Dry well
Encyclopedia
A dry well is an underground structure that disposes of unwanted water
, most commonly stormwater
runoff
, by dissipating it into the ground, where it merges with the local groundwater
. Often called a soakaway in the UK.
A dry well is a passive structure. Water flows through it under the influence of gravity. A dry well receives water from one or more entry pipes or channels at its top. A dry well discharges the same water through a number of small exit openings distributed over a larger surface area, the side(s) and bottom of the dry well. When a dry well is above the water table
, most of its internal volume will contain air. Such a dry well can accept an initial inrush of water very quickly, until the air is displaced. After that, the dry well can only accept water as fast as it can dissipate water. Some dry wells deliberately incorporate a large storage capacity, so that they can accept a large amount of water very quickly and then dissipate it gradually over time, a method that is compatible with the intermittent nature of rainfall. A dry well maintains the connection between its inflow and outflow openings by resisting collapse and resisting clogging.
Simple dry wells consist of a pit filled with gravel
, riprap
, rubble
, or other debris
. 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 reinforced concrete
cylinder 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.
A French drain
can resemble a dry well that is not covered. A covered dry well that disposes of sewage is called a cesspool, while an open pit that receives storm water and dissipates it into the ground is called a recharge basin or infiltration basin
.
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, most commonly stormwater
Stormwater
Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...
runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...
, by dissipating it into the ground, where it merges with the local groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
. Often called a soakaway in the UK.
A dry well is a passive structure. Water flows through it under the influence of gravity. A dry well receives water from one or more entry pipes or channels at its top. A dry well discharges the same water through a number of small exit openings distributed over a larger surface area, the side(s) and bottom of the dry well. When a dry well is above the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
, most of its internal volume will contain air. Such a dry well can accept an initial inrush of water very quickly, until the air is displaced. After that, the dry well can only accept water as fast as it can dissipate water. Some dry wells deliberately incorporate a large storage capacity, so that they can accept a large amount of water very quickly and then dissipate it gradually over time, a method that is compatible with the intermittent nature of rainfall. A dry well maintains the connection between its inflow and outflow openings by resisting collapse and resisting clogging.
Simple dry wells consist of a pit filled with gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
, riprap
Riprap
Riprap — also known as rip rap, rubble, shot rock or rock armour or "Rip-rap" — is rock or other material used to armor shorelines, streambeds, bridge abutments, pilings and other shoreline structures against scour, water or ice erosion.It is made from a variety of rock types, commonly granite or...
, rubble
Rubble
Rubble is broken stone, of irregular size, shape and texture. This word is closely connected in derivation with "rubbish", which was formerly also applied to what we now call "rubble". Rubble naturally found in the soil is known also as brash...
, or other debris
Debris
Debris is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, in geology, large rock fragments left by a melting glacier etc. The singular form of debris is debris...
. 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 reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...
cylinder 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.
A French drain
French drain
A French drain, blind drain, rubble drain, rock drain, drain tile, perimeter drain, land drain or French ditch is a trench covered with gravel or rock that redirects surface and groundwater away from an area...
can resemble a dry well that is not covered. A covered dry well that disposes of sewage is called a cesspool, while an open pit that receives storm water and dissipates it into the ground is called a recharge basin or infiltration basin
Infiltration basin
An infiltration basin , is a type of best management practice that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...
.
See also
- Infiltration basinInfiltration basinAn infiltration basin , is a type of best management practice that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...
- Landscape architectureLandscape architectureLandscape architecture is the design of outdoor and public spaces to achieve environmental, socio-behavioral, or aesthetic outcomes. It involves the systematic investigation of existing social, ecological, and geological conditions and processes in the landscape, and the design of interventions...
- Percolation trenchPercolation trenchA percolation trench, also called an infiltration trench, is a type of best management practice that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...
- French drainFrench drainA French drain, blind drain, rubble drain, rock drain, drain tile, perimeter drain, land drain or French ditch is a trench covered with gravel or rock that redirects surface and groundwater away from an area...