The architecture firm that designed DC Water's new Capitol Riverfront headquarters is suing the project's lead contractor over unpaid bills.

SmithGroup filed a lawsuit Friday against Skanska USA Building Inc., seeking more than $921K it says the company owes it for extra work on the Southeast D.C. riverfront project.

The lawsuit, filed in U.S. District Court for the District of Maryland, claims the DC Water headquarters project was delayed by more than two years from its initial projected delivery date of June 30, 2017, until the project was ultimately completed Feb. 29, 2020.

Skanska, which provided design-build services for the DC Water headquarters project, directed SmithGroup, the project's architect, to perform a series of additional services during the project's extended timeline, according to the lawsuit. The suit says the parties had agreed to extend the delivery date to September 2018, but it blames Skanska for the additional 17 months of delays.

SmithGroup claims Skanska has not paid it for $921,138 in additional services it performed. The lawsuit asks the court to compel Skanska to pay it the $921K, plus interest, fees and other costs.

Skanska declined to comment.

The DC Water headquarters building sits on the west bank of the Anacostia River at 1385 Canal St. SE, one block from Nationals Park. The five-story, 167K SF office building was projected to cost $55M when it was proposed in 2015.

The building's curved, glass facade stands out along the waterfront, and the project's design incorporated a host of environmentally friendly features. It has a green roof with plantings that reduce stormwater runoff and a wastewater thermal recovery system that captures heat from flowing wastewater.