of the water system, the state Department of Health could potentially mandate some sort of treatment,” Denham said.
State requirements
State law requires that public water systems develop and implement cross-connection control programs, which are monitored by the state Department of Health.
For Twisp, the need to develop its program is linked to work that has just gotten underway to install new pressurized irrigation pipe within town limits for Methow Valley Irrigation District (MVID) members as part of the district’s Instream Flow Improvement Project.
“Heightened urgency came from MVID providing pressurized irrigation water within town. The possibility for cross connections is higher as a result of the new irrigation system, which creates the potential of higher water pressure than some parts of the town’s water system,” Denham said.
“If somehow the residential system was connected to the irrigation system and the irrigation pressure was higher, it would flow into the municipal system,” Denham said.
Although untreated, the town’s municipal water is tested regularly for bacteria and other contaminants to make sure it is safe, but irrigation water is not tested.
“When I became aware of the MVID project, I contacted a cross-control specialist and hired them to provide technical guidance,” said Denham, who became public works director five months ago.
For the past three months, Backflow Management Inc. from Oregon has been working as the town’s cross-control specialist to help develop a cross-connection control plan.
Under state law, if a hazardous or potentially hazardous cross connection cannot be eliminated, a backflow prevention device must be installed, tested a least once annually, and maintained for as long as the cross-connection potential exists.
The backflow prevention devices include a check valve that prevents water from flowing backwards.
The town and the backflow management consultants will survey properties in the municipal water system, which has 628 service connections, to identify cross connections, and determine whether they can be eliminated or whether a backflow prevention device needs to be installed, Denham said.
Some businesses are already required by law to have the devices in place, including wastewater treatment plants, car washes, film processers, dentist offices and medical clinics, Denham said.
Backflow incidents
Some documented backflow incidents around the nation have had disastrous results, according to information developed by the Town of Twisp. A high school in Oregon had antifreeze from an air conditioner backflow into water pipes, sending eight teachers to the hospital.
If the town determines through its survey that a backflow prevention device is required at a residence or business, it is the property owner’s responsibility to purchase, install, test, repair and maintain it, according to the town ordinance adopted in March. The devices cost about $100, Denham said.
The devices for MVID customers in Twisp will be purchased as part of the Instream Flow Improvement Project, said Roger Rowatt, a member of the project team. State law requires a cross-control device be installed for all properties serviced by irrigation as well as a municipal water supply.
When the new irrigation system is completed, MVID customers in Twisp will receive irrigation water either by gravity fed pipe connected to the enclosed east canal that diverts water from the Methow River, or from pressurized pipe on MVID’s west side that will draw water from ground wells.
As part of Twisp’s Cross Connection Control Program, Denham said he may become certified as the town’s cross-control specialist and assume those responsibilities from Backflow Management Inc., depending on time constraints and cost-effectiveness.
Twisp residents will receive information this spring about the new Cross Connection Control Program, Denham said.
“I believe our biggest defense against a cross-control hazard is having informed residents and everyone watching out for their water system. It’s their water system and everyone has to protect it and use it responsibly,” Denham said.
