Less than two weeks after the Loudoun County Board of Supervisors voted to commit to Metrorail’s Silver Line extension into Loudoun County, the project officially took a step forward as the Metropolitan Washington Airports Authority began the process of selecting a contractor for the second phase of construction.

On Friday, the MWAA announced that it had issued a request to solicit statements from potential bidders to oversee construction of the 11.5-mile extension from Reston to Dulles International Airport and west to Route 772 in eastern Loudoun.

Patrick Nowakowski, executive director of the Dulles Corridor Metrorail Project, said in a statement that MWAA would select “a highly qualified team to design and build Phase 2 in the most cost-effective manner.”

The contract could be awarded as soon as late spring, and construction of Phase 2 is estimated to be completed about five years after that, MWAA officials said.

Statements of qualifications will be gathered from prospective bidders and then narrowed down to no more than five teams, the MWAA said. The contract will be awarded to the team that meets the requirements and has the lowest price, officials said.

The first phase of the Silver Line’s development, expected to be completed by August 2013, runs from Tysons Corner to Wiehle Avenue in Fairfax County. When both phases are finished, the line will have 23 miles of rail between East Falls Church and Ashburn.

As the MWAA moves forward, Loudoun leaders are also preparing for the work ahead. Along with the July 3 vote to participate in the second phase of the Silver Line, supervisors voted to begin the process of establishing a special tax district to fund Loudoun’s share of the project costs, about $270 million toward construction and about $17 million in annual operating costs, beginning in 2019.

The tax district, proposed by Supervisor Shawn Williams (R-Broad Run), would encompass commercial and undeveloped properties surrounding the Metro stations. The district is described as “hybrid,” because, under the plan, it would have multiple subsets: Properties within a half-mile of each Metro stop would pay a tax of 20 cents per $100 of assessed value; properties in the outer portions of the district would probably pay less than 20 cents per $100 of assessed value. The board also supported creating an airport district surrounding Dulles Airport, which could be used to fund operating costs after the county’s debt service for the project has been paid off.

Almost all existing residential property is excluded from the tax district, with the exception of 37 parcels. Future residential development within the tax district would be subject to rail taxes.

As soon as the county has drafted an ordinance to establish the tax district, the ordinance will be advertised, and county residents will have a chance to voice their opinions. A public input session will be scheduled no later than Nov. 1, officials said. The county might arrange for additional public input, they said.

Many Loudoun residents have already responded to the county’s approval of the second phase of the project, Supervisor Matt Letourneau (R-Dulles) said.

“The reaction to the vote has been overwhelmingly positive,” Letourneau said. “I think, for my constituents, it has been a mixture of relief and, for some, surprise that it was so close.”

Letourneau, chairman of the board’s Economic Development Committee, said his conversations with business leaders after the supervisors’ vote to take part in the project has confirmed the importance of Metro as a lure for companies considering Loudoun.

Supervisor Kenneth D. Reid (R-Leesburg), who cast the deciding vote in favor of the project despite his long-standing opposition to it, has received more mixed feedback, he said.

“I have received mostly positive comments. Quite a lot, in fact,” he said. “But I have been getting a lot of invective, mostly from Republicans.”

Some of those comments, he said, crossed the line from disagreement to personal attacks and even veiled threats. One Facebook message suggested that Reid should be “careful” when he starts his car.

Reid offered the reasoning behind his vote in a statement on his Web site, noting that the special tax district — which would place the financial burden of the Silver Line extension on the shoulders of those most likely to benefit from proximity to the stations, without instituting a countywide tax — was the deciding factor that enabled him to reverse his position.

In his online statement, Reid saluted the intentions and efforts of the rail opponents with whom he was once allied, including Loudoun Opt Out, which he said did “a stellar job” of grass-roots lobbying.

That sentiment is somewhat less than mutual: Reid said that David LaRock has referred to Reid as “Kenedict Arnold” and suggested that Reid should “reconsider, re-vote or relocate.”

Reid said the Leesburg Town Council’s support of the project, contingent on the exclusion of a countywide tax, also encouraged his vote. He added that the choice to support the project was the “most difficult decision” he has faced in his six years in office.

“I am sure many are unhappy with my vote, and some are vowing to unseat me,” his statement said. “But I ask for your patience and understanding as we moved forward to make Leesburg and Loudoun great places to live, work and play.”