September 20, 2017

Morvarid Ganjalizadeh
Infrastructure Project Management Division
District Department of Transportation
55 M Street SE, Suite 400
Washington, DC 20003

Re: LeDroit Park Phase II Green Infrastructure Design

Dear Morvarid Gonjalizadeh,

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 LeDroit Park neighborhood in Northwest Washington, D.C.

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 new trees throughout the proposed design, filling all proposed bioretention areas. These installations will grow the tree canopy of LeDroit Park, benefitting residents and visitors.

In order to further reduce the volume of stormwater runoff and pollution flowing into the Anacostia and Potomac Rivers, we suggest incorporating the following recommendations into this phase two design:

Improve Soil Space for Trees

Install soil cells or structural soils under sidewalks adjacent to bioretention areas. 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. All of the canopy trees selected for this project are suitable for bioretention areas and will offer shade and extend habitat in addition to managing stormwater. Casey Trees’ Urban Tree Selection Guide may be consulted for additional species appropriate for these conditions.

Thank you for the opportunity to comment. Casey Trees would be happy to work with you to provide tree-related analyses for the LeDroit Park Green Infrastructure Project. If you have any questions about these recommendations, please feel free to contact me at ktaddei@caseytrees.org.

Sincerely,
Kristin Taddei

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