POST FALLS - Those dam issues can get in the way of construction.

Construction on rebuilding Avista Utilities' 108-year-old South Channel Dam on the Spokane River at Post Falls is two months behind schedule due to an erosion problem on the north bank of the channel, said Mary Jensen, project engineer.

"It was a (worker) safety issue," Jensen said.

The hiccup required a water management plan to be submitted to and approved by the Idaho Department of Environmental Quality.

Jensen described the erosion as a "cave" 10 feet tall, 12 feet wide and 40 feet long, which made working conditions unstable.

Jensen said it's now looking like the $13.5 million project next to Q'emiln Park will be completed in March with landscaping in April and May. She said work will continue throughout the winter, six days a week.

"It's not likely that we'll make up the two months with winter ahead," Jensen said.

Construction on the project began in April.

An observation deck overlooking the dam will be built after construction of the structure is completed.

Jensen said Avista hopes to obtain a permit this week from the Environmental Protection Agency on a water filtration system that will clean contaminated water from the construction zone. The system in the boat launch parking lot includes six 100,000-gallon tanks. The filtered water will be pumped back into the river.

"We appreciate the patience and cooperation of the people who visit the park during construction," said Debbie Simock, Avista spokeswoman.

Jensen said the filtration systems will create some noise during daytime hours.

A temporary dam just upstream from the permanent structure was built to allow workers to perform upgrades. The concrete of the structure is currently being repaired.

In addition to replacing manual equipment, the project includes removing the original 1906 concrete gate frames and adding new concrete and spillway gates.

The project will be funded by ratepayers as part of Avista's capital improvement program.

"It should last another 100 years," Simock said.

The dam is one of three Avista owns at Post Falls. The North Channel Dam was upgraded in 2004 and the Middle Channel Dam was upgraded in 2012.

The South Channel Dam is not used to generate power. It helps lower river and lake levels during the spring runoff season.

The Q'emiln Park boat launch next to the dam closed Monday for the season.