Kennedy Center officials appeared before the National Capital Planning Commission Thursday to provide additional detail about its $100 million expansion project and its impact on the environment and boating traffic.

Designed by architect Steven Holl, the expansion features three pavilions with 60,000 square feet of rehearsal, classroom and performance space that will cascade down the southern slope of the arts center, ending on the Potomac River. Most of the added space will be built underground, while new landscaping will include a reflecting pool, a grove of trees and sloping lawns.

In December, the NCPC approved the preliminary plan with the exception of the floating River Pavilion, a 8,500-square foot facility moored on the Potomac that includes indoor and outdoor performance spaces and a café. The commissioners had requested information about its impact on boating traffic as well as additional design details for a pedestrian bridge over the Rock Creek and Potomac Parkway that would connect it to the existing structure.

In a 45-minute presentation, architect Chris McVoy and Kennedy Center President Deborah Rutter outlined the importance of new connections to the river front walk way and bike paths to the center’s effort to engage the surrounding community.  A marine engineer also described work required to ensure the pavilion is able to withstand flooding and ice floes.

Rutter emphasized the arts center’s need for additional and smaller performance spaces, and said the project attempts to provide them while also breaking down the barriers that isolate the building from the rest of the city. “We can be more than a destination for performances and events and become a place for pleasure and learning,” she said.  “It will give us a level of interaction we don’t have now.”

No action was taken at the meeting. The Kennedy Center is expected to seek preliminary approval at the next meeting on March 5. The NCPC and the Commission of Fine Arts are the government agencies that must approve projects before construction can begin.

Meanwhile, Kennedy Center officials are preparing audiences for the disruptions that the work will create. Beginning in mid-March, the southern entrance from northbound Rock Creek Parkway will be closed. Three northern entrances – off Rock Creek, F Street and New Hampshire Avenue — will remain open, as will the A Level entrance off 25th Street. To encourage audiences to arrive earlier and limit pre-performance congestion, the center is offering parking and meal discounts starting March 23. Patrons who arrive for an evening performance between 4 and 6 p.m. will pay $15 to park, a savings of $8, and a 10 percent coupon for purchases that day in the KC Café and Roof Terrace Restaurant.