Built in 1812, City Hall has hosted presidents and kings throughout its 200-year history. It contains many significant paintings and priceless artifacts. The five-story, 70,000-square-foot building remains busy today as the hub of city government. It is the oldest city hall in continuous operation in the United States, and had not undergone any major renovation in more than a century. Work began on the complex and comprehensive four-year restoration in 2008, and involved structural improvements and upgrades to building services, as well as meticulous restoration of much of the interior and exterior. Major project challenges included:
Field conditions: Pottery, debris, graves and other artifacts found beneath the site demanded that a team of preservationists monitor construction. When artifacts were found, work stopped while each was documented, analyzed and preserved.
Building Occupation: Much of City Hall had to remain in operation during construction, with work proceeding safely and unobtrusively around the needs of the city government.
Logistics and Access: Surrounded in a dense urban setting by the Brooklyn Bridge, Wall Street, nine separate subway lines, and an equally historic public park, the City Hall project faced several serious access and site restrictions.
Historic Restoration: The project required meticulous restoration of decorative plaster ceilings and canvas murals that run thematically throughout it. Also, priceless furniture, fixtures, and valuable artwork needed to be removed and stored off-site.
Safety: Because of the nature and location of the work, safety concerns were prevalent. Safety risks were mitigated through proactive, precautionary tools and protocols.
Micro-tunneling: For years, City Hall’s electrical service was provided by off-site feeds that ran through an underground tunnel from the adjacent Tweed Building. To provide City Hall with its own electrical source, the A/E proposed running the electrical feed from a vault across the street to a new electrical sub-basement. The plan required digging a 2,000-foot-long trench though City Hall Park, which posed several challenges, including the daily discovery of archeological finds, and conflict with the health of 300-year old trees. As a result, tunneling was reduced to only two feet per day, nearly immobilizing the schedule. Hill’s CM recommended micro-tunneling. A micro-tunnel boring machine, set 15 to 20 feet underground, generated a 32-inch-diameter tunnel for new feeds. The solution reduced an eight-month timeline to three and a half weeks, and saved more than $2 million in associated costs.
Fuel Cell Technology: Hill recommended and managed the installation of innovative fuel technology to reduce City Hall’s energy consumption. As a result, the building was able to reduce its energy draw and carbon footprint while gaining valuable LEED points for environmental sustainability.
With occupants including the Mayor and City Council, we needed an experienced and sophisticated management team to complete the project successfully. Hill has managed a number of complex renovation projects at cultural institutions for DDC, and we had confidence in their expertise in government projects and their proven ability to deliver high-profile projects.
As CM, Hill’s approach to controlling the project and delivering innovative and feasible solutions to challenges has been integral to guiding the project to a successful completion. Highlights of Hill’s performance included managing the staging and logistics requirements of the site, which is in a public park and rests above four subway lines, and performing the work while City Hall remained occupied and open for business. In addition, Hill was particularly adept in dealing with the unforeseen conditions on the project; whenever the work revealed an unexpected deficiency in the building, Hill worked with the team to solve the problem quickly and effectively.
David Burney, FAIA
New York City Department of Design and Construction