Station 650 (Landbay J)
The project includes development of 183 luxury residential units in a single four and five-story wood frame building. Landbay J will also features 2,900 sf of retail space and include one level of above-grade parking and one level of below-grade parking.
Potomac Yard, a former rail yard dating back to the early 1900s, is today the site of the 167-acre master planned, mixed-use redevelopment. Following decommissioning as a rail yard in the late 1980s, Potomac Yard was officially declared a Superfund site and in 1995, an intense hazardous soil remediation program was undertaken to deal with contaminated soil containing heavy metals and hydrocarbons, including diesel. The environmental cleanup was completed in 1989; however, the overall site continues to be challenging from a road and building support standpoint. With a roughly 50 ft deep soft soil profile, Landbay J was no exception and early project planning suggested using driven pile support but the estimated cost was approaching $2 million.
The soil conditions consisted of approximate 10 feet of contaminated urban debris fill overlying 8 feet of soft clay, 35 feet of loose to dense sands, underlain by very stiff Potomac Group clays. The original geotechnical report recommended 80-ton 14×73 steel H-Piles or 80-ton, 14-inch square-precast concrete piles driven 65 feet into very stiff Potomac Group clay.
GeoStructures worked with the project team during a value engineering exercise and identified the Geopier grouted Impact® Pier (GIP) system as a ground improvement solution that would allow the building to be supported on a conventional spread footing foundation. The 50-foot deep grouted Impact Pier elements (Geopier rigid inclusions) tested for the project deflected 0.04 inches at a load of 50 tons. The GIP system design was able to meet the performance criteria with a considerably lower cost than the deep foundation systems (driven piles) that were considered for the project.
A Load Transfer Platform (LTP) consisting of a 2-foot thick ungrouted Impact Pier elements was installed between the Grouted Impact Pier element and the footing bottom to create a shear break between the Geopier rigid inclusion element and the footing.
By using Geopier ground improvement in lieu of piles the owner was able to:
- Take advantage of a faster installation schedule, which meant they could move in their first tenant earlier, and
- Use Geopier rigid inclusions instead of piles saving over $750,000 as well as other cost savings which included:
- Using spread footings vs. pile caps which meant less concrete
- Eliminating pile cutoffs which resulted in a quicker installation
- Savings on construction schedule by using Geopier versus piles