The use of infiltration facilities represents an attractive opportunity to contribute to the recharge of groundwater and thus to minimise the interference of the natural water cycle. Stormwater infiltration returns surface flows to the subsurface and, thus, never aggravates flooding downstream. Additionally, a significant portion of the pollutant load of stormwater, which is normally directed to the receiving water, can be removed. If the soil through which water infiltrates contains any degree of clay or humus, the soil is a powerful filter that protects aquifers from contamination.

Some advantages of local rainwater infiltration are:

• recharge of groundwater

• preservation and/or enhancement of natural vegetation

• reduction of pollution transported to the receiving waters

• reduction of downstream flow peaks

• reduction of basement flooding in combined sewer systems

• reduction in the settlement of the surface in areas of groundwater depletion

• smaller storm sewers at a lesser cost

In some cases rainwater infiltration may have following negative impacts (Urbonas & Stahre, 1993):

• soils seal with time

• some infiltration facilities may not receive proper maintenance

• reliance on their operation may leave communities facing enormous capital costs in

the future, if these systems begin to fail

• groundwater level may rise and cause basement flooding or damage to building

foundations