Water, sewer and stormwater management rates in Boulder all could go up more than previously planned this year to help pay for flood recovery and infrastructure improvements.

During a discussion Tuesday night of budget planning issues, Boulder Utilities Director Jeff Arthur said his division might ask for water rates to go up 5 percent and for sewer rates to go up 10 percent to pay for infrastructure improvements in the aftermath of September's flooding.

While Boulder maintained its drinking water supply during the floods, unlike some cities, there were widespread sewer backups.

Arthur said assessment of the system is still ongoing, but it seems that most of the backups were caused by "hydraulic constraint," not blockages. That is, too much water in the system.

Every year, Boulder installs an inflatable liner in another four miles of older clay pipes, which significantly reduces water infiltration in the system. With the higher rate increases, the city could line six miles of pipe.

Arthur said the city would prioritize lining pipes in areas that are more vulnerable to backups.

"We don't think it's reasonable to maintain the status quo," he said.

The main pipeline that brings drinking water from the Betasso Treatment Plant in Boulder Canyon has several significant cracks and would be vulnerable in future flooding.

Arthur said the department wants to move up replacement of that pipeline.

Arthur also said stormwater management rates could rise from $8 a month to $13 for the average single-family home.

A formal recommendation based on more detailed analysis of infrastructure needs will be made to the City Council in June.