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Final Facilities Plan
October 2005 Executive Summary
This Facilities Plan for the Carnation Wastewater Treatment Facility (CWWTF) has been
prepared in accordance with the Submission of Plans and Reports for Construction of
Wastewater Facilities (2000) Washington Administrative Code (WAC) 173-240 for submittal
to the Washington Department of Ecology (Ecology). This plan is designed to demonstrate
that the proposed project will meet the applicable guidelines, regulations, and approval
requirements for issuance of a discharge permit. In addition, the Facilities Plan serves as a
comprehensive guide to the project.
The City of Carnation (City) is located on the Snoqualmie River within the Snoqualmie
Valley (see Figure 1.1) and is an incorporated city within King County (County). At the
request of the City, the County proposes to build and operate a new local wastewater
treatment facility and associated river outfall to meet the needs of the City’s designated
Urban Growth Area (UGA) for a 2030 facility design year. The City will construct and
operate a vacuum sewer collection system for the conveyance of sewage from residences
and businesses within the City to the treatment facility. An agreement between the County
and the City, attached as Appendix C (PDF, 1.3 MB) of this plan, requires the facility to be operational by
December 2007.
Historically, the City has relied on a system of individual septic tanks and drain fields.
In 1987, Public Health − Seattle & King County (Public Health) declared the City a public
health hazard area based on the number of inadequate septic systems and the likely
contamination of the unprotected aquifer from which drinking water is derived. Public
Health made this declaration based on the soil conditions within the City, documented
illegal sewage disposal repairs, and informal surveys confirming inadequate systems. Due
to the costs associated with a lot-to-lot survey and comprehensive ground water studies,
Public Health has been unable to determine the full extent of the health threat. Since then,
Public Health has taken the step of restricting property use or prohibiting remodeling
projects in cases where the long-term protection of public health is at risk. Legal repairs to
existing septic systems on inadequately sized lots may require a notice of nonconforming
repair on the property deed of records. Attached as Appendix D, Public Health issued a
letter on September 28, 2005 that indicates that due to continued public exposure to
surfacing sewage and untreated sewage entering the groundwater aquifer, current on-site
sewage disposal practices in the City are clearly inadequate and present a Severe Public
Health Hazard to the community. As a result, Public Health supports the development of a
sewer system for the City. Public Health views the system remains the “most viable solution
for the long-term protection of the public’s health.” Replacing on-site septic systems with a
wastewater treatment facility is important to address public health concerns, achieve the
City’s comprehensive plan goals, and enhance community livability.
Hard Copies of the Final Facility Plan
Copies of the Final Facility Plan are available for review at:
King County Wastewater Treatment Division
Environmental Planning
201 South Jackson Street, 5th Floor
M.S. KSC-NR-0505
Seattle, WA 98104
see map
The Adobe Acrobat reader is required to view .pdf files linked off of this page. You can obtain a free copy by visiting Adobe's Web site.
Final Facilities Plan, entire document, October 2005 (21.6 MB)
Detailed contents of Final Facilities Plan
Report Cover (191 KB)
Title Page with engineer stamps (44 KB)
Table of Contents (138 KB)
Acronyms and Abbreviations (133 KB)
1.0 Executive Summary (986 KB)
2.0 Purpose and Scope (925 KB)
3.0 Existing Environment (8.1 MB)
4.0 Discharge Standards (335 KB)
5.0 Future Conditions (274 KB)
6.0 Preliminary Development of Principal Alternatives (2.8 MB)
7.0 Final Recommended Alternative (3.3 MB)
8.0 Financial Analysis (133 KB)
9.0 Project Implementation (143 KB)
Appendices
A – City of Carnation 2004 Comprehensive Sewer Plan, Executive Summary (120 KB)
B – City of Carnation 2004 Draft Sewer Facilities Plan, Executive Summary (127 KB)
C – King County - City of Carnation Agreement for Sewage Disposal (1.3 MB)
D – Severe Public Health Hazard in the City of Carnation Letter (118 KB)
E – City of Carnation Water Reuse Interest Letter (229 KB)
F – Preliminary Cost Comparison (107 KB)
G – Salmonid Use of the Snoqualmie River - Tolt Delta Reach (318 KB)
H – Discharge Hydraulix™ (121 KB)
I – Reliability Checklist and Water Quality Comparison (125 KB)
J – Conveyance Cost Estimate Support (248 KB)
K – Alternate WWTF Cost Estimate (discharge to SWA) (161 KB)
L – Public Involvement Chronology (204 KB)
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