Huge excess of office space makes air rights development unlikely over Dulles Toll Road
By Peter Samuel
Metropolitan Washington Airports Authority (MWAA) operators of the Dulles Toll Road in Northern Virginia have decided against building $34m of foundations for future air rights development over the toll road in Reston. The huge excess of office space in the Dulles Corridor plus plentiful land for new development make it unlikely air rights will be taken up in the next twenty years, a report concludes.
Any delay beyond 2028 would make the foundations investment a loser.
The issue of building foundations for an air rights development arose because MWAA is moving into stage 2 of a metro rail line in the median of the highway. Extensive air rights development across the pike was suggested alongside Reston Parkway rail station.
The Dulles corridor extending 11 miles, 18km from Tysons Corner at the Beltway to the front of Washington Dulles International Airport consists of 4 lanes each direction of the Dulles Toll Road on the outside, two lanes each direction (expandable to 3 lanes) of a Dulles Airport Access Road presently untolled, with a heavy metro-rail line being built in its median. Overall width is about 300ft.
Planning was for the first air rights development at Reston Metro station, about midway in the corridor.
4 million square ft of commercial and residential space (2.2m commercial, 1.8m residential) was envisaged at a cost of $1.5b. This would be mounted on a platform or deck approximately 1250ft long x 300ft - a 400k sf deck.
Three stages were envisaged - the foundations and barrier walls now while the rail line is being built, next the deck structure, and third the buildings on the deck.
Five under-deck corridors, or three
The foundations would consist of lines of continuous foundation barrier walls poured atop auger pile caissons. According to the original plan there would have been six such foundation barrier walls built providing five corridors underneath the air rights deck - two for the tollroad's 4-lanes each direction, two for the Dulles Airport Access Road's 3-lanes (after third laning) each direction, and the new metro rail pair of lines.
The spans between the walls would be around 60ft.
However the recent study suggests that if the foundations are deferred it will be possible to go to a three corridor design to reduce the disruptive effects of construction work. Under this alternate plan there would then be a single 150ft span over both directions of the airport access road and the rail line, and the same smaller 60ft spans over each direction of the tollroad. (see sections at end of our report)
The three-corridor design with the 150ft central span is 30% more expensive to build than the five corridor 60ft spans, but far less disruptive to road and rail traffic in the construction zone.
Unviable sustainability, unsmart smart growth?
Such dense 'transit-oriented development' around metro stations is all the vogue among county planners, and other local enthusiasts for 'smart growth' and 'sustainability.'
However it's financial viability looks doubtful.
MWAA obtained a forecast from the George Mason University Center for Regional Analysis which predicted a continuing surplus of commercial office space in the corridor. They estimate only after 2040 will existing and planned commercial space be taken up. 2030 demand they put at 18.8msf (million square feet) vs existing and planned 22.4msf. Even 2040 demand they put at only 21.4msf.
This makes it extremely unlikely anyone would invest in the more expensive air rights development, and the MWAA would be left with a sunk investment in foundations yielding no return on capital.
MWAA has therefore decided on no investment now.
Copies of the reports: