February 17, 2017
Infrastructure Project Management Administration
District Department of Transportation
55 M Street SE, Suite 400
Washington, DC 20003
Re: Alger Park Green Infrastructure Design
Dear Julie Pike,
Casey Trees is a Washington, D.C.-based nonprofit, with a mission “to restore, enhance, and protect the tree canopy of the nation’s capital.” To fulfill this mission, we plant trees; monitor the city’s tree canopy; and work with government officials, developers, and residents to prioritize the District’s trees and to encourage tree planting on both public and private property. We are dedicated to helping the District reach its 40 percent tree canopy goal by 2032 – an achievable goal only if the District actively grows the city’s urban forest. Therefore, we are excited to provide comments on the green infrastructure design for the Hillcrest neighborhood adjacent to Alger Park in Southeast Washington, DC.
This project aims to retain stormwater through green infrastructure, including bioretention installations with tree plantings. Trees in bioretention areas slow stormwater runoff and reduce pollution through interception, evapotranspiration, and nutrient removal. We are pleased to see 27 new trees in the design, filling nearly all proposed bioretention areas. These trees will provide additional tree canopy and transitional habitat between the Alger Park and the Hillcrest neighborhood.
In order to further reduce the volume of stormwater runoff and pollution flowing into the Anacostia River, we suggest incorporating the following recommendations into the design.
Improve Soil Space for Trees
Consider installing soil cells or structural soils under sidewalks. These systems facilitate tree root growth and provide adequate soil volume for roots, allowing larger trees to thrive and soil to remain un-compacted. Reference section 47.7.4 of the DDOT Green Infrastructure Standards and pages 26-27 of Casey Trees’ Citizen Advocate Handbook for more information.
Maximize Tree Canopy
Maximize tree canopy in all bioretention areas to absorb excess stormwater. We suggest selecting medium or large trees for this project and covering streetside bioretention areas with tree canopy wherever possible. If opting for a small tree due to soil volume constraints, plant Downy Serviceberry (Amelenchier arborea), as it tends to perform better than Apple Serviceberry (Amelenchier x grandiflora) in moist soil conditions (See Table 1). See Table 2 for alternative medium and large tree species that are suitable for streetside bioretention.
Thank you for the opportunity to comment. Casey Trees would be happy to work with you to provide tree related analyses for the Alger Park Green Infrastructure Project. If you have any questions about these recommendations, please feel free to contact me at firstname.lastname@example.org.