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Adry well ordrywell is an underground structure that disposes of unwantedwater, most commonlysurface runoff andstormwater, in some casesgreywater or water used in agroundwater heat pump. It is agravity-fed, vertical underground system that cancapturesurface water fromimpervious surfaces, then store and graduallyinfiltrate the water into thegroundwater aquifer.
Such a structure is also called adead well,absorbing well, ornegative well, and in the United Kingdom asoakaway orsoakage pit,[1] and in Australia asoakwell orsoak pit.[2][3]
Dry wells are excavated pits that may be filled withaggregate or air and are often lined with a perforated casing. The casings consist of perforated chambers made out ofplastic orconcrete and may be lined withgeotextile.[4] They provide high stormwater infiltration capacity while also having a relatively small footprint.[5]
A dry well receives water from entry pipes at its top. It can be used as part of astormwater drainage network, an agriculturalwell drainage system or on smaller scales such as collecting stormwater from buildingroofs. It is used in conjunction with pretreatment measures such asbioswales or sediment chambers to preventgroundwater contamination.[6][2]
The depth of the dry well allows the water to penetrate soil layers with poor infiltration such asclays into morepermeable layers of thevadose zone such assand.[7][8]
Simple dry wells consist of a pit filled withgravel,riprap,rubble, or otherdebris. Such pits resist collapse but do not have much storage capacity because their interior volume is mostly filled by stone. A more advanced dry well defines a large interior storage volume by a concrete or plastic chamber with perforated sides and bottom. These dry wells are usually buried completely so that they do not take up any land area. The dry wells for a parking lot's storm drains are usually buried below the same parking lot.[citation needed]
Asump in abasement can be built in dry well form, allowing thesump pump to cycle less frequently (handling only occasional peak demand). AFrench drain can resemble a horizontal dry well that is not covered. A larger open pit or artificialswale that receives stormwater and dissipates it into the ground is called aninfiltration basin or recharge basin. In places where the amount of water to be dispersed is not as large, arain garden can be used instead.
A covered pit that disposes of the water component of sewage by the same principle as a dry well is called acesspool. Aseptic drain field operates on the same slow-drain/large-area principle as an infiltration basin.
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