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Pillsbury A-Mill Tunnel Historic and Engineering Condition Study

Background

The Pillsbury A-Mill is one of only 25 National Historic Landmarks in the state and one of the most notable structures on the Minneapolis riverfront. On October 10, 2013, the A-Mill property and the tunnel system below it was purchased by Dominium.

At this time, Dominium is renovating the historic complex into affordable artist apartments that will be called the A-Mill Artist Lofts. The complex will feature 251 units.

There is a strong interest by the City of Minneapolis, Dominium, and the St. Anthony Falls Heritage Board to preserve the tunnel system below the A-Mill and find ways to explain its significance to the public. The A-Mill tunnel system contains three main pieces 1) the headrace that brings water from the Mississippi River under Main Street to under the A-Mill, 2) two drop shafts in the basement of the A-Mill building, and 3) two tail races that bring water back out into the river below the falls.

Pillsbury A-Mill Tunnel System Study

In order to preserve the tunnel system, we first had to learn more about it. So, in partnership with Dominium, the City of Minneapolis has completed a study of the historic and structural condition of the A Mill tunnel system.

The study was funded by grants of $250,000 from the Minnesota Historical and Cultural Heritage Grant program and $35,000 from the St. Anthony Falls Heritage Board, with matching contributions from Dominium and the City of Minneapolis.

The project included two general phases. In the first phase, Dominium completed a package of preparatory work to open the tunnel system and make it safer for consultants to access. Weis Builders oversaw this work, with Lametti and Sons and Medina Electric as subcontractors.

In the second phase of work, a consultant team led by Mead & Hunt completed the actual condition study. In addition to Mead & Hunt (historical research and evaluation), the team included CNA Consulting Engineers (structural and engineering evaluation), 10,000 Lakes Archaeology, Inc. (archaeological fieldwork plan), Rani Engineering (survey/engineering) and Arch3, LLC (photography).

Study Outcomes

As a result of the study, the City and its partners have a much better understanding of the various components of the tunnel system and how they functioned together, as well as more knowledge about the history of this historically significant site. One outcome of the study was the preparation of Historic American Buildings Survey documentation including plans and large-format photos that has been submitted to the National Park Service as a permanent record of the system.

The parties also have much more extensive information about the physical condition of the system, its dimensions and materials and its potential for future use. The study found that the system is in relatively good condition for its age (130+ years) and is largely intact from a historic point of view. While the system will need maintenance to prepare it for use and then will need ongoing maintenance, nothing was found that would preclude its use.

Possible future uses include using the water running through the tunnel system for hydrothermal heating and cooling of the entire A-Mill Artist Lofts development, as well as hydroelectric power generation to meet a portion of the project’s needs.

There also is interest in creating public access to some or all of the tunnel system to allow historic interpretation. The 2013 east bank interpretive vision completed by the St. Anthony Falls Heritage Board highlighted the dramatic potential and high priority of helping the public understand the key role that this tunnel system played in making Minneapolis the flour milling capital of the world from 1880 to 1930. In order to explore the practical feasibility of creating safe public access into the tunnel system, the St. Anthony Falls Heritage Board has funded a feasibility study.

No Public Tunnel Access

Dominium has secured the tunnel system to reduce the ability of “urban explorers” to access parts of the system, at great danger to themselves and the historic resource. The entire system is considered a “confined space” under OSHA definitions and may not be accessed except by parties with the necessary confined spaces training and equipment, accompanied by a rescue team.

 

Last updated Jul 1, 2014