SABINE PASS LNG PROJECT
Cameron Parish, Louisiana

To expedite permit processing of a new tank farm, the owner selected a site with little public opposition however, a site poorly suited for construction. In general terms, the site was a dredge spoil pile. These soils have little bearing capacity and consolidate extensively when subjected to loads. Remedial Construction Services, L.P. (RECON’s) challenge was to develop an approach that:

• Stabilized over a million cubic yards of zero strength soils;
• Constructed 300,000 cubic yards of dikes with an above grade height of 30 feet;
• Accelerated 7 feet of consolidation from 7 years to 12 months; and
• Constructed a temporary dock.

Stabilization
The largest hurdle consisted of stabilizing 500,000 cubic yards during the first 6 months of the project to allow the tank contractor access to the site. The remaining materials could be stabilized within 12 months. To meet this schedule, RECON needed an innovative technique; otherwise 20 soil mixing rigs and over 192,000 tons of concrete would be required.

RECON’s approach was to use a technique developed for the stabilization of massive impoundments in the environmental industry – use a high calcium oxide ash to consume the soil moisture and allow the soils to be placed and compacted to the required 25 psi unconfined compressive strength. RECON processed 3,500 cubic yards per day during the first six months of the project, meeting the project schedule.

The top 8 feet of stabilized soils were used for construction of the secondary containment dikes. These dikes averaged 15 feet above existing grade. Preliminary calculations indicated that these dikes, once built, could subside as much as 7 feet. To accelerate subsidence, over six million linear feet of wick drains were installed on 4 foot spacing to a depth of 90 feet. The water flowed into a French drain system at the toe of the dike. To continuously monitor the dikes, over 50 nests of vibrating wire piezometers, settlement platforms, and inclinometers were installed.

Dock Construction
The area selected for the construction of the dock had low to zero- strength soils to depths of 70 feet. The dock design required:

• A bulkhead with 16 feet of draft,
• A platform for a 200-ton crane, and
• A truck turn-around and materials staging area.

The bulkhead was constructed using 65 foot sheet piles. These piles were tied back with 50 foot long Dywidag Threadbar® rods to a series of A-frame battered pipe piles, each 85 feet long. The battered piles had a concrete pile cap cast-in-place which anchored the rods.