Queen City Farms
Updated Through September 5, 2020
Queen City Farms Superfund Site
Location: 17825 Cedar Grove Rd SE, Maple Valley, WA 98038
Queen City Farms (QCF) is a Federal Environmental Protection Agency (EPA) Superfund site and, as such, carries special considerations for any work done on or below the surface. The 324-ac site is located on Cedar Grove Road, ~2.5 mi north of the City of Maple Valley due south of the Cedar Hills Regional Landfill.
Disposal activities on site processed and dumped industrial/hazardous wastes in buried drums, as well as in three ponds, from 1955 to 1964. In 1980 the ponds were sampled by EPA; heavy metals and volatile organic compounds (VOCs) were found in the water, sludge, and sediment. Processing and waste handling activities resulted in contamination of soil and groundwater with organic com- pounds and metals. Following cleanup, operation and maintenance activities and monitoring are ongoing (see: EPA QCF page).
On March 16 the King County (KC) Department of Local Services (DLS) Permitting Division issued a Notice of Application for Queen City Farm Reclamation Phase III. The permit application (GRDE18-0048) was for Grading and Tributary Relocation and included: Refill Operations, Erosion Control, Stream Channel Restoration, Plantings, etc.
May 1, 2020 — GMVUAC Letter to King County’s Department of Local Services Permitting Division regarding Permit Application (GRDE18-0048) Phase III Queen City Farms Gravel Pit Refill Project.
Conclusions and Recommendations
While QCF can reclaim (refill) the mined areas, they can’t restore the pre-mining hydrology or, especially, the hydrogeology.
The TCE groundwater plumes at the Superfund site will probably be impacted to some extent, and additional groundwater monitoring wells will likely be needed. However, there is an ongoing monitoring program, and the plumes migrate slowly enough that Boeing and EPA should be able to identify and address any issues in a timely manner. The refill of the MGPL will even enable Boeing and EPA to place monitoring wells where they couldn’t previously, allowing them to improve their understanding of the how contamination flows through the site, as well as to identify any changes caused by the reclamation project.
The stormwater control measures may not be adequate to manage future peak flows, especially in the decades before the various areas become meaningfully revegetated. The permit should require a contingency plan to enable QCF to upgrade the stormwater detention capacity quickly if needed. This could be developed as part of the additional analysis QCF and LAI has promised to perform after the permit is approved.
To enable restoration of salmon spawning habitat in the Cedar Grove Channel that was disrupted when Aquifer 1 was largely mined out, the permit should include as a Condition the re-establishment of year-round flows in the stream that originates from the spring at the south property boundary. If QCF could truly restore the hydrogeology of the site, this would happen automatically. While that’s not possible, it would be entirely feasible for them to restore this hydrologic function by pumping groundwater into that drainage (ideally at the spring location at the source of the stream) during the late summer and early fall. Perhaps they could use the treated water discharging from Boeing’s groundwater treatment plant, which currently discharges to MGPL and will need to be moved eventually anyway.
On July 14 the US Environmental Protection Agency (EPA) published a Notice of Intent to Delete the Queen City Farms Superfund Site.
August 11, 2020 — GMVUAC Letter to US EPA regarding its proposal to partially delist soils at the Superfund site.
The deletion document should note the likely presence of dioxins and furans in undisturbed soils near the Final Containment Cell (FFC) is a significant unknown. Should residential use ever be allowed in this area, even far into the future, these areas near the FFC should be evaluated for dioxins in near-surface soils before such a land-use change is approved. Before finalizing the deletion, EPA should evaluate whether the 1994 Record of Decision (ROD) cleanup level for polycyclic aromatic hydrocarbons (PAHs) is still protective. If it’s not, the confirmation sampling results from the Buried Drum area outside the FFC should be re-evaluated to see if that area still meets risk-based cleanup levels. This further compounds our concerns about contemplated potential future uses of the Superfund site.