Solano County, CA Environmental Rules: Erosion Control (2026)

Under Solano County Code Section 31-20, no one may change land topography, fill or divert a drainage channel, or grade, fill, excavate or clear vegetation without first obtaining a grading and drainage permit from the Department of Resource Management. A separate permit covers each site, and emergency work protecting life or public property may begin before permitting only if the County is notified the next business day and an application follows within ten days. Section 31-16 fixes the construction season from April 15 through October 15; work outside that window needs the Director's written approval, since Section 31-30(c) requires soil exposure to be stabilized and revegetated by season's end.

Small projects can qualify for exemptions under Section 31-22, such as excavations moving fewer than fifty cubic yards on less than 8,000 square feet, or home gardening disturbing under 10,000 square feet, but only if Section 31-21's conditions are met: the work must not increase erosion, sedimentation or runoff, impair an offsite watercourse, or create a nuisance. Larger jobs need either a minor permit (under one acre disturbed, under 1,000 cubic yards moved, no steep or unstable slopes) or a major permit requiring an engineered erosion, sediment and runoff control plan prepared and sealed by a registered civil engineer, per Sections 31-23 through 31-26.

Section 31-30 lists the mandatory design standards: cut and fill slopes cannot exceed 2:1 without an engineering analysis justifying a steeper slope, sediment basins and diversions must be installed before any clearing begins, and runoff from more than 5,000 square feet of new impervious surface must be treated with biofiltration before leaving the site or entering state or federal waters. Work inside the Suisun Marsh watershed faces added restrictions under Section 31-20(c): a marsh development permit is required first, and vegetation removal, new structures, and channel filling within 25 feet of a protected channel bank are unlawful without a permit, with limited agricultural and habitat-management exceptions. Section 31-42 obligates the permit holder to keep erosion controls in place for at least one year after work is finished or until the Director confirms the site is stabilized.