Recurring sinkholes prompt $600K storm drain repair in North Auburn neighborhood

After years of temporary fixes and recurring sinkholes, Placer County supervisors approved a contract Tuesday to repair an aging storm drain in North Auburn, bypassing the usual bidding process as officials warned of further ground collapse and property damage.

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The work along Greenstone Court is expected to take about three months, depending on the weather. County officials said they want to finish before the winter rainy season, when heavy storms could make the problem worse.

The county hired Lorang Bros. Construction to complete the work for $600,000, with help from a company that specializes in repairing underground pipes. Supervisors also authorized up to $42,500 in change orders, bringing the potential contract cost to $642,500.

The county awarded and signed the contract Oct. 6, two weeks before supervisors ratified it at their Tuesday meeting.

Matt Randall, deputy director of Placer County Public Works, said the sinkholes are a symptom of a worsening problem.

The roughly 800-foot metal pipe was installed in 1988 as part of the Pine View subdivision. It carries stormwater through residents’ backyards before draining toward an outlet near Highway 49.

Because the pipe runs through private backyards instead of beneath a public road, accessing it for repairs has been difficult, Randall said.

County crews have responded to sinkholes over the years, making temporary repairs as problems appeared. Over time, the sinkholes became more frequent, and county workers struggled to inspect the entire pipe with their own equipment.

“I think we had done a series of kind of band-aid fixes for years,” Randall said. He said the increasing frequency of the sinkholes and the county’s difficulty inspecting the pipe raised concerns about its condition.

The county’s staff report warned that the deteriorating pipe could cause more ground collapses, damage nearby property and interfere with stormwater drainage. The report did not identify any homes that had been damaged.

County officials initially considered making more temporary repairs before winter and postponing permanent rehabilitation until a later construction season. But after further evaluation with the contractor, they determined both types of work could be completed together, potentially saving money and reducing the risk of further damage, according to the staff report.

Why Placer County bypassed the usual bidding process

Randall said the county chose an informal process to hire the contractor because officials wanted to begin work quickly. A standard bidding process can take two to three months, he said, potentially pushing permanent repairs into the rainy season.

According to the county staff report, delaying repairs for a formal bidding process could increase the risk of additional sinkholes, ground collapse and property damage.

The report also warned that failure to ratify the contract would stop rehabilitation work, leaving the neighborhood vulnerable to further deterioration.

The project is funded by state road maintenance money collected through fuel taxes, rather than the county’s general fund.

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How the storm drain will be repaired

Rather than digging up the entire pipe and disturbing residents’ yards, crews plan to install a new lining inside the existing pipe.

The process, called cured-in-place pipe lining, involves inserting a flexible liner into the old pipe, inflating it and hardening it in place. Once it cures, the liner forms a new pipe inside the old one.

Randall compared the process to inflating a balloon inside a pipe. He said the liner is designed to last up to 50 years.

“It gets blown up like a balloon and cured in place with steam,” Randall said. “Then it hardens, and then it’s basically like you have a new pipe.”

Crews have already used a camera to inspect the pipe and identify damaged areas, Randall said. The camera equipment had difficulty passing through some sections, and workers needed specialized help to complete the inspection.

The project also includes repairing damaged sections of the pipe, filling voids beneath the pipe and stabilizing the surrounding ground. A short section near the road will be excavated and replaced.

The county expects to save money by combining the work into one project rather than handling it in separate stages, Randall said.

The county’s initial estimate for the entire project was $1.5 million, including engineering work, staff time and other costs. Randall said he expects the final cost to come in well below that estimate.

“I think ultimately it’s going to be a cost-effective way of getting it done,” Randall said.

The county also maintains more than 1,000 miles of roads and regularly inspects storm drains and culverts to identify problems before they lead to sinkholes, Randall said.

“We do our best to take care of everything we can before winter comes,” he said.

Randall said the Greenstone Court project is larger than the routine repairs county crews typically handle, but he expressed confidence in the contractors and county staff working on it.

“We do this the right way. We do it once, and it’s good for the future,” he said.

This story was originally published October 22, 2026 at 12:49 PM with the headline “Recurring sinkholes prompt $600K storm drain repair in North Auburn neighborhood.”

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