Working to Find Ways to Reduce Selenium In Our Locally Affected Waterways
History of Selenium
In 1983, incidences of mortality, deformities, and decreased
reproduction in fish and aquatic birds were first discovered by the
U.S. Fish and Wildlife Service at the Kesterson Wildlife Refuge in the
western San Joaquin Valley, California, where irrigation drainage
waters with high concentrations of selenium were collected. Due to
concerns that problems with selenium toxicity may not be confined to
the Kesterson Refuge, in 1985, the U.S. Department of the Interior
began a program to study the effects of irrigation drainage on the
water quality of the Western United States.
Subsequent investigations by the National Irrigation Water Quality
Program (NIWQP) and the United States Geological Survey (USGS) in
1987-88 indicated that irrigation drainage from the Uncompahgre Project
along the Western Slope of Colorado, a Bureau of Reclamation (BOR)
irrigation project, might be a primary source of selenium, dissolved
solids and other constituents to the Gunnison and Uncompahgre rivers,
and Sweitzer Lake. Additional studies conducted by in 1991-93, found
that about 64 percent of water samples collected from the lower
Gunnison River and about 50 percent of samples from the Colorado River
near the Colorado-Utah line exceeded the U.S. Environmental Protection
Agency (EPA) selenium criterion of 5 m g/L (micro grams per liter) for
protection of aquatic life.
Based on these results it appears that drainage from the Uncompahgre
Project and the Grand Valley may account for as much as 75% of the
selenium load to the Colorado River near the Colorado-Utah line. The
primary source areas for selenium were determined to be the eastern
side of the Uncompahgre Valley, and the western one-half of the Grand
Valley, where extensive irrigation is located on Mancos Shales (see map).
SELENIUM STANDARDS ARE AMENDED & THE TMDL PROCESS BEGINS
On July 14, 1997, the Colorado Water Quality Control Commission
amended the Classifications and Numeric Standards for the Gunnison and
Lower Dolores River Basins (Regulation No. 35). These amendments
included the adoption of new standards for selenium and the adoption of
temporary modifications for selenium standards in four segments of the
basin. These segments are now included in the Colorado 303D list of
"impaired waters" (see map of targeted segments). Section 303D
of the Clean Water Act requires States to identify waters that do not
or are not expected to meet applicable water quality standards with
technology-based controls alone.
Once listed, the State is required to prioritize these waters,
analyze the causes of the water quality problem, and allocate the
responsibility for controlling the problem. All stream segments listed
on the 303D list are then subject to analysis called the Total Maximum
Daily Load (TMDL) process. The TMDL is an estimate of the greatest
amount of a specific pollutant, in this case selenium, that a given
waterbody or stream segment can receive without violating water quality
standards.
As part of the TMDL process, the State must quantify the pollution
sources and determine allowable loads to both point and non-point
pollution sources. A point source is defined a pollution coming from a
single identifiable source, such as effluent from a sewage treatment
pipe. Non-point source pollution is pollution discharged over a large
land area, not from one specific location. This may include drainage
from irrigated areas or suburban lawns, as well as stormwater runoff,
and soil erosion. In the case of non-point sources, voluntary controls
or locally enacted controls are necessary to implement the TMDLs.
This is where the Gunnsion Basin / Grand Valley Selenium Task Force comes in. We
are a group of private, local, state and federal agencies committed to
finding ways to reduce selenium and aid in the development TMDLs, while
preserving the viability and lifestyle of the Lower Gunnison Valley.