About half of North Bend’s permitted sewer system capacity is still available for new connections. Yet the wastewater treatment plant today doesn’t always have that same capacity, a deficiency that has prompted city officials to consider a series of large sewer rate increases over the next five years.

Need for an estimated $27 million in repairs and updates to existing equipment is driving the increases, say city officials, not the anticipation of future growth — new homes and businesses will be paying an increased General Facilities Charges for connecting to the sewer system, as part of the sewer rate increase proposal.

The current facility, with structures dating back to 1951, 1978 and 1995, is adequate for current users as well as the estimated 1,100 new homes to be built in the city in the next few years. However, City Administrator Londi Lindell noted that the city is required to plan for the next 20 years.

The plant was also not up to the challenge of multiple flooding events last November and December that sent millions of gallons of stormwater through the system, creating a peak flow of 3.8 million gallons a day.

The plant is permitted to process 2.58 million gallons of wastewater per day, and averages about 700,000 gallons daily, year-round.

Last December’s peak flow led to a significant spill into the South Fork Snoqualmie River, which resulted in a fine to the city.

The city could also have been cited for exceeding its permitted processing capacity, but “the good news is they only look at a monthly average, so we didn’t violate our permit,” said Lindell, on a tour of the city’s treatment plant with community members July 7.

The tour was followed by a town hall meeting, attended by about 30 people, on the proposed increases.

Various maintenance problems have come up at the plant in the past few years. A new outlet structure, gate and piping for the plant’s oxidation ditch, at a cost of $265,000 was completed in December, 2014.

The plant dryer broke down in 2015, leading the city to get a two-year allowance from the Department of Ecology to dispose of its processed solid waste in a landfill. Full-time plant manager, Mark Fogle, was also hired in 2015.

In January, the council approved another $257,000 for emergency repairs to the plant’s two ultraviolet disinfection units and installation of a third.

The city has also spent almost $100,000 between 2011 and 2013 to address odors from the plant.

“Notwithstanding significant investments, we do not meet regulation,” said Lindell. “When you don’t have redundancy, you violate regulations… Even if we didn’t allow another person to connect to the plant, the rates would go way up.”

City Engineer Don DeBerg affirmed her statement, using the the plant’s 500,000 gallon clarifier, which separates liquid and solid wastes, as an example. “The current clarifier is failing. To fix it, we need to drain the tank…. We need to build another one so we can fix the one we’ve got.”

The plant has two, smaller unused clarifiers, Fogle pointed out on the plant tour, but at only 30,000 gallons each, they can’t be used as backup for the half-million-gallon tank.

“In this day and age, if you were to try to build this plant, Ecology would say ‘no, you need to add a clarifier,'” Fogle said.

The UV equipment expected in a few months will also improve the plant’s redundancy, but before it can be installed, the city will need a new building for it. The concrete building now housing the UV units is very unstable, said DeBerg, pointing out large cracks in the walls.

In addition to equipment updates to repair these problems, Lindell said the rate increase would fund another full-time employee to address a problem outside the plant, inflow and infiltration (I & I) of stormwater. I&I was a primary contributor to the plant’s peak flows in December.

“It’s not like people were flushing their toilets that much,” Lindell said.

The increased water flow came primarily from rainwater, from downspouts tied into the sewer system instead of the stormwater system, and from leaky side sewer connections, allowing water from the saturated ground to seep into pipes.

Another staff person would begin work on reducing inflow and infiltration, by fixing the leaking manholes, and recording video of the sewer plant’s lines to locate and fix other leaks.

Lindell noted that inflow and infiltration is also affecting the plant’s expected capacity, but the extent is unclear. The city is permitted 4,492 ERUs (equivalent residential units, equal to about 2.57 people in a house) and has 2,292 in use, but there are fewer than 2,200 ERUs left within the system.

“When it’s flowing at 3.8 million gallons, you have zero ERUs,” she said.

In the town hall meeting, city staff and consultants covered the list of items that the sewer rates would pay for, which included the new building for the UV system planned for this year, a second clarifier in 2018, and a new electrical building and aerobic digester, to be used in conjunction with the existing 600,000 gallon oxidation ditch, in 2020.

Lindell emphasized that current sewer users would not be paying for growth, just for repairs and replacements. Of the $15.6 million expected from the proposed rate increase, she said 23 percent would come from current users, while 77 percent would be collected from new users connecting to the system.

The proposed increase would establish a base rate that is the same for residential and commercial users, plus a use rate that varies. Rates are proposed to increase 12.7 percent this year, 12.7 percent in 2017, 8.25 percent in 2018, 8.25 percent in 2019 and 8 percent in 2020.

The General Facilities Charge (GFC) for a new house will result in increasing the new connection fee from $5,852 to $10,222 (or to $7,699 if the new home is in the assessment area of ULID 6, which has already paid for a portion of the collection system).

Find the city’s full presentation from the town hall meeting at http://northbendwa.gov/CivicAlerts.aspx?AID=412.

A public hearing on the proposed rate increase will continue through the July 19 meeting of the North Bend City Council, 7 p.m. at the Mount Si Senior Center.