How to Fill Out the Washington Ecology Water Quality Modification Permit + FAQs

A Washington Ecology water quality permit modification is the formal request you send to the Washington State Department of Ecology when something about your permitted discharge changes and your current coverage no longer matches what is happening on the ground. Most filers use one of two forms: the Construction Stormwater General Permit Modification/Update (ECY 070-558) or the Modification of Permit Coverage Form (ECY 070-361, revised February 2025) for industrial sites. Larger projects that touch wetlands or streams instead use the Section 401 Water Quality Certification request process.

This article walks you through every box on these forms, line by line, in plain words. Ecology funds its permit program through fees set under Chapter 173-224 WAC, and the agency processes thousands of stormwater coverage actions each year, with construction permit terminations alone taking around 30 days to clear. A wrong or late modification can stall a project, trigger an inspection, or expose you to enforcement penalties, so getting each field right matters.

Here is what you will learn:

• 📝 How to fill out each form field, box by box, with real sample entries
• 📂 Which documents and ID numbers to gather before you open the form
• 🖥️ How to file through Ecology’s online portal, by email, and by mail
• ⚠️ The most common mistakes filers make and what each one costs you
• ❓ Clear answers to the questions filers ask most about modifications

What the Form Is and Who Must File It

A water quality permit modification tells Ecology that the conditions in your original permit coverage have changed. You file it when your site grows, shrinks, changes hands, adds a new discharge point, or starts a new activity that affects stormwater or wastewater. The agency that receives the form is the Washington State Department of Ecology Water Quality Program, which administers permits under the authority of RCW 90.48, the state Water Pollution Control Act.

The permit modification follows the permit, not the calendar. There is no single annual due date for construction sites, because you file when the change happens. Industrial stormwater permit holders, by contrast, often submit Modification of Permit Coverage forms by a set date, and the 2025 Industrial Stormwater General Permit guidance lists an August 31 deadline tied to the permit year. Knowing which schedule applies to you is the first step.

Who must file? Any person or company that already holds a Construction Stormwater or Industrial Stormwater General Permit and has a change to report must file. Builders, developers, general contractors, factory operators, and the consultants who file for them all use these forms. Ecology stresses that permit coverage follows the person, so the named permit holder, not the property, carries the duty to keep coverage current.

The statute behind the form is the federal Clean Water Act, carried out in Washington through the state’s National Pollutant Discharge Elimination System (NPDES) authority. The deadline is event-driven for construction and date-driven for industrial. The penalty for ignoring it can reach significant civil penalties per day of violation, plus the risk that Ecology terminates your coverage. Each of these pieces connects: the statute creates the duty, the form satisfies it, the deadline times it, and the penalty enforces it.

Before You Start: Documents and Information You Need

Gathering your paperwork first saves you from a half-finished form and a second trip through the portal. The Construction Stormwater Modification/Update form marks all fields as required unless noted, so a missing detail stalls the whole request. Here is your pre-filing checklist.

• Your permit number. This is the unique coverage number Ecology assigned you (for example, WAR123456). Without it, Ecology cannot match your form to your file, and the request bounces back.
• Site or project name. Use the exact name on your existing permit. A new name confuses the match and can delay review.
• Site street address or location description. Ecology ties coverage to a physical location, so a wrong address can attach your change to the wrong site.
• Legal landowner and operator names. Changes in operator or owner drive many modifications, and the agency cross-checks these names.
• Updated site maps and acreage figures. If your disturbed acreage changes, you need current numbers, because fees and conditions scale with disturbed area.
• Your updated Stormwater Pollution Prevention Plan (SWPPP). Many modifications require a revised SWPPP that reflects the new conditions, and filing without it is a common cause of follow-up requests.
• Receiving water names. You must name the water body that receives your discharge, since Ecology checks it against water quality standards in Chapter 173-201A WAC.
• Authorized signatory details. The form must be signed by a person with legal authority to bind the permit holder, or Ecology will not accept it.
• WQWebPortal login. Most filers submit online, so set up or recover your portal account before you start.

If any item is missing, the most likely result is a delay. Ecology contacts you for the gap, the review clock pauses, and your change sits unapproved while work may need to wait. Collecting everything up front keeps your modification moving.

Where to Get the Form and How to Access It

You get the official forms straight from Ecology’s publications library, not from a third-party site, so you always have the current version. The Construction Stormwater Modification/Update form (ECY 070-558) is posted as both a PDF and a Microsoft Word file, which lets you type directly into the document. The Industrial Stormwater Modification of Coverage form (ECY 070-361) was last revised in February 2025, so confirm that date on the copy you download.

For projects that affect wetlands, streams, or other waters, the modification runs through the Section 401 certification process, which uses the 401 Request Form (ECY 070-674) alongside a Joint Aquatic Resources Permit Application (JARPA). That form lists the information Ecology needs to review and process a 401 request without delay.

Most permit holders never download a paper form at all, because Ecology routes stormwater changes through its online system. You access it through the WQWebPortal, the same secure system you use for discharge monitoring reports. Inside the portal you select your existing coverage and choose the modification option, which pre-fills your permit details and reduces typing errors.

If you prefer a fillable file, the Word version is the friendliest, because it lets you tab from box to box and keeps your entries clean. Print only at the end if you must mail the form. Always check that the revision date on your downloaded form matches the date on Ecology’s summary page, since using an outdated version is a frequent reason filings get returned.

Step-by-Step: How to Fill Out the Construction Stormwater Modification/Update Form Line by Line

This section is the heart of the article. The ECY 070-558 form is organized into parts, and each part holds several numbered fields. Fill them in the order they appear, because later boxes build on earlier ones. Every field below tells you what it asks, how to answer, a sample entry, an edge case, a common mistake with its cost, and a myth to drop.

Part 1, Field 1a: Site or Project Name

This box asks for the name of the construction site as it appears on your current permit. Write the name exactly as Ecology has it on file, using the same spelling and capitalization. For example, Riverbend Townhomes Phase 2 should appear the same way it did on your original Notice of Intent.

A common edge case is a project that changed names after it was permitted. If your marketing name changed but Ecology’s record did not, use the permitted name in this box and note the new name elsewhere. A common mistake is entering a fresh project name that Ecology has never seen, which breaks the link to your file and forces a manual lookup that adds days to review. Many filers wrongly believe this box is just a label; in fact it is one of the keys Ecology uses to match your modification to the right coverage.

Part 1, Field 1b: Street Address or Location Description

This field asks where the site physically sits. Enter the street address if one exists, written in standard format, such as 412 Riverbend Lane, Spokane, WA 99201. If the site has no street number, describe the location instead, using cross streets, parcel numbers, or a quarter-section description.

The frequent edge case is a raw-land project with no assigned address, which is normal for new subdivisions. In that case a clear location description, such as NE corner of Mill Rd and 5th Ave, parcel 12345, keeps Ecology from guessing. The common mistake is entering a mailing address instead of the site address, which can route your change to the wrong location and trigger a correction request. People often think any address will do, but Ecology ties discharge conditions to the exact site, so precision here protects you.

Part 1, Field 1c: Permit Number

This box asks for the coverage number Ecology assigned when you first got the permit. Copy it exactly, including the letter prefix, such as WAR304512. You can find it on your permit coverage letter or inside your WQWebPortal account.

An edge case arises when a company holds several permits across different sites. Make sure you pull the number for the specific site you are modifying, not a sister project. The common mistake is transposing digits or using an old, terminated number, which causes Ecology to reject the form because it cannot find a live match. A widespread myth is that your name alone is enough to identify you; Ecology runs on permit numbers, and a wrong one stops the process cold.

Part 2: Permittee and Contact Information

This part asks who holds the permit and who Ecology should contact about the change. Enter the legal name of the permit holder, the mailing address, and a working phone number and email for the day-to-day contact. For example, Cascade Builders LLC, with Maria Delgado listed as the site contact at a monitored phone and email.

The edge case here is a separate operator and owner. If a general contractor runs the site for a developer, list the legal permit holder as the permittee and the on-site manager as the contact, so messages reach the right desk. The common mistake is listing a contact who has left the company, which means Ecology’s questions go unanswered and your review stalls. Filers often assume the contact is just a courtesy line, but Ecology uses it to resolve gaps fast, and a dead contact can cost you weeks.

Part 3: Description of the Modification

This is the most important narrative box on the form. It asks you to describe, in clear terms, what is changing and why. Write a short, factual statement, such as Adding 3.5 acres of disturbed area on the east parcel and one new discharge point to Mill Creek, effective 07/01/2026.

The common edge case is multiple changes at once. If you are adding acreage and changing operators in the same filing, list each change as its own line so the reviewer can track them separately. The common mistake is a vague entry like minor update, which forces Ecology to call you for details and delays approval. Many filers believe a brief note is safer; in truth, a complete and specific description speeds review, because the reviewer can act without chasing you.

Part 4: Disturbed Acreage and Site Changes

This part asks for the current and revised totals for disturbed area and any change to site boundaries. Enter both the old and new figures in acres, such as Previous: 4.0 acres; Revised: 7.5 acres. Attach an updated site map that shows the new limits of disturbance.

The edge case is phased construction, where acreage rises and falls over time. Report the disturbed acreage that applies once the change takes effect, not the lifetime total. The common mistake is updating the number without attaching the map, which leaves Ecology unable to verify the change and prompts a follow-up. Filers sometimes think acreage is cosmetic, but it can move you into a different fee tier and change your monitoring duties, so accuracy here has a direct dollar effect.

Part 5: Receiving Water and Discharge Points

This field asks where your stormwater goes. Name each receiving water and identify every discharge point, using the same labels as your SWPPP, such as Discharge Point 2 to Mill Creek. If discharge flows to a municipal storm sewer first, name that system and the ultimate water body.

The edge case is groundwater infiltration with no surface discharge, which you should state plainly rather than leave blank. The common mistake is naming a different water body than the one in your SWPPP, which creates a conflict that Ecology must resolve before approval. A common misconception is that all nearby water counts the same; Ecology checks the named water against state water quality standards, and an impaired water can bring extra conditions, so name it correctly.

Part 6: Certification and Signature

The final part asks an authorized person to certify that the information is true and to sign and date the form. Sign with a person who has legal authority to bind the permit holder, print that person’s name and title, and enter the date in MM/DD/YYYY format, such as 06/15/2026. The certification carries legal weight under penalty of law.

The edge case is a consultant filing on a client’s behalf; the consultant may prepare the form, but the certifying signer must be an authorized officer or duly authorized representative of the permittee. The common mistake is an unsigned or wrongly signed form, which makes the submission invalid and sends it back unprocessed. Filers often assume any manager can sign, but Ecology requires a person who meets the signatory rule, and the wrong signer voids the certification.

Step-by-Step: The Industrial Stormwater Modification of Coverage Form (ECY 070-361)

Industrial sites use a shorter, three-page form, but the logic is the same. The Modification of Permit Coverage form for industrial activities asks for your facility name, permit number, the specific change, and an authorized signature. Enter your facility name and permit number exactly as they appear on your existing coverage, then describe the modification, such as adding a new outfall or a new industrial activity.

The most common industrial changes are adding a new pollutant-generating activity, changing the facility’s primary operator, or correcting acreage and outfall counts. For each, describe the change clearly and attach supporting documents, such as a revised SWPPP or site map. The common mistake on this form is treating it like a renewal; a modification reports a change to live coverage, while a renewal extends an expiring permit, and confusing the two delays both. Because fee reductions are not available to industrial stormwater permit holders under WAC 173-224-090, report changes that affect your fee tier honestly and on time.

Three Filled-Out Examples Using Real Scenarios

Seeing the form filled in by real filers makes each box click. Below are three common fact patterns, each shown as a two-column table.

Scenario 1: Carlos Adds Acreage to a Construction Site

Carlos manages a townhome build and is expanding the disturbed area onto a new parcel.

Form Section	What Carlos Enters
Site or Project Name (1a)	Riverbend Townhomes Phase 2
Street Address (1b)	412 Riverbend Lane, Spokane, WA 99201
Permit Number (1c)	WAR304512
Permittee Name (Part 2)	Cascade Builders LLC
Site Contact (Part 2)	Carlos Mendez, monitored phone and email
Description of Modification (Part 3)	Adding 3.5 acres of disturbance on east parcel
Disturbed Acreage (Part 4)	Previous: 4.0 acres; Revised: 7.5 acres
Receiving Water (Part 5)	Discharge Point 2 to Mill Creek
Signature and Date (Part 6)	Signed by authorized officer, 06/15/2026

Scenario 2: Janet Changes the Site Operator

Janet’s firm is taking over an active site from another contractor and must update the operator on file.

Form Section	What Janet Enters
Site or Project Name (1a)	Eastgate Commercial Plaza
Street Address (1b)	88 Commerce Way, Tacoma, WA 98402
Permit Number (1c)	WAR298017
Permittee Name (Part 2)	Summit Site Works Inc
Site Contact (Part 2)	Janet Okoro, project superintendent
Description of Modification (Part 3)	Change of operator from prior contractor, effective 07/01/2026
Disturbed Acreage (Part 4)	Previous: 2.0 acres; Revised: 2.0 acres (no change)
Receiving Water (Part 5)	Discharge Point 1 to municipal storm sewer to Commencement Bay
Signature and Date (Part 6)	Signed by authorized representative, 06/20/2026

Scenario 3: Marcus Adds a New Outfall at an Industrial Facility

Marcus runs a metal fabrication plant and is adding a new outfall, so he uses the industrial ECY 070-361 form.

Form Section	What Marcus Enters
Facility Name	Northwest Metal Fab
Permit Number	WAR012345
Facility Address	1500 Industrial Ave, Everett, WA 98201
Primary Operator	Marcus Lee, plant manager
Description of Modification	Adding Outfall 003 discharging to Snohomish River
Supporting Documents	Revised SWPPP and updated site map attached
Activity Change	New stormwater contact from wash-bay area
Receiving Water	Snohomish River
Signature and Date	Signed by authorized officer, 08/15/2026

How to File the Completed Form

Ecology accepts modifications through more than one channel, and the right one depends on your permit type. Pick the channel that matches how you normally manage your coverage.

Online through WQWebPortal. This is the preferred path for both construction and industrial stormwater changes. Log in to the WQWebPortal, open your coverage, select the modification option, attach your SWPPP and maps, and submit. The system gives you an electronic confirmation, which is your proof of filing, and there is no separate filing fee for the modification itself, since costs are recovered through your annual permit fee.

By mail. If you must file on paper, mail the signed form and attachments to the Department of Ecology Water Quality Program at the address listed on the form’s contact page. Keep a copy of everything and use certified mail with return receipt so you have dated proof Ecology received it. Paper review takes longer than online, so expect added processing time.

By email. For some forms, Ecology lets you email the completed PDF to the program contact named on the form, such as the staff listed for ECY 070-558. Save the sent message and any reply as your proof of filing.

For 401 certifications. Submit the 401 Request Form and JARPA to the regional Ecology office handling your project, following the instructions on the form. Keep your dated submission record, because the 401 review has its own timeline set by federal rule.

Whatever channel you use, save your confirmation. Construction permit actions such as termination run about 30 days, and industrial actions about 60 days, so your dated proof matters if a question comes up later.

What Happens After You File

Once Ecology has your modification, a permit administrator reviews it against your existing coverage and the applicable rules. If the form is complete, the reviewer updates your coverage and sends a confirmation or a revised coverage letter. If something is missing, the reviewer contacts the person you listed in Part 2, which is why a live contact matters.

Ecology may require an inspection for certain changes, especially those that add discharge points or significant acreage. The agency decides this case by case, and an inspection can extend your timeline. For context, Ecology notes that construction permit termination usually takes about 30 days and industrial termination about 60 days, and modifications fall in a similar range depending on complexity.

Your fee may change after a modification takes effect. Because fees are set by category under Chapter 173-224 WAC, a change in disturbed acreage or activity can move you to a different tier, and Ecology bills on the state fiscal year that runs July 1 through June 30. Watch for an updated invoice, and pay it on time, since unpaid fees can lead to a collections surcharge and even permit termination.

Mistakes to Avoid When Filling Out the Form

Each field on a modification form is its own chance to slip, so review carefully before you submit. Below are the errors filers make most and what each one costs.

• Using an outdated form version. Ecology may return it, and you lose the time it takes to refile on the current version.
• Entering the wrong permit number. The agency cannot match your file, and the request is rejected outright.
• Leaving a required field blank. The form marks most fields as required, so a blank triggers a follow-up that pauses review.
• Writing a vague modification description. A reviewer must call for details, which adds days to approval.
• Reporting new acreage without a site map. Ecology cannot verify the change and asks you to resubmit.
• Listing a stale contact person. Ecology’s questions go unanswered and your review stalls.
• Naming a receiving water that conflicts with your SWPPP. The mismatch must be resolved before approval.
• Confusing a modification with a renewal. You file the wrong action and delay the change you actually need.
• Using an unauthorized signer. The certification is invalid and the form is sent back.
• Forgetting to save your filing confirmation. You lose your proof that you filed on time if a dispute arises.
• Ignoring a fee tier change. An unpaid higher fee can lead to a surcharge or enforcement.
• Filing the change late. Discharging under conditions that do not match your permit exposes you to civil penalties.

Do’s and Don’ts

A few simple habits keep your modification clean and fast.

Do:

• Do download the form straight from Ecology, because that guarantees the current revision.
• Do copy your permit number exactly, since one wrong digit stops the match.
• Do describe each change in its own clear line, so the reviewer can act without calling you.
• Do attach updated maps and your SWPPP, because Ecology verifies changes against them.
• Do list a monitored contact, since that person fields any questions during review.
• Do save your confirmation, because it is your proof of timely filing.

Don’t:

• Don’t reuse an old or terminated permit number, because it breaks the link to your file.
• Don’t write a vague summary like minor update, since it forces a delay.
• Don’t let an unauthorized person sign, because that voids the certification.
• Don’t mail without proof of delivery, since you may need a dated record later.
• Don’t ignore a revised invoice, because unpaid fees can reach collections.
• Don’t wait to file after a change takes effect, since a mismatch invites penalties.

Pros and Cons of Filing on Your Own vs. With Help

Many small filers handle modifications themselves, while larger or complex changes often go to a consultant. Weigh both paths against your situation.

Filing on Your Own	Filing With Professional Help
Pro: You save the consultant fee, which helps on tight budgets.	Pro: A consultant knows the boxes that trip filers, which cuts errors.
Pro: You control the timeline and submit the moment a change happens.	Pro: They handle the SWPPP and maps, which saves you hours.
Pro: You learn your own permit, which helps with future filings.	Pro: They track fee tiers, so you avoid surprise invoices.
Pro: There is no separate modification fee, so the direct cost is low.	Pro: They speak Ecology’s language, which can speed review.
Pro: Simple changes, like a contact update, are quick to self-file.	Pro: They carry the signatory and certification risk off your desk.
Con: A small error can cost weeks in delays.	Con: Their fee adds to your project cost.
Con: You may miss a fee tier change and face a surprise bill.	Con: You depend on their schedule, not yours.
Con: You carry the legal weight of the certification alone.	Con: You still must give them accurate site data.
Con: Complex 401 or multi-change filings can overwhelm a first-timer.	Con: A distant consultant may not know your site’s daily reality.
Con: You spend your own time learning the form.	Con: Hand-offs can create gaps if communication slips.

FAQs

Do I need to file a modification if I only change my site contact person?

Yes. A change in the contact or permittee information should be reported so Ecology can reach the right person, and keeping it current prevents review delays and missed notices.

Do construction and industrial sites use the same modification form?

No. Construction sites use ECY 070-558, while industrial stormwater sites use ECY 070-361, and using the wrong form for your permit type can cause Ecology to return it.

Do I pay a separate fee just to file a modification?

No. Ecology recovers its costs through your annual permit fee under Chapter 173-224 WAC, though a change in acreage or activity can move you to a higher fee tier on your next invoice.

Do I write the permit number with the letter prefix in the Permit Number box?

Yes. Enter the full coverage number including the prefix, such as WAR304512, because Ecology matches your form to your file using the complete number.

Do I put the mailing address or the site address in Field 1b?

No. Field 1b asks for the physical site location, not your mailing address, so enter the street address or a clear location description of the construction site itself.

Do I need to attach an updated SWPPP with my modification?

Yes. Most modifications that change site conditions require a revised SWPPP, and filing without it is a common reason Ecology sends a follow-up request.

Do I list the old and new acreage in Part 4, or just the new figure?

Yes. List both the previous and revised acreage so the reviewer can see the change clearly, and attach a site map that shows the new limits of disturbance.

Do I have to name the receiving water on the form?

Yes. You must name each receiving water, because Ecology checks it against state water quality standards in Chapter 173-201A WAC, and an impaired water can bring extra conditions.

Do I file a modification or a renewal when my permit is about to expire?

No. A modification reports a change to live coverage, while a renewal extends expiring coverage, so use the renewal process for an expiring permit, not the modification form.

Do I qualify for a small business fee reduction on a stormwater permit?

No. Fee reductions are not available to construction or industrial stormwater general permit holders under WAC 173-224-090, so plan for the full fee tied to your coverage.

Do I need an authorized officer to sign, or can any manager sign Part 6?

No. The certification must be signed by an authorized officer or duly authorized representative of the permit holder, and a signature from anyone else voids the certification.

Do projects that affect wetlands or streams use these stormwater forms?

No. Those projects use the Section 401 Water Quality Certification process with the 401 Request Form (ECY 070-674) and a JARPA, not the stormwater modification forms.

Do I get proof that Ecology received my modification?

Yes. The WQWebPortal gives an electronic confirmation, and for mailed forms you should use certified mail with return receipt so you hold dated proof of filing.

Do I need to file again if I make several changes at one site?

No. You can report multiple changes on one modification form, but list each change as its own clear line so the reviewer can track and approve them separately.