After additional zebra mussels were found in Highline Lake in October 2023, a two-phase plan has been implemented to eradicate mussels from the lake.
EarthTecQZ, an EPA-registered copper-based molluscicide, will be used to treat the water in November 2023. These treatments will contain a higher concentration of the chemical than used in March 2023.
Highline Lake will be lowered, beginning in January 2024, and eventually drained in late 2024. As the plan currently sits, the lake will refill in 2025. [See press releases for this project below.]
On September 14, 2022 a single adult zebra mussel was detected on an artificial substrate at Highline Lake by the Aquatic Nuisance Species (ANS) Sampling Monitoring Team.
On October 21, 2022, 5 additional adult zebra mussels were found on a work boat that had been slipped in Highline for the majority of the summer and an additional single adult was found on the west boat ramp.
On October 23, 2022, 3 more adult mussels were found when the east boat ramp dock was removed from the water.
On November 15, 2022, 2 adult zebra mussels were found in Mack wash below Highline.
These subsequent detections are indicative of an established population of zebra mussels in Highline and as a result Highline is now considered “Infested” with zebra mussels. Surveys of the Colorado River and Highline Canal upstream of Highline Lake did not provide any evidence to indicate there is an established population upstream of the reservoir.
Over the winter, Highline Lake was lowered approximately 30 feet to expose areas along and near the shoreline to kill zebra mussels through the natural processes of desiccation and freezing. CPW then applied EarthTec QZ, an EPA-registered copper-based molluscicide, to the lake on February 28, 2023 and on March 15, 2023.
During the summer of 2023, all vessels were inspected (and decontaminated if necessary) prior to launch and ALL vessels were decontaminated prior to exiting the park. The Aquatic Nuisance Species (ANS) team at Highline decontaminated more than 2,100 vessels.
On October 1, 2023, during routine work to remove buoys from the water in preparation for winter, five additional zebra mussels were located in Highilne Lake. Continued work on October 12, 2023 yielded more mussels and a two-phase plan was developed to further eradicate mussels from the lake.
On November 3rd and 6th, EarthTecQZ will again be applied to Highline Lake but in higher concentrations that the spring treatments. Highline Lake will be lowered and emptied, beginning in January 2024. The lake will not be open to motorized vessels during the 2024 season and additional closures may be announced at a later date.
During treatment, Highline Lake is not open to fishing and it is not recommended to consume dead fish from the lake. [Mack Mesa Lake is a separate body of water, has not tested positive for mussels, and is not being treated with EarthTecQZ.]