Tailings and Mine Waste 1996

Colorado State University

• Publisher: CRC Press
• Year: 2022
• Print ISBN: 9789054105947
• eBook ISBN: 9781000150544
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Presents papers on mine and mill tailings and mine waste, as well as current and future issues facing the mining and environmental communities. Subjects related to technical capabilities and developments, regulations and environmental concerns are included.

Surface water quality and modelling

DOI:10.1201/9781003077855-48

Screening-level assessment of nonpoint source pollution from inactive hardrock mines in the Cement Creek Basin, Colorado

DOI:10.1201/9781003077855-49

Brian S. Caruso & Jim C. Loftis

Colorado State University, Fort Collins, Colo., USA

Abstract: A watershed-based methodology for the screening-level assessment of nonpoint source pollution from inactive and abandoned metal mines was developed, tested, and evaluated that is intended for use by state and federal agencies responsible for management of these sites. The methodology was designed to generate the common types of baseline site characterization information required for targeting areas for detailed investigation and/or remediation. The Cement Creek Basin, part of the Upper Animas River Basin above Silverton in the San Juan Mountains of southwestern Colorado, was used as the primary case study to develop and evaluate the recommended methodology. The results of this case study are presented in this paper.

1 INTRODUCTION

The intensive mining that occurred in the western U.S. for over a century left a legacy of waste and environmental problems from inactive and abandoned metal, or hardrock, mines (IAMs). These mine wastes have caused and are continuing to cause significant impacts to the water quality of streams and aquatic life, including acidic drainage, sediment, and metals from nonpoint source (NPS) areas such as waste rock and tailings, thereby impairing the beneficial uses of the water bodies (USEPA, 1987, 1991; WGA, 1991). Increasing outdoor recreation, urban sprawl, and general population growth into rural areas where many of these sites are located also increase the risk of exposure of the general public to hazardous mine waste and increase public awareness of and concern over mine waste problems.

No comprehensive national program currently exists for the management of IAMs, and no federal environmental regulations directly address the vast majority of these sites. Overall management goals for IAMs, therefore, have not been defined. Specific information goals for the assessment of these sites that are based on management goals have also not been defined. Unlike coal, there has been no national inventory of noncoal mine waste problems. Much of the existing data, therefore, are incomplete and inconsistent. Attempts to address the IAM problem are very scattered within the federal and state governments (WGA, 1991). The approaches taken by each of the agencies are not consistent, and the management and information goals of each agency are different. One of the primary reasons for the significant differences in the status of state programs is that the inventorying costs alone can be as high as over one million dollars in states such as Idaho and Montana, and funds for most states to address the problem are not currently available (WGA, 1991). The effective management of IAMs will require the prioritization or “targeting” of sites given limited resources. Therefore, a watershed-based methodology for the screening-level assessment of IAMs that is effective, somewhat standardized, and generates the information required for targeting is needed. The objective of this paper is to present the results of the application such a methodology to the Cement Creek Basin in Colorado.

2 INFORMATION GOALS

Seven screening-level assessment information goals for targeting that are common to most LAM watersheds have been identified (Caruso, 1995):

1. Type and extent of water quality impairment and critical conditions.
2. Magnitudes of concentrations in and loadings to stream segments.
3. Differences between magnitudes of concentrations in and loadings to stream segments.
4. Frequency or risk of exceeding a target concentration in and loading to stream segments.
5. Areal extent and contaminant concentrations of NPSs.
6. Locations of loadings to and losses from stream segments.
7. Distances between sources and watercourses and impaired stream segments.

This paper addresses the first four information goals only. The uncertainty of or confidence in the data and information generated should also be evaluated and used in the assessment and targeting process.

3 DATA COLLECTION

Data have been collected from the Upper Animas River Basin above Silverton in the San Juan Mountains of southwestern Colorado by the Colorado Department of Public Health and Environment (CDPHE) as part of a NPS demonstration program grant (CWA Section 319) from the U.S. Environmental Protection Agency (USEPA) (CDPHE, 1992, 1993a). This basin is an historic metal mining district whose streams have been severely impacted by mine drainage. The watershed has an area of approximately 146 mi² and ranges in elevation from 9,200 feet to over 13,000 feet. Alpine tundra and Englemann spruce-fir forest are the dominant community types. The watershed is composed of three primary subbasins. The upper mainstem Animas River subbasin is the largest subbasin and is heavily impacted by past metal mining activities. Cement Creek joins the Animas River immediately above Silverton. Mineral Creek joins the Animas River immediately downstream from Silverton. This subbasin is also impacted by past metal mining activities, but not to the extent of the other two subbasins. The Cement Creek subbasin was the focus of this study because it is believed to be the most heavily impacted subbasin, and t...

Table of contents

• Cover Page
• Half-Title Page
• Title Page
• Copyright Page
• Table Of Contents
• Preface
• Introduction
• Regulatory considerations
• Design and operation
• Geotechnical considerations
• Liners, covers, barriers
• Groundwater and geochemistry
• Surface water quality and modelling
• Remediation and reclamation
• Reprocessing and utilization
• Case histories
• Author index