Environmental Rules in Franklin County, WA (2026)
5 rules for unincorporated Franklin County, Washington.
Verified from official government sources
Stormwater Management
In unincorporated Franklin County, all storm drainage generated by new development must stay on the site. Franklin County Code Section 17.72.060 requires builders to control runoff with drainage swales, dry wells, French drains, or another method the county engineer approves, rather than letting water leave the property onto neighboring land or public roads.
Franklin County Site Drainage Retention Standard
Some RestrictionsFranklin County Code § 17.72.060
All storm drainage shall be retained on-site and controlled by way of drainage swales, dry wells, french drains or other means as approved by the county engineer.
Erosion Control
Unincorporated Franklin County has no stand-alone grading and erosion ordinance; erosion control comes through SEPA environmental review. Franklin County Code Section 18.04.260(D)(4)(b) lets the county require dust abatement, wind erosion control, and site restoration whenever grading or excavation is part of a proposal, and the county can attach that requirement as a written condition on the permit itself.
Franklin County SEPA Erosion Control Policy
Some RestrictionsFranklin County Code § 18.04.260(D)(4)(b)
4.The county establishes the following additional policies:a.Require land development to include appropriate measures to prevent air pollution and deterioration of ambient air quality;b.Require land development where necessary to employ dust abatement, wind erosion and/or site restoration methods where construction or subsequent operations involve grading or excavation activities; ... d.Require...
Flood Zones
Building or altering anything within a mapped special flood hazard area in unincorporated Franklin County requires a development permit first. The county building official, acting as floodplain administrator, reviews the application; building without one is a misdemeanor punishable by a fine and jail time.
Franklin County Floodplain Development Permit
Some RestrictionsFranklin County Code §§ 15.08.080, 15.08.130
1.All development within special flood hazard areas is subject to the terms of this chapter and other applicable regulations. ... Violations of the provisions of this chapter by failure to comply with any of its requirements (including violations of conditions and safeguards established in connection with conditions), shall constitute a misdemeanor. Any person who violates this chapter or fails...
Defensible Space
Where a proposed home in unincorporated Franklin County sits more than 500 feet from a working fire hydrant or approved suppression system, Franklin County Code § 8.40.080 requires 25-foot front and rear setbacks, a 20-foot side setback, and 15 feet between structures, or 20,000 gallons of on-site water storage instead.
Franklin County Fire-Flow Setback Requirement
Some RestrictionsFranklin County Code § 8.40.080
A.Standardized On-Site Water Storage.1.Where year round, on-site water storage is required (as determined by building occupancy classifications) in accordance with this code, a minimum of twenty thousand (20,000) gallons shall be provided. ... 2.If no fire suppression system, as described in Section 8.40.080(A)(1), or no approved, working fire hydrant is located within five hundred (500) feet o...
Flood Elevation Requirements
New and substantially improved homes in Franklin County's mapped flood zones must sit at least one foot above base flood elevation where a BFE is set, or two feet above the highest adjacent grade where it isn't. Mechanical equipment must clear the same one-foot freeboard.
Franklin County Flood Elevation Freeboard Rule
Some RestrictionsFranklin County Code § 15.08.250
A.Residential Construction:1.In AE and A1-30 zones or other A zoned areas where the BFE has been determined or can be reasonably obtained, new construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot or more above base flood elevation. Mechanical equipment and utilities shall be waterproof or elevated least one foot...
All Franklin County ordinances
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