LAND AS THE RESOURCE - Low Impact Development and Sustainable Stormwater Management - page 67

regions of the country, the implementation process will evolve through more con-
siderate design efforts that shape the development to fit the land rather than the
current opposite practice.
3.7 URBAN COMMUNITIES WITH COMBINED SEWER OVERFLOWS
In many older cities, especially along the East coast but not limited to the East, the
sewer system consists of a single pipe, in which both sewerage and stormwater
are “combined,” an unfortunate consequence of historic development patterns
that took shape during the late nineteenth century (Figure 3-15). During periods
of rainfall, these sewage systems overflow to surface waters when the hydraulic
capacity of the conveyance system is exceeded, resulting in one of the most
serious impacts on water quality of the twenty-first century. The discharge from
these overloaded sewers occurs at outlets described as combined sewer overflows
(CSOs) and is a legacy of urban expansion. From New York and Philadelphia
to Chicago and Kansas City and as far west as Portland and Seattle, the issue
overwhelms the redevelopment process in urban environments and has created
a multi-billion-dollar headache for many cities that face a multiplicity of other
problems, from population migration and the loss of tax base, to traffic, crime,
and schools. The cities simply cannot afford the additional cost of replacing
the urban infrastructure of sewers, despite litigation by the U.S. Environmental
Protection Agency to force resolution through the federal court system.
The application of LID concepts to these communities is driven by the simple
fact that if rainfall is prevented from discharging to the combined sewer, it
Figure 3-15 Sewer construction in the late 1870s buried most urban streams and turned
them into sanitary and storm sewers, with combined discharge to tributary rivers.