Quartermaster Harbor Community System Wastewater Treatment Options Report

King County Environmental Health has identified failing septic systems in communities adjacent to Quartermaster Harbor on Vashon Island. This area was the subject of a 1993 Facilities Plan that addressed alternatives to on-site septic systems for four communities on Vashon Island that were declared Health Hazard Areas (HHAs) by the Washington State Department of Health. The Facilities Plan provided an evaluation of costs and environmental issues as well as preliminary design of a preferred alternative for each community and steps to implementation.

This report identifies treatment and disposal alternatives, estimates life cycle costs, and discusses the jurisdictional structure already in place for establishing community wastewater treatment in the study area.

	Executive Summary
	Cover, table of contents and appendices A - F
	Chapter 1 Outlines the basis for a wastewater management system for the study area. The study area boundaries are defined as well as the number of parcels and population within the study area. Study area land use and environmental characteristics are described. Estimated wastewater flow for the study area is presented based on water usage.
	Chapter 2 Describes the process of establishing management of the community wastewater system for the study area. Potential sources of funding that might apply to wastewater projects are discussed.
	Chapter 3 Centralized treatment involves collection and conveyance of wastewater from the study area to the Vashon WWTP via the VSD collection system. Sewage would be collected from individual parcels to a central point in the study area through one of three types of collection technologies - gravity, vacuum, or low-pressure, or a combination of these technologies.
	Chapter 4 Discusses the regulatory structure for decentralized systems, the process options for both discharge and treatment, and presents schematic development of four options including footprint and cost estimates.
	Chapter 5 Describes criteria for sizing and arrangement of holding tanks as a permanent onsite wastewater management options. This chapter summarizes applicable regulations, discusses system components, configuration, and design criteria, as well as operation/maintenance requirements and life cycle costs.
	Chapter 6 Consolidates the cost information presented in the previous chapters and presents a life cycle cost analysis.

	Figure ES 1 Magnolia Beach - Greater Burton Study Area		Figure 4.8 Mound system
	Figure ES 2 Centralized Treatment Option, Conceptual Conveyance System		Figure 4.9 Aerobic treatment unit
	Figure 1.1 Magnolia Beach - Greater Burton Study Area		Figure 4.10 Sequencing batch reactor
	Figure 1.2 Magnolia Beach - Greater Burton Study Area, Environment Areas		Figure 4.11 Membrane bioreactor
	Figure 1.3 Study Area Land Use and Developed Parcels		Figure 4.12 The living machine
	Figure 3.1 Centralized Treatment Option, Conceptual Conveyance System		Figure 4.13 Potential Decentralized Treatment/Discharge Sites
	Figure 4.1 Conventional trench detail		Figure 4.14 Potential Sites, Soil Survey and Water Wells
	Figure 4.2 Drainfield area requirements		Figure 4.15 Community conventional drainfield
	Figure 4.3 Typical septic system schematic		Figure 4.16 Recirculating gravel filter and subsurface drip system
	Figure 4.4 Intermitten sand filter		Figure 4.17 Sequencing batch reactor and percolation pond
	Figure 4.5 Sand lined trench		Figure 4.18 Membrane bioreactor and percolation pond
	Figure 4.6 Stratified sand filter		Figure 5.1 Single residence holding tank configuration and selected setback requirements
	Figure 4.7 Recirculating gravel filter		Figure 5.2 Multi-family holding tank configuration