PORTLAND, Ore. (AP) — Officials say barges carrying wheat, wood and other goods will remain at a standstill for the rest of the month while workers repair a critical navigation lock at the Bonneville Dam on the Columbia River.

The Portland District, U.S. Army Corps of Engineers said Wednesday the locks will reopen Sept. 30. The navigation lock was closed Thursday after operators detected problems and further investigation revealed cracked concrete.

The closure comes during wheat harvest.

Portland District Commander Col. Aaron Dorf says teams will be working around the clock until the repairs are finished.

The Bonneville Dam is the first in a series of eight dams on the Columbia and Snake Rivers, which together make up a watery highway for goods flowing into and out of the region from the Pacific Rim.