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Bioretention Cells 

Bioretention cells reduce runoff  by   promoting infiltration and  evapotranspiration and  improve water  quality  by   filtering through soil  media and  transformation by   plants. 

Bioretention Design Bioretention cells are shallow landscape depressions with

perforated storm sewer pipe below an engineered soil mix.

The landscaped ponding area allows 6 inches of water to pond

on the surface during storm events.

Native plants tolerant of moisture variation are planted within

the cell and promote pollution removal and runoff reduction.

A mulch layer minimizes soil erosion and promotes pollutant

removal.

Sandy soil mix (≥ 72% sand, ≤ 10% clay, 5-20% organic matter)

removes pollutants by filtering and microbial activity.

A mix of pea gravel and sand or geotextile fabric layer prevents

the planting soil from migrating into the larger gravel layer andin situ soil.

A perforated pipe underdrain is embedded in a 8-12 inch layer

of #57 washed stone gravel.

Pretreatment areas along the slope of the cell provide some

water quality treatment and decrease the velocity of water

entering the cell. A grassed area or stone trench will serve this

purpose.

Chagrin River Watershed Partners, Inc.

Detail Courtesy Land Design Consultants, Inc.

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Bioretention Maintenance Water plants regularly during first growing season.

Weed, prune, and replace dead or diseased plants

as necessary. Inspect pretreatment areas twice a year. If erosion

or deposition has occurred, repair damage.

Monthly, remove litter and debris and monitor for

salt damage to plants and soil.

Annually, add additional mulch to the cell.

Every 2 years, test soil pH, and check planting soil

and mulch layer for clogging.

Bioretention Benefits Lowers stormwater runoff volume

Reduces suspended solids, metals, &

nitrogen concentrations in runoff 

Allows stormwater management to occur

in existing landscaped areas

Aesthetically pleasing 

Frequently Asked Questions

Q1. For what type of land use are bioretention cells well suited?

Bioretention cells are well suited for commercial properties in parking lot

islands or other areas available for landscaping, some industrial areas,

apartments, and other residential areas.

Q2. What is the difference between a rain garden and a bioretention cell?

Bioretention cells usually have an underdrain; rain gardens do not. In

addition, bioretention cells typically have a much greater depth of 

engineered soil mix, resulting in a greater amount of infiltration. Because of 

their lower cost, rain gardens are used by homeowners more frequently

than bioretention cells.

Q3. Can bioretention cells be incorporated into redevelopment projects?

 Yes! Former parking areas, landscaped areas, and parking lot islands can

be converted to bioretention cells.

Q4. I’d like to put a bioretention cell on my property. Who should I contact?

Landscape architects and engineers help their clients design bioretention

cells and can recommend installers. Instructions for rain garden design and

construction are available from:

Chagrin River Watershed Partners, Inc. Bioretention Cells 

Chagrin River Watershed Partners, Inc.P.O. Box 229 Willoughby, Ohio 44096-0229Phone: 440.975.3870 www.crwp.org