Treatment MeasuresInfiltration Trenches : Overview

More Information

Comprehensive guidelines for the design of infiltration measures can be found in Chapter 11 "Infiltration Measures" in the WSUD Engineering Procedures available for purchase from CSIRO publishing.

An infiltration trench is a shallow, excavated trench filled with gravel or rock, through which run-off drains. Stormwater transfers from the trench into the surrounding soil, while sediment and some dissolved pollutants are retained in the trench.

The trench is lined with a layer of geotextile fabric, to prevent soil migration into the rock or gravel fill. The top surface of the fill is also covered with a layer of fibre fabric, then finished with a shallow layer of topsoil.

Lynbrook Estate: Infiltration trench filled with appropriate sized gravel.
(Photo Courtesy of Melbourne Water)

Local soil geochemistry and grading determine the infiltration trench's ability to remove particulate and dissolved pollutants. The trenches increase the soil moisture levels, groundwater flow rates and reduce stormwater flow velocities.

Advantages

reduces peak run-off rates and volumes, and recharges groundwater,
retains pollutants prior to discharge into the drainage or groundwater system.

Limitations

pollutants and sediment may clog the gravel and infiltration surface,
groundwater contamination and low dissolved pollutant removal may occur in coarse soils,
cannot be located on steep slopes, loose or unstable areas.

References and Further Information

Schueler T.R., 1987, Controlling Urban Runoff-A Practical Manual for Planning and Designing Urban BMPs.
Schueler T.R., Kumble P.A. & Heraty M.A., 1992, A Current Assessment of Urban Best Management Practices: Techniques for Reducing Non-Point Source Pollution in the Coastal Zone.
Ontario Ministry of Environment and Energy, 1994, Stormwater Management Practices Planning and Design Manual.
Whelans, Halpern Glick Maunsell, Thompson Palmer and Murdoch University, 1994, Planning and Management Guidelines for Water Sensitive Urban (Residential) Design.
Auckland Residential Council, 1992, Design Guideline Manual: Stormwater Treatment Devices.
Galli J., 1992, Current Assessment of Urban Best Management Practices, Analysis of Urban BMP Longevity in Prince George County.
Maryland Department of the Environment, 1984, Standards and Specifications for Infiltration Practices.
Construction Industry Research and Industry Information Association (CIRIA), 1992, Report 123 Scope for control of urban runoff, Volume 1, CIRIA Report 124 Scope for control of urban runoff, Volumes 2, 3, and 4.