Environmental Engineering Reference
In-Depth Information
3.1.3 Pervious (porous) pavements
In contrast to ordinary impervious pavements of roads, streets and parking slots, the
pervious ones have incorporated porous modules, which allow for the infiltration of
runoff into the road (street) sub base and after that to the ground. With these pavements,
the volume of runoff is reduced drastically and directed to recharge ground aquifers.
However, they have the disadvantages of reduced load bearing and more difficult
maintenance, as the infiltration modules (sections) require a regular cleaning and
sweeping in order to avoid clogging. The application of pervious payment is most
recommendable for areas with permeable soils. If the street (road) base is impermeable,
their application would require the addition of a sub drain system for the collection and
discharge of the percolated runoff, which might increase the cost considerably. In
general, the most appropriate applications of porous pavements are in the cases of
parking slots and small streets (roads), with relatively low traffic load, where regular
cleaning would be feasible, and the soil conditions allow for runoff infiltration. It should
be noted that the infiltration rate of porous pavements is much higher than the soil
infiltration rate, which allows for the accumulation of the infiltrated water in the sub-base
and its gradual infiltration through the soil.
3.2 Control during runoff transport
3.2.1 Filter strips and environmental corridors
These are especially designated and vegetated areas, which have the purpose to retard and
partially absorb the runoff from developed areas, to enhance infiltration and to retain
suspended particles, which could be the carriers of pollutants. We could differentiate
between:
• Filter strips - these are vegetated corridors of land parallel to road structures, which
have the purpose of partial filtration and infiltration of runoff from upstream areas.
Usually, they are covered by grass, which has the purpose of slowing down the runoff
velocity, allowing for the increased rate of infiltration and sedimentation of suspended
particles, thus preventing erosion and assimilating potential pollution constituents,
associated with particulate material and nutrients. An illustration of a filter strip along
a road junction is shown in Figure 2.2. Filter strips at a larger scale could serve as a
buffer between different types of land uses, be landscaped to become aesthetically
pleasant and provide groundwater recharge in areas with permeable soils.
• Environmental buffer zones are open vegetated areas or parks along natural water
bodies, which have the purpose to retain runoff pollution before it is discharged into
the water body. Often, they incorporate some of the treatment methods described in
section 3.3, such as retention basins, ponds or wetlands.
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