The Dilemma of Water in the City - Politics of Urban Runoff: Nature, Technology, and the Sustainable City - page 13

fl ooding in urban areas by detaining water temporarily and releasing it
slowly, but these facilities also capture contaminants as stormwater vol-
umes slow down and solids drop out. Detention ponds are a common
element of cities, whether they are fenced-off concrete boxes in sprawl-
ing parking lots, artifi cial ponds behind buildings on private property,
or grassy depressions in public rights-of-way. They have become the de
facto strategy to manage the fl ooding, erosion, and water quality issues of
urban runoff in many cities because they are relatively easy to construct
and because they provide fl ood protection and a modest degree of water-
quality treatment.
However, detention ponds are only partially effective as a water treat-
ment strategy because they provide physical removal of contaminants but
do not address those contaminants that remain suspended in solution.
These suspended pollutants fl ow through detention ponds and are released
downstream, where they have biological and ecological impacts. Further-
more, there are social costs associated with detention ponds, namely large
land requirements (estimated at 0.5 to 2 percent of the catchment area),
unattractive aesthetics, and public safety concerns. 58 Finally, there are sig-
nifi cant challenges in maintaining these systems over time, from removing
captured pollutants to controlling insects and rodents and monitoring to
determine when they need to be replaced or upgraded. 59 In effect, deten-
tion ponds require a high level of management costs by local governments
while providing only partial environmental protection.
Other stormwater management strategies involve a variety of so-called
best management practices (BMPs) such as ponds, vaults, tanks, sepa-
rators, swales, fi lter strips, wetlands, basins, perforated pipes, trenches,
French drains, sand and biological fi lters, and porous pavements. These
strategies are used to store, treat, and infi ltrate urban runoff volumes to
mitigate issues of fl ooding, soil erosion, and water pollution. The end-of-
pipe treatment strategies of conventional stormwater management have
a wide range of effi cacy for pollutant removal and are not particularly
reliable, despite the claims of product manufacturers and designers (see
table 1.1). 60 Urban runoff continues to confound engineering solutions,
although there has been an enormous amount of scientifi c research, pi-
lot studies, regulations, construction, administration, and maintenance
of these systems. In other words, nonpoint source pollution problems
have largely eluded the Promethean promise of the complete control of
nature. 61 At the end of the twentieth century, over half of the receiving
water bodies in the United States did not meet their designated water
uses and water quality goals as specifi ed in the CWA. 62 It is tempting to