Basics
- Puget Sound Indicator Name
- On-site sewage system compliance
- Progress Indicator
- Each Unit (count)
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- Topics
- On-site Sewage Systems
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Laura Vary
- Contributing Partners
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- Last Updated
- 07/17/2025 15:30:01
Map
Description
This indicator measures the number of small on-site sewage systems compliant with state and local inspection schedules. Compliant OSS that are routinely inspected ensure the system is used and operating as designed. These OSS do not pose a risk to human or environmental health and will not impact nearby water quality and shellfish beds. This indicator helps us evaluate trends in the number of OSS that are compliant with state and local inspection requirements.
Progress Indicator Chart
Figure 1. Number of on-site sewage systems compliant with state and local routine inspection requirements (blue column sections) and non-compliant OSS (white column sections) across Puget Sound local health jurisdictions (LHJs) and marine recovery and sensitive areas in June and December of 2024.
In Puget Sound, fecal pollution impacts water quality, harvestability and food safety of shellfish, and can cause public health concerns in swimming areas. On-site sewage systems (OSS) treat wastewater close to where it is generated and many properties across Puget Sound are supported by this essential wastewater infrastructure[1]. However, improper management of OSS can lead to environmental and public health concerns; failing OSS are a leading pressure impacting water quality and shellfish bed health in Puget Sound[2].
State code requires owners to have OSS inspected on a routine basis depending on design type: for gravity systems, inspections must occur at least every three years whereas OSS that are not gravity (“alternative” systems) must be inspected every year[1]. Local regulations may require more frequent inspections. The responsibility to manage these systems appropriately is split between homeowners and local health jurisdictions (LHJs). While homeowners must ensure proper use and care of OSS, LHJs must support homeowners by establishing programs that offer education, training, rebates, and technical assistance to ensure proper OSS management[1].
Despite these requirements and local assistance options, compliance with OSS management best practices varies across the region. Inspections can be difficult to schedule and if problems are identified, such problems can be costly to correct. OSS are also often falsely perceived as simple, static systems that require less care despite being complex, albeit small-scale, wastewater facilities[1]. LHJs are also often limited by budget and staff capacity, impacting their ability to provide essential services to homeowners.
This indicator measures the number of OSS that are compliant with their state and local inspection schedules; they receive regular inspections based on their system type to identify problems and ensure proper operation. The indicator helps us understand trends in OSS compliance which can help identify issues before systems have the potential to cause negative environmental and public health impacts.
[1] Schneider, L., Glasoe, S., Story, C., Hofstad, L., Thomas, J., Washington State Department of Health, Skagit County Health, BH Consulting, & Washington On-Site Sewage Association. (2016). Puget Sound Septic System Management Programs Best Management Practices Reference Manual. https://doh.wa.gov/sites/default/files/legacy/Documents/Pubs/332-166.pdf
[2] Shellfish Beds Interdisciplinary Team, Puget Sound Partnership, Washington State Department of Health. (2023). Shellfish Beds Implementation Strategy: Protect and Restore Shellfish Beds in Puget Sound. https://pspwa.box.com/s/d3u2rf092imo9pt4foqgrw3m6p6rj9yv
Key Progress Indicator Results
At the end of the baseline period (2024), 145,695 OSS were compliant with state and local inspection schedules (26 percent).
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In June of 2024, there were 511,427 known OSS across the Puget Sound region. Of these, 108,072 systems (21 percent of known systems) were compliant with their state and local inspection mandates.
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By December of 2024, the total known OSS increased to 550,417 systems and percent compliance increased to 26 percent of known systems.
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Percent compliance in both June and December of 2024 was higher in marine recovery and sensitive areas. In June of 2024, 22,691 systems were compliant (36 percent of known systems in these areas). By December of 2024, 42,062 systems were compliant (49 percent of known systems in these areas).
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In December of 2024, most compliant systems across local health jurisdictions were also permitted. 8,732 systems were not permitted but were compliant with their state and local inspection mandates.
Methods
- Monitoring Program
Puget Sound local health jurisdictions with on-site sewage system management areas.
- Data Source
Compilation of Puget Sound local health jurisdiction data which are submitted to Washington DOH biannually.
This Progress Indicator tracks the number of on-site sewage systems (OSS) that have been inspected within the required state and local inspection schedules and are therefore “compliant” in each Puget Sound local health jurisdiction (LHJ).
LHJs in the Puget Sound region are required by Chapter 246-272A-0015 of the Washington Administrative Code (WAC) to establish local management plans describing how they will maintain inventories, identify areas where OSS can pose a risk, assess operations and maintenance requirements for areas at risk, provide homeowner outreach, and operate operations and maintenance (O&M) programs.
O&M programs collect data on OSS and inspections to protect public health and Puget Sound water quality[1]. Data management processes vary across LHJs, including practices to track system compliance across Puget Sound. This indicator relies on LHJ staff to identify the number of OSS inspected according to required schedules.
Data are collected by LHJ practitioners and submitted via survey reporting form to the Washington State Department of Health (DOH) on-site sewage management program on a biannual basis. Data are then transferred from DOH to Puget Sound Partnership (Partnership), where Partnership staff manually review LHJ entries for anomalies and confirm values with DOH and LHJ staff as warranted. Data are collected at the county scale, though system compliance within marine recovery areas and sensitive areas (sub-areas within counties that have enhanced management requirements) are also provided in this report.
Compliant systems include both permitted and unpermitted systems. Some systems are older than Washington state permit requirements and thus are not necessarily required to have a permit on file. This definition of compliance is consistent with regional LHJ practices. To calculate this indicator, the number of permitted, inspected systems is added to the number of unpermitted inspected systems.
LHJ biannual reports illustrate a snapshot of OSS data at the time of reporting. This means that OSS may be double counted if multiple reports are summed together. We avoid this by reporting numbers attached to specific report submittal dates and by reporting net change over time.
Current reporting period: 2024
Baseline period: 2024
Each reporting period for this indicator is one calendar year; each calendar year includes two biannual reports submitted by LHJs covering January through June and July through December, respectively. We will evaluate trends over time by comparing the regional indicator value of the most recent reporting period (one year) to the regional value of the baseline period (2024). 2024 is selected as the baseline period because it is the first year for which LHJs reviewed local methods and implemented widespread updates to their data systems.
Limitations:
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Data comprehensiveness and quality varies by LHJ, depending on available resources. LHJs are often understaffed and under-resourced, which can impact their ability to comprehensively assess the inspection status of OSS, both within marine recovery and sensitive areas and across their full county. Beginning in 2022, LHJs completed a significant effort to update databases and data systems to provide the data reported here. Most database updates are still in progress as of July 2025, and staff continue to work with technology staff to develop workflows that allow them to query this data accurately. Dedicated and sustained funding to LHJs can help improve the quality and comprehensiveness of local data.
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Data are currently non-spatial. This impacts our ability to understand the relationship between water quality and OSS management. We can note which OSS are in marine recovery or sensitive areas, but not specific locations therein. Improving the spatial data capabilities of LHJs is a regional priority.
[1] Chapter 246-272A WAC: (n.d.). https://app.leg.wa.gov/wac/default.aspx?cite=246-272A&full=true
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- Critical Definitions
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On-site sewage system (OSS): Integrated system of components, located on or near the property it serves, that stores, treats, and manages the dispersal of sewage[1].
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Small OSS: OSS with daily flows less than 3,500 gallons per day[2].
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Inspection frequency: Washington state law requires OSS inspections at least every three years for conventional (gravity) systems and at least annually for advanced systems. Some local health jurisdictions may adopt more stringent inspection schedules (e.g., at least annually for all system types)[3].
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Compliance: OSS are compliant when associated LHJs have record of an inspection on file within Washington state and local inspection frequency mandates. An OSS can be compliant even if it does not have a permit on record.
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Gravity systems: a common type of OSS consisting of a septic tank, drainfield, and soil beneath the drainfield[4].
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Alternative systems: any OSS with designs different from gravity systems, including pressure distribution systems, mound systems, sand filter systems, aerobic treatment units, BioFilters, etc[4].
[1] Chapter 246-272A WAC: (n.d.). https://app.leg.wa.gov/wac/default.aspx?cite=246-272A&full=true
[2] Washington State Department of Health, (n.d.). On-site Sewage Systems (OSS). Wastewater Management, Department of Health, State of Washington. Accessed at https://doh.wa.gov/community-and-environment/wastewater-management/site-sewage-systems-oss#:~:text=Small%20on-site%20sewage%20systems%2C%20also%20known%20as%20septic,flows%20of%20less%20than%203%2C500%20gallons%20per%20day.
[3] Schneider, L., Glasoe, S., Story, C., Hofstad, L., Thomas, J., Washington State Department of Health, Skagit County Health, BH Consulting, & Washington On-Site Sewage Association. (2016). Puget Sound Septic System Management Programs Best Management Practices Reference Manual. https://doh.wa.gov/sites/default/files/legacy/Documents/Pubs/332-166.pdf
[4] Washington State Department of Health. (n.d.). Types of septic systems. https://doh.wa.gov/community-and-environment/wastewater-management/septic-system/types-systems.
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Interpretation of Results
This Progress Indicator report represents the first year for which we have improved data on OSS management. We thus apply the “Limited Data” designation to this indicator and will address indicator trends over time as we compile additional years of data.
Over the baseline period (2024), compliance in marine recovery and sensitive areas was higher compared to local health jurisdiction (LHJ) totals (Figure 2).
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In June of 2024, 36 percent of systems (22,691 systems) were compliant in marine recovery and sensitive areas whereas 21 percent of systems (108,072 systems) were compliant across wider LHJs.
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By December of 2024, 49 percent of systems (86,425 systems) were compliant in marine recovery and sensitive areas whereas 26 percent of systems (145,695 systems) were compliant across wider LHJs.
Figure 2. Total compliant and non-compliant systems as a percentage across Puget Sound local health jurisdictions and marine recovery and sensitive areas in June and December of 2024.
System compliance at the end of the baseline period (2024) varied by LHJ (Figure 3.A.). Most LHJs had higher percent compliance in marine recovery and sensitive areas (Figure 3.B).
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Skagit county, with 21,046 systems, had the highest percent compliance at 63 percent at the end of 2024. Snohomish county, with 80,739 systems, had the lowest percent compliance at 3 percent at the end of 2024 (Figure 3.A).
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Pierce county’s marine recovery and sensitive areas, with 12,734 systems, had the highest percent compliance at 86 percent at the end of 2024. Jefferson county, with 4,128 systems, had the lowest percent compliance at 19 percent at the end of 2024 (Figure 3.B).
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At the end of 2024, percent compliance across full LHJs averaged 30 percent whereas percent compliance averaged 58 percent in marine recovery and sensitive areas.
Figure 3. A) Compliant systems (blue column sections) and non-compliant systems (white column sections), and percent compliance across local health jurisdictions at the end of 2024. B) Compliant systems (blue column sections) and non-compliant systems (white column sections), and percent compliance across marine recovery and sensitive areas at the end of 2024.
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Puget Sound local health jurisdictions (LHJs) dedicate significant time and resources to assisting homeowners with proper OSS management. However, the landscape of OSS management is complex, authority for enforcement varies, and homeowner awareness of best practices varies.
Trends in this indicator are thus affected by:
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Dedicated and sustained funding for LHJs to educate homeowners, offer incentives and financial assistance, determine compliance, manage compliance data, and implement enforcement activities,
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Technical capacity and suitable software for LHJs to monitor compliance,
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Capacity for LHJs to support homeowners navigating permitting and inspection processes,
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Homeowner awareness of their OSS needs, changes to OSS state codes, and willingness to comply with mandated management practices, and
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Consistent enforcement of inspection requirements.
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Overview of OSS and homeowner resources, Department of Health (DOH)
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Septic system basics, DOH
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On-site sewage systems, Washington Administrative Code Chapter 246-272A
Datasets
No datasets uploaded.
Reporting Guidance
- Reporting Instructions
Subcategories
| Name | |
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| Area |
Local Health Jurisdictions, Marine Recovery and Sensitive Areas
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| Metrics |
Total Known, Total Compliant, Percent Compliant
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| Month |
June, December
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