Before they can build the six-lane Triangle Expressway across southern Wake County, state officials must show that the highway won’t do serious harm to two rare species of mussels that live in streams there.
The centerpiece of the state’s strategy is a laboratory that would operate as a mussel hatchery. The N.C. Department of Transportation has proposed to spend $2 million to upgrade a lab used by N.C. State University researchers at Historic Yates Mill County Park and provide another $3 million for mussel propagation over five years.
The goal would be to raise the two species of mussels – dwarf wedgemussel and yellow lance – and place them in streams in Wake County and beyond where they are likely to survive on their own.
The two types of thumb-size mussels – one on the Endangered Species List and the other likely headed that way – have cast a large shadow over the $2.2 billion final leg of the 540 loop around Raleigh. The endangered dwarf wedge, found in small numbers in the Swift Creek watershed south of Garner, was the reason NCDOT considered an alternative path for the road known as the Red Route, which would have largely avoided the mussels while plowing through subdivisions, businesses and churches in Garner.
Instead, NCDOT consulted the U.S. Fish and Wildlife Service on other ways it could minimize the highway’s impact on the mussels. These include eliminating storm drains on bridges over Swift Creek and building containment areas near the creek to capture any spills that might occur on the road, said Jared Gray, the environmental program supervisor for the N.C. Turnpike Authority, which will operate the toll road.
Gray said scientists have been talking about the need for a mussel hatchery in Eastern North Carolina for years, and the 540 project provided an opportunity to establish one.
“They were looking to build it, and we were needing to build the project,” Gray said. “And so in that informal consultation with the Fish and Wildlife Service, we both agreed that this would be a conservation measure for potential effects on the dwarf wedge and yellow lance mussels.”
Opponents of the highway question whether the hatchery idea will work. Kym Hunter of the Southern Environmental Law Center in Chapel Hill says five years isn’t enough time to commit to the effort and that it’s not clear the highway won’t destroy the suitable habitat in the Swift Creek watershed where the mussels could be released.
“The entire purpose of the Endangered Species Act is to preserve species in the wild, in their natural habitat,” Hunter said. “Placing them in tanks in a propagation facility does not accomplish this. Similarly it would not be legal to just round up all the sea turtles and place them in a zoo.”
But Gary Jordan, the biologist with the Fish and Wildlife Service who has worked with NCDOT on the 540 project, says propagation is one of the most needed tools for mussel recovery. Jordan says mussels have declined in the Swift Creek watershed as the area has become more suburban but says that decline appears to have leveled off.
“So we are hopeful that we still have enough suitable habitat out there that we can put dwarf wedgemussels and yellow lance mussels back into,” Jordan said.
Jordan’s agency is evaluating a report on the highway’s likely impact on the mussels that was drawn up by NCDOT and the Federal Highway Administration, which will provide some funding. The Fish and Wildlife Service has until April 20 to decide whether the highway will “jeopardize” the continued existence of the mussels – a decision that will determine whether the project can move forward as proposed.
“Jeopardy opinions are rare because we can usually modify projects to avoid jeopardy. So we don’t have those happen very often,” Jordan said. “I can’t tell you where this one is going just yet.”
Scientists have learned how to reproduce freshwater mussels in captivity in labs like one at NCSU’s College of Veterinary Medicine. For 17 years, NCSU researchers have been propagating mussels on a small scale, and their lab in a metal building known as the mussel barn is one of only about a dozen places in the country where this kind of work is done, said Jay Levine, a professor of epidemiology and public health at the vet school.
As a group, freshwater mussels and other aquatic invertebrates are among the most endangered animals in the world, Levine said. Not only are mussels sensitive to environmental pollution, but they can reproduce only with the help of certain kinds of fish that carry the mussel larvae on their gills as they grow to a point where they’re ready to settle in the mud and live on their own.
Levine and the NCSU lab’s propagation coordinator Chris Eads have learned the nuances of this process well enough to replicate it in the mussel barn. It starts by determining what kind of fish each species of mussel relies on to carry its larvae; the dwarf wedgemussel depends on a couple of species of darter – the Johnny and the fantail.
The scientists begin by finding female mussels in the wild whose eggs have been fertilized by a nearby male, then place them in about four liters of water containing the proper fish. The larvae released by the female mussels find their way to the fish gills, where each one looks like a tiny Pac-Man about the size of a grain of salt.
The fish are then moved to small aquariums where they’re fed and kept happy while the larvae develop into young mussels, a process Levine likens to the metamorphosis of a caterpillar larvae into a butterfly. After two to four weeks, the juvenile mussels drop off the fish gills and are caught in a mesh netting.
Scientists count the tiny mussels, and then put them in their own aquariums where they’re given a steady diet of algae. They’ll remain in those tanks until the following spring, when they’ll be put in a pond or sent to a state fish hatchery in Marion to grow out. It will take another one to two growing seasons before they’re on the cusp of being reproductive adults and can be either released to the wild or begin the whole process over again.
Freshwater mussels like the dwarf wedge and yellow lance are an important part of the environment, Levine says; they help improve water quality and provide food for otters and muskrats and other creatures.
But their odd symbiotic reproduction makes them cool by itself, he says. Some species, including the dwarf wedge, will work to attract fish with “lures,” part of their bodies that stick out of their shells and wave in the water like tiny fish or insects that the host fish might want to eat.
“They’re kind of this living wonder in our streams,” Levine said.
‘A lot to learn’
The new hatchery created and run with NCDOT’s money would be known as the Yates Mill Aquatic Conservation Center. While the center will begin with the mission of propagating dwarf wedge and yellow lance mussels, it can easily branch out to involve other endangered mussel species, said Rodger Rochelle, the Turnpike Authority’s chief engineer.
“You’ve got a major research university involved,” Rochelle said. “There’s going to be a lot to learn.”
NCDOT uses several methods to try to make up for the environmental damage done by building highways. It restores streams and wetlands and buys conservation easements in areas far beyond the path of the new road. But Rochelle says the Yates Mill center may be a first for the department.
“We have funded research on the topic,” he said. “But in terms of actually providing funding to develop a propagation facility, this is the first to my knowledge.”
NCDOT describes the proposed mussel hatchery in the Final Environmental Impact Statement, a report that spells out the possible effects of the final 28.4 miles of the Triangle Expressway on the natural and human environment. The report was released Dec. 22, and the public has until Feb. 1 to comment on it.
Meanwhile, the Turnpike Authority and NCDOT will hold three meetings and a hearing in February to provide information about the highway, including preliminary designs, and gather feedback from the public. The three public meetings will take place:
▪ Tuesday, Feb. 20, from 6 to 8 p.m. in the cafeteria of Holly Springs High School, 5329 Cass Holt Road.
▪ Wednesday, Feb. 21, from 6 to 8 p.m., at the Barwell Road Community Center gymnasium, 5857 Barwell Park Drive in Raleigh.
▪ Thursday, Feb. 22, from 4 to 6:30 p.m. in the Southern campus of Wake Tech Community College, 9101 Fayetteville Road, Rooms 212-214 of Student Services Building L. The meeting will be followed by a formal hearing at 7 p.m., with a presentation and the opportunity for the public to speak.
Written comments also can be submitted at the hearing or the public meetings. For more information about the project, including a link to the full Final Environmental Impact Statement, go to www.ncdot.gov/projects/complete540/.