The Dilemma of Water in the City - Politics of Urban Runoff: Nature, Technology, and the Sustainable City - page 14

Table 1.1
Average pollutant removal rates as a percentage for common stormwater BMPs

Strategy Total suspended solids Total phosphorous

Dry extended detention pond 25 to 81 10 to 40

Wet basin 33 to 97 29 to 75

Stormwater wetland 43 to 93 16 to 68

Bioretention fi lter 75 to 95 61 to 83

Sand fi lter 68 to 96 15 to 77

Infi ltration trench 90 to 100 30 to 100

Source : Weiss, Gulliver, and Erickson 2007, 226.
Note : Represents the 67 percent confi dence interval. Some values are assumed.

blame technical experts and ineffective local governments for this failure,
but the confounding character of nonpoint source pollution is a classic
“wicked problem” of environmental protection—one that is not easily
solved through technomanagerial activities.
One of the most signifi cant barriers to effective stormwater manage-
ment is that cities were already in place before water quality issues were
raised. Thus, retrofi tting has enormous costs because the embedded logic
of effi cient conveyance is diffi cult to reverse both materially and admin-
istratively. 63 Moreover, urban runoff is not amenable to conventional
“command and control” forms of environmental management due to its
dispersed and low concentration character. 64 It is a systemic problem that
transcends technical and administrative rationality because it implicates
a whole host of urban development activities, from impervious surface
propagation to land use and zoning regulations, growth management,
resident behavior, the location and character of vegetation, maintenance
schedules, and so on. There is a fundamental mismatch between the end-
of-pipe strategies that dominate conventional stormwater management
and the complex character of urban runoff.

Conclusions

Historic and contemporary practices of urban drainage have contributed
to the supposed separation of the city from nature. Engineers played a sig-
nifi cant role in rationalizing urban water fl ows to allow for urban growth
by constructing urban drainage networks that could convey stormwater as
quickly as possible away from cities. The 1960s marked a turning point
in urban runoff practices from a logic of effi cient conveyance to focus on