WATER QUALITY ASSESSMENT REPORT FOR UNITED KENO HILL MINES Report Prepared for: Elsa Reclamation and Development Company Whitehorse, Yukon Report Prepared by: Minnow Environmental Inc. 2 Lamb Street Georgetown, Ontario L7G 3M9 July 2008 WATER QUALITY ASSESSMENT REPORT FOR UNITED KENO HILL MINES Report Prepared for: Elsa Reclamation and Development Company Whitehorse, Yukon Report Prepared by: Minnow Environmental Inc. Cynthia Russel, B.Sc. Project Manager Patti Orr, M.Sc. Technical Reviewer July 2008 ERDC Water Quality Assessment EXECUTIVE SUMMARY United Keno Hill Mines Limited and UKH Minerals Ltd. were the previous owners of the properties located on and around Galena Hill, Keno Hill, and Sourdough Hill collectively known as the United Keno Hill Mining Property (UKHM). The UKHM is located in north- central Yukon Territory and is comprised of approximately 827 mineral claims covering the three mountains (“hills” named above) over an area of approximately 15,000 ha (about 29 km long and 8 km wide). Associated with the site are abandoned adits, buildings/structures, and waste material which represent a source of contaminants to the downstream watersheds. In June 2005, Alexco Resource Corp was selected as the preferred purchaser of the UKHM assets. Alexco’s subsidiary Elsa Reclamation and Development Company (ERDC) is required to develop a Reclamation Plan for the Existing State of the Mine. As part of the closure planning process, long-term water quality performance will need to be assessed relative to relevant water uses and closure plan options. It is expected that historical sources associated with the UKHM may not allow for generic water quality guidelines to be achieved at all downstream locations and that alternative targets may need to be developed, depending on water use goals. In order to identify the parameters and locations of concern at the UKHM site, ERDC retained Minnow Environmental Inc. to assess the water quality data available for creeks and rivers downstream of the various UKHM sources. Water quality data were compiled, evaluated and interpreted to identify parameters and locations of concern within the downstream waters relative to established guidelines and background. This information, combined with toxicity data and watershed use objectives, may then be use to develop an approach for water quality management, goals and objectives relative to identified water uses. All water quality data were downloaded from the water quality database developed and managed for the UKHM by Access Consulting Group. At the time the data were downloaded, sample results were available for the period up to June 2007. Water quality data for 20 stations were analyzed in detail, including stations located on permanent surface water courses located upstream (reference/background) and downstream (exposed) of mine- related disturbances or inputs (e.g., adits, roads, rock piles, buildings, etc.). Analytical data for most of the selected stations dated back to the mid-1980’s, however, sporadic data and poor method detection limits prior to 1994 limited the value of the older data and restricted the period of assessment to 1994-2007. Within this period, older data for some parameters was still hampered by inadequate analytical method detection limits and some data sets Minnow Environmental Inc. i July 2008 Project 2209 ERDC Water Quality Assessment were further truncated to the period mid-2004 - 2007. In total, analytical results corresponding to more than 2,000 individual data points were examined. The upper range of background concentrations of some parameters, including aluminum, cadmium, copper, iron, phosphorus, sulphate, and zinc, exceeded federal or alternative guidelines for protection of aquatic life. The concentrations of numerous parameters measured at stations within the various watersheds downstream of UKHM exceeded both the applicable guideline and background benchmark in at least 10% of samples. However, a much smaller set of parameters and locations showed elevations above both the guideline and background benchmark in 50% or more of samples (i.e., median value): aluminum, arsenic, cadmium, chromium, copper, iron, lead, manganese, nitrite, phosphorus, selenium, silver, sulphate, and zinc. These generally occurred in the tributaries located immediately downstream of mine sources (Christal Creek, Lightning Creek, Flat Creek and No Cash Creek). In no instance did the median concentration of any parameter exceed both the guideline and background benchmark at South McQuesten River stations. Contaminants of concern (COCs) were identified based on elevated frequency and magnitude of exceedance relative to both guideline or background (i.e., whichever value was higher); COCs were identified as cadmium and zinc. Other substances identified as having a high frequency and/or magnitude of exceedance above benchmarks (i.e., potential contaminants of concern; PCOCs): aluminum, arsenic, chromium, copper, manganese, nitrite, phosphorus, selenium and silver, lacked sufficient data and/or adequate analytical method detection limits at some or all stations to make a definitive conclusion regarding current risks to aquatic biota. Additional data need to be collected to determine if these substances should be considered mine-related COCs. There was also insufficient data (data for too few samples within and/or among locations) to make any assessment of mercury and cyanide concentrations, so these parameters also cannot be ruled out as COCs at this time. Statistically significant decreases in zinc over time were indicated at most stations, with the most substantial decrease occurring at Christal Creek station KV-29 and immediately downstream at KV-30 between 2004 and 2007. Since 2006, remediation and treatment of the Galena 300 adit (primary source captured at KV-29) has occurred, which will likely result in additional future improvements in zinc concentrations downstream of this source. While no trends in cadmium were detected, this is likely due to the short time frame assessed (mid- 2004 to 2007) relative to zinc (1994 to 2007). However, cadmium concentrations strongly correlated with zinc concentrations among stations, suggesting that cadmium concentrations have likely also decreased in Christal Creek over the same time period (1994 to 2007). Minnow Environmental Inc. ii July 2008 Project 2209 ERDC Water Quality Assessment Based on toxicity data available in the scientific literature, concentrations of the COCs are below effect thresholds within the South McQuesten River. However, it is likely that concentrations of cadmium and zinc in some tributary areas may periodically be high enough to cause toxicity to some species. Canadian water quality guidelines (CWQG) are currently being updated for cadmium and zinc, and conclusions presented herein should be revisited once available. However, even if the guidelines are raised somewhat, it is considered unlikely that water quality in tributaries immediately downstream of the UKHM discharges/sources will achieve these levels due to historical sources within the watershed. It is also expected that the development of site- specific water quality objectives (SSWQO) would be unlikely to result in values that could be achieved in these same areas, so an alternative approach for setting water quality expectations should be considered for these historically affected areas. It is expected that concentrations within the South McQuesten River downstream of the UKHM will continue to meet water quality guidelines or background benchmark. Minnow Environmental Inc. iii July 2008 Project 2209 ERDC Water Quality Assessment TABLE OF CONTENTS EXECUTIVE SUMMARY ..........................................................................................................I 1.0 INTRODUCTION..........................................................................................................1 1.1 Background ..............................................................................................................1 1.2 Study Objectives.......................................................................................................1 1.3 Approach ..................................................................................................................2 1.4 Canadian Water Quality Guideline (CWQG) Updates..............................................3 1.5 Report Organization .................................................................................................3 2.0 METHODS....................................................................................................................4 2.1 Data Base Used in Water Quality Assessment ........................................................4 2.2 Data screening .........................................................................................................4 2.2.1 Guidelines.........................................................................................................4 2.2.2 Background Concentrations .............................................................................6 2.2.3 Receiving Environment Data Evaluation ..........................................................8 2.3 Identification of COCs...............................................................................................9 2.4 Total Versus Dissolved Concentrations..................................................................10 2.5 Temporal Trend Analysis for COCs........................................................................10 2.6