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Adry well orsoak is a structure formed underground that disposes of unwantedwater, such assurface runoff water andstormwater.[1] In this process, the water isinfiltrated into the ground, further merging with groundwater in the local area.[1] The way water flows in a dry well is throughgravity.[1] A dry well will typically have a chamber structure, or a deep pit covered with gravel.[1] Dry wells may vary from simple to more advanced structures.
Whendesigning a dry well, there are requirements. Dry wells require optimal conditions prior to installing; they may not be installed wheretopographic conditions andsoil are not at ideal standards.[2] Dry wells should typically be anywhere from 30–100 feet deep, with a width of 3–6 feet at the surface.[3] For safety cautions, the dry wells must be placed at a distance away from property lines, basements, and any foundations.[2] Any plants or other structures should not be placed on top of a dry well in case of maintenance.[2] Furthermore, when wanting to install a dry well it is highly recommended toconsult with aprofessional.
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][7]
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.[8][9]
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 stormdrains are usually buried below the same parking lot.[1]
Dry wells are followed by their own pros and cons when considering installing one. These pros and cons are included below;
Pros: low cost, small footprint,construction is rapid.[3]
Cons: difficult to maintain when clogged, cannot be pumped to extractgroundwater, is dependent on permeable soil that allows infiltration ofstormwater.[3]
A sump in abasement can be built in dry well form, allowing thesump pump to cycle less frequently (handling only occasional peak demand). A discharge line may also be placed to help discharge water that is propelled by the sump pump, driving out of the basement and further away from the foundation.[10] AFrench drain can resemble a horizontal dry well that is not covered.[11] 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.[10]
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.[12]
