Cistern unearthed in downtown Vancouver

Work on replacing a water main in downtown Vancouver was interrupted Monday by the discovery of a water cistern.

The underground brick tank, estimated to be at least 75 years old, measures 12 feet deep and 16 feet in diameter, said Joe Chumley, president of Integrity Excavating and Construction in Battle Ground. His company received the contract from the city of Vancouver to install a new 8-inch water main on Main Street between 12th and 15th streets. Work began March 24.

Monday’s exposure of the cistern was a reminder of the days when storm-water was collected in underground tanks and used for fire suppression, said Loretta Callahan, spokeswoman for the city’s public works department. She estimated the cistern to be 75 to 100 years old.

The discovery of a cistern at 12th and Main streets, which was made by the operator of an excavator, wasn’t entirely unexpected, Chumley said.

The public works department suspected a cistern was in the area, but nobody could pinpoint the spot, Chumley said Monaday, as he waited for concrete mixer trucks from Cemex to arrive.

The plan was to fill the cistern with 90 cubic yards of a type of concrete, Callahan said, and that work began Monday afternoon.

“When working underground in the oldest areas of a city, you can encounter the unexpected,” said Dan Swensen, Vancouver Public Works’ construction and engineering manager. “Over the years, we’ve discovered old trolley lines, wood-stave water lines and wooden telephone conduit buried deep beneath the streets, along with other abandoned infrastructure.”

In fact, a few days ago, workers on the same job found an old trolley track under Main Street at 15th. The trolley from Portland used to run across the Interstate 5 Bridge and up Main Street.

Integrity Excavating and Construction submitted the lowest responsive bid — $238,241 — for the Main Street water main replacement project among eight companies, according to city documents.

Callahan said she’s expecting the materials and labor to fill in the cistern will add $11,000 to the cost of the project, which should be completed by the end of April.