24 Leonard Street Case Study

PROJECT CASE STUDY IV 24 LEONARD STREET

THE FOCUS OF THIS CASE STUDY WILL BE ON A REAL JOB SITE WHERE CERTAIN FLOORS OF AN EXISTING BUILDING WERE KEPT IN ORDER TO KEEP THE EXISTING PARKING LICENSE VALID, AND TO BUILD ADDITIONAL SQUARE FOOTAGE TO THE BUILDING. THIS WAS DONE TO ENSURE THE CONSTRUCTION OF A NEW MULTI-LEVEL AUTOMATED PARKING SYSTEM. A 30FT. DEEP EXCAVATION UNDERNEATH THE EXISTING STRUCTURE WAS UNDERTAKEN FOR NEW BUILDING SUPPORT, AND FOR THE INSTALLATION OF THE NEW UNDERGROUND PARKING. ABOVE GROUND, THE NEW COMPLETED RESIDENTIAL STRUCTURE REACHED 9 STORIES. THE STUDY WILL EXAMINE THE SPECIFICS OF 24 LEONARD STREET - A GROUND-UP CONDOMINIUM PROJECT DESIGNED BY BKSK ARCHITECTS - TO CONVEY FOUNDATIONS GROUP’S CONSTRUCTION METHODS FOR SUCH EXTENSIVE BUILDING SITES.

COMPANY Foundations Group is an established Building + Construction Management firm formed in 1993 by Cooper Union School of Architecture trained architects. Comprised primarily of architects and engineers, our team is keenly aware of the design needs of each project, and we run all projects in a very collaborative effort with developers, clients, and architects.

Over the last two decades, Foundations Group has built over 1.5 million sqft of construction in New York City ranging from ground-up buildings to building additions, conversions, gut rehabilitations, high-end residential, commercial fit outs, and museum exhibits.

As one of the premier non-union Construction Management firms in New York City dedicated to building very high-end projects, we pride ourselves on our track record. We work with world renowned architects and designers such as Enrique Norten, Tadao Ando, Morris Adjmi, Soo Chan Khian/SCDA, Michael Gabellini, Shigeru Ban, and BKSK among others.

We were selected by Tim Lynch and the NYC Department of Buildings as one of the select construction managers to help the DOB with their study on how to keep buildings and sites safe - High Risk Construction Oversight (HRCO). Our work has been published in numerous publications including The New York Times, Interior Design, and Architectural Record.

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MAIN CHARACTERISTICS OF THE EXISTING BUILDING 100ft. x 100ft. brick parking garage.

Load bearing walls built on rock + rubble foundation over timber piles.

Piles connected to structural steel center columns w/ 50ft. 48in. deep I-beams.

Floor slabs constructed as cast in place concrete.

PRE CONSTRUCTION

CHALLENGES FACED THE BUILDING PLAN To comply with code, we were to keep the existing parking license from the existing building, which would make this an alteration rather than a full new building project. As a result, the 3rd and 4th floors of the existing building were kept and we excavated 30ft. underneath for the new support structure and parking system.

DEMOLITION / EXCAVATION MONITORING PLAN: As the building on the west side of this site was a landmark, we were under the technical procedures section 10/88, known as TPPN 10/88. This plan includes vibration and optical monitoring of all buildings within 90ft. of the construction site, and allowances for movement are much less than regular buildings. TPPN was altered by the SOE engineer and approved by the head of excavation unit of the DOB. DEWATERING: Per geotechnical report, we had a 12ft. silt layer from the bottom of the excavation, left over to ballast the water pressure under this layer. There was a chance of a blowout, so we had to make sure a dewatering plan consisting of deep wells was ready for any additional dewatering. Once we reached the bottom of excavation we experienced this blowout and installed the deep wells to continue dewatering during our foundation work.

CONSTRUCTION METHODS

DEEP EXCAVATION

[ CERTAIN FLOORS FROM EXISTING BUILDING KEPT ]

[ GROUND LEVEL ]

[ 30FT. DEEP EXCAVATION FOR UNDERGROUND SUPPORT STRUCTURE AND PARKING ]

*GRAPHIC NOT TO SCALE

START OF DEMOLITION

START OF EXCAVATION

FULL EXCAVATION FACING LEONARD STREET

FULL EXCAVATION FACING BACK WALL

NEW AUTOMATED PARKING STRUCTURE

NEW FOUNDATION + WALL WORK

PARKING SYSTEM INSTALLATION

FOUNDATIONS GROUP / WWW.FOUNDATIONSGROUP.COM 520 W27TH ST., SUITE 302, NEW YORK, NY 10001 / TEL. 212 924 1724