Air Bubble in Interceptor Causes Release of Wastewater
March 8, 2011
LAKE OSWEGO - At approximately 5:30 a.m. today, high level alarms installed in the Lake Oswego Interceptor Sewer (LOIS) system alerted workers to high wastewater level ("surcharge") conditions within the partially completed LOIS system. An immediate response by the City's Contractor, James W. Fowler, its by-pass pumping subcontractor, Godwin Pumps, along with assistance by marine support subcontractor, Advanced American Construction, and Engineer Brown and Caldwell is underway. The cause of the surcharge appears to be caused by air entering the pipe as it comes on grade with the refilling of Oswego Lake and then accumulating at high points in the pipe. The high points were created when the Contractor intentionally pulled down sections of the floating pipe to allow barges and other marine equipment to move back and forth across the pipe path to access and construct the north shore trunk lines and manholes. Over time, enough air has accumulated at these high points to create a "bubble" that is reducing the capacity of the LOIS pipeline. Efforts are underway to "vent" the entrained air from the LOIS pipe and restore full capacity while work continues to complete the project over the next few months.Release of wastewater to the lake bed has occurred at locations of temporary connections west of Springbrook Creek and at a location a few hundred feet north of Allen Road. Contractor personnel have implemented containment and collection procedures concurrent with efforts to remove air from the pipeline. These efforts will continue until the surcharge conditions have been abated. Lake Oswego Corporation and all other appropriate regulatory agencies have been notified of the release. The City's Pollution Liability Insurance carrier has also been notified. The volume of the release has not yet been determined.
Since November 2010, uninterrupted sewer service during this final phase of the LOIS project, has been possible through the use of an extensive system of by-pass pumping equipment. These systems include redundant pumps and alarm systems that automatically dial emergency phone numbers in the event of a pump failure or other situation that could potentially result in a release. In addition to these systems, each by-pass pumping installation is monitored around the clock by Godwin employees. Without such systems in place, the project could not have been completed. While this event is unfortunate, particularly when the project as a whole has been a resounding success both in terms of being under budget and being completed on time, proper safeguards and response protocols were in place and worked successfully to minimize the uncontrolled release of wastewater during construction.
This text excerpted from a City of Lake Oswego press release (pdf, 81 kb) issued on 3/8/2011.