If the depression holds water for more than four hours, dig 10 to 15 inches deeper and provide an underdrain of gravel.

These wells are intended to control the leachate mound after there has been a failure of the underdrain system.

The underdrain system is generally designed to flow one-third to one-half full to permit ventilation of the bed.

The treated wastewater is collected by an underdrain system prior to clarification in the final settling tank.

Type D soils will require an underdrain paired with the sandy soil mix in order to drain properly.

The filtered water is collected by perforated underdrain pipes in a similar manner as in bioretention systems.

• the underdrain system which supports the media, collects the effluent and ventilates the filter providing oxygen for biological growth.

These types of underdrain pipes were able to draw vacuum without collapsing, which enabled them to attach to a pump to dewater a construction site.

When an area's soils are not permeable enough to allow water to drain and filter properly, the soil should be replaced and an underdrain installed.

A porous pavement LID has storage, underdrain and pavement compartments.

Pumping wells in the waste have also been proposed to reduce the height in old landfills that are not engineered with a leachate underdrain system.

The findings from a rare opportunity to exhume, examine, and sample a granular underdrain leachate collection system at a large municipal landfill site are reported.

Pumping (extraction, purge) wells in the waste may be proposed as part of the design of new landfills to backup the leachate underdrain system.

A rain barrel has only storage and underdrain compartments and a vegatative swale LID has a single surface compartment.

Michels Materials has highway construction operations varying from specialized underdrain systems and shouldering to complete construction of roadways, including base course placement and grading.

When the fill is completed, this underdrain will form a continuous water runoff system from the upper end of the valley to the lower end of the fill.

Liquid accumulating in the underdrain ducting may be returned to the sewage treatment plant; and composting pads may be roofed to provide better moisture content control.

The design process should consider the provision of detention storage to yield a high hydrologic effectiveness, and discharge control by proper sizing of the perforated underdrain and overflow path.

The infiltration capacity of the native soil is a key design consideration for determining the depth of base rock for stormwater storage or for whether an underdrain system is needed.

For instance, in the proposed green streets, the cost of dry swales with underdrain and reinforced grass shoulders should be balanced with savings by not requiring curb, gutter or catch basins.

Filtration applications are highway underdrain systems, retaining wall drainage, landfill leachate collection systems, as silt fences and curtains, and as flexible forms for bags, tubes and containers.

The concept of developing "triggers" to initiate leachate control measures, and the associated potential impact on groundwater, is discussed in the context of the potential design life of the underdrain system in a landfill.