Chapter 2 - Background Information

In this chapter we provide basic planning and physical environment information as context for discussion in the following chapters. We use community trends in land use, population and demand for sewer service as the basis for projecting wastewater flows and future wastewater infrastructure and program needs. The physical landscape dictates to a certain extent the types of sewer collection and conveyance systems that are most appropriate for each basin within the Sewer Service Area.

This chapter also gives an overview of the state and federal regulatory environment associated with planning, constructing, operating and maintaining wastewater infrastructure; a brief discussion of other plans that relate to water-based resources in our community; and some of the agreements in place among the LOTT partners that relate to wastewater.

2.1 Sewer Service Area

The City of Olympia is located on Budd Inlet at the southern end of Puget Sound. The Wastewater Utility’s Sewer Service Area (see Figure 2.1) includes the 17.5 square miles of the City, its Urban Growth Area (UGA) (approximately eight square miles in unincorporated Thurston County), several areas in the Cities of Tumwater and Lacey for which service agreements have been executed, and a small area outside its western UGA which received sewer service before the City’s UGA boundaries were established under the Growth Management Act. Appendix M includes a larger scale map showing the Sewer Service Area.

Many neighborhoods and individual lots within the City and its UGA, including unincorporated "islands" within the external boundaries of the City, are still using onsite sewage systems (OSS). See Chapter 4 for a discussion of OSS, and current City and Thurston County policies regarding them.

The Sewer Service Area is divided into six major watersheds, or basins, also shown in Figure 2.1, to facilitate watershed-based planning strategies. Chapter 5 discusses each basin in more detail, including the characteristics and challenges associated with each of them.

View Figure 2.1 Wastewater Utility Service Area and Watershed Basins

2.2 Population and Land Use

Population and Demand for Sewer Service

Population data in this Plan is based on data published by the Thurston Regional Planning Council (TRPC) and electronic source data obtained from the TRPC. Historic population trends for the City of Olympia are shown in Table 2.1. Table 2.2 and Figure 2.2 show population forecasts. Given current wastewater policies and regulations, the vast majority of new population in Olympia will be served by municipal sewer service.

Table 2.1

Olympia and UGA Historic Population Trends*





















*Source: Thurston Regional Planning Council

View Figure 2.2 Population Projections


Table 2.2

Olympia and UGA Population Forecast

























Land Use Trends

From 2004 to 2007, residential and commercial properties developed rapidly in Olympia, its UGA, and the adjacent cities of Lacey and Tumwater. During this period, Olympia permitted relatively large subdivisions at an increasing rate, with approximately 300-500 homes constructed per year. Urban villages and other planned unit developments were constructed. Southeast Olympia and the adjacent UGA experienced the greatest development pressure. Areas of northwest Olympia and, to a lesser extent, northeast Olympia also developed rapidly.

While overall construction activity in Olympia and its UGA leveled off and remained relatively steady from 2007 to 2011, especially compared to its municipal neighbors, Lacey and Tumwater, residential housing construction dropped dramatically for all three cities. In Olympia, near term growth projections indicate slow but steady growth in residential construction. In 2011, 75% percent of new home construction was single family residential and 22% multifamily.

Projected Growth Patterns

While there are no clear trends as to growth in one particular area of the City, Thurston County Regional Planning Council data on housing starts and population indicate that growth in the near term (one to six years) will continue to be focused in urban areas, rather than rural areas of Thurston County. Also, while most new housing starts will continue to be single family residential, there will be an increase in the density of housing and numbers of multifamily housing units constructed.

2.3 Wastewater Flows

Demand for sewer service is calculated using a value called an "Equivalent Residential Unit" (ERU). ERUs create a common base for estimating the amount of wastewater generated from both residential and commercial sources. Olympia uses data provided by its Utility Billing section and the LOTT Clean Water Alliance to calculate the number of ERUs served and the average winter wastewater flow per single family residence. These calculations generate an average winter wastewater flow of about 130 gallons per day per single family residence.

ERUs are used to plan infrastructure needs and define billing rates. Combining these typical wastewater flows with projections of future connections allows us to evaluate system capacities and needs. Projected growth data provided by the Thurston Regional Planning Council (TRPC) is used to compute the projections of future ERUs in Table 2.3.

Table 2.3

ERUs for Olympia’s Sewer Service Area1








Single Family ERU’s







Multi-family ERU’s







Commercial ERU’s







Total ERU’s







% Increase







1Based on growth projections from TRPC, and data from LOTT and the City’s Utility Billing.

Table 2.4, summarizing recent historical flows, indicates that wastewater generation has been decreasing since 2007. Reduced wastewater generation even as Olympia’s population grows reflects the effectiveness of community water conservation practices. For more information regarding basin-specific flows, including wet weather flows, see LOTT’s most recent Annual Capacity Report.

Table 2.4

Olympia Wastewater Flows (MGD)1







Average Daily Base Wastewater Flow, MGD






Average Peak Hour Flow, estimated MGD2






1Source: LOTT 2010 Annual Capacity Reports.

2Based on LOTT’s calculation for Olympia of 6.2 as the average ratio of Peak Hour Flow to Base Flow.

2.4 Physical Setting

Water Resource Inventory Area

The City’s entire Sewer Service Area is within Water Resource Inventory (WRIA) Area 13 - Deschutes. This includes the portions of the Sewer Service Area within the Eld Inlet and Henderson Inlet watersheds on the west and east sides of Olympia. Washington Department of Ecology’s initial intent for the WRIAs was to complete drainage basin-specific assessments in order to better understand the relationships between climate, surface water and groundwater in a given area. Elements of the initial assessment, completed in 1995, and the extensive documentation and ongoing research that has followed, include water withdrawals and allocations, hydrology, water quality, and riparian values such as fisheries habitat.

Past and ongoing efforts related to water, water quality and habitat in WRIA 13 include, but are not limited to, establishing seasonal instream flow requirements for the Deschutes River, and characterizing water quality degradation and how to limit or reduce it. Water quality issues and constituents of interest include temperature, pH, fine sediment, dissolved oxygen, fecal coliforms, and nutrients such as nitrogen and phosphorus. These have had an adverse effect on the health of the lower reaches of the Deschutes, as well as most of the urban watersheds within the Cities of Lacey, Olympia and Tumwater.

As a result, the Department of Ecology, with stakeholder input, is in the process of establishing Total Maximum Daily Loads (TMDLs) for some of these constituents, under a process established by Section 303(d) of the federal Clean Water Act. This process has a direct relationship to the issues of onsite sewage system management (see Chapter 4), discharge of treated effluent into Budd Inlet, and potentially groundwater recharge of treated water (see the LOTT Clean Water Alliance discussion in Section 3.6).

In addition, the Henderson Inlet Watershed Management Area has been established to address ground and surface water issues that have impacted shellfish and other species. See Chapter 4 for further information.

Geology and Soils

Geology in Olympia and the rest of Thurston County is the result of glacial activity in Puget Sound. Receding glaciers left the land dotted with lakes, ponds and materials called glacial till or glacial drift, deposited during successive glacial periods. This material varies from fine particles to large rocks and is generally permeable, with the capacity to absorb the 50-plus inches of annual precipitation.

However, soil characteristics present challenges for both gravity sewers and onsite sewage systems. The 1990 Soil Survey of Thurston County Washington identified 30 types of soil within the urbanized Thurston County UGA (U.S. Department of Agriculture Soil Conservation Service, 1990). Only about one percent of the county land area has soils that meet all criteria for ideal functioning of onsite sewage systems (Sandison, 1996). Soils in most of Olympia’s UGA are either too porous, too close to groundwater, or too close to underlying impermeable layers to allow ideal onsite treatment of wastewater. During winter months, many soils are occasionally or consistently saturated.

Construction of gravity sanitary sewer systems is influenced by soil texture, depth to the water table, and linear extensibility (shrink-swell potential), which can influence soil stability. Depth to the seasonal high water table, flooding and ponding may restrict the period when excavation can be done, and slopes create more difficulty when using machinery. The areas with unfavorable soil conditions may limit installation of deep sewers without major soil reclamation, special design or expensive installation procedures. Poor performance and high maintenance can be expected.

In some portions of the City’s Sewer Service Area, especially west and southwest of Ken Lake, there is very little soil on top of the impermeable basalt layer. Soils there are inappropriate for onsite sewage systems and installation of gravity sewers is difficult.

See Chapter 4 for more information on soils and groundwater, and their impacts on onsite sewage systems.


Thurston County’s topography is characterized by coastal lowlands and wooded prairies up to the Cascade foothills. In general, Olympia’s topography slopes to downtown, where the LOTT Clean Water Alliance’s main treatment facility (Budd Inlet Treatment Plant) is located. Land elevation within and between neighborhoods varies appreciably, often creating topographic barriers for the gravity conveyance of wastewater to the LOTT facility. To overcome these barriers, the Wastewater Utility operates 33 sewer lift stations and over 1,860 STEP systems that pump effluent from individual residences to a centralized collection system and ultimately to the LOTT facility. A number of privately-owned and operated grinder pumps provide a pressurized service connection to the City’s sewer collection system.


Winter weather in Olympia is temperate, wet and generally overcast. Summer weather is moderate and comparatively dry. The average annual range in temperature is relatively narrow, from an average low of 40 degrees (Fahrenheit) to an average high of 60 degrees. Monthly average low and high temperatures vary from 32-50 degrees and 44-77 degrees, respectively.

The average annual precipitation for Olympia is 51 inches. During the wet season, generally from October to May, storms usually arrive from the southwest and continue north into the Puget Sound area. Most precipitation occurs during November, December and January (averaging 8.2, 7.9 and 7.6 inches per month, respectively), with an occasional Arctic storm that brings freezing temperatures, hail or sleet, freezing rain or snow.

Water Supply

Olympia depends on springs/groundwater for its drinking water supply. About 70 percent of Olympia’s water comes from McAllister Springs, located about 10 miles east of the city. Water leaves McAllister Springs through a 36-inch transmission main and is pumped to the Meridian Storage Tanks less than a mile west of the springs. The water then flows by gravity from the storage tanks through the transmission main for an eight-mile journey to the storage tanks on Fir Street and 7th Avenue. From these storage tanks, the water is pumped and piped throughout the city.

The City also has five water supply wells. Three are on the west side of Olympia: two at Allison Springs and one on Kaiser Road. Two wells are in southeast Olympia: one on Hoffman Road and one at Shana Park, near the Indian Summer Golf Course.

As part of its long range planning for additional water supply and redundancy within the system, Olympia is developing the McAllister Wellfield (which recently received a water right from the Washington State Department of Ecology) and is planning to use an existing well at Indian Summer Golf Course, pending approval of a request to transfer water rights (City of Olympia, 2004). See the City’s 2009 Water System Plan for more information.

Some Wastewater Utility customers have their own water wells and therefore do not receive City water.

2.5 State and Federal Regulations

Wastewater Utility services are planned and implemented within a complex framework of statutes, regulations, plans and policies adopted by federal, State, County and City governments and intergovernmental agreements with neighboring jurisdictions. Below are brief discussions of the more important programs and regulations. Please click on the appropriate link for more information.

Clean Water Act and Department of Ecology

The federal Clean Water Act, 33 U.S.C. §1251 et seq. (1972), forms the basis of our regulatory standards regarding discharges of pollutants into surface waters. Additionally, the Safe Drinking Water Act, 42 U.S.C. §300f et seq. (1974), protects and regulates all potential sources of drinking water, both surface and groundwater.

The United States Environmental Protection Agency (EPA) is responsible for enforcing the provisions of both the Clean Water Act and Safe Drinking Water Act, through programs such as the National Pollutant Discharge Elimination System permit program, authority for which has been delegated to the Department of Ecology (Ecology) in Washington State. LOTT’s Budd Inlet Treatment Plant holds the current NPDES permit that covers the City’s wastewater collection system (see Appendix I). EPA has also delegated authority to Ecology for approval of wastewater plans and specifications. Washington Administrative Code (WAC) 173-240-050, Department of Ecology Requirements for General Sewer Plans, lists specific information that wastewater plans should address when submitting one to Ecology for approval (see Appendix A).

Under RCW 90.48.110(2), Ecology has delegated to the City of Olympia responsibility for review and approval of engineering reports, plans and specifications for new wastewater facilities within its Sewer Service Area. Engineering specifications for the use and construction of sewer infrastructure are provided in Ecology’s Criteria for Sewage Works Design.

Ecology has also authorized the City of Olympia to issue permits for discharge into the wastewater system (WAC 173-208). These are regulated under the Industrial Pretreatment Program jointly administered by LOTT under its NPDES permit and the City through OMC 13.20.

Growth Management Act

The City of Olympia is required by the Growth Management Act (RCW 90.48) to plan for 20 years of future growth. State-mandated growth management planning is designed to produce denser urban areas while protecting the rural character of unincorporated areas. Consistent with the GMA, the Wastewater Utility manages its infrastructure capacity to accommodate projected development within the City and its Urban Growth Area (UGA). Sewer extensions outside the UGA are normally not allowed under the GMA without a rigorous demonstration of a need to address an urgent public health threat.


SEPA, the State Environmental Policy Act (RCW 43.21C), requires the City to consider the potential environmental impacts of a proposal. Plans such as this one are considered non-project, or program, proposals and do not go through as rigorous an environmental review as do specific project proposals.

As a lead agency under SEPA, the City identifies the potential impacts of sewer service associated with proposed new development and measures to mitigate these impacts. See Appendix L for the SEPA review and determination for this Wastewater Management Plan.

Washington Department of Health

The Washington State Department of Health is this state’s regulatory authority for most issues related to drinking water. In addition, the Department of Health has authority for approving private sewage disposal systems (WAC 246-272), but has delegated the authority to approve all systems with a design flow of less than 3,500 gallons per day to the Thurston County Board of Health. Criteria for system approval include minimum lot size and setbacks from sources of drinking water or other water resources. See Chapter 4 for more information.

2.6 Local Regulations and Design Standards

Olympia Municipal Code

The Olympia Municipal Code (OMC) addresses wastewater issues in the following chapters and sections:


Sewer Capital Improvement Fund


Local Improvement Districts






Wastewater System (Pretreatment)


Subdivisions - Improvements


Developments which rely on onsite sewage systems

Other chapters of the OMC, for example those addressing Zoning and Building Codes in Chapters 16 and 18, also include regulations that directly or indirectly address issues related to providing sewer service.

Olympia Engineering Design and Development Standards

The City of Olympia’s design and development standards regarding wastewater infrastructure are contained in Chapter 7 of the Engineering Design and Development Standards (EDDS). The EDDS are updated every few years, at which time they address inconsistencies in language, new industry standards, input from local businesses and related professionals, and comments from local and state jurisdictions, private citizens and other stakeholders.

WAC 173-240, Submission of Plans and Reports for Construction of Wastewater Facilities, includes in subsection .040, Review Standards, a requirement that plans and reports be "reasonably consistent" with the Department of Ecology’s "Criteria for Sewage Works Design" manual. The City’s EDDS fulfills this requirement.

Article IV of the Sanitary Code for Thurston County

Article IV of the Sanitary Code for Thurston County includes "rules and regulation of the Thurston County Board of Health governing treatment and dispersal of sewage." Article IV protects public health through regulating the "location, design, installation, operation, maintenance, and monitoring of OSS..." through the authority granted in Chapter 70.05 RCW and 246-272A WAC. See Chapter 4 of this Plan for more information.

2.7 Related Plans

Following are a number of plans and guidance documents that relate directly or indirectly to the 2013 Wastewater Management Plan.

Olympia Comprehensive Plan

In addition to its sustainable community vision, the Comprehensive Plan makes commitments to the future through its goals and policies. Specific Wastewater Utility activities are guided by Comprehensive Plan goals and policies established in the Growth Management, Environment, Public Utilities and Services, and Public Education sections of the Comprehensive Plan.

Olympia Capital Facilities Plan

The City’s Capital Facilities Plan (CFP) is updated every year to reflect six and 20-year priorities for public infrastructure construction. Wastewater projects identified and prioritized by this Plan (see Chapter 10) are more fully defined, funded and implemented through the City’s Capital Facilities Planning and yearly budgeting processes.

Thurston County Sewerage General Plan

The 1990 Thurston County Sewerage General Plan for Unincorporated Urban Growth Management Area promotes the orderly growth of the urban area, addresses the ownership of sewers, timing of construction, and hookup and payment policies for the unincorporated Urban Growth Area (UGA).

This plan requires that areas within the short-term UGA (defined in the document) be developed on sewers or community onsite sewage systems, and specifies that areas within the long-term UGA (also defined in the document) need not be served by sewers at the time of construction. Since 1990, the short-and long-term UGAs have been combined into one UGA which, despite having somewhat different boundaries then those originally developed by 1990, is regulated under the previous policies for the short-term growth area. Under this approach, community onsite sewage systems are allowed in the UGA. In the long-term, sewer service is to be provided. Areas served by sewer and community systems are required to annex or sign a no-protest annexation agreement. The plan also defines circumstances under which sewer service can be extended to areas outside the UGA.

While the delineation between long-term and short-term urban growth areas is no longer in effect, the Thurston County General Sewerage Plan continues to guide some of the sewer policies relevant to development in the UGA, particularly when a development plan may include using a community onsite sewage system. Also see the 1992 General Sewerage Agreement for the Unincorporated Urban Growth Management Area.

Olympia 2009 Water System Plan

The City of Olympia delivers high quality drinking water to nearly 55,000 people through approximately 19,000 service connections. The 2009 Water System Plan presents both a 50-year vision and a six-year plan for efficiently using regional water resources to ensure safe and sustainable drinking water for the City’s growing needs.

The plan is used by City staff to accomplish goals around efficient use and protection of current water supplies to ensure future supplies, maintain a reliable water system infrastructure, and manage the Drinking Water Utility in a fiscally responsible manner. The Plan also highlights past accomplishments and current priorities.

Issues covered in the 2009 Water System Plan include actions to protect groundwater quality and promote water conservation, and an increased emphasis on utilizing reclaimed water.

Reclaimed water, addressed in Chapter 7 of the 2009 Water System Plan, is part of the Drinking Water Utility’s water conservation strategy to ensure regional water supplies are used efficiently. After the LOTT Budd Inlet Treatment Plant generates reclaimed water to Class A standards, the City purveys it to four Olympia customers, primarily for irrigation. The LOTT Clean Water Alliance is also actively pursuing groundwater infiltration of reclaimed water outside City limits. The City’s Reclaimed Water Program, begun around 2005, is implemented through Olympia Municipal Code (OMC) 13.24, state and City standards, and individual End User Service Agreements. Reclaimed water staff is also guided by a reclaimed water system expansion plan and procedures manual.

The Washington State Department of Health (DOH) requires the City to update its water system plan every six years. DOH must approve the plan for the City to be in compliance with water system planning requirements. The next update is scheduled for spring 2014.

1996 North Thurston County Coordinated Water System Plan

Thurston County oversees a planning process that coordinates and regulates water system services within the urban area of North Thurston County and designates Urban Water Supply Services Areas. Policies and recommendations contained in this 1996 document are intended to "encourage the effective coordination and development of water systems capable of meeting domestic and fire protection water requirements of the property owners and residents of the North Thurston urban area."

Olympia 2003 Storm & Surface Water Plan

The role of the City’s Storm and Surface Water Utility was bolstered in 1990 with the following mission:

To provide services that minimize flooding, maintain or improve water quality, and protect or enhance aquatic habitat. These services reflect community values, are efficient and cost-effective, and satisfy regulatory requirements and Olympia Comprehensive Plan goals and policies.

The 2003 Storm & Surface Water Plan and its 2010 refinements to goals and priorities guide the Utility’s action in regards to flooding, water quality and aquatic habitat management. Its illicit discharge detection and elimination (IDDE) program includes identifying sources of wastewater connected to the stormwater conveyance and discharge system, and eliminating them in coordination with the Wastewater Utility.

Sustainable Thurston

Currently being developed by the Thurston Regional Planning Council, Sustainable Thurston is intended to "create a vision for how the Thurston Region will look, function and feel over the next 20 - 30 years." By the end of 2013, it intends to have a Regional Plan for Sustainable Development, a Regional Housing Plan, and a Sustainable Economy Strategy.

While Sustainable Thurston is not a regulatory or state-mandated planning effort, its current effort explores many issues including the community’s water resources. The effort includes identifying challenges and opportunities related to water quality and onsite sewage systems, as well as sewer collection, treatment and disposal. Information being developed as part of this process is aiding implementation of several Wastewater Utility goals - for example, addressing basin-specific water quality issues, and sustainably expanding sewer service into areas within the City and its Urban Growth Area which are currently undeveloped or served by onsite sewage systems.

2.8 Governmental Agreements

A number of agreements are in place among the four local jurisdictions that make up the LOTT Clean Water Alliance. Below are brief summaries of some of the more important ones. See also Appendix Q for a more complete list of active agreements related to the Wastewater Utility.

1992 Agreement for the Implementation of the Thurston County Sewerage General Plan for the Unincorporated Urban Growth Management Area

This agreement serves as the means to implement the 1990 Thurston County Sewerage General Plan. It clarifies ownership and payment policies, procedures and responsibilities for sewers and community onsite systems. The agreement anticipated "eventual interception of individual and community onsite systems" within the Urban Growth Area (UGA) by gradually constructing regional pipe systems and connecting residences. Key provisions of the agreement are:

• Establishing that Olympia, Lacey and Tumwater are the primary providers of sewers and other utilities in their urban growth areas, with authority to establish policies and development standards applicable to the unincorporated County within their UGA.

• Procedures for the joint review and annexation of development projects within the UGA.

• Agreement by the three cities to own and operate community systems, including community onsite sewage systems and STEPS, within their service areas. This provision ensures consistent wastewater services to all customers as mandated by the Growth Management Act. The agreement establishes the requirements under which the cities will accept responsibility for community systems and will serve as the permit holder for these systems.

1999 Interlocal Cooperation Act Agreement for Wastewater Management

The Interlocal Cooperation Act Agreement for Wastewater Management by the LOTT Wastewater Alliance (now LOTT Clean Water Alliance) was executed on November 5, 1999 and adopted by ordinance January 24, 2000. This agreement provided for a new governance structure to carry out the regional Wastewater Resource Management Plan and set the stage for consolidation of the ownership and management of all joint facilities under the management and control of a new LOTT organization. It superseded the 1976 agreement establishing the LOTT Partnership, under which ownership and operation of the joint facilities was handled by Olympia. The new facilities implemented pursuant to this agreement, together with those developed as joint facilities under the 1976 agreement, are operated for the benefit of all Partners.

Besides describing how LOTT is managed, the agreement addresses a number of issues, including flow reduction goals, pretreatment requirements, and allocation of costs.

Wastewater flows from the three local municipalities are piped to LOTT treatment facilities for treatment, re-use and /or discharge to receiving waters. All of Olympia’s wastewater flows are treated by LOTT’s Budd Inlet facility in downtown Olympia.

The Budd Inlet facility provides tertiary treatment including denitrification. Long-range planning for upgrades and expansions seeks to complete projects incrementally as needed by growing populations. LOTT is overseen by an elected-official Board and a technical support committee. At a staff level, projects and programs are well-coordinated with the local jurisdictions including Thurston County. More information on LOTT is provided in Chapter 3.

Intergovernmental Contract for Inflow and Infiltration Management and New Capacity Planning

This contract, executed in 1995 and updated in 1999, outlines a strategy for Olympia to first reduce, then limit, the amount of infiltration and inflow (I&I) entering the collection system, with financial participation from LOTT. I&I from groundwater and stormwater unnecessarily consume pipe and treatment plant capacity. The contract is included as Exhibit J of the 1999 Interlocal Cooperation Act Agreement establishing the LOTT Alliance described above.

Agreement Regarding Joint Wastewater Flow Reduction and Water Conservation

The Interlocal Cooperation Agreement between Thurston County and the Cities of Lacey, Olympia and Tumwater Regarding Joint Wastewater Flow Reduction and Water Conservation Projects was executed in October 2006 for the years 2007 to 2012, and extended through the year 2013 in December 2012. It defines the arrangements for joint management of flow reduction, especially water conservation projects at area schools. This agreement is included as Exhibit K of the 1999 Interlocal Cooperation Act Agreement establishing the LOTT Alliance described above.