Reserve Silica Reclamation

The Reserve Silica Reclamation site is located between Ravensdale and Black Diamond, Washington. The site is in a historical mining area where coal and sandstone have been mined from a tilted bedrock formation south of Ravendsdale Lake and Ravensdale Creek.

Two surface mining pits – the Lower Disposal Area and Dale Strip Pit – were reclaimed with cement kiln dust (CKD) and mining spoils between 1979 and 1988 under the permitting authorities of two King County agencies, currently known as King County Department of Local Services and Public Health – Seattle & King County.

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. This creates caustic water. The caustic water has seeped from the Lower Disposal Area since the 1980s. The cleanup site is associated with the release of contamination from the CKD.

Reserve Silica Corporation and Holcim (US) Inc. entered into an agreed order under the state's cleanup law, the Model Toxics Control Act (MTCA) in December 2019. The Agreed Order requires the companies to complete the following:

• Remedial Investigation
• Feasibility Study
• Preliminary Draft Cleanup Action Plan

Public Review and Comment

Draft Remedial Investigation - The Draft Remedial Investigation Report (PDF) describes the history, regulatory and environmental settings, field investigations, conceptual site model, Site boundary, and cleanup standards.

Submit Comments

Comments may be submitted online, through the mail, or email. Ecology will consider and respond to comments received during the public comment period. The Remedial Investigation will be finalized after the public comment period.