Powered watercraft, jet skis and any boat that needs to be brought in on a trailer will be banned from Standley Lake this summer for fears that non-native mussel species could be introduced.

The city issued the ban March 19 after a review of boating records showed that 24 boaters had broken the city's quarantine protocol in 2018, using their boats in lakes and ponds as far away as Lake Powell within days of putting their boat into Standley Lake.

“We cross-compared launch data from across the state — Colorado license numbers and trailer numbers — with our own permit holders and based on that we found some of our permit holders had launched on other lakes and then returned to Standley Lake,” said Jodie Carroll, interim communications director for the city. “A number of our permit holders circumvented our protocols by manipulating their tag in some way.”

A further check of records showed some of the quarantine scofflaws had taken their crafts out to Arizona, Utah or Wyoming, Carroll said.

The city has a strict decontamination policy, requiring all boats be sprayed and inspected before they are put Standley Lake. Big craft, with bilge tanks and motors that can't be sprayed or inspected easily, must be kept in quarantine for 35 days before they can be used in Standley Lake.

The concern is that non-native Quagga or Zebra mussels could attach themselves to a boat and get introduced to Standley Lake. The mussels can destroy local ecosystems, clog drinking water pipes and cause algae blooms that threaten water quality.

The invasive species have not been found in Westminster's drinking water supply yet.

“Standley Lake is the drinking water supply for roughly 300,000 people in Westminster, Northglenn and Thornton,” Public Works Director Max Kirschbaum said in a written statement. “Water comes directly from the lake into our treatment system. If these mussels establish themselves in the lake, there would be significant, on-going costs to keep our system running. Protecting our community's water supply will always be the chief concern.”

The city had 483 trailered watercraft registered to use Standley Lake in 2018. A review of 2018 boat launch data found that as many as 24 boats circumvented the quarantine process. Boat owners launched the boat on other lakes, in some cases multiple times, and then launched on Standley Lake only days later. Trespassing notices are being issued to several of those owners.

“The Standley Lake boating community has largely been a terrific partner in helping protect these waters,” Parks, Recreation and Libraries Director Jason Genck said in a written statement. “Until we can determine if there's a way to ensure these types of boats won't pose a substantial risk at the lake, we need to put these activities on hold immediately and indefinitely.”

All 2019 permits that have been issued for trailered boats have been canceled and no additional permits will be sold. Individuals who already purchased a 2019 permit are being notified and will receive a full refund.

Permits can still be purchased for non-trailered watercraft such as kayaks, canoes, rafts and paddleboards. Those types of watercraft will still have to go through the city's on-site decontamination procedure.