Natural Resource Damage Assessment: Methods and Cases

and translate that into marsh acre-years. They then calculated how long it will probably take the
damaged resources to recover. Texaco then offered to create new marshland so that the present
value of the acre-years of new marsh would compensate for the present value of the acre-years
lost.
To calculate the number of aquatic animals and birds killed by the spill, the trustees and
Texaco agreed to use models to estimate the figure based on the amount of oil spilled, rather than
attempt to count carcasses. They decided not to try to count because it would be expensive.
Moreover, a count would likely be inaccurate because of the difficulty of finding dead animals in
the lake and marsh and because of the difficulty of knowing whether variations in plankton
counts were caused by the spill or by other factors. In addition, the small number of dead birds
and marine animals found during the containment and cleanup indicated that the loss of life was
relatively small. The trustees estimated that the spill killed 7,650 kg of marine biomass and 333
birds. Texaco estimated that the numbers were significantly smaller. However, because the
trustees found that Texaco’s restoration offer was more than sufficient to compensate for the
high estimate, there was no need to resolve that disagreement.
To calculate the amount of marshland services lost, the trustees and Texaco conducted a
joint field study in July and October of 1997 and in June of 1998. Based on these studies and on
observations of the size and shape of the oil slick during the containment and cleanup, they
divided the damage to marshland into four categories of severity and estimated the amount of
marsh in each category. Based on that, they then estimated the amount of acre-years of marsh
services lost to the spill. The total damage to marshland in acre-years was estimated at 75.6.
The trustees determined that human use of the area was not significantly affected, since
alternative resources were easily available during the time the affected area was unavailable, and
the cost of estimating any loss would probably outweigh the loss itself. The trustees did consider
that there was some loss of human use in deciding on the appropriate compensation.
To calculate how many acres of salt marsh grass Texaco should plant, the trustees
considered several factors, including: the amount of time it would take the planted marsh to
reach maturity, the amount of time it would take marsh grass to grow on the site through natural
colonization, the fact that the grass will be planted in strips so that unplanted areas will be
colonized by the planted grass, and the fact that the planted grass will prevent erosion and thus
preserve the site. Texaco was required to plant enough grass so that the number of acre-years,
discounted to present value, created on the site through Texaco’s efforts, minus the number of
discounted acre-years that would arise naturally, equals the amount of acre-years of damage.
The trustees calculated that Texaco must plant 18.6 acres.
Settlement: Texaco agreed to implement a restoration project that consists of planting
marsh grasses on 18.6 acres of East Timbalier Island and to pay approximately $480,000 to
cover response and assessment costs.
The trustees held public meetings and other consultations to consider what restoration
projects would most effectively compensate for the damage. The trustees found that, because all
of the directly affected area, except for 0.28 acres, was recovering rapidly, primary restoration
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