MS4 annual report checklist for Western Washington Phase II permittees

If you operate an MS4 in Western Washington under the Phase II permit issued by the Washington State Department of Ecology, you’ve got an annual report due each spring. This is a working checklist of what to file, what auditors typically flag, and what the months leading up to submission should look like.

This isn’t a substitute for reading your permit. Permit conditions get amended, deadlines occasionally shift, and your specific obligations may vary by jurisdiction. Treat this as the cheat sheet you check after you’ve read the permit, not before.

When it’s due

The Western Washington Phase II permit’s annual report is generally due March 31, covering the previous calendar year (January 1 – December 31). The current year’s exact deadline and submission portal are on Ecology’s permit page — verify them before you finalize.

If your program is large enough to need internal review cycles, the practical work calendar looks like:

January: pull together preliminary numbers
Early February: management review
Mid-February: finalize narrative sections
Early March: legal and sign-off review
Late March: submit, document the submission

If you’re routinely submitting in the last week before deadline, that’s a sign your records are scattered, not that your team is slow.

What’s in the report

The annual report covers the six Minimum Control Measures plus updates to your Stormwater Management Program (SWMP) plan. The report’s structure roughly follows the SWMP itself, so the more your day-to-day records align to MCM categories, the easier the report assembles.

MCM 1 — Public Education and Outreach

Education events held this year, with audience, format, and topic
Materials distributed (type, quantity, target audience)
Effectiveness measures, where your program tracks them
Audiences reached: residents, businesses, schools, contractors

MCM 2 — Public Involvement and Participation

Public meetings, hearings, comment periods
Volunteer events (cleanups, monitoring programs)
Documentation of comments received and how they were handled

MCM 3 — Illicit Discharge Detection and Elimination

Complaints received and investigated
Field screening results
Source tracing outcomes
Enforcement actions taken
Outfall mapping updates

MCM 4 — Construction Site Stormwater Runoff Control

Number of active construction sites under your jurisdiction
Inspection records by site
Deficiencies identified and corrected
Enforcement actions (NOVs, stop-work orders, escalations)

MCM 5 — Post-Construction Stormwater Management

New BMPs added to inventory this year
Annual inspections of structural BMPs
Maintenance actions performed
Operational deficiencies and follow-up

MCM 6 — Pollution Prevention / Good Housekeeping

Municipal facility inspections
Spill response events
Staff training records
Operations and maintenance updates (fleet wash, salt storage, street sweeping)

SWMP plan updates

Changes to the SWMP since last year
Any reductions in scope and the rationale
Plan additions tied to permit modifications or program growth

Common audit findings

These are the patterns Ecology auditors flag most often. Most aren’t about doing the work badly — they’re about not documenting it cleanly enough.

Numbers in the report don’t reconcile with underlying records. The report says 47 construction inspections, the inspection log shows 41, and three of those are missing follow-up notes. This is the single most common finding. The fix is keeping inspection records in one system that the report rolls up from automatically.

Late or missing IDDE response. Permits typically require a response timeline (often within 7 days from complaint to first action). Missing timestamps on response actions read as missed deadlines, even when the work was done.

Public education events listed without effectiveness measures. “Held a clean water booth at the city fair” is fine documentation. “Reached 240 attendees, distributed 180 brochures, three follow-up calls received” is much stronger.

BMP inventory hasn’t been updated. New developments add post-construction BMPs to your responsibility. If those BMPs aren’t in the inventory by the next reporting cycle, the inspection program shows gaps.

Training records signed off but not detailed. “All staff trained” isn’t a record. Names, date, topic, materials covered, attestation signature — that’s a record.

What to keep on hand year-round

The report assembles itself if the underlying records are clean. The records that need to be clean:

Inspection records with timestamps, locations, findings, and follow-up status
IDDE incident log with response timestamps and outcomes
Public education event log with audience and material counts
BMP inventory with inspection history
Training log per employee
Enforcement actions with full chronology

If those exist in spreadsheets that one person maintains, the report is also one person’s burden — and it breaks when that person changes roles. If they exist in a system anyone on the team can update and search, the report is just a view of what’s already there.

How software fits

Tools like NPDESTracker structure the records described above so the annual report rolls up automatically — every count in the report links back to the underlying record, with audit-log entries for any manual override. That’s not a substitute for doing the work, but it eliminates the spring scramble of reconciling spreadsheets to narrative sections.

See how reporting works →

Submission checklist

The annual report is one of the few pieces of municipal compliance work where the deadline and stakes are both public. A clean submission with reconciled numbers is the difference between a quiet audit and a long one.