Sean C. Morgan
The Sweet Home Planning Commission approved a conditional use permit allowing the City of Sweet Home to begin upgrading the city’s Wastewater Treatment Plant.
The city is planning to upgrade the facility to meet state standards, improve the efficiency of the plant and replace aging equipment that is expensive to repair.
After replacing wastewater pipes in four major projects at a cost of $15 million beginning in 2000 to reduce inflow and infiltration, additional projects would have smaller impacts on I&I. The city began planning upgrades to the Wastewater Treatment Plant as a more cost-effective way to handle inflow and infiltration.
Inflow and infiltration is water that flows into the city’s sewer system through deteriorating pipes and cross connections to storm drains. While the city might produce 1 million gallons of water per day, during heavy rainstorms, the sewer system has returned up to 22 million gallons per day to the Wastewater Treatment Plant, which can handle 7 million gallons per day. The vast majority of it is storm water.
The plant cannot handle the flow, and the city would bypass the diluted but untreated wastewater directly into Ames Creek at the South Sanitam River. I&I reduction projects have taken the peak water flows during heavy rains to a maximum 12 million gallons per day.
Public Works Director Greg Springman said the city had a couple of bypasses last winter, but it hasn’t yet this fall and winter.
The plant, built in 1947 and upgraded in 1974 and 1994, needs additional work, he said. In addition to increasing its capacity, the plant needs improvements using newer technology to better manage flows and the microbes used to treat wastewater during dry and wet weather and better debris screening.
“The plant needs a lot of help,” Springman said.
Equipment is old and expensive to repair when it breaks, he said. Mixers used in the aeration basin are no longer manufactured, and parts must be specially manufactured. Of the four, one broke down last week, and it could cost up to $30,000 to repair it. Two are having problems.
Pumps and pipes, which are used to manage the flow of sludge containing microbes used in treatment back to the aeration basin or to a biosolids holding tank for disposal, are leaky, and they share a room with an electrical panel that could shut down the entire plant if it were to go out, according to Steven Haney, plant manager.
At the head of the aeration basin, bar screens have 1-inch and 1.5-inch gaps, allowing debris and trash to move through the system.
The material, which included a Hershey bar wrapper Monday afternoon, can be found floating on top of the clarifiers, where sludge is settled from the treated water, and a little of it finds its way as far as the chlorine contact tank, the last stop on its way back to the river. The material can also clog the system at various points throughout the plant.
Characteristics of wastewater have changed, Springman said. These days, everything gets flushed, resulting in higher levels of plastics and paper products that can form mats and block flows.
The plant also has difficulty handling the amount of biosolid waste it produces. The city is currently repairing and cleaning a basin designed to hold the biosolids, and a temporary hose runs along the parking lot to a temporary 1,000-gallon tank, which feeds a press, which dewaters the biosolid waste.
The biosolids are taken to landfills.
Haney said the press runs longer every day than it used to, and it cannot handle all of the material the plant produces.
The entire biosolids section of the plant will be replaced in the upcoming project, Springman said. The mixers will be replaced by large blowers. New bar screens will have smaller gaps, catching more debris. Equipment will be replaced across the plant.
The project will be confined to the area inside the fenced boundary to the 10.5-acre property, located at 1357 and 1359 Pleasant Valley Road, just south of the Pleasant Valley Boat Ramp and the existing outfall where Ames Creek meets the South Santiam River.
The project should save the city maintenance expenses, Springman said. That money could be set aside for future improvements or to further reduce I&I.
City Senior Engineering Technician Joe Graybill said that the project will be designed in 2018, with construction during 2019 and 2020. By early 2021, the project should be complete or nearly complete.
Initially, city officials talked about completing improvements over a 30-year period, Graybill said, but consolidating it into a shorter time frame makes it more cost-effective.
“The goal is to get as much done up front,” Graybill said, which also will help the city comply with Oregon Department of Environmental Quality rules more quickly.
Consulting firm Brown and Caldwell estimated the cost at $20 million in 2016 and up to $40 million over a 30-year period.
The project will be designed by Murraysmith, a public infrastructure engineering firm with offices in Portland, Eugene and several other Northwest cities.
Springman said he would begin meeting with Murraysmith Tuesday.
The commission voted 6-0 to approve the permit.
Present were Thomas Herb, Greg Stephens, Anay Hausner, Henry Wolthuis, Eva Jurney and Edith Wilcox. Chairman Lance Gatchell was absent.
In other business, the commission approved a variance for Manuel Victor and Stacy Vaughn for 345 18th Ave. to allow a front setback of 12 feet instead of 20 feet and a side setback of 4 feet 8 inches instead of 5 feet.
The variance will allow construction of a garage similar to the neighboring property, replacing a dilapidated carport, which is not large enough to accommodate a vehicle and lacks a paved driveway.
The zone, low-density residential, requires two hard-surfaced parking spaces in addition to the garage. The commission gave a variance from the requirement, allowing the builder to construct a single hard-surfaced parking space in addition to the garage to help keep drivers from parking across the sidewalk due to the short driveway.