Located along the western banks of the Hudson River in Cliffside Park, N.J., (approximately two miles south of the George Washington Bridge and seven miles north of the Lincoln Tunnel), 300 Winston Towers is a popular residential building with approximately 600 units. The main entrance to the building is accessed via a 28,000-square-foot entrance plaza, which consists of driveways, walkways, and a visitors' parking lot, and sits directly above the 500-space residents' parking garage. Over the years, pooling water on the entrance plaza had leaked into the parking garage below, leading not only to the deterioration of the entrance plaza structural slab, but also to spalling of some of the concrete beams and columns in the garage. The solution came in the form of a waterproofing membrane.
The original plaza was composed of various toppings over a precast concrete double-tee structural slab. The driveway and visitors' parking area were paved with asphalt, and the walkways were topped with pavers. The north perimeter of the entrance plaza was landscaped, containing various soil depths. When the owner identified the deterioration, an initial condition survey performed by the engineering firm The Falcon Group was used to develop project specifications and drawings. Structural Preservation Systems, hired to demolish and reconstruct the entrance plaza, corrected these problems. After the existing toppings were removed, the contractor and engineer performed another condition survey to determine the extent of deterioration.
Considerable effort was devoted to preconstruction planning and site phasing to ensure the demolition and reconstruction process went smoothly and safely for both the onsite crews and the building's residents. The project team -- consisting of a project manager, superintendent, and foreman -- collaborated closely on all aspects of the project, including budget, working restrictions, phasing/site logistics, and, most importantly, expectations and procedures. Communication of the contractor's safety culture was also an important focus of planning meetings, in order to keep all parties safe.
The importance of safety also extended to the residents of the building, who needed to be able to use the entrance plaza during the project. Working closely with the owner and engineer, Structural Preservation Systems developed a phasing plan that identified which parking spots would be closed and where the barricades (in this case, post shores and polyethelene plastic) would be placed. To protect vehicles that would remain in the garage below, ethylene propylene diene monomer (EPDM) was installed over some of the repaired tee-to-tee joints as temporary waterproofing. Further, to maintain free and clear access to the front door, a site logistics plan was created to show how tenants could safely navigate the work area. Jersey barriers, orange snow fencing and post fencing were clearly color-coded so everyone would be aware of the site restrictions. The plan also highlighted the egress path for the tenants from the front main entrance. The owner informed the tenants about these phasing and logistics plans by distributing them and posting signs throughout the building.
The first phase of construction involved demolishing the various plaza toppings to make way for the new toppings and a waterproofing membrane. With the large volume of debris generated, it was critical to avoid point loading of the structural deck. The deck could support lighter machinery such as skidsteers, but heavier trucks and containers were set on grade to avoid any structural problems. The existing soil was not piled too high to avoid structural damage to the deck. Once the toppings were disposed of completely, the existing waterproofing membrane was removed with the aid of ride-on scrapers, as well as handheld grinders for hard-to-reach areas. Any membrane still bonded to the deck after this process was removed by hydrodemolition. It also was determined that it was necessary to install additional drains to help prevent the water from ponding on the plaza.
With a clean structural deck, the engineer and contractor performed a condition survey to determine the extent of the concrete restoration. A few spall repairs were required, and most of the grout in the tee-to-tee joints had to be replaced. New drains were installed in the structural deck to allow for better drainage and prevent the pooling that had led to the failure of the waterproofing membrane.