The University of Minnesota retained Braun Intertec to be part of the design and construction team to transform and renovate the 75-year old Walter Library into a code-compliant, modern, digital-technology-driven facility.

The project was particularly unique because the building is on the national list of historic places so the exterior had to remain generally unchanged. To transform the building, the massive volume of archived books and manuscripts were relocated to the new Minnesota Library Access Center or the Elmer L. Anderson Library. Once this was done, the center of the west wall was removed and the core of the building, from the roof to the basement was removed and replaced with modern elements that blended with the historic feel of the library that would provide a welcoming ambiance to U of M students, staff and alumni.

We are fortunate to have come into this project with a solid knowledge of University of Minnesota requirements, and a working and professional relationship with the design and construction team.

Challenges

Historic photos, original drawings and the geotechnical evaluation showed the Library had been supported directly on the Decorah shale that exists in isolated areas across the Minneapolis campus. As a result, there was a strong desire to support the new construction also on the shale. This created special geotechnical challenges because of the variable weathered zones within the shale, the unweathered zones and the thick and thin, continuous and isolated limestone stringers with in the shale. Confirming the design bearing pressure was available was critical.

Whenever old structures are updated to new standards, the structural properties of the in place components must be defined. Because of the age of Walter Library, it was necessary to define the engineering properties of the in place floor slab concrete and the type, size and strength of the reinforcement, as these components could not be adversely affected by new construction.

With construction under way, daily challenges occurred even though construction drawings of the building were available. As the general renovation continues forward, many areas were exposed that didn’t quite conform to the details shown in the plans. When these areas were found, the construction team worked together to develop solutions to keep the project moving forward. A few examples of these types of events are discussed in the following.

When the roof was being replaced, the large stone parapet walls were found to have undergone various degrees of distress and displacement over the years because of water infiltration and frost action.

Another occurred when it was found that most of the drains in the area wells were installed so that any water collected in the wells would drain directly into the lower level of the Library. The original solution was to channel the water to area floor drains. This solution was not acceptable given everyone’s strong desire to keep water out of Walter Library. To the surprise of many, an underground flow of water was also discovered below the Library. More water to deal wi

Solutions

The challenges of this project required that all departments of Braun Intertec be tapped for their knowledge and expertise. Groups involved included the Field Services group, the Building Sciences group, the NDE group, the Geotechnical group, the Analytical Laboratory group and Environmental Consulting group.

As the Decorah shale was exposed, a program that used dynamic cone penetrometers, static cone penetrometers, pocket penetration penetrometer and hand auger borings were used to evaluate the shale. These evaluations proved effected and were used to establish guidelines for shale removal and subcut depths. Concrete cores from the in place concrete were removed for compressive strength testing and dry unit weight testing of the slab concrete. A program to exposure, remove and determine the yield strength of the reinforcement bars was also initiated to define the properties of the existing reinforcement for the project structural engineers, Meyer, Borgman and Johnson.

Another challenge arose when it was discovered the large stone blocks that makeup the roof’s parapet wall had, to varying degrees, become unstable. After a detailed review by the Building Sciences group, the decision was made to remove many of the mortar plugs that covered the rusted and sometimes broken, stone block hold down anchors, remove and replaced them as needed, and then re-mortar the plugs. The joints and cracks in the stones were also retooled and sealed. When done, there was a comfortable level that the stone parapet wall would be in place for another 75 years.

We studied the operation of the underground drainage system around the building with remote cameras and test floods. After viewing broken pipes and lots of critters in the pipes, a below slab drainage system was installed to collect the water from the outside area wells and the underground "stream." The drainage system routed the water to several sump pits in the basement. From the pits, it was pumped to the sewer system. For the first time in many years, the lower level of Walter Library was dry.

Unlike new projects where everything is new, renovations create special needs for the construction team. For this project, we assigned one of our most experienced special inspectors to oversee our field services and to track the 100’s of information request forms, project modifications and project directives. He was given the latitude to focus as much effort as needed to meet the needs of the project, the University, Mortenson, who acted as the general contractor, the design team and the University code officials.

When You Visit

As part of your next visit to the University, plan to take some time and see the restored grandeur of Walter Library. As you walk from hall to hall, don’t forget to look up and marvel at the restored ceilings. During the renovation, layers of grit, grime and paint were removed down to the original surface that was fully restored. Craftsmen from around the country were employed to recreate the 75-year-old beautiful artwork and detail. Look at the light fixtures in the great halls. These are replicas of the original fixtures that can be seen in many of the historic photos throughout the Library.

The wall carvings around the Library are generally not noticed by most, but they add an architectural detail to the building that is not typically seen in modern buildings. One feature detailed in the carvings designed by the original architect, is the owls. Searching and finding nearly a 100 of the now famous "Walter Library Owls" presents a challenge to visitors. Next time, take a look and see how many you can spot, because they have already spotted you!