Environmental Engineering Reference
In-Depth Information
$14.0
Total (in 2000 dollars)
CWSRF
EPA line item
Construction grant
12.0
10.0
8.0
6.0
4.0
2.0
0.0
1970
1975
1980
1985
1990
1995
2000
Figure 2.2
Federal funding for wastewater infrastructure, 1970-2000.
Note:
CWSRF = Clean Water
State Revolving Fund. (Source: EPA, Report to Congress: Impacts and Control of CSOs
and SSOs, Washington, D.C.: EPA, 2004.)
the homeowner. But it is not always clear who is responsible for sewage
bubbling up in a basement, and, as with other parts of our underground
infrastructure, local offi cials and voters have tended to treat sewers as
an out-of-sight, out-of-mind problem.
Older municipal sewer systems are powered almost entirely by gravity
rather than by large pumps, which means that when they are working
properly, they move millions of gallons of sewage daily across consider-
able distances with only a minimum expenditure of energy, a feat of
effi ciency virtually unparalleled in the annals of engineering. New York
was one of the fi rst cities to build a large sewer system, starting construc-
tion in 1849, the year President James Polk annexed California; the sewer
system operates almost entirely by gravity.
Most of the time, backups in sewers are caused by tree roots, although
many of the items produced and discarded in our industrial civilization
can also cause problems. If a pipe has even a pinhole leak, which often
occurs at joints, trees near the pipes will fi nd it, and tiny root tendrils
will begin slowly working their way into the opening and grow, eventu-
ally forming dense root balls through which solids cannot pass. No way
has been found to stop this.
