Poor Soil Conditions at Helipad Improved within Lightweight Aggregate Fill

By Ed Whalen, Norlite Corporation

The Northeast corridor, and especially Manhattan, is the busiest helicopter environment in the world. In December 2010, Helo Holdings Inc. opened the first new commercial heliport in more than 30 years – aimed squarely at the turbine helicopter community. The 7.26 acre “Helicopter-Only” facility is located in Kearny, New Jersey at 165 Western Avenue and is just 2 minutes flying time from Manhattan. It offers 28,000 sq. ft. of hangar space, 10,000 sq. ft. of lease-able hangar and administrative offices, ample landing and parking (up to 12 outdoor helicopter parking spaces).

The project was situated along the Passaic River and had a gas main that ran the length of the property. The elevation of the landing pad had to be raised approximately 3 feet due to the project being located in a flood plain. The geotechnical engineers had concerns with the loads that would be placed on the gas main due to the construction and additional fill needed to raise the elevation. A ten foot wide by three foot deep trench over the gas main was excavated and the existing soils were removed. The removed material had a density of 135 pounds per cubic foot and it was replaced with fine lightweight aggregate with an in-place compacted density of 75 pounds per cubic foot. An additional 8,000 cubic yards of lightweight fill was used to build up other areas around the site. This fill had the same requirements as the fill used over the gas main.

The geotechnical engineers evaluated both a ¾” x No. 4 and 3/8” x 0 lightweight fills that were supplied by Norlite LLC. Although the angle of Poor Soil Conditionsinternal friction and permeabilitites were slightly less for the finer material, the design of the project allowed the finer material to be used saving the owner a considerable amount of money. The density difference between the coarse and fine lightweight fills was approximately 15 pounds per cubic foot.

The contractor was able to complete the project that turned a brownfield site along the Passaic River into a transportation center to serve the metropolitan New York area. He was able to save the owner money by being innovative and utilizing a finer gradation of lightweight fill material while still meeting the requirements of the job.