Bothell, WA Environmental Rules: Stormwater Management (2026)

Bothell Municipal Code § 18.04.040 requires a permit before any additions, betterments or extensions to the existing storm drainage system. Four permits apply: a right-of-way invasion permit for work in the street right-of-way or a public easement, a storm drainage side sewer permit for any side sewer or on-site storm drainage system, a grading permit whenever grading is performed, and a utility permit for infrastructure improvements with storm water revisions not covered by the other three. BMC 18.04.020 states the purpose: preventing siltation of the city's creeks, streams, rivers and lakes, and protecting adjacent owners from increased runoff that could cause flooding and erosion.

BMC 18.04.070 requires every applicant for a development permit to submit a drainage plan under the Bothell Standards. The exceptions are administrative interpretations, sign, street vacation, street use, hydrant use, plumbing, electrical, mechanical, sewer connection and water meter permits, and interior alterations with no change of use. Under BMC 18.04.080 new work must follow the storm drainage comprehensive plan, KCSWDM and the Bothell Standards, with the fee set by resolution. BMC 18.04.290 places all real property within the city limits inside the city's municipal separate storm sewer system.

Maintenance falls on the owner. BMC 18.04.270 makes the property owner responsible, at the owner's expense, for private storm water and drainage systems, requires facilities to be cleaned at least annually, and subjects them to annual inspection by the director. An order to maintain must be answered within 30 calendar days and becomes final after 30 calendar days unless appealed to the director. BMC 18.04.260 bans discharging anything other than storm water into the storm drain system, including silt, sediment, concrete, cement and gravel, and bars discharge water more than five degrees Fahrenheit warmer than the receiving water.