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Lower Bridge Mine

The Lower Bridge Mine site is located 5.5 miles west of Terrebonne, Oregon near Redmond. It is a former diatomaceous earth mine, encompassing 570+ acres.

Starting in the early 1900's the site was strip mined for diatomaceous earth (DE). For 30 years, DE was processed into a form of crystalline silica known as cristobalite. Hazardous and radiological waste was stored on the site for approximately 8 years, before being cleaned up in the mid-1980s by the Department of Environmental Quality (DEQ).


In December 2008, the Deschutes County Planning Commission granted a re-zoning of the mine site property to residential use. This re-zone was conditional upon the developers receiving a certification of "no apparent public health hazard" from the Oregon Health Authority, Environmental Health Assessment Program (EHAP).

In 2009, EHAP developed and sent a Scope of Work document (SOW) to the developers, which described the information needed to determine whether there are (or would be) risks for future residents of the proposed residential development. Soon after the SOW was written, economic forces played a role in the decision for the developer to postpone the planned development of the eastern portion of the property. Then, in 2013, EHAP revised the SOW to focus resources on exposure prevention through dust suppression, rather than additional analysis. 

Read the revised 2013 Scope Of Work (SOW).    

The developers have entered into a voluntary cleanup agreement with DEQ and submitted a draft Plan of Work (POW) that includes a site-wide sampling plan for the proposed residential site. This POW will require approval by EHAP prior to implementation and will be posted here once it is finalized.

View the original cover letter EHAP sent to the developers  

Educational Materials

Public Participation

  • A public availability session was held in May, 2009 to answer questions about the final health consultation. This was an informal open house held at the Redmond Senior Center.
  • EHAP accepted comments from the public on the draft health consultation report until December 8, 2008.
  • EHAP held a public meeting at the Redmond Senior Center in November, 2008. EHAP staff talked about the health consultation findings and answered questions from the public.
  • EHAP held an initial public meeting at the Redmond Senior Center in August, 2008. Staff from the Oregon Public Health Division, Department of Environmental Quality, and the Department of Geology and Mineral Industries were available to talk to citizens who had individual questions. Formal presentations began at 6:30pm.


Please note that the public comment period dates listed in this report are inaccurate. Comments were received until 12/08/09.

Related Websites

lower bridge mine