The Process
Each property is different, but the work generally moves through three phases. Environmental review comes first when critical areas may affect the site, followed by septic design and then construction.
Three Project Phases
The exact requirements vary by property. MKPE provides a clear proposal for the services and fees that apply before each phase begins.
Review the property, development goals, records, soils, water source, access, and mapped constraints. If critical areas may affect the project, the environmental and PDS process is completed before the final septic design is submitted.
MKPE develops the final on-site sewage system (OSS) design around the established site constraints and submits it to the Snohomish County Health Department. A well-site application can be submitted at the same time when needed.
After approval and permit issuance, a certified installer constructs the system. MKPE reviews the work, prepares the as-built record, and coordinates final Health Department inspection.
Phase 1 — Feasibility & Site Constraints
Wetlands, streams, shorelines, steep slopes, and their buffers can limit where a home, driveway, well, drainfield, and reserve area may be placed. When critical-area review applies, the responsibilities are divided clearly.
Performs the applicable field work, flags and documents regulated features, prepares the technical materials, and coordinates the Critical Area Verification request with the county.
Snohomish County Planning and Development Services (PDS) reviews the submitted information, visits the property when required, and provides written Critical Area Verification (CAV).
Reviews the development goals and preliminary septic options, then uses the verified critical-area boundaries and other site information to move the OSS design forward.
Need an Environmental Professional?
Depending on the property, the appropriate consultant may be a wetland scientist, biologist, geologist, or geotechnical professional. Ask whether the consultant will perform the field work, prepare the required documents, manage the PDS submittal, and respond through written verification.
These resources help homeowners begin their search and do not constitute an endorsement of any individual consultant.
Phase 2 — OSS Design & Review
MKPE evaluates the soils, establishes the system approach, and prepares the site plan, design drawings, calculations, construction details, and supporting documents.
The OSS application and design are submitted to the Snohomish County Health Department. If the property requires an individual well, the water-supply application can be submitted with the OSS application so the well and septic locations are reviewed together.
The Health Department reviews the design and site conditions. MKPE responds to standard review comments and revises the design when required within the agreed scope.
Phase 3 — Construction & Closeout
An approved design is not permission to begin construction. Applicable requirements must be completed and the installation permit must be issued first.
After applicable permit requirements are complete, a certified OSS installer is selected and the installation permit is issued.
The installer builds the approved system and leaves it uncovered. MKPE confirms the installation matches the approved design. For systems with pumps, MKPE and the installer verify that the pump, controls, alarm, dosing, and distribution operate as designed.
MKPE prepares the as-built record. The Health Department performs its final inspection and authorizes covering the system after acceptance.