A once quiet valley, about a half mile northeast of downtown Bentonville, Arkansas, is the scene of intense construction. The Crystal Bridges Museum of American Art, designed by Moshe Safdie, has arisen from the ground, and its buildings are taking shape. Once complete, the museum will become a major tourist attraction in northwest Arkansas.
The architectural concept by Moshe Safdie & Associates required that the Crystal Bridges Museum border, span, and dam two creek-fed ponds. The design took into account the steep valley walls at the site and the desire to protect mature trees and other natural elements; the main construction staging and office area thus are located 1,500 feet away, on other museum property. Temporary offices, lay-down areas, assembly sheds, access roads, and parking are remote, and workers are bussed to the construction zone.
An earthwork platform was constructed over the natural creek to allow for the passage of construction equipment and cranes and the performance of some lay-down and assembly and other activities in close proximity to the construction. This platform will be removed near the end of the construction, and the area will be turned into the upper pond.
The underground construction has included a number of unusual features. A storm sewer was built to take normal low flow from the creek through the site without interrupting construction. This pipe will also serve as a permanent bypass when the ponds are drained for maintenance. Larger flows, however, will wash through the construction site, a risk deemed acceptable but one that will require close attention to weather forecasts.
The Crystal Bridges Museum buildings and ponds are being constructed on top of an existing trunk sanitary sewer (24" in diameter). Relocation of the sewer to a site removed from the ponds and museum buildings was not feasible, so it was relocated a few feet into a pipe chase and was enlarged to account for probable future improvements to the rest of the sewer. The chase size is 10 ' wide by 6' high and runs over 600' and is designed to facilitate maintenance and repair of the sewer (36" in diameter).
Two buildings of the Crystal Bridges Museum that are located directly over the creek, and the creek-fed ponds are part of Safdie's response to the surrounding nature. Safdie's goal is to have the upper pond discharge straight toward the building, then disappear under it. To protect the building and its multimillion dollar contents from flooding, the project includes weirs under the buildings to protect them from, approximately, the 1,000 year flood. These weirs are mostly constructed but cannot be completed until later in the construction, to avoid impeding site traffic.
Early construction activities came close to damaging some trees that were planned to remain. Final grading after construction should adequately protect the trees, but during construction they are at risk. The contractor used soil nailing and shotcrete to stabilize the vertical cut. So far the two trees, dubbed “Thelma and Louise,” are still thriving.
From the public overlook platform, which is part of the Bentonville trails system, the current view is of buildings going up. Construction of the two ponds has also begun, mainly of the impervious liner beneath the ponds. Some of the buildings are topped out; others are getting close. The full scope of the project is mostly visible from the overlook, although upstream and downstream portions are hidden by foliage.
A joint venture, Nabholz Construction Corp./LINEBECK, is constructing the building. As many as 20 subcontractors will be involved at the site before the Crystal Bridges Museum is completed. Construction is progressing at a significant pace, although an opening date has not yet been announced.
A senior engineer and corporate trainer of engineering for CEI Engineering Associates, Inc. David has 36 years of experience as a consulting civil engineer. His experience includes water, wastewater, stormwater, roads, and solid waste infrastructure. For much of the last 20 years he has been involved with stormwater issues. Specifications and construction administration have been a specialty of his within civil consulting engineering . He has BS and MS degrees in Civil Engineering, is a registered engineer in four states, and a Certified Professional in Erosion and Sediment Control.