The National Park Service sent a memorandum of agreement to historic preservation groups that included a series of measures to lessen the impact of President Donald Trump’s planned 250-foot triumphal arch after concluding the massive structure would have unavoidable “adverse effects” on historic sites around the nation’s capital.

The proposed MOA, obtained by the Washington Post, lays out steps federal officials say could mitigate the project’s effects as the Trump administration seeks to complete a required historic preservation review and move the arch toward final approval.