- Percolation trench
A percolation trench, also called an infiltration trench, is a type of best management practice (BMP) that is used to manage
stormwater runoff, preventflood ing and downstreamerosion , and improvewater quality in an adjacentriver ,stream ,lake orbay . It is a shallow excavated trench filled withgravel or crushed stone that is designed to infiltrate stormwater though permeable soils into thegroundwater aquifer . [Metropolitan Council. St. Paul, MN. "Minnesota Urban Small Sites Best Management Practice Manual." [http://www.metrocouncil.org/environment/Watershed/bmp/CH3_STInfilTrenches.pdf "Infiltration Trenches."] July 2001.]A percolation trench is similar to a
dry well , which is typically an excavated hole filled with gravel. [Metropolitan Area Planning Council. Boston, MA. "Massachusetts Low Impact Development Toolkit." [http://www.mapc.org/regional_planning/LID/PDFs/trenchesdrywells.pdf "Infiltration Trenches and Dry Wells."] 2005.] Another similar drainage structure is aFrench drain , which directs water away from abuilding foundation , but is usually not designed to protect water quality.Application and Design
Percolation trenches are often used to treat runoff from
impervious surface s, such assidewalk s andparking lot s, on sites where there is limited space available for managing stormwater. They are effective at treating stormwater only if the soil has sufficientporosity . To function properly, a trench must be designed with a pretreatment structure such as a grass channel or swale, in order to capturesediment and avoid clogging the trench. [Atlanta Regional Commission. Atlanta, GA. “Georgia Stormwater Manual: Volume 2.” [http://www.georgiastormwater.com/vol2/3-2-5.pdf Section 3.2.5: "Infiltration Trench."] 2001.] It may not be appropriate for sites where there is a possibility of groundwater contamination, or where there is soil with a highclay content that could clog the trench. [ [http://wef.org Water Environment Federation,] Alexandria, VA; and [http://www.asce.org American Society of Civil Engineers,] Reston, VA. [http://books.google.com/books?id=AdU-VXXV_H0C "Urban Runoff Quality Management."] WEF Manual of Practice No. 23; ASCE Manual and Report on Engineering Practice No. 87. 1998. ISBN 1-57278-039-8. Chapter 5.]ee also
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Best management practice for water pollution
*Infiltration basin
*Sustainable urban drainage systems References
External links
* [http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=browse&Rbutton=detail&bmp=70 U.S. EPA Fact Sheet: "Infiltration Trench"]
* [http://bmpdatabase.org International Stormwater BMP Database] – Performance Data on Urban Stormwater Best Management Practices
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