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Since 2012, the Colorado Department of Health and the Environment has listed Gore Creek as an impaired waterway due to low aquatic life.

In the ensuing years, the town of Vail and the Eagle River Water and Sanitation District have been working to get the waterway off the list. Restore the Gore activities have included education efforts around pesticides and landscaping as well as the recent installations of gutter bins to reduce pollution flowing through its its stormwater drains.  

One of the main metrics the two entities use to track the progress of such efforts is the health of macroinvertebrate species in Gore Creek, Black Gore Creek, Red Sandstone Creek and Booth Creek. To track the abundance and diversity of these species, the water district conducts sampling at several sampling locations each September. This data has been collected since 2009 and includes eight sites on Gore Creek.

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According to the Gore Creek , these “bottom-dwelling, or benthic, macroinvertebrate communities represent one of the most valuable indicators of water quality and aquatic conditions.”

Pete Wadden, the town’s watershed health specialist, recently presented the full data from Eagle River Water and Sanitation District’s 2021 sampling as well as gave some insight into the 2022 results to the Town ߣÏÈÉú.

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Overall, samples from the last two years showed that the creek is “moving in the right direction, albeit at a modest pace,” Wadden said, later adding that the data shows an “upward trend over time, but it’s very gradual and still in most cases, in most years, pretty far from reaching what CDPHE defines as attainment.”

“We have about 100 different species of macroinvertebrates in Gore Creek; most of these are insects who spend their larval stages in the water and emerge as winged insects as adults. This also includes some worms and crustaceans and also snails and things like that,” Wadden said.

The 2021 sampling included 31,630 individual insects. The sampling found 15 mayfly taxa, 16 stonefly taxa and 16 caddisfly taxa — which are “called out” in the data because those orders of insects are the most pollutant-sensitive, Wadden said.

“When we see those in the creek, it’s typically a pretty good sign,” he added.

In 2018, the state updated its methodology to grade the aquatic macroinvertebrate species in the creek, which has led to a decline in the number of sites that are “passing” or not impaired.

The previous version (version three) was “more forgiving on Gore Creek,” largely because this version gave the creek credit for having one individual bug from the “sensitive taxa,” Wadden noted.

However, the state’s updated methodology (version four) “takes into account the abundance of those sensitive species,” Wadden reported.

“In some ways, it’s a better gauge but it also doesn’t shine a great light on Gore Creek,” he said.

Under version four, all the sites tested are “pretty far from attainment,” Wadden said, even as they show improvement year over year.

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In addition to seeing overall gradual improvement on Gore Creek, Wadden pointed out that the data shows the impact of development on the aquatic life.

“Overall, the trend is that the undisturbed places on Gore Creek, like above Black Gore Creek, are extremely healthy and are probably what we would see in Gore Creek if there was no human influence, no pollution, no impacts whatsoever. As we move into the developed parts of Vail, those aquatic invertebrate numbers drop as a result of non-point source pollution throughout town,” he said.

While the data shows the amount of progress that still needs to be made, the one “glimmer of hope” is Red Sandstone Creek, Wadden said.

Red Sandstone Creek — which Wadden described as a microcosm of Gore Creek — used to show the same impairments at downstream sites as Gore Creek has shown significant improvement in the past four years. This trend was seen in both the 2021 and 2022 macroinvertebrate sampling.

While Wadden said he has not had confirmation, he said he suspects the reason for the turnaround of the tributary is that one or two big properties in the area eliminated the use of pesticides.

Eliminating pesticides — at least within 100 feet of the creek bed — Wadden later reported is the leading thing that could have the biggest positive impact on the stream health in town.

“Pesticides are the one thing we can control that continues to be a serious problem in Gore Creek,” he said.

Wadden reported said the data is evidence that the town is “slowly making steps in the right direction.”

“The investments of time and plants and money that this council has put into the creek have shown some improvements,” he said.

Mill Creek die-off

The 2021 macroinvertebrate sampling was conducted the week before a large die-off of fish was found in Mill Creek and Gore Creek.

Earlier this month, the state concluded its investigation of the incident, which found that from Sept., 17-20, 2021, Vail Mountain left open isolation valves on its snowmaking system and released approximately 2 million gallons of water containing hazardous substances into both creeks. The spill impacted numerous aquatic species including fish, algae and aquatic insects along 1.5 miles of the waterway.

Additionally, the Colorado Natural Resources Trustees approved a $275,000 settlement with Vail Resorts — $249,000 of which will go to the state for a restoration project in the Gore Creek basin, with the remaining $26,000 going to the state’s Water Quality Improvement Fund. 

Wadden said that after the spill, there was another sampling done to see the impact it had had on the macroinvertebrate. The “stark picture” of the impact was seen in the density of the species, he said.

Immediately following the spill, Mill Creek at Gore Creek dropped from 6,000 species per square meter to less than 100.

However, in the most recent 2022 sampling, Wadden said that the results were largely the same as in 2021 before the spill and in some instances “maybe slightly better.”

“That’s really, really good news, especially following this spill,” Wadden said. “One of the things that we have in our favor when it comes to these insect species is they are mostly fairly short-lived and reproduce quickly so their populations are able to recover if the source of pollution is removed, as we can see in this case.”