Bothell Riverside HVOC

Last Updated: 12/28/2022

Ecology and the City of Bothell are moving forward with the cleanup of the Bothell Riverside HVOC Site in the downtown Bothell area. This Site is one of six sites in the historic downtown area that have received grant funding from Ecology to help with the cost of cleanup. 

The following Riverside HVOC documents were available for public comment from November 21 - December 22:
 
Agreed Order (AO) 
A legal agreement between Ecology and the City requiring the City to investigate the contamination, share different methods for cleaning it up, and create a draft cleanup plan for Ecology’s selected cleanup method.

Supplemental Remedial Investigation/Feasibility Study (RI/FS) 
A description of the nature and extent of the contamination, evaluation of other ways to clean up the Site, and a recommendation of a preferred remedial alternative.

Draft Cleanup Action Plan (dCAP): (pg.26 of the Agreed Order)
A description of Ecology’s selected cleanup action and the specific cleanup standards for the Site.

We received no public comments during the comment period and are moving forward with finalizing the documents above. We will update this webpage with next steps in early 2023. 

November 2022 Community Mailer

If you would like to be added to the mailing list or email list for this site, contact Meredith Waldref. 

The Bothell Riverside HVOC (Halogenated Volatile Organic Compounds) Site is generally located at NE 180th Street & Woodinville Drive (SR 522) in Bothell. Originally, this Site was considered an “area” within the overall Riverside Site.  

Operations at a former machine maintenance shop are believed to have caused HVOC contamination to enter groundwater in the HVOC area at cleanup levels higher than allowed under the Model Toxics Control Act (MTCA).

In 2009, Ecology and the City of Bothell entered into an Agreed Order to conduct investigations, develop cleanup alternatives, and perform interim cleanup actions at this site. Investigations found chlorinated solvents in groundwater in the HVOC area and petroleum contamination in the soil in the TPH area. The areas were then split into two cleanup sites.

In 2013, Ecology and the City agreed to amend the 2009 Agreed Order so that the City could conduct an interim cleanup action to prevent the chlorinated solvents from discharging into the Sammamish River. The City installed six extraction wells to collect solvent-contaminated groundwater and treat and discharge it into the sanitary sewer.

In 2019, Ecology negotiated a new Agreed Order with the City for the Bothell Riverside HVOC Sites. This new order replaced the existing 2009 Agreed Order for the original larger Bothell Riverside Site.

Remedial Investigation and Feasibility Study
HVOC-impacted soil exceeding MTCA cleanup levels range from 12 to 30 feet below ground surface. HVOC-impacted groundwater exceeding MTCA cleanup levels is present at depths less than 15 feet below ground surface.  Impacted soil and groundwater were found to be suitable for mass removal through soil vapor extraction and bioremediation.

Proposed cleanup
A soil vapor extraction system will be installed in the source area.  In addition, a bioremediation and groundwater recirculation system will be installed to treat HVOC contamination in the groundwater.  The contaminated groundwater will be treated and discharged back into the ground.  Once the bioremediation/recirculation system is fully operational, none of the treated groundwater is anticipated to be discharged to the sanitary sewer system. More details of the proposed cleanup can be found on page 40-44 of the dCAP.