This Comprehensive Wastewater System Plan is a summary of the conclusions and findings completed by Penhallegon Associates Consulting Engineers, Inc. and Brown and Caldwell, Inc. in analyzing Lakehaven Utility District's existing wastewater collection and treatment systems. The Plan updates and supercedes the District's previous (1983) Comprehensive Sewer Plan and has been prepared in accordance with all applicable regulatory requirements. The primary goals of the planning effort were to:

1. Determine the adequacy of the existing wastewater collection and treatment system to meet the current and projected needs of the District's customers in accordance with all state, federal and local regulations, as well as current industry standards.
2. Develop recommendations for system improvements which meet the wastewater collection and treatment system needs, are environmentally sound and protect public health and welfare.
3. Identify potential mechanisms for funding recommended studies, improvements and other recommendations of the Plan.

The following is a summary of the key elements of the planning process and sections of the Plan:

Introduction

This section presents an overview of the study, history and objectives of the District, and a summary of the rules and regulations which govern the operation of the District and the development of the Comprehensive Planning Document.

Basic Planning Data

Lakehaven Utility District currently serves within the corporate limits of eight jurisdictions. The future service area identified in the Plan extends to the District's corporate boundary, which represents a significant change from the previous Comprehensive Plan. This change is the result of Growth Management Act planning, which eliminates the previous restriction associated with Local Service Area designations and establishes an Urban Growth Area (UGA) within which urban levels of service are to be provided. The entire corporate boundary of the District is within the UGA and the District is therefore responsible for planning accordingly.

Demographics

Population and employment forecasts are based on the adopted land use plans of the various jurisdictions within which the District operates. They are presented by drainage basin to allow for evaluation of the system and consideration of future improvement alternatives. As of 1997, there were approximately 109,000 residents and 37,000 employees within the District's corporate boundary. The population is projected to increase to nearly 121,000 by 2003, and almost 150,000 by the year 2017. Employment is expected to increase to more than 42,000 by 2003 and more than 52,000 by 2017. An estimated 7,500 on-site wastewater disposal systems are in operation within the corporate area. It is anticipated that service will be extended to these unsewered areas as on-site systems become less viable to maintain and/or new development requires public sewers.

Flow Projections

Average daily flow from the District, is currently (1997) estimated at 11 MGD and is expected to increase to nearly 13 MGD by 2007, 15 MGD by 2017, and nearly 25 MGD at full development. Peak flows, including infiltration and inflow (I & I), are estimated at 21 MGD in 1997, 33 MGD by 2007, 35 MGD by 2017, and 48 MGD at full development.

Existing Wastewater Collection System

The existing collection system consists of approximately 275 miles of sanitary sewer pipes, 6,500 manholes, 27 pump stations, six siphons and two secondary wastewater treatment facilities. The system has been constructed over a number of years, and from a wide variety of materials, as dictated by development trends in the area. The system is divided into seven primary basins and 40 smaller sub-basins. The two largest basins, Lakota and Redondo, flow to the District's wastewater treatment plants. The remaining basins currently discharge to other utilities for treatment and disposal.

Collection System Analysis/Recommended Improvements

Analysis of the collection system was accomplished with a computer modeling system using the design criteria established in the Plan. Primary issues resulting from analysis of the collection system were related to normal renewal and replacement programs, I & I control in the older areas of the system (especially Redondo), capacity issues related to growth and the reconfiguration of drainage basins to maximize capacity in the existing treatment facilities and minimize pump station requirements. Collection system improvement projects identified in the Capital Facilities Plan are representative of these findings, as well as extension of service to currently unsewered areas.

Treatment Facilities Analysis

The Lakota Plant was constructed as a primary treatment plant in 1967 and upgraded to secondary treatment in 1991. The Lakota plant was designed for a peak month flow of 10 mgd and a peak hour flow of 22.2 mgd. The Redondo plant was constructed as a primary treatment plant in 1962 and upgraded to secondary treatment in 1983. The Redondo plant was designed for an annual average flow of 4.32 mgd and a peak hour flow of 13.8 mgd.

Hydraulic Capacity Analysis

Analyses were performed using 1992-1997 data during which period annual wastewater flow to Lakota increased 10% to 4.12 mgd and to Redondo increased 25% to 3.0 mgd. Peak hour flows for 1997 were 11.3 at Lakota, 11.2 at Redondo (the latter was estimated due to flowmeter limit). Hydraulic capacity at both plants is estimated to be available up to the original design peak hour capacities of 22.2 mgd for Lakota and 13.8 mgd for Redondo.

Lakota Process Capacity Analysis

Analyses were performed on 1992-1997 data and individual process unit capacities were compared to Washington State design criteria. Limiting criterion at Lakota is peak month capacity. Primary treatment comprises screening, grit removal and primary clarifiers and has adequate capacity. Grit and primary scum removal need improvement to protect and optimize downstream processes. Secondary treatment comprises aeration basins, secondary clarifiers and chlorine disinfection. Process analysis showed peak month capacity at 9.2 mgd for the aeration process (limited by air diffusion capacity) and 10.5 mgd for the secondary clarifier process vs. the overall design capacity of 10 mgd. The estimated dry weather capacity is 7.2 mgd and is limited by air diffuser capacity. Solids treatment comprises thickening, digestion and dewatering and has adequate capacity. Of the three solids processes, digestion has the least reserve capacity at 20 percent. The overall process design capacity of 10 mgd can, in practice, be achieved by higher capacity processes compensating for lower capacity processes

Redondo Process Capacity Analysis

Analyses were performed on 1992-1997 data and individual process unit capacities were compared to Washington State design criteria. Limiting criteria at Redondo is peak hour capacity. Primary treatment comprises screening, grit removal and primary clarifiers and has adequate capacity. Grit removal needs improvement to protect and optimize downstream processes. Manual screenings removal is labor intensive and could be automated. Secondary treatment comprises aerating trickling filters, secondary clarifiers and chlorine disinfection. Secondary capacity, and consequently overall process capacity, is limited by clarifier capacity. However, clarifier capacity can be partially compensated for in other processes. Solids treatment comprising digestion and dewatering has adequate capacity. Limited thickening is achieved in the process tanks rather than a separate thickening process.

Recommended Treatment Facility Improvements

The recommended improvements fall into two categories, general improvement requirements and capacity expansion requirements. General improvement are those needed to improve individual processes and provide improved control of the plants. Capacity improvements are those needed to accommodate future wastewater flows.

Biosolids

Dewatered biosolids cake from both plants, stabilized to Class B quality in the digesters, is trucked to compost producers. Metals content in the biosolids has been consistently well below EPA regulatory limits for land application and is currently below EPA limits for "clean" biosolids.

Water Reuse

The District is evaluating the feasibility of municipal wastewater reuse to offset potable water use. The November 1998 Comprehensive Water System Plan by Kennedy/Jenks Consultants, provided an evaluation of the feasibility of wastewater reuse. Landscape irrigation and groundwater recharge are the two potential reclaimed water uses identified within the District. However, because of the potential cost and regulatory uncertainties, at this time water reuse possibilities are limited. Future reclamation treatment facilities would be located at the Lakota WWTP and possibly the Redondo WWTP, if implemented.

Financing Options

Several typical funding options are available to the Lakehaven Utility District. These include the following: State and Federal Grants and Loans; Bond Financing, both General Obligation Bonds and Revenue Bonds; Privatization; Leasing; Pay-As-You-Go; Capital Reserve Funds; Development Based Funding; and Connection Fees.