Guidance for contaminated water on construction sites
Our Construction Stormwater Permits require permittees to prevent water pollution by managing water that may be contaminated from their construction sites.
Learn how to handle your contaminated construction stormwater safely and properly. Find helpful documents, links, and frequently asked questions.
This spreadsheet shows treatment systems that may be effective in treating specific contaminants. Users should evaluate the effectiveness of any treatment system they plan to implement and confirm that the chosen treatment system does not cause or contribute to a violation of the water quality standards.
The TAPE program provides a peer-reviewed regulatory certification process for emerging stormwater treatment technologies. This database is a collection of assessed treatment technologies.
Effluent guidelines are national standards based on the performance of treatment and control technologies for wastewater discharges to surface waters and municipal sewage treatment plants. Your local jurisdiction may have different guidelines, so check with them before discharging from your site.
Definitions from the Washington State legislature regarding dangerous wastes and hazardous substances
Frequently asked questions
Provide the location(s), contaminant(s), and contaminant concentration(s) of the soil or groundwater.
Provide the pollution prevention and/or best management practices (BMPs) proposed to control the discharge of soil/groundwater contaminants (example: treatment method).
You can locate existing contaminated sites — or see if your site has already been reported to have contaminants — by using our Toxic Cleanup Sites database.
No. You do not have to test for other contaminants on your construction site to receive a permit. Report known or suspected contaminants that you are already aware of on the NOI.
Discharges must be in compliance with the Construction Stormwater General Permit (CSWGP). See S1.C (Authorized Discharges) & S1.D (Prohibited Discharges).
Written approval from Ecology is required prior to using chemical treatment.
pH adjustment using CO2 or dry ice does not require written approval.
If you plan to discharge to 303(d) or TMDL waterbodies; See S8 in the CSWGP for information on the limits on coverage for discharges.
The answer depends and is site specific.
Infiltration of dewatering water must not cause or contribute to a violation of surface water quality standards (Chapter 173-201A WAC), groundwater quality standards (Chapter 173-200 WAC), sediment management standards (Chapter 173-204 WAC), and human health criteria in National Toxics Rule (40 CFR Part 131.36). Contact your permit manager if you are unsure.
Treatment systems may be linked in series to allow you to remove all contaminants to discharge levels. For example, you may use pH treatment and oil and water separators together. Talk with your vendor about what treatment options may be available.
Yes, any additional sampling or monitoring we require will be issued in an Administrative Order that includes reporting sampling results on the Discharge Monitoring Report (DMR).
The DMR will list the parameters that must be recorded.
If the event may cause a threat to human health or the environment, you must immediately notify us by calling your nearest Ecology office.
Immediately take action to cease the discharge or pollution.
You must also contact us if there is a high turbidity (250+ NTUs or transparency 6cm or less) discharge on your site.
No; however, we recommend you develop a contingency plan for water storage if the treatment system does not perform as anticipated. This will help reduce setbacks due to ineffective treatment methods.
No. NFA letters are issued for several reasons (i.e., meets MTCA, an engineered barrier has been installed, or a deed restriction is in place).
Construction activities may breach engineered barriers or suspend residual contamination in construction stormwater and/or groundwater that may cause or contribute to a standards violation.
No. Meeting MTCA cleanup criteria for soil and/or groundwater does not automatically mean the stormwater discharge from your site will meet water quality standards (Chapter 173-201A WAC). MTCA cleanup standards may leave residual contaminants in soil or groundwater that construction may expose, and could cause or contribute to a standards violation.
Yes. The construction stormwater discharge must not cause or contribute to a violation of surface water quality standards (Chapter 173-201A WAC), groundwater quality standards (Chapter 173-200 WAC), sediment management standards (Chapter 173-204 WAC), and human health criteria in National Toxics Rule (40 CFR Part 131.36).
Discharges that cause or contribute to a violation of these standards cannot be covered by the Construction Stormwater General Permit.
We will respond to your NOI within 30 days indicating:
1) receipt of the NOI
2) any request for additional information
Note the timeframe to issue a permit or admin order can vary greatly depending on the project and location. Please expect we will need additional review time depending on the number of other applications in review and the complexity of the project.
Thirty companies and agencies in Washington can treat, store, dispose or recycle hazardous waste (TSDR) or process used oil. See our guidance on finding waste disposal facilities.
The Western Washington and Eastern Washington Stormwater Management Manuals both contain guidance for assistance in selecting appropriate BMPs (Best Management Practices) to manage contaminated runoff.
Your local jurisdiction’s manual may also contain BMP information.
Treatment systems can be complicated and you may want to seek help from professionals with expertise in this area.
Site-specific indicator levels.
We will establish levels, known as indicator levels, if treated construction stormwater or dewatering water will be discharged.
Stormwater discharges should meet the Water Quality Standards for surface waters of Washington state. Specifically, WAC section 173-201A-240 contains information on toxic substances.
