Focused Review of Specific Remediation Issues: An Addendum to the Remediation System Evaluation for the Homestake Mining Company (Grants) Superfund Site, New Mexico, Region 6

摘要

The current evaluation of the remediation efforts at the Homestake Mining Company (Grants) Superfund site has been conducted on behalf of the US Environmental Protection Agency (US EPA) by the US Army Corps of Engineers Environmental and Munitions Center of Expertise. The evaluation is intended to supplement the previous Remediation System Evaluation (RSE) conducted for the site by Environmental Quality Management (EQM, 2008). Specific issues remaining from the RSE, as identified in the Scope of Work (Appendix A), have been addressed through data analysis and conceptual design, including: (1) Evaluate the capture of contaminant plumes in the alluvial and Chinle aquifers. (2) Evaluate the overall strategy of flushing contaminants from the large tailings pile with discharge of wastes to on-site evaporation ponds and to identify and compare alternatives. (3) Assess potential modifications to the current ground water treatment plant to improve capacity. (4) Evaluate the projected evaporation rates for the existing on-site ponds and for a proposed evaporation pond west of the on-site tailings piles, as it may affect the restoration activities at the site. (5) Assess the adequacy of the monitoring network at the site. (6) Evaluate the current practice of irrigating with untreated water. (7) Evaluate the smaller of the two tailings piles at the site as a potential source of contamination and the future need for a more conservative cap than the radon barrier.