Reserve Silica Reclamation

The Site is generally located at 26000 Black Diamond–Ravensdale Road near Ravensdale, Washington. The initial Site boundary includes King County Tax Parcel Nos. 362206-9138, 012106-9011, and 352206-9046. The Draft Remedial Investigation Report revises Site boundary.

The Site does not include King County Tax Parcel No. 352206-9018, which is included in the Reserve Silica Plant site located at 28131 Black Diamond-Ravensdale Road. 

Arsenic and lead contaminated soils from the former Asarco Tacoma Smelter site were inadvertently disposed in a reclamation area east and beyond the boundaries of the Reserve Silica Reclamation site in May 2023. Ecology issued a no further action opinion for the Reserve Silica Asarco Soil Disposal site in February 2024 because the release of contamination does not pose a threat to human health or the environment.

The McVeas Trucking Diesel Spill site is associated with the release of an estimated 25 to 50 gallons of diesel when a truck crashed into a stormwater ditch near the mine portal in March 2020. Potentially impacted soil and water were cleaned up and Ecology determined that no further action was necessary.

Coal and sand were mined from geologic rock formations from 1924 to 2007.

Coal Mining

Underground coal was mined from the Dale Nos. 4 and 7 coal seams from 1924 to 1933. Surface mining of the Dale Strip Pit (DSP) to access the Dale No. 4 coal seam was performed between 1945 and 1948. Groundwater within the coal seams discharges through the underground mining works to the mine portal.

Sand Mining

Surface sand mining operations were performed from 1968 to 2007. An area referred to as the Lower Disposal Area (LDA) was mined from the Bonneville Power Administration (BPA) transmission lines to the northwest-southeast trending fault line north of the Dale Nos. 4 and 7 mining areas. The surface pit was mined until inhibited by standing water at the bottom of the pit. Sand mining was performed from additional seams between the DSP and the LDA toward the southeast.

Reclamation

Surface mining areas were reclaimed with fill material to re-contour the surface pits. The LDA and DSP were reclaimed using cement kiln dust (CKD) and mine spoils between 1979 and 1988.  Additional sand-mining pits—the North Pit, Tan Sand Pit, Upper Pit, Lower Pit, and Middle Pit—were filled with inert materials. Reserve Silica continues to reclaim the Lower Pit and the Middle Pit; the remaining sand pits have been reclaimed.

Mining reclamation and landfilling activities are regulated by:

King County Department of Local Services (DLS)

DLS issues Grading Permit No. GRDE15-0011 for the Reserve Silica fill site. The Reserve Silica fill site is associated with reclamation activities to restore specific areas of the property to pre-mining elevations.

Public Health – Seattle & King County (Public Health)

Public Health issues Post-Closure Care and Maintenance Permit No. PR0015708 for the closed CKD landfills—the LDA and DSP.

Public Health issues Inert Waste Landfill Permit No. PR0082027 for disposal of inert waste in reclamation fill.

Washington State Department of Ecology

Ecology Sand and Gravel General Permit No. WAG503029 for the discharge of storm water at the entire Site.

Ecology draft State Waste Discharge Permit No. ST0501373 for the treatment and discharge of seepage water collected from the LDA. Ecology anticipates finalizing the permit in the summer of 2025.

Cement kiln dust (CKD) is a waste product from cement processing. CKD reacts with water to form calcium hydroxide, which can increase the pH to greater than 12 standard units creating caustic water. Caustic water has seeped from the LDA since the 1980s. The cleanup site is associated with the release of contamination from the CKD.

Since 1981, caustic seepage has been directed towards a borrow pit or the Infiltration Ponds, where the seepage was neutralized in groundwater. In 2002, Reserve Silica executed an Agreement to allow Holcim to conduct monitoring and cleanup activities for the CKD landfills. Since 2002, Holcim has completed independent cleanup actions at the Site. These actions include groundwater and surface water monitoring, capping and monitoring of the LDA and DSP, management and treatment of seepage from the LDA, and installation of fencing to mitigate exposure.

Electromagnetic (EM) geophysical surveys indicate that high pH groundwater is released from the northwest side of the LDA and extends in low permeability soil beyond the seepage collection ditch and Lower Haul Road to the South Pond. The EM surveys also depict residual high pH groundwater near the Infiltration Ponds after the startup of the treatment system. The EM surveys do not indicate any lateral migration of high pH groundwater from the DSP.

There has been no confirmed release of contamination from the DSP after more than 20 years of monitoring groundwater in the bedrock monitoring wells and water that discharges from the mine portal. Mine water that discharges through the portal complies with the cleanup standards for the Site. The DSP is not subject to the MTCA regulations and thus not retained as a part of the MTCA Site.

CKD fill in the LDA extends further southeast than the previously demarcated boundary. The low-permeability soil cover does not extend beyond the haul road and parcel boundary.

The low-permeability bedrock beneath the LDA causes water to fill the former surface mine like a bathtub and discharge laterally through a berm on the northwest side of the LDA. The seepage collection ditch intercepts and discharges the caustic water through a pipe to the seepage treatment facility and then to the Infiltration Ponds. The seepage collection ditch has operated since 2013 and the seepage treatment system has operated continuously since 2019. Surface water in the Infiltration Ponds has been neutralized since treatment was initiated.

The Remedial Investigation delineates the extent of contamination defined as the areas where the concentrations of the contaminants of concern (COCs) exceed the preliminary cleanup standards (PCULs). Antimony, arsenic, lead, vanadium, and pH were identified as COCs because their concentrations exceeded the PCULs developed in the Work Plan. Vanadium exceedances are limited to the areas with the highest pH and the concentrations of all the COCs decrease below the PCULs at neutral pH.

• Groundwater contamination extends from the active seepage area within the low permeability Vashon till formation and is encountered in the high permeability recessional outwash when high pH water discharges to the Infiltration Ponds.
• Surface water contamination is limited to the seepage collection ditch, the South Pond, and the Infiltration Ponds. The ponds discharge only to groundwater. Chain link fencing is placed around the seepage area and surface water bodies to restrict access.
• Soil contamination exists in the seepage area and historical drainage areas, while sediment contamination exists in the South Pond and Infiltration Ponds.

Ecology’s Solid Waste Management Program maintains regulatory standards and provides technical assistance to the jurisdictional health departments. The roles of Ecology and the jurisdictional health department are described in WAC 173-350-900 when a permitted landfill is subject to the Model Toxics Control Act due to a release of contamination.

The Model Toxics Control Act (MTCA) is Washington’s cleanup law. MTCA provides requirements for contaminated site cleanup and sets standards that protect human health and the environment. Ecology is the lead agency for the implementation of MTCA.

The MTCA cleanup process includes the several steps shown in the information graphic. Public participation is a key component of Ecology-led and Ecology-supervised cleanups. For this Site, Ecology hosts public comment periods for the Agreed Order, Remedial Investigation, Feasibility Study, and Draft Cleanup Action Plan.

Ecology is committed to providing people with disabilities access to information and services. To request an ADA accommodation, contact Ecology by phone at 360-407-6831 or email at ecyadacoordinator@ecy.wa.gov. For Washington Relay Service or TTY call 711 or 877-833-6341.  Visit Ecology’s website for more information.

To request language services (interpreting/translation), contact Ecology by phone at 425-393-5679 or email nancy.lui@ecy.wa.gov or visit https://ecology.wa.gov/About-us/Accessibility-equity/Language-services. For Relay Service or TTY call 711 or 877-833-6341.