Environmental Engineering Reference
In-Depth Information
New impervious surfaces such as rooftops, which produce relatively little
additional pollutants, can be left out of the water quality impact site evaluation
under most circumstances. Rainfall has some latent concentration of nitrate (1 to
2 mg/L) as the result of air pollution, but it would be unreasonable to require
removal of this pollutant load from stormwater runoff. The control of nitrate from
new development should focus on reduction of fertilizer applications rather than
removal from runoff.
When the development plan proposed for a site is measured by type of sur-
face (roof, parking lot, driveway, lawn, etc.), an estimate of potential pollutant
load can be made based on the volume of runoff from those surfaces, with
a flow-weighted pollutant concentration applied. The total potential non-point
source load can then be estimated for the parcel, and the various LID measures,
both structural and nonstructural, can be considered for their effectiveness. This
method is described in detail in subsequent chapters. In general, the nonstruc-
tural measures are most beneficial for the reduction of solutes, with structural
LID measures most useful for particulate reduction. Because soluble pollutants,
once they are contained in runoff, are extremely difficult to remove, prevention
or reduction on the land surface, as achieved through nonstructural measures, is
the most effective approach.
Stormwater Standards for Special Areas
The control guideline may have to be modified before applying to special areas
around the country. The “special areas” designation includes existing dense urban
parcels (served by combined sewers) or highly developed sites with little or no
vacant areas, contaminated or brown field sites, and sites situated on old mining
lands. These are areas where LID application may be limited.
Legal Implications of Green Infrastructure
Although most research and development of green infrastructure has focused
on the technical aspects of various methods and materials, a recent paper by
A. P. Dunn raises several issues as to how green infrastructure can alleviate
urban poverty and promote healthy communities [13]:
Green infrastructure is an economically and environmentally viable approach for
water management and natural resource protection in urban areas. This article argues
that green infrastructure has additional and exceptional benefits for the urban poor
which are not frequently highlighted or discussed. When green infrastructure is con-
centrated in distressed neighborhoods—where it frequently is not—it can improve
urban water quality, reduce urban air pollution, improve public health, enhance
urban aesthetics and safety, generate green collar jobs, and facilitate urban food
security. To make these quality of life and health benefits available to the urban
poor, it is essential that urban leaders remove both legal and policy barriers to
implementing green infrastructure projects. This Article argues that overcoming
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