Sewer study raises concerns

HBH conducted a two year infiltration and inflow (I&I) study to determine areas where storm water is breaching sewer pipes. The study was conducted on the northeast corner of the city. This area has a higher concentration of lead or clay pies that are in need of replacement. HBH was hired in 2021 and mainly works with small to medium sized municipalities around Oregon, Washington and California.

According to the study, I&I happens “due to cross connections, pipe cracks, pipe breaks, and root damage to both storm and sanitary sewer pipes, ground water and storm water is allowed to access the sanitary sewer system.”

More specifically, inflow occurs when water directly enters the sewer system through storm water cross connections and illegal connections. Infiltration is water that enters the system from groundwater through broken pipes, cracks and manholes.

Currently, the Waster Water Treatment Plant has a maximum capacity of 3 million gallons per day. According to the city’s website, the average amount processed reaches a little more than a third of its capacity with 1 million gallons per day. I&I not only affects the water levels in the treatment plant, but excess storm water dramatically increase or decrease the pH levels. In turn this alters plant operations and adherence by the Department of Environmental Quality’s guidelines.

The Waste Water Treatment Plant, located in the Waterfront district, has been slated for upgrades for a few years now. Rice said replacement of century old clay pipes could delay the costly expansion.

In order to determine what area of pipes need replaced the most, HBH had three different approaches.

Nighttime monitoring was done between the hours of 1-5 a.m. — the times when most sewer flows were mostly I&I.

Closed captioned television footage was also recorded from pipelines. A robotic vehicle was sent down to inspect and collect visual imagery. Due to obstacles throughout the pipelines, mobility was limited, but Rice and Jennings agreed that this was the most helpful form of observation.

“Some spots we couldn’t get to because of root penetrations,” said Rice.

“If it’s that bad you pretty much know it should be replaced,” added Jennings.

Smoke testing was completed to find spots where cracks and breaks could be present. If smoke was observed to be emitting from the ground that signified there might be a section of pipe that is damaged.

HBH prioritized which pipes need to be replaced and Jennings provided a cost estimate for the Capital Improvement Plan. To replace every section would cost upwards of almost $32 million. “Something to note with the costs presented, that is the total cost for all pipes in each category,” said Jennings, adding the price tag includes the replacing he entire width of street and doing ADA improvements for every single project.