City of Lake Oswego - Lake Oswego Interceptor Sewer - Greater than $75 Million - Environmental (Water, Wastewater, Stormwater) (pictured from right, Mark Briggs, Brown & Caldwell and Joel Komarek, City of Lake Oswego accept the Project of the Year Environmental (more than $75 million) from APWA National President Elizabeth Treadway)
Receiving an award in the Environmental category, Lake Oswego is identified as the managing agency, Advanced American Construction is identified as the primary contractor and Brown and Caldwell is identified as the primary consultant.
The project involved the installation of more than 29,000 feet of new pipe, 18 inches to 42 inches in diameter. The sewer itself is configured in a serpentine alignment with thermal expansion loops that maintain grade despite wide-ranging water temperatures. The sewer is held to proper grade beneath the lake surface by 428 ground anchors and tethers that are fastened into solid bedrock beneath a thick, soft sediment layer at the lake bottom. For maintenance and cleaning purposes, submerged buoyant stainless steel manholes were installed along the pipeline, with access via removable aluminum caissons.
The $100 million project was completed on time and 10 percent under budget, and the gravity system will save an estimated $20 million in operations and maintenance costs during its service life. The in-lake gravity sewer eliminated the need to build six pumping stations and reduced the pipe length by 40 percent, compared to a land-based system, which provides a direct route with less material consumption, reduced use of heavy construction equipment, and fewer visits from utility maintenance trucks throughout its service life. Numerous project challenges included: difficult topography and geology very soft sediment up to 200 feet thick overlying basalt; flat grades on the existing system; lack of access/staging sites; private lake ownership, high visibility and high consequence of failure; high HDPE thermal expansion; and future draw-downs.
The project was constructed under two major contracts, titled Lake Full and Lake Down. Lake Full was a marine, barge-based project in which all ground anchors, tethers, sewer pipe, buoyancy pipe, and piles were installed. Lake Down was a more conventional land-based project, although on a soft lake bed, in which excavation, construction, and restoration for some final pipe replacement and junction structures were performed. Lake Down included lake level control and substantial flow diversion. The conventional project delivery method of design-bid-build was employed for both major contracts. The whole system has performed well since coming online in June, 2011.
City of Tigard - SW Burnham Street Improvements - $5 Million but less than $25 Million
Receiving an award in the Transportation category, Tigard is identified as the managing agency, Kodiak Pacific Construction is identified as the primary contractor and Otak, Inc. is identified as the primary consultant.
This project supports the revitalization of downtown Tigard by remaking Burnham Street into the City’s first Green Street. Features along Burnham include widened sidewalks with flow-through stormwater planters, “state of the art” low-energy street lighting, pedestrian crossing enhancements and complete undergrounding of aerial utilities.