25 October 2004
required.23 Other potential tasks include replacement of dead vegetation, soil pH
regulation, erosion repair at inflow points, mulch replenishment, unclogging the
underdrain, and repairing overflow structures. Depending on pollutant loads, soils may
need to be replaced within 5-10 years of construction.24
DRY WELLS. A dry well typically consists of a pit filled with aggregate such
as gravel or stone and is located to catch water from roof downspouts or paved areas.
Figure 8-3. Dry Well Schematic
Source: Stormwater Management for Maine, 1995.
Most Appropriate Uses. Dry wells are suitable for treating small impervious
areas (as an alternative to infiltration trenches) and may be useful on steeper slopes
where trenches or other facilities cannot be installed. Dry wells are particularly suited to
treat runoff from residential driveways or rooftop downspouts. It is important to avoid
installation in large areas with high sediment loads and in soils with limited permeability.
Dry wells are not appropriate for treating runoff from large impervious surfaces such as
Cost Data. Costs for dry wells are site specific. Cost is determined by the
cost of excavation and the price of gravel. This will depend on the well volume and the
source of the gravel.
Maintenance Issues. Dry wells are typically employed in single-family
homes; maintenance is usually the responsibility of the homeowner. Maintenance is
minimal and includes clearing the rain gutters of debris that clogs the downspout.
Corrective Actions. Dry wells can clog over time if there is extensive
loading of fine grained sediment. Clogging is evident if there is standing water after a
rain event at the surface of the facility. The appropriate corrective action is to first dig
LID Center, 2000.