WITH THE notable exception of Superfund sites and the occasional bridge collapse, rarely are failures of public planning, administration and good sense as glaringly visible as what is unfolding right now in the suburbs of D.C., where a $5.6 billion, three-decade partnership to build a 16-mile light rail line just north of the nation’s capital is on the verge of collapse.

Midway through the massive Purple Line construction project, intended to connect Maryland’s two most populous localities, Montgomery and Prince George’s counties, and revitalize run-down neighborhoods, contractors are packing up and preparing to quit the job amid a dispute over delays and cost overruns with the state. That would leave miles of ripped-up roadways and half-finished bridges and tunnels — a tableau of dysfunction and a fiasco for all to see.

Amid this blight, there is radio silence from Gov. Larry Hogan (R), for whom the Purple Line was a signature example of his ability to build major infrastructure in partnership with the private sector. The governor, said a spokesman, supports his transportation secretary’s “efforts to get the project done and protect taxpayers.”

Actually, at this stage at least, this is on Mr. Hogan. It is true that a specious lawsuit intended to block construction, baseless in law and logic, caused nearly a year’s delay at the outset. Yet whoever and whatever may cause the collapse of one of the nation’s first public-private partnerships for a major transit line, it was the governor’s initiative to go ahead with the project. And it is his problem to fix.

Maryland transportation officials insist the rail line will go forward, somehow. But if the deal with the private partners collapses, as seems imminent, the obstacles to reviving the project will be daunting. The Purple Line, meant to carry passengers starting in March 2022, might not be operational until 2026. Even that timeline could slip.

Among the unresolved issues is how the state would finance the remaining $1 billion in construction to finish the work — the portion the private partners, Meridiam, Fluor and Star America, were to have paid and borrowed upfront. Facing massive budget cuts owing to the pandemic’s ruinous impact on projected tax revenue, the state may have to cannibalize funds from highways, MARC service, the Port of Baltimore and other transportation links to maintain progress on the Purple Line, lest more than 100 subcontractors walk off the job, along with more than 700 workers.

The bigger question is how to proceed generally — whether the state itself could or should manage a massive and complex project to completion, or hire a contractor, or try to find a new private partner with the resources to resume full-fledged construction, and assume the risk of further mishaps, in return for decades of future profits.

Officials in Annapolis have offered no answers, beyond saying it may take six months to figure out. As for Mr. Hogan, his silence is deafening.

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