Executive Summary: Numerical analysis was used to simulate a catastrophic failure of the largest crude oil tank, Tank 11, in the Valdez Marine Terminal's (VMT) East Tank Farm (ETF). The goal of this analysis was to quantify the volume of oil that would escape Tank 11's secondary containment system in such a worst-case scenario.
Field testing has revealed that a component of the ETF’s secondary containment systems, known as the catalytically blown asphalt (CBA) liner, likely has unrepaired holes in it that could allow oil to reach groundwater in the event of a spill, but the secondary containment systems are required to protect groundwater from oil spill contamination.
Alyeska’s spill response activities (e.g. times and recovery/processing rates) were modelled based on their stated capacities. To simulate how much oil could leak through a damaged CBA liner, this analysis considered the following key factors, among others: full storage volume of Tank 11, area of Tank 11’s secondary containment system, hydraulic conductivity or permeability of the earthen fill above the buried CBA liner, depth of that earthen fill, rate which spilled oil could be drained from the secondary containment area, time estimate for spill cleanup, and an estimate of the percentage of CBA liner damage (i.e., holes).
The results of the simulation indicate that the earthen fill above the CBA liner will be fully saturated with oil in under 8 minutes. Assuming a value of 0.1% liner damage, the standing oil will be drained in approximately 2.8 days; however, 38,000 barrels of oil will have leaked from secondary containment during this time period. Over the entire 30-day clean-up window, the simulation estimates that approximately 125,000 barrels of oil will be discharged through damage in the CBA liner.