Trump's proposed arch has 'adverse effects,' administration acknowledges

The Trump administration acknowledges that the proposed construction of a 250-foot triumphal arch along the Potomac River at the foot of Arlington National Cemetery will cause "adverse effects" on the setting and views along the river -- but it says those impacts "cannot be fully avoided" because the arch's location is "central to the undertaking."

The acknowledgment is contained in a document that has been sent by the National Park Service to four historic preservation and planning agencies in the Washington area, seeking their agreement with park service's plans to mitigate the adverse effects.

Those efforts include monitoring construction vibration and controlling noise, an archeological study and various planned "improvements" to the parkland, including new walkways, curbs, lighting and plantings, according to the document.

Earlier this month, attorneys for a group of Vietnam War veterans who have sued to block construction of the arch, asked a federal judge to issue a temporary restraining order to prevent the administration from moving forward with excavation work on the project. The veterans suing over the arch have argued it would obstruct views of Arlington National Cemetery and can't be built without congressional authorization.

Federal rules call for agreements like this to be reached with a state's historic preservation office or a tribal nation when there's the potential for a project to "diminish the integrity" of a historic property. Memorial Circle, the planned site for the arch and a roundabout near the entrance Arlington National Cemetery, is a historic property listed on the National Register of Historic Places.

While the law requires consultation and an effort to minimize potential harms -- "to the maximum extent possible" -- agreement with state officials does not appear to be a requirement for a federal project at a historic site to continue.

The document circulated by NPS to historic preservation officials in Virginia and D.C. says that Memorial Circle "is located within a highly sensitive historic and commemorative landscape," and that the arch at that space would affect the "setting, design, feeling, association, spatial organization, circulation, and contributing views and vistas" of the location.

Renderings of the arch show a 250-foot structure -- more than twice as tall as the nearby 99-foot Lincoln Memorial -- with an inscription reading "One Nation Under God" and at its top, a gold statue of Lady Liberty with outstretched gold wings. Four golden lions sit at each corner of the arch's base, renderings showed.

The administration said in the document that the location is "central to the undertaking" and the arch can't be placed elsewhere because "relocation outside Memorial Circle would constitute a materially different undertaking."

Word of the agreement was first reported by The Washington Post.

Trump has said called the arch a "wonderful addition to the Washington D.C. area," saying in a social media post earlier this year that it will be the "GREATEST and MOST BEAUTIFUL" of structures "anywhere in the world."

The arch received initial approval in July from the National Capital Planning Commission, a federal agency led by Trump's hand-picked appointees, despite hours of public testimony against the project.

The arch still needs final approval from the National Capital Planning Commission. Several Democratic lawmakers say that the arch violates the Commemorative Works Act, which requires congressional approval for memorials on federal land in or near D.C.

An Interior Department spokesperson said it will "follow all laws and regulations" around the arch construction.

"Throughout the consultation process, Interior has received over 100,000 public comments, has accepted dozens of organizations as consulting parties, and has extended comment periods to allow for more robust discussion," the spokesperson said in a statement to ABC News.