Straight Creek inching closer to health
DILLON – It’s going to be a long process, but the water quality in Straight Creek is slowly getting better.
The creek, which supplies municipal water to the town of Dillon and unincorporated Dillon Valley, was listed as impaired in 1998. To blame is an overload of sand washing down from Interstate 70 each spring and degrading the insect and fish habitat within the creek.
The Colorado Department of Transportation (CDOT), the Summit Water Quality Committee, the town of Dillon, U.S. Forest Service (USFS), state Department of Health and Environment, Denver Water Board and others have since worked to develop standards and implement methods to restore the creek’s health.
A group of about 40 water specialists, town and state health officials and others trekked through the woods Friday morning to see how far the cleanup effort has come in the past 12 years.
The sand, most of which derives from traction sand CDOT has spread on the interstate during the winter in the past 30 years, has slowly filled the creek bed, widening the channel and creating sand bars. Ultimately, the sand becomes embedded between smaller rocks and chokes out mayflies and stoneflies vital for sustainable trout populations.
The cleanup effort – a similar one is under way on the headwaters of Black Gore Creek at the top of Vail Pass – is expected to take 32 years and will include the creation of 30 sediment ponds, revegetation to stabilize slopes and annual maintenance. Lots of annual maintenance.
Last year, crews removed 5,100 tons of sand from three sediment ponds, all while revegetating slopes and replacing culverts.
Currently, 14 ponds along the upper reaches of the creek catch dirty water near the Eisenhower Tunnel, slow the volume of water so the sand can settle out and let the water continue into the creek.
“We need to control the source,” said Greg Laurie, a hydrologist with the USFS Dillon Ranger District. “Very dynamic streams do remove material, and in a matter of time, you see a very dramatic improvement. The stream will repair, but we have to control the sources.”
The Straight Creek watershed comprises about 20 square miles of land and generates about 11,000 acre-feet of water each year. An acre-foot is 325,851 gallons of water, or enough to cover an acre of land to a depth of one foot.
Crews began their work near the Eisenhower Tunnel, where most of the sand is deposited. Since 1991, they have constructed ponds to collect the sediment, revegetated slopes to hold sand in place and prevent it from sliding down the hill, paved the interstate shoulders to prevent erosion and installed drainage pans to divert runoff into inlets that lead to the ponds.
Stations monitor the turbity of the water, and about once a year, crews head out to various locations along the stream and collect and measure rocks. They want rocks to measure 60 millimeters at their thickest point. That rock size creates a viable environment for bugs – and the bugs attract trout.
reek are smaller than 60 millimeters, said Bill McKee, a water quality control official with the state Department of Public Health and Environment. And that’s not suitable for older trout.
“The adult trout are not growing and surviving,” McKee said. “There are three age groups, and we’d like to see five.”
Another component is prevention. CDOT officials have dramatically reduced the amount of sand they spread on the road and return in the spring to sweep it up. Salt levels in that sand are at 5 percent compared to other areas of the state where salt levels can be up to 18 percent of the mixture.
Graphs indicate that sediment levels in the upper reaches of the creek have decreased dramatically where work has been done since 1992. As expected, sediment at the lower reaches is about the same as it was in 1992.
Additionally, massive revegetation efforts on the steep slopes along both sides of the interstate are helping hold sand and dirt in place, thus preventing further degradation of the water below.
In the end, there will still be sand in the creek – some 300,000 tons of it, said Dillon town councilmember Lauren Gardner.
“It’s here, and we have to live with it,” Gardner said. “But the stability of that and control of new sand is really the goal. In 2001-2002, it was the first time in 15 years that more sand was recovered than applied. If we keep up that trend and allow the existing sand to stabilize, we’ll obviously be somewhat successful in controlling this.”
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