Attenuation

GJ AttenuationRestricting the rate of drainage

There is an increasing need to control and restrict the rate of drainage (attenuate) flow from sports pitches.

There could be one of three reasons:

  • there is no acceptable outfall within the confined surroundings of the pitch
  • there is a statuary regulation to restrict the flow rate from the site
  • there is a need to protect adjacent property.

Drainage water can be temporarily stored in swales, stone trenches, ponds or manufactured plastic cells.  Secondary drains in the form of narrow spaced slit drains attenuate rainfall to a degree but the quantity of water temporarily held does not amount to much more than 4mm of rainfall.  With careful planning attenuation procedures can account for 1 in 10 year storm rate intensity.  Outflow off-site from temporary storage can be controlled by further means or with the installation of a ‘hydro-brake’ system incorporated in a re-enforced concrete chamber.

There is now the environmental concern to retain storm water on site where possible.  This assists in re-charging underground water flow and prevents the loss of a valuable resource that is becoming increasingly in short supply.

Examples

Hertfordshire County Council

Given a restricted drainage outfall rate, a feasibility study was prepared for the construction of a sports facility to incorporate attenuation. An intensive installation was designed to temporary store water without utilising undue space. After preparation of tender documents the contract was supervised to completion.

 

Elm Lane Sportsgrounds, Lewisham

A 70m storage trench was installed in order to temporary store surface and underground drainage water from renovated a sportsground within a residential area and without any approved natural water-course outfall.

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Refer to the following articles…

Restricting drainage outfall from sports pitches

(International Turfgrass Research Conference, July 2005)

Flooding may not mean more drains

(Golf Course News International, Feb/Mar 2005)

Read more articles about attenuation…

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