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portion of the tundra with gravel dikes or berms. They
constructed other pits, called “containment” and “flare” pits, to
collect escaped hydrocarbons during oil production.
The AOGCC regulations from the period at issue provided
that, upon abandonment of wells, the pits at well sites must be
filled and the well sites left in a clean and generally level
condition. Exxon’s plan for closing the pits upon abandoning and
plugging the wells uses the so-called freeze-back-in-place
method, which involves placing on each pit a 6-foot layer of
gravel fill with a domed cap. The insulating effect of the
gravel cover keeps the waste located in the pits permanently
frozen, thereby containing the waste in place. During the years
in issue, freeze-back in place represented an acceptable method
of pit closure.
Exxon’s estimated DRR costs associated with pit closures
include wages, fuel, rental of equipment, supplies, and hauling
of gravel and equipment.
Charles E. Wilson, a civil engineer and employee of Harding
Lawson Associates, a large environmental remediation and civil
engineering firm with an Anchorage office, developed Exxon’s pit
closure plan and estimated the related DRR costs. Mr. Wilson is
experienced in closing pits and moving gravel on the North Slope.
Mr. Wilson estimated total PBU pit closing costs in the
Prudhoe Bay field in 1970 and 1980 dollars to be $152,720 for
each of the 174 pits for which an estimate was done (for a total
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