DESIGN OF LID SYSTEMS - Low Impact Development and Sustainable Stormwater Management - page 142

Figure 7-13 Rooftop connection to storage and infiltration bed.
Water Quality Mitigation
Pervious pavement systems are effective in reducing such pollutants as total sus-
pended solids (TSS), metals, and oil and grease (see Table 7-2). Both the pervious
pavement surface and the underlying soils below the infiltration bed allow pol-
lutant filtration. When pervious pavement systems are designed to capture and
infiltrate runoff volumes from small storm events, or what is often referred to
as the water quality volume , they provide very high pollutant reductions because
there is little if any discharge of runoff carrying the highest pollutant loads.
Because pervious pavement systems require pretreatment of TSS when adjacent
areas are allowed to drain to them, reduction of TSS and other particulates is
typically high. Pervious pavement systems will also provide limited treatment
of dissolved pollutants such as nitrates. Typical ranges of pollutant reduction
efficiencies for pervious pavements based on available literature and sampling
data are as follows: TSS, 65 to 100%; TP, 80 to 90%; TN, 30 to 65%; and NO 3 ,
30%. Pretreatment is recommended for TSS if contiguous areas drain to pervious
pavement. For information on calculating pollutant removal benefits provided by
pervious pavements, see Chapter 6.
7.4 BIOREMEDIATION
The use of vegetation in stormwater management systems evolved from vegetated
detention basins (originally described as bioretention [12], where a portion of
the runoff was retained to support vegetative growth, usually wetland species,
in a relatively impervious basin. While detention and retention structures are
no longer considered an adequate stormwater management method, the use of
vegetation has proved very effective, and partially replicates the natural system