Utah’s push to develop the $1.8 billion Lake Powell pipeline, held up for years by political wrangling, funding feuds, reams of red tape and massive amounts of paperwork, is now being threatened by a tiny creature: the quagga mussel.

The nonnative mollusk, infesting Lake Powell since 2013, has been wreaking havoc on boating facilities and Glen Canyon Dam and is the subject of an inconvenient quarantine process to ensure that what happens in Lake Powell stays in Lake Powell.

Now the noxious shellfish is threatening to gum up permitting for the proposed pipeline after federal regulators demanded the state provide a plan for preventing the line from transporting quagga mussels across southern Utah and infesting waters along the 140-mile route.

The worry was raised in a June 13 letter from the U.S. Army Corps of Engineers, which asked the state to address quagga risks and 12 other concerns associated with the pipeline that state water officials hope will move 86,000 acre-feet a year from the Colorado River to fast-growing Washington and Kane counties.

State officials say quagga is not considered a threat to the project and “plans are in place" to prevent the spread of the nonnative mussel through the pipeline.

“Preliminary designs for the Lake Powell pipeline include a filtration system, chemical mix and coating to be applied to the intake portion of the pipeline that would help prevent mussels from entering the system,” the Utah Division of Water Resources said in a news release Friday afternoon.

The release expressed confidence in countering the quagga issue, stating that “it is easier to treat a pipe for mussels than an open body of water.”

Without intervention, though, "the likelihood that the pipeline would move quagga is 100%,” warned Jordan Nielson, Trout Unlimited’s invasive species coordinator.

Quagga’s microscopic larvae are floating in Lake Powell, where they get sucked into boats’ internal systems and moved around the lake. As they mature, the mollusks form jagged colonies on docks, rocks, pipes, virtually any hard surface.

“We could be putting them in the Sand Hollow water supply, and any pesticide used to kill the quagga could pollute the water,” cautioned pipeline critic Zach Frankel, executive director of the Utah Rivers Council. “The quagga could interfere with the project itself. They could take over the intake machinery.”

The Army Corps is now processing the Utah Division of Water Resources’ application for a permit under Section 404 of the Clean Water Act, necessary for most infrastructure projects that impact wetlands. This permit is separate from one pending before the Federal Energy Regulatory Commission, which is overseeing the pipeline’s hydropower components.

Before issuing a 404 permit, the Army Corps wants to see a plan to keep quagga from being deposited in the pipeline’s terminus at Sand Hollow Reservoir near St. George or released along the line from leaks or spills.

Nielson doubted quagga larvae, known as veligers, could survive the entire journey to Sand Hollow, but the mussel could become established inside the pipeline and disrupt its operations.

Utah law bans the transport of quagga, alive or dead, from one water body to another inside the state. In Friday’s news release, Brian Steed, head of the Utah Department o Natural Resources, emphasized the importance of containing the Lake Powell quagga epidemic.

The state "spends millions of dollars to keep quagga mussels from spreading to other Utah lakes and reservoirs from Lake Powell. It’s an extremely successful and aggressive program,” Steed said. “Keeping our water bodies free of invasive species will continue to be a priority for the state; and that focus extends to the future development of water delivery systems.”

The Utah Water Resources Board analyzed treatment options in a report released in 2016, which acknowledged quagga as a major menace.

“When present in a source water supply system, they potentially become a serious problem for operating municipal and industrial supply facilities,” the report states. “At a minimum, even the simplest colonization in a pipeline creates significant friction losses which limit pipeline discharge.”

The outlines for a final plan won’t emerge until the pipeline’s design and alignment are finalized.

“We don’t know what technology will be available when the pipeline is built. We are trying to analyze what technology we have now and what are the best ones to consider,” Marcie Larson, spokeswoman with the Division of Water Resources, said Thursday. “With water entering the intake, it would be dosed with a molluscicide. Then it would be filtered to remove other biological materials that could be repeated at proposed booster-pump stations."

The molluscicide, a chemical specifically toxic to snails and slugs, would be approved by the U.S. Environmental Protection Agency and National Park Service, she explained, and would not render the water harmful to humans.

“Our hope is the molluscicide will keep the larvae and veligers from reaching Sand Hollow," Larson said. “The intake might take physical cleaning to remove adult quagga.”

The Army Corps’ recent letter gives the state 30 days, until July 13, to provide a plan for quagga and to address a dozen other issues.

These include downstream impacts arising from the forebay and afterbay reservoirs associated with the pipeline’s hydro components; reducing the “impacts to the aesthetic quality of area along the pipeline"; reducing the effects on sensitive habitats; and restoration of stream crossings.

The corps also wants the division to provide evidence that the pipeline as currently proposed “avoids and minimizes aquatic resource impacts to the maximum extent possible.”

Editor’s note • This story has been updated with additional comments from the Utah Division of Water Resources.