Workers from Sargent install under-drain pipes as part of an ongoing project to build wastewater storage tanks alongside Back Cove. Ben McCanna/Staff Photographer

A stormwater retention project the city of Portland has been working on since 2019 is almost done after more than two years of delays, 10 contract amendments and $1 million in unexpected costs.

The Back Cove South Storage Conduit project is part of an extended effort by the city to reduce the amount of raw sewage and polluted stormwater runoff being discharged into the cove. The project was supposed to be complete by September 2022, but unexpected issues with the soil in the area delayed the work by more than two years, ultimately costing about $1 million more than planned.

The project is funded by wastewater fees, which are based on water usage by homeowners and businesses. In order to build the storage tanks that will alleviate the strain on a dated sewer and stormwater runoff system, the city dug up the soccer field that once sat between the Back Cove trail and Interstate 295 and has been building tanks underground.

Project leaders say they don’t expect to have the soccer field up and running again until next summer, even though the project will be mostly done by the end of November because by then it will be too late in the season to put in the field.

“People ask all the time. They say they’re on the trail but they don’t see anything happening on the project. Well it’s been happening, but everyone is down in the hole working,” said Brad Roland, a senior project engineer with the city’s public works department.

Roland said the site will be all closed up, cleaned and left as a dirt lot for the winter. Then in the spring, workers will come back to lay sod and sand and install landscaping.

By next July, the soccer field will be back with the addition of an obstacle course looping around the edge of the field, he said.

The field and the section of the Back Cove trail along the field will be rebuilt 2-3 feet higher than they are now to shore up the area against future storms and rising sea levels, he said.

Construction of wastewater storage tanks alongside Back Cove has taken two years longer than expected and driven up costs by $1 million. Ben McCanna/Staff Photographer

THE PROJECT

Since 2020, the space that was once a bustling soccer field between the Back Cove trail and I-295 has been transformed into a construction site. The grass field is gone and in its place are excavators and trucks and a few big holes.

During a site visit last week, Roland tromped through the muddy site under a clear blue sky. He pointed to the large tanks, built about 40 feet underground. Crews were getting ready to bury them.

The city moves sewage and stormwater runoff around the city using a combined method, but when the city gets an inch or more of rain, it creates too much water for the system to store. That extra water is then dumped into the Back Cove. City officials estimate that the current system dumps hundreds of millions of gallons into the cove each year.

“It’s better for the environment and for the people in the neighborhood if we can limit that as much as possible,” Roland said.

A series of projects have aimed to tackle that issue by building large underground storage tanks to store extra wastewater until the rain stops and the system is no longer overwhelmed. Then it can be diverted back into the system, rather than being dumped into the cove.

The effort began in 2013 with the construction of storage tanks under Baxter Boulevard and Payson Park. Then, more tanks were built on Baxter Boulevard near Vannah Street. The Back Cove South project is the last one on the list.

Once completed, it is expected to reduce the amount of wastewater dumped into the Back Cove by about 80 million gallons. Roland said he is hopeful more storage tanks can be constructed going forward so that eventually, no wastewater will be dumped there.

Glenn Adams, a project manager for Sargent, stands on the grounds of an ongoing project to build wastewater storage tanks alongside Back Cove. The project has taken two years longer than originally planned. Ben McCanna/Staff Photographer

WHAT WENT WRONG 

The construction contract was awarded to Sargent Corporation in 2019 and was slated to cost $41 million. In the more than four years since, the contract has been amended 10 times to reflect additional work and the new anticipated project cost is $42 million, according to the city.

Those delays and extra costs can mostly be chalked up to an issue with the soil when workers started digging to build the tanks, said Glenn Adams, a project manager with Sargent.

The project called for 3.5 million gallons of new wastewater storage. To construct those massive tanks, workers dug two, large deep holes in order to build the tanks deep underground. Shortly after they were excavated, the wall on the side of one of the holes began to move. It appeared to be unstable and Adams said he became concerned that it might cave in with workers inside.

Adams said it took them a while to figure out how to remedy the problem.

“We couldn’t send workers in there because it wasn’t safe,” he said.

Eventually, they decided to use a method called jet grouting to strengthen the soil. They had to close up the hole and then drill deep down into it and apply high-pressure jets to condense the soil, making it solid enough to hold up, Adams said. Then they dug the hole again and began work on the second tank.

In all, it delayed the project by 18 months.

“There was just no way around it, we had to make sure it was safe before sending anyone down there,” said Adams.