Infrastructure
Addressing Aging Utility Tunnels at Midwestern Universities
By Myles Moran, PE, Project Engineer, RMF Engineering & David Mercer, PE, Principal, RMF Engineering
Our colleges and universities are aging gracefully, but with time, the need for updated infrastructure becomes evident. Higher education institutions are regularly addressing their physical facilities, updating building interiors and exteriors to ensure they continue to meet evolving standards and student expectations. What can’t be overlooked in these improvements is often hidden from plain sight below the surface— the tunnels that house the critical utilities enabling these buildings to function. Underground utility tunnels play a vital role in the continuous functioning of utility services on campus such as steam, chilled water, electricity, domestic water, and telecom systems, housing and protecting the piping and cables necessary to each. They are a tremendous asset for increasing the life span of the many utilities within by allowing for regular inspection and repairs to be performed without the need for excavation and impacts to above ground operations. Like the institutions that sit above these tunnels, many were built over 100 years ago, and due to natural wear and tear are in need or will soon be in need of renovation or retrofit to remain usable for decades to come. Without addressing these aging tunnels, the systems that service the residence halls, academic buildings, recreation centers, and other campus facilities that students, staff, and faculty interact with each day are at risk of failure, where consequences can be more far reaching than the loss of heating and cooling, or a pause in operations. Depending on the system, failure can be hazardous to those on campus and most
certainly maintenance personnel, amplifying the resolve to maintain these critical pieces of infrastructure. Evaluating Aging Tunnels Many of the tunnels built in the late 19th or early 20th century were constructed with brick walls and brick arch tops and are still widely in use today. In fact, a recent structural assessment performed on a university campus by RMF Engineering, Inc. found a stretch of brick tunnel from the 1920s in surprisingly good condition given its age. The mid-20th century witnessed an increasing shift to reinforced concrete for reduced costs and ease of construction, which made it easier for some institutions to invest in these important infrastructure assets. Precast concrete tunnels, cast-in-place concrete tunnels, and brick- walled tunnels with cast-in-place tops are all often encountered in a campus environment, and while some may be in better condition than others, many are in need of some level of repair. Ultimately, some level of rehabilitation to account for degradation over time is inevitable, but it can be accelerated by varying factors depending on locale. In the Midwest, climate and weather conditions play a significant role. Tunnel tops are often very close to the surface, and in many instances double as a sidewalk or bearing surface. With little or no cover, the tunnel structure can be adversely affected by heavy use of salt to mitigate ice and snow in the winter. Over time, this salt will seep into cracks or voids and begin to corrode the steel reinforcement within, causing the concrete structure to delaminate or otherwise deteriorate
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csengineermag.com
Summer 2024
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