Centennial Mills

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Centennial Mills 2017-06-23T15:34:56+00:00

Project Description

Centennial Mills

Prosper Portland acquired Centennial Mills from ADM Milling Company in 2000 using urban renewal and City of Portland Bureau of Environmental Services (BES) funds. The property was acquired to fulfill the River District Urban Renewal Plan’s stated objective of enhancing the waterfront with public open spaces and to facilitate connectivity between the River District, the Willamette River and the Willamette River Greenway.

The City relocated the Police Department’s Mounted Patrol Unit (MPU) to the site in 2002 as an interim use due to displacement from their former operating location under the Lovejoy ramp.  In 2006, Prosper Portland with the Bureau of Planning to complete the Centennial Mills Framework Plan which outlines Portland’s interest and aspirations for redevelopment of the site. The framework plan was the result of a six-month public process and was approved by the Portland City Council in December 2006. The plan does not posit particular redevelopment schemes for the property. Rather, it outlines various development opportunities and lays out five key principles to guide redevelopment: Provide Open Space, Capture History, Define a Community Focal Point, Strengthen Connections, and Embrace Sustainability. Redevelopment of the site is also anticipated to advance the goals of the agency’s Strategic Plan.

Between 2006 and 2013, Prosper Portland engaged two different development teams (LAH Holdings and Harsch Investment Properties) to undertake project feasibility work. Unfortunately, both attempts at redevelopment were ultimately deemed infeasible due to a combination of market conditions, technical challenges, and resource constraints.

In December 2014, the Prosper Portland Board adopted Resolution 7089, making an emergency declaration relating to the physical condition of Centennial Mills, and instructed staff to seek a contractor for the selective demolition and salvage of the site’s various buildings. Prosper Portland announced in March 2015 the selection of Tigard, OR-based Northwest Demolition & Dismantling as the Construction Manager/General Contractor (CMGC) for that work.

From April to June 2015, Prosper Portland staff, with assistance from KLK Consulting and Northwest Demolition and Dismantling, performed a series of pre-demolition investigations to determine the scope, schedule, and safety measures necessary for accomplishing the selective demolition of the site.

The Mounted Patrol Unit vacated the site on May 31, 2015, relocating its daily operational offices to the east end of the Hawthorne Bridge.  The horse stables have been relocated to the Lake Oswego Hunt Club.


On July 16, the Prosper Portland Board of Commissioners approved Resolution 7137, beginning the first phase of the selective demolition of Centennial Mills.  While the resolution excluded demolition of the Feed and Flour Mill buildings, the Mayor’s office has requested additional investigation into the costs and feasibility of preserving these structures.

Early preparatory work began on site in August and September 2015.  Work included installation of temporary roadways for heavy equipment, utilities termination and rerouting, artifact salvage, and temporary structural shoring.  During this period, demolition crews witnessed several instances of structural collapse and accelerating deterioration.  Due to the heightened danger, non-demolition personnel are no longer permitted on the Property.

Phase One demolition of Warehouses A, B, C, D, and F as well as Elevators A, B, and C began in fall 2015 and concluded in late spring 2016.

Phase Two of the demolition began in June 2016. The second phase of the selective demolition removed the underlying concrete wharf deck, with the contractor using a floating barge to cut out large sections and then life the pieces onto the upland bank for crushing. Due to the potential for riverine impacts, the phase required oversight by the Army Corps of Engineers, Department of State Lands, and Department of Environmental Quality (DEQ). At the completion of Phase Two, Prosper Portland received a letter of commendation from DEQ for the care taken to protect the environment and the extensive riverbank cleanup completed by the contractor.

As demolition progressed, the foundation of the Feed Mill was finally exposed and accessible to further inspection. Unlike the Flour Mill, which rests firmly upon driven friction piles, the Feed Mill’s foundation only consisted of a shallow stemwall and concrete footings, built on fill material. The team observed a significant difference between the level of the other surrounding foundations and that of the Feed Mill. The assessment was that the building had settled approximately six inches at its northwest corner, resulting in the five-story structure leaning slightly in that direction. This was a significant setback to the feasibility of preserving and restoring the Feed Mill building.

In September 2016, the Prosper Portland Board approved Resolution 7208 by a one-vote margin, authorizing demolition of the Feed Mill building. Demolition of the structure took an additional six months to complete due to a large amount of previously unknown asbestos-containing material being discovered inside the building, as well as large areas of unreinforced structure requiring careful demolition procedures in order to prevent uncontrolled collapse. Demolition of the Feed Mill concluded in March 2017, completing Northwest Demolition and Dismantling’s involvement in the redevelopment efforts.

In March 2017, City Council passed a resolution precluding the return of the Mounted Patrol Unit and approving redevelopment of the entire site. At the meeting, Prosper Portland staff provided City Council with a conceptual program that addressed the principles of the 2006 Framework Plan. The conceptual program includes extension of the greenway trail, public access through the site, mixed-income housing, and renovation of the iconic Flour Mill building.