Septic to Sewer - Reference Maps
Maps depicting the City's sewer infrastructure and available ranking criteria for prioritizing septic system conversions are provided in printer-friendly PDF formats below. When viewing the PDF files in Adobe Reader, use the zoom tools to focus in on your neighborhood.
Sewer Infrastructure Map:
Depicts sewer pipes based on mapping as of January 2008.
Septic Density Map: Depicts septic system density as determined by City of Olympia staff using geographic information systems software based on the centroid of properties assumed to have septic systems.
Wellhead and Watershed Protection Areas Map: Depicts wellhead protection areas based upon Wellhead Protection Area Delineation for the City of Olympia Wellfield Areas, performed by Golder Associate, Inc., dated May 20, 2008. The Henderson Inlet Shellfish Protection District boundaries are based on the Thurston County Board of County Commissioners Ordinance No. 13470 adopted November 21, 2005.
Septic System Age Map: Depicts assumed septic system ages estimated using the effective year built for a property according to Thurston County parcel information.
Wetlands, Surface Water, and Buffer Areas Map:
Depicts wetlands based on a composite created by Thurston Geodata Center of the wetland delineations identified by The Thurston Regional Planning Council (TRPC) staff and the National Wetlands Inventory data completed in December 2002. Surface water bodies are based on Thurston Geodata Center data.
Soil Characteristics and Depth to Groundwater Map: Depicts soils categorized as moderate or severe for septic tank absorption fields in the Soil Survey of Thurston County, Washington, performed by the Soil Conservation Service in 1982.
- "Moderate" indicates soil properties are not favorable for septic tank absorptions fields and special planning, design, or maintenance is needed to overcome or minimize the limitations.
- "Severe" indicates soil properties are so unfavorable or so difficult to overcome that special design, significant increases in construction costs, and possibly increased maintenance are required. Soils where the water table is indicated to be within 3 feet or less of the ground surface are categorized as having high groundwater.
Conversion Criteria Ranking Map:
Parcels assumed to be served by septic systems were ranked with one point each being given for each of the following seven criteria:
- Within surface water bodies and wetlands buffer areas
- Within wellhead protection areas
- Within the Henderson Inlet Shellfish Protection District
- Within areas of septic density exceeding 2 septic systems per acre
- Assumed to exceed an age of 25 years
- Having soils categorized as severe
- In an area of high groundwater
The conversion criteria ranking is a basic tool to help utility staff make recommendations for neighborhood sewer extension projects. Essentially, the higher the ranking number, the higher the assume risk to public and/or environmental health.
Other criteria, including neighborhood interest and septic system failures, will also be considered in selecting neighborhood sewer extension projects, but have not been mapped or ranked. Neighborhood interest is being gauged through responses to surveys mailed to septic system owners. Utility staff recommendations for neighborhood sewer extension projects will require the approval of the Utility Advisory Committee. Other criteria including neighborhood interest and septic system failures have not been mapped or ranked.
Contact Us: Contact Eric Christensen at 360.570.3741, Diane Utter at 360.753.8562, or send an e-mail.
Need More Information about Public Works Programs or Services? Contact the Public Works office.
- Physical Address: 924 7th Ave. SE, Suite A
- Mailing Address: PO Box 1967, Olympia, WA 98507-1967
- Download printer-friendly (PDF) directions to our office
- Hours: M - F from 8 a.m. to 5 p.m. (except for City-recognized holidays)
- Phone: (360) 753-8588
- TTY: (360) 753-8270
- Email: Public Works