Project Name: Valmont Butte Property, Boulder, Colorado
Date Project Began: December 2008
Date Project Completed: August 2013
Project Description: Casey Resources Inc. (CRI) was contracted by the City of Boulder (the "City") to perform soil investigation on a 101 acre site to determine the areas and extent of environmentally impacted soil at the Valmont Butte Property. The Valmont Butte Property (the "Property") is located in Boulder County, approximately four miles east of the City's central business district. The Property's past use included fluorspar and precious metals processing and containment of milling wastes in two tailings impoundments. Past environmental investigations had identified potential metals and radiation impacts in soils at the Property. Based on these previous investigations, CRI prepared a detailed Work Plan that included an extensive sampling and analysis plan to confirm environmentally impacted areas. The Work Plan was approved by the Colorado Department of Public Health and Environment (CDPHE) and the work was initiated during the summer of 2009. CRI personnel completed a structured soil quality investigation using field-portable X-ray fluorescence (XRF) equipment and laboratory analysis for quality control checks. The XRF sampling program was the most comprehensive soil investigation completed at the Property to date. Approximately 1,000 XRF measurements were taken during the metals screening program. During the site screening investigation, approximately 679,600 square feet (15.6 acres) of the Property were identified as containing lead concentrations that exceed the screening value of 800 milligrams per kilogram (mg/kg). As part of the Work Plan, a radiation survey of the Property was also conducted using state-of-the-art portable gamma radiation sodium iodide (NaI) detection meters with real-time Global Positioning System (GPS) equipment. Over 115,000 data points were collected during the survey. These data were correlated to specific onsite radiation source measurements collected using a High Pressure Ion Chamber. The results of the site investigations were used to develop specific remediation strategies and closure planning for the Property. These plans were subsequently presented in a Voluntary Cleanup Plan (VCUP) Application for the Property that was approved by the CDPHE in June 2010. CRI developed construction documents for the VCUP implementation as well as obtained County and State permits as required. In addition, CRI assisted the City with notifications and negotiations with Native American representatives and other parties who have cultural interests at the Property.
The City then contracted CRI to implement the VCUP and in April 2012 remediation of the Property was initiated. Soil from all areas that were identified during the metals screening program as exceeding 800 mg/kg lead was excavated and consolidated in the Primary Tailings Impoundment. The XRF was used to assess, in real time, when an area was adequately remediated. Once an area was judged to be remediated based on XRF measurements, the area was gridded and confirmation soil samples were collected and submitted to a laboratory for metals analysis. In addition, confirmation soil samples from areas known to have high concentrations of mill tailings and/or showed higher radiation readings during the site radiation screening were also analyzed for gross α/β and radium 226/228. Once all impacted soils had been consolidated into the Primary Tailings Impoundment, the impoundment was capped with two feet of “clean” soil and 18 inches of rock to prevent prairie dog colonies from inhabiting this area.
During remediation of known conditions, several other sources of contamination were discovered and remediated. These included:
- Petroleum contaminated soil from a oil fired boiler in the Mill Building
- Several buried drums that contained petroleum products (characteristic hazardous and nonhazardous waste)
- A buried pipe line that was insulated with asbestos containing material
- An underground fuel storage tank
Since a large quantity of import soil was needed to meet the final grading plan, CRI established an import soils protocol and monitored soil imported to the Property. Final grading of the site was performed to CRI design specifications and seeding of soil disturbed areas was performed for re-vegetation.
Type of Contamination: Heavy metal and low level radiation impacted soils. ACM, petroleum contaminated soil, buried drums, and an underground storage tank identified during the remediation activities.
