Cowlitz County, WA Environmental Rules: Stormwater Management (2026)
Key Facts
- Applies to
- Development adding 12,000+ sq ft impervious area
- Threshold
- Impervious area equal to 15% or more of parcel
- Large developments
- Over 1 acre impervious triggers CCC § 16.20.070
- Area covered
- Unincorporated rural area outside urbanized boundary
- Enforcement
- Civil infraction, or lien for county-performed repairs
Summary
New development in the unincorporated, non-urbanized area of Cowlitz County that adds 12,000 square feet or more of impervious surface, equal to at least 15 percent of the parcel, must control stormwater runoff under CCC Chapter 16.20, with violations enforceable as a civil infraction.
Ensure that property owners control the volume and rate of stormwater runoff originating from their property so that adjacent and downstream property and property owners' rights are protected, soil erosion minimized, off-site sedimentation prevented and flooding potential reduced; ... The provisions of this chapter shall apply to development that: ... Creates an additional 12,000 square feet or more of impervious area outside of the unincorporated urbanized area; and ... The additional impervious area is equal to 15 percent or more of the parcel, or sum total of the parcels impacted, area. ... It shall be unlawful to violate any provision or fail to comply with any of the requirements of this chapter. ... Violation of any provision of this chapter shall be deemed a nuisance in RCW 36.32.120(11) and may be cited as a civil infraction or referred to the prosecuting attorney for appropriate legal action as specified in this section and in Chapter 2.06 CCC.
Full Breakdown
22 CCC, covers the unincorporated urbanized area). 010 states the purpose is to ensure property owners control the volume and rate of stormwater runoff from their property so that adjacent and downstream property and property owners' rights are protected, soil erosion is minimized, off-site sedimentation is prevented, and flooding potential is reduced, while also preventing accelerated erosion and sedimentation and protecting the county's municipal and downstream stormwater facilities. 070. Development activities on a parcel occurring within a year of each other count as the same project for these thresholds.
Compliance requires following the county's stormwater drainage manual and the state Stormwater Management Manual for Western Washington, and is treated as a minimum standard; other permits from local, state, or federal agencies may still be required. 06 CCC, with the county able to order installation, maintenance, or repair of stormwater facilities, cessation of violating discharges, and remediation of contamination.
Violations & Fines
Failing to meet Chapter 16.20 CCC's stormwater standards is unlawful under CCC § 16.20.100 and can be cited as a civil infraction or referred to the prosecuting attorney under Chapter 2.06 CCC. The county can order compliance measures such as installing or repairing stormwater facilities, and if it makes emergency repairs itself, the cost plus any penalties incurred becomes a lien on the property.
Frequently Asked Questions
Does building a new driveway or shop trigger Cowlitz County's stormwater rules?
What's the goal of the county's stormwater management chapter?
What happens if I don't comply with a stormwater order from the county?
Sources & Official References
Other rules in Cowlitz County
Compare Cowlitz County to another location·View the Washington environmental rules overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.