State Route 6 Corridor Study Final Report - Cobb County Government

ioretention facility and are categorized as a Low Impact Development (LID)
stormwater best practice. Rain gardens along transportation corridors can provide the
following benefits:
• Provide a natural approach to water quality and water quantity problems
associated with development and impervious surfaces;
• Reduce rainwater runoff and the amount of storm sewer system needed to
manage stormwater;
• Control erosion and reduce pollution during and after construction; and
• Provide an aesthetic view for roadway users.
Rain gardens have been primarily been implemented in the Midwest, Northeast and
Northwest. According to Low Impact Development: A Literature Review by the
Environmental Protection Agency, implementing a rain garden can be less costly than
traditional stormwater treatments. 4
Rain garden implementation considerations include soil types, site conditions and
adjacent land uses. As a planning‐level study, this study does not have the required
data available to identify precise locations for rain gardens for the recommended
capacity projects. Applicability and appropriate use of rain gardens for recommended
projects should be developed during preliminary engineering and design.
A conceptual roadway cross‐section with a rain garden is illustrated in Figure 3‐4. As
water runs off the roadway into a rain garden, the water is absorbed by plants,
infiltrated into the ground, and is slowed before discharging into the adjacent land. In
general, native plant materials are used within rain gardens because they are hardy and
require little maintenance. In addition, the dense roots of native plants help break up
heavy soils and increase infiltration. Typical rain gardens are four to eight inches deep.
4 Environmental Protection Agency, Low Impact Development: A Literature Review (Washington, D.C., October 2000), Page
4.
Final Report 3‐15
January 2008