Environmental Rules in Benton County, OR (2026)
5 rules for unincorporated Benton County, Oregon.
Verified from official government sources
Stormwater Management
Any new development or redevelopment in unincorporated Benton County that creates or replaces a quarter acre (10,890 square feet) or more of impervious surface needs a Post-Construction Stormwater Permit under BCC § 99.670 before ground-disturbing work starts. The permit requires the property owner to design stormwater detention and treatment to the county's Stormwater Support Documents and sign a long-term maintenance agreement, and smaller projects on the same property count toward that threshold cumulatively.
Benton County Post-Construction Stormwater Permit
Significant RestrictionsBenton County Code § 99.670
(1)Purpose. Establish stormwater management requirements and controls to protect and safeguard the health, safety, welfare, financial investment in public and private infrastructure, and private property value, and minimize flooding and sedimentation in areas where structural and non-structural stormwater management is required to improve water quality and manage post construction runoff from n...
Erosion Control
Construction that disturbs soil in unincorporated Benton County falls under the county's illicit-discharge ordinance: BCC § 36.215 requires anyone covered by an NPDES stormwater permit or the county's own Erosion and Sediment Control Permit to comply with all its terms before the site can discharge to the stormwater system, and Public Works or Community Development can demand proof.
Benton County Erosion Control Permit for Construction
Some RestrictionsBenton County Code §§ 36.100(4), 36.215
(4)"Construction Activity" means activities subject to the Oregon Phase II Municipal Stormwater Program or NPDES General Construction Permits or Benton County Erosion and Sediment Control Permit requirements. ... Any person subject to any NPDES stormwater discharge permit or Benton County Erosion and Sediment Control Permit shall comply with all provisions of such permit. Proof of compliance wi...
Flood Zones
Any construction, substantial improvement, manufactured dwelling placement, or grading within a Benton County special flood hazard area requires a floodplain development permit under BCC 83.250 before work begins. New or expanded commercial, industrial, and other non-residential structures are flatly prohibited within the floodplain unless no buildable land exists outside it, and code violations carry fines of $500 per occurrence, $1,000 if continuing.
Floodplain Development Permit Rules in Benton County
Significant RestrictionsBenton County Code §§ 31.125(3), 83.250(1), 83.610(1)
(3)In addition to any other remedy provided by law to the County, the County may seek a fine of $500 for each separate violation and a fine of $1,000 for a continuing violation of any County ordinance, pursuant to this ordinance. ... (1)A floodplain development permit shall be obtained prior to construction of a new structure, substantial improvement to any structure, the placement of a manufac...
Defensible Space
Every new structure in unincorporated Benton County's Forest Conservation Zone must carry a defensible-space clearing around it. BCC 51.020(17) defines a "fire break" as a minimum 30-foot area cleared of vegetation, widened to 50 feet on slopes over 30%, and BCC 60.405(1) requires the owner to maintain a primary and secondary fuel-free fire-break around the structure, following Oregon Department of Forestry siting standards.
Benton County Defensible Space Fire Break Rule
Some RestrictionsBenton County Code §§ 51.020(17), 60.405(1)
(17)"Fire Break" means a minimum area of 30 feet around a dwelling cleared of vegetation except for ornamental shrubbery, sod, single trees or similar plants used for ground cover. Trees and large ground cover shall be placed to prevent rapid movement of a fire. If slopes are greater than 30%, "fire break" means a minimum of 50 feet. ... (1)The owner of any new structure shall maintain a primar...
Flood Elevation Requirements
Unincorporated Benton County requires the lowest floor of new or substantially improved residential structures in a special flood hazard area to sit at least 18 inches above the Base Flood Elevation (BFE), the height of base-flood waters expressed in feet above mean sea level. Critical facilities such as schools and fire stations must clear the BFE by a full 3 feet, or the 500-year flood height, whichever is higher.
Base Flood Elevation Freeboard Rules in Benton County
Some RestrictionsBenton County Code §§ 51.020(5), 83.500(3), 83.620(1)
(5)"Base Flood Elevation" means the height of the flood waters during a base flood at points along the water course, expressed in feet above mean sea level. ... Critical facilities constructed within the SFHA shall have the lowest floor elevated 3 feet above the Base Flood Elevation (BFE) or to the height of the 500-year flood, whichever is higher. ... (1)Where allowed, new construction, conver...
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