Subgrade preparation Each of the three tanks are 150 feet (45.7 m) in diameter and 60 feet (18.3 m) tall and constructed of welded steel. The entire area is enclosed inside a 6 foot (1.8 m) high berm constructed of local gravel that is also used under the tanks. In those areas comprising the base of the tanks, compaction was achieved by dynamic compaction, repeatedly dropping 15 ton (13.6 mt) weights to improve bearing capacity, reduce settlement and diminish liquefaction potential. 4 Ring wall construction The first portion of the liner deployment was for secondary containment/ leak detection under the floors of the storage tanks contained within the concrete ringwalls, supporting the tank walls. Historically, tank ring walls are cast in place in a tank construction of this type. However, a precast system developed by the project construction manager, Latitude 63 of Anchorage, was used to save time and expense. Precast sections are joined to form a continuous circle with interlocking connections that are not subject to leakage and provide the strength necessary to support the tank walls. This allowed construction to proceed more rapidly during the short Alaskan construction season. Tank construction Upon completion of the ring wall and tank base secondary containment, the bulk storage tank construction began. Single steel rings were constructed from plates; then construction proceeded vertically with the next ring until the design height of the tank was reached and completed. Each tank was completed before proceeding to the next to maintain quality control and safe working conditions. 5 6 7 FIGURES 4-7 Stages of ringwall installation. Photos courtesy of Latitude 63 GeosyntheticsMagazine.com 15http://www.GeosyntheticsMagazine.com