Environmental Engineering Reference
In-Depth Information
high level of treatment in a small footprint, as well as modest long-term
maintenance requirements.
The early codifi cation of high-effi ciency treatment strategies is simul-
taneously a strength and a weakness of the municipality's water quality
program. Although it represents a strong commitment to protecting wa-
terways from urban runoff impacts, it also tends to limit the choice of
treatment strategies. A consulting engineer notes, “The downside is that
the high standards discourage innovation to some extent because you have
to get variances to do anything that isn't approved in the manual, and
variances are hard to get. So you don't see much experimentation here
because the rules call for sand fi lter or equivalent.”
26
In other words, the
reliance on a proven technology as specifi ed in the municipal regulations
comes at the expense of innovation in treatment strategies. The regulatory
structure creates particular expectations for the existing drainage system
and a “technological momentum” to continue stormwater management in
the established manner.
27
As a result, more recent source control strategies
have not been adopted because of the diffi culties in proving equivalence
with existing end-of-pipe strategies.
28
In the mid 2000s, municipal staff
members updated the city's
Environmental Criteria Manual
to include a
handful of source control measures, including vegetated fi lter strips, rain
gardens, rainwater harvesting, porous pavement, and biofi ltration, but the
majority of new development projects continue to rely on conventional
strategies with established performance records. A Watershed Department
staff member notes: “The development community wants to use [source
control] techniques more than we do. I think if we already had green
roofs, rainwater harvesting, bioretention, and porous pavement in our
regulations, people would be using these techniques right now. They want
to use it and they want to get credit for it but it's not very explicit. You
could do something alternative but it's a hassle and it slows your project
down, so no one wants to do it.”
29
The municipal water quality regulations stabilize the network of nature
and society in the urban environment via well-established technological
strategies, just as the watershed ordinances stabilize land development
practices in the Hill Country. The codes can be understood as a means
of translating the water quality interests of Austin residents into material
practices, but the resulting system of regulations is obdurate, resisting
modifi cation and circumvention by newer strategies based on the assump-
tion that they cannot meet existing pollutant removal thresholds. Although
the establishment of the water quality program in the 1980s is inter-
preted by many as a signifi cant achievement, evolution of the program in
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