With floodwaters, mud and debris filling Boulder County sewer pipelines — and manholes underwater and inaccessible — the city of Boulder was, by Sunday, receiving a barrage of citizen reports of water or sewage backing up into homes.

“What we’re seeing most is it’s floodwaters overwhelming the sanitary sewer system,” said Boulder Public Works spokesman Mike Banuelos. “It’s coming through the grates. That’s a lot of what people are seeing. In some cases, it might be sewage backing up into homes. In those cases, we’re asking people to evacuate because it’s a health issue.”

University of Colorado police also blocked off a footpath on east campus, north of the Space Science Building, where a broken sewer line was spilling Sunday evening.

“It’s not near any classrooms or dorms — it’s an almost rural area of campus,” said CU police spokesman Ryan Huff. “Facilities managers are aware of it.”

Boulder officials are asking residents to report any raw sewage backing up into their homes by calling the Emergency Call Center at 303-413-7730 and asking it to forward the report to Public Works crews.

Boulder is also asking residents to minimize water use, including flushing toilets and discharging anything more into the sewer system.

In the city of Evans and environs in Weld County, a no-flush order is in effect because floodwaters have damaged the First Avenue Waste Water Treatment Plant. While drinking water is still safe to drink, city officials said, they are asking residents to refrain from all uses of the wastewater system. This means no flushing of toilets, no laundry, no baths or showers, and no washing dishes.

The city planned to distribute some portable potties to affected areas over the weekend.

For those interested in their own do-it-yourself sanitation, Public Works officials don’t recommend burying solid waste in your yard. Residents could, however, borrow a page from outdoor enthusiasts who routinely use portable toilet systems.

The Bureau of Land Management advises that toilet systems consist of some type of sturdy, leak-proof container with either a liquid or dry base material designed to reduce odor until the material can be dumped.

Single-use individual bag products are available — typically a heavy-duty bag with a seal that contains an odor-neutralizing powder. Such bags can be sent to the landfill.

To address the system-wide sanitation issues in Boulder, officials said, they must work in low-lying areas first because waste flows downhill to the wastewater treatment plant on 75th Street east of the city. But first floodwaters must recede. In a release Sunday, Public Works said it hopes to see “significant progress in the next few days.”

Electa Draper: 303-954-1276, edraper@denverpost.com or twitter.com/electadraper