The Kemper Development Company has started the permitting process for an underground tunnel that will connect Lincoln Square to its counterpart tower under construction on Bellevue Way.

The tunnel will run from the fifth level of the Lincoln Square garage to the fourth parking level of Lincoln Square 2, providing two-way vehicle and pedestrian access below Northeast Sixth Street. Excavation work on the expansion tower started in June, and Lincoln Square 2 will include 700,000 square feet of office space and 177,000 square feet for retail, dining and entertainment.

The northwest portion of the excavation is complicated by the adjacent Bellevue Arts Museum, which will need to be underpinned with a shoring system to stabilize its foundation, according documents in the city’s Weekly Permit Bulletin.

KDC will also require permission from the city to use its right of way property to construct the Sixth Street tunnel.