Reserve Silica Reclamation
The remedial investigation activities are ongoing, and Ecology anticipates that the Remedial Investigation Report will be available for public comment by the end of 2023. Work plans and preliminary investigation reports are available under the View Documents tab.
Site Location
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 Site boundary will be determined based on the findings of the planned Remedial Investigation. 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.
Mining History
Coal and sand were mined from geologic rock formations from 1924 to 2007 at the Site.
Coal Mining
Underground coal was mined from the Dale No. 4 and 7 coal seams from 1924 to 1933, and from the Dale No. 7 seam from 1945 to 1948. The underground mine continues to drain from a pipe installed in the collapsed Dale mine portal.
Surface coal mining was performed from the Dale No. 4 seam from 1946 to 1950, in an area referred to as the Dale Strip Pit (DSP).
Sand Mining
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) as fill material.
- Approximately 175,000 tons of CKD were disposed in the LDA from June 1979 to October 1982. After placement, the CKD was graded, covered by a 2-foot thick layer of clayey material and a 7-foot layer of overburden from the sand mining operations, and the area was seeded with grass.
- The DSP was reclaimed with CKD between November 1982 and 1989 with an estimated 250,000 cubic yards of fill material. The top 7 feet of the DSP was reclaimed with 4 feet of on-site clay soil and 3 feet of overburden from the sand mine, and the completed surface was seeded.
- 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.
Permits
Mining reclamation and landfilling activities are regulated by:
Washington State Department of Natural Resources (DNR)
DNR issued a Surface Mining Permit for sand mining and reclamation in 1971. This permit was cancelled on April 15, 2010 following King County’s request to assume primacy.
Washington State Department of Ecology (Ecology)
Ecology grants coverage under the Sand and Gravel General Permit for the discharge of surface water at the mining Site.
King County Department of Local Services
King County issues a Grading Permit to regulate reclamation activities.
Public Health – Seattle & King County (Public Health).
· Public Health issues a Post-Closure Maintenance Permit for the Lower Disposal Area and the Dale Strip Pit.
· Public Health issues an Inert Waste Landfill Permit for filling of the Lower Pit and Middle Pit area.
Release Of Contamination
In June 1981, Ecology became aware that caustic storm water was released from the LDA during the filling of the surface pit from June 1979 to October 1982. Industrial Mineral Products, a predecessor company of Holcim (US) Inc., alleged that the cementitious CKD would cure and harden like concrete, preventing further releases.
High pH seepage continues to be released on the northwest side of the LDA, and elevated pH and arsenic and lead concentrations have been observed in surface water and groundwater at the Site. Ecology issued a Notice of Violation on June 29, 2016 for the release of high pH surface water. Seepage of hazardous constituents from the LDA led to the regulation of the Site under the state cleanup law, the Model Toxics Control Act .
Cleanup Work So Far
• 1979-1980: Industrial Mineral Products allowed caustic surface water to flow unconfined to a borrow pit along Black Diamond-Ravensdale Road, about a 1,000 feet from the seepage face. The impacted surface water was allowed to percolate to groundwater in the advance outwash formation.
• 1981: Ecology requested that the caustic discharge be neutralized with acid at its point of origin. Industrial Mineral Products dismissed acid neutralization due to the absence of power needed for a metering pump, and concerns about spillage and vandalism.
• 1981: Industrial Mineral Products collected the caustic discharge and conveyed it through a corrugated pipe to mix with purported acid mine drainage from the Dale mine portal. The drainage pipe was routed along an old drainage ditch adjacent to the mine road. The relatively large flow of weakly acidic mine drainage (pH 6.6) was reported to neutralize the relatively small flow of strongly caustic leachate (pH 12.4) to a pH of 8.1, which met the state discharge criteria (pH 6.5–8.5). The mixed discharge then flowed overland to the borrow pit.
In 2002, Reserve Silica executed an Agreement to allow Holcim to conduct monitoring and remediation activities for the CKD landfills. The investigation and remediation activities for the CKD include:
• 2002: Developed a monitoring well system and reported data quarterly to Ecology and Public Health.
• October 2006: Submitted post-closure plan for the LDA and DSP. Evaluated remediation alternatives for the LDA, including construction of a clay cap and a shallow leachate collection interceptor trench. Evaluated leachate treatment options, including wetlands, onsite chemical treatment, and discharge to an offsite wastewater treatment plant.
• September to October 2007: The cover of the LDA was upgraded to reduce infiltration. A minimum 2-foot thick low permeability soil cover was constructed. The soil cover was graded to drain stromwater and then seeded with grass.
• September 2008: Constructed and monitored two test trenches to collect high pH seepage from the LDA.
• 2009 to 2013: Performed hydrogeological studies for the LDA. The studies included test trenches and borings, seismic refraction to evaluate depths to bedrock, electromagnetic imaging to evaluate interconnected porosity, moisture content, and dissolved ion concentrations, and groundwater tracer studies to evaluate groundwater flow.
• November 2010 to July 2011: The DSP soil cover was upgraded. The cover was regraded to promote drainage and a minimum 2-foot thick low permeability soil cover was a constructed and vegetated with grass to reduce infiltration.
Next Steps
Learn How Ecology Is Protecting The Environment In Your Community
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Phone: 206-594-0000
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Documents 85
Legal 4
Document Title | Document Date | Document Type |
Reserve Silica Reclamation - Agreed Order DE16052 | 12/16/2019 | Agreed Order |
Reserve Silica Reclamation - Final Determination of Liability, BNSF Railway | 3/5/2018 | Final Potentially Liable Person Status Letter |
Reserve Silica Reclamation - Final Determination of Liability, Reserve Silica Corporation | 9/5/2017 | Final Potentially Liable Person Status Letter |
Reserve Silica Reclamation - Final Determination of Liability, Holcim (US) Inc. | 9/5/2017 | Final Potentially Liable Person Status Letter |
Map 4
Document Title | Document Date | Document Type |
Reserve Silica Reclamation - Ravensdale Group of Mines (DNR Map K56_C) | 6/1/1994 | Map |
Reserve Silica Reclamation - Ravensdale No. 2 Mine (DNR Map K60_G) | 6/1/1940 | Map |
Reserve Silica Reclamation - McKay and No. 5 Bed Workings (DNR Map K56_D) | 9/1/1936 | Map |
Reserve Silica Reclamation - Dale Mine No. 1 (DNR Map K62_A) | 7/15/1931 | Map |
Public Information 10
Technical Reports 67
Places to see print documents
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Solid Waste Program - Northwest Regional Office15700 Dayton Ave NShoreline, 98133This location may only have print documents available during open comment periods.
Contaminants 2
Contaminant Type | Soil |
Groundwater |
Surface Water |
Air |
Sediment |
Bedrock |
---|---|---|---|---|---|---|
Metals - Metals Priority Pollutants | S | C | C | |||
Reactive Wastes - Corrosive Wastes | S | C | C |
- S
- Suspected
- C
- Confirmed Above Cleanup Levels
- B
- Below Cleanup Levels
- RA
- Remediated-Above
- RB
- Remediated-Below
- R
- Remediated