UFC 3-210-10
25 October 2004
Figure 4-5. Mechanism of Groundwater Recharge
4-5.1
LID Infiltration Concepts. Maintaining natural infiltration rates is an
important aspect of LID design. Accomplishing this requires an accurate understanding
of the existing soils and groundcover conditions. For example, a clay soil on a pre-
development site may have very little infiltration capacity or a sandy soil, which is
compacted, may have reduced capacity. The design should take care not to overload
the hydraulic conductivity of existing soils.
Soil maps by themselves are not sufficient to determine the capacity of the
soils to absorb and filter water; additional field testing is required. Dispersing flows,
maintaining natural flow patterns, and directing flows towards soils with high capacities
for infiltration will help maintain ground water levels. Amending soils by adding organic
materials, reducing compaction by aeration, maintaining leaf or "duff" layers in natural
areas, and reducing compaction requirements for non-load bearing areas will also
enhance and maintain infiltration rates and patterns.
Although soils and natural areas have a high capacity to filter and treat
pollutants, careful planning must take place to ensure that potential pollutants such as
nitrates, oils, or other urban runoff contaminants are adequately treated before entering
any potential water supply. Infiltration areas should not be located near areas that have
potential for hazardous waste spills or contamination. It is important to ensure that
runoff is adequately filtered before it is allowed to infiltrate, especially if local aquifers
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