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LONG RANGE SEWER REHABILITATION PLAN
City & County of Honolulu
(page 1 of 3)
SUMMARY
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In 1992, the City & County of Honolulu (City)
was served with a notice of violation by the U.S. Environmental
Protection Agency (EPA) for alleged violations of the Federal Clean
Water Act, due to repeated spills from its extensive sewage collection
system. The City was mandated to control these overflows, which were
deemed a severe threat to public health, safety and welfare. The City
selected Fukunaga & Associates, Inc. (FAINC) to conduct a
comprehensive assessment of the condition of the City’s aging sewer
system and to formulate a proactive rehabilitation plan to improve the
City’s sewers. |
Sanitary Sewer Overflow
(SSO) occurring on a
city street. |
In 1995, a Consent Decree agreed to by the City, the
Hawaii State Department of Health (DOH) and EPA, was filed in Federal
court, requiring the City to prepare a comprehensive Sewer
Rehabilitation Plan by December 31, 1999. FAINC and its subconsultants
worked closely with the City to develop the Long Range Sewer
Rehabilitation Plan, meeting all mandated deadlines and requirements
established in the Consent Decree. This plan was approved by EPA and
has been identified by EPA Region IX as a "model program".
BACKGROUND
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Unlike potable water distribution systems, sewage
collection systems are not expected to be "water-tight". It
is common practice to design sewer systems to handle wastewater flow,
and also accommodate a nominal amount of extraneous water, known as
infiltration and inflow (I/I). Infiltration occurs when water enters
the sewers through defects such as leaky pipe joints, and cracked or
corroded pipes and manholes. Inflow occurs through manhole covers,
cleanout pipes or illegally connected area drains or roof downspouts.
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Infiltration occurring
through cracked pipe |
When storms occur, this extraneous water, called "wet weather
I/I", can cause the total flow to exceed the hydraulic capacity of
the collection system, resulting in spills, referred to as sanitary
sewage overflows (SSOs). SSOs threaten public health because they can
expose people to disease-causing organisms called pathogens that are
present in sewage.
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The City’s task to develop a sewer rehabilitation
plan addressing these spills was formidable because it was dealing with
a large, complex and aging system. The City presently collects, treats
and disposes over 120 million gallons of wastewater every day through
1800 miles of collection lines. The plan had to effectively address
existing system deficiencies, factor in future development
requirements, and program the necessary improvements over a 20-year
time frame within a schedule that the City could reasonably afford.
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Infiltration through
deteriorated sewer
manhole wall |
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