Project Description
Whitestone was originally retained by Post Management, LLC to perform a limited geotechnical investigation of a proposed self-storage facility site located at 3325 Atlantic Avenue in Brooklyn, Kings County, New York. Acadia Realty Trust took control of the project in June 2006 and ordered Whitestone to conduct a follow-up investigation prior to site re-development. The site development plan included partial demolition and modification of an existing site building and construction of an approximately 20,491 square feet, four-story facility with a two-level cellar, associated pavement, and utilities.
Whitestone’s 2006 subsurface exploration included a site reconnaissance, installation of 12 soil test borings, groundwater level observations, and soil sample collection for in-house laboratory analyses. The borings were drilled to depths ranging between 50 and 102 feet below ground surface with various equipment including an all terrain vehicle-mounted drill rig using hollow stem augers; a low-clearance, skid-mounted drilling rig using hollow stem augers; and driven casing with mud rotary techniques. Data from the exploration were analyzed by Whitestone’s geotechnical engineers in light of the proposed development and recommendations were presented for:
- foundation design (structural foundation mat bearing on approved glacial deposits and/or structural fill materials);
- pavement support (including potential subgrade stabilization); and
- groundwater control (dewatering during construction).
Whitestone performed pre-construction surveys in 2007 and 2008 to document the physical condition of accessible portions of residences located within 100 feet of the cellar portion of the proposed self-storage building. Residential exteriors, garages, and basements were inspected and crack monitors installed as permitted by the property owners. A comprehensive written and photographic record of the survey efforts was prepared to fully document the existing condition of surrounding structures prior to construction.
Vibrations generated by demolition and pile driving operations were monitored by Whitestone personnel during December 2007 and November 2008 to January 2009. Data from the 2007 event were used to develop baseline vibration levels that were subsequently used to monitor vibration measurements on a near continuous basis during installation of basement excavation shoring within the proposed cellar excavation limits. Whitestone field personnel monitored ground vibrations with two seismographs. One monitor was placed at various locations along the eastern, southern, and western property line between the site and nearby residential structures. The second monitor was placed in a fixed location nearest to an active underground subway tack associated with the Long Island Railroad (LIRR). Results were recorded in histograph format and evaluated using action limits established by the U.S. Bureau of Mines. Post-construction surveys were performed and documented following construction.