assessing and communicating risk:
a partnership to evaluate a superfund site on leech lake tribal
the Cass Lake, MN Superfund Site Report
Why was this project needed?
The Leech Lake Tribal Council was concerned that the former wood
preserving facility located along Pike Bay in Cass Lake, MN, had
not been studied well enough to know whether or not the clean up
actions taken by the company that owned the site were successful.
They were concerned about whether there were still chemical contaminants
on and near the site that might harm the health of local people
and the environment.
What is the partnership?
In 1997, the University of Minnesota’s Natural Resources Research
Institute and Sea Grant Program teamed up with the Leech Lake Tribal
Council to submit a grant proposal to the U.S. Environmental Protection
Agency Environmental Justice Program. The proposal was funded and
began in 1998.
What was proposed in the grant?
To address the tribal council’s concerns, the University agreed
to bring together experts to review the available scientific data
from the site and try to determine whether the site was being cleaned
up effectively. The experts were also asked to make recommendations
for future work on the site, including additional data that should
be collected. The University also agreed to share the conclusions
of the experts with the Leech Lake Tribal Council and local community.
Three groups of experts were brought together. The first group reviewed
groundwater data (Groundwater Panel), the second reviewed human
health data (Human Health Panel), and the third group reviewed ecological
data (Ecological Panel). As part of the project, scientists from
the University collected additional biological and geological data.
What were the general conclusions of the three expert panels?
The site at Cass Lake continues to be contaminated with chemicals
at levels considered harmful to humans and wildlife. The chemicals
are commonly found at wood preserving industries and are related
either to actual preserving activities or to general facility maintenance.
Some of the chemicals can cause cancer. Known contaminants of concern
•Semi-volatile organic compounds (SVOCs), including Polycyclic
aromatic hydrocarbons (PAHs)
•Dioxins and polychlorinated biphenyls (PCBs)
•Certain heavy metals
The site and surrounding area have not been sampled well enough
to know how far the contamination has spread. There is not enough
information to know how likely it is that additional contaminants
will move off of the site into the surrounding area in the future.
It is not clear how great the risk is now or will be in the future
to environmental and human health. More groundwater, ecological,
and human health data are needed.
Although a number of steps have been taken to clean up the contamination,
those efforts have not been fully successful. The panels of experts
found evidence to suggest that some contaminants are moving off
of the site to areas that could cause human and ecological health
The panels of experts also found evidence that people living or
working near the site are probably being exposed to toxic chemicals
at levels higher than what is considered protective of human health.
This is especially important for children who live and play near
What were the general recommendations of the three panels?
Steps should be taken as soon as possible to reduce health risks
to children and other people exposed to the site. For example, there
are high levels of dioxins and furans in the soils on the site.
Until these contaminants are cleaned up, the site should be fenced
off to keep people away.
It is important for scientists to learn more about the amount and
location of the contaminants that were released when the plant was
in operation, where the contaminants are currently distributed,
as well as how much and where the contaminants are moving.
Work needs to be done to have a better understanding of all the
different ways that humans, plants, and wildlife are currently being
exposed to the contaminants. These efforts need to consider how
local people use natural resources in their day-to-day lives.
The health of local people who have been exposed to the site and
the health of the local environment, including plants and wildlife,
should be evaluated carefully. This will help scientists do a better
job of estimating how much of a risk the site is to human and ecological
Standard methods of determining the health risks of a contaminated
site do not always look at special circumstances, such as traditional
tribal uses of natural resources. The methods used to determine
risks should be designed to include traditional tribal practices
and should consider the possibility that people might be exposed
to contaminants in a number of ways as they live, work, and play
near the site.
The Groundwater, Human Health and Ecological Panel Reports, and
other Superfund Site related information can be found at the Web