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2017WinterShotcreteEMag

2016 Outstanding Architecture | New Construction Project Elephant Lands By John Fulford Controversy surrounding keeping large mammals in zoos has recently increased in the zoological community. The Oregon Zoo responded strongly and positively to this challenge by dedicating six acres (24,000 m2) of their facility to the most ambitious and largest exhibit built in their 128-year history: “Elephant Lands.” With the health and welfare of the Portland community’s beloved elephants as the guiding principle, a world-class exhibit was constructed over the course of 3 years, all while the popular herd was kept on view to the public through a complicated series of construction phases. The result is a robust habitat that keeps the six elephants of the Oregon Zoo’s herd mentally and physically active with abundant behavioral enrichment opportunities (such as mud wallows and a 160,000 gal. 605,000 L3 pool for swimming and cavorting) while providing the public with an exciting and enriching experience that honors these magnificent animals. This $57 million project was designed by CLR, a Philadelphia based architectural firm that is widely known and highly regarded in the zoo construction industry. The innovative engineering of the project’s shotcrete elements was performed by Armour Unsderfer Engineering, and the General Contractor/Construction Manager for the project was Lease Crutcher Lewis, one of the Pacific Northwest’s premier builders. The Turnstone Construction, Inc., crew had the pleasure of building the previous home for these elephants back in 1992, and so we were happily aware of some of the habits and personalities of these behemoths. We knew that Packy, the 54-year-old patriarch, enjoyed rubbing his belly on rocks with striated rib-like textures at about 4 ft (1.2 m) above grade. We also knew that the removal of the existing work to make way for the new exhibit would entail patience and heavy equipment. We happily left that work to a demolition contractor who exclaimed, “We had no idea concrete could get that hard,” as they spent weeks breaking apart the old shotcrete rockwork and pool. Shotcrete structures held up to their notoriety as the strongest concrete in the zoo! This was the fourth elephant exhibit Turnstone had constructed, which allowed us to participate in preconstruction meetings with the zoo’s animal management staff and the architectural and engineering team. We knew that the concrete surface textures needed to have high compressive strengths to withstand the rubbing of an elephant’s leathery skin and at the same time be easy for them to walk on, and that walls had to be engineered to withstand the same impacts as a highway guardrail (a long-used standard). Our staff also brought construction options to the design process that used shotcrete’s sustainability advantages. As an example, we promoted top-down soil nail construction techniques to help save many of the trees in the areas that abutted the exhibit’s containment walls. This was an important success because modern zoo design is based on the concept of habitat immersion—creating a sense of timelessness to help zoo visitors realize the importance of preserving the world’s natural habitats. Being able to save large, mature trees in the background of these large mammals is particularly important to this illusion. It is also important to note that the substantially reduced excavation required by the shotcrete-based method provided multiple benefits, from less disruption to the animals and the public, environmental advantages (saved emissions and lowered fuel use), substantial cost savings, and schedule enhancement. Thousands of yd3 (m3) of soil remained in place due to this approach. The construction process began with carefully shaped clay models of the exhibit and three-dimensional samples of each texture we would be sculpting. This was an important means of communicating to the owner and design team how we were interpreting a very subjectively judged scope of work. We requested an interactive workshop to develop the clay forms and review the samples so that we would not have to reconfigure our shotcrete during the construction process—clay being a much easier material to re-sculpt Fig. 1: Clay models were developed to show mass and scale of the shotcrete elements of the exhibit 18 Shotcrete | Winter 2017 www.shotcrete.org


2017WinterShotcreteEMag
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