Environmental Assessment of Emerald Ash Borer on Arch Grounds Completed

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Date: March 8, 2012
Contact: Ann Honious, 314-655-1614

After a period of study and public comment, the NPS has determined that the best course of action will be to remove the single species planting of Rosehill ash trees and replace it with a new uniform planting using a compatible new species. The EA proposes a strategy for addressing the threat posed by the Emerald Ash Borer, establishes the criteria and decision-making process for identifying a compatible species for replacing the Rosehill ash, and assesses the impacts of replacing the ash trees in the historic planting. The goals of the project included maintaining the integrity of the National Historic Landmark (NHL), retaining the character-defining features of the Memorial (including the single species tree planting along the allées or walkways), minimizing the impact on National Park Service operations, and maintaining and enhancing the visitor experience.

The National Park Service is proposing action at this time due to the current state of decline of the Rosehill ash trees as well as the impending arrival of the Emerald Ash Borer in the St. Louis metropolitan area. The Rosehill ash is a species that is susceptible to ash borer damage, and it is anticipated that once these insects become established in the St. Louis area the ash trees will eventually succumb to them. In addition, the existing ash trees, many over 40 years old, have reached or passed their maturity due to urban conditions, and need to be replaced whether the ash borer arrives or not. The Memorial's General Management Plan directs park managers to protect the allées, along with the NHL's other character defining landscape features. These features are part of the design plan for the grounds created by Dan Kiley, noted modernist landscape architect and close friend of Gateway Arch designer Eero Saarinen. Saarinen himself worked closely with Kiley on this plan, and the Memorial staff and preservationists within the NPS have made great efforts to try to preserve the landscape in a form as closely approximating the original plan as possible.

Under the accepted preferred alternative, the Rosehill ash trees will be removed in a phased approach,coordinated with implementation of the overall City-Arch River 2015 Design Competition. The replacement trees in the allées will be a single species of uniform height, form, and caliper, chosen for disease and insect resistance and bearing a form similar to that specified by Kiley. In many ways the mature replacement trees will look very much like the existing Rosehill ash when the process of replacement is complete. The replacement of the Rosehill Ash trees will only affect the allées of the Arch Grounds, while over 50% of the park's 1,100 trees of 36 other species will remain untouched.

The Environmental Analysis used science and scholarship, advice from subject matter experts and others who have relevant knowledge and experience, and the results of public involvement activities to arrive at the preferred alternative. In Superintendent Tom Bradley's professional judgment there would be no impairment of park resources and values from implementation of the preferred alternative. Copies of the EA and Finding of No Significant Impact are available on the park's website at www.nps.gov/jeff

Last updated: April 10, 2015

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