How the cleanup process works

Cleaning up contamination can mean removing contaminated material from the site and storing it in a special landfill, treating it until it’s no longer harmful, or isolating it so it can’t affect human health or the environment. The cleanup process is defined in the Model Toxics Control Act (MTCA), Washington’s cleanup law.

Property owners can clean up independently or with our supervision. We also manage some cleanups directly. Cleanups we conduct or supervise are called formal cleanups. We follow the steps below and ask for public feedback at key points. Independent cleanups don’t have the same public participation requirements, but they must meet the same cleanup standards.

Steps in the formal MTCA cleanup process

1. Discovery & initial investigation

Find a hazardous spill or suspect one happened in the past? Report it to us, and we’ll investigate and inform the property owners. Property owners might clean up minor spills at this stage. If they don’t, we add the site to our Confirmed and Suspected Contaminated Sites List.

2. Site Hazard Assessment

We evaluate the potential risk the contamination poses to human health and the environment. We're currently working on a new process for assessing and ranking sites.

When we supervise cleanups, we may issue an order or enter into a settlement agreement after completing a site hazard assessment.

3. Remedial Investigation and Feasibility Study

To clean up a site, we need to know what’s there. Remedial investigations collect environmental data to learn what chemicals are contaminating the site and where they are. Sometimes contamination can travel a long way from the initial leak or spill.

A feasibility study uses the results of the remedial investigation to explore different ways to clean up the contamination. A cleanup option might combine several different methods. The study evaluates several options to see if they meet legal requirements and to weigh the benefit of each option against the cost.

4. Cleanup Action Plan

We consider public comments on the feasibility study and choose a preferred option for the cleanup action plan. The plan includes the schedule, standards, and requirements for every phase of the cleanup. It also explains why we chose the cleanup option.

We consider public comments before finalizing the cleanup action plan.

5. Engineering Design

Cleanups are often very complex construction projects with many parts. This stage adds details about how exactly to construct, operate, maintain, and monitor the cleanup.

6. Clean up the site!

Cleanups are construction projects that follow the cleanup action plan. That might mean building a treatment facility for contaminated groundwater, digging up contaminated sediment and sending it to a hazardous waste landfill, or consolidating the contaminated soil and isolating it so living things aren’t exposed.

7. Monitoring and site-use controls

At times some contamination is safetly left at a site after cleanup construction is finished. Contaminated soil may be isolated underneath a building or cap, or a long-term treatment system may clean the groundwater. To keep the contamination isolated, we may restrict how these sites can be used. These restrictions are called institutional controls. An institutional control may prohibit installing drinking water wells or disturbing a protective cap that isolates contamination. The controls are usually listed in environmental covenants recorded with the county.

We review these sites about every five years to make sure the controls are still effective and the cleanup still protects living things from contamination. We share these reports for public comment.

8. De-list the site

If we added the site to the Hazardous Sites List, we remove it after it meets all cleanup standards and requirements from the cleanup action plan. We ask for public input before we remove a site from this list.

Sites that have been cleaned up are marked No Further Action in our database.

Law and policy about the cleanup process

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