Statistical Analysis of Post-Phase I Remedial Action Water Quality Data Operable Unit 2

Transcription

1 Final Statistical Analysis of Post-Phase I Remedial Action Water Quality Data Operable Unit 2 Bunker Hill Mining and Metallurgical Complex Superfund Site Prepared for U.S. Environmental Protection Agency Region 10 January 2006 AES10 Architect and Engineering Services Contract Contract No. 68-S Prepared by Ecology and Environment, Inc. SPK\

2 Acronyms and Abbreviations ANOVA ARAR AWQC CCP CERCLA CIA CSM EMP EPA ICP IDEQ IDHW MCL MDL mg/l O&M OU2 OU2 EMP PRP PWWTP RAMP RI analysis of variance Applicable or relevant and appropriate requirement ambient water quality criteria Comprehensive Cleanup Plan Comprehensive Environmental Response, Compensation, and Liability Act Central Impoundment Area Conceptual Site Model Environmental Monitoring Plan U.S. Environmental Protection Agency Institutional Controls Program Idaho Department of Environmental Quality Idaho Department of Health and Welfare maximum contaminant level method detection limit Milligrams per liter operations and maintenance Operable Unit 2 of the Bunker Hill Mine and Metallurgical Complex Superfund Site OU2 Environmental Monitoring Plan potentially responsible party Page Wastewater Treatment Plant Remedial Action Management Plan remedial investigation ROD Record of Decision [1992] SACA SCA SFCDR Support Agency Cooperative Agreement Smelter Closure Area South Fork Coeur d Alene River SPK\ iii

3 ACRONYMS AND ABBREVIATIONS SPLOM SSC ug/l us/cm USGS scatter plot matrix State Superfund Contract micrograms per liter microsiemens per centimeter U. S. Geological Survey

4 Executive Summary This document presents a statistical analysis and evaluation of water quality monitoring data collected within Operable Unit 2 (OU2) of the Bunker Hill Mining and Metallurgical Complex Superfund Site following the implementation of Phase I remedial actions. This document is a companion document to the Current Status Conceptual Site Model for OU2 (CSM) (CH2M HILL, 2006a) and the OU2 Environmental Monitoring Plan (OU2 EMP) (CH2M HILL, 2006b). This statistical analysis and evaluation provides an evaluation of water quality status and trends following the implementation of Phase I remedial actions and provides a framework for future analyses of water quality data collected within OU2. Water quality monitoring has been conducted within OU2 from 1987 to the present. Three time periods representing different physical and contaminant conditions were evaluated, as follows: 1987 to 1994 Remedial Investigation and Design (characterization monitoring) 1994 to 2000 Phase I Remedial Action Implementation (detection monitoring) 2000 to 2004 Post-Phase I Remedial Action Implementation (effectiveness monitoring) The post-phase I remedial action implementation time period best represents water quality and trends attributable to the implementation of Phase I remedial actions and evaluation of these actions toward meeting water quality objectives for OU2. The statistical evaluation methodologies included comparing monitoring results to water quality criteria (exceedence), noting correlations between monitoring parameters, and performing an evaluation of trend using the Mann-Kendall test. The Mann-Kendall test is a non-parametric test for the detection of trends in time series data. The Mann-Kendall test is widely used in environmental science because it is simple, robust, and can cope with missing values and values below detection limits (Libiseller and Grimvall, 2002). Both groundwater and surface water monitoring data collected between April 2000 and October 2004 were evaluated. The focus of the evaluation was on groundwater, with surface water as an ancillary component of the groundwater evaluation. Both the full period of record monitoring results (1987 to 2004) and the post-phase I remedial action implementation monitoring results were evaluated. Results and conclusions presented in this document are focused on the post-phase I remedial action implementation period (2000 to 2004). Water quality results for exceedence and trends at each monitoring location were evaluated geospatially for the monitoring network and with respect to the hydrogeologic site conceptual model. The results of the evaluation are summarized by the methodologies used, and are as follows: Dissolved metals in groundwater were evaluated against maximum contaminant levels (MCLs) to determine the frequency of MCL exceedence. The MCL was exceeded most often by cadmium, followed by zinc, arsenic, lead and antimony (Table ES-1). SPK\ ES-1

5 ACRONYMS AND ABBREVIATIONS Dissolved cadmium (Figure ES-1) and dissolved zinc exceeded their respective MCLs at a relatively high frequency in the upper aquifer throughout OU2 with the exception of the eastern and western boundaries of the site. Dissolved lead and dissolved arsenic (Figure ES-2) MCLs were most frequently exceeded in Government Gulch and in the upper aquifer near the Central Impoundment Area (CIA) and Page Ponds. Dissolved antimony exceeded the MCL at relatively low frequencies throughout OU2. The distribution of dissolved cadmium (Figure ES-1) and zinc MCL exceedence frequencies in the lower aquifer suggest that a preferential flow pathway may be present in the southern portion of the lower aquifer. Groundwater quality parameter correlations were observed and are summarized as follows: A strong correlation between dissolved cadmium and dissolved zinc and to a lesser extent between dissolved arsenic and dissolved lead were observed. A correlation was indicated between ph and dissolved arsenic and to a lesser degree dissolved cadmium and dissolved zinc. A correlation between conductivity and the parameters dissolved cadmium and dissolved zinc was present. Groundwater quality trends associated with post-phase I remedial actions are summarized as follows: Decreasing or not significant (confidence interval less than 95 percent) trends were determined for dissolved metals in all except two wells; one with an increasing dissolved cadmium trend (Figure ES-3) and the other an increasing dissolved zinc trend (Figure ES-4). The increasing dissolved cadmium trend occurred at monitoring well BH-SF-W U, completed in the tailings material of the Page Ponds tailings impoundment. The increasing dissolved zinc trend occurred at monitoring well BH-SF-E-0321-U, located in the upper aquifer between the CIA and the South Fork Coeur d Alene River (SFCDR). Surface water parameters were evaluated for frequency of ambient water quality criteria (AWQC) exceedence for the post-phase I remedial actions time period, and are summarized as follows: In general, dissolved metals exceed AWQC at relatively high frequencies throughout OU2 (Table ES-2). Lack of sufficient monitoring data limited the applicability of determining correlations and trends; however, extensive work is being conducted to develop methods of analysis for surface water monitoring locations within the Coeur d Alene

6 River Basin as part of the OU3 Basin Environmental Monitoring Plan (EPA, 2004) and will implemented within OU2. Based on the results and lessons learned during the performance of this statistical analysis and evaluation, the following conclusions and recommendations have been developed regarding future monitoring data collection and statistical analysis: Post-Phase I remedial action groundwater monitoring results indicate that the OU2 Phase I source removal and containment actions have generally resulted in downward dissolved metal contaminant concentrations, but concentrations continue to frequently exceed the MCLs. Post-Phase I surface water monitoring results indicate that dissolved metal concentrations continue to frequently exceed AWQC throughout OU2. Monitoring well hydrographs indicate past inconsistent and noncoincident sampling of groundwater monitoring locations, which limits the utility of the data for statistical evaluation. Consistent and coincident surface water and groundwater monitoring and placement of groundwater monitoring locations adjacent to surface water monitoring locations would improve comparison and statistical evaluation for surface water and groundwater quality. Events should coincide with SFCDR base-flow and high-flow surface water events. Surface water method detection limits (MDLs) were found to be greater than AWQC for several monitoring parameters. This limited the ability to analyze surface water monitoring data with respect to AWQC. Revised MDLs for surface water monitoring parameters are needed to improve analysis of these parameters. Continued groundwater and surface water monitoring is recommended to refine the ability to track trends over time and to increase the post-phase I remedial action data set to develop time-dependant estimates for achieving remedial action objectives through regression analyses. Based on the results to date, the OU2 Environmental Monitoring Plan has been developed and includes streamlined monitoring activities to assess long-term status and trends of OU2 groundwater and surface water, and to provide data required for future Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) required five-year reviews.

7 TABLE ES-1 Groundwater Parameter MCL Exceedence OU2 Statistical Analysis Bunker Hill Superfund Site OU2 Range of Exceedence Frequency within a Well Range of Detected Concentrations Parameter (dissolved) Exceedence (# of wells [% of all wells]) Minimum (%) Maximum (%) Mean (%) Minimum (µg/l) Maximum (µg/l) Mean (µg/l) MCL (µg/l) Cadmium 68 [81%] , Zinc 47 [58%] ,000 7,820 5,000 a Arsenic 47 [58%] Lead 21 [2] Antimony 5 [] a Secondary MCL CH2M HILL

8 TABLE ES-2 Surface Water Parameter AWQC Exceedence OU2 Statistical Analysis Bunker Hill Superfund Site OU2 Range of Exceedence Frequency at a Station Range of Detected Concentrations Parameter Exceedence (# of stations Minimum (%) Maximum (%) Mean (%) Minimum (µg/l) [% of all Maximum (µg/l) stations]) Zinc (dissolved) 13 [] ,500 Cadmium (dissolved) 13 [] Lead (total) 13 [] ,180 Arsenic (dissolved) 12 [] CH2M HILL

9 UPPER AQUIFER BH-SF-W-0203-U 7% BH-SF-W-0201-U 33% BH-SF-W-0120-U 8% BH-SF-W-0118-U BH-SF-W-0119-U BH-SF-W-0121-U 11% BH-SF-W-0104-U BH-SF-W-0108-U BH-SF-W-0111-U BH-SF-W-0113-U 59% BH-SF-W-0018-U 17% BH-SF-W-0008-U 90% BH-SF-W-0009-U BH-SF-W-0010-U BH-SF-W-0019-U BH-SF-W-0001-U BH-SF-E-0502-U 9 BH-SF-E-0503-U BH-SF-E-0504-U BH-SF-W-0003-U BH-GG-GW-0007 BH-GG-GW % BH-GG-GW-0005 BH-SF-W-0007-U BH-SF-W-0005-U 78% BH-SCA-GW-0002 BH-SF-E-0429-U 98% BH-SF-E-0425-U BH-SF-E-0423-U 21% BH-SF-E-0427-U BH-SCA-GW-0005 BH-SCA-GW-0006 BH-SF-E-0501-U BH-SF-E-0403-U 40% BH-SF-E-0402-U 9 BH-SF-E-0407-U BH-SF-E-0408-U BH-SF-E-0409-U BH-SF-E-0410-U BH-DW-GW % BH-SF-E-0321-U 9 BH-SF-E-0322-U BH-SF-E-0317-U 7 BH-SF-E-0318-U BH-SF-E-0314-U 78% BH-SF-E-0315-U 2 BH-SF-E-0309-U BH-SF-E-0316-U 57% BH-SF-E-0305-U BH-SF-E-0301-U BH-SF-E-0201 BH-GG-GW-0004 BH-SF-E-0320-U BH-GG-GW-0003 BH-SF-E-0101 BH-SF-E-0003 BH-GG-GW-0002 LOWER AQUIFER BH-SF-W-0122-L BH-SF-W-0115-L 94% BH-SF-E-0424-L BH-SF-E-0426-L BH-SF-W-0004-L BH-SF-E-0428-L BH-SF-W-0011-L BH-SF-E-0306-L BH-SF-E-0302-L NOTE: Data gathered between April 2000 and May Legend 1-2 Exceedence Water Features 26-50% Exceedence 51-7 Exceedence FIGURE ES-1 DISSOLVED CADMIUM FREQUENCY OF MCL EXCEEDENCE IN GROUNDWATER OU2 STATISTICAL ANALYSIS BUNKER HILL SUPERFUND SITE OU2 76- Exceedence 0 3,000 6,000 Feet File Path: Z:\USEnvironmentalProte\321104\GIS\MapDocuments\Mxds\Trend Analysis\Figure ES-1.mxd, Date: January 16, :50:32 PM

10 UPPER AQUIFER BH-SF-W-0203-U 7% BH-SF-W-0018-U BH-SF-W-0121-U BH-SF-W-0118-U BH-SF-W-0119-U 50% BH-SF-W-0113-U 3 BH-SF-W-0114-U 91% BH-SF-W-0111-U 9 BH-SF-W-0008-U BH-SF-W-0009-U BH-SF-W-0010-U BH-SF-E-0503-U 7% BH-SF-W-0003-U 17% BH-SF-E-0502-U BH-SF-E-0429-U 98% BH-SF-E-0504-U 12% BH-SF-E-0425-U 83% BH-SF-E-0501-U 3% BH-SCA-GW % BH-SF-E-0423-U BH-SF-E-0427-U 97% BH-SF-E-0403-U BH-SF-E-0402-U BH-SF-E-0321-U BH-SF-E-0322-U 20% BH-SF-E-0407-U BH-SF-E-0409-U BH-SF-E-0410-U 3% BH-SF-E-0317-U BH-SF-E-0318-U 14% BH-SF-E-0315-U BH-SF-E-0314-U BH-SF-W-0019-U BH-SCA-GW % BH-SF-E-0320-U BH-GG-GW BH-SCA-GW % BH-SF-E-0003 BH-GG-GW-0002 BH-GG-GW % LOWER AQUIFER BH-SF-W-0122-L BH-SF-W-0115-L BH-SF-W-0011-L BH-SF-W-0004-L 17% BH-SF-W-0006-L 33% BH-SF-E-0424-L 2 BH-SF-E-0426-L NOTE: Data gathered between April 2000 and May Legend 1-2 Exceedence Water Features 26-50% Exceedence 51-7 Exceedence FIGURE ES-2 DISSOLVED ARSENIC FREQUENCY OF MCL EXCEEDENCE IN GROUNDWATER OU2 STATISTICAL ANALYSIS BUNKER HILL SUPERFUND SITE OU2 76- Exceedence 0 3,000 6,000 Feet File Path: Z:\USEnvironmentalProte\321104\GIS\MapDocuments\Mxds\Trend Analysis\Figure ES-2.mxd, Date: January 16, :52:49 PM

11 UPPER AQUIFER BH-SF-W-0018-U BH-SF-E-0423-U BH-SF-E-0403-U BH-SF-E-0402-U BH-SF-E-0321-U BH-SF-W-0104-U BH-SF-W-0108-U BH-SF-W-0008-U BH-SF-W-0009-U BH-SF-E-0502-U BH-SF-E-0429-U BH-SF-E-0504-U BH-SF-E-0503-U BH-SF-E-0501-U BH-SF-E-0317-U BH-SF-E-0315-U BH-SF-E-0314-U BH-SF-W-0113-U BH-SF-E-0427-U BH-SF-W-0010-U BH-SF-W-0005-U BH-SCA-GW-0005 BH-SF-E-0410-U BH-SCA-GW-0006 BH-GG-GW-0005 BH-SF-E-0320-U BH-SF-E-0201 BH-SCA-GW-0002 BH-DW-GW-0001 BH-SF-E-0301-U BH-GG-GW-0004 BH-SF-E-0101 BH-GG-GW-0003 BH-GG-GW-0002 LOWER AQUIFER BH-SF-W-0205-L BH-SF-W-0115-L BH-SF-W-0011-L BH-SF-E-0302-L NOTE: Data gathered between April 2000 and May Legend Increasing Trend Decreasing Trend No Significant Trend Water Features 0 3,000 6,000 Feet FIGURE ES-3 DISSOLVED CADMIUM TRENDS IN GROUNDWATER OU2 STATISTICAL ANALYSIS BUNKER HILL SUPERFUND SITE OU2 File Path: Z:\USEnvironmentalProte\321104\GIS\MapDocuments\Mxds\Trend Analysis\Figure ES-3.mxd, Date: January 16, :58:55 PM

12 UPPER AQUIFER BH-SF-W-0203-U BH-SF-W-0121-U BH-SF-W-0120-U BH-SF-W-0104-U BH-SF-W-0108-U BH-SF-W-0111-U BH-SF-W-0018-U BH-SF-W-0008-U BH-SF-W-0009-U BH-GG-GW-0005 BH-GG-GW-0006 BH-SF-E-0502-U BH-SF-E-0503-U BH-SF-E-0429-U BH-SF-E-0423-U BH-SF-E-0403-U BH-SF-E-0402-U BH-SF-E-0321-U BH-SF-E-0501-U BH-SF-E-0317-U BH-SF-E-0315-U BH-SF-E-0314-U BH-SF-W-0113-U BH-SF-E-0427-U BH-SF-W-0010-U BH-SF-W-0005-U BH-SF-E-0410-U BH-SF-W-0019-U BH-SCA-GW-0005 BH-SCA-GW-0006 BH-SCA-GW-0007 BH-SCA-GW-0002 BH-DW-GW-0001 BH-SF-E-0320-U BH-SF-E-0301-U BH-SF-E-0201 BH-GG-GW-0004 BH-SF-E-0101 BH-GG-GW-0003 BH-GG-GW-0002 BH-GG-GW-0001 LOWER AQUIFER BH-SF-W-0205-L BH-SF-W-0122-L BH-SF-W-0115-L BH-SF-W-0011-L BH-SF-E-0302-L NOTE: Data gathered between April 2000 and May Legend Increasing Trend Decreasing Trend No Significant Trend Water Features 0 3,000 6,000 Feet FIGURE ES-4 DISSOLVED ZINC TRENDS IN GROUNDWATER OU2 STATISTICAL ANALYSIS BUNKER HILL SUPERFUND SITE OU2 File Path: Z:\USEnvironmentalProte\321104\GIS\MapDocuments\Mxds\Trend Analysis\Figure ES-4.mxd, Date: January 16, :55:05 PM