It’s been 21 days since one of the busiest intersections in town closed for the start of the latest combined sewer overflow project.

But after three weeks of detours, it is open again, as of Monday afternoon.

Next up: the remainder of Eighth Street, closing approximately one block a week until reaching Niagara Avenue.

Public Works Director Ken Cook called it the biggest single project in this phase of the CSO.

“We’re installing sewer and water lines in certain sections,” Cook said. “The street is already torn up between Duane and Exchange Street so they will start moving up the hill.”

The project is also moving east, stretching in various areas through 12th Street.

The bulk of the project, Cook said, will be done by the end of October.

Add some finishing touches, and the city’s sewer and water lines will be separated and the streets will be repaved by the end of November or beginning of December.

The separation is a federal mandate to prevent sewage from overflowing into the Columbia River.

This project is expected to cost around $6 million.