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by Paul Kashmann
These are very difficult scales to balance. Exactly how many pollutants are acceptable in a park lake and how many does it take to foul the water? How many dead birds are acceptable, and how many constitute a needless tragedy?
These questions seem to
be at the heart of an ongoing debate over why waterfowl continue to die
off in disturbing numbers in City Park’s Duck Lake, what is the root
cause of that die-off and what can be done to alleviate the situation.
In 2007, and again this year, what appear to be inordinate amounts of
dead birds have been found in Duck Lake, and residents,
environmentalists and animal activists want to know why. Many of the
bird deaths have been attributed to avian botulism by Denver Parks &
Recreation.
Adrienne Anderson is a former board member of Metro
Wastewater and former professor of Environmental Studies at the
University of Colorado-Boulder. She attributes the problems in City Park
Lake to the “recycled water” that has been funneled to City Park,
Washington Park and other area green spaces since 2004, when the flow of
the City Ditch was reversed in conjunction with the I-25 T-REX light
rail/highway expansion project.
For decades these areas received
water from the South Platte River through the historic City Ditch that
ran south to north through Denver. Now, a plant located in Commerce
City, near the Metro Wastewater treatment facility, receives water
treated initially by Metro, and then processes it further to meet
standards deeming it satisfactory for non-potable uses.
The wastewater facility treats water from a number of sources
including contaminated water from the old Lowry landfill. For decades
the landfill was the dumping ground for all manner of radioactive waste,
cleaning solvents, pesticides and other objectionable substances. It is
the Lowry influent that Anderson sees as the culprit.
“This has
never been done anywhere – flushing plutonium-contaminated wastewater
through a public sewer infrastructure,” said Anderson in an August 2009
Profile article on the Lowry water picture. “They don’t have treatment
systems to handle hazardous or nuclear waste and the (Metro) plant is
not certified to handle this waste.”
Denver Water has a website
page devoted to presenting its version of the Lowry story. It states,
“The discharge (from Lowry) represents 0.026 percent of the 140 million
gallons per day treated by Metro Wastewater. Extensive scientific
testing by the EPA over more than a decade has not identified any
elevated risk from the Lowry discharge.”
Linda Neeley is a
private investigator by profession, and a volunteer with Wild Bird
Information & Rehabilitation of Denver. Neeley has concern about the
recycled water that extends past the Lowry element. “It’s very high in
sodium, which can affect vegetation that filters bacteria from the
water.” Neeley explains that the deaths are most certainly related to
conditions in the water, because ducks and cormorants are the ones
dying, and they get their food from the water. “Geese eat grass,” she
explains, “and they’re not dying.”
“Botulism and numerous other
life-threatening organisms thrive in sewage effluent water, with its
high nitrate levels and such,” said Anderson in a recent e-mail. “This
is what is being pumped to fill the City Park lakes. Among the stew,
semi-volatile organic compounds such as those present at huge
volumes in Lowry Landfill that are potent grease cutters, and which
predictably de-strip avian species’ feathers of their protective oils.
Never mind these chemicals’ ability to weaken immune systems, making
wildlife even more vulnerable to succumbing under these conditions.”
A study completed by the U.S. Fish & Wildlife Service (USFWS) in
2007 addressed the issue of duck deaths at water treatment facilities
along the Front Range, but has not yet been released to the public.
“That die-off was not at City Park and was not due to botulism,” said
James Dubovsky, Chief, Division of Migratory Bird Management,
Mountain-Prairie Region, USFWS. Asked about the delay in releasing the
information, Dubovsky said, “One of the issues is that there were a
number of collaborators on the study, and all need to review and approve
the release of the results prior to us providing them to the public.
That process is under way, but is slower than we initially realized.”
Denver Water is looking at the effects recycled water has on plant
life, to assess any unanticipated detrimental effects from its use on
city property. While not limited to City Park, any evidence of
irregularities could shed light on a situation that is long on theory
and short on smoking guns.
A Parks Department release said,
“There is concern about increased salinity and the potential impacts on
our trees. There are certain species of trees that are more sensitive –
ponderosa pine, blue spruce, white pine, etc. that we feel the most
concern for.
“It is our goal to closely monitor all tree species
to determine impacts, and we’ll take actions to protect trees and
minimize damage whenever possible. At this point we have not decisively
determined if trees have or have not been impacted by the change in
water.”
One critical piece of information that has been
lacking in the search for answers is detailed historical data about duck
deaths in City Park prior to 2004. If a trend can be established
showing spikes in bird mortality since the switch to a new water source,
it would give credence to the theory that the recycled water could be
the problem.
Alan Polonsky is an environmental analyst with
Denver’s Department of Environmental Health. Polonsky says the avian
deaths in City Park have been going on “for decades,” but doesn’t have
hard facts to present. “I’d love to have that information on numbers and
species of birds, but the long-term story is anecdotal,” said Polonsky.
“It’s been a problem for the 12 years I’ve been here. I ask guys who
worked here for 20 years before me and they say the same thing. The
people who would have the data are at the zoo.”
George Pond is
vice president for planning and capital projects for Denver Zoo.
Responding to a call from The Profile, Pond stated, “We do have detailed
records, but the way it’s compiled is not segregated to Duck Lake, and
we haven’t had time to break things down. Anecdotally our head
veterinarian has made the comment that the past couple of years have
actually been good years – with relatively low mortality rate for what
we’re used to.
“One of the significant things I would say is that
the island at Duck Lake is one of most significant rookeries for
black-crowned night-herons and double-breasted cormorants in the region.
The bulk of the mortality we see has nothing to do with things like
botulism and other issues ascribed to the lake and water conditions. The
lake has hundreds and hundreds of nesting birds and they naturally have
a mortality rate during the nesting and fledging of the young. What
we’ve been seeing is considered a natural mortality rate based on the
number of birds out there in any given year.”
Pond does
acknowledge that water conditions in the lake have deteriorated
dramatically over the years and do contribute to the avian botulism that
claims Duck Lake fowl every year.
“Botulism essentially is
present in the lake and becomes a more active problem based on some
environmental conditions. When we get long stretches of hot temperatures
it starts to increase, and it’s cyclical. We remove (dead bird) bodies
from the lake on a regular basis because the botulism ends up being
spread through the process of decaying carcasses of birds that have died
of botulism and the maggots that feed on them. The maggots are eaten by
other birds and animals, and the cycle goes on.
“It’s important
to put this into context,” Pond concluded. “It makes obvious sense that
people are concerned. No one more than the Zoo and Parks Department.
We’ve been working on this for years. The (lake reconstruction) work
under way is critically important to address these very issues. Things
are starting to come together right now.
Addressing the recycled
water issue directly, Pond said, “I have not been presented with any
data or analytical results that would lead me to believe that (the
switch to recycled water) has had a major impact. This is an ecosystem
that has to some extent been in peril for many years, and overlays that
switch. (The avian deaths) absolutely predate the switch.”
For
now, without an organized set of relevant statistics and scientific
data, the debate – and the bird deaths – will continue. |
