Sewage was to start flowing through a newly repaired sewerline on Benson Hill today (Friday) after a contractor replaced one that had corroded near the Royal Hills Apartments.

The City of Renton also is taking a closer look at a long-standing plan to relocate that sewerline, including moving it around the apartment complex, rather than through it.

“It’s better to not have it there,” said Gregg Zimmerman, the city’s public works director, of the underground pipeline in the complex.

The apartment buildings stand on posts, rather than foundations. Two 16-foot sinkholes had opened up on the street in front of the complex.

The contractor, Shoreline Construction, met the City of Renton’s goal to finish the work today. Late afternoon, the contractor was planning to pave Royal Hills Drive.

Once sewage began flowing again, a city crew on Index Avenue Northeast in the Tiffany Park neighborhood would shut down a bypass that carried sewage around the failed sewerline in about 1,000 feet of connected hoses.

The city replaced about 200 feet of concrete pipeline with a 20-inch plastic pipe that resists the type of corrosion that occurs in aging concrete pipes. The contractor dug a trench roughly eight feet deep in an easement through the complex for the new pipeline.

The cost of the project is estimated at between $100,000 and $125,000. The sewerline is shared with the Soos Creek Water and Sewer District, which has agreed to share in the repair costs, Zimmerman said.

How much Renton and Soos Creek each pay is based on the percentage of sewage contributed to the line, he said.

The contractor was to return Monday for some finishing work, but Royal Hills Drive was to reopen today. During repair work the street was closed, sending Metro and school buses and apartment traffic through the complex.

Royal Hills Drive only serves the large low-income apartment complex, where it dead-ends.

Power was accidently cut to the Windsor Hills area and elsewhere Wednesday afternoon when a crew working on the pipeline cut an unrecorded underground power line that cut across the pipeline, said Zimmerman.

Power was restored to all customers by about 11 p.m., he said.

The city used a camera mounted on a carrier to inspect the pipeline before the repair work. More such inspections are planned to determine whether there are other deteriorated parts of the pipeline, Zimmerman said.

What the city finds will help determine how soon it may relocate the pipeline, he said. Concrete pipelines typically last between 50 and 70 years. This pipeline is 47 years old.

Now is the time to consider relocating the sewerline if it has to be repaired, he said.

The need for the repair work was prompted by two sinkholes that opened up in Royal Hills Drive earlier this month. The first sinkhole revealed a corroded section of pipeline that was the entry point for debris that clogged the pipeline further downstream. That clog forced sewage up a manhole, some of which likely reached the Cedar River