College Town Drive Rain Gardens
The College Town Drive rain gardens are designed to be an extremely low-cost LID BMP to replace grass between a bike path and the street.
Curbside Rain Gardens
Four rain gardens were installed in the grass strip to capture and infiltrate street runoff. The gardens were built by simply excavating a small area of existing lawn and underlying soils to below the street grade, and replacing them with a soil/compost mix (see diagram below). This mix is more permeable than the lawn it replaced. Two cuts were made in the existing curbs along the road to allow runoff to enter the garden. If the runoff flow is larger than the garden's infiltration capacity, the garden fills up, causing water in the street to bypass the curb cuts and flow to the existing drain inlet downstream. Because it does not require any pipes, channeling, or drains, this was an inexpensive BMP. Actual costs at any particular site depend on local conditions, especially working with underground facilities.
Unlined Rain Garden
Gutter Cutouts
Gutter Cutouts allow water that would normally have either been trapped on the road or funneled into the drainage system to instead run off of the road, and flow into the rain gardens that line College Town Drive.
Infiltration Issues
Soil types and their infiltration capabilities can change over a short distance. Soil borings from previous campus projects indicated fairly good infiltrating soils throughout campus in general, with occasional areas of more poorly infiltrating soils. Site-specific soil investigations were not conducted for this project, and, subsequently, one of the College Town Drive rain gardens infiltrates slower than the other three. Although an added cost, a geotechnical investigation that identifies site-specific infiltration rates may be warranted rather than risk building an LID BMP that may not work as well as intended.
Imperfections in Existing Grades
Elevation changes in urban areas may be subtle and unexpected. In the photo below, the corner of one of the College Town Drive rain gardens is visible at the lower left. This garden was intended to treat runoff from the adjacent street, bike path, and landscaping. See the large, muddy puddle in the center of the bike path? The settling of the bike path and erosion of the eucalyptus landscaping to the right have caused undulations in the surface grade that prevent the continual flow of runoff to the garden.
These are the plants at this BMP Site:
Featured Plant
Feather Reed Grass (Calamagrostis x Acutiflora 'Karl Floerster')
Calamagrostis x Acutiflora 'Karl Floerster': Image by:Botaurus (Creative Commons Attribution-Share Alike 2.0 Generic)
Blue Eyed Grass (Sisyrinchium Bellum)
Deer Grass (Muhlenbergia Rigens)
Douglas Iris (Iris Douglasiana)
Lomandra (Lomandra Longfolia 'Breeze')
Want more details? https://www.owp.csus.edu/csus-lid/
Curbside Rain Gardens
Four rain gardens were installed in the grass strip to capture and infiltrate street runoff. The gardens were built by simply excavating a small area of existing lawn and underlying soils to below the street grade, and replacing them with a soil/compost mix (see diagram below). This mix is more permeable than the lawn it replaced. Two cuts were made in the existing curbs along the road to allow runoff to enter the garden. If the runoff flow is larger than the garden's infiltration capacity, the garden fills up, causing water in the street to bypass the curb cuts and flow to the existing drain inlet downstream. Because it does not require any pipes, channeling, or drains, this was an inexpensive BMP. Actual costs at any particular site depend on local conditions, especially working with underground facilities.
Unlined Rain Garden
Gutter Cutouts
Gutter Cutouts allow water that would normally have either been trapped on the road or funneled into the drainage system to instead run off of the road, and flow into the rain gardens that line College Town Drive.
Infiltration Issues
Soil types and their infiltration capabilities can change over a short distance. Soil borings from previous campus projects indicated fairly good infiltrating soils throughout campus in general, with occasional areas of more poorly infiltrating soils. Site-specific soil investigations were not conducted for this project, and, subsequently, one of the College Town Drive rain gardens infiltrates slower than the other three. Although an added cost, a geotechnical investigation that identifies site-specific infiltration rates may be warranted rather than risk building an LID BMP that may not work as well as intended.
Imperfections in Existing Grades
Elevation changes in urban areas may be subtle and unexpected. In the photo below, the corner of one of the College Town Drive rain gardens is visible at the lower left. This garden was intended to treat runoff from the adjacent street, bike path, and landscaping. See the large, muddy puddle in the center of the bike path? The settling of the bike path and erosion of the eucalyptus landscaping to the right have caused undulations in the surface grade that prevent the continual flow of runoff to the garden.
These are the plants at this BMP Site:
Featured Plant
Feather Reed Grass (Calamagrostis x Acutiflora 'Karl Floerster')
Calamagrostis x Acutiflora 'Karl Floerster': Image by:Botaurus (Creative Commons Attribution-Share Alike 2.0 Generic)
Blue Eyed Grass (Sisyrinchium Bellum)
Deer Grass (Muhlenbergia Rigens)
Douglas Iris (Iris Douglasiana)
Lomandra (Lomandra Longfolia 'Breeze')
Want more details? https://www.owp.csus.edu/csus-lid/