D.C. Code § 10-150
The Director of the National Park Service is authorized to grant permission to the Department of Agriculture for the temporary occupation of such area or areas of Potomac Park, not exceeding a total of 75 acres in extent, as may not be needed in any one season for the reclamation or park improvement, the said areas to be used by the Department of Agriculture as testing grounds; provided, that nothing herein contained shall be construed to change the essential character of the lands so used, which lands shall continue to be a public park, as provided in § 10-147; and provided further, that said area or areas shall be vacated by the Department of Agriculture at the close of any season upon the request of the said Director; and provided further, that the entire Park shall remain under the charge of the said Director.
D.C. Code § 10-150