The Dilemma of Water in the City - Politics of Urban Runoff: Nature, Technology, and the Sustainable City - page 6

systems was justifi ed by the prevailing theory of miasmas held by public
health offi cials that disease was transmitted through gases emanating from
the decay of waste. Although the theory was scientifi cally fl awed, it em-
phasized sanitation as a primary focus of nineteenth-century city builders
and called for the removal of sanitary wastes to avoid epidemics. 27 A clean
city was a healthy city, and cleansing would be accomplished through
the adoption of the water-carriage system to remove disease-causing
wastes.
Urban drainage fl ows were implicated with the new water-carriage
system for sanitary wastes through the construction of combined sewer
systems, in which both sanitary and stormwater volumes were conveyed
in a single pipe. For nineteenth-century engineering and sanitary experts,
the combined sewer design was a cost-effective and effi cient solution that
avoided the buildup of miasmas that were thought to be produced by
standing water. 28 However, other technical experts advocated for sepa-
rated sewers in which sanitary wastes were carried in a smaller pipe and
stormwater volumes were carried either in a larger pipe or in ditches on
the surface. Engineers who promoted the separated sewer design argued
that sanitary wastes contained valuable organics that could be recovered
and used as agricultural fertilizer.
The choice of combined versus separate sewers was complicated by a
number of factors including hydraulics, cost, design features, perspectives
on disease transmission, and the infl uence of internationally recognized
sewerage experts such as Colonel George E. Waring Jr. However, by the
1890s, most engineers concluded that both systems provided equivalent
sanitary services, with combined systems being more appropriate in large
cities where space for the surface conveyance of urban runoff was infea-
sible. 29 In essence, population density and economic development took
precedence over hydrologic fl ows in large cities, which required water
fl ows to be relegated underground. The variety of sewer networks fi rst
built in the nineteenth century would result in a hodgepodge of drain-
age networks, often within the same city, including surface networks,
subsurface separated sewers, and subsurface combined sewers. 30 In many
cases, these networks continue to be used today due to the high cost and
disruption associated with upgrading them.
With respect to the Promethean Project, urban drainage would involve
increasingly sophisticated hydrologic approaches to convey these water
volumes to downstream receiving waterbodies. Water was interpreted as
an unruly element in the urban landscape and the enclosed pipe was the
primary strategy to discipline it. 31 As a whole, stormwater engineering