Deep Foundation Load Testing

Flag City Natural Gas Processing Plant
Jackson County, Texas
Client: Alpine Site Services
Owner: Confidential

This plant has the capacity to process a product stream of 800 Million cubic feet per day. The plant, completed in 2013 included 4 “trains” that each include cryogenic units, amine units, refrigeration units, regeneration gas heaters, pipe racks, various compressor units, flares, and other processing equipment. Maximum pile service loads associated with mechanical systems and pipe racks were on the order of 90 to 100 kips compression and about 60 kips in tension. Pipe rack foundations were also required to withstand about 115 kip-ft of overturning due to wind loading. The large site was underlain by two primary soil conditions: dense sand was present on the western site extents, while soft clays were the dominant soil condition in the central and eastern portions of the site.

The CG team performed load testing on several steel pipe screwpile configurations as part of project planning. The piles used on the site ranged from 4-1/2 to 9-5/8 inches in diameter with up to 3 helices. We documented ultimate capacities ranging from 95 kips for the 4-1/2” diameter piles up to 280 kips for the 9-5/8” piles. Lateral load testing indicated that the larger piles could be used to support lateral loads of up to 15.5 kips with deflections of one inch or less. We also completed moment testing of the larger piles and determined an ultimate moment capacity of 114 kip-feet.

In all, Alpine installed approximately 4,200 piles for this project.

Utica East Ohio Gathering - Harrison Hub
Scio, Ohio
Client: Alpine Site Services
Owner: Utica East Ohio

The Harrison Hub is a fractionation, storage and shipping facility. The facility includes three processing equipment “trains”, at-grade and elevated bullet tanks for various products, a train car loading facility, and an electrical substation. The site posed significant geotechnical challenges in that the total length of improvements was on the order of two miles and earthen cut and fill depths up to 65 feet were required to bring the site to final grade.

The CG team completed load testing of a single-helix 5-1/2” pile in both the cut and deep fill portions of the site. In the cut areas, pile lengths were limited due to shallow siltstone and sandstone bedrock. In the deep fill areas, pile length extended to approximately 75 feet or more. Testing indicated that Alpine’s piles were capable of supporting an ultimate compressive capacity of 280 kips when bearing on the bedrock materials. The ultimate tension capacity of the pile design was found to be 130 kips. The pile was also subjected to lateral load testing and deflected approximately 1 inch under 8 kips. Using Alpine’s pile reinforcement system, the pile was able to sustain a lateral load of 22 kips with only about 0.8” of deflection.

Alpine has installed approximately 5,500 screwpiles to date and is often contacted by the owner to complete plant upgrades and additions.