Amid all that earnest activity, however, the nagging question remains: what to do with the two-mile section of I-84 just outside downtown, which in an ironic reference to past glory is known as the Aetna Viaduct. Its projected lifespan ended in 2005, and engineers are now worried about catastrophic failure. Replacement options under consideration include just fixing the viaduct so it is in a state of good repair ($2 to $3 billion), or lowering the highway with a series of decks ($4 to $5 billion). A study commissioned by the city calls for a more artful integration of the urban streetscape and the area’s existing rail and bus rapid transit system, known as CTfastrak. From there, things get more creative. Connecticut Congressman John Larson seeks to bury not only I-84 in a tunnel, Big Dig-style, but also I-91 just to the east of downtown, in the process reclaiming waterfront property along the Connecticut River. The estimated price tag: at least $10 billion.