Sean C. Morgan
The city of Sweet Home opened bidding last week for Phase IV of its ongoing inflow and infiltration reduction project.
The total project estimate, including engineering and design, will be in the $6 million to $7 million range, said Public Works Director Mike Adams. Sealed bids will be opened by the city on Jan. 13. The project has been broken into 15 parts, which can be dropped according to priority depending on available funding and the price for the project.
The project is supposed to help reduce inflow and infiltration (I&I), which is water that leaks into the sewer system through deteriorating pipes or through cross connections to storm drainage. When the rain is heavy, the I&I can overload the wastewater treatment plant, forcing the bypass of untreated sewage into the South Santiam River.
The city has been operating under an agreement with the Oregon Department of Environmental Qualify for the past decade to reduce I&I and stop bypassing. The deadline was January, but the DEQ is processing an extension to the agreement. The last time the plant bypassed was in March, Adams said.
Phase IV is supposed to be completed within 425 days, he said. Much of the project includes “pipe bursting,” an in-ground process.
“The nice thing about it is we anticipate most of it if not all of it is going to be trenchless technology, which will reduce the amount of disruption,” Adams said. It’s like the difference between arthroscopic surgery and open surgery.
The $5 million the city plans to borrow will ome in interest-free loans from a state revolving loan fund, he said. Additional expenses will be paid from previously approved low-interest loans.
Phases I and II cost about $3.9 million, and Phase III cost about $3.8 million, he said. That leaves about $2.1 million in approved low-interest loan funds.
“The concept is that this is going to be last large system-wide project we’re going to be doing for some time through this process,” Adams said. The anticipated I&I reduction city officials hope to get from this project won’t quite reach the goals, so the next project will focus on the wastewater treatment plant.
The reductions the pipe projects have made will reduce the expansion requirements for the wastewater plant, he said. The city needs to make improvements at the plant regardless of I&I problems, including efficiency improvements, requirements and new technology, as well as a small expansion.
The plant is rated to handle 7 million gallons per day, Adams said. The plant can handle higher flow rates depending on several variables, such as sustained rain and saturation. Once all factors reach a crescendo, the plant will begin bypassing, he said. The plant has successfully handled more than 12 million gallons per day without bypassing.
To demonstrate the variability in how conditions can influence flows, Adams said, Sweet Home recorded 7 inches of rain in November and the plant received 95 million gallons of wastewater. In January, the city recorded 5 inches of rain while processing 101 million gallons of rainwater.
Prior to the start of Phase I, modeling showed peak flows of 22 million gallons per day. After Phase I and Phase II, peak flows were reduced to 15.3 million gallons per day. After Phase III, flow modeling showed a peak flow of 12.7 million gallons per day.
Based on the agreement with the DEQ, the city still must reduce flow rates by 5.7 million gallons per day, Adams said. Phase IV will reduce flows by an estimated 2.5 million gallons per day.
The final 3.2 million gallons per day will be more difficult to stop by repairing pipes, Adams said, and the city will get a bigger bang for its buck by working in the plant.
The Phase IV project area is spread across the city. Most of it will be located in the western part of town, but a couple of areas are in the eastern part of town. Notifications have been sent to property owners in affected areas, which include the following:
n Second and Third avenues.
n Long and 43rd.
n Off Ninth from Elm to Cedar and between Long and Main.
n Long Street south between Ninth and 15th.
n Elm and Mountain View.
n Long and 18th east to Mountain View.
n 1800 block of North Main .
n Osage, Poplar and Quince around 15th.
n Clark Mill and Main.
n Westwood and Sunset.
The project will include the reconstruction of 50,000 feet of 6-inch pipe and larger using pipe bursting; construction of 1,300 feet of new 8-inch sewer pipe by open cut; replacement of 700 service laterals on private and public property; rerouting 20 private service laterals to sewer mains in the public right-of-way; replacement of approximately 150 manholes; and asbestos abatement where concrete sewers are burst and exposed.
For more information about the project, people contact Adams at 367-6243. The plans may be viewed in the city’s Engineering Division, downstairs at City Hall, 1140 12th Ave.