Park Place on Peachtree Plaza Redevelopment

Title: Park Place on Peachtree Plaza Redevelopment

Award Category: Waterproofing

Project Address/Location

Park Place on Peachtree Plaza Redevelopment

Atlanta, Georgia 30305
United States

Submitted By: Christopher Giffin

Company Info

Wiss, Janney, Elstner Associates, Inc.

2055 Sugarloaf Circle, Suite 250

Duluth, Georgia 30097
United States

770.923.9822

[email protected]

Project Description and Background: Park Place on Peachtree is a 40-story concrete structure condominium building constructed in 1987. Designed by architect Ted Levy, the building is located in the Buckhead area of Atlanta, GA and was the city’s first modern luxury high-rise. Well known occupants have included Coretta Scott King and Sir Elton John, who famously combined six condominium units into one 13,000 square foot residence. The brutalist-style tower is octagonal in plan and sits atop a two-story below-grade parking structure. The roof of the parking structure is a plaza deck containing residential amenity spaces, a pool, and parking around the central tower. WJE was retained to address the water leakage into the parking structure that had been occurring for an extended period of time and to address site access, parking, and to improve the amenity spaces. The building remained fully operational for the duration of the project. Access to the property was limited to a single entrance on Peachtree Road, the major thoroughfare through Buckhead. This entrance had to be maintained for residents, the construction team, and emergency vehicles.

Scope: Prior to the renovation project, WJE performed an assessment of the plaza and parking structure, which included identification of multiple leak sources through the plaza to the garage below. The Homeowner’s Association elected to address these leaks by removing the existing plaza overburden to install a new waterproofing system and re-purpose the plaza spaces. WJE was retained as the lead architect/engineer for the plaza renovation project, which included design of the new waterproofing and overburden assembly as well as design of new structural elements on the plaza. HGOR, a landscape architecture firm, was retained to design the new amenity spaces for the plaza; Smith Dalia Architects was retained to design the cladding for a new front entrance porte cochere and entryway, for which WJE served as the structural engineer. Gay Construction Company (GCC) was selected as the General Contractor for the project. The Owner retained Vandermeer Management, LLC, as the Owner's Representative for the project. The new plaza design includes an enlarged pool lounge space, residential green space, multiple garden planting areas and pedestrian walkways with custom lighting, new canopy structures, a new drive aisle at the southeast corner requiring the addition of a structural slab capable of supporting an H40 truck load, and new parking areas. The $15,000,000 renovation was sequenced in two major phases, the north and south halves of the plaza. WJE provided part-time construction observations services and participated in biweekly OAC meetings for the duration of the 10-month project. The plaza renovation involved fully removing the plaza overburden which included asphalt paving, concrete topping slabs, planter walls, soil, existing vegetation, and the original waterproofing membrane to expose the post-tensioned concrete structural slab. Demolition also included original perimeter planter walls and modification of the original drainage system. The removal of these perimeter planters increased the useable space on the plaza. The existing porte cochere at the front entrance was also removed to renovate the front entrance. A new hot rubberized asphalt waterproofing membrane system was installed over the entire deck. At large planting areas, new lightweight soil and extruded polystyrene fill was used to create landscaping berms and wells for larger tree installations. Where the original perimeter planters were removed to increase the usable area of the plaza, new drainage strategies were designed to integrate these areas with the existing stormwater management system. At pedestrian walkways and the pool deck, new concrete paver and pedestal systems were installed with multiple free standing planter boxes at strategic locations.

Solution: During the demolition process, it was discovered that the original construction details did not match the field conditions and the concrete topping slab was lightweight instead of normal weight and the topping slab thickness varied from 4 inches to 16 inches across the deck. As a result, additional structural analysis was performed to confirm the existing structure was capable of sustaining the new loading plan of landscaping, trees, parking areas, etc. As part of this analysis, the parking area assembly was redesigned to include lightweight aggregate and polystyrene fill to ensure additional dead load was not added to the structure. The modified assembly was designed to not interfere with the established finished elevations of the parking areas and also maintain the established structural sloping plan to promote positive drainage at the waterproofing membrane level. At the southeast corner, WJE designed the new H-40-rated structural drive aisle to provide access to the new valet parking area. This new structural slab required multiple revisions to ensure all finished elevations were maintained, the waterproofing system could be installed continuously, the drainage strategy slope would not be interrupted at the edge of slab, the new valet drive security gate could be installed as intended, and the selected pavement and sidewalk finishes could be installed. A combination of value engineering, select finishes, modifying the adjacent structural slab sloping plan, and designing a depressed area of the new structural slab to accommodate the new custom-blended sidewalk pavement led to the successful implementation of this component. Unique design details included new concrete planter wall design where selective demolition of previous planter walls occurred and transitions from the new waterproofing membrane to the original waterproofing at select areas where private resident-owned terraces were not included in the renovation project. Transitioning from the new waterproofing to the private terraces proved to be a particular challenge because the waterproofing membrane continuity had to be maintained at a cast-in-place concrete site wall that divided the two areas, while also maintaining the drainage strategies for both the private terrace and newly renovated amenity space. At the southwest corner of the site, the existing water supply line for the fire suppression system was leaking and required excavation to replace and waterproof. This line was directly under the drive aisle providing access to the parking garage, meaning lane closures were required. This work was completed in approximately three days thanks to the seamless coordination between all members of the project team and communication with the residents. The power bank for the building enters the structure through the east wall of the parking garage. This area was inaccessible for waterproofing from the exterior due to the existing below-grade mechanical well in this area. WJE provided a solution to this issue which involved diverting water away from this area and adding drain tile along garage exterior to promote drainage away from the penetrations. WJE also participated in electronic leak detection testing of the new membrane to confirm the integrity of the newly installed hot-rubberized asphalt assembly.

Value: As the initial water leakage investigation progressed into a full renovation of the plaza deck, WJE transitioned from the Owner's building enclosure consultant to the lead designer of record for the structural and waterproofing components of the project. Our familiarity with the building and leakage history allowed WJE's multi-disciplinary project team to provide a comprehensive plan to address the ongoing leakage and also accommodate the design features of the newly planned amenity spaces. During the design phase, we were able to lead discussions with the Owner and other design team members about the implications of overburden design choices and amenity space design as it related to the waterproofing aspects of the new system, capacity of the existing structure, and drainage capabilities of the original plaza. We performed a structural analysis of the post-tension structural slab to determine the loading limits for new landscaping fill materials and most appropriate locations for new tree placement on the deck. By reviewing the planter and overburden plan with HGOR during development of the construction documents, WJE was also able to design a waterproofing assembly that allowed for continuous drainage across the plaza utilizing as many existing plaza drains as possible, which minimized new penetrations through post-tensioned structural slab. These reviews allowed for modification of the planned overburden and amenity space design early in the project to avoid significant redesign of the plaza during construction. As construction began WJE was able to provide value in site observation services throughout the 10-month project. For example, WJE reviewed demolition strategies with GCC, including demolition methods, equipment type used, and debris storage locations, to ensure the existing structure was not overloaded or damaged. We were also able facilitate coordination between other disciplines to ensure a watertight assembly was maintained throughout the project. Our site presence also allowed us to react in real time to unforseen conditions and facilitate coordination with the other disciplines to address changes to the scope as a result of these discoveries. When the wide range of overburden thickness was discovered during the demolition phase, we needed to quickly design a new overburden assembly for the parking areas that did not exceed the dead load of the existing overburden and also did not significantly impact the planned construction schedule. WJE facilitated meetings with the Owner, HGOR, and GCC to develop a constructable design that would accommodate the planned plaza finishes. The same coordination efforts allowed us to revise the design of the new structural slab a the southeast corner to ensure the planned finishes and design intent were maintained. Throughout this process WJE was able to help ensure the design intent for the planned amenity spaces was maintained while also successfully implementing a waterproofing design to ensure the parking structure below remained watertight.

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Additional Info: Special thanks to Tim Huffman and Sharon Graham, the property management team that made the plaza renovation project possible.

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