A ruptured valve on Tualatin's main water transmission line left the city with about a day's worth of drinking water before crews welded the pipe shut Aug. 25.

Public Works Director Rachel Sykes told Tualatin Life that staff discovered an overflowing manhole on 72nd Avenue in Tigard on the morning of Monday, Aug. 24. They found a 2-inch hole in the city's transmission line, caused by a failed air relief valve.

"It was getting worse by the minute … we figured we needed some pretty quick mobilization," Sykes said.

The transmission line carries water from the City of Portland through 60 miles of pipe beneath Tigard. It was built in the late 1970s. Because the leak could not be plugged with water still in the pipe, crews spent about 12 hours draining a 3,000-foot segment before they could begin the repair.

During that window, Tualatin relied entirely on its reservoirs. Those reservoirs hold a maximum of about 16 million gallons, but summer demand runs roughly 9 million gallons per day, double the city's average of 4.5 million gallons. Sykes said the city had about a day's worth of water remaining.

The city issued its first conservation notice at 2 p.m. Aug. 24, asking residents and businesses to halt all outdoor watering, vehicle washing and pool filling. As we reported Aug. 26, the city also asked residents to shorten showers and reduce indoor use.

Tigard's Water Division and the Tualatin Valley Water District (TVWD) assisted at the scene. Rivergrove Water District and the City of Sherwood supplied Tualatin with additional water while the line was down.

Crews welded a steel cap over the failed valve and restored the pipe to service by about 7 p.m. Tuesday, Aug. 25. By Wednesday, Aug. 26, water was flowing back into the city's reservoirs. Sykes said the conservation request remained in effect through Thursday, Aug. 27.

Sykes said she had never seen a similar failure in her five years with the city. She said the incident raises questions about the condition of smaller components, such as air relief valves, along the entire transmission line and that the city may need to assess them more closely.

No formal timeline for that assessment has been announced.