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.
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”.
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.
Results from all of the three condition assessment efforts were compiled and used to develop the City’s Long Range Sewer Rehabilitation Plan.
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.
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.
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 two-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.
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.
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.
The task of assessing the City’s entire wastewater collection system within the mandated five-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.
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.