$200,000 Department of Environmental Quality funding fuels study for city's future needs

FILE PHOTO - The existing wastewater treatement plant in Sandy was built in the 1990s based on a projected population of 11,100 residents. As Sandy's population rises above 12,000, the city is reaching the end of the planning process for a new or renovated wastewater treatment plant designed to handle the ongoing influx of residents

The current plant was built in 1998, when it was only responsible for serving just over 5,000 people.

"We need the new plan to serve new growth," Public Works Director Mike Walker told The Post in a previous interview. "These things only last so long, (so) you try to kind of match (its capacity) to your growth horizon."

The planning of the project is partially funded by a loan of $200,000 from the Department of Environmental Quality.

The plan will evaluate the circa-1998 plant and look at the newly completed urban growth boundary expansion and land-use planning to determine what work needs to be done.

The existing facility was built based on a projected population of 11,100 people, but Walker said it should be fit to service the city until expansions can be completed.

"It's not a hard-and-fast thing," Walker explained. "It's not like when we get to 11,099 we can only get one more person, but we need to plan for the future."

In December the city solicited bids and granted the contract to complete the facilities plan to Murraysmith, a Portland-based engineering firm.

Since then the firm has completed flow monitoring endeavors in the plant's collection system and worked to assess the needs of the structure. The city could be able to renovate the plant, or it could need to completely rebuild. The plan will give staff an idea of which route will be necessary.

Unfortunately, for planning's sake, there wasn't much rainfall while Murraysmith was monitoring the flow of the facility, but with the help of historic data, he hopes the city will have a clearer picture of its wastewater treatment needs by the end of September.

"Ideally you want to catch some big rainfall events while monitoring," he said. "(The firm) has demonstrated that we have a lot of rainwater that gets into our system, and that affects (the capacity of the plant). Sometimes rainfall can account for double or more the capacity of the plant."

This abundance of rainwater flooding the facility in wet months has led to multiple DEQ violations in the past year.

Once the plan is completed the city will know the cost of the renovations or building and will hire a consultant by April 2019 to design the next facility.

November 2021 is the deadline by DEQ for completion of the rebuild or renovation, and the next facility is required to fulfill a 20-year planning horizon, maxing out at a projected population of 22,000.

"We might not be able to afford the 20-year model," Walker admitted. "So, we might have to phase it out. Some of this is driven by growth. Some of it is an existing problem with the pipes we can't charge new development for and some of it is attributed to growth, which we can't charge existing residents for. We have to find some equitable way to distribute costs."

Those costs will most likely appear in the form of rate increases and connection fees, all dependent on the total cost of the project. But the concern over the plant's capacity pushes the project and possible increases forward.

"We are concerned the plant won't (remain fully functional until the project is complete)," Walker said. "It will be a challenge over the next three years if the population continues to grow as it has. We're trying to keep everything running the best we can."

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