cut had to be made within the sloping site without disturbing that cemetery, Langan had to design a s o l u t i o n t o p r e s e r v e t h e archaeologically-sensitive areas. Site History From 1799 to 1858, immigrants — many fleeing the Great Irish Famine of 1845 to 1852 — were seen by physicians aboard ships anchored in New York Harbor. If patients showed signs of infectious diseases, they were taken to the Marine Hospital and Quarantine Station on Staten Island. Patients who did not recover were buried in unmarked graves 3 to 4 ft (0.9 to 1.2 m) below grade. In November 2006, 36 skeletons — 50 percent intact — were found along with numerous other remains. Skeletal remains that were removed were reinterred in the cemetery at a ceremony held on Sunday, April 27, 2014. A “Memorial Green” park will ultimately cover the area. difference in elevation, very long and deep, costly grade beams would have been needed throughout the foundation to keep the building from sliding south. In addition to the problems View of Staten Island quarantine grounds and buildings, 1858 (courtesy of the Collection of the Staten Island Museum) but was not truly appreciated until initial environmental studies were performed in 2000 and 2001. For the next four years, numerous locations were considered and rejected for the new courthouse. Ultimately, planners decided to keep the courthouse at its present location but decrease the development size to avoid any effect on possible cemetery remains. A supplemental archaeological study was performed in 2006 to identify the boundary of the cemetery, and after that study, a 20 ft (6.1 m) wide buffer was established around the cemetery to prevent disturbance. Engineering Problems Attack on the quarantine establishment, September 1, 1858 (courtesy of the New York Public Library Picture Collection) The presence of the hospital was not without controversy. Because of suspicions about the potential for diseases to spread, neighbors often appealed to authorities to close the hospital, complaining of terrible odors and of people in the community getting sick. Community anger grew until one day in 1858 when a crowd broke through the hospital gates and set the buildings on fire. According to historical accounts, “the Quarantine staff gave way before the attackers and set about helping them remove patients, people, cats and canaries from the buildings.” This site history had been well- documented in the annals of Staten Island 68 • DEEP FOUNDATIONS • MAR/APR 2015 The site chosen for the new courthouse presented several engineering challenges. First, the natural topography involved a large change in elevation across the site, creating an unbalanced earth pressure acting on the foundation of the new courthouse. The unbalanced earth pressure of nearly 20 ft (6.1 m) of soil resting on the new northern foundation walls would have been substantial enough to slowly push the building south. Additionally, this would have created structural issues with the building superstructure that would have required costly braced frames or moment frames. To hold back the slope, the temporary condition for excavation would have required vertical members for a support system in tandem with drilled tiebacks. The foundation at the north of the site required an excavation of about 27 ft (8.2 m) at the deepest location. The foundation at the south of the site required an excavation of about 4 ft (1.2 m) at the shallowest location. Because of the caused by the difference in eleva- tion, the presence of archaeolog- ically-sensitive areas in the northern part of the site would have interfered with the massive vertical cut that was required. Furthermore, the excava- tion would have to be performed in a manner that would protect the archaeologically sensitive areas of the site. A typical support of excavation system would not have been cost effective because of the aforementioned atypical site conditions. Also, a traditional earth retaining wall typically used in New York City did not seem feasible because it would have required excavation encroaching on the cemetery. Engineering Solutions To solve these elevation and preservation issues, Langan had to find a way to permanently support the excavation and make a nearly vertical cut from the slope without disturbing the cemetery. Excavation within a slope typically requires inserting vertical members (such as driven soldier piles) and supporting them by installing lateral restraints (such as long drilled tiebacks). Numerous types of excavation systems were suggested and considered, including internal bracing, which would have made it extremely difficult to work within the site. Another system, soil nails along the sensitive part of the site and soldier pile and wood lagging or open-cut excavations for the balance of the site, was also considered. As with all projects, the cost for instal- lation and materials, along with the time to construct, were weighed in the selection of the earth retention system. A permanent soil nail wall with shotcrete facing was selected to: retain the cemetery, stay within the buf- fer zone and decrease the lateral demands required for the building foundation. For the permanent wall, the nail spacing and forces were based on modeling the wall geometry using SNAILZ, a program used for analyzing soil nail
