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LONG RANGE SEWER REHABILITATION PLAN
City & County of Honolulu
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LONG RANGE SEWER REHABILITATION PLAN
The City’s Long Range Sewer
Rehabilitation Plan includes conceptual CIP projects formulated to
address existing hydraulic and structural deficiencies identified in
the assessment phase of the program. The Rehabilitation Program will
systematically address the deficiencies identified in the assessment
effort over the 20-year (2000 - 2019) implementation period. I It is
estimated that the rehabilitation program will cost $890 million over
the next 20 years. However, the cost of the program is considered
affordable and is consistent with the City’s long range financial
plan that was developed in parallel with the Sewer Rehabilitation Plan.
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The Rehabilitation
Plan was developed to apply a "Holistic Approach",
considering all aspects of the collection system as a complete (or
"whole") functioning system. The objectives are to
minimize existing SSOs by addressing existing deficiencies,
improve system reliability by preventing future deficiencies
through proactive system planning and monitoring, and to integrate
system expansions by planning system growth and providing
necessary system upgrades. Part of the plan is to continue
monitoring the impact of system improvements, and also to maintain
program flexibility that will allow for adjustments to the Plan in
the future. |
20-Year Sewer Rehabilitation
Capital Improvement Plan |
FUKUNAGA & ASSOCIATES, INC’s ROLE IN THE PROJECT
FAINC served as the prime engineering consultant for the project,
assisting the City in negotiations with EPA, establishing the terms of
the consent decree, for the full term of the Rehabilitation Program
development. FAINC was responsible for the production of all
deliverables and meeting all deadlines. Subconsultants for the project
included Brown & Caldwell of Pleasant Hill, California, providing
technical support and Belt Collins Hawaii, of Honolulu, providing
computer and data management services. ADS Environmental Services, Inc.
and MGD Technologies, Inc. provided flow monitoring and field
investigation support.
INNOVATIVE APPLICATION OF NEW AND
EXISTING TECHNIQUES
As stated earlier, one of the most significant
challenges was the determination of reasonable design flows for
Honolulu’s wastewater collection system. Real data obtained from the
flow monitoring program revealed that the existing Sewer Design
Standards used to design most of the existing sewer systems were
inadequate. To address these deficiencies, theoretical design flows
resulting from storms of various recurrence frequencies were
calculated, and a cost performance analysis was conducted to estimate
the projected occurrence of SSO’s under the various storm conditions.
Based on this analysis, system capacities capable of handling the
2-year design storm provided the optimal containment level, reducing
wet weather SSOs by 78 percent. Increasing system capacity to
accommodate higher magnitude events resulted in only a marginal
improvement in SSO containment, while costing the City significantly
more to implement. By convincing EPA that the selected design storm
level was appropriate and truly optimized the system’s containment
capacity, the City saved several hundred million dollars.
TECHNICAL VALUE TO THE ENGINEERING PROFESSION
The many studies conducted
as part of this project brought to the forefront the numerous
factors and considerations involved in wastewater collection system
planning and design. Each of the studies provided the background
and rationale for the procedures and evaluation methodologies
applied during the formulation of the Plan. A new "standard"
for wastewater flow determination was established, including the
development of a prototype sewer system hydraulic model for Honolulu.
As a result, a more rational approach has been established to
properly size system elements for all future extensions and improvements
to the City’s sewer system.
SOCIAL AND ECONOMIC CONSIDERATIONS
The development of Honolulu’s Long Range
Development Plan required a balance of social and economic
considerations. The primary goal of the Plan was to protect public
health and the environment. However, the level of protection had to be
cognizant of the economic cost to the public. Therefore,
cost-effectiveness and cost performance were keywords in the
development of the plan. Flexibility and performance monitoring were
also incorporated into the Final Plan, giving the City the ability to
revise and modify the conceptual projects should future conditions
warrant such changes.
COMPLEXITY
The task of assessing the City’s entire wastewater
collection system within the mandated 5-year time frame appeared
monumental at the onset of the project. The study encompassed over
1,800 miles of sewer lines, 67 wastewater pumping stations and 8
wastewater treatment plants. During the course of the project, the
program included flow and rainfall monitoring, hydrologic analyses,
field investigations (manhole entry and CCTV inspections), chemical
sampling, corrosion modeling and analyses, hydraulic modeling of the
entire collection system, and the development of alternative solutions
to address structural, hydraulic and operational deficiencies. All work
was closely monitored by EPA throughout the project duration; and the
methods, results and recommendations were subject to their approval.
MEETING AND EXCEEDING THE CLIENTS EXPECTATIONS
The Sewer Rehabilitation Plan was completed on time and under the
original budget projected by the City. The improvements recommended in
the Plan (estimated to cost $890 million over the next 20 years) are
considered to be affordable, based on projected and approved sewer user
fee schedules. The Plan was submitted in December 1999 and accepted by
EPA in March 2000. This unprecedented action was made possible because
of the open, on-going dialog with EPA. The consultant team was at the
forefront of these discussions, accompanying City officials to EPA
Region IX, headquarters in San Francisco on numerous occasions to
negotiate the final requirements. In the end, Honolulu’s Sewer
Rehabilitation Plan has been described by EPA Region IX as a
"model program," meeting all mandated deadlines and
requirements set forth in the Consent Decree.
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