About 200 feet of sewerline where two sinkholes opened up on Royal Hills Drive “is about shot,” according to the Renton’s public works director.

That assessment was made after a camera was carried through the pipeline Friday from the edge of the Tiffany Park neighborhood through roughly the middle of the Royal Hills Apartments.

The city is now considering which of two options it likely will use to repair the pipeline. The repairs could cost 10s of thousands of dollars and could force the city to rethink how it plans to spend its capital-improvement budget.

“That whole section of line has to be replaced and it has to be done sooner rather than later,” said Gregg Zimmerman, the public works administrator.

That first sinkhole opened up in the street’s pavement about mid-day on Thursday, June 3. It was repaired the next day. The second one appeared right next to it on June 9. That opening has been covered with steel plates while the city figures out how to repair the damaged pipeline.

The first sinkhole revealed why sewage gushed from a manhole several hundred feet away, some of which reached the Cedar River. A section of concrete pipeline corroded over time; debris entered at that point and clogged the narrowing pipeline downflow from the break.

There have been no sewage overflows since June 2. Sewer service also has not been disrupted.

Last Friday, the city hooked together hoses to carry sewage around the stretch of sewage line it wanted to inspect. The bypass starts in a manhole on Index Avenue in Tiffany Park, goes down a steep hill and then crosses Royal Hills Drive to another manhole in the apartment complex.

The entire bypass is about 250 feet, including the hill section. The pipeline is in better condition on the hill slope and on the downflow side of the manhole in the apartment complex.

The line and pump were left in place in case they need to be pressed into service again. City crews inspected the lines over the weekend and will continue to do so this week.

The camera was carried through the pipeline using a wheeled carrier belonging to a city contractor. The city has its own on back order.

The camera revealed the cause of the second sinkhole: yet another hole in the pipeline.

Aggregate or small rock is exposed in the concrete pipeline, a sign of corrosion, and gaskets are dangling into the line, which slows the sewage flow, according to Zimmerman.

The city has two alternatives to replace the pipeline.

One is a “shallow replacement” which requires digging a trench four or five feet deep. The current pipeline there is about 16 feet deep.

That option is “much less expensive” than digging down to the failing pipeline, Zimmerman said.

The other option is what’s called pipe-bursting and doesn’t require a trench. In that method, an expanding device breaks apart the pipeline as it moves through it. At the same time, the device is pulling the new plastic pipeline behind it, known as a slip-line pipeline.

The repair, Zimmerman said, “is not going to be inexpensive.” He didn’t have an exact amount, but it could be in the 10s of thousands of dollars.

Because the repairs need to be done soon, Zimmerman said some thought is being given to declaring an emergency. That would allow the city to get the work done without a bid process; however, it would still negotiate a repair cost with a contractor after obtaining cost estimates early this week.

Mayor Denis Law would declare the emergency, subject to City Council approval.