Thurston County, WA Landscaping Rules: Rainwater Harvesting (2026)
Key Facts
- Base rate reduction
- 10% for qualifying commercial buildings
- Bonus reduction
- Extra 10% for over 90% roof capture used internally
- Qualifying threshold
- System captures rainwater from over 85% of roof
- Annual requirement
- Inspection report filed by July 1st
- Governing chapter
- Storm and Surface Water Utility Rates, Ch. 15.06
Summary
Thurston County doesn't mandate rainwater harvesting, but it rewards it. TCC § 15.06.020 defines rainwater harvesting as collecting roof runoff for uses like landscape irrigation or toilet flushing, and § 15.06.040(E) cuts a qualifying commercial building's stormwater utility rate by 10%, with an additional 10% if the system captures runoff from over 90% of the roof.
"Rainwater harvesting" means the collection, storage and use of rainwater from the roof as a non-potable water source for a building. The uses may include landscape irrigation, toilet flushing or other uses approved by the appropriate permitting authority. ... E.Rainwater Harvesting Rate Reduction.1.For qualifying commercial buildings, the rates and charges set by subsections A and B of this section shall be reduced by ten percent. When qualifying buildings harvest rainwater from greater than ninety percent of the roof area and use the harvested rainwater as a portion of the building's internal water supplies, the rates and charges set by subsections A and B of this section shall be reduced by an additional ten percent.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 77).
Full Breakdown
Thurston County's rainwater harvesting rules live in the stormwater and surface water utility rate chapter, not a standalone environmental mandate. 020 defines 'rainwater harvesting' as collecting, storing and using roof rainwater as a non-potable water source, for uses including landscape irrigation, toilet flushing, or other uses the permitting authority approves. To earn the rate reduction, a building must first be a 'qualifying commercial/industrial building' under the same section: new or remodeled construction specifically designed and engineer-approved to use rainwater harvesting as an integral part of its water management, capturing rainwater from more than 85% of the total roof area.
040(E)(1) recognizes a building as qualifying, its stormwater rates and charges under subsections A and B are cut by 10%. If the system harvests from more than 90% of the roof and uses that water as part of the building's internal water supply, the county stacks on a second 10% reduction, for up to 20% off the base stormwater charge. 040(E)(2). The design engineer must also certify the building was built or remodeled to the approved design, and performance is evaluated and adjusted within the first two years of operation to meet the stormwater runoff goal.
Violations & Fines
There's no fine for skipping rainwater harvesting since it's a voluntary rate incentive, not a mandate. But a qualifying building that fails to file its required annual inspection report with the storm and surface water utility by July 1st of the preceding year loses eligibility for the rate reduction after its second year of operation, under § 15.06.040(E)(2). Billing disputes over eligibility go through the rate adjustment and appeal process in § 15.06.060.
Frequently Asked Questions
Does Thurston County require rainwater harvesting?
How big a discount does rainwater harvesting earn?
What makes a building 'qualifying' for the rainwater harvesting rate cut?
Can the county take away the rate reduction later?
Sources & Official References
Other rules in Thurston County
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