Project Update: Full Steam Ahead for a Tunnel Rehabilitation

Hoyle Tanner is in the construction phase for the rehabilitation of the steam utility tunnel at St. Joseph Hospital in Nashua, New Hampshire. This cast-in-place concrete utility tunnel contains multiple pipes which transport steam from the boiler room into the hospital. Steam is used for all sorts of systems in the hospital so keeping the tunnel in good condition is important for the day-to-day operations of St. Joseph.

During the design phase of this project, it was determined that the top slab of the tunnel was in poor condition and should be entirely replaced. The tunnel sidewalls and bottom slab are in good condition and require only minor repairs. To reduce total project cost and construction duration, new precast concrete panels were designed to replace the existing tunnel roof. As with any rehabilitation project (especially for buried structures like tunnels) minor changes to the contract plans were needed to meet unforeseen or unknown site conditions encountered during construction. Also, a major constraint for this project was to remove and replace the top slab while the existing steam pipes remained in operation. To overcome these challenges, continuous communication between hospital facilities staff, the contractor, and Hoyle Tanner has been essential, especially to determine a practical sequence to remove the existing tunnel roof while keeping the steam pipes undamaged.

At this time, the tunnel top slab has been successfully removed and the new precast panels have been installed. Cast-in-place concrete closure pours are being formed to match up the newprecast concrete to existing structures. The final step before backfilling the tunnel will be to install the all-important waterproofing systems to ensure that the tunnel remains dry during its remaining service life. To find out more about the rehabilitation projects we do, or how we can help your project, reach out to me or see our projects!

Construction progress for the St. Joseph's Steam Utility Tunnel Rehabilitation.

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