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Filter Drain
FILTER DRAINS
Construction Cost
L and Take
PRIMARY CONSIDERATIONS
Maintenance Requirements
LOW
HIGH
LOW
BENEFITS
�Water
Quality Control YES
�Water
Quantity Control YES
�Amenity
Value NO
�Habitat
Creation Value NO
�Biological
Treatment NO
DESCRIPTION
DESIGN
filter drain is a gravel filled �Filter
drains are normally situated on �Design
to avoid flooding for 1:30 year
trench, generally with a the roadside verge or median strip. The storm event. For 100 year events,
Aperforated pipe at the base. Run- perforated pipe is not required along the property flooding should not take place
off flows slowly through the granular entire length of the trench, only near the and overland flows should not pass from
material, trapping sediments and end of the device.
the site to cause flooding to other areas.
providing attenuation. Flow is then �The
trench is usually lined with �Filter
drains should not be located on
directed to a perforated pipe, which geotextile to prevent ingress of soil and common boundaries as construction of
conveys run-off either back into the other material into the structure fences and hedges will destroy them.
sewerage network or into a waterbody. (CIRIA,2000).
�The
minimum distance from a property
Filter drains are mainly used to drain �Inspection
manholes should be located should be at least three times the depth
road and carpark surfaces. Ideally these at regular intervals along the length of of the trench.
systems are used as a component of a the device.
�Consideration
of topography is
treatment train.
�Excess
flows during extreme rainfall important to ensure sub-surface and
events may be dealt with by overland overland flows are directed away from
flooding passing to swales or by an properties.
overflow pipe which connects to swales �When
filter drains are used to drain
or other parts of the drainage system. road surfaces, there is a possibility of the
�The
dimensions of the trench should be stones being scattered when vehicles
selected to meet the level of reduction leave the carriageway. This can be
and attenuation of flows required, the minimised by using crushed rock on the
assessment of hydraulic design surface layer of the fill material (CIRIA,
performance being site specific. 2000).
�Should
only be used to drain areas less �Filter
drains can be used in the base of
than 5 hectares.
swales to provide additional attenuation
�Ideally
a pre-treatment device (such as and treatment.
a filter strip or grassed area) should be �When
using filter drains, the use of
incorporated to increase the longevity of gullypots is not required and should be
the system.
avoided.
�Construct
at least 1.5m above the �Do
not construct near drinking water
maximum groundwater level and only wells, septic tanks or drain fields, unless
where the groundwater classification fully lined.
allows.
Road Sub-Base
Road Base
Capping Layer
(where required)
Road Edge
CROSS-SECTION THROUGH A FILTER DRAIN
For inspection purposes only.
Consent of copyright owner required for any other use.
Filter Material
Filter Material
Filter Drain
S OURCE
CONTROL
Geo-textile Liner
Road Verge
Porous and Perforated Pipe
MORE OVERLEAF - 1 of 2
GREATER DUBLIN STRATEGIC DRAINAGE STUDY - ENVIRONMENTAL MANAGEMENT POLICY
EPA Export 24-08-2012:23:55:52