Clark County adopts amendments to on‑site sewage code to align with new state septic rules

The Clark County Board of Health on March 26 adopted Ordinance 20250312, amending Clark County Code 24.17 (on‑site sewage systems and regulation) to align local rules with updated Washington state on‑site septic regulations that take effect April 1, 2025.

The changes are intended to make county rules “consistent with or at least as stringent as the state code for septic rules,” Chuck Harmon, program manager for on‑site septic programs at Clark County Public Health, told the board during a public hearing. Harmon said the state has worked on the rule changes for five to six years and that counties must be consistent with the new state standards.

The updates address several areas of practical effect for property development and septic system management. They increase minimum lot‑area requirements for new development served by septic — by roughly 500 to 1,000 square feet depending on soil conditions — and explicitly require space for both a primary system and a future replacement drain field. County staff said the lot‑size standard varies by soil type and water supply: in poor soils or where private water supplies are used, required areas can be substantially larger; under an alternative sizing methodology the smallest lots could be about 12,500 square feet, and in the worst soils sizing could approach two acres.

Harmon and Miles Lawson, interim permitting manager for the on‑site program, told the board that the code preserves an exemption for existing legal lots of record created under earlier rules. “There’s an exemption for existing legal lots of record that were created before the current set of standards,” Lawson said; the new minimums primarily apply to the creation of new lots such as subdivisions and short plats.

The ordinance also clarifies repair and remediation rules. The code continues to require the least‑expensive repair or replacement that meets rules and sets timeframes to remedy unpermitted sewage discharges. The state rule updates add remediation options for failed drain fields on small lots, and they require field testing to verify performance of proprietary nitrogen‑ or disinfection‑treating components before those systems are broadly approved. Harmon said the state conducts the approvals for proprietary treatment technologies and that counties may receive local applications as part of state testing programs.

County staff said the changes include new language to ensure usable area is counted for lot sizing (excluding wetlands or permanently unusable land), and they reaffirm county practice of certifying pumpers, inspectors and installers at the local level while designers and engineers remain licensed by the state. Harmon said local code allows some homeowner self‑inspection programs, but last cycle the county intentionally limited homeowner self‑installation because of problems seen previously.

Several councilors asked how the new lot sizes would affect development in urban growth areas and whether the change would force more connections to sewer. Lawson said the county development code requires connection where sewer is available and that the increased minimums mainly affect new rural subdivisions; he added that for like‑for‑like repairs on failed septic systems, if the replacement cost is less than half the cost to connect to sewer, the county allows replacement rather than forced connection. Councilors pressed staff for more detail about the nitrogen‑reducing treatment and potential homeowner costs; Harmon said nitrogen‑reducing proprietary systems approved by the state must meet an NSF standard (roughly a 50% nitrogen reduction benchmark) and that costs vary a great deal by site and technology — ranging from lower‑cost gravity systems ($5,000–$10,000) up to higher‑treatment systems that can run in the tens of thousands of dollars depending on circumstances.

Public commenters during the hearing expressed broader concerns about growth, water quality and contaminants. One online commenter, Kimberly Goheen, said, “We are polluting the hell out of our earth,” and urged greater local transparency on water pollution. Another speaker, Wynn Gersich, urged attention to hazardous wastes and long‑term contaminants entering water and soil.

Action: Council moved and passed Ordinance 20250312 by roll call vote. Council recorded aye votes from Councilor Young, Councilor Belcott, Councilor Fuentes, Councilor Little and Chair Marshall (5–0). The ordinance number in the meeting packet is 20250312. The consent minutes (02/19/2025) were also approved earlier on the consent agenda.

Why it matters: The state rule changes become effective April 1, 2025; county staff said adopting the local amendments now prevents a gap between state and local standards and clarifies requirements developers, designers and homeowners must meet when building or repairing on‑site systems.

The county declined to set an immediate effective date for every local administrative step in the hearing; staff said additional implementation guidance and permit procedures will follow and that they will continue outreach with the on‑site septic industry and a technical advisory committee.