Comment on whether FWP should drain Lake Elmo
By Moosetrack Megan

Posted: October 20, 2020

BILLINGS – Montana Fish, Wildlife and Parks has recommended that it drain Lake Elmo in Billings Heights next year to eradicate invasive Asian clams found there in 2019.

FWP fisheries biologists and managers have completed a draft environmental assessment on plans to address the invasive clams. The document also lists plans to improve fish habitat and add state park amenities while the lake is dry.

People are encouraged to comment on the draft environmental assessment and its recommendations by Nov. 18, 2020.

 Asian clams were found in Lake Elmo in 2019 by FWP employees training to search lakes for aquatic invasive species. Subsequent searches of an irrigation storage reservoir and ditches and rivers upstream and downstream from the lake found no other Asian clams, suggesting that they are limited to Lake Elmo. The invasive clams are found nowhere else in Montana. 

Asian clams can clog irrigation and other water system infrastructure, filter and remove important food sources needed by other species and promote the growth of bacteria and algae. Their shells are sharp, causing a safety hazard for people using the lake. 

Public comments solicited in March 2020 indicated strong support for FWP to address the presence of Asian clams in Lake Elmo and take the opportunity to improve fish habitat, access and park amenities. The 60-acre lake is the key feature of Lake Elmo State Park in Billings, which receives high year-around use for a variety of activities. 

Scientific information shows that drying and freezing is the most effective way to kill Asian clams. FWP biologists believe that draining the lake to expose all Asian clams to winter weather provides the best opportunity to eradicate them.

This fall the lake level already has been drawn down by two to three feet to try to kill Asian clams in shallow water near the shore.  Most of the clams found to date in the lake have been in less than six feet of water. Lake Elmo State Park and the remaining water will remain available to the public during this winter’s partial drawdown. The lake will refill in April 2021.

The environmental assessment recommends that FWP drain the lake completely starting in the fall of 2021, leave it dry for the winter, then refill it in April 2022.

While the lake is dry, FWP is recommending improvements to fish habitat and addition of park amenities that would be more difficult and expensive if the lake was full of water. Projects could include excavation to deepen the lake, handicap-accessible rock jetties, sunken structures for fish, a boardwalk between the lake shoreline and Lake Elmo Drive, fishing nodes along the boardwalk, work on the dog park shoreline and a sediment retention area. All projects would depend on funding and completion of engineering and planning.

The draft environmental assessment discusses the process of draining the lake, precautions to keep Asian Clams from spreading during draining, disposition of fish and aquatic species now in the water, repopulating fish in the lake in 2022 and effects of the various projects.

  The full 60-page environmental assessment, including preferred alternatives, is on the FWP website at and follow the links to “news,” “environmental assessments” and “restoration & rehabilitation.” Comments are due by Nov. 18, 2020. Phone questions may be directed to Mike Ruggles, FWP’s regional fisheries program manager, at 406-247-2961 during normal business hours. Comments may be emailed to or mailed to:

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