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The Dalton at Braddock Gateway

General Contractor:  Clark Construction Group, LLC
Engineer/Architect:  B&A Consulting Engineers
Architect:  SK & I
Contract Amount:  $4,846,614
Contract Start Date:  1/27/16
Contract Completion Date:  1/26/18

Challenges

Braddock Gateway is a new mixed-use project consisting primarily of apartments along with office and retail, located near the Braddock Road Metro in Alexandria, Virginia. The Dalton, a 14-story apartment building (not including two garage levels), is the tallest building in the complex with impressive, unobstructed views of Washington, DC and the Potomac River.

The Dalton’s mechanical system is fairly typical, with the exception of a winterization heat exchanger that is not commonly used in the D-M-V region.  For Shapiro & Duncan’s project team, the biggest challenge was design and construction of the mechanical shafts and mechanical closets interconnecting each apartment to this system. Running from the first floor all the way up to the top floor, these tight mechanical shafts and 260 tiny mechanical closets had to contain the HVAC equipment for each unit as well as the piping for the water heater.

Coordinating all of these mini mechanical rooms up front was time consuming, but it was necessary to make sure that the layout of every single closet was worked out ahead of time with all of the other trades. Not only did we have to make sure that everything would fit, but also that mechanical components would be installed in the right sequence to avoid blocking other trades from doing their work.

Every floor above the first floor had a post-tension concrete deck, which presented a significant construction challenge. Each of these poured concrete slabs had steel tensioning cables running through the center of the slab at 48 inches on center. Once the concrete was poured and the cables are tensioned, we had to be dead-on with our penetrations and sleeves used to run piping from floor to floor through each deck. With very small tolerances, all of our penetrations had to be closely coordinated with other trades requiring slab penetrations and the partition layout.

Solution

There were four key elements to Shapiro & Duncan’s mechanical solution. First, our Virtual Design Coordination (VDC) team, using our advanced Building Information Modeling (BIM) system, created 3D models and coordinated all of the mechanical details of the utility closets. Given the fact that there was not much “wiggle room” in these tiny closets, up-front 3D coordination was a must.

Second, 3D coordination was also essential in getting our slab penetrations lined up ahead of concrete pouring. When it came time to lay out our slab penetrations and embeds, our coordination team relied heavily on technology – in this case, Sokkia Total Station – to confidently locate our penetrations and anchors in the deck exactly, without compromising any of the tensioning cables.

Third, after coordinating most of the mechanical systems in the building, we worked with the general contractor to build an exact mockup of the 260 mechanical closets. This was done in our 51,000-square-foot fabrication shop in Landover, Maryland. While this wasn’t a contract requirement, our management team figured it would be beneficial to give the owner and each of the trades an opportunity to walk the closet layout and see first-hand how tight the tolerances would be. This would allow each trade to speak up ahead of time if they felt any changes were necessary. As it turned out, all of trades did their own component mockups. The proactive problem-solving that resulted from this mockup exercise headed off potential conflicts on the job which could delay the project and add cost.

The fourth and final element of our solution also involved our fabrication shop, which prefabricated most of the mechanical system, including the condenser water supply, return risers, loops and equipment trim packages.

Our complete mechanical solution consisted of one cooling tower, two boilers, four base-mounted pumps and a heat exchanger. These components form an open and closed condenser loop serving 260 apartment heat pumps, as well as the heat pumps in public spaces. In addition, there are a number of fans, unit heaters and two rooftop air handling units (RTUs) that further serve public spaces.

Results

Thanks to the detailed coordination and up-front problem solving facilitated by the Shapiro & Duncan team, coupled with excellent on-the-job supervision by our foreman. The Dalton at Braddock Gateway project ran very smoothly and was completed ahead of schedule. There were very few conflicts during construction, and those were quickly resolved. We had a positive experience with the general contractor, Clark Construction Group, and the result is a happy owner. Successful completion of this project is yet another demonstration of the core competencies that set Shapiro & Duncan apart – our commitment to proactive coordination, our effective use of technology and, most of all, the extraordinary ability of our people.