For several years, Environmental Services has worked to stop sewer overflows to South Ash Creek during wet weather. In 2006, the city installed a temporary bypass pipe on the surface near the creek to prevent overflows.
The city is currently working on a project to repair portions of the Ash Creek sewer, remove the temporary pipe and install a permanent sewer line to improve sewer system reliability and stop wet weather overflows to South Ash Creek (see map).
- Construction is ongoing.
- Much of the work on private property in the project area has been completed.
- The CIPP lining process has been completed.
- Crews are working to repair several manholes and prepare to remove the bypass pipe.
- The re-vegetation team will begin working on site in the next several weeks as well as in early 2014 (see map).
Construction is tentatively scheduled to be complete by the end of November. Re-vegetation will be ongoing into early 2014.
Project Overview: Construction Methods
The city’s contractor will use a trenchless repair method called cured-in-place pipe-lining (CIPP) for much of the work. The CIPP process doesn’t require digging a trench and minimizes construction impacts. Work crews use manholes or other access points to insert a flexible liner inside the old pipe. Hot water or steam pumped into the sewer flattens the lining against the inside of the old pipe. The liner gradually hardens to form a rigid, smooth surface. Construction crews will access the pipe via several temporary construction easements along the project alignment.
You are likely to smell a chemical odor during the CIPP lining work. The odor is from a chemical called styrene in the resin liner installed inside the pipe. The odor dissipates quickly once installation is complete. The amount of airborne styrene the repair process produces is not a human health risk.
There will also be about 350 feet of open trench excavation at the west end of the project area to install new pipe that is farther away from the creek. The open trench construction will be on land owned by the City of Portland.
Environmental Services will take care to project private property, water quality and trees and vegetation throughout the project area. When the project is complete, we will replant the city-owned site.
What to expect during Construction
- Construction will create noise, vibration and dust and may disrupt normal neighborhood activity.
- Work hours are 7:00 a.m. to 6:00 p.m. Monday through Friday. The contractor may schedule work during the same hours on Saturdays.
- Traffic control will be in place, and you may be delayed traveling into, out of, or through the work area.
- On-street parking in or near the work area may be prohibited during work hours.
- Equipment and materials may be secured and stored on nearby streets overnight.
- You will have sewer service at all times, even when work is near your home.
- There may be periods of inactivity between construction phases.
- A city construction inspector will be on-site during work hours, and may be able to assist you with construction concerns. Inspectors typically wear a safety vest and hard hat.
The Portland Watershed Management Plan identifies re-vegetation as a key strategy for protecting and improving watershed health. Environmental Services will remove invasive plant species and restore native trees, shrubs and ground cover in the city-owned area that will be disturbed by the sewer construction. Re-vegetation will include follow-up maintenance and ongoing invasive plant control using manual, mechanical and chemical methods.
The old Tualatin Hills Sanitary Sewer District built the Ash Creek sewer in the 1950s. The eight-inch diameter concrete pipe collects sewage from areas north and south of the creek, and from an area south of Interstate 5. It flows east to west and joins the Clean Water Services collection and treatment system west of the city line.
Although it is a sanitary-only sewer, a considerable amount of stormwater enters the pipe through joints and cracks. Because of that, the sewer is too small to handle wet weather flows.
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