BURLINGTON – Developers of a proposed high-voltage transmission line bringing Canadian hydropower through Vermont presented their vision at a three-hour symposium in Burlington on Thursday morning.
Transmission Developers Inc. is seeking approval to build a 154-mile line from the Canadian border at Alburgh, southward under Lake Champlain, and then across central Vermont to a converter station in Ludlow using existing rights-of-way. The power would then be released to the New England grid. The line would carry 1,000 megawatts of DC power, enough to provide electricity to a million homes, according to the developers.
The plan for a $1.2 billion, privately financed New England Clean Power Line was presented at the ECHO Lake Aquarium and Science Center. TDI depicted the project as a “green” technology that would benefit Vermont’s tax base, spur economic growth with reduced energy costs, and diversify the state’s energy sources.
The presentation was both comprehensive and short on detail. To date, most plans and the studies that inform them are preliminary. One application for a federal permit was filed in May. Company officials said more specific information will be available in public filings to be made later this fall with the state and the Army Corps of Engineers.
Project leaders want to gather more questions from stakeholders, TDI president and CEO Donald Jessome said, so they can submit the most responsive permit applications possible. Several meetings and public forums already have taken place, he said.
Thursday’s symposium focused almost entirely on the 98-mile underwater portion of the line, rather than the overland portion. Major topics included the mechanics of moving high-voltage DC power, underwater installation techniques, considerations that went into developing the lake route, and environmental impacts of the installation – from electromagnetic fields to the heat the cables would produce.
Two unanswered questions revolved around Lake Champlain’s environmental health: whether the phosphorus that’s kicked up in the course of drilling would add to the lake’s nutrient load, and how the project’s thermal gradient may impact mercury levels.
The process, in a nutshell, is to bundle two cables and one fiber optic line, which then will be strung through heavily armored steel casing designed to protect both the equipment and the surrounding environment. In parts of Lake Champlain deeper than 150 feet, the cable would be laid on the lake floor. In shallower depths, the cable would be buried about four feet below the lake floor.
About 40 miles of the underwater transmission lines would be buried and 58 miles would lay on the lake floor. The weight of the cables and casing, however – more than 50 pounds per linear foot – ultimately would cause even the unburied conduit to sink. Slack would be built into the cable length to accommodate this effect.
The trench for burying the cables would be horizontally drilled, then “plowed” with special equipment. The process would kick up sediment that could contain contaminants.
High levels of phosphorus, most notably from agricultural runoff, are linked to algal blooms that threaten the health of the lake as a wildlife habitat and a source of public drinking water. The U.S. Environmental Protection Agency has demanded the lake’s phosphorus load be reduced by 36 percent, but a plan for achieving – and paying for – that goal has yet to come.
Sean Murphy, a project consultant from the firm HDR, Inc., said Wednesday morning he did not believe that phosphorus released into the water from the installation would count toward the EPA’s Total Daily Maximum Load because the process wouldn’t add new phosphorous to the lake. It would merely release phosphorus already present, and scientific modeling shows the material will likely settle back to the lake floor in a safe period of time, Murphy said.
Murphy did not know the total number of pounds of phosphorus that might be released. He added that it was unclear if specifics would be released, due to concerns of proprietary information.
Christopher Kilian, of the Conservation Law Foundation, was not assuaged by Murphy’s assurance that the formulas employed were reliable. He urged the developers to lay out more of the math that informed their assessment of the project’s environmental impacts.
“It would be good to know the technical basis, as opposed to hand-on-the-Bible,” Killian said. “That’s not going to be a good answer.”
Kilian also was not pleased by the revelation that, to date, no study had been conducted of methylmercury, the most toxic form of mercury, according to the U.S. Geological Survey.
William Bailey, of the consulting firm Exponent, said thermal gradients surrounding the surface cables would be less than one degree in most instances, depending on the flow of the water around the cables. In some cases, he said, there could be a more than one degree increase alongside the cable, in an area about six inches tall by seven feet wide.
Kilian said even incremental heat can release methylmercury. “So creating a methylmercury machine would be a great concern,” he concluded
Jessome said the purpose of the symposium was to hear such concerns, which the company will use to inform its additional modeling work and remaining permit applications. They want to anticipate and respond to all questions in advance, he said.
Those include public safety, decommissioning, shoreland sounds from the project’s 24-hour installation schedule, and impact on the lake’s fauna, he said.
TDI’s projected timeline is to commence operations by 2019 following a two-year construction period. The rest of the time until 2016 will be consumed by permit applications and reviews.
TDI, financed by the global investment and advisory firm Blackstone, began permitting in 2010 for a similar project in New York called the Champlain Hudson Power Express. That project, valued at $2.2 billion, would bring about 1,000 megawatts of high-voltage DC power under Lake Champlain to markets in New York.
A $117 million public benefit fund, separate from any mitigation actions and to be paid out over the course of 35 years, was created in New York. Project officials said they would propose creating a similar fund for a transmission line in Vermont.
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