Long-Term Monitoring Network
Optimization Evaluation
for
Operable Unit 2
Bunker Hill Mining and Metallurgical
Complex Superfund Site
Idaho
3»
January 2006
-------
Solid Waste and EPA 542-R-06-005
Emergency Response December 2006
(5102P) www.epa.gov
Long-Term Monitoring Network
Optimization Evaluation
for
Operable Unit 2
Bunker Hill Mining and Metallurgical Complex
Superfund Site
Idaho
January 2006
-------
FINAL
LONG-TERM MONITORING NETWORK
OPTIMIZATION EVALUATION
FOR
OPERABLE UNIT 2
BUNKER HILL MINING AND METALLURGICAL COMPLEX
SUPERFUND SITE
IDAHO
January 2006
-------
TABLE OF CONTENTS
Page
SECTION 1 INTRODUCTION 1-1
SECTION 2 SITE BACKGROUND INFORMATION 2-1
2.1 Site Location and Operational History 2-1
2.2 Environmental Setting 2-4
2.2.1 Geology 2-4
2.2.2 Hydrogeology 2-4
2.2.3 Surface Water Hydrology 2-5
2.3 Nature and Extent of Contamination 2-5
SECTIONS LONG-TERM MONITORING PROGRAM AT OU2 3-1
3.1 Description of Monitoring Program 3-1
3.2 Summary of Analytical Data 3-8
SECTION 4 QUALITATIVE LTMO EVALUATION 4-1
4.1 Method for Qualitative Evaluation of Monitoring Network 4-2
4.2 Results of Qualitative LTMO Evaluation for Groundwater 4-3
4.2.1 Single Unconfmed Aquifer 4-3
4.2.2 Upper Alluvial Sand and Gravel Aquifer 4-9
4.2.3 Lower Alluvial Sand and Gravel Aquifer 4-11
4.2.4 Upland Aquifer 4-12
4.3 Results of Qualitative LTMO Evaluation for Surface Water 4-13
4.4 Laboratory Analytical Program 4-16
4.5 Data Gaps 4-17
4.6 LTM Program Flexibility 4-19
SECTION 5 TEMPORAL STATISTICAL EVALUATION 5-1
5.1 Methodology for Temporal Trend Analysis of Contaminant Concentrations 5-1
5.2 Temporal Evaluation Results for Groundwater Wells 5-4
5.3 Temporal Evaluation Results for Surface Water Stations 5-12
SECTION 6 SPATIAL STATISTICAL EVALUATION 6-1
6.1 Geostatistical Methods for Evaluating Monitoring Networks 6-1
6.2 Spatial Evaluation of the Monitoring Network at OU2 6-3
6.3 Spatial Statistical Evaluation Results 6-5
SECTION 7 SUMMARY OF LONG-TERM MONITORING
OPTIMIZATION EVALUATION 7-1
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TABLE OF CONTENTS (Continued)
Page
7.1 Groundwater Monitoring Network Summary 7-1
7.2 Surface Water Monitoring Network Summary 7-8
SECTIONS REFERENCES 8-1
APPENDICES
A Supporting Figures from the Draft OU2 Conceptual Site Model Report
(CH2M Hill, 2005a)
B Comments and Responses on Draft Report
LIST OF TABLES
No. Title Page
3.1 Basecase Groundwater Monitoring Program 3-2
3.2 Basecase Surface Water Monitoring Program 3-5
3.3 Summary of Occurrence of Groundwater Contaminants of Concern 3-9
3.4 Summary of Occurrence of Surface Water Contaminants of Concern 3-10
3.5 Most Recent Groundwater COC Concentrations 3-15
3.6 Most Recent Surface Water COC Concentrations 3-18
4.1 Monitoring Network Optimization Decision Logic 4-2
4.2 Monitoring Frequency Decision Logic 4-3
4.3 Qualitative Evaluation of Groundwater Monitoring Network 4-4
4.4 Qualitative Evaluation of Surface Water Monitoring Network 4-14
5.1 Temporal Trend Analysis of Groundwater Monitoring Results 5-8
5.2 Temporal Trend Analysis of Surface Water Monitoring Results 5-13
6.1 Best-Fit Semivariogram Model Parameters 6-4
6.2 Results of Geostatistical Evaluation Ranking of Wells by Relative Value of
Zinc in the Upper HU 6-7
6.3 Results of Geostatistical Evaluation Ranking of Wells by Relative Value of
Cadmium in the Upper HU 6-8
6.4 Results of Geostatistical Evaluation Ranking of Wells by Relative Value of
Zinc in the Lower HU 6-9
6.5 Summary Results of Geostatistical Evaluation Ranking of Wells by Relative
Value of Cadmium and Zinc in the Upper HU 6-14
7.1 Summary of Long Term Monitoring Optimization Evaluation of the OU2
Groundwater Monitoring Program 7-2
7.2 Summary of Revised and Basecase Monitoring Programs 7-8
7.3 Summary of Long-term Monitoring Optimization Evaluation of Surface
Water Monitoring Program 7-9
-11-
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TABLE OF CONTENTS (Continued)
LIST OF FIGURES
No. Title Page
2.1 OU2 Site Features 2-2
3.1 Groundwater Monitoring Wells 3-6
3.2 Surface Water Monitoring Points 3-7
3.3 Most Recent Dissolved Arsenic Concentrations in Groundwater 3-11
3.4 Most Recent Dissolved Cadmium Concentrations in Groundwater 3-12
3.5 Most Recent Dissolved Lead Concentrations in Groundwater 3-13
3.6 Most Recent Dissolved Zinc Concentrations in Groundwater 3-14
3.7 Most Recent Arsenic in Surface Water 3-19
3.8 Most Recent Cadmium in Surface Water 3-20
3.9 Most Recent Lead in Surface Water 3-21
3.10 Most Recent Zinc in Surface Water 3-22
4.1 Qualitative Evaluation Sampling Frequency Recommendations for
Groundwater Wells 4-7
5.1 Zinc Concentrations Through Time at Well BH-GG-GW-0004 5-2
5.2 Conceptual Representation of Temporal Trends and Temporal Variations
in Concentrations 5-3
5.3 Conceptual Representation of Continued Monitoring at Location Where
No Temporal Trend in Concentrations is Present 5-5
5.4 Temporal Trend Decision Rationale Flowchart 5-6
5.5 Temporal Trend Results for Cadmium in Groundwater 5-10
5.6 Temporal Trend Results for Zinc in Groundwater 5-11
6.1 Idealized Semivariogram Model 6-3
6.2 Impact of Missing Wells on Predicted Standard Error 6-6
6.3 Geostatistical Evaluation Results Showing Relative Value of Spatial
Information on Zinc Distribution, Upper HU Wells 6-10
6.4 Geostatistical Evaluation Results Showing Relative Value of Spatial
Information on Cadmium Distribution, Upper HU Wells 6-11
6.5 Geostatistical Evaluation Results Showing Relative Value of Spatial
Information on Zinc Distribution, Lower HU Wells 6-12
7.1 Combined Evaluation Sampling Frequency Recommendations For
Groundwater Wells 7-5
7.2 Combined Evalution Summary Decision Logic 7-6
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LIST OF ACRONYMS
AWQC
bgs
Bunker Hill
CIA
CLP
COC
COV
CSM
BMP
ESRI
ft/day
ft/ft
GIS
HU
LTM
LTMO
MCL
MNO
ND
OU
PQL
RAO
ROD
SCA
SFCDR
USEPA
ambient water quality criteria
below ground surface
Bunker Hill Mining and Metallurgical Complex Superfund Site
Central Impoundment Area
Contract Laboratory Program
contaminant of concern
coefficient of variation
conceptual site model
Environmental Monitoring Plan
Environmental Systems Research Institute, Inc.
foot per day
foot per foot
geographical information system
hydrostratigraphic unit
long-term monitoring
long-term monitoring optimization
microgram(s) per liter
maximum contaminant level
monitoring network optimization
not detected
Operable Unit
practical quantitation limit
remedial action objective
Record of Decision
Smelter Closure Area
South Fork Coeur d'Alene River
United States Environmental Protection Agency
-IV-
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SECTION 1
INTRODUCTION
Groundwater monitoring programs typically have two primary objectives (U.S.
Environmental Protection Agency [USEPA], 1994; Gibbons, 1994):
1. Evaluate long-term temporal trends in contaminant concentrations at one or
more points within or outside the remediation zone as a means of monitoring
the performance of the remedial measure (temporal objective) and
2. Evaluate the extent to which contaminant migration is occurring, particularly if
a potential exposure point for a susceptible receptor exists (spatial objective}.
The relative success of any remediation system and its components (including the
monitoring network) must be judged based on the degree to which it achieves the stated
objectives of the system. Designing an effective groundwater monitoring program
involves locating monitoring points and developing a site-specific strategy for
groundwater sampling and analysis to maximize the amount of relevant information that
can be obtained while minimizing incremental costs. Relevant information is that
required to effectively address the temporal and spatial objectives of monitoring. The
effectiveness of a monitoring network in achieving these two primary objectives can be
evaluated quantitatively using statistical techniques. In addition, there may be other
important considerations associated with a particular monitoring network that are most
appropriately addressed through a qualitative assessment of the network. The qualitative
evaluation may consider such factors as hydrostratigraphy, locations of potential receptor
exposure points with respect to a dissolved contaminant plume, and the direction(s) and
rate(s) of contaminant migration.
This report presents a description and evaluation of the groundwater and surface water
monitoring program associated with the Bunker Hill Mining and Metallurgical Complex
Superfund Site (Bunker Hill) Operable Unit (OU) 2. A monitoring network consisting of
77 groundwater monitoring wells and 18 surface water stations was evaluated to assess
its overall effectiveness at achieving the OU2-specific monitoring objectives, and to (1)
identify potential opportunities to streamline monitoring activities while still maintaining
an effective monitoring program, and (2) identify data gaps that may require the addition
of additional monitoring points. A three-tiered approach, consisting of a qualitative
evaluation, a statistical evaluation of temporal trends in contaminant concentrations, and
a spatial statistical analysis (groundwater only), assessed the degree to which the
monitoring network addresses the objectives of the monitoring program, as well as other
important considerations. The results of the three evaluations were combined and used to
assess the optimal frequency of monitoring and the spatial distribution of the components
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of the monitoring network. The results of the analysis were then used to develop
recommendations for optimizing the monitoring program at OU2.
1-2
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SECTION 2
SITE BACKGROUND INFORMATION
The location, operational history, environmental setting (i.e., geology, hydrogeology,
and surface water hydrology), and remediation history of OU2 are briefly summarized in
the following subsections. These topics are discussed in detail in the draft OU2
conceptual site model (CSM) report (CH2M Hill, 2005a), which is the primary source of
the information presented below.
2.1 SITE LOCATION AND OPERATIONAL HISTORY
Bunker Hill Mining and Metallurgical Complex Superfund Site is within one of the
largest historical mining districts in the world. Commercial mining for lead, zinc, silver,
and other metals began in this portion of the Coeur d'Alene River Basin (known as the
"Silver Valley") in 1883. Heavy metals contamination in soil, sediment, surface water,
and groundwater from over 100 years of commercial mining, milling, smelting and
associated modes of transportation has impacted both human health and environmental
resources in many areas throughout the site.
The Bunker Hill Superfund Site was listed on the National Priorities List in 1983. The
Site includes mining-contaminated areas in the Coeur d'Alene River corridor, adjacent
floodplains, downstream water bodies, tributaries, and fill areas, as well as the 21-square
mile Bunker Hill "Box" located in the area surrounding the historic smelting operations.
The USEPA has designated three OUs for the Site:
• The populated areas of the Bunker Hill Box (OU1),
• The non-populated areas of the Bunker Hill Box (OU2), and
• Mining-related contamination in the broader Coeur d'Alene Basin (OU3).
OU2 of the Bunker Hill Mining and Metallurgical Complex Superfund Site is the
focus of this report and consists of the non-populated areas of a rectangular 7-mile by 3-
mile area known as the Bunker Hill "Box" with the exception of the South Fork Coeur
d'Alene River (SFCDR) and the Pine Creek drainage (see Figure 2.1 of this report and
Figures 2-1 and 2-2 of the draft CSM report [CH2M Hill, 2005a] which are included in
Appendix A). The populated areas of the Bunker Hill Box and the SFCDR/Pine Creek
drainage are included in OU1 and OU3, respectively.
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South Fork Coeur
d'Alene River
I--'
.Pinehust Narrows
*^ WVest Page Swamp
Smelterville Flats
East Page
Swamp
o
v£
' - ' «. *
0 1,2502,500
5,000
7,500
10,000
1 inch equals 2,500 feet
Legend
_! Main Valley Alluvial Aquifer
Upland Tributary Alluvial Aquifers
Lower Aquifer Confining Unit
(Eastern Extent)
FIGURE 2.1
OU2 SITE FEATURES
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
2-2
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Fifty-two mines and mine-related sites were identified within OU2. The primary ores
mined during the early stages of mining activity were galena (a source of lead and silver)
and tetrahedrite (a source of silver). Later stages of mining activity also targeted
sphalerite (a source of zinc that also contained manganese, cadmium, and other metals).
Mining activities began in 1885 and large-scale mining operations within OU2 ceased in
1991. Small-scale operations are still ongoing at the Bunker Hill Mine and several other
mines are still in operation upstream of OU2.
The draft CSM report (CH2M Hill, 2005a) states that "the long history of mining
activities within and upstream of the Bunker Hill site, combined with the dynamic and
complex hydrologic system and anthropogenic effects to that system, have resulted in
widespread and commingled sources of contamination." For example, mine tailings
generated in OU2 were, for many years, deposited directly to the SFCDR, its tributaries,
and their associated floodplains, resulting in wide dispersal of tailings throughout the
valley floor within OU2. Anthropogenic and natural processes have resulted in the
mixing of the tailings with the underlying natural alluvium (e.g., to depths of up to 15
feet in portions of Smelterville Flats). According to the draft CSM report (CH2M Hill,
2005a), historical events left a layer of tailings mixed with alluvium generally 4 to 7 feet
thick across the majority of OU2. In addition, tailings, tailings mixtures, and mine waste
rock were used as fill in construction projects throughout OU2 over time (e.g., towns,
industrial facilities, railroad grades, and road grades).
The OU2 Record of Decision (ROD) issued in 1992 set forth priority cleanup actions
to protect human health and the environment. Cleanup actions included a series of source
removals, surface capping, reconstruction of surface water creeks, demolition of
abandoned milling and processing facilities, engineered closures for waste consolidated
onsite, revegetation efforts, and treatment of contaminated water collected from various
site sources.
In 1995, with the bankruptcy of the Site's major Potentially Responsible Party, the
USEPA and the State of Idaho defined a path forward for phased remedy implementation
in OU2. Phase I of remedy implementation includes extensive source removal and
stabilization efforts, all demolition activities, all community development initiatives,
development and initiation of an institutional controls plan, future land use development
support, and public health response actions. Also included in Phase I are additional
investigations to provide the necessary information to resolve long-term water quality
issues, including technology assessments and pilot studies, evaluation of the success of
source control efforts, development of site-specific water quality and effluent-limiting
performance standards, and development of a defined operation and maintenance plan
and implementation schedule. Interim control and treatment of contaminated water and
acid mine drainage is also included in Phase I of remedy implementation. Phase I
remediation began in 1995, and source control and removal activities are near
completion.
Phase II of the OU2 remedy will be implemented following completion of source
control and removal activities and evaluation of the impacts of these activities on meeting
water quality improvement objectives. Phase II will consider any shortcomings
encountered in implementing Phase I and will specifically address long-term water
quality and environmental management issues. The evaluation of the effectiveness of the
2-3
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Phase I source control and removal activities at meeting the water quality improvement
objectives outlined in the 1992 OU2 ROD will be used to determine appropriate Phase II
implementation strategies and actions.
2.2 ENVIRONMENTAL SETTING
2.2.1 Geology
This brief summary focuses on the thick sequence of unconsolidated deposits
overlying bedrock within OU2, given that all of the groundwater monitoring wells
evaluated are screened within these deposits. An east-west-oriented longitudinal
geologic cross-section, shown on Figure 3-8 of the draft CSM report (CH2M Hill,
2005a), aids in the visualization of the stratigraphic units described in this subsection.
The location of this cross-section is depicted on Figure 3-7 of the CSM report; both
figures are included in Appendix A.
The primary stratigraphic units that are relevant to this monitoring network
optimization (MNO) evaluation include an upper alluvial sand and gravel unit, a
lacustrine silt/clay unit that underlies the upper sand and gravel, and lower sand and
gravel unit that underlies the silt/clay. The lacustrine silt/clay that separates the upper
and lower sand and gravel units is present throughout the central and western portions of
OU2; this unit thins to the east and is not present in the eastern portion of OU2, most
likely starting between Milo and Portal Gulches (see Figure 2.1).
Sedimentary deposits in the upland tributary gulches are highly variable in
composition and consist of coarse-grained deposits (i.e.., sand and gravel) that were
deposited in higher-energy depositional environments and a heterogeneous mixture of
fine- to coarse-grained colluvium and slope-wash materials. Transitional depositional
environments are found predominantly near the mouths of gulches and along the main
valley/hillside interface. These transitional deposits consist of a mixture of colluvial and
slopewash materials intermixed with main valley alluvial sediments.
2.2.2 Hydrogeology
The primary groundwater-bearing units of concern in the MNO evaluation include the
upper and lower alluvial sand and gravel units present beneath the main SFCDR valley
and the upland tributary colluvial/alluvial unit that is associated with the hillsides and
gulches that discharge to the main SFCDR valley groundwater system. The upper
alluvial sand and gravel aquifer is mostly unconfined and is perched on top of the
lacustrine silt/clay unit, which acts as an aquitard. However, the upper aquifer may be
locally confined where it is overlain by a relatively fine-grained mixture of alluvium and
tailings. The thickness of this upper aquifer ranges from less than 10 feet near the valley
walls to nearly 40 feet. The lower alluvial sand and gravel aquifer is confined by the
overlying lacustrine silt/clay aquitard, and ranges from 20 to 40 feet in thickness. In the
eastern portion of OU2, where the aquitard is not present, the upper and lower sand and
gravel units are combined into a single thick (up to 60 feet) unconfined alluvial aquifer.
The depth to the water table generally ranges from approximately 8 to 10 feet below
ground surface (bgs) in the eastern portion of OU2 to approximately 10 to 25 feet bgs in
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the central and western portions; however some variability exists. Water table elevations
fluctuate seasonally due to temporal variations in precipitation and snowmelt.
As indicated on Figures 3-37 through 3-40 of the draft CSM report (CH2M Hill,
2005a) (Appendix A), regional groundwater flow in the main SFCDR valley is generally
from east to west, although local variations in flow direction (e.g., either toward or away
from major surface water drainages due to the presence of gaining and losing reaches)
exist. The geometric mean hydraulic conductivity values for the upper and lower alluvial
sand and gravel aquifers beneath the SFCDR valley, derived from single-well aquifer
tests performed by CH2M Hill and reported in 'Single Well Pumping Test Methods and
Results (CH2M Hill, 2004), are 103 feet per day (ft/day) and 117 ft/day, respectively.
The geometric mean hydraulic conductivity value for the upland tributary aquifer is 5.6
ft/day. The average hydraulic gradient in the upper and lower alluvial sand and gravel
aquifers, measured across the Bunker Hill Box, is 0.0046 foot per foot (ft/ft) (CH2M Hill,
2005a). Government Gulch is the only upland tributary aquifer with sufficient
monitoring wells to allow calculation of a hydraulic gradient. The measured average
hydraulic gradient in the upland aquifer along the length of Government Gulch, derived
from groundwater elevation maps contained in the draft CSM report (CH2M Hill, 2005a,
see Appendix A), is 0.054 ft/ft. Using the above-described hydraulic conductivity and
hydraulic gradient values and estimated values for effective porosity of 0.25 for the main
upper and lower alluvial sand and gravel aquifers and 0.20 for the upland aquifer, the
average groundwater seepage velocity in OU2 was calculated to range from 1.5 ft/day in
the Government Gulch upland aquifer to 2 ft/day in the main valley alluvial aquifers.
With a few exceptions, vertical hydraulic gradients are generally downward in the
eastern portion of OU2 and upward in the western portion of OU2 downgradient of the
Government Gulch vicinity. Vertical gradients do not appear to be seasonally variable.
2.2.3 Surface Water Hydrology
The main surface water body within OU2 is the SFCDR, which is depicted along with
its tributaries on Figure 2.1. The draft CSM report states that the interaction of
groundwater and surface water is a significant factor affecting contaminant fate and
transport within OU2, and the potential exposure of human and ecological receptors to
contaminants of concern (COCs) (CH2M Hill, 2005).
The approximate locations of gaining and losing reaches of the SFCDR within OU2
are shown on Figure 3-41 of the draft CSM report (Appendix A). The gaining and losing
conditions were observed under base flow conditions, in which flow in the SFCDR is
composed primarily of groundwater discharge. The interaction between surface water
and groundwater under different hydrologic conditions is not well-defined.
2.3 NATURE AND EXTENT OF CONTAMINATION
The primary COCs at OU2 are arsenic, cadmium, lead, and zinc, given their elevated
concentrations in OU2 groundwater, surface water, soil, and sediment; their potential to
have significant negative impacts on potential receptors; or both. Within OU2, arsenic is
present in surface water at concentrations toxic to aquatic organisms and other wildlife.
Cadmium is widely distributed within OU2, and is relatively mobile in aquatic
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environments. Lead is present within OU2 at concentrations toxic to waterfowl and other
wildlife via ingestion of contaminated soil or sediment. Ambient water quality criteria
(AWQC) for zinc are exceeded throughout OU2, generally at levels toxic to aquatic
organisms. Zinc is one of the most mobile of the heavy metals and is readily transported
in most natural waters. Of these four COCs, cadmium and zinc are, by far, the metals
that have the most widespread distribution and highest magnitude of exceedances of
cleanup goals in OU2 groundwater.
The primary source for dissolved metals in groundwater within OU2 is metal-rich
sediment within the vadose zone. The two release and transport mechanisms for metals
from this source are unsaturated flow downward through the vadose zone and the
seasonal rise and fall of the water table. The magnitude of dissolved metal release by
these mechanisms is related to the magnitude of the hydrologic event. Major hydrologic
events, such as occurred in 1996 to 1997, can result in a relatively large influx of metals
into the groundwater system due to enhanced flushing of metals out of the vadose zone.
The upper portion of the SFCDR valley essentially constitutes one large source area,
preventing delineation of discrete contaminant plumes in OU2 groundwater. Rather,
elevated metal concentrations are found in groundwater and surface water throughout
OU2. Given the near-surface locations of contaminant sources (e.g., mine tailings),
elevated metal concentrations are more prevalent in the surficial aquifers than at deeper
depths. Specifically, the upper alluvial sand and gravel aquifer beneath the SFCDR
valley and the upland aquifer present in Government Gulch (and perhaps other tributary
valleys north and south of the SFCDR valley) tend to have relatively high metal
concentrations. In contrast, elevated metal concentrations are less prevalent in the lower
alluvial sand and gravel aquifer beneath the lacustrine silt/clay aquitard. This indicates
that the silt/clay aquitard has minimized downward migration of metals to the lower
alluvial aquifer, despite the presence of a downward vertical hydraulic gradient
throughout a sizable portion of OU2.
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SECTION 3
LONG-TERM MONITORING PROGRAM AT OU2
The existing groundwater and surface water monitoring program at OU2 was
examined to to assess its overall effectiveness at achieving the OU2-specific monitoring
objectives, and to (1) identify potential opportunities to streamline monitoring activities
while still maintaining an effective monitoring program, and (2) identify data gaps that
may required the addition of additional monitoring points. The monitoring program at
OU2 is reviewed in the following subsections.
3.1 DESCRIPTION OF MONITORING PROGRAM
The OU2 monitoring program examined during this long-term monitoring
optimization (LTMO) evaluation consists of 77 groundwater monitoring wells and 18
surface water monitoring stations. The wells and surface water stations included in this
analysis are listed in Tables 3.1 and 3.2, respectively. The groundwater wells are shown
on Figure 3.1 classified by hydrostratigraphic unit (HU), and the 18 surface-water
monitoring stations are shown on Figure 3.2. These wells and stations were included in
the LTMO analysis based on their "Active" status in the draft Environmental Monitoring
Plan (BMP) (CH2M Hill, 2005b) and discussions with Bunker Hill site personnel. This
evaluation did not include new wells proposed in the EMP or surface water monitoring
stations associated with treatment plant outfalls. Monitoring point information listed in
Tables 3.1 and 3.2 includes "basecase" sampling frequency (generally quarterly), first
used and most recent sampling events, HU for groundwater wells, and location for
surface water stations.
The objectives of the groundwater monitoring program at OU2 are outlined in the
draft OU2 EMP (CH2M Hill, 2005b) and listed below:
1. Evaluate groundwater within OU2 for compliance with federal maximum
contaminant levels (MCLs);
2. Evaluate the nature of groundwater/surface water interaction and the impact of
groundwater discharge on surface water quality;
3. Evaluate the cumulative effects of Phase I remedial actions;
4. Provide data for five-year reviews of remedy implementation as required by
CERCLA; and
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TABLE 3.1
BASECASE GROUNDWATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
Hydrogeologic
Unit
Current Sampling
Frequency
Earliest Sampling
Data Used
Most Recent
Data Used
Deadwood Gulch Upland Aquifer
BH-DW-GW-0001
Government Gulch U
BH-GG-GW-0001
BH-GG-GW-0002
BH-GG-GW-0003
BH-GG-GW-0004
BH-GG-GW-0005
BH-GG-GW-0006
BH-GG-GW-0007
BH-GG-GW-0008
Upland
Quarterly
3/16/2000
4/7/2004
pland Aquifer
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
4/17/2000
4/17/2000
4/17/2000
4/17/2000
2/24/2000
2/24/2000
4/4/2003
4/4/2003
10/19/2004
10/19/2004
10/19/2004
10/19/2004
10/19/2004
10/19/2004
10/14/2004
10/18/2004
Upland Aquifer between Deadwood and Railroad Gulches
BH-ILF-GW-0001
Upland
Quarterly
4/25/2001
1/15/2003
Upland Aquifer at the Smelter Closure Area
BH-SCA-GW-0001
BH-SCA-GW-0002
BH-SCA-GW-0005
BH-SCA-GW-0006
BH-SCA-GW-0007
SCA
SCA
SCA
SCA
SCA
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
2/23/2000
2/23/2000
2/23/2000
2/23/2000
2/23/2000
10/13/2004
10/12/2004
10/18/2004
10/18/2004
10/12/2004
Transect 1
BH-SF-E-0001
BH-SF-E-0002
BH-SF-E-0003
Single
Single
Single
Quarterly
Quarterly
Quarterly
3/31/2003
4/1/2003
4/1/2003
10/11/2004
10/11/2004
10/11/2004
Transect 1 to Transect 2
BH-SF-E-0101
BH-SF-E-0201
Transect 2
BH-SF-E-0301-U
BH-SF-E-0302-L
BH-SF-E-0305-U
BH-SF-E-0306-L
BH-SF-E-0309-U
BH-SF-E-0310-L
BH-SF-E-0311-U
Single
Single
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
4/15/2000
4/21/2000
4/15/2000
4/15/2000
4/2/2003
4/2/2003
4/1/2003
4/1/2003
4/2/2003
10/11/2004
10/11/2004
10/12/2004
10/12/2004
7/14/2004
10/11/2004
10/12/2004
4/7/2004
10/12/2004
Transect 2 to Transect 3
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0318-U
BH-SF-E-0320-U
BH-SF-E-0321-U
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
10/20/2000
10/20/2000
10/23/2000
4/15/2000
10/24/2000
4/15/2000
4/15/2000
10/26/2004
10/26/2004
10/13/2004
10/26/2004
10/13/2004
7/19/2004
10/26/2004
FINAL Bunker Hill Tables.xls
3-2
-------
TABLE 3.1 (Continued)
BASECASE GROUNDWATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-SF-E-0322-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0409-U
BH-SF-E-0410-U
Hydrogeologic
Unit
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Current Sampling
Frequency
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Earliest Sampling
Data Used
5/1/2003
4/15/2000
4/15/2000
5/1/2003
10/24/2000
10/24/2000
2/23/2000
Most Recent
Data Used
10/13/2004
10/26/2004
10/26/2004
10/13/2004
10/13/2004
10/13/2004
10/12/2004
Transect 3
BH-SF-E-0423-U
BH-SF-E-0424-L
BH-SF-E-0425-U
BH-SF-E-0426-L
BH-SF-E-0427-U
BH-SF-E-0428-L
Upper
Lower
Upper
Lower
Upper
Lower
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
4/15/2000
4/7/2003
4/7/2003
4/7/2003
2/23/2000
4/7/2003
10/26/2004
10/26/2004
10/12/2004
10/12/2004
10/12/2004
10/12/2004
Transect 3 to Transect 5
BH-SF-E-0429-U
BH-SF-E-0501-U
BH-SF-E-0502-U
BH-SF-E-0503-U
BH-SF-E-0504-U
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
2/24/2000
2/23/2000
4/19/2000
1/18/2001
1/18/2001
10/26/2004
10/18/2004
10/20/2004
10/26/2004
10/26/2004
Transect 5
BH-SF-W-0001-U
BH-SF-W-0002-L
BH-SF-W-0003-U
BH-SF-W-0004-L
BH-SF-W-0005-U
BH-SF-W-0006-L
BH-SF-W-0007-U
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
4/8/2003
4/8/2003
4/9/2003
4/9/2003
4/18/2000
4/9/2003
4/18/2000
10/19/2004
10/19/2004
10/18/2004
10/18/2004
10/25/2004
10/25/2004
10/25/2004
Transect 5 to Transect 6
BH-SF-W-0008-U
BH-SF-W-0009-U
BH-SF-W-0010-U
BH-SF-W-0011-L
BH-SF-W-0019-U
BH-SF-W-0018-U
BH-SF-W-0020-U
BH-SF-W-0104-U
BH-SF-W-0111-U
BH-SF-W-0118-U
BH-SF-W-0119-U
BH-SF-W-0121-U
BH-SF-W-0122-L
Upper
Upper
Upper
Lower
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Lower
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
4/19/2000
4/19/2000
4/18/2000
4/18/2000
4/18/2000
4/19/2000
4/18/2000
4/19/2000
4/20/2000
2/22/2002
2/22/2002
4/20/2000
4/20/2000
7/27/2004
10/20/2004
10/25/2004
10/25/2004
10/26/2004
10/20/2004
10/26/2004
10/20/2004
10/20/2004
10/20/2004
10/25/2004
10/20/2004
10/20/2004
FINAL Bunker Hill Tables.xls
3-3
-------
TABLE 3.1 (Continued)
BASECASE GROUNDWATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
Hydrogeologic
Unit
Current Sampling
Frequency
Earliest Sampling
Data Used
Most Recent
Data Used
Transect 6
BH-SF-W-0201-U
BH-SF-W-0202-L
Upper
Lower
Quarterly
Quarterly
4/8/2003
4/3/2003
10/20/2004
10/20/2004
Transect 6 to Transect 7
BH-SF-W-0203-U
Upper
Quarterly
4/21/2000
10/25/2004
Transect 7
BH-SF-W-0204-U
BH-SF-W-0205-L
Upper
Lower
Quarterly
Quarterly
4/8/2003
4/8/2003
10/25/2004
10/25/2004
FINAL Bunker Hill Tables.xls
3-4
-------
TABLE 3.2
BASECASE SURFACE WATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Surface Water
Station Name
BH-BC-0001
BH-CS-0001
BH-DW-0001
BH-GC-0001
BH-GG-0001
BH-HC-0001
BH-IG-0001
BH-JC-0001
BH-MC-0001
BH-MC-0002
BH-MG-0001
BH-PG-0001
BH-RR-0001
BH-WP-0001
PC-339
SF-268
SF-270
SF-271
Location
Bunker Creek
Seeps North of CIA
Magnet Gulch
Grouse Creek
Gov't Creek at Gulch Mouth
Humboldt Creek
Italian Gulch
Jackass Creek
Old Milo Creek Outfall
New Milo Creek Outfall
Deadwood Gulch
Portal Gulch
Railroad Gulch
West Page Swamp Outfall
Pine Creek below Amy Gulch
SFCDR at Elizabeth Park
SFCDR at Smelterville
SFCDR at Pinehurst
Current Sampling
Frequency
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Annual3'
Annual3
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Earliest Sampling
Data Used
2/17/00
3/17/00
4/25/00
11/14/01
4/25/00
3/22/03
3/22/03
3/22/03
5/1/02
2/17/00
4/25/00
4/24/00
3/22/03
4/24/00
4/24/00
4/25/00
4/21/04
4/24/00
Most Recent
Data Used
10/29/04
10/28/04
10/29/04
10/28/04
10/28/04
10/28/04
4/10/03
4/22/04
10/29/04
10/29/04
10/29/04
2/20/02
3/22/03
10/28/04
4/20/04
4/22/04
4/21/04
4/20/04
Station sampled during high-flow events.
FINAL Bunker Hill Tables.xls
5-5
-------
South Fork Coeur
d'Alene River
-W-0204
F-W-0205
^iSF-E-0423-U
-E-0424-L
SF-E-0403-U
-E-0402-U_SF-E-0321-U
•SF-E-0317-
QSF-W-0203-b'
\ I/
SF-W-0201 -
inenust Narrows
SF-W-0008-UU „,-,„,„
•SF-W-0104-U
Smelterville Flats SF-W-0002-L
,wm,,-u SF*om-u* sBagaJ-BtaBJi
-W-0202-L
F-W-01
F-W-0118-U
st Page Swim
-W-0119-U
E 0409 U SF-E-0309-U
t utua u SF.E.031 O-L
SF-W-0005-
SF-W-0006-L
SF-W-0007
CA-GW-0006
CA-GW-0007
•F-E-0001
F-E-0002
:-E-0003
*Note that the "BH-" at the beginning of all the wells
has been omitted from the labels on this figure.
0 1,2502,500
5,000
7,500
10,000
1 inch equals 2,500 feet
Legen
Groundwater Monitoring Well
Hydraulic Unit
• Lower
O SCA
A Single Unconfined
4 Upland
• Upper
Monitoring Well Transect
! Main Valley Alluvial Aquifer
Upland Tributary Alluvial Aquifers
Lower Aquifer Confining Unit
(Eastern Extent)
FIGURE 3.1
GROUNDWATER
MONITORING WELLS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3-6
-------
South Fork Coeur
d'Alene River
f -BlH-DW-00011
trjj?
/
Legend
Surface Water
Monitoring Station
Monitoring Well Transect
! Main Valley Alluvial Aquifer
0 1,2502,500
5,000
7,500
10,000
1 inch equals 2,500 feet
Upland Tributary Alluvial Aquifers
Lower Aquifer Confining Unit
(Eastern Extent)
FIGURE 3.2
SURFACE WATER
MONITORING POINTS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3-7
-------
5. Improve understanding of processes and variability within OU2 to assist in
Phase I remedial action evaluations and Phase II remedial design and
implementation.
The objectives of the surface water monitoring program are also outlined in the draft
OU2 BMP (CH2M Hill, 2005b) and listed below:
1. Evaluate tributaries to the SFCDR within OU2 with respect to compliance with
the AWQC;
2. Evaluate potential impacts to SFCDR water quality from tributaries and
groundwater within OU2; and
3. Evaluate the cumulative effects of Phase I remedial actions with respect to
water quality goals and objectives.
Four of the surface water monitoring stations listed in Table 3.2 (PC-339, SF-268, SF-
270, and SF-271) are sampled as part of the environmental monitoring plan for OU3
(Coeur d'Alene Basin). However, results generated from sampling of these stations are
also used during the analysis and evaluation of OU2 monitoring results. Consequently,
OU2 surface water data needs were considered when the OU3 monitoring plan was
developed.
3.2 SUMMARY OF ANALYTICAL DATA
The monitoring program for OU2 groundwater and surface water stations were
evaluated using results for sampling events performed from February 2000 through
October 2004 to represent the time period after Phase I remedial actions were
implemented. The Phase I remedial actions resulted in substantial changes to site
conditions that were expected to impact groundwater and surface water quality.
Therefore, use of data collected prior to Phase I remediation could potentially have
resulted in misleading trends that are not representative of recent site conditions. The
database was processed to remove duplicate data by retaining the "normal" result for
each duplicate sample pair (i.e., excluding the duplicate value). As discussed in Section
2.3, the COCs identified for OU2 include zinc, cadmium, arsenic, and lead (both total and
dissolved for surface water stations). Tables 3.3 and 3.4 present summaries of the
occurrence of potential COCs based on the data collected from OU2 monitoring points
for groundwater and surface water, respectively. Tables 3.3 and 3.4 show that although
arsenic and lead have high percentages of detections, cadmium and zinc are more
significant COCs at the site based on their widespread and relatively high concentrations
compared to their respective MCLs or AWQCs.
Figures 3.3 through 3.6 display the most recent (typically October 2004, but the most
recent event for wells BH-DW-GW-0001 and BH-SF-E-0310-L [April 2004]; BH-ILF-
GW-0001 [Jan 2003]; and BH-SF-E-0305-U, BH-SF-E-0320-U, and BH-SF-W-0008-U
[July 2004] occurred prior to October 2004) concentrations of arsenic, cadmium, lead,
and zinc respectively for the groundwater monitoring wells classified by MCL
exceedance ratio. Table 3.5 presents the corresponding most recent COC concentrations
for each monitoring well and associated sampling date. The most recent samples from 51
3-8
-------
TABLE 3.3
SUMMARY OF OCCURRENCE OF GROUNDWATER CONTAMINANTS OF CONCERN
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Parameter
Dissolved Arsenic
Dissolved Cadmium
Dissolved Lead
Dissolved Zinc
Total
Samples"'
1330
1330
1330
1327
Range of Detects
(mg/L)b/
0.00004
0.00001
0
0.002
-
-
-
-
0.119
2.13
0.54
60.5
Number of
Detects
389
1003
372
1268
Percentage
of Detects
29.2%
75.4%
28.0%
95.6%
Percentage of
Samples with
MCL
Exceedances
17.1%
66.2%
9.5%
50.6%
MCL
(mg/L)
0.01*
0.005
0.015
5e/
Number of
Wells with
Results
77
77
77
77
Number of
Wells with
Detections
74
77
72
77
Number of
Wells with
MCL
Exceedances
40
60
15
44
Analytical data analyzed includes sampling results from February 2000 through October 2004.
mg/L = milligrams per liter.
0 Data includes 77 sampling points shown on Table 3.1
Arsenic MCL based on new EPA standard that became effective on February 22, 2002. (Compliance January 23, 2006)
FINAL Bunker Hill Tables.xls
3-9
-------
TABLE 3.4
SUMMARY OF OCCURRENCE OF SURFACE WATER CONTAMINANTS OF CONCERN
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Parameter
Arsenic
Dissolved Arsenic
Cadmium
Dissolved Cadmium
Lead
Dissolved Lead
Zinc
Dissolved Zinc
Total
Samples3'
230
245
230
252
230
245
230
252
Range of
Detects (mg/L)b/
8E-05
0.0001
5E-05
5E-05
0.0003
6E-05
0.0024
0.0041
-
-
-
-
-
-
-
-
0.1
0.11
1.04
0.26
3.18
0.79
34.8
34.5
Number
of
Detects
134
132
177
192
185
151
228
250
Percentage
of Detects
58.3%
53.9%
77.0%
76.2%
80.4%
61.6%
99.1%
99.2%
Percentage of
Samples with
AWQC
Exceedances
58.3%
53.9%
72.2%
68.7%
69.6%
44.9%
90.9%
87.3%
AWQCC/
(mg/L)
0.000018
0.000018
0.001
0.001
0.0025
0.0025
0.105
0.105
Number of
Stations with
Results0'
17
18
17
18
17
18
17
18
Number of
Stations with
Detections
15
16
16
17
17
18
17
18
Number of
Stations with
AWQC
Exceedances
15
16
13
14
14
15
15
16
a Analytical data analyzed includes sampling results from February 2000 through October 2004.
b/ mg/L = milligrams per liter.
0 AWQCs are hardness dependant. AWQCs shown assume a hardness of 100 mg/L
0 Data includes 18 sampling points shown on Table 3.2
FINAL Bunker Hill Tables.xls
3-10
-------
Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-L
SF-E-0425-UI
SF-E-0429-U
SF-i
SF-W-0018-l
•F-W-0201-U
CMT , „, ™ ^ „ ,, r-i SF-W-0008-U H
RF-W-0104-U-H SE3W-0003-I
SF-W-0121-LT ^
SF-W-0119-U0/
SF-W-0118-L
SF-E-0503-l
• I SF-E-0504-l
*» .SF-E-0502-l
I LCI **f*e^S A
^^SF-W-0001-U.
_,._.-uJS
SF-W-0009-I
SF-'
SF-W-0010-U
SF-W-0020-U
SF-W-0019-U
iSF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
•F-E-0407-U
F-E-0321-U
F-E-0322-U
^ SF-E-0317-l
07SB.E-Q318-U
•SF-E-0409-U
GSF-E-041(f=bi
:A-G'
I
nSF-E-0311-U
SF-E-0315 -
J--SF-E-0314-U
•-E-0316
•F-E-0305-U
F-E*-0301-I
F-E-0320-U
;A-GW-0006\ \LF-GW-0001
«
14-'
)3G
'-E-02I
•F-E-0309-U
I-U
f-GW-0001
Lower Unit Wells
BSF-W-0205-L
SF-W-0004-LH
W-0011-LM GSF-W-0006-L
Note: Majority of wells "most recent" sampling event occured in October 2004; wells BH-DW-GW-0001, BH-SF-E-0310-L
[April 2004], BH-SF-E-0305-U, BH-SF-E-0320-U, BH-SF-W-0008-U [July 2004], and BH-ILF-GW-0001 [Jan 2003],
most recent sampling event occurred previously.
Specific concentrations
and sampling dates
shown in Table 3.5
Legend
Arsenic Concentrations (MCL = 0.01 mg/L)
D Non-Detect
A
-------
Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-L
SF-E-0425-UI
SF-E-0429-U
•SF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
F-E-0407-U
F-E-0321-U
SF-E-0503-I
• I SF-E-0504-I
*» .SF-E-0502-I
U-F1
u-tJ SF.W.0001.|L
SF-E-0409-U
Lower Unit Wells
BSF-W-0205-L
SF-W-0004-lO
QSF-W-0006-L
Note: Majority of wells "most recent" sampling event occured in October 2004; wells BH-DW-GW-0001, BH-SF-E-0310-L
[April 2004], BH-SF-E-0305-U, BH-SF-E-0320-U, BH-SF-W-0008-U [July 2004], and BH-ILF-GW-0001 [Jan 2003],
most recent sampling event occurred previously.
Legend
Cadmium Concentration (MCL=0.005mg/L)
D Non-Detect
Specific concentrations
and sampling dates
1-10 times MCL
A
O
O
100 times MCL
0 1,2502,500 5,000 7,500
10,000
• Feet
FIGURE 3.4
MOST RECENT DISSOLVED
CADMIUM CONCENTRATIONS
IN GROUNDWATER
LONG TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3-12
-------
Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-U
SF-E-0425-U
SF-E-0429-U
•SF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
F-E-0407-U
F-E-0321-U
F-E-0322-U
SF-E-0503-
SF-E-0504-
,.SF-E-0502-
SF-W-0203-U^ /SF-W-0201-U
fj ^SF-W-0104-U[H
SF-W-0121-U "
SF-W-0119-U-H
-
-SF-E-0314-U
GG-GW
SCA-G
SCA-GW-0001
Lower Unit Wells
BSF-W-0205-L
SF-W-0004-LH
W-0011-L^ QSF-W-0006-L
Note: Majority of wells "most recent" sampling event occured in October 2004; wells BH-DW-GW-0001, BH-SF-E-0310-L
[April 2004], BH-SF-E-0305-U, BH-SF-E-0320-U, BH-SF-W-0008-U [July 2004], and BH-ILF-GW-0001 [Jan 2003],
most recent sampling event occurred previously.
Legend
Lead Concentration (MCL=0.015mg/L)
D Non-Detect
A
-------
Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-L
SF-E-0425-UI
SF-E-0429-U
SF-E-0503-L
•SF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
F-E-0407-U
F-E-0321-U
F-E-0322-U
SF-E-0317-
SF-E-0318-U
1 n ^ ASF-E-0311-
F-W-0201-U'
SF-W-0104-UO
SF-E-040S-U ^•>T^SFr\|v0333114_u
SF-W-0005-U A.
SF-W-0010-U^ A
SF-W-0020-U [~KGG-GW-0005
SF-W-0019-U
\ w > \JA.W ^
\ \ \ X^SF-E-0305-U
\ \ \ VF-E-OSOI-U
\ \ ^SF-E-0320-U
\ \
GG-GW-0003-fc),
SCA-G'
SCA-GW-0001
X3G-GW-0002
0GG-GW-0002
/GG-GW-0001
AGG-GW-OOOI
Lower Unit Wells
BSF-W-0205-L
Note: Majority of wells "most recent" sampling event occured in October 2004; wells BH-DW-GW-0001, BH-SF-E-0310-L
[April 2004], BH-SF-E-0305-U, BH-SF-E-0320-U, BH-SF-W-0008-U [July 2004], and BH-ILF-GW-0001 [Jan 2003],
most recent sampling event occurred previously.
Leqend
Specific concentrations
anc' sampiin9 dates
shown in Table 3.5
Zinc Concentrations (MCL=5mg/L)
D Non-Detect
A 10 times MCL
0 1,25C2,500 5,000 7,500
10,000
• Feet
FIGURE 3.6
MOST RECENT DISSOLVED
ZINC CONCENTRATIONS
IN GROUNDWATER
LONG TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3-14
-------
TABLE 3.5
MOST RECENT GROUNDWATER COC CONCENTRATIONS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-DW-GW-0001
BH-GG-GW-0001
BH-GG-GW-0002
BH-GG-GW-0003
BH-GG-GW-0004
BH-GG-GW-0005
BH-GG-GW-0006
BH-GG-GW-0007
BH-GG-GW-0008
BH-ILF-GW-0001
BH-SCA-GW-0001
BH-SCA-GW-0002
BH-SCA-GW-0005
BH-SCA-GW-0006
BH-SCA-GW-0007
BH-SF-E-0001
BH-SF-E-0002
BH-SF-E-0003
BH-SF-E-0101
BH-SF-E-0201
BH-SF-E-0301-U
BH-SF-E-0302-L
BH-SF-E-0305-U
BH-SF-E-0306-L
BH-SF-E-0309-U
BH-SF-E-0310-L
BH-SF-E-0311-U
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0318-U
BH-SF-E-0320-U
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0409-U
BH-SF-E-0410-U
BH-SF-E-0423-U
Most Recent
Sampling Event
4/7/04
10/19/04
10/19/04
10/19/04
10/19/04
10/19/04
10/19/04
10/14/04
10/18/04
1/15/03
10/13/04
10/12/04
10/18/04
10/18/04
10/12/04
10/11/04
10/11/04
10/11/04
10/11/04
10/11/04
10/12/04
10/12/04
7/14/04
10/11/04
10/12/04
4/7/04
10/12/04
10/26/04
10/26/04
10/13/04
10/26/04
10/13/04
7/19/04
10/26/04
10/13/04
10/26/04
10/26/04
10/13/04
10/13/04
10/13/04
10/12/04
10/26/04
Dissolved
Arsenic
MCL=10|^g/L
NDa/
ND
ND
ND
12.6
ND
ND
ND
ND
ND
ND
ND
ND
3.8
ND
ND
ND
ND
ND
ND
ND
ND
ND
2.6
ND
ND
ND
4.7
ND
ND
ND
ND
ND
ND
ND
39.3
59
19.5
ND
44.4
ND
57.7
Dissolved
Cadmium
MCL=5|^g/L
13.5b/
ND
108
122
359
113
ND
350
ND
249
ND
455
837
1420
ND
ND
ND
ND
18.4
36.7
101
37
21.8
40.6
11.7
ND
ND
6.7
ND
ND
20.6
9.9
30
24.8
17.5
30.9
ND
321
6.2
23
217
ND
Dissolved
Lead
MCL=15|^g/L
0.19
ND
ND
11
ND
63.1
ND
18.7
ND
1
ND
ND
ND
6.6
ND
ND
ND
ND
4.6
ND
30.6
ND
ND
ND
18
ND
ND
ND
ND
ND
ND
ND
17.2
ND
114
ND
ND
22.4
7.8
ND
ND
ND
Dissolved Zinc
MCL=5000|^g/L
844
233
2,120
5,000
21,700
6,250
182
7,210
333
12,300
ND
2,740
824
14,900
209
190
ND
155
3,520
6,430
21,700
10,400
4,640
8,560
1,640
291
77
972
70
947
7,070
1,560
8,970
7,120
5,860
25,900
12,200
11,100
11,200
20,800
18,700
17,100
FINAL Bunker Hill Tables.xls
5-15
-------
TABLE 3.5 (Continued)
MOST RECENT GROUNDWATER COC CONCENTRATIONS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-DW-GW-0001
BH-GG-GW-0001
BH-GG-GW-0002
BH-GG-GW-0003
BH-GG-GW-0004
BH-GG-GW-0005
BH-GG-GW-0006
BH-GG-GW-0007
BH-GG-GW-0008
BH-ILF-GW-0001
BH-SCA-GW-0001
BH-SCA-GW-0002
BH-SCA-GW-0005
BH-SCA-GW-0006
BH-SCA-GW-0007
BH-SF-E-0001
BH-SF-E-0002
BH-SF-E-0003
BH-SF-E-0101
BH-SF-E-0201
BH-SF-E-0301-U
BH-SF-E-0302-L
BH-SF-E-0305-U
BH-SF-E-0306-L
BH-SF-E-0309-U
BH-SF-E-0310-L
BH-SF-E-0311-U
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0318-U
BH-SF-E-0320-U
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0409-U
BH-SF-E-0410-U
BH-SF-E-0423-U
Most Recent
Sampling Event
4/7/04
10/19/04
10/19/04
10/19/04
10/19/04
10/19/04
10/19/04
10/14/04
10/18/04
1/15/03
10/13/04
10/12/04
10/18/04
10/18/04
10/12/04
10/11/04
10/11/04
10/11/04
10/11/04
10/11/04
10/12/04
10/12/04
7/14/04
10/11/04
10/12/04
4/7/04
10/12/04
10/26/04
10/26/04
10/13/04
10/26/04
10/13/04
7/19/04
10/26/04
10/13/04
10/26/04
10/26/04
10/13/04
10/13/04
10/13/04
10/12/04
10/26/04
Dissolved
Arsenic
MCL=10|^g/L
NDa/
ND
ND
ND
12.6
ND
ND
ND
ND
ND
ND
ND
ND
3.8
ND
ND
ND
ND
ND
ND
ND
ND
ND
2.6
ND
ND
ND
4.7
ND
ND
ND
ND
ND
ND
ND
39.3
59
19.5
ND
44.4
ND
57.7
Dissolved
Cadmium
MCL=5|^g/L
13.5b/
ND
108
122
359
113
ND
350
ND
249
ND
455
837
1420
ND
ND
ND
ND
18.4
36.7
101
37
21.8
40.6
11.7
ND
ND
6.7
ND
ND
20.6
9.9
30
24.8
17.5
30.9
ND
321
6.2
23
217
ND
Dissolved
Lead
MCL=15|^g/L
0.19
ND
ND
11
ND
63.1
ND
18.7
ND
1
ND
ND
ND
6.6
ND
ND
ND
ND
4.6
ND
30.6
ND
ND
ND
18
ND
ND
ND
ND
ND
ND
ND
17.2
ND
114
ND
ND
22.4
7.8
ND
ND
ND
Dissolved Zinc
MCL=5000|^g/L
844
233
2,120
5,000
21,700
6,250
182
7,210
333
12,300
ND
2,740
824
14,900
209
190
ND
155
3,520
6,430
21,700
10,400
4,640
8,560
1,640
291
77
972
70
947
7,070
1,560
8,970
7,120
5,860
25,900
12,200
11,100
11,200
20,800
18,700
17,100
FINAL Bunker Hill Tables.xls
5-16
-------
of the 77 monitoring wells (66%) had at least one COC that exceeded MCLs. Likewise,
Table 3.6 presents the most recent (typically October 2004, but the most recent event for
surface water stations BH-IG-0001 [April 2003]; BH-JC-0001, PC-339, SF-268, SF-270,
and SF-271 [April 2004]; BH-PG-0001 [Feb 2002]; and BH-RR-0001 [Mar 2003]
occurred prior to October 2004) COC concentrations for each surface water monitoring
station for both total and dissolved COCs. Figures 3.7 through 3.10 display the most
recent total and dissolved concentrations of arsenic, cadmium, lead and zinc,
respectively. The most recent samples from 15 of the 18 surface water monitoring
stations (83%) had at least one COC that exceeded an AWQC.
3-17
-------
TABLE 3.6
MOST RECENT SURFACE WATER COC CONCENTRATIONS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Surface Water
Station Name
BH-BC-0001
BH-CS-0001
BH-DW-0001
BH-GC-0001
BH-GG-0001
BH-HC-0001
BH-IG-0001
BH-JC-0001
BH-MC-0001
BH-MC-0002
BH-MG-0001
BH-PG-0001
BH-RR-0001
BH-WP-0001
PC-339
SF-268
SF-270
SF-271
Location
Bunker Creek
Seeps North of CIA
Magnet Gulch
Grouse Creek
Gov't Creek at Gulch Mouth
Humboldt Creek
Italian Gulch
Jackass Creek
Old Milo Creek Outfall
New Milo Creek Outfall
Deadwood Gulch
Portal Gulch
Railroad Gulch
West Page Swamp Outfall
Pine Creek below Amy Gulch
SFCDR at Elizabeth Park
SFCDR at Smelterville
SFCDR at Pinehurst
Most Recent
Sampling
Event
10/29/04
10/28/04
10/29/04
10/28/04
10/28/04
10/28/04
4/10/03
4/22/04
10/29/04
10/29/04
10/29/04
2/20/02
3/22/03
10/28/04
4/20/04
4/22/04
4/21/04
4/20/04
Arsenic
Dissolved
Arsenic
AWQC=0.018|^g/L
2.8a/
40.5
0.39
0.99
0.36
0.44
NDb/
ND
0.53
0.54
13.5
ND
NSC/
0.63
ND
0.35
0.43
0.36
2.9
41
0.36
0.48
0.61
0.43
0.18
ND
0.58
0.4
13.2
ND
0.11
0.8
ND
0.28
0.34
0.25
Cadmium
AWQC=
lUg/L
32.1
10.3
4.4
1
189
4.3
0.18
ND
0.5
4.4
84
ND
NS
ND
0.32
3.6
4.6
3.6
Dissolved
Cadmium
32.3
10.5
4.5
0.91
191
4.7
0.14
ND
0.37
4.4
85.5
ND
76.9
ND
0.2
3.1
4
3.1
Lead
Dissolved
Lead
AWQC= 2.5|^g/L
2.8
0.64
8.1
5.3
22.4
5.3
0.6
0.47
3
250
5.3
16
NS
4.6
0.45
7.4
12
9
1.4
0.06
4.8
0.11
8.8
1.7
0.26
0.15
1.3
219
4.9
10
4.4
1.3
0.21
2.9
4.8
o
J
Zinc
AWQC=
105ug/L
1690
11900
570
199
6480
1040
36.4
o o
J.J
125
1230
2560
292
NS
53.6
63.3
485
675
560
Dissolved
Zinc
1730
12400
585
157
6510
1100
18
5.9
122
1250
2610
288
2820
47.9
47.7
429
609
492
B results in [ig/L
b/ ND = analyte not detected
c/ NS = not sampled
AWQC exceedances highlighted in yellow
Most recent sampling dates earlier than 10/04 highlighted in grey.
FINAL Bunker Hill Tables.xls
3-18
-------
South Fork Coeur
d'Alene River
SF-271
Wo.36
DisAs:0.2
H-IG-0001
As: Not Detected
BH-MC-0002
As: 0.54
Dis As: ff.4*
PC-339
As: Not Detected
Us As: Not Detected
Pinenust Narrows
SF-273*
As: 0.43
Dis As: 0.34
BH-CS-0001
s: 40.
Dis As: 41
Smelterville Flats
-JC-0001
Not Detected
Dis As: Not Detected
BH-MG-0001
13.5
1
BH-GG-00
As: 0.36
Dis As: 0.6
East Page
Swamp
BH-PG-0001
As: Not Detected
BH-GC-0001
As: 0.99
Dis As: 0.48
BH-DW-0001
Dis As: 0.36 a
BH-MC-0001
As: 0.53
Dis As: 0.58
SF-268
As: /35
\sAs: 0.28
Note: Majority of wells "most recent" sampling event occurred in October 2004,
but surface water stations BH-IG-0001 [April 2003], BH-JC-0001, PC-339,
SF-268, SF-270, SF-271 [April 2004], BH-PG-0001 [Feb2002], and BH-RR-0001 [Mar 2003;
most recent sampling events occurred previously.
Surface Water
Monitoring Station
Monitoring Well Transect
! Main Valley Alluvial Aquifer
0 1,2502,500
5,000
7,500
10,000
1 inch equals 2,500 feet
Upland Tributary Alluvial Aquifers
Lower Aquifer Confining Unit
(Eastern Extent)
FIGURE 3.7
MOST RECENT TOTAL
AND DISSOLVED ARSENIC
IN SURFACE WATER
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3-19
-------
South Fork Coeur
d'Alene River
BH-CS-0001
0Cd: 10.:
SF-273*
Cd: 4.6
DisCd:4
DisCd:10.5
-JC-0001
Cd: Not Detected
DisCd: Not Detected
BH-DW-0001
d: 4.4
d:4.5
I8H-MG-0001
84 0
DisCd :
Detected
DisCd: Not Detected
H-IG-0001
Cd: 0^8
:
-------
South Fork Coeur
d'Alene River
Pb: 0.45
Dis Pb: 0.21
Pinehust Narrows
-WP-0001
SF-273*
Pb: 12
Dis Pb: 4.8
BH-CS-0001
0Pb: 0.64
Dis Pb: 0.06
Smelterville Flats
BH-DW-0001
Pb: 8.1
isPb:4.8
BH-GG-00
Pb: 22.4
Dis Pb: 8.8
BH-GC-0001
East Page
Swamp
£BH-MG-
5.3
Dis Pb:
H-IG-0001
Pb: 0.6
Pb: 16
— i
CO
;/
BH-RR-0001
Pb: Not Sampled
Note: Majority of wells "most recent" sampling event occurred in October 2004,
but surface water stations BH-IG-0001 [April 2003], BH-JC-0001, PC-339,
SF-268, SF-270, SF-271 [April 2004], BH-PG-0001 [Feb2002], and BH-RR-0001 [Mar 2003]
most recent sampling events occurred previously.
Surface Water
Monitoring Station
Monitoring Well Transect
! Main Valley Alluvial Aquifer
0 1,2502,500
5,000
7,500
10,000
1 inch equals 2,500 feet
Upland Tributary Alluvial Aquifers
Lower Aquifer Confining Unit
(Eastern Extent)
FIGURE 3.9
MOST RECENT TOTAL
AND DISSOLVED LEAD
IN SURFACE WATER
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3-21
-------
South Fork Coeur
d'Alene River
isZn:492DisZn:47.7
BH-CS-0001
11900
DisZn: 12400
-JC-0001
3.3
DisZn: 5.9
n:47.9
st Page Swam
EH-GG-000
i: 6480
sZn:6510
0001
SrcB%DW-OQ01
iZn: 570
BH-GC
£Zn: 199
4H-RR-0001
BH-PG-0001
Zn: 292
DisZn: 288
/Zn: Not Sampled
DisZn: 2820
BH-MC-000
Zn: 1
Dis
Note: Majority of wells "most recent" sampling event occurred in October 2004,
but surface water stations BH-IG-0001 [April 2003], BH-JC-0001, PC-339,
SF-268, SF-270, SF-271 [April 2004], BH-PG-0001 [Feb2002], and BH-RR-0001 [Mar 2003]
most recent sampling events occurred previously.
Surface Water
Monitoring Station
Monitoring Well Transect
! Main Valley Alluvial Aquifer
0 1,2502,500
5,000
7,500
10,000
1 inch equals 2,500 feet
Upland Tributary Alluvial Aquifers
Lower Aquifer Confining Unit
(Eastern Extent)
FIGURE 3.10
MOST RECENT TOTAL
AND DISSOLVED ZINC
IN SURFACE WATER
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3-22
-------
SECTION 4
QUALITATIVE LTMO EVALUATION
An effective groundwater monitoring program will provide information regarding
contaminant plume migration and changes in chemical concentrations through time at
appropriate locations, enabling decision-makers to verify that contaminants are not
endangering potential receptors, and that remediation is occurring at rates sufficient to
achieve remedial action objectives (RAOs) within a reasonable time. The design of the
monitoring program should therefore include consideration of existing receptor exposure
pathways as well as exposure pathways arising from potential future use of the
groundwater.
Performance monitoring wells located within and downgradient from a contaminated
area provide a means of evaluating the effectiveness of a groundwater remedy relative to
performance criteria. Long-term monitoring (LTM) of these wells also provides
information about migration of the contamination and temporal trends in chemical
concentrations. Groundwater monitoring wells located downgradient from the leading
edge of a contaminated area (i.e., sentry wells) are used to evaluate possible changes in
the extent of the plume and, if warranted, to trigger a contingency response action if
contaminants are detected.
Primary factors to consider when developing a groundwater monitoring program
include at a minimum:
• Aquifer heterogeneity,
• Types of contaminants,
• Distance to potential receptor exposure points,
• Groundwater seepage velocity and flow direction(s),
• Potential surface-water impacts, and
• The effects of the remediation system.
These factors will influence the locations and spacing of monitoring points and the
sampling frequency. Typically, the greater the seepage velocity and the shorter the
distance to receptor exposure points, the more frequently groundwater sampling should
be conducted.
4-1
-------
One of the most important purposes of LTM is to confirm that the contaminant plume
is behaving as predicted. Graphical and statistical tests can be used to evaluate plume
stability. If a groundwater remediation system or strategy is effective, then over the long
term, groundwater-monitoring data should demonstrate a clear and meaningful
decreasing trend in concentrations at appropriate monitoring points. The groundwater
and surface water monitoring programs at OU2 were evaluated to identify potential
opportunities for streamlining monitoring activities while still maintaining an effective
performance and compliance monitoring program.
4.1 METHOD FOR QUALITATIVE EVALUATION OF MONITORING
NETWORK
The LTMO evaluation included 77 groundwater wells and 18 surface water sampling
stations located in OU2. These sampling points, their associated HUs (for groundwater
wells), their basecase monitoring frequencies, and the earliest and most recent sampling
data used in the LTMO analysis are listed in Tables 3.1 and 3.2; their locations are
depicted on Figures 3.1 and 3.2.
Multiple factors were considered in developing recommendations for continuation or
cessation of groundwater monitoring at each well. In some cases, a recommendation was
made to continue monitoring a particular well, but at a reduced frequency. A
recommendation to discontinue monitoring at a particular well based on the information
reviewed does not necessarily constitute a recommendation to physically abandon the
well. A change in site conditions might warrant resumption of monitoring at some time
in the future at wells that are not currently recommended for continued sampling.
Typical factors considered in developing recommendations to retain a well in, or remove
a well from, an LTM program are summarized in Table 4.1. Typical factors considered
in developing recommendations for monitoring frequency are summarized in Table 4.2.
TABLE 4.1
MONITORING NETWORK OPTIMIZATION DECISION LOGIC
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Reasons lor Retaining a Well in
Monitoring Network
Well is needed to further characterize the site or
monitor changes in contaminant concentrations
through time
Well is important for defining the lateral or vertical
extent of contaminants.
Well is needed to monitor water quality at
compliance point or receptor exposure point (e.g.,
water supply well)
Well is important for defining background water
quality
Reasons lor Removing a Well Irom
Monitoring Network
Well provides spatially redundant information with
a neighboring well (e.g. , same constituents, and/or
short distance between wells)
Well has been dry for more than two years37
Contaminant concentrations are consistently below
laboratory detection limits or cleanup goals
Well is completed in same water-bearing zone as
nearby well(s)
a/ Periodic water-level monitoring should be performed in dry wells to confirm that the upper boundary of the saturated
zone remains below the well screen. If the well becomes re-wetted, then its inclusion in the monitoring program
should be evaluated.
4-2
-------
TABLE 4.2
MONITORING FREQUENCY DECISION LOGIC
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Reasons for Increasing
Sampling Frequency
Groundwater velocity is high
Change in contaminant concentration would
significantly alter a decision or course of action
Well is necessary to monitor source area or
operating remedial system
Cannot predict if concentrations will change
significantly over time, or recent significant
increasing trend in contaminant concentrations is
resulting in concentrations approaching or
exceeding a cleanup goal, possibly indicating plume
expansion
Reasons for Decreasing
Sampling Frequency
Groundwater velocity is low
Change in contaminant concentration would not
significantly alter a decision or course of action
Well is distal from source area and remedial system
Concentrations are not expected to change
significantly over time, or contaminant levels have
been below groundwater cleanup objectives for
some prescribed period of time
4.2 RESULTS OF QUALITATIVE LTMO EVALUATION FOR
GROUNDWATER
The results of the qualitative evaluation of monitoring wells in OU2 are described in
this subsection. The evaluation included the 77 groundwater monitoring wells listed in
Table 3.1. The qualitative LTMO evaluation for groundwater considered historical
analytical results for the four primary COCs (arsenic, cadmium, lead, and zinc) and
whether continued monitoring of each well was desirable in light of the OU2
groundwater monitoring goals listed in Section 3.1.
Table 4.3 includes recommendations for retaining or removing each well, the
recommended sampling frequency, and the rationale for the recommendations. The draft
CSM report (CH2M Hill, 2005a) discusses contaminant fate and transport by monitoring
well transect or inter-transect area, beginning at the upgradient (east) end of the site and
progressing in the downgradient (westerly) direction. Similarly, the wells in Table 4.3
are listed in general order from upgradient to downgradient according to the transect or
inter-transect area in which they are located. The qualitative analysis results are depicted
on Figure 4.1 and are summarized by aquifer in the following subsections.
4.2.1 Single Unconfined Aquifer
Wells located along Transect 1 and between Transects 1 and 2 are screened in the
single unconfined aquifer, which is located in the easternmost portion of OU2
hydraulically upgradient of the eastern limit of the lacustrine silt/clay aquitard. As shown
in Table 4.3, two of the three wells located at Transect 1 are recommended for retention
in the LTM program because they provide background groundwater quality data in the
upper and lower portions of the aquifer. Collection of background data is useful because
it helps define the impact of contaminant sources and temporal variations in the
frequency and magnitude of precipitation events within OU2 on groundwater quality. In
addition, the qualitative evaluation judged wells located on defined transects to be
4-3
-------
TABLE 4.3
QUALITATIVE EVALUATION OF GROUNDWATER MONITORING NETWORK
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
Hydrologic Unit
Current
Sampling
Frequency
Qualitative Analysis
Exclude
Retain
Monitoring Frequency
Recommendation
Rationale
Deadwood Gulch Upland Aquifer
BH-DW-GW-0001
Upland
Quarterly
Government Gulch Upland Aquifer
BH-GG-GW-0001
BH-GG-GW-0002
BH-GG-GW-0003
BH-GG-GW-0004
BH-GG-GW-0005
BH-GG-GW-0006
BH-GG-GW-0007
BH-GG-GW-0008
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Upland Aquifer between Deadwood and Railroad Gulches
BH-ILF-GW-0001
Upland
Quarterly
Upland Aquifer at the Smelter Closure Area
BH-SCA-GW-0001
BH-SCA-GW-0002
BH-SCA-GW-0005
BH-SCA-GW-0006
BH-SCA-GW-0007
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 1
BH-SF-E-0001
BH-SF-E-0002
BH-SF-E-0003
Single Unconfined
Single Unconfined
Single Unconfined
Quarterly
Quarterly
Quarterly
Transect 1 to Transect 2
BH-SF-E-0101
BH-SF-E-0201
Transect 2
BH-SF-E-0301-U
BH-SF-E-0302-L
BH-SF-E-0305-U
BH-SF-E-0306-L
BH-SF-E-0309-U
BH-SF-E-0310-L
BH-SF-E-0311-U
Single Unconfined
Single Unconfined
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
X
X
annual
Monitors effectiveness of Phase I removal actions in Deadwood Gulch and quality of GW emerging from the gulch; decreasing Cd concentrations justify
lower frequency; other COCs are < MCL and exhibit stable concentrations
X
X
X
X
X
X
X
X
biennial
annual
annual
annual
annual
annual
annual
annual
Monitors background GW quality in Gov't Gulch; reduced frequency justified by non-detect or very low magnitude COC concentrations over 1 5 events from
4/00 to 10/04; more frequent delineation of background GW quality unnecessary unless upgradient conditions change.
Monitors elevated metal concentrations in upland aquifer and Phase I remedial effectiveness at achieving MCLs; decreasing Cd and Zn trends (approaching
or below MCLs) justify lower frequency; see text in Section 4.2.4 for additional details regarding recommended monitoring frequency
Monitors elevated metal concentrations in upland aquifer and Phase I remedial effectiveness at achieving MCLs; decreasing Cd and Zn trends (approaching
or below MCLs) justify lower frequency; see text in Section 4.2.4 for additional details regarding recommended monitoring frequency
Monitors elevated metal concentrations in upland aquifer and Phase I remedial effectiveness at achieving MCLs; decreasing Cd and Zn trends (approaching
or below MCLs) and low magnitude of As levels (near new MCL) justify lower frequency; see text in Section 4.2.4 for additional details regarding
recommended monitoring frequency
Monitors net effect of Phase I remedial measures on alluvial GW quality in Gov't Gulch; decreasing COC concentrations justifies lower frequency; see text in
Section 4.2.4 for additional details regarding recommended monitoring frequency
Single, v. slight MCL exceedance (Cd) in Apr 02; perform low-frequency monitoring to assess potential increasing trend for Cd over time; low magnitude of
metal concentrations does not justify more frequent sampling; see text in Section 4.2.4 for additional details regarding recommended monitoring frequency
Monitors net effect of Phase I remedial measures on alluvial GW quality in Gov't Gulch; lack of temporal trends justifies lower frequency; see text in Section
4.2.4 for additional details regarding recommended monitoring frequency
No MCL exceedances; perform low-frequency monitoring to assess potential increasing Zn trend over time; low magnitude of metal concentrations does not
justify more frequent sampling; see text in Section 4.2.4 for additional details regarding recommended monitoring frequency
X
semiannual
Well appears to be monitoring effectiveness of Phase I removal and capping actions at two upslope industrial landfills; insufficient data to determine temporal
trends for all COCs; perform semiannual sampling to support trend determinations, then reassess frequency. Consider annual frequency if COCs are
decreasing
X
X
X
X
X
biennial
semiannual
semiannual
semiannual
semiannual
Background well for the SCA; more frequent definition of upgradient GW quality not necessary due to concentration stability and lack of increasing trends
At upgradient edge of SCA; increasing metal concentrations justifies higher frequency to support remedial decision-making
Monitors for seepage from SCA waste cell; retain at higher frequency to support remedial decision-making and more rapid response in the event of waste cell
seepage
Monitors for seepage from SCA waste cell; retain at higher frequency to support remedial decision-making and more rapid response in the event of waste cell
seepage
Monitors for seepage from SCA waste cell; retain at higher frequency to support remedial decision-making and more rapid response in the event of waste cell
seepage
X
X
annual
annual
exclude
On Trans ect 1 ; provides background data in lower portion of alluvial aquifer; upgradient location and lack of MCL exceedances over 1 st 2 yr of quarterly
sampling justifies relatively low frequency
On Trans ect 1 ; provides background data in lower portion of alluvial aquifer; upgradient location and lack of MCL exceedances over 1 st 2 yr of quarterly
sampling justify relatively low frequency
Redundant with and typically similar to lower concentrations than BH-SF-E-0001, which exhibits similar trends
X
X
X
X
X
X
X
X
X
semiannual
semiannual
semiannual
annual
semiannual
annual
semiannual
annual
annual
Monitors elevated Cd concentrations in alluvial aquifer in area with low well density; upgradient of Milo Creek channel restoration so indicates impact of
restoration on GW quality further downgradient; potentially indicative of surface water impacts on GW quality
Monitors elevated Cd and Zn concentrations in alluvial aquifer in area with low well density; indicative of Phase 1 remediation effectiveness (channel
restoration at Milo Ck).
Monitors elevated metal concentrations at Transect 2 near preferential flowpath (pre-1900 river channel) and near area of contaminated fill south of Bunker
Ck
same as BH-SF-E-0301-U; lower aquifer completion interval and lack of increasing trends justify lower frequency
Monitors elevated metal concentrations in upper alluvial aquifer at Transect 2
Monitors elevated metal concentrations at Transect 2; lower aquifer completion interval and lack of increasing trends justify lower frequency
Monitors elevated metal concentrations in upper alluvial aquifer at Transect 2
Monitors lower aquifer at Transect 2; lower aquifer completion interval, lack of MCL exceedances, and lack of increasing trends justify removal from LTM
program; however, retain at lower frequency to support annual mass flux calculations
Retain to evaluate contaminant flux across Transect 2 and relationship between the SFCDR and the upper aquifer north of the river (in terms of water quality
and head difference). Relatively low sampling frequency justified by lack of MCL exceedances during 8 events over 1.5 years. Well appears to be screened
in lower-K unit that is not fully representative of the upper aquifer; consider further frequency reduction to biennial at a later date.
FINAL Bunker Hill Tables.xls
4-4
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TABLE 4.3 (continued)
QUALITATIVE EVALUATION OF GROUNDWATER MONITORING NETWORK
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
Hydrologic Unit
Current
Sampling
Frequency
Transect 2 to Transect 3
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0318-U
BH-SF-E-0320-U
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0409-U
BH-SF-E-0410-U
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 3
BH-SF-E-0423-U
BH-SF-E-0424-L
BH-SF-E-0425-U
BH-SF-E-0426-L
BH-SF-E-0427-U
BH-SF-E-0428-L
Upper
Lower
Upper
Lower
Upper
Lower
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 3 to Transect 5
BH-SF-E-0429-U
BH-SF-E-0501-U
BH-SF-E-0502-U
BH-SF-E-0503-U
BH-SF-E-0504-U
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 5
BH-SF-W-0001-U
BH-SF-W-0002-L
BH-SF-W-0003-U
BH-SF-W-0004-L
BH-SF-W-0005-U
BH-SF-W-0006-L
BH-SF-W-0007-U
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 5 to Transect 6
BH-SF-W-0008-U
BH-SF-W-0009-U
BH-SF-W-0010-U
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Qualitative Analysis
Exclude
X
X
X
X
Retain
Monitoring Frequency
Recommendation
Rationale
X
X
X
X
X
X
X
X
X
X
X
semiannual
exclude
semiannual
semiannual
semiannual
semiannual
semiannual
annual
semiannual
exclude
semiannual
exclude
semiannual
semiannual
Monitors elevated Cd concentrations in upper aquifer at upgradient perimeter of CIA; retain at relatively high frequency to evaluate effectiveness of Phase I
remedial actions and facilitate remedial decision-making
Redundant with and consistently lower Cd and Zn concentrations than BH-SF-E-0314-U
Monitors elevated Cd concentrations in upper aquifer within/beneath CIA; retain at relatively high frequency to detect potential migration of metals from CIA
and facilitate timely response and remedial decision-making
Monitors elevated metal concentrations in upper aquifer at perimeter of CIA; retain at relatively high frequency to detect potential migration of metals from
CIA and facilitate timely response and remedial decision-making
Monitors elevated Cd concentrations in upper aquifer within/beneath CIA; retain at relatively high frequency to detect potential migration of metals from CIA
and facilitate timely response and remedial decision-making
Monitors elevated metal concentrations in upper aquifer at perimeter of CIA and downgradient of holding ponds; retain at relatively high frequency to detect
potential migration of metals from CIA and holding ponds and facilitate timely response and remedial decision-making
Monitors elevated metal concentrations in upper aquifer at perimeter of CIA; retain at relatively high frequency to detect potential migration of metals from
CIA and facilitate timely response and remedial decision-making
Well is screened in impounded waste material; retain to provide indication of waste toxicity over time, but at reduced frequency because well does not serve a
sentry purpose.
Monitors elevated metal concentrations in upper aquifer at perimeter of CIA; retain at relatively high frequency to detect potential migration of metals from
CIA and facilitate timely response and remedial decision-making
Redundant with and consistently has similar or lower Cd and Zn concentrations than BH-SF-E-0402-U
Monitors elevated metal concentrations in upper aquifer within/beneath CIA; retain at relatively high frequency to facilitate evaluation of effectiveness of
Phase I remedial actions and support remedial decision-making
Redundant with and consistently has lower Cd and Zn concentrations than BH-SF-E-0407-U
Monitors elevated metal concentrations in upper aquifer within/beneath CIA; retain at relatively high frequency to facilitate evaluation of effectiveness of
Phase I remedial actions and support remedial decision-making
Monitors elevated metal concentrations in upper aquifer at perimeter of CIA; retain at relatively high frequency to detect potential migration of metals from
CIA and facilitate timely response and remedial decision-making
X
X
X
X
X
X
semiannual
annual
semiannual
annual
semiannual
annual
Monitors elevated metal concentrations in upper aquifer downgradient of CIA at Transect 3; increasing As trend; retain to support mass flux calculation
Monitors lower aquifer downgradient of CIA at Transect 3 ; lower aquifer completion interval, lack of increasing trends, and lack of MCL exceedances justify
lower frequency; consider reducing to biennial frequency if 5 years of below-MCL results are obtained.
Monitors elevated metal concentrations in upper aquifer downgradient of CIA at Transect 3 ; retain to support mass flux calculation
Monitors elevated metal concentrations in lower aquifer downgradient of CIA at Transect 3; lower aquifer completion interval, lack of increasing trends, and
low contaminant load relative to paired shallow well justify lower frequency
Monitors elevated metal concentrations in upper aquifer downgradient of CIA at Transect 3; near preferential flowpath (pre-1900 river channel); retain to
support mass flux calculation
Monitors elevated metal concentrations in lower aquifer downgradient of CIA at Transect 3; lower aquifer completion interval, lack of increasing trends, and
low contaminant load relative to paired shallow well justify lower frequency
X
X
X
X
semiannual
semiannual
semiannual
semiannual
exclude
Monitors elevated metal concentrations in upper aquifer downgradient of CIA and Slag Pile Area
Monitors elevated metal concentrations and increasing As concentrations in upper aquifer downgradient of SCA
Monitors elevated metal concentrations in upper aquifer in area of low well density north of SFCDR
Monitors elevated metal concentrations in upper aquifer downgradient of Slag Pile Area
Redundant with and tends to have similar or lower Cd and Zn concentrations than BH-SF-E-0503-U
X
X
X
X
X
X
X
semiannual
annual
semiannual
annual
semiannual
annual
annual
Monitors elevated metal concentrations in upper aquifer at Transect 5 near preferential flowpath (pre-1900 river channel)
Retain to facilitate mass flux calculations; lower aquifer completion interval, lack of MCL exceedances, and lack of increasing trends justify lower frequency;
consider reducing to biennial frequency if 5 years of below-MCL results are obtained.
Monitors elevated metal concentrations in upper aquifer at Transect 5
Monitors elevated metal concentrations in lower aquifer at Transect 6; lower aquifer completion interval and lack of increasing trends justify lower frequency
Monitors elevated metal concentrations in upper aquifer at Transect 5
Slight exceedances of future As MCL (0.01 mg/L); lower aquifer completion interval, relatively lowmetal concentrations, and lack of increasing trends
justify lower frequency; consider reducing to biennial if 5 years of results indicate continued low-magnitude, stable results
Only 1 slight MCL exceedance in 1 8 events; additional delineation of GW quality at edge of alluvial valley unnecessary, but retain at low frequency to
facilitate mass flux calculations at Transect 5 ; consider reducing to biennial frequency if 5th year of data indicate continued low, stable trends .
X
X
X
semiannual
semiannual
semiannual
Monitors elevated metal concentrations in upper aquifer in Smelterville Flats area (Phase I removal and capping)
Monitors elevated metal concentrations in upper aquifer in Smelterville Flats area (Phase I removal and capping)
Monitors elevated metal concentrations in upper aquifer in Smelterville area
FINAL Bunker Hill Tables.xls
4-5
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TABLE 4.3 (continued)
QUALITATIVE EVALUATION OF GROUNDWATER MONITORING NETWORK
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-SF-W-0011-L
BH-SF-W-0019-U
BH-SF-W-0018-U
BH-SF-W-0020-U
BH-SF-W-0104-U
BH-SF-W-0111-U
BH-SF-W-0118-U
BH-SF-W-0119-U
BH-SF-W-0121-U
BH-SF-W-0122-L
Hydrologic Unit
Lower
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Lower
Current
Sampling
Frequency
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 6
BH-SF-W-0201-U
BH-SF-W-0202-L
Upper
Lower
Quarterly
Quarterly
Transect 6 to Transect 7
BH-SF-W-0203-U
Upper
Quarterly
Transect 7
BH-SF-W-0204-U
BH-SF-W-0205-L
Upper
Lower
Quarterly
Quarterly
Qualitative Analysis
Exclude
X
X
X
Retain
X
X
X
X
X
X
X
Monitoring Frequency
Recommendation
annual
exclude
exclude
exclude
semiannual
semiannual
semiannual
semiannual
annual
annual
Rationale
Monitors elevated metal concentrations in lower aquifer in Smelterville area
One slight MCL exceedance (Cd in Apr 02) in 20 events; further delineation of this relatively uncontaminated area is unncessary.
No MCL exceedances since Oct 01 (13 events); further delineation of this relatively uncontaminated area is unnecessary
No MCL exceedances over 17 events from April 00 to Oct 04; further delineation of this uncontaminated area is unnecessary
Monitors elevated metal concentrations in upper aquifer in Smelterville Flats area; near preferential flowpath (pre-1900 river channel) and in Phase I
removal/capping area
Monitors elevated metal concentrations (including potentially increasing As levels) near Page WWTP and downgradient of holding ponds
Monitors potentially increasing As concentrations in Upper Aquifer adjacent to West Page Swamp and downgradient from Page WWTP and Smelterville
Flats
Monitors elevated metal concentrations (including potentially increasing As levels) near West Page Swamp
Downgradient of increasing As levels in upper aquifer; relatively low metal concentrations justifies reduced sampling frequency
Retain to monitor lower aquifer GW quality in area with very low density of lower aquifer wells; downgradient of increasing As levels in upper aquifer;
relatively low metals concentrations and lower aquifer completion interval justifies lower sampling frequency
X
X
semiannual
annual
Monitors elevated metal concentrations at Transect 6 near current and pre-1900 river channels (potential preferential flow paths)
Monitors lower aquifer GW quality near downgradient edge of "Box"; lower aquifer completion interval and historic lack of MCL exceedances justify lower
sampling frequency
X
annual
Monitors upper aquifer GW quality downgradient of Pine Creek (losing reach) in area of low well density; single slight MCL exceedance (CD, Apr 02) in 16
events justifies reduced frequency
X
X
annual
annual
Downgradient sentry well permits evaluation of upper aquifer GW quality leaving "Box"; history of relatively low metal concentrations (no MCL exceedances
and COCs mostly non-detect) justify reduced frequency; delete from LTM program if 5 yr of low, stable results are obtained
Downgradient sentry well permits evaluation of lower aquifer GW quality leaving "Box"; relatively low metal concentrations and lower aquifer completion
interval justify reduced sampling frequency; delete from LTM program if 5 years of low, stable results are obtained
FINAL Bunker Hill Tables.xls
4-6
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Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-U
SF-E-0425-U
SF-E-0429-U
SF-W-0018-l
F-W-0201-U
SF-W-0008-U
SF-E-0503-I
I SF-E-0504-I
'- , SF-E-0502-I
SF-W-0009-UA
S -- v SF-W-0005J
SF-W-0010-UA
SF-w-oo20-Jri
SF-W-0019-L^
•SF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
F-E-0407-U
F-E-0321-U
.SF-E-0317-
A SF-E-Q318-U
f A OSF-E
SF-E-0409:U
ASF-E-°41
-------
particularly useful because they can be used to periodically estimate the mass flux of
selected metals migrating across the vertical plane of the transect. Periodic (e.g., annual)
estimates of the mass flux of metals across the transects would be a useful way to
evaluate the net impact of the various factors influencing groundwater quality throughout
OU2 (i.e., the Phase I remedial actions; inputs to and outflows from the groundwater
system such as contributions from sources, gains from and losses to surface water, and
the influence of fate and transport properties such as metals precipitation and sorption).
For this reason, relatively detailed definition of contaminant and hydraulic characteristics
along the defined transects was considered to be relatively important during the
qualitative analysis. Although a substantial degree of uncertainly may be associated with
the magnitudes of calculated mass fluxes given the uncertainty in estimation of
representative hydraulic conductivity values, relative changes in mass flux could be
determined if the same hydraulic information and wells are used in the calculations from
year to year. These relative changes could be useful indicators of remedial effectiveness
and the effects of significant hydrologic (e.g., precipitation and snowmelt) events.
The background groundwater quality data collected to date indicate that groundwater
at Transect 1 is relatively uncontaminated compared to more downgradient locations.
Given the relatively low magnitude and stable nature of metal concentrations in
groundwater at Transect 1, indicated by the first two years of quarterly monitoring, a
relatively infrequent (i.e., annual) monitoring frequency is recommended for the two
Transect 1 wells recommended for retention. Annual sampling should be performed at a
time of year when metal concentrations in groundwater are typically relatively elevated
based on historical data. The third Transect 1 well, BH-SF-E-0003, is recommended for
deletion from the LTM program because it is nearly co-located (both horizontally and
vertically) with BH-SF-E-0001 and exhibits similar trends, with generally similar or
lower metal concentrations than that well. BH-SF-E-0003 and BH-SF-E-0001 are
screened from 41 to 61 feet bgs and 46 to 59 feet bgs, respectively, and thus are
monitoring similar portions of the single unconfined aquifer.
The two wells screened in the single unconfined aquifer between Transects 1 and 2 are
recommended for continued sampling primarily because they monitor elevated metal
concentrations in an area that does not contain any other wells screened in the single
unconfined aquifer. Therefore, they appear to be spatially important. In addition, they
can be used to indicate the impact of Phase I remedial actions performed in the eastern
portion of OU2 on groundwater quality (e.g., channel restoration in the Milo Creek
drainage). Data from these wells (especially BH-SF-E-0101, which is screened near the
water table) also can be used to assess the impact of surface water infiltration to the
groundwater system, given that surface water flow measurements indicate that the
SFCDR is losing in this area.
A semiannual monitoring frequency is recommended for wells BH-SF-E-0101 and -
0201. Semiannual is the highest frequency recommended in this analysis. Continuation
of quarterly monitoring of OU2 wells is not considered appropriate or necessary for the
following reasons:
• The quarterly monitoring performed to date is sufficient to qualitatively indicate
seasonal changes in COC concentrations (however, the historical data are not
necessarily adequate to determine seasonality in a statistical sense in order to
4-8
-------
perform statistical corrections for seasonality using the Mann-Kendall test for
trend).
• Given the very large size of OU2 relative to the estimated advective groundwater
velocity, significant changes in groundwater quality resulting from the Phase I
remedial actions are not anticipated to be recognizable from one quarter to the
next; therefore, quarterly sampling is not necessary to achieve monitoring goals 1
and 3 listed above in Section 4.2, and semiannual sampling is judged to be
sufficient to achieve all of the monitoring goals.
• The quarterly monitoring performed to date supports the observation that rapid and
substantial changes in groundwater quality are generally not occurring from one
quarter to the next. Therefore, semiannual monitoring should be adequate to
identify longer-term trends in groundwater quality.
The primary objective of recommending a semiannual monitoring frequency is to
provide sufficient data on temporal trends in COC concentrations (especially recent
trends) to facilitate making decisions regarding the need for, and scope of, Phase II
remedial actions. Once these decisions are made, a further decrease in the groundwater
monitoring frequency for wells screened in the single unconfmed aquifer and upper
alluvial sand and gravel aquifer (Section 4.2.2) to annual is recommended. This is
justified given that 1) MCL exceedances are widespread throughout the unconfmed
aquifers, 2) monitoring data obtained to date indicate that rapid changes in contaminant
concentrations are generally not occurring, and 3) the localized nature of remedial actions
relative to the large size of OU2 suggest that achieving MCLs in groundwater will be a
long process that can be adequately tracked with annual groundwater sampling. In
summary, the semiannual monitoring period is recommended to be relatively short (e.g.,
two to three years) and transitional to a less frequent (i.e., annual) monitoring approach.
Annual sampling should be performed at a time of year when metal concentrations in
groundwater are typically relatively elevated based on historical data. As stated in
Section 4.6, a temporary increase in the frequency of groundwater monitoring in the
event of an unusually large hydrologic event should be considered to capture potential
effects of dissolved metals releases from the vadose zone.
4.2.2 Upper Alluvial Sand and Gravel Aquifer
Most of the wells completed in the upper alluvial sand and gravel aquifer that
underlies the SFCDR valley are recommended for retention in the LTM program because
this aquifer has been and continues to be substantially impacted by historic mining-
related activities, and detections of COCs at concentrations that are substantially greater
than MCLs are widespread. Given that this aquifer is the uppermost water-bearing zone
in the SFCDR valley and receives discharge from groundwater underlying the hill slopes
and tributary valleys bordering the main valley, groundwater quality in this aquifer is
expected to be the primary indicator of the effectiveness of prior (Phase I) and future
(Phase II) remedial actions as well as of the effects of precipitation events that result in
leaching of contaminants from the vadose zone. In addition, this aquifer is in hydraulic
communication with surface water drainages that traverse the Bunker Hill Box.
Therefore, monitoring of wells screened in this aquifer is consistent with each of the five
groundwater monitoring goals listed above in Section 4.2. Given that only 44 wells are
4-9
-------
scattered throughout the shallow alluvial aquifer in OU2, which has an average length
and width of approximately 29,000 feet and 3,000 feet, respectively, there are few
redundancies in terms of spatial location.
A semiannual monitoring frequency for most wells completed in this aquifer is
recommended for the same reasons stated for the single unconfmed aquifer in Section
4.2.1. However, as is also stated in Section 4.2.1, the semiannual monitoring period
should not last longer than needed to support Phase II remedial action decisions, and
should be considered to be a short-term (i.e.., two to three years) transitional period to a
less-frequent (annual) monitoring frequency that is maintained for a longer period of
time.
Exceptions to the above-described monitoring strategy for the upper alluvial sand and
gravel aquifer are discussed below and in Table 4.3.
Four wells screened in this aquifer are recommended for removal from the LTM
program because they are co-located with other wells that exhibit similar temporal trends
and that historically have had COC concentrations that are generally similar to or higher
than the well recommended for removal. Therefore, continued monitoring of the co-
located well should be sufficient to track temporal trends in COC concentrations in the
upper aquifer at these locations over time. The wells recommended for removal for these
reasons include
• BH-SF-E-0315-U at the northeastern edge of the Central Impoundment Area
(CIA) (co-located with BH-SF-E-0314-U),
. BH-SF-E-0403-U at the northern edge of the CIA (co-located with BH-SF-E-
0402-U),
. BH-SF-E-0408-U in the interior of the CIA footprint (co-located with BH-SF-E-
0407-U), and
. BH-SF-E-0504-U located between Transects 3 and 5 (co-located with BH-SF-E-
0503-U).
Three wells are recommended for removal from the LTM program because they
appear to be monitoring relatively uncontaminated portions of the upper alluvial sand and
gravel aquifer. Continued monitoring of zones that have repeatedly been shown to be
relatively unimpacted by historic mining activities does not provide any useful
information; it is reasonable to assume that if these areas have not been impacted to date,
they will remain unimpacted in the future unless hydraulic conditions undergo a
significant change (e.g., installation of a pump and treat system). The wells
recommended for removal for this reason are described below
. BH-SF-W-0019-U and BH-SF-W-0020-U are both located at the southern edge of
the SFCDR alluvial valley in Smelterville. The former well has had only one very
slight MCL exceedance (cadmium in April 2002) in 20 events spanning 4.5 years,
and the latter well has not had any MCL exceedances in 17 events spanning 4.5
years).
4-10
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. BH-SF-W-0018-U is located adjacent to the SFCDR at the north edge of
Smelterville Flats. This well has not had any MCL exceedances in 13 monitoring
events since October 2001, and the prior MCL exceedances (for cadmium) were
very slight (maximum exceedance of 0.003 micrograms per liter [|ig/L]). It is
possible that groundwater quality at this location is influenced by recharge from
relatively clean surface water in the SFCDR.
Well BH-SF-E-0311-U could also potentially be included in this category and removed
from the LTM program. However, it was recommended for retention at a relatively low
sampling frequency as described in Table 4.3.
Four upper aquifer wells are recommended to be sampled at a lower (annual to
biennial) frequency as described below:
• BH-SCA-GW-0001 provides useful background groundwater quality information
due to its location upgradient of the Smelter Closure Area (SCA). However, it has
exhibited relatively stable metal concentrations over a nearly five-year time frame,
and more frequent definition of background conditions is not necessary unless
there is reason to believe that conditions at or upgradient of this well will change
in the future.
• BH-SF-W-0121-U provides useful information because it is located downgradient
of an area exhibiting potentially increasing arsenic concentrations in groundwater
(well BH-SF-W-0018-U). Well BH-SF-W-0121-U has exhibited two slight
exceedances of the cadmium MCL and one slight exceedance of the lead MCL in
21 sampling events spanning 4.5 years. Annual monitoring of this relatively
uncontaminated zone is recommended; more frequent monitoring is not necessary
to achieve any of the monitoring goals listed in Section 3.1.
• Wells BH-SF-W-0203-U and -0204-U are located near the downgradient (western)
edge of the Bunker Hill Box. They are useful because they monitor upper aquifer
groundwater quality leaving the Box. An annual sampling frequency for these
wells is recommended, given their history of relatively low and stable metal
concentrations, indicating they are monitoring relatively clean groundwater.
Groundwater quality at these locations should improve over time due to the effects
of prior (Phase I) and future (Phase II) remedial actions (although variation in the
magnitude and frequency of precipitation events will likely result in some
temporal variation in metal concentrations in OU2 groundwater). Annual
sampling of BH-SF-W-0204-U will facilitate annual mass flux calculations for
Transect 7.
4.2.3 Lower Alluvial Sand and Gravel Aquifer
There are only 13 lower aquifer wells included in the group of 77 wells evaluated.
The relatively low number of lower aquifer wells is likely because this aquifer tends to be
much less contaminated than the overlying upper alluvial aquifer as a result of the
shallow nature of the contaminant sources and the presence of the lacustrine silt/clay
aquitard. All 13 lower aquifer wells are recommended for retention at an annual
sampling frequency. The lower sampling frequency (relative to the upper aquifer) is
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justified by the relatively uncontaminated nature of this aquifer and the fact that is it
somewhat hydraulically isolated from the upper aquifer by the aquitard. Annual
sampling should be performed at a time of year when metal concentrations in
groundwater are typically relatively elevated based on historical data. Reasons for
retaining these wells for continued monitoring include:
• 11 of the 13 lower aquifer wells are located along defined transects across the
alluvial valley, and periodic sampling of these wells will permit evaluation of
metal concentrations in lower aquifer groundwater migrating across the transect
lines, thereby supporting evaluation of the impact of Phase I/II remedial actions on
groundwater quality in the lower aquifer. Some of these 11 wells contain elevated
concentrations of one or more COCs.
• Lower aquifer well BH-SF-W-0122-L is not located on a defined transect, but is
located downgradient of a large area between Transects 5 and 6 that contains only
one lower aquifer well (BH-SF-W-0011-L). Therefore, groundwater quality in the
lower aquifer throughout this large area is not well characterized. This well is
centrally located in a relatively narrow portion of the alluvial aquifer, where
groundwater from the large, uncharacterized area further to the east funnels
through a fairly narrow "neck" near Transect 6. Therefore, continued sampling of
this well will provide useful information on lower aquifer groundwater quality
funneling out of a fairly large uncharacterized area near the downgradient end of
the Bunker Hill Box.
• Lower aquifer well BH-SF-W-0011-L is also not located on a defined transect, but
is useful because it monitors elevated metal concentrations in the Smelterville
area. This well is the only lower aquifer well in the large, relatively poorly
characterized (in terms of the lower aquifer) area mentioned above.
It may be reasonable to further reduce the sampling frequency of some of the lower
aquifer wells, or remove them from the sampling program entirely, in the future based on
temporal trend criteria described in Section 5. Specifically, these criteria include 1) wells
that are continually non-detect for COCs or that have COC concentrations that are less
than the MCLs, 2) wells that exhibit decreasing COC concentrations, and 3) wells that
exhibit stable concentrations. An example of a well which could be a candidate for
additional frequency reduction in the future is BH-SF-E-0310-L, located at Transect 2,
given its historic lack of MCL exceedances and stable COC concentrations.
4.2.4 Upland Aquifer
Ten monitoring wells screened in the upland aquifer were evaluated. Eight of the 10
wells are located in or at the mouth of Government Gulch, one well is located at the
mouth of Deadwood Gulch, and the remaining well is located near the southern boundary
of the SFCDR alluvial valley between Railroad and Deadwood Gulches. Based on the
qualitative evaluation, each of these 10 wells is recommended for continued monitoring
at varying frequencies as described in the following paragraphs.
Government Gulch was the subject of Phase I removal and capping and channel
restoration actions that appear to be having a positive effect on metal concentrations in
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groundwater in the upland aquifer. Elevated concentrations of COCs detected at wells
BH-GG-GW-0002, -0003, -0004, and -0005 appear to be decreasing over time and, in
some cases, no longer exceed the MCL. However, the degree to which the decreasing
trends are due to the Phase I remedial actions as opposed to other environmental variables
such as temporal variation in the frequency and magnitude of precipitation events that
result in leaching of contaminants from the vadose zone is not known. Despite the
continued presence of elevated COC concentrations at Government Gulch, a relatively
infrequent (annual to biennial, see Table 4.3) sampling frequency is recommended by the
qualitative analysis based on the assumption that additional (Phase II) remedial actions
are not required and will not be performed (i.e., more frequent monitoring of wells
associated with Government Gulch is not required in the near term to support Phase II
remedial decision-making). If this assumption is incorrect, then a semi-annual sampling
frequency is recommended for Government Gulch wells to support Phase II remedial
decisions, followed by a reduction to annual sampling. Annual to biennial sampling
should be performed at a time of year when metal concentrations in groundwater are
typically relatively elevated based on historical data.
Upland aquifer well BH-DW-GW-0001 is recommended for retention because it
monitors the effectiveness of Phase I removal actions performed further upstream in
Deadwood Gulch at reducing elevated metal concentrations in groundwater. Cadmium is
the only COC in groundwater at this location, and, similar to the Government Gulch
wells described above, concentrations of this metal are decreasing. Concentrations of
arsenic, lead, and zinc are below their respective MCLs and exhibit relatively stable
trends. For these reasons, a relatively low (annual) sampling frequency is recommended
for this well.
Upland aquifer well BH-ILF-GW-0001 is recommended for retention at a semiannual
frequency because it appears to be monitoring the effectiveness of Phase I removal and
capping actions at two upslope industrial landfills. This well was installed in 2000 but
has only been sampled twice (April 2001 and January 2003) because it has been dry or
(once) could not be accessed due to snow. On October 24, 2005 there was approximately
1.8 feet of water in the well. As a result, there are insufficient data for this well to
determine temporal trends for all COCs; collection of additional data will support
statistical trend determinations, which will in turn help determine the proper future
monitoring frequency for this well. If insufficient water is present to collect samples
using a dedicated low-flow pump, then sample collection using another feasible method
(e.g., non-dedicated peristaltic pump) is recommended.
4.3 RESULTS OF QUALITATIVE LTMO EVALUATION FOR SURFACE
WATER
The results of the qualitative evaluation of surface water monitoring stations in OU2
are described in this subsection. The evaluation included the 18 surface water monitoring
stations listed in Table 3.2 (the treatment plant outfalls and proposed new stations were
excluded). The qualitative LTMO evaluation for surface water considered historical
analytical results for the four primary COCs (arsenic, cadmium, lead, and zinc) and
whether continued monitoring of each location was desirable in light of the OU2 surface
water monitoring goals listed in Section 3.1. Table 4.4 includes recommendations for
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TABLE 4.4
QUALITATIVE EVALUATION OF SURFACE WATER MONITORING NETWORK
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Surface Water
Station Name
BH-BC-0001
BH-CS-0001
BH-DW-0001
BH-GC-0001
BH-GG-0001
BH-HC-0001
BH-IG-0001
BH-JC-0001
BH-MC-0001
BH-MC-0002
BH-MG-0001
BH-PG-0001
BH-RR-0001
BH-WP-0001
PC-339
SF-268
SF-270
SF-271
Location
Bunker Creek
Seeps North of CIA
Magnet Gulch
Grouse Creek
Gov't Creek at Gulch Mouth
Humboldt Creek
Italian Gulch
Jackass Creek
Old Milo Creek Outfall
New Milo Creek Outfall
Deadwood Gulch
Portal Gulch
Railroad Gulch
West Page Swamp Outfall
Pine Creek below Amy Gulch
SFCDR at Elizabeth Park
SFCDR at Smelterville
SFCDR at Pinehurst
Current
Sampling
Frequency
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Annual3
Annual3
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Qualitative Analysis
Exclude
Retain
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Monitoring Frequency
Recommendation
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Rationale
Monitors elevated metals load discharging to SFCDR from Bunker Creek
Indicative of metal concentrations in groundwater discharging to SFCDR adjacent to CIA. Monitoring of surface water quality in
SFCDR (OU3) upstream and downstream of CIA should be sufficient to measure increase in metal load due to groundwater discharge;
repeated measurement of localized seep(s) along this long stretch of river adjacent to CIA for the purpose of gauging the impact of
groundwater discharge on surface water quality does not seem especially useful; however, continued sampling would serve to indicate
how groundwater quality in this portion of the CIA is changing over time in response to Phase I remedial actions; retain at semiannual
frequency to support Phase II remedial decision-making, then reduce to annual
Monitors elevated metals load discharging to Bunker Creek from Magnet Gulch
Monitors elevated metals load discharging from Grouse Creek and flowing toward SFCDR
Monitors elevated metals load entering SFCDR valley from Gov't Creek and allows quantification of metals load entering groundwater
along losing stretch between gulch mouth and SFCDR
Monitors elevated metals load discharging from Humboldt Creek and flowing toward SFCDR
Monitors relatively low metals load discharging to SFCDR from Italian Gulch. Only dissolved arsenic exceeds the AWQC based on
results from 2 samples. Evaluate whether As concentrations are representative of background levels and reduce to annual frequency if
results are not indicative of contamination and stable trend is indicated.
Monitors relatively low metals load discharging to SFCDR from Jackass Creek. Only arsenic exceeds the AWQC based on results from
4 samples. Evaluate whether As concentrations are representative of background levels and reduce to annual frequency if results are not
indicative of contamination and stable trend is indicated.
Monitors water that is infiltrating into the old piping system (different water than new Milo Creek outfall); retain to facilitate surface
water mass balance calculations.
Monitors elevated metals load discharging to SFCDR from Milo Creek; consistently higher metal concentrations than co-located station
BH-MC-0001
Monitors elevated metals load discharging to Bunker Creek from Deadwood Gulch
Monitors elevated metals load discharging to Bunker Creek from Portal Gulch
Monitors elevated metals load discharging to Bunker Creek from Railroad Gulch
Monitors elevated metals load discharging to SFCDR and net contribution of metals from upstream sources (Grouse and Humboldt
Creeks, page WWTP, and East and West Page Swamps)
Monitors discharge of metals from Pine Creek to the SFCDR; relatively low metal concentrations; most recent results reviewed were all
less than AWQC
Measures upstream, background surface water quality
Facilitates definition of metals load in SFCDR and spatial changes in that load due to inputs and outflows
Most downstream station in Bunker Hill Box; monitors net outflow of COCs from OU2
3 Station sampled during high-flow events.
FINAL Bunker Hill Tables.xls
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retaining or removing each monitoring station, the recommended sampling frequency,
and the rationale for the recommendations.
The OU2 surface water monitoring program focuses on measuring influxes of COCs
to the SFCDR due to the fact that the portion of the SFCDR that passes through OU2 is
part of OU3. Therefore, monitoring of the SFCDR itself is primarily performed under the
OU3 monitoring program. Only three SFCDR monitoring stations are included in the
data set used for this LTMO evaluation (i.e., SFCDR at Elizabeth Park, Smelterville, and
Pinehurst). As described in Section 3.1, these three stations (and PC-339 [Pine Creek
below Amy Gulch]) are sampled as part of the OU3 monitoring program, but the data are
used for both OUs 2 and 3. Fourteen of the remaining 15 monitoring locations are
located in tributary drainages just upstream of their confluence with Bunker Creek or the
SFCDR. The remaining monitoring station was established to sample groundwater seeps
adjacent to the SFCDR just north of the CIA.
Surface water drainages provide a means for metals contamination sourced in OU2 to
be transported out of upland areas to the SFCDR and then off site to the west. Therefore,
these drainages provide a means by which human and/or ecological receptors both within
and downstream of OU2 may be impacted. As stated in the draft CSM report (CH2M
Hill, 2005a), 52 mines and mine-related sites have been identified within OU2, most of
which are scattered throughout the upland area south of the SFCDR valley. As a result,
tributaries to the SFCDR that drain these upland areas can be contaminated with elevated
concentrations of metals, an observation supported by the surface water monitoring
results reviewed for this qualitative evaluation. Therefore, monitoring of surface water
quality in these tributaries is an important component of 1) developing an adequate
understanding of the locations of significant contaminant source areas that impact surface
water quality, 2) monitoring the effects of Phase I remedial activities on surface water
quality, 3) monitoring the effects of temporal variations in the frequency and magnitude
of precipitation events on surface water quality, and 4) evaluating the need for Phase II
remedial actions. None of the surface water monitoring stations listed in Table 4.4 are
recommended for immediate removal from the monitoring program. However, future
removal of selected stations may be justifiable as described in the following paragraphs.
The surface water monitoring network depicted on Figure 3.2 of this report and Figure
4-1 of the draft EMP (CH2M Hill, 2005b) appears to be reasonably comprehensive in
that input from each of the primary tributaries that flow into the SFCDR is measured.
However, some inputs are more significant than others. For example, results of the high-
flow monitoring event performed in March 2003 (see Table 5-10 of the draft CSM report
[CH2M Hill, 2005a]) indicate that 93 percent of the total cadmium load was measured at
two locations (BH-GG-0001 and HB-BC-0001). Similarly, 92 percent of the total lead
load was measured at two locations (BH-MC-0002 and BH-BC-0001), and 91 percent of
the total zinc load was measured at three locations (BH-MC-0002, BH-GG-0001, and
BH-BC-0001). In contrast, high-flow results for Italian Gulch (station BH-IG-0001)
indicate that only 0.008 percent of the total cadmium load, 0.2 percent of the total lead
load, and 0.03 percent of the total zinc load were discharged by this drainage. Therefore,
it may be possible to either remove selected sampling locations such as BH-IG-0001
from the surface water monitoring program or reduce their sampling frequency without
introducing significant error into measurement of the total metals load entering the
SFCDR.
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Table 5-9 of the draft CSM report (CH2M Hill, 2005a) indicates that there were no
exceedances of the AWQC for zinc, cadmium, lead, or antimony measured at the mouths
of Italian Gulch and Jackass Creek (BH-IG-0001 and BH-JC-0001); however, there was
at least one order-of-magnitude exceedance of the AWQC for arsenic at each location.
These observations are based on the results of only one to three samples. These two
drainages are located north of the SFCDR in an area containing relatively few historic
mines. If an additional two years of monitoring indicates continued low metal
concentrations in these two creeks, and Phase II remedial actions are not planned, then
consideration should be given to removing these stations from the monitoring program or
reducing the sampling frequency to biennial (during high-flow conditions). The degree
to which the arsenic concentrations detected in these two creeks are representative of
background levels should also be assessed. Similar types of analyses should be
performed as additional data are obtained to rank the metals loads of the various
tributaries to facilitate assessment of the importance of continued monitoring on a
semiannual basis.
A semiannual monitoring frequency for surface water in OU2 is judged to be
appropriate at this time because these events can be approximately timed to coincide with
high- and low-flow conditions, providing data that should be reasonably representative of
the range of metal concentrations present in surface water and supporting Phase II
remedial decisions. Higher-frequency monitoring results obtained to date can be used to
assess the optimal timing of the semiannual events Reduction of the sampling frequency
for the seeps north of the CIA to annual after Phase II remedial decisions have been made
should be considered, similar to the upper aquifer wells discussed in Section 4.2.
Additional recommendations regarding sampling frequency are made as part of the
temporal statistical analysis (Section 5), and final recommendations are made in Section
7.
4.4 LABORATORY ANALYTICAL PROGRAM
Groundwater samples are analyzed for dissolved concentrations of a short-list of seven
metals using USEPA Contract Laboratory Program (CLP) method ILM05.2. It is
assumed that use of a CLP method is required at this site, given its regulatory status.
Surface water samples are analyzed for both total and dissolved concentrations of a
short-list of seven metals using the same CLP method referenced above for groundwater.
Two additional analytes (calcium and magnesium) are targeted for hardness calculations
using the same method. Total and dissolved metal concentrations are each measured
annually during the high-flow and low-flow sampling events, respectively. This is
reasonable because the suspended sediment load during high-flow conditions is expected
to be relatively large, and total concentrations would be indicative of the total metals load
being carried by the river/creek. In contrast, the suspended sediment load during low-
flow conditions is expected to be relatively small, given that flow is primarily
representative of groundwater discharge.
This analytical program appears to be reasonably optimized, and no changes are
recommended. It is assumed that pH, specific conductance, turbidity, and depth to water
are being measured during well purging; measurement of pH is recommended given its
effect on the mobility of selected metals. Measurement of dissolved oxygen and
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oxidation-reduction potential during purging is recommended for the same reason. These
are simple field measurements that can provide further insight into metals fate and
transport.
4.5 DATA GAPS
No data gaps in the OU2 surface water monitoring network were observed during the
qualitative evaluation. Measurement of inputs to the SFCDR via tributary surface water
drainages appears to be adequate for the intended purpose.
Specific data gaps in the groundwater monitoring network were assessed during
performance of the qualitative evaluation. Section 7.0 of the draft CSM report (CH2M
Hill, 2005a) summarizes general data gaps in a relatively "broad-brush" manner (e.g.,
general topics that would benefit from an improved understanding are identified), but
specific actions to fill these gaps (e.g., installation of five borings in these specific
locations) are not identified. The discussion in this subsection is limited to data gaps
associated with the groundwater monitoring network, rather than all site-characterization-
related data gaps. However, implementation of these recommendations would assist in
filling some of the more general characterization-related data gaps outlined in the draft
CSM report. A number of the recommendations focus on enhancing the groundwater
monitoring networks at existing transect locations to more accurately estimate the mass
flux of metals in groundwater across these transect lines, as described above in Section
4.2.1. Periodic mass flux estimates are a potentially useful way to semi-quantitatively
measure the effectiveness of Phase I remedial actions. Installation of 22 new monitoring
wells should be considered as described below and in Table 4.3.
1. The density of monitoring wells between Transects 1 and 2 is relatively low, and
groundwater quality within large areas is not monitored. Subsurface conditions in
this area could be better characterized by implementing one or both of the
following two approaches:
a. Installation of at least two additional monitoring well pairs in the single
unconfined aquifer north and south of BH-SF-E-0201 to help refine
groundwater hydraulic and contaminant characteristics and provide for more
timely and comprehensive monitoring of the effects of Phase I remedial
actions performed along Milo Creek. Installation of well pairs is
recommended due to the prevalence of downward vertical hydraulic gradients
in the eastern portion of OU2 and the lack of an aquitard to limit the
downward migration of contaminants in the alluvial aquifer. The shallow
wells should be screened near the water table and the deep wells in the lower
third of the single unconfined alluvial aquifer.
b. Installation of one monitoring well pair at Transect 2 (between BH-SF-E-
0305-U and BH-SF-E-0309-U) to better define the mass flux of metals
upgradient of an area that underwent substantial Phase I remedial actions.
The pair should consist of both an upper and lower aquifer well. This would
be a more cost-effective means of assessing water quality migrating through
the single unconfined aquifer to the east, given the well control that already
exists at Transect 2; however, approach l(a) above is recommended if more
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timely data for the upgradient area are needed for remedial decision-making
purposes. Implementation of recommendation l(b) is still recommended even
if l(a) is also implemented.
2. Installation of one monitoring well pair (upper and lower aquifer wells) in the
area between Transects 3 and 5 between existing wells BH-SF-E-0501-U and BH-
SF-E-0503-U would help create another north-south transect of wells stretching
from BH-SF-E-0502-U in the north to BH-SF-E-0501-U in the south.
Groundwater quality in the nearly 1,400-foot wide area between these two
existing wells and downgradient of the slag pile area is uncharacterized.
3. Installation of one monitoring well pair at Transect 5 (between BH-SF-E-0003-U
and BH-SF-E-0001-U) is recommended to better define the mass flux of metals in
the alluvial aquifer along this north-south transect. The two existing wells listed
above are nearly 1,000 feet apart.
4. Installation of at least four new well pairs at Smelterville Flats, each consisting of
an upper and lower aquifer well (eight wells total), is recommended given the
large size of this area and the relatively low number of wells currently present as a
result of the removal action that was performed.
5. Installation of at least one monitoring well pair at Transect 6 approximately
midway between the SFCDR and the southern perimeter of the main valley
alluvial aquifer is recommended to better define the mass flux of metals in the
alluvial aquifer along this north-south transect. There is no well control in the
approximately 700-foot span between existing well BH-SF-W-0201-U and the
edge of the alluvial aquifer. Installation of a well pair along Transect 6 between
the SFCDR and the northern limit of the main valley alluvial aquifer also should
be considered to obtain more detailed groundwater quality data. Transect 6 is
located hydraulically downgradient of the westernmost Phase I remedial action in
an area where the alluvial aquifer is inferred to be relatively constricted.
Therefore, collection of more detailed groundwater quality data along this transect
would be useful in evaluating the effectiveness of Phase I remedial actions and
groundwater quality near the western edge of the Bunker Hill Box.
6. Groundwater quality in the western portion of OU2 between Transects 6 and 7
(and along Transect 7) is relatively poorly characterized. Metal concentrations
that exceed MCLs (but not by much) have been detected at upper aquifer well
BH-SF-W-0201 (Transect 6), and wells further to the west have had few to no
MCL exceedances. The draft CSM report (CH2M Hill, 2005a) states that the
relatively low magnitude of the metals concentrations measured in alluvial aquifer
groundwater at the western end OU2 is not understood. The western extent of
elevated metal concentrations in groundwater is not well characterized, and the
lateral extent of the main valley alluvial aquifer at Transect 7 does not appear to
be well defined. The SFCDR is gaining between Transects 6 and 7, while Pine
Creek appears to be losing. It is likely that at least some of the groundwater
containing metal concentrations in excess of MCLs at Transect 6 discharges to the
SFCDR near and/or west of this transect. Further evaluation of groundwater
quality west of Transect 6 would appear to be justified, given the results obtained
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at Transect 6. This could potentially be performed in a relatively inexpensive
manner by installing and sampling temporary wells and/or by collecting
groundwater grab samples using direct push methods, followed by the installation
of a relatively small number of permanent monitoring wells at select key locations
based on the data obtained.
4.6 LTM PROGRAM FLEXIBILITY
The LTM program recommendations summarized in Tables 4.3 and 4.4 are based on
available data regarding current (and expected future) site conditions. Changing site
conditions (e.g., periods of drought or excessive rainfall or introduction of hydraulic
stresses such as pumping wells) could affect contaminant fate and transport. Therefore,
the LTM program should be reviewed if hydraulic conditions change significantly, and
revised as necessary to adequately track changes in the magnitude and extent of COCs in
environmental media over time. For example, a temporary increase in the frequency of
surface water and groundwater monitoring in the event of an unusually large hydrologic
event should be considered to capture potential effects of dissolved metals releases from
the vadose zone.
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SECTION 5
TEMPORAL STATISTICAL EVALUATION
Chemical concentrations measured at different points in time (temporal data) can be
examined graphically or using statistical tests to evaluate temporal trends. In general, if
removal if contaminant mass is occurring in the subsurface as a consequence attenuation
processes (e.g., metals precipitation) or remedial actions (e.g., source removal), mass
removal will be indicated by a decrease in analyte concentrations through time at a
particular sampling location, as a decrease in analyte concentrations with increasing
distance from source areas, and/or as a change in the suite of analytes detected through
time or with increasing migration distance.
5.1 METHODOLOGY FOR TEMPORAL TREND ANALYSIS OF
CONTAMINANT CONCENTRATIONS
Temporal chemical-concentration data can be evaluated for trends by plotting
contaminant concentrations through time for individual monitoring wells (e.g., Figure
5.1), or by plotting contaminant concentrations versus downgradient distance from the
contaminant source for several wells along the groundwater flowpath over several
monitoring events. Plotting temporal concentration data is recommended for any analysis
of plume stability (Wiedemeier and Haas, 2000); however, visual identification of trends
in plotted data may be a subjective process, particularly if (as is likely) the concentration
data do not exhibit a uniform trend, but are variable through time (Figure 5.2).
The possibility of arriving at incorrect conclusions regarding the fate and transport of
dissolved contaminants on the basis of visual examination of temporal concentration data
can be reduced by examining temporal trends in chemical concentrations using various
statistical procedures, including regression analyses and the Mann-Kendall test for trends.
The Mann-Kendall nonparametric test (Gibbons, 1994) is well-suited for evaluation of
environmental data because the sample size can be small (as few as four data points), no
assumptions are made regarding the underlying statistical distribution of the data, and the
test can be adapted to account for seasonal variations in the data; however seasonal
correction was not appropriate or conducted for this OU2 analysis. The Mann-Kendall
test statistic can be evaluated to determine, at a specified level of confidence, whether a
statistically significant temporal trend is exhibited by contaminant concentrations
detected through time in samples from an individual well. A negative slope (indicating
decreasing contaminant concentrations through time) or a positive slope (increasing
concentrations through time) provides statistical confirmation of temporal trends that may
have been identified visually from plotted data (Figure 5.2). In this analysis, a 90%
confidence level is used to define a statistically significant trend.
5-1
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FIGURE 5.1
ZINC CONCENTRATIONS THROUGH TIME
AT WELL BH-GG-GW-0004
LONG-TERM MONITORING NETWORK OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
0
Jan-QO
Jan-01
Jan-02
Jan-03
Jan-04
Jan-05
Date
5-2
-------
Decreasing Trend
Increasing Trend
No Trend
Confidence Factor
HIGH
Confidence Factor
LOW
Variation
LOW
Variation
HIGH
FIGURE 5.2
CONCEPTUAL REPRESENTATION OF
TEMPORAL TRENDS AND TEMPORAL
VARIATIONS IN CONCENTRATIONS
Long-Term Monitoring Optimization
Bunker Hill Mining and Metallurgical Complex
draw\739732\diffusion\williamsA.cdr pg1 nap 4/3/02
5-3
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The relative value of information obtained from periodic monitoring at a particular
monitoring well can be evaluated by considering the location of the well with respect to
the dissolved contaminant distribution and potential receptor exposure points, and the
presence or absence of temporal trends in contaminant concentrations in samples
collected from the well. The degree to which the amount and quality of information that
can be obtained at a particular monitoring point serves the two primary (i.e.., temporal and
spatial) objectives of monitoring (Section 1) must be considered in this evaluation. For
example, the continued non-detection of a target contaminant in groundwater at a
particular monitoring location provides no information about temporal trends in
contaminant concentrations at that location, or about the extent to which contaminant
migration is occurring, unless the monitoring location lies along a groundwater flowpath
between a contaminant source and a potential receptor exposure point (e.g., downgradient
of a known body of contaminated groundwater). Therefore, a monitoring well having a
history of contaminant concentrations below detection limits may be providing little or no
useful information, depending on its location.
A trend of increasing contaminant concentrations in groundwater at a location
upgradient of a contaminant source or between a contaminant source and a potential
receptor exposure point may represent information critical in evaluating whether
contaminants are migrating to the exposure point, thereby completing an exposure
pathway. Identification of a trend of decreasing contaminant concentrations at the same
location may be useful in evaluating decreases in the areal extent of dissolved
contaminants, but does not represent information that is critical to the protection of a
potential receptor. Similarly, a trend of decreasing contaminant concentrations in
groundwater near a contaminant source may represent important information regarding
the progress of remediation near, and downgradient from, the source. By contrast, the
absence of a statistically significant (as defined by the Mann-Kendall test with a 90%
confidence level) temporal trend in contaminant concentrations at a particular location
within, upgradient or downgradient from a plume indicates that virtually no additional
information can be obtained by frequent monitoring of groundwater at that location, in
that the results of continued monitoring through time are likely to fall within the historic
range of concentrations that have already been detected (Figure 5.3). Continued
monitoring at locations where no temporal trend in contaminant concentrations is present
serves merely to confirm the results of previous monitoring activities at that location.
The temporal trends and relative locations of wells can be weighed to determine if a
well should be retained, excluded, or retained with a reduced sampling frequency. Figure
5.4 presents a flowchart demonstrating the method for using trend results to draw these
conclusions.
5.2 TEMPORAL EVALUATION RESULTS FOR GROUNDWATER WELLS
The analytical data for groundwater samples collected from the 77 groundwater
monitoring wells and 18 surface sampling points in the OU2 LTM program from
February 2000 through October 2004 were examined for temporal trends using the Mann-
Kendall test. The objective of the evaluation was to identify those wells having
increasing or decreasing concentration trends for each COC, and to consider the quality
of information represented by the existence or absence of concentration trends in terms of
the location of each monitoring point. Increasing or decreasing trends are those identified
5-4
-------
c
o
+*
re
+->
c
0)
u
c
o
O
Likely Future
Results
(A
=
CD 2
c =
a g
0£ g
o
O
Historic Results
Time
FIGURE 5.3
CONCEPTUAL REPRESENTATION
OF CONTINUED MONITORING AT
LOCATION WHERE NO TEMPORAL
TREND IN CONCENTRATIONS
IS PRESENT
Long-Term Monitoring Optimization
Bunker Hill Mining and Metallurgical Complex
draw\739732\diffusion\williamsA.cdr pg2 nap 4/3/02
5-5
-------
FIGURE 5.4
TEMPORAL TREND DECISION RATIONALE FLOWCHART
LONG-TERM MONITORING NETWORK OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Exclude/Reduce \
Frequency J
Recent
Concentrations
« MCLs?
Increasing
Trend?
I/ Exclude/Reduce
\^ Frequency
> \^
Recent
Concentrations
«MCLs?
Decreasing
Trend?
Well in Source
Area?
No—w Retain
Downgradient
Sentry Well?
Exclude/Reduce \
Frequency j
Downgradient -^ Y
Sentry Well?
Yes—W Retain
Exclude/Reduce
Downgradient
Sentry Well?
ND or < PQL? V-Yes
Exclude/Reduce
Frequency
5-6
-------
as having positive or negative slopes, respectively, by the Mann-Kendall trend analysis
with a confidence level of 95%; "probably" increasing or decreasing trends are those
identified with a confidence level of 90-95%.
Summary results of Mann-Kendall temporal trend analyses for COCs in groundwater
samples from OU2 are presented in Table 5.1. Table 5.1 also contains the relative
location designation assigned to each well. In general, upper HU wells were designated
as "source" wells, unless they have had no MCL exceedances, in which case they were
designated as "downgradient." Lower wells were also considered to be downgradient
due to their vertical separation from contaminant source areas. Trends for four COCs
(dissolved arsenic, cadmium, lead, and zinc) were evaluated to assess the value of
temporal information provided by each well. As implemented, the algorithm used to
evaluate concentration trends assigned a value of "ND" (not detected) to those wells with
sampling results that were consistently below analytical detection limits through time,
rather than assigning a surrogate value corresponding to the detection limit - a procedure
that could generate potentially misleading and anomalous "trends" in concentrations. In
addition, a value of "
-------
TABLE 5.1
TEMPORAL TREND ANALYSIS OF GROUND WATER MONITORING RESULTS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-DW-GW-0001
BH-GG-GW-0001
BH-GG-GW-0002
BH-GG-GW-0003
BH-GG-GW-0004
BH-GG-GW-0005
BH-GG-GW-0006
BH-GG-GW-0007
BH-GG-GW-0008
BH-ILF-GW-0001
BH-SCA-GW-0001
BH-SCA-GW-0002
BH-SCA-GW-0005
BH-SCA-GW-0006
BH-SCA-GW-0007
BH-SF-E-0001
BH-SF-E-0002
BH-SF-E-0003
BH-SF-E-0101
BH-SF-E-0201
BH-SF-E-0301-U
BH-SF-E-0302-L
BH-SF-E-0305-U
BH-SF-E-0306-L
BH-SF-E-0309-U
BH-SF-E-0310-L
BH-SF-E-0311-U
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0318-U
BH-SF-E-0320-U
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0409-U
BH-SF-E-0410-U
BH-SF-E-0423-U
BH-SF-E-0424-L
BH-SF-E-0425-U
BH-SF-E-0426-L
BH-SF-E-0427-U
BH-SF-E-0428-L
BH-SF-E-0429-U
BH-SF-E-0501-U
BH-SF-E-0502-U
BH-SF-E-0503-U
BH-SF-E-0504-U
BH-SF-W-0001-U
BH-SF-W-0002-L
BH-SF-W-0003-U
BH-SF-W-0004-L
Hydraulic Unit
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Upper
Upper
Upper
Upper
Upper
Single Unconfmed
Single Unconfmed
Single Unconfmed
Single Unconfmed
Single Unconfmed
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Upper
Upper
Upper
Upper
Upper
Lower
Upper
Lower
Relative Location
Downgradient
Upgradient
Source
Source
Source
Source
Downgradient
Source
Downgradient
Downgradient
Upgradient
Source
Source
Source
Downgradient
Upgradient
Upgradient
Upgradient
Source
Source
Source
Downgradient
Source
Downgradient
Source
Downgradient
Downgradient
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Source
Downgradient
Source
Downgradient
Source
Downgradient
Source
Source
Source
Source
Source
Source
Downgradient
Source
Downgradient
Number of
Sampling Results
20
15
18
21
19
45
43
8
8
3
29
38
40
41
27
8
8
8
20
20
22
19
7
8
6
6
8
20
18
9
22
9
20
22
"/
22
22
7
4
9
33
21
8
7
8
35
4
44
43
22
17
17
8
8
8
8
Dissolved
Arsenic
MCL, Zn < MCL, decreasing downgradient
Zinc « MCL, decreasing/no trend Upgradient
Decreasing CD in source area > MCL
Decreasing COCs in source area > MCLs
Decreasing COCs in source area > MCLs
Decreasing COCs in source area > MCLs
Increasing CD MCL
Deceasing CD in source area > MCL
Decreasing COCs in source area > MCLs
As and Pb primarily ND or TR. Decreasing/No Trend downgradient
CD « MCL; Zn low COV; No Trend or < PQL Upgradient
Zn « MCL; No Trend or MCLs
COCs low COVs; No Trend in source area
One detect of Pb « MCL; decreasing or no trend (low COV) downgradient
Most recent Pb ND; low COV no trend in source area
No trend with low COV downgradient
No recommendation. Fewer than 6 measurements.
No recommendation. Fewer than 6 measurements.
No trend with low COV downgradient
Recent NDs Pb; No trend with low COV in source area
Zn « MCL; no trend/decreasing in source area
Decreasing CD around MCL; No trend with low COV in source area.
No Trend in source area (high variation)
Decreasing CD in source area > MCL
Decreasing COCs in source area > MCL
Increasing Zn in source area >MCL
Decreasing COCs in source area > MCL
Probably increasing COCs in source area > MCL
Increasing Cd in source area around MCL
Decreasing COCs in source area > MCL
No recommendation. Fewer than 6 measurements.
Decreasing As in source area >MCL
Decreasing COCs in source area > MCL
Probably increasing As > MCL in source area
CD < MCL; Zn No Trend low COV downgradient
Pb < MCL; no trend in source area
No trend with low COV downgradient
Decreasing Cd trend in source area >MCL
No recommendation. Fewer than 6 measurements.
Increasing As > MCL in source area
Decreasing Zn and Cd >MCL in source area
Decreasing COCs in source area < MCL
Decreasing Zn in source area >MCL
Decreasing COCs in source area > MCLs
Decreasing COCs in source area > MCLs
Decreasing (Cd recent ND) or No Trend low COVs downgradient
No trend with low COV in source area
Decreasing trends downgradient (Zn >MCL)
022/742479/FINAL Bunker Hill Tables.xls/Table 5.1
5-8
-------
TABLE 5.1 (Continued)
TEMPORAL TREND ANALYSIS OF GROUND WATER MONITORING RESULTS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-SF-W-0005-U
BH-SF-W-0006-L
BH-SF-W-0007-U
BH-SF-W-0008-U
BH-SF-W-0009-U
BH-SF-W-0010-U
BH-SF-W-0011-L
BH-SF-W-0018-U
BH-SF-W-0019-U
BH-SF-W-0020-U
BH-SF-W-0104-U
BH-SF-W-0111-U
BH-SF-W-0118-U
BH-SF-W-0119-U
BH-SF-W-0121-U
BH-SF-W-0122-L
BH-SF-W-0201-U
BH-SF-W-0202-L
BH-SF-W-0203-U
BH-SF-W-0204-U
BH-SF-W-0205-L
Hydraulic Unit
Upper
Lower
Upper
Upper
Upper
Upper
Lower
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Lower
Upper
Lower
Upper
Upper
Lower
Relative Location
Source
Downgradient
Source
Source
Source
Source
Downgradient
Source
Downgradient
Downgradient
Source
Source
Source
Source
Downgradient
Downgradient
Source
Downgradient
Downgradient
Downgradient
Downgradient
Number of
Sampling Results
20
8
18
21
22
22
20
20
20
17
19
21
10
10
21
18
8
8
16
"/
1
Dissolved
Arsenic
MCLs
Cd low COV, Decreasing or MCLs
As increasing in source area >MCL
No Trend upgradient (As high COV, recent MCL exceedance)
As increasing in source area >MCL
Cd and Pb recent NDs, Zn No Trend low COV downgradient
CD recent NDs; decreasing downgradient
Cd recent NDs; Zn no trend low COV in source area
Cd recent NDs; Zn no trend low COV downgradient
Zn no trend high variation downgradient (95% confidence) increasing trend in concentrations.
= Statistically significant (90-95% confidence) increasing trend in concentrations.
= Statistically significant (>95% confidence) decreasing trend in concentrations.
= Statistically significant (90-95% confidence) decreasing trend in concentrations.
= Fewer than 6 measurements for COC.
Analytical results contain greater than 50% Non-detects
022/742479/FINAL Bunker Hill Tables.xls/Table 5.1
5-9
-------
Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-U
SF-E-0425-U
SF-E-0429-U
SF-W-(
'•- £>
V-0203-lX^
SF-E-0503-l
• f SF-E-0504-l
*» .SF-E-0502-l
SF-W-0018-U S>
•/3F-W-0201-U l8L>»SF-W-0001-i
* qp W m 04 11-* SF-W-0008-U O
V ^SF-W-0104-U-W SF-W-0003-I
SF-W-0009-U-©
SF-W-0119-L>€)
SF-W-0118-L
SF-'
SF-W-0010-U^
SF-W-0020-U'Q':
SF-W-0019-U
b
SF-W-0005-U
iSF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
•F-E-0407-U
F-E-0321-U
F-E-0322-U
'^xSF-E-0317-L
GT/SF-E-0318-U
G-j^gF^E-OSII;^
SF-E-0409-U
I
CSF-E-0410-USF
A-GW-0005
-E-0305-U
-E-0301-
-E-0320-U
A-GW-0006\ \LF-GW-0001
Lower Unit Wells
F-E-0428-L
GSF-W-0006-L
Legend
Cadmium Mann-Kendall
Trend Result
• Decreasing
• Increasing
O No Trend
O
-------
Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-L
SF-E-0425-UI
SF-E-0429-U
SF-E-0503-l
SF-E-0504-l
*» .SF-E-0502-l
SF-W-0018-UQ i
•F-W-0201-U SF-W-0001-l
SFWmfMlia SF-W-0008-UQ
SF-W-0104-U-W SF-W-0003-I
SF-W-0009-U-©
SF-W-0010-U
SF-W-0020-L>g)
SF-W-0019-Lr^
iSF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
•F-E-0407-U
F-E-0321-U
SF"'
&
*- SF-E-0409-U
CSF-E-041Q4J
:A-GW-0005.
/SF-E-0322-U
_ SF-E-0317-L
O SF-E-0318-U
i-, C O.SF-E-0311-U
SF-E-031_ _
""-E-0314-U
15-U
•F-E-0305-U
F-E*-0301-I
F-E-0320-U
;A-GW-0006\ \LF-GW-0001
Lower Unit Wells
F-E-0428-L
GSF-W-0006-L
Legend
Zinc Mann-Kendall
Trend Result
• Decreasing
o
Increasing
No Trend
o
O <4 Measurements
2,500 5,000 7,500
10,000
Hi Feet
FIGURE 5.6
TEMPORAL TREND RESULTS
FOR ZINC IN GROUNDWATER
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
5-11
-------
temporal information is described in the "Rationale" column of Table 5.1, and a flow
chart of the decision logic applied to the temporal trend analysis results is presented on
Figure 5.4. Trend results for zinc and cadmium were given more weight than those for
the other COCs, given their relatively higher impact; however, the most conservative
trend was used in all cases (e.g., if an arsenic or lead trend resulted in a recommendation
to retain a well, that well would be recommended for retention.)
Wells that have decreasing trends in a source area in which concentrations are above
MCLs (e.g., BH-GG-GW-0002, BH-SF-E-0320-U, and BH-SF-W-0005-U) are valuable
because they provide information on the effectiveness of the remedial actions performed
to date and the effects of significant hydrologic (i.e., precipitation and snowmelt) events
and are thus recommended for retention in the monitoring system. Conversely, wells
located downgradient of the source area that have either decreasing concentrations or
source area wells with a recent history of concentrations significantly below MCLs (e.g.,
BH-SF-W-0004-L, BH-SF-W-0122-L, and BH-SF-W-0201-U) will provide limited
valuable temporal information in the future and are recommended for exclusion or
reduced sampling. Wells with increasing COC concentration trends in the source area
(e.g., BH-SF-E-0321-U, BH-SF-E-0402-U, and BH-SF-W-0118-U) provide valuable
information about the effectiveness of the remediation system and the effects of
significant hydrologic events and areas that should potentially be targeted for Phase II
remediation, and should be retained. Wells with stable (low coefficient of variation), 'no
trend' results (e.g., BH-SF-E-0426-L, BH-SF-W-0121-U, and BH-SF-E-0425-U) were
recommended for exclusion or monitoring reduction because continued frequent
sampling would not likely yield new information, while wells with highly variable COC
concentrations (e.g., wells BH-SF-W-0118-U, BH-SF-W-0203-U) were recommended
for retention.
Table 5.1 summarizes recommendations to retain 36 and exclude or reduce the
frequency for 36 of the 72 wells analyzed in the temporal evaluation (not including the
well with fewer than six measurements). The recommendations provided in Table 5.1 are
based on the evaluation of temporal statistical results only, and must be used in
conjunction with the results of the qualitative and spatial evaluations to generate final
recommendations regarding retention of monitoring points in the LTM program, and the
frequency of monitoring at particular locations in OU2.
5.3 TEMPORAL EVALUATION RESULTS FOR SURFACE WATER
STATIONS
Surface water Mann-Kendall trend results are shown in Table 5.2 for both total and
dissolved COC concentrations. Limited data (six or fewer measurements) were available
for surface water stations BH-IG-0001, BH-JC-0001, BH-PG-001, BH-RR-0001 and SF-
270. Only dissolved COCs results were available for BH-JC-0001. Although the
temporal trend decision rationale shown on Figure 5.4 was developed for application to a
groundwater monitoring network, in this case it was used for the surface water stations by
considering each station as a "downgradient" well, since the stations are mostly located at
the mouths of the tributaries feeding into Bunker Creek or the SFCDR. As a result,
several stations with increasing concentrations above AWQCs were recommended for
retention (e.g., BH-CS-0001, and BH-DW-0001), while those with decreasing
concentrations and/or low temporal variation and no trends were recommended for
5-12
-------
TABLE 5.2
TEMPORAL TREND ANALYSIS OF SURFACE WATER MONITORING RESULTS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Surface Water
Station Name
Exclude/
Reduce
X
Retain
X
X
X
Rationale
Decreasing or low COV no trend
Increasing COCs > standards
Increasing dissolved cadmium above standard
Highly variable cadmium and arsenic; Increasing dissolved arsenic > standard
X
Increasing dissolved cadmium and arsenic > standards
X
Decreasing or low COV no trend
No recommendation. Fewer than 6 measurements.
No recommendation. Fewer than 6 measurements.
X
High number of ND or low COV no trend
X
Increasing lead and dissolved lead > standards
X
Increasing dissolved lead > standards, other COCs low COV no trend
No recommendation. Fewer than 6 measurements.
No recommendation. Fewer than 6 measurements.
X
High number of ND or low COV no trend
SF-270
X
ND or 95% confidence) increasing trend in concentrations.
= Statistically significant (90-95% confidence) increasing trend in concentrations.
= Statistically significant (>95% confidence) decreasing trend in concentrations.
= Statistically significant (90-95% confidence) decreasing trend in concentrations.
= Fewer than 6 measurements for COC.
Analytical results contain greater than 50% Non-detects
FINAL Bunker Hill Tables.xls
5-13
-------
exclusion or reduction from the monitoring program (e.g., BH-WP-0001 and BH-BC-
0001). As with the groundwater well temporal trend results, the recommendations in
Table 5.2 are based on the evaluation of temporal statistical results only, and must be
used in conjunction with the results of the qualitative evaluation to generate final
recommendations regarding retention and sampling frequency of surface water
monitoring stations in the LTM program.
5-14
-------
SECTION 6
SPATIAL STATISTICAL EVALUATION
Spatial statistical techniques also can be applied to the design and evaluation of
groundwater monitoring programs to assess the quality of information generated during
monitoring and to evaluate monitoring networks. Geostatistics, or the theory of
regionalized variables (Clark, 1987; Rock, 1988; American Society of Civil Engineers
Task Committee on Geostatistical Techniques in Hydrology, 1990a and 1990b), is
concerned with variables having values dependent on location, and which are continuous
in space but vary in a manner too complex for simple mathematical description.
Geostatistics is based on the premise that the differences in values of a spatial variable
depend only on the distances between sampling locations, and the relative orientations of
sampling locations - that is, the values of a variable (e.g., chemical concentration)
measured at two locations that are spatially close together - will be more similar than
values of that variable measured at two locations that are far apart.
6.1 GEOSTATISTICAL METHODS FOR EVALUATING MONITORING
networks
Ideally, application of geostatistical methods to the results of the groundwater
monitoring program at OU2 could be used to estimate COC concentrations at every point
within the distribution of dissolved contaminants, and also could be used to generate
estimates of the "error," or uncertainty, associated with each estimated concentration
value. Thus, the monitoring program could be optimized by using available information
to identify those areas having the greatest uncertainty associated with the estimated
plume extent and configuration. Conversely, sampling points could be successively
eliminated from simulations, and the resulting uncertainty examined, to evaluate if
significant loss of information (represented by increasing error or uncertainty in
estimated chemical concentrations) occurs as the number of sampling locations is
reduced. Repeated application of geostatistical estimating techniques, using tentatively
identified sampling locations, then could be used to generate a sampling program that
would provide an acceptable level of uncertainty regarding the distribution of COCs with
the minimum possible number of samples collected. Furthermore, application of
geostatistical methods can provide unbiased representations of the distribution of COCs
at different locations in the subsurface, enabling the extent of COCs to be evaluated more
precisely.
Fundamental to geostatistics is the concept of semivariance [tfh)], which is a measure
of the spatial dependence between sample variables (e.g., chemical concentrations) in a
specified direction. Semivariance is defined for a constant spacing between samples (h)
by:
6-1
-------
y(h) = — JL[g(x) - g(x + h) f Equation 6-1
Where:
y(h) = semivariance calculated for all samples at a distance h from each other;
g(x) = value of the variable in sample at location*;
g(x + h) = value of the variable in sample at a distance h from sample at location x;
and
n = number of samples in which the variable has been determined.
Semivariograms (plots of y(h) versus h) are a means of depicting graphically the range
of distances over which, and the degree to which, sample values at a given point are
related to sample values at adjacent, or nearby, points, and conversely, indicate how close
together sample points must be for a value determined at one point to be useful in
predicting unknown values at other points. For h = 0, for example, a sample is being
compared with itself, so normally y(0) = 0 (the semivariance at a spacing of zero, is
zero), except where a so-called nugget effect is present (Figure 6.1), which implies that
sample values are highly variable at distances less than the sampling interval. Analytical
variability and sampling error can contribute to the nugget. As the distance between
samples increases, sample values become less and less closely related, and the
semivariance therefore increases, until a "sill" is eventually reached, where y(h) equals
the overall variance (i.e., the variance around the average value). The sill is reached at a
sample spacing called the "range of influence," beyond which sample values are not
related. Only values between points at spacings less than the range of influence can be
predicted; but within that distance, the semivariogram provides the proper weightings,
which apply to sample values separated by different distances.
When a semivariogram is calculated for a variable over an area (e.g., concentrations of
lead in OU2 groundwater), an irregular spread of points across the semivariogram plot is
the usual result (Rock, 1988). One of the most subjective tasks of geostatistical analysis
is to identify a continuous, theoretical semivariogram model that most closely follows the
real data. Fitting a theoretical model to calculated semivariance points is accomplished
by trial-and-error, rather than by a formal statistical procedure (Clark, 1987; Rock, 1988).
If a "good" model fit results, then y(h) (the semivariance) can be confidently estimated
for any value of h, and not only at the sampled points.
6-2
-------
FIGURE 6.1
IDEALIZED SEMIVARIOGRAM MODEL
LONG-TERM MONITORING NETWORK OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
3500 n
3000
<£ 2500
£ 2000 H
I 1500
I 1000 H
1 500 H
0
Range
Spherical model
0
500 1000
1500 2000
Distance (ft)
2500 3000 3500
6.2 SPATIAL EVALUATION OF THE MONITORING NETWORK AT OU2
Cadmium and zinc concentrations were used as the indicator chemicals for the spatial
evaluation of the groundwater monitoring network in the OU2 upper HU, and zinc was
used for the lower HU. These COCs were selected because of their relative prevalence
and spatial distribution in the upper and lower HUs in groundwater at OU2. The kriging
evaluation examines a two-dimensional spatial "snapshot" of the data. Therefore, the
most recent (typically 2004) analytical data available at the start of this LTMO evaluation
were used in the kriging evaluation. Two separate kriging analyses were conducted for
the 44 upper HU wells (cadmium and zinc) and one kriging analysis was conducted for
the 14 lower HU wells (zinc). Note that single unconfmed well BH-SF-E-0201 was
included as a lower aquifer well in this analysis because it is screened at a similar depth
to the other lower aquifer wells. The spatial evaluation has a lower limit of 11 wells;
thus, the upland and single unconfmed aquifer well groups did not have adequate spatial
coverage for analysis. A spatial evaluation for the surface water points was not
appropriate because each monitoring station measures water quality at the mouth of a
separate tributary in the drainage system, and thus the points are not spatially correlated.
The commercially available geostatistical software package Geostatistical Analyst™
(an extension to the Arc View® geographic information system [GIS] software package)
(Environmental Systems Research Institute, Inc. [ESRI], 2001) was used to develop
semivariogram models depicting the spatial variation in the upper HU for cadmium and
zinc and in the lower HU for zinc concentrations in groundwater.
6-3
-------
As semivariogram models were calculated for each scenario (Equation 6-1),
considerable scatter of the data was apparent during fitting of the models. Several data
transformations (including a log transformation) were attempted to obtain a
representative semivariogram model. Ultimately, the concentration data were
transformed to "rank statistics," in which, for example, the 14 wells in the lower HU were
ranked from 1 (lowest concentration) to 14 (highest concentration) according to their
most recent zinc concentration. Tie values were assigned the median rank of the set of
ranked values; for example, if five wells had non-detected concentrations, they would
each be ranked "3", the median of the set of ranks: [1,2,3,4,5]. Transformations of this
type can be less sensitive to outliers, skewed distributions, or clustered data than
semivariograms based on raw concentration values, and thus may enable recognition and
description of the underlying spatial structure of the data in cases where ordinary data are
too "noisy."
The rank statistics were used to develop semivariograms that most accurately modeled
the spatial distribution of the data in the three scenarios. Anisotropy was incorporated
into the models to adjust for the directional influence of groundwater flow to the west.
Note that the minor ranges used in these variogram models are not intended to be
considered for well spacing between the transects. The parameters for best-fit
semivariograms for the three spatial evaluations are listed in Table 6.1.
TABLE 6.1
BEST-FIT SEMIVARIOGRAM MODEL PARAMETERS
LONG-TERM MONITORING NETWORK OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
Parameter
Model
Range (ft)
Sill
Nugget
Minor Range (ft)
Direction (°)
Upper HU
Zinc
Spherical
5500
194
41
3500
272
Upper HU
Cadmium
Circular
8500
115
105
3500
272
Lower HU
Zinc
Exponential
5500
18
1.1
3000
272
After the semivariogram models were developed, they were used in the kriging system
implemented by the Geostatistical Analyst™ software package (ESRI, 2001) to develop
two-dimensional kriging realizations (estimates of the spatial distribution of zinc or
cadmium in groundwater at OU2), and to calculate the associated kriging prediction
standard errors. The median kriging standard deviation was obtained from the standard
errors calculated using the entire monitoring network for each scenario (e.g., the 14 wells
in the lower HU). Next, each of the wells was sequentially removed from the network,
and for each resulting well network configuration, a kriging realization was completed
using the COC concentration rankings from the remaining wells. The "missing-well"
monitoring network realizations were used to calculate prediction standard errors, and the
median kriging standard deviations were obtained for each "missing-well" realization and
compared with the median kriging standard deviation for the "base-case" realization
6-4
-------
(obtained using the complete monitoring network), as a means of evaluating the amount
of information loss (as indicated by increases in kriging error) resulting from the use of
fewer monitoring points.
Figure 6.2 illustrates an example of the spatial-evaluation procedure by showing
kriging prediction standard-error maps for three kriging realizations for the lower HU
wells. Note that maps A through C in Figure 6.2 are not a representation of COC
distribution, but standard-error, which show the error associated with the kriging
predicted distribution. Each map shows the predicted standard error associated with a
given group of wells based on the semivariogram parameters discussed above. Lighter
colors represent areas with lower spatial uncertainty, and darker colors represent areas
with higher uncertainty; regions in the vicinity of wells (i.e., data points) have the lowest
associated uncertainty. Map A on Figure 6.2 shows the predicted standard error map for
the "base-case" realization in which all 14 wells are included. Map B shows the
realization in which well BH-SF-E-0426-L was removed from the monitoring network,
and Map C shows the realization in which well BH-SF-W-011-L was removed. Figure
6.2 shows that when a well is removed from the network, the predicted standard error in
the vicinity of the missing well increases (as indicated by a darkening of the shading in
the vicinity of that well). If a "removed" (missing) well is in an area with several other
wells (e.g.., well BH-SF-E-0426-L; Map B on Figure 6.2), the predicted standard error
may not increase as much as if a well (e.g., BH-SF-W-0011-L; Map C) is removed from
an area with fewer surrounding wells.
Based on the kriging evaluation, each well received a relative value of spatial
information "test statistic" calculated from the ratio of the median "missing well" error to
median "basecase" error. If removal of a particular well from the monitoring network
caused very little change in the resulting median kriging standard deviation, the test
statistic equals one, and that well was regarded as contributing only a limited amount of
information to the LTM program. Likewise, if removal of a well from the monitoring
network produced larger increases in the kriging standard deviation (more than 1
percent), this was regarded as an indication that the well contributes a relatively greater
amount of information and is relatively more important to the monitoring network. At
the conclusion of the kriging realizations, each well was ranked from 1 (providing the
least information) to the number of wells included in the zone analysis (providing the
most information), based on the amount of information (as measured by changes in
median kriging standard deviation) the well contributed toward describing the spatial
distribution of COCs, as shown in Tables 6.2 to 6.4. Wells providing the least amount of
information represent possible candidates for exclusion from the monitoring network at
OU2.
6.3 SPATIAL STATISTICAL EVALUATION RESULTS
Figures 6.3 through 6.5 and Tables 6.2 to 6.4 present the test statistics and associated
rankings of the evaluated subsets of monitoring locations (zinc in the upper HU,
cadmium in the upper HU, and zinc in the lower HU, respectively). The wells are ranked
from least to most spatially relevant based on the relative value of the associated recent
COC information provided by each well, as calculated based on the kriging realizations.
Examination of these results indicate that monitoring wells in close proximity to several
6-5
-------
A) Basecase (all wells)
B) Missing well BH-SF-E-0426-L: relative small change in spatial
uncertainty
C) Missing well BH-SF-W-011-L: relative large change in spatial
uncertainty
Legend
Well missing from
O
kriging realization
Predicted Standard Error Map
Less spatial uncertainty
Greater spatial uncertainty
FIGURE 6.2
IMPACT OF MISSING WELLS
ON PREDICTED STANDARD ERROR
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
PARSONS
6-6
-------
TABLE 6.2
RESULTS OF GEOSTATISTICAL EVALUATION RANKING OF WELLS
BY RELATIVE VALUE OF ZINC IN THE UPPER HU
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name "'
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0425-U
BH-SF-E-0503-U
BH-SF-E-0504-U
BH-SF-E-0501-U
BH-SF-E-0318-U
BH-SF-E-0322-U
BH-SF-E-0409-U
BH-SF-E-0427-U
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-W-0003-U
BH-SF-W-0005-U
BH-SF-E-0309-U
BH-SF-E-0321-U
BH-SF-E-0423-U
BH-SF-W-0020-U
BH-SF-E-0311-U
BH-SF-E-0429-U
BH-SF-E-0305-U
BH-SF-W-0012-U
BH-SF-W-0121-U
BH-SF-E-0317-U
BH-SF-E-0502-U
BH-SF-E-0301-U
BH-SF-E-0320-U
BH-SF-W-0007-U
BH-SF-W-0201-U
BH-SF-W-0204-U
BH-SF-W-0119-U
BH-SF-W-0010-U
BH-SF-W-0001-U
BH-SF-E-0410-U
BH-SF-W-0018-U
BH-SF-W-0118-U
BH-SF-W-0008-U
BH-SF-W-0009-U
BH-SF-W-0203-U
BH-SF-W-0104-U
BH-SF-W-0111-U
Kriging
Metric
0.99992
0.99992
0.99994
0.99997
0.99997
0.99998
0.99999
0.99999
1.00000
1.00012
1.00016
1.00016
1.00017
1.00035
1.00035
1.00054
1.00084
1.00086
1.00121
1.00129
1.00155
1.00156
1.00172
1.00177
1.00209
1.00233
1.00313
1.00371
1.00445
1.00621
1.00634
1.00642
1.00703
1.00900
1.00961
1.00966
1.01043
1.01092
1.01270
1.01285
1.01360
1.01385
1.01443
1.01444
Kriging
Ranking "
1.5C/
1.5
3
4.5
4.5
6
7.5
7.5
9
10
11.5
11.5
13
14.5
14.5
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
Exclude
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
d/
-
—
-
—
-
—
-
—
-
—
-
—
-
Retain
—
-
—
-
—
-
—
-
—
-
—
-
—
-
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Well set includes upper aquifer wells designated in Table 3.1.
1= least relative amount of information; 44= most relative amount of information
Tie values receive the median ranking of the set.
Well in the "intermediate" range; received no recommendation for excludsion or retention
(see Section 6.2).
FINAL Bunker Hill Tables.xls
6-7
-------
TABLE 6.3
RESULTS OF GEOSTATISTICAL EVALUATION RANKING OF WELLS BY RELATIVE VALUE OF CADMIUM
IN THE UPPER HU
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name "
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0427-U
BH-SF-E-0501-U
BH-SF-E-0318-U
BH-SF-E-0322-U
BH-SF-E-0425-U
BH-SF-E-0409-U
BH-SF-E-0503-U
BH-SF-E-0504-U
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-W-0003-U
BH-SF-E-0309-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0321-U
BH-SF-E-0423-U
BH-SF-E-0429-U
BH-SF-W-0005-U
BH-SF-E-0311-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0410-U
BH-SF-E-0305-U
BH-SF-W-0007-U
BH-SF-E-0502-U
BH-SF-E-0301-U
BH-SF-W-0001-U
BH-SF-E-0320-U
BH-SF-W-0204-U
BH-SF-W-0020-U
BH-SF-W-0012-U
BH-SF-W-0121-U
BH-SF-W-0119-U
BH-SF-W-0203-U
BH-SF-W-0118-U
BH-SF-W-0010-U
BH-SF-W-0201-U
BH-SF-W-0018-U
BH-SF-W-0008-U
BH-SF-W-0009-U
BH-SF-W-0104-U
BH-SF-W-0111-U
Kriging
Metric
0.99996
0.99996
0.99998
0.99998
0.99999
1.00000
1.00000
1.00001
1.00007
1.00007
1.00013
1.00013
1.00017
1.00019
1.00019
1.00019
1.00026
1.00028
1.00028
1.00029
1.00033
1.00044
1.00050
1.00085
1.00091
1.00095
1.00098
1.00166
1.00170
1.00175
1.00180
1.00205
1.00207
1.00209
1.00251
1.00265
1.00293
1.00360
1.00373
1.00384
1.00548
1.00633
1.00763
1.00774
Kriging
Ranking
1.5C/
1.5
3.5
3.5
5
6.5
6.5
8
9.5
9.5
11.5
11.5
13
15
15
15
17
18.5
18.5
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
Exclude
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
d/
-
-
—
-
-
—
-
-
-
-
—
-
Retain
-
-
-
—
-
-
—
-
-
-
-
—
-
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Well set includes upper aquifer wells designated in Table 3.1.
1= least relative amount of information; 44= most relative amount of information.
c Tie values receive the median ranking of the set.
Well in the "intermediate" range; received no recommendation for excludsion or retention.
(see Section 6.2).
FINAL Bunker Hill Tables.xls
-------
TABLE 6.4
RESULTS OF GEOSTATISTICAL EVALUATION RANKING OF WELLS
BY RELATIVE VALUE OF ZINC IN THE LOWER HU
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name a/
BH-SF-E-0426-L
BH-SF-E-0306-L
BH-SF-W-0004-L
BH-SF-E-0302-L
BH-SF-E-0201
BH-SF-E-0428-L
BH-SF-W-0006-L
BH-SF-E-0424-L
BH-SF-W-0122-L
BH-SF-W-0202-L
BH-SF-W-0205-L
BH-SF-W-0002-L
BH-SF-E-0310-L
BH-SF-W-0011-L
Kriging
Metric
0.99715
1.00072
1.00140
1.00183
1.00258
1.00520
1.00947
1.00954
1.00986
1.01029
1.01660
1.01831
1.02064
1.02835
Kriging
Ranking b/
1
2
o
5
4
5
6
7
8
9
10
11
12
13
14
Exclude
X
X
X
X
X
c/
—
~
~
Retain
~
—
~
~
X
X
X
X
X
a Well set includes lower aquifer wells designated in Table 3.1,
and single unconfined aquifer well BH-SF-E-0201.
b/1= least relative amount of information; 14= most relative amount of information.
c/ Well in the "intermediate" range; received no recommendation for excludsion or retention.
(see Section 6.2).
FINAL Bunker Hill Tables.xls
6-9
-------
BH-SF-E-0425-U
BH-SF-E-0423-U
H-SF-W-0203-U
QBH-SF-W-0201-U
OBH-SF-W-0121-U
BH-SF-W
BH-SF-E-0429-U
BH-SF-E-0502-U
BH-SF-W-0008-u^
BH-SF-W-0104-U BH-SF-W-0001-UO
BH-SF-W-0009-U>^
BH-SF-W-0003-U O
Legend
riging Ranking
K
1-9 Least value of spatial information
10-15
16-29
30-37
/• 38-44 Most value of spatial information
0 1,250 2,500 5,000 7,500 10,000
1 inch equals 3,000 feet
-SF-W-0020-U
BH-SF-W-0019-U
BH-SF-E-0408-U
I-SF-E-0407-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0317-
H-SF-E-0314-U
BH-SF-E-0315-U
-0—BH-SF-E-0311-U
l-SF-£-0318-U
BH-SF-E-0503-U
BH-SF-E-0504-U
BH-SF-E-0501-U
BH-SF-E-0309-U
OBH-SF-E-0316-U
OBH-SF-E-0305-U
OBH-SF-E-0320-U
^^ \ "^BH-SF-E-0301-U
\Btf-EP*E-,
ht6F-E-C
FIGURE 6.3
GEOSTATISTICAL EVALUATION
RESULTS SHOWING RELATIVE
VALUE OF SPATIAL INFORMATION
ON ZINC DISTRIBUTION
UPPER HU WELLS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
6-10
-------
BH-SF-E-0425-U
BH-SF-E-0423-U
BH-SF-W
SF-W-0203-U
(BH-SF-W-0201-
OBH-SF-W-0121-U
BH-SF-E-0429-U
BH-SF-E-0502-U
^ I_M |-\JI -'
SF-W-0118-U--®
BH-SF-W-0008-u^
BH-SF-W-0104-U BH-SF-W-0001
BH-SF-W-0009-U
BH-SF-W-0003-U •
Legend
riging Ranking
K
1-9 Least value of spatial information
10-15
16-29
30-37
/• 38-44 Most value of spatial information
0 1,250 2,500 5,000 7,500 10,000
1 inch equals 3,000 feet
BH-SF-E-0408-U
I-SF-E-0407-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0317-
H-SF-E-0314-U
BH-SF-E-0315-U
-0—BH-SF-E-0311-U
l-SF-i-0318-U
BH-SF-E-0503-U
BH-SF-E-0504-U
BH-SF-E-0501-U
BH-SF-E-0309-U
OBH-SF-E-0316-U
OBH-SF-E-0305-U
OBH-SF-E-0320-U
"^BH-SF-E-0301-U
3H-SF-E-0409-U
/"•• W
H-SF-E-0410-U
FIGURE 6.4
GEOSTATISTICAL EVALUATION
RESULTS SHOWING RELATIVE
VALUE OF SPATIAL INFORMATION
ON CADMIUM DISTRIBUTION
UPPER HU WELLS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
6-11
-------
BH-SF-W-020
BH-SF-W-0122-L
Legend
Kriging Ranking
• 1-4 Least value of spatial information
O 5-9
0 10-14 Most value of spatial information
BH-SF-W-0002-L
BH-SF-W-0004-L *BH-SF-E-0426-L
OBH-SF-W-0006-L
BH-SF-E-0310-L
BH-SF-E-0201 v
0 1,250 2,500
5,000
7,500
10,000
1 inch equals 3,000 feet
FIGURE 6.5
GEOSTATISTICAL EVALUATION
RESULTS SHOWING RELATIVE
VALUE OF SPATIAL INFORMATION
ON ZINC DISTRIBUTION
LOWER HU WELLS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
6-12
-------
other monitoring wells (e.g., red color coding on Figures 6.3 to 6.5) generally provide
relatively lesser amounts of information than do wells at greater distances from other
wells or wells located in areas having limited numbers of monitoring points (e.g., blue
color coding on Figures 6.3 to 6.5). This is intuitively obvious, but the analysis allows
the most valuable and least valuable wells to be identified quantitatively. For example,
Table 6.2 identifies the wells ranked below 15 that provide the relative least amount of
information, and the wells ranked at or above 30 that provide the greatest amount of
relative information regarding the occurrence and distribution of zinc in groundwater
among those wells in the upper HU. The lowest-ranked wells are potential candidates for
exclusion from the OU2 groundwater monitoring program, and the highest-ranked wells
are candidates for retention in the monitoring program; intermediate-ranked wells receive
no recommendation for removal or retention in the monitoring program based on the
spatial analysis. Note that these recommendations are based only on the statistical
evaluation and must be used in conjunction with the results of the qualitative and
temporal evaluations to generate final recommendations regarding retention and sampling
frequency of monitoring stations in the LTM program. Table 6.5 summarizes the ranking
and recommendations for the spatial evaluation of both metals analyzed in the upper HU.
In the situations where a upper HU well was recommended for removal or retention in
both analyses, it received a classification of "ZC" in the appropriate column. If a well
was recommended for removal or retention in just the zinc or the cadmium analysis, it
received a "Z" or a "C,' respectively. The spatial results for the metals were consistent in
that no well was recommended for removal based on one metal and retention based on
the other.
6-13
-------
TABLE 6.5
SUMMARY RESULTS OF GEOSTATISTICAL EVALUATION RANKING OF WELLS BY
RELATIVE VALUE OF CADMIUM AND ZINC IN THE UPPER HU
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-SF-E-0301-U
BH-SF-E-0305-U
BH-SF-E-0309-U
BH-SF-E-0311-U
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0318-U
BH-SF-E-0320-U
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0409-U
BH-SF-E-0410-U
BH-SF-E-0423-U
BH-SF-E-0425-U
BH-SF-E-0427-U
BH-SF-E-0429-U
BH-SF-E-0501-U
BH-SF-E-0502-U
BH-SF-E-0503-U
BH-SF-E-0504-U
BH-SF-W-0001-U
BH-SF-W-0003-U
BH-SF-W-0005-U
BH-SF-W-0007-U
BH-SF-W-0008-U
BH-SF-W-0009-U
BH-SF-W-0010-U
BH-SF-W-0012-U
BH-SF-W-0018-U
BH-SF-W-0020-U
BH-SF-W-0104-U
BH-SF-W-0111-U
BH-SF-W-0118-U
BH-SF-W-0119-U
BH-SF-W-0121-U
BH-SF-W-0201-U
BH-SF-W-0203-U
BH-SF-W-0204-U
Zinc
Kriging
Ranking
29
24
18
22
11.5
11.5
13
27
7.5
30
19
7.5
14.5
14.5
1.5
1.5
9
37
20
3
10
23
6
28
4.5
4.5
36
16
17
31
40
41
35
25
38
21
43
44
39
34
26
32
42
33
Exclude
-
-
-
-
X
X
X
—
X
-
X
X
X
X
X
X
-
X
X
-
X
—
X
X
-
-
-
-
-
Retain
-
-
-
-
—
X
-
X
-
-
—
X
-
-
X
X
X
X
-
X
-
X
X
X
X
-
X
X
X
Cadmium
Kriging
Ranking
28
25
15
21
11.5
11.5
22
23
5
30
17
6.5
15
15
1.5
1.5
8
24
18.5
6.5
3.5
18.5
3.5
27
9.5
9.5
29
13
20
26
41
42
38
33
40
32
43
44
37
35
34
39
36
31
Exclude
-
-
X
-
X
X
-
—
X
-
X
X
X
X
X
X
-
-
X
X
-
X
—
X
X
-
X
-
-
Retain
-
-
-
-
—
X
-
-
-
-
—
-
-
-
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Summary
Exclude
-
-
ca/
-
zc
zcb/
zd
—
zc
-
zc
zc
zc
zc
zc
zc
-
zc
zc
-
zc
—
zc
zc
c
-
Retain
-
-
-
—
ZC
-
z
-
-
—
z
-
z
zc
zc
zc
c
zc
c
zc
zc
zc
zc
c
zc
zc
zc
bl
C = well identified for exclusion or retention in cadmium analysis only.
ZC = well identified for exclusion or retention in both cadmium and zinc analyses.
' C = well identified for exclusion or retention in zinc analysis only.
6-14
FINAL Bunker Hill Tables.xls
-------
SECTION 7
SUMMARY OF LONG-TERM MONITORING OPTIMIZATION
EVALUATION
Seventy-seven groundwater monitoring wells and 18 surface water stations at OU2
were evaluated qualitatively using hydrogeologic, hydrologic, and contaminant
information, and quantitatively using temporal and spatial statistical techniques. As each
tier of the evaluation was performed, monitoring points that provide relatively greater
amounts of information regarding the occurrence and distribution of COCs in
groundwater and surface water were identified, and were distinguished from those
monitoring points that provide relatively lesser amounts of information. In this section,
the results of the evaluations are combined to generate a refined monitoring program that
potentially could provide information sufficient to address the primary objectives of
monitoring, at reduced cost. Monitoring points not retained in the refined monitoring
network could be removed from the monitoring program with relatively little loss of
information and without sacrificing achievement of monitoring objectives.
7.1 GROUNDWATER MONITORING NETWORK SUMMARY
The results of the qualitative, temporal, and spatial evaluations for the groundwater
monitoring wells are summarized in Table 7.1, along with the final recommendations for
sampling point retention or exclusion and sampling frequency. These final
recommendations are also shown on Figure 7.1. The results of the evaluations were
combined and summarized in accordance with the decision logic shown on Figure 7.2
and described below.
1. Each well retained in the monitoring network on the basis of the qualitative
hydrogeologic evaluation was recommended to be retained in the refined
monitoring program.
2. Those wells recommended for exclusion from the monitoring program on the
basis of all three evaluations, or on the basis of the qualitative and temporal
evaluations (with no recommendation resulting from the spatial evaluation)
were recommended for removal from the monitoring program.
3. If a well was recommended for removal based on the qualitative evaluation and
recommended for retention based on the temporal and/or spatial evaluation, the
final recommendation was based on a case-by-case review of well information.
7-1
-------
TABLE 7.1
SUMMARY OF LONG TERM MONITORING OPTIMIZATION EVALUATION OF THE OU2 GROUNDWATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
Hydrologic Unit
Deadwood Gulch Upland Aquifer
BH-DW-GW-0001 [Upland
Government Gulch Upland Aquifer
BH-GG-GW-0001
BH-GG-GW-0002
BH-GG-GW-0003
BH-GG-GW-0004
BH-GG-GW-0005
BH-GG-GW-0006
BH-GG-GW-0007
BH-GG-GW-0008
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Upland
Current
Sampling
Frequency
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Qualitative Evaluation
Exclude
Retain
Recommended
Monitoring
Frequency
X
X
X
X
X
X
X
X
X
annual
biennial
annual
annual
annual
annual
annual
annual
annual
Upland Aquifer between Deadwood and Railroad Gulches
BH-ILF-GW-0001 [Upland
Upland Aquifer at the Smelter Closure Area
BH-SCA-GW-0001
BH-SCA-GW-0002
BH-SCA-GW-0005
BH-SCA-GW-0006
BH-SCA-GW-0007
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 1
BH-SF-E-0001
BH-SF-E-0002
BH-SF-E-0003
Single Unconfmed
Single Unconfmed
Single Unconfmed
Quarterly
Quarterly
Quarterly
Transect 1 to Transect 2
BH-SF-E-0101
BH-SF-E-0201
Transect 2
BH-SF-E-0301-U
BH-SF-E-0302-L
BH-SF-E-0305-U
BH-SF-E-0306-L
BH-SF-E-0309-U
BH-SF-E-0310-L
BH-SF-E-0311-U
Single Unconfmed
Single Unconfmed
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 2 to Transect 3
BH-SF-E-0314-U
BH-SF-E-0315-U
BH-SF-E-0316-U
BH-SF-E-0317-U
BH-SF-E-0318-U
BH-SF-E-0320-U
Upper
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
X
X
X
X
X
X
semiannual
biennial
semiannual
semiannual
semiannual
semiannual
X
X
X
annual
annual
exclude
X
X
X
X
X
X
X
X
X
semiannual
semiannual
semiannual
annual
semiannual
annual
semiannual
annual
annual
X
X
X
X
X
X
semiannual
exclude
semiannual
semiannual
semiannual
semiannual
Temporal Evaluation
Exclude/
Reduce
X
X
X
X
X
Retain
X
X
X
X
Not Analyzed
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Not Analyzed
Not Analyzed
X
X
X
X
X
X
X
Spatial Evaluation
Exclude
Retain
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
Not included
X
—
X
—
X
c37
—
—
—
X
—
zc
zcb/
zc/
—
zc
—
ZC
Summary
Exclude
Retain
Recommended
Monitoring
Frequency
Rationale
X
X
X
X
X
X
X
X
X
Annual
Biennial
Annual
Annual
Annual
Annual
Annual
Annual
Annual
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Qualitative factor overrides statistics recommendations. Phase I remediation established well enough to justify lower frequency.
Qualitative factor overrides statistics recommendations. Phase I remediation established well enough to justify lower frequency.
Qualitative factor overrides statistics recommendations. Phase I remediation established well enough to justify lower frequency.
Qualitative factor overrides statistics recommendations. Phase I remediation established well enough to justify lower frequency.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
X
X
X
X
X
X
Semiannual
Biennial
Semiannual
Semiannual
Semiannual
Semiannual
Reevaluate for temporal trends once more data has been obtained.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Well is serving as downgradient sentry well for SCA. Qualitative factor overrides statistics recommendations.
X
X
X
Annual
Annual
Exclude
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
X
X
X
X
X
X
X
X
X
Semiannual
Semiannual
Semiannual
Annual
Semiannual
Annual
Semiannual
Annual
Annual
Well is spatially important. Qualitative factor overrides temporal statistics.
Temporal statistics confirm qualitative analysis.
Qualitative factor (Phase II remediation) overrides statistics recommendations.
Temporal statistics confirm qualitative analysis.
Qualitative factor (Phase II remediation) overrides statistics recommendations.
Statistics confirm qualitative analysis.
Qualitative factor overrides spatial statistics recommendations.
Spatial statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
X
X
X
X
X
X
Semiannual
Exclude
Semiannual
Semiannual
Semiannual
Semiannual
Additional considerations in qualitative evaluation override temporal statistics
Statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
FINAL Bunker Hill Tables.xls
7-2
-------
TABLE 7.1 (Continued)
SUMMARY OF LONG TERM MONITORING OPTIMIZATION EVALUATION OF THE OU2 GROUNDWATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-SF-E-0321-U
BH-SF-E-0322-U
BH-SF-E-0402-U
BH-SF-E-0403-U
BH-SF-E-0407-U
BH-SF-E-0408-U
BH-SF-E-0409-U
BH-SF-E-0410-U
Hydrologic Unit
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Current
Sampling
Frequency
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 3
BH-SF-E-0423-U
BH-SF-E-0424-L
BH-SF-E-0425-U
BH-SF-E-0426-L
BH-SF-E-0427-U
BH-SF-E-0428-L
Upper
Lower
Upper
Lower
Upper
Lower
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 3 to Transect 5
BH-SF-E-0429-U
BH-SF-E-0501-U
BH-SF-E-0502-U
BH-SF-E-0503-U
BH-SF-E-0504-U
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 5
BH-SF-W-0001-U
BH-SF-W-0002-L
BH-SF-W-0003-U
BH-SF-W-0004-L
BH-SF-W-0005-U
BH-SF-W-0006-L
BH-SF-W-0007-U
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Transect 5 to Transect 6
BH-SF-W-0008-U
BH-SF-W-0009-U
BH-SF-W-0010-U
BH-SF-W-0011-L
BH-SF-W-0019-U
BH-SF-W-0018-U
BH-SF-W-0020-U
BH-SF-W-0104-U
BH-SF-W-0111-U
BH-SF-W-0118-U
BH-SF-W-0119-U
Upper
Upper
Upper
Lower
Upper
Upper
Upper
Upper
Upper
Upper
Upper
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Qualitative Evaluation
Exclude
X
X
Retain
X
X
X
X
X
X
Recommended
Monitoring
Frequency
semiannual
annual
semiannual
exclude
semiannual
exclude
semiannual
semiannual
X
X
X
X
X
X
semiannual
annual
semiannual
annual
semiannual
annual
X
X
X
X
X
semiannual
semiannual
semiannual
semiannual
exclude
X
X
X
X
X
X
X
semiannual
annual
semiannual
annual
semiannual
annual
annual
X
X
X
X
X
X
X
X
X
X
X
semiannual
semiannual
semiannual
annual
exclude
exclude
exclude
semiannual
semiannual
semiannual
semiannual
Temporal Evaluation
Exclude/
Reduce
Retain
X
X
X
X
X
Not Analyzed
X
X
X
X
X
X
X
Not Analyzed
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
X
X
X
X
X
X
Spatial Evaluation
Exclude
—
zc
zc
zc
zc
zc
zc
Retain
—
z
—
—
zc
X
zc
—
—
—
—
—
zc
—
zc
zc
—
—
c
X
—
—
z
X
—
—
z
zc
zc
zc
X
c
zc
c
zc
zc
zc
zc
Summary
Exclude
X
X
Retain
X
X
X
X
X
X
Recommended
Monitoring
Frequency
Semiannual
Annual
Semiannual
Exclude
Semiannual
Exclude
Semiannual
Semiannual
Rationale
Temporal statistics confirm qualitative analysis.
Spatial statistics confirm qualitative analysis. Qualitative factor overrides temporal statistics recommendations.
Temporal statistics confirm qualitative analysis.
Same trends in BH-SF-402-U. Qualitative factor override temporal statistics recommendation.
Temporal statistics confirm qualitative analysis.
Spatial statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
X
X
X
X
X
X
Semiannual
Annual
Semiannual
Annual
Semiannual
Annual
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Qualitative factor (Phase II remediation) overrides temporal statistics recommendations.
Statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
X
X
X
X
X
Semiannual
Semiannual
Semiannual
Semiannual
Exclude
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Same trends in BH-SF-402-U. Qualitative factor override temporal statistics recommendation.
X
X
X
X
X
X
X
Semiannual
Annual
Semiannual
Annual
Annual
Annual
Annual
Statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
Qualitative factor (Phase II remediation) overrides temporal statistics recommendations.
Statistics confirm qualitative analysis.
Temporal statistics justify reduced monitoring frequency
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis; qualitative factors override spatial statistics.
X
X
X
X
X
X
X
X
X
X
X
Semiannual
Semiannual
Semiannual
Annual
Exclude
Exclude
Exclude
Semiannual
Semiannual
Semiannual
Semiannual
Statistics confirm qualitative analysis.
Spatial statistics confirm qualitative analysis. Phase II considerations override temporal statistics.
Statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis; qualitative factors override spatial statistics.
Temporal statistics confirm qualitative analysis; qualitative factors override spatial statistics.
Temporal statistics confirm qualitative analysis; qualitative factors override spatial statistics.
Statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
FINAL Bunker Hill Tables.xls
7-3
-------
TABLE 7.1 (Continued)
SUMMARY OF LONG TERM MONITORING OPTIMIZATION EVALUATION OF THE OU2 GROUNDWATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Well Name
BH-SF-W-0121-U
BH-SF-W-0122-L
Hydrologic Unit
Upper
Lower
Current
Sampling
Frequency
Quarterly
Quarterly
Transect 6
BH-SF-W-0201-U
BH-SF-W-0202-L
Upper
Lower
Quarterly
Quarterly
Transect 6 to Transect 7
BH-SF-W-0203-U |Upper [Quarterly
Transect 7
BH-SF-W-0204-U
BH-SF-W-0205-L
Upper
Lower
Quarterly
Quarterly
Qualitative Evaluation
Exclude
Retain
X
X
Recommended
Monitoring
Frequency
annual
annual
X
X
semiannual
annual
X
annual
X
X
annual
annual
Temporal Evaluation
Exclude/
Reduce
X
X
X
X
X
0
Retain
X
X
Spatial Evaluation
Exclude
—
Retain
C
—
zc
X
zc
zc
X
Summary
Exclude
Retain
X
X
Recommended
Monitoring
Frequency
Annual
Annual
Rationale
Statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
X
X
Semiannual
Annual
Spatial statistics confirm qualitative analysis. Phase II considerations override temporal statistics.
Statistics confirm qualitative analysis.
X
Annual
Statistics confirm qualitative analysis.
X
X
Annual
Annual
Statistics confirm qualitative analysis.
Statistics confirm qualitative analysis.
New Wells (Recommended for Installation) Add
Single Unconfmed # 1
Single Unconfmed #2
Single Unconfmed #3
Single Unconfmed #4
Transect 2 #1
Transect 2 #2
Transect 3-5 #1
Transect 3-5 #2
Transect 5 #1
Transect 5 #2
Transect 6 #1
Transect 6 #2
Transect 6 #3
Transect 6 #4
Smelterfille Flats #1
Smelterfille Flats #2
Smelterfille Flats #3
Smelterfille Flats #4
Smelterfille Flats #5
Smelterfille Flats #6
Smelterfille Flats #7
Smelterfille Flats #8
Single Unconfmed
Single Unconfmed
Single Unconfmed
Single Unconfmed
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
NA47
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
semiannual
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
New well recommended for addition to monitoring program.
C = well identified for exclusion or retention in cadmium analysis only.
ZC = well identified for exclusion or retention in both cadmium and zinc analyses.
0 C = well identified for exclusion or retention in zinc analysis only.
NA=not applicable.
FINAL Bunker Hill Tables.xls
7-4
-------
Upper, Upland, Single Unconfined and SCA Unit Wells
SF-E-0427-U
SF-E-0425-U
SF-E-0429-U
SF-W-0018-l
•F-W-0201-U _*.
kSF-W-0104-UA
SF-W-0009-uA"
SF-E-0503-I
• I SF-E-0504-I
* *.£ '- .SF-E-0502-I
-U-FI
L>USF-W-0001-U
SF-W-0008-U
u4/ ~~ak
,u/s^^ffl
•SF-E-0423-U
F-E-0402-U
F-E-0403-U
F-E-0408-U
F-E-0407-U
F-E-0321-U
.SF-E-0317-
A SF-E-Q318-U
/. A OSF-E
SF-E
ASF-E-041
:A-GW-0005
F-E-0305-U
F-E-0301-
F-E-0320-U
LF-GW-0001
-GW-0001
^GG-GW-0001
Lower Unit Wells
^BF-W-0205-t
Legend
Combined Evaluation
Sampling Frequency Recommendation
• Biennial
• Annual
A Semiannual
D Exclude
0 1,2502,500 5,000 7,500 10,000
FIGURE 7.1
COMBINED EVALUATION
SAMPLING FREQUENCY
RECOMMENDATIONS FOR
GROUNDWATER WELLS
LONG TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
7-5
-------
FIGURE 7.2
COMBINED EVALUTION SUMMARY DECISION LOGIC
LONG-TERM MONITORING NETWORK OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX
Retain Monitoring Point
(Increase Frequency on a Case-
by-Case Basis)
Reduce Monitoring Frequency
(Case-By-Case)
Exclude Well from Future
Sampling
4. If a well was recommended for retention based on the qualitative evaluation and
recommended for removal based on the temporal and/or spatial evaluation, the
well was recommended to be retained, but the possibility of reducing the
sampling frequency was evaluated based on a case-by-case review of well
information.
It should be noted, as stated in number four above, that the final recommended
monitoring frequencies that resulted from the combined analysis are not, in all cases, the
same as those recommended as a result of the qualitative evaluation. The justifications for
the final recommendations are provided in the "Rationale" column in Table 7.1, and fall
into the following general categories:
• Temporal and/or spatial statistical results confirm the sampling frequency
recommendations from the qualitative evaluation. For example, well BH-SF-E-
0315-U is recommended for exclusion from the network or for sampling frequency
reduction by both the temporal and spatial statistical results; thus, the statistics
7-6
-------
confirm the qualitative recommendation to exclude the well. Similarly, well BH-
SF-E-0306-L is recommended for exclusion or reduction by the temporal and
spatial statistical results; thus the statistics confirm the relatively low (annual)
sampling frequency recommended by the qualitative evaluation. Likewise, well
BH-SF-E-0410-U is recommended for retention based on the statistical
evaluations, which confirm the relatively higher (semiannual) sampling frequency
recommendation stemming from the qualitative evaluation.
• Decrease sampling frequency due to statistics results. For example, well BH-SF-
W-0005-U is recommended for semiannual sampling in the qualitative evaluation.
However, the well was recommended for exclusion or reduction in the temporal
evaluation because the cadmium and zinc levels are below their respective MCLs;
therefore, continued high frequency sampling would yield little additional
information. The temporal statistical evaluation results for multiple other wells
(e.g., BH-SF-E-0301-U, BH-SF-E-0305-U, and BH-SF-E-0425-U) would also
justify reduced sampling frequencies in typical LTMOs in which remediation is
complete or well-established. At OU2 however, the qualitative Phase II
remediation considerations overrode the statistics as described in Section 4.2.1.
As indicated by the temporal recommendation in Table 7.1, in these cases, a
reduction in the monitoring frequency may be appropriate once a Phase II
remediation plan is in place.
• Qualitative factor overrides statistics recommendations. For example, although
well BH-SCA-GW-0007 is recommended for exclusion or reduction based on the
limited value of its temporal trend information, the qualitative evaluation classified
this well as a downgradient sentry well for the SCA; thus, it is recommended for
semiannual monitoring. Additionally, although well BH-SF-E-0403-U is
recommended for retention by the temporal statistical analysis based on its
increasing cadmium concentrations, it is ultimately recommended for exclusion
from the monitoring program because the qualitative evaluation points out that it
exhibits the same trends and similar or lower COC concentrations than nearby well
BH-SF-E-0402-U.
Table 7.2 presents a summary of the revised groundwater monitoring network as
compared to the basecase network (number shown in parentheses) classified by HU. For
the OU2 groundwater monitoring wells, the LTMO results indicate that a refined
monitoring program consisting of 69 of the 77 original wells sampled less frequently
(two wells sampled biennially, 30 sampled annually, and 37 sampled semiannually) and
22 additional monitoring wells sampled semiannually would be adequate to address the
two primary objectives of monitoring listed in Section 1 and the OU2-specific objectives
listed in Section 3.1. This refined monitoring network would result in an average of 149
well-sampling events per year, compared to 308 per year under the current quarterly
monitoring program. A well sampling event is defined as a single sampling of a single
well. Implementing these recommendations for optimizing the LTM monitoring
program at OU2 would reduce the number of groundwater well-sampling events per
year by approximately 52% percent.
An approximate total cost per well-sampling event of $315 was derived based on
historic cost information provided by the USEPA. This cost includes field work,
7-7
-------
laboratory analytical, and data transfer; it was assumed that significant savings in overall
data management costs would not be realized. Using this cost, eliminating 159 well-
sampling events per year would result in an annual savings of approximately $50,000.
Because eight existing wells were recommended for exclusion from the monitoring
program, and 22 new wells were recommended for addition to the monitoring program,
the revised program consists of 91 total wells (compared to 77 in the original program).
Thus, all of the cost savings were derived from the recommended monitoring frequency
reductions from quarterly to semiannual, annual, or biennial.
TABLE 7.2
SUMMARY OF REVISED AND BASECASE MONITORING PROGRAMS
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
HU
Lower
SCA
Single
Unconfined
Upland
Upper
Total Wells
Monitoring Frequency
Exclude
1
7
8
Biennial
1
1
2
Annual
13
2
8
7
30
Semiannual
9
4
6
1
39
59
Quarterly
(13f
(5)
(5)
(10)
(44)
(77)
Total
Sampling
Points
22(13)
5(5)
8(5)
10(10)
46 (44)
91 (77)
Basecase sampling frequency corresponding to Table 3.1 shown in parentheses.
7.2 SURFACE WATER MONITORING NETWORK SUMMARY
The results of the qualitative and temporal evaluations for surface water monitoring
stations are summarized in Table 7.3, along with the final recommendations for sampling
station retention or exclusion and sampling frequency. A spatial statistical analysis of the
surface water stations was determined to be inappropriate and was not performed. The
results of the evaluations were combined and summarized in accordance with the
decision logic shown on Figure 7.2 and described for groundwater monitoring wells in
Section 7.1.
All 18 surface water monitoring stations evaluated were recommended for continued
sampling at a semiannual frequency as a result of the qualitative assessment. However,
as described in Section 4.3, it may be possible to either remove at least two monitoring
stations (BH-IG-0001 and BH-JC-0001) from the sampling program in the future, or to
reduce their sampling frequency, without introducing significant error into measurement
of the total metals load entering the SFCDR. This decision could potentially be made
following collection of two additional years of data.
In several cases, the temporal trend results were overridden by qualitative
considerations. In general, semiannual monitoring of surface water stations during high-
and low-flow conditions is recommended to support the Phase II remedial decisions, at
7-8
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TABLE 7.3
SUMMARY OF LONG-TERM MONITORING OPTIMIZATION EVALUATION OF SURFACE WATER MONITORING PROGRAM
LONG-TERM MONITORING OPTIMIZATION
BUNKER HILL MINING AND METALLURGICAL COMPLEX SUPERFUND SITE
Surface Water
Station Name
BH-BC-0001
BH-CS-0001
BH-DW-0001
BH-GC-0001
BH-GG-0001
BH-HC-0001
BH-IG-0001
BH-JC-0001
BH-MC-0001
BH-MC-0002
BH-MG-0001
BH-PG-0001
BH-RR-0001
BH-WP-0001
PC-339
SF-268
SF-270
SF-271
Current
Sampling
Frequency
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Annual
Annual
Quarterly
Quarterly
Quarterly
Quarterly
Quarterly
Qualitative Evaluation
Exclude
Retain
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Recommended
Monitoring
Frequency
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Semiannaual
Temporal Evaluation
Exclude/
Reduce
X
X
Retain
X
X
X
X
Not analyzed
Not analyzed
X
X
X
Not analyzed
Not analyzed
X
X
X
Not analyzed
X
Summary
Exclude
Retain
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Recommended
Monitoring
Frequency
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Rationale
Qualitative factor overrides temporal statistics; monitor semiannually to support Phase II remedial decision
making, then consider reduction to annual during high-flow conditions if most recent data indicate that similar
trends persist.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Qualitative factor overrides temporal statistics; monitor semiannually to support Phase II remedial decision
making, then consider reduction to annual during high-flow conditions if most recent data indicate that similar
trends persist.
Reevaluate for temporal trends once more data have been obtained.
Reevaluate for temporal trends once more data have been obtained.
Qualitative factor overrides temporal statistics; monitor semiannually to support Phase II remedial decision
making, then consider reduction to annual during high-flow conditions if most recent data indicate that similar
trends persist.
Temporal statistics confirm qualitative analysis.
Temporal statistics confirm qualitative analysis.
Reevaluate for temporal trends once more data have been obtained.
Reevaluate for temporal trends once more data have been obtained.
Qualitative factor overrides temporal statistics; monitor semiannually to support Phase II remedial decision
making, then consider reduction to annual during high-flow conditions if most recent data indicate that similar
trends persist.
Qualitative factor overrides temporal statistics; monitor semiannually to support Phase II remedial decision
making, then consider reduction to annual or biennial if continued low-magnitude and lack of trends .
Qualitative factor overrides temporal statistics; station indicates background levels.
Reevaluate for temporal trends once more data have been obtained.
Qualitative factor overrides temporal statistics due to station's downstream "sentry" location.
FINAL Bunker Hill Tables.xls
7-9
-------
least until these decisions are made. After that time, annual sampling of several stations
during high-flow conditions could be considered (e.g., BH-BC-0001, BH-HC-0001, BH-
WP-0001, and PC-339), assuming that the historical trends (decreasing and/or "no trend"
accompanied by a low coefficient of variation [COV]) shown in Table 5.2 persist and no
significant changes in upstream conditions (e.g., Phase II remedial actions) occur.
For OU2 surface water, the LTMO results indicate that a refined monitoring program
consisting of 18 stations sampled semiannually would be adequate to address the primary
objectives of monitoring listed in Section 3.1. This refined monitoring network would
result in an average of 36 surface water station-sampling events per year, compared to 66
per year under the current monitoring program (16 stations sampled quarterly and 2
sampled annually). Implementing these recommendations for optimizing the LTM
monitoring program at OU2 would reduce the number of surface water station-
sampling events per year by approximately 45% percent.
An approximate total cost for each sampling of a surface water station of $337 was
derived based on historic cost information provided by the USEPA. This cost includes
field work, laboratory analytical, and data transfer; it was assumed that significant
savings in overall data management costs would not be realized. Using this cost,
eliminating 30 surface water station-sampling events per year would result in an annual
savings of approximately $10,000.
7-10
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SECTION 8
REFERENCES
American Society of Civil Engineers (ASCE) Task Committee on Geostatistical
Techniques in Hydrology. 1990a. Review of Geostatistics in Geohydrology - I.
Basic concepts. Journal of Hydraulic Engineering 116(5):612-632.
ASCE Task Committee on Geostatistical Techniques in Hydrology. 1990b. Review of
Geostatistics in Geohydrology - II. Applications. Journal of Hydraulic
Engineering 116(6): 63 3 -65 8.
CH2M Hill. 2004. Bunker Hill Superfund Site, Kellogg, Idaho: Single Well Pumping
Test Methods and Results. Technical Memorandum. January 26.
CH2M Hill. 2005a. Current Status Conceptual Site Model, Operable Unit 2, Bunker Hill
Mining and Metallurgical Complex Superfund Site. External Review Draft. June.
CH2M Hill. 2005b. Environmental Monitoring Plan, Operable Unit 2, Bunker Hill
Mining and Metallurgical Complex Superfund Site. External Review Draft. June.
Clark, I. 1987. Practical Geostatistics. Elsevier Applied Science, Inc., London.
Environmental Systems Research Institute, Inc. 2001. ArcGIS Geostatistical Analyst
Extension to ArcGIS 8 Software. Redlands, CA.
Gibbons, R.D. 1994. Statistical Methods for Groundwater Monitoring. John Wiley &
Sons, Inc., New York, NY.
Rock, N.M.S. 1988. Numerical Geology. Springer-Verlag, New York, NY.
U.S. Environmental Protection Agency (USEPA). 1994. Methods for Monitoring Pump-
and-Treat Performance. Office of Research and Development. EPA/600/R-
94/123.
U.S. Environmental Protection Agency. 2005. Roadmap to Long-Term Monitoring
Optimization. Office of Superfund Remediation and Technology Innovation.
EPA/542/R-05/003.
Wiedemeier, T.H., and P.E. Haas. 2000. Designing Monitoring Programs to Effectively
Evaluate the Performance of Natural Attenuation. Air Force Center for
Environmental Excellence (AFCEE). August.
8-1
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APPENDIX A
SELECTED FIGURES FROM THE DRAFT CONCEPTUAL SITE
MODEL REPORT (CH2M HILL, 2005A)
-------
APPENDIX B
COMMENTS AND RESPONSES ON THE DRAFT REPORT
-------
Note: All comment responses prepared by Parsons and submitted to project team on 12/2/05
CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
General Comment:
This is a well-written and thought out document that follows a logical pathway to evaluate long-term groundwater monitoring network. The applicability to the
evaluation of surface water monitoring networks is not as clear and does not fit well with the methods used. This may be an area for further exploration by the
Long-Term Monitoring Optimization group.
Response: Agree. The LTMO tools applied for OU2 are best suited to groundwater monitoring networks. As a result, the qualitative evaluation of the surface
water monitoring network carried the most weight for this site.
Specific Comments:
Item
No.
1.
2.
o
J.
4.
5.
6.
Section/Page
Title
Figure 2.1
Page 2-1
Page 2-6
Page 3-8
Table 3. 3
Line(s)
20
14-15
18
Comment
It would alleviate a potential source of confusion to add Operable
Unit 2 to the title.
The confining unit box shown in this figure and others within the
report should be identified as the approximate eastern extent of the
confining unit.
Large-scale mining operations within OU2 ceased in 1991. Small-
scale operations are still operating at the Bunker Hill Mine and
several other mines are still in operation upstream of OU2.
It should be noted that the upper portion of the SFCDR valley
alluvium is one large source area which prevents the delineation of
plumes. Numerous source areas imply that all of the sources of
contamination within OU2 can be delineated and defined.
"for this plume" is not an accurate depiction of conditions within
OU2. Suggest "for OU2 groundwater and surface water"
Need a footnote to indicate that the zinc MCL is a secondary
MCL.
Response
Done.
Done.
The sentence will be revised to incorporate the
information presented in the comment.
The sentence will be revised to read: "The upper
portion of the SFCDR valley essentially constitutes one
large source area, preventing delineation of discrete
contaminant plumes in OU2 groundwater."
Revised to reflect suggested text.
Done.
Draft Long Term Monitoring Plan Comments - Final.doc
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CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
7.
8.
9.
10.
Section/Page
Table 3. 4
Table 3. 5
Page 3-9
Table 4.3
Line(s)
Comment
Need to indicate that the AWQC shown in Table 3.4 are hardness
dependant. It appears that the AWQC shown are those from the
Statistical Analysis Report which assumed a hardness of 100
mg/L.
Five of the groundwater monitoring well results shown on the
table are for different time periods (other than October 2004). This
should be called out and noted. This comment also applies to
Table 3.6 and figures generated using this data.
Groundwater monitoring wells classified by MCL exceedence
ratio. This is interesting to see, and appropriate as a summary of
the data and the level of decision seems appropriate. However,
there appears to be limited value in this approach which may
confuse the reader regarding the statistical significance of the
information. Also, some statistical information regarding the ratio
should be included such as how often the MCL is exceeded at the
ratio given. Is this a measurement weighted average or is it based
on a single result or sampling event which may or may not be
indicative of contaminant concentrations over time at a specific
location?
The rationale given for the BH-SCA series wells should be
"seepage" versus "leakage"
Response
Done.
Tables 3.5 and 3.6 and figures modified to note
different time periods.
The MCL exceedance ratio data is for the most recent
concentration only, and, as suggested in the comment,
intended as a higher level summary of the data. The
text is updated to emphasize the "most recent" one data
point approach, and the figures are updated to clarify
date of sampling, per comment #8.
Wording changed in table.
Draft Long Term Monitoring Plan Comments - Final.doc
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CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/Page
Line(s)
Comment
Response
11.
Page 4-10
5&6, First
Bullet
This bullet states that quarterly monitoring performed to date is
sufficient to indicate seasonal changes in COC concentrations. It
needs to be stated that the term seasonality as used in this bullet is
not the same as seasonality as used statistically for statistical
corrections using the Mann-Kendall test for trend. This has been a
point of contention recently regarding the statistical analysis of
water quality data using the Mann-Kendall test for trend within the
group. In general, the current data set is not sufficient to determine
or provide a seasonal statistical correction to the evaluation and
this statement about seasonality may add to this confusion. While
there appears to be seasonal changes (not statistical seasonality) in
the data set in response to snowmelt or precipitation events, I do
not see that these changes occur on a predictable and consistent
time interval that would be required to provide a statistical
correction for Mann-Kendall analysis. It would appear that the
authors reached the same conclusion as a seasonal correction is
not discussed in this report. Some clarification may need to be
provided in this report that states whether the data set was
sufficient to indicate the presence or lack of statistical seasonality.
The first bullet will be revised to read: "The quarterly
monitoring performed to date is sufficient to
qualitatively indicate seasonal changes in COC
concentrations (however, the historical data are not
necessarily adequate to determine seasonality in a
statistical sense in order to perform statistical
corrections for seasonality using the Mann-Kendall
test for trend)."
12.
Page 4-10
13-16,
Third Bullet
Here the statement that quarterly monitoring performed support
the observation that.... This language suggests that the first bullet
is indicating that a statistical seasonality is present. If this is the
case, the first bullet should be refined to indicate that statistical
seasonality is present in the data set and the authors should
consider adjusting the data and performing the analysis on the
adjusted data set. Again, we did not see statistical seasonality in
the data set and would be interested in reviewing this with the
authors if they did detect this.
The intent of the third bullet is not to suggest that
statistical seasonality is present. The correction made
to the first bullet (see response to comment #11) should
make this sufficiently clear.
Draft Long Term Monitoring Plan Comments - Final.doc
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CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/Page
Line(s)
Comment
Response
13.
Page 4-11
1-2 and 21-
25
While we agree with the recommendation to reduce monitoring
frequency further following a two-year period of semi-annual
monitoring, the authors recommendation for when annual
monitoring should be included. We believe that annual
groundwater monitoring in conjunction with low-flow surface
water condition is appropriate given the need to evaluate
conditions when groundwater is having a greater potential impact
on surface water quality.
The referenced text recommends an approximately 2 to
3 year semiannual monitoring period followed by
annual monitoring. A more definite time frame for
implementing annual monitoring was not included
because we did not know the time frame for finalizing
Phase II remedial decisions. The text in lines 22-23
states that once the need to collect more frequent data
to support Phase II remedial decisions is past the
monitoring frequency could be reduced. It would be
difficult for us to be more specific at this time.
14.
Page 4-12
1-11
Monitoring wells collocated with other wells on the northern edge
of the CIA may appear to be redundant. However, given public
interest in the CIA and belief by some that the CIA is a water and
contamination source in this area may require the need to retain
the two monitoring wells called out in the first two bullets as part
of Phase I remedial action effectiveness monitoring. The
monitoring wells in questions are screened slightly above/below
each other and provide some information on water quality
stratification in this area that can be used to indicate the
significance of the CIA as a water/contaminant source in this area.
In addition, they also provide some information with regard to
water quality for water lost from the SFCDR as it infiltrates
through the upper aquifer and groundwater quality as it
approaches and eventually discharges to the SFCDR.
The two wells recommended in the comment for
retention (BH-SF-E-0315-U and BH-SF-E-0403-U)
exhibit similar temporal trends as the paired shallower
well, but often exhibit lower concentrations.
Comparison of water quality results for zinc and
cadmium for these two well pairs indicates that the
deeper wells consistently have concentrations that are
lower than or similar to the shallower wells. It seems
as though the stated goal of indicating the significance
of the CIA as a water/contaminant source would be
best served by monitoring wells located along the
downgradient edge of the CIA and monitoring the
reach of the SFCDR that is adjacent to and
immediately downstream of the CIA, rather than these
two wells that are in the interior of the CIA. The goal
of assessing the impact of groundwater quality on the
SFCDR is best served by monitoring surface water
quality in gaining reaches of the SFCDR rather than
individual, isolated wells. Continuing to monitor these
two wells to assess the impact of surface water
discharge on groundwater quality is of questionable
utility (especially when the two shallower paired wells
will continue to be monitored). In summary, Parsons
questions whether sufficient useful and important data
are gathered from these two wells to justify their
Draft Long Term Monitoring Plan Comments - Final.doc
-4-
-------
CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/Page
Line(s)
Comment
Response
retention. If they are retained, then a lower sampling
frequency may be appropriate (e.g., annual for 2-3
years then transitioning to biennial). Our intention is to
continue to recommend that these wells be deleted
from the LTM program purely on technical grounds.
However, the USEPA/State/CH2M Hill are free to
continue to monitor these wells if they disagree with
this recommendation.
15.
Page 4-12
Last Bullet
on page
BH-SF-E-0311-U is one of the few monitoring wells located on
the north side of the SFCDR. While water quality information
from this monitoring well may indicate relatively little
contamination in this area, we believe that information from this
monitoring well is critical for evaluation of contaminant flux
across Transect 2 (as recommended on page 4-4) and also in
evaluation of the relationship between north of SFCDR
groundwater and the SFCDR (head difference and water quality).
The qualitative evaluation will be revised to
recommend retention of this well at a reduced (annual)
sampling frequency to support the objectives outlined
in the comment. Sampling this well at a reduced
frequency is justified given that the well represents a
relatively small portion of Transect 2 and has metal
concentrations (Cd and Zn) that are 1 to 2 orders of
magnitude lower than detected further south along this
transect (wells 0309-U and 0305-U). Therefore, mass
flux calculations will be dominated by the larger
concentrations detected south of the SFCDR. The
report will state that additional reduction of the
sampling frequency of 0311-U to biennial further into
the future should be considered.
Draft Long Term Monitoring Plan Comments - Final.doc
-5-
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CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
16.
17.
18.
Section/Page
Page 4-13
Table 4.4
Page 5-2
Line(s)
14-19
10-11
Comment
We agree with the statements regarding water quality in well BH-
SF-W-0018-U and the potential influence of the SFCDR on this
monitoring location. Given the proximity of this monitoring well
with the SFCDR in a losing reach, this monitoring well provides
information regarding the impact of potential contaminant sources
near this well on relatively clean SFCDR water that is lost to the
aquifer in this area. This monitoring well plays a key role in the
evaluation of the SFCDR/upper aquifer groundwater relationship.
BH-MC-0001 - The old Milo Creek outfall is not connected to the
new outfall and represents water that is infiltrating and finding its
way to the old piping system. We feel that this location should be
retained in order to complete surface water mass balances.
See comment above regarding seasonal correction.
Response
Comparison of dissolved cadmium and zinc
concentrations in well 0018-U with dissolved
concentrations of these metals detected in the SFCDR
at station SF-270 in April 2004 indicates that they are
similar. The dissolved lead concentration at SF270
was higher than typically detected in groundwater at
0018-U. Therefore, it is not clear from these data that
the SFCDR water is significantly more clean than the
groundwater at well 0018-U. Is it necessary to
continually assess the impact of potential contaminant
sources near this well on SFCDR water that is lost to
the aquifer in this area when the impact results in
groundwater COC concentrations that do not exceed
cleanup goals (based on results from 20 sampling
events performed over 4.5 years)? Our intention is to
continue to recommend that this well be deleted from
the LTM program purely on technical grounds.
However, the USEPA/State/CH2M Hill are free to
continue to monitor this well if they disagree with this
recommendation. If so, a relatively low monitoring
frequency should be considered.
The report will be revised to retain the old Milo Creek
outfall for the reason stated in the comment.
Text revised to clarify that MK seasonal correction was
not conducted or appropriate for this analysis.
Draft Long Term Monitoring Plan Comments - Final.doc
-------
CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/Page
Line(s)
Comment
Response
19.
Section 5
We compared the CH2M HILL statistical analysis with that in
Section 5. While both evaluations use the Mann-Kendall test for
trend, there were differences in the confidences and assumptions
underlying the trend test. The LTMO test uses a 90% confidence
level and uses data with 4 or more detections in the data set, while
the CH2M HILL analysis used a 95% confidence level and was
limited to 11 or more samples with greater that 50% detected
concentrations at a given location. A comparison of the trends
between the two studies indicates that the LTMO study results in
far more trends than the CH2M HILL analysis. Given that both
documents are now out there, the rationale for selection of
confidence level (90%) and the number of samples required (4 or
more) should probably be discussed. Using a lower confidence
level and a less restrictive data population could result in increased
incidence of false trends in addition to additional trends due to
more wells meeting the criteria for determining a trend. We
observed this in the CH2M HILL statistical analysis when the full
period of record data set for each location was evaluated with the
same confidence interval but no qualifications for number of
samples and detected concentrations. Some discussion comparing
methods and results would be helpful since both used the same
trend determination methodology (Mann-Kendall).
Table 5.1 and Section 5 text were modified to clarify
the MK trend parameters and results to allow for more
transparent comparison to the CH2M Hill Analysis.
Specifically, the following were added: 1) a column
showing the number of sampling results; 2) trends
changed to "probably" increasing/decreasing in those
cases where the confidence level was between 90 and
95%; 3) identification of those trends in which >50%
of the sampling results were ND.
Using a 90% confidence interval allows for the
identification of more "potential" trends, and is more
conservative (e.g., identifying the probably increasing
trends in BH-SF-E-0402-U). Using 4 or more results is
consistent with other LTMO analyses (i.e. MAROS)
and guidance (see [added] USEPA/USACE LTMO
Roadmap reference and response to Lorraine Edmond
comment #10); the majority of wells had >6 results.
Trend recommendations for those wells with fewer
than 6 results were revised to "no recommendation".
Text was added to highlight that trends based on less
sampling data and/or with >50% ND should be given
less relative weight in decision making.
Note that no revisions to the trends affected the final
well retention/frequency recommendations.
20.
Section 6
The evaluation of the spatial distribution of the monitoring
locations within the site (without taking into account the spatial
boundary conditions of the site) could be confused with a
statistical evaluation of COC distribution. Given the conditions at
the site (highly heterogeneous with widespread sampling
locations) the significance of this section with respect to the
evaluation should be reduced reflecting the applicability of the
results on the final selection criteria for wells to retain or be
Text added to clarify that the statistical evaluation
(specifically Figure 6.2) was based on the standard
error and not the COC distribution. Agree that the
heterogeneous conditions make statistical evaluation
difficult. Text added to discuss this and to clarify that
the statistical evaluation results were not given as high
of a weighting in the combined evaluation as a result.
Draft Long Term Monitoring Plan Comments - Final.doc
-7-
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CH2M HILL Comments on the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill
Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
21.
Section/Page
Section 7
Line(s)
Comment
excluded from the program.
Cost savings. It would be helpful to understand how much of the
reduction in cost is associated with the exclusion of monitoring
locations and how much of the reduction is associated with the
reduction in frequency. This would be a very helpful tool to assist
in making further adaptive management changes to the long-term
monitoring program.
Response
Text was added to Section 7 to describe the specific
cost savings due to monitoring exclusion and
reduction.
Draft Long Term Monitoring Plan Comments - Final.doc
-------
HTRW Center of Expertise - Review Comments on the Draft Long-Term Monitoring Network Optimization
Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
General Comment.
An excellent job on a complex project. I agree with the overall recommendations, but defer to the project team for Bunker Hill for a detailed
assessment of the recommendations in light of their site conceptual model.
Item
No.
1.
2.
3.
4.
5.
6.
7.
Page
Page 2-5
Page 3-12
Page 3-19
Page 4-3
Page 5-2
Page 5-5
Page 6-5
Section
Sec. 2.2.2
Figure 3.3
Figure 3.7
and
subsequent
figures
Table 4.2
sec. 5.1
sec. 5.2
Table 6.1
Comment
Please indicate if groundwater is used for any purpose within the
study area.
Please use different symbols in addition to colors in case people
only have a black-and-white copy.
Some of the posted values are the same for several sampling
points. Please verify the values. Are these detection limits?
I would like to see one modification to the decision logic used in
the qualitative assessment (and in the overall assessment logic).
The sampling frequency should probably increase if there has been
a recent significant upward trend in the data toward or exceeding a
standard at locations suggesting plume expansion.
Please revise second to last sentence to read "The Mann-Kendall
test statistic can be evaluated to determine, at a specified level of
confidence, whether a statistically significant temporal trend. .."
May want to separately identify upgradient wells, too.
a) The minor ranges identified here are significantly larger than
the spacing along the transects after the addition of the added
wells recommended in the qualitative analysis. I agree with the
addition of wells, but I would suggest adding a few sentences
cautioning using these ranges as a basis for well spacing in a
heterogeneous site such as this. I suspect the anisotropic ranges
are poorly constrained, b) For the Upper HU Cd column, verify
the sill and nugget values. The sill should not be lower than the
nugget, though I am not very familiar with the circular model.
Response
Text will be added to state that groundwater is not used
for any purpose within the study area.
Symbols modified in maps to allow for differentiation
in black and white.
The figures were revised to display non-detects as
"ND" and to post the correct COC data (corresponding
to Table 3. 6).
This modification will be made.
Text revised.
Upgradient description added to text.
a) Text was added to clarify that the minor range used
for the variogram model should not be considered for
well spacing along the transects.
b) The nugget and sill values were transposed and
corrected.
Draft Long Term Monitoring Plan Comments - Final.doc
-9-
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HTRW Center of Expertise - Review Comments on the Draft Long-Term Monitoring Network Optimization
Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
8.
9.
10.
11.
12.
13.
Page
Page 6-6
Page 6-9
Page 6-12
Page 7-2
Page 7-6
Page 7-10
Section
sec. 6.2
Table 6.2
Table 6.5
Table 7.1
Figure 7.2
sec. 7.1
Comment
I would like some additional discussion of the impact of the use of
ranks in the geostatistical analysis on the sensitivity of the analysis
to the edges of the plumes relative to the high concentrations. Are
the higher numbers for the ranks assigned to the lower
concentrations?
This table has erroneous page numbers - they should have the
prefix of 6-, not 5-.
Please add a footnote to the table explaining the Z, C, and ZC
entries. I know its explained in the text, but it should be explained
in the footnote, too.
Please show the recommended additional wells in this table.
Again, please indicate the potential to increase sampling frequency
for increasing trends in downgradient wells if the current
frequency is not adequate.
Would it not be appropriate to sample the new wells at least semi-
annually for a couple of years?
Response
Text was added to clarify that the wells are ranked
from lowest concentration (1) to highest concentration
(# of wells inset).
Page numbers corrected.
Footnote added to table.
New wells added to summary table.
Increase frequency option added to flow chart.
Agree, the lower aquifer wells recommended for
annual sampling will be recommended for two years of
semiannual sampling to establish a better baseline of
data followed by annual sampling unless the
semiannual sampling results indicate a need for
continuing with a higher frequency.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 - Office of Environmental Assessment Review Comments on
the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill Mining and Metallurgical
Complex Superfund Site
General Comments. Lorraine Edmond
Item
No.
1.
2.
3.
4.
5.
6.
Comment
I found the report to be clear, well-organized, and efficient at making use of the abundant site data
and the existing Conceptual Site Model. The recommendations for the frequency of sampling
make sense, and are tied to the decision-making process, with further modifications that can be
made after decisions on Phase II remediation are made. The clear decision logic and
recommendations for specific analyses for future decisions makes the LTMO analysis useful both
now and in the future.
It is hard to say how easily this project will work as a national example, since the site is atypical
in so many ways, but the report does a good job of evaluating potential efficiencies in monitoring
for Bunker Hill OU2. Some of my comments below reflect the fact that this report will be used
as an example for the LTMO process in general.
The optimization principles and the decision logic are clearly explained and are consistently tied
to the project monitoring objectives. These aspects of the report would be applicable to any
project.
Addition of monitoring wells
I agree that wells should be added to increase density in the transects. The transects are the only
places we have that even approach having a reasonable density of wells relative to the rest of the
site. Even though considerable uncertainty regarding the absolute value of the metals flux though
the transects will remain, I agree that they will continue to be useful for evaluating temporal
changes and relative down-valley changes in flux, and additional wells will aid in that evaluation.
I also agree with the State's comment that additional wells in the Smelterville Flats area are
important. It is a large area with a very low density of wells, and a significant amount of remedial
effort was expended there. Evaluation of the current groundwater conditions and of the
effectiveness of the remedial actions could be significantly aided by the addition of monitoring
wells.
Reduction in monitoring wells
With regard to specific recommendations to retain certain wells, I defer to the comments by
CH2MHill and the State of Idaho, who have much more well-specific knowledge. I agree that the
wells evaluating the CIA are important, even though they may appear to be spatially redundant.
Response
Noted.
Noted.
Noted.
Noted
Additional wells will be recommended for installation
per the response to TerraGraphics comment #29.
Noted
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 - Office of Environmental Assessment Review Comments on
the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill Mining and Metallurgical
Complex Superfund Site
(Continued)
Item
No.
Comment
Response
Reduction in monitoring frequency
7.
The proposed reductions in monitoring frequency make sense given the amount of data that we
have for OU2 already and the rate of change in groundwater quality we are likely to see. I would
be much more cautious about decreasing monitoring frequency based on only 4 rounds of
sampling, however, which is the threshold the LTMO uses for determining trends. At most sites,
this would mean making long-term monitoring decisions based on only the first year's worth of
data, which might or might not be representative of a longer time period.
Wells with fewer than 6 results were excluded from the
temporal analysis to include the conservative number
of sampling points recommended in the
USEPA/USACE "Roadmap to LTMO" guidance. In
addition, text was added to
highlight that trends based on less sampling data
should be given less relative weight in decision
making.
Trend Analysis
The comparison with CH2MHill trend results is worth discussing, since they use almost the same
dataset and both will be publicly available. Differences in the number of samples required for
testing and in the confidence interval used to determine significance inevitably results in different
conclusions regarding trends.
Agreed. Please see response to similar CH2M Hill
comment #19 on page 6.
9.
While the threshold used by CH2MHill of 11 samples required before testing for trends is a high
one, it is probably appropriate for the OU2 dataset. Other sites may not have this abundance of
data, however. The selection of the 90th % confidence interval should also be discussed, as this is
also a relatively low threshold for determining that a trend exists. How different would the final
conclusions be if a 95% confidence interval had been used?
See response to comment #7 re the number of sampling
points relevant for trends.
"Probably" increasing/decreasing trend classifications
were added to differentiate between the 90% and 95%
confidence levels. Using a lower confidence level
allows for the earlier identification of trends, and is
thus more conservative.
10.
As a general recommendation for other sites, waiting to have 11 sample rounds before analyzing
trends may not be realistic. However, as mentioned above, the threshold of 4 data points seems
too low. What might prove useful is to show the results of the two analyses side-by-side, along
with some discussion of whether or not the resulting recommendations would differ had the
LTMO used a higher threshold of sample numbers and of statistical confidence. Showing at least
some of the trends graphically would be helpful to the reader.
Agreed that the more information, the better; however,
useful information can be determined from fewer than
11 rounds of sampling data (4-6 sampling points is the
minimum recommended in USEPA/USACE
"Roadmap to LTMO" guidance) and was thus included
in this analysis. A column with the number of
sampling results used in the analysis was added to
Table 5.1 to make the data more transparent.
An example graphical trend is shown in Figure 5.1;
however, statistical trends are used precisely because it
is difficult to quantitatively judge trends based on
graphical interpretation.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 - Office of Environmental Assessment Review Comments on
the Draft Long-Term Monitoring Network Optimization Evaluation for Bunker Hill Mining and Metallurgical
Complex Superfund Site
(Continued)
Item
No.
Comment
Response
11.
On the other hand, it may be that the low threshold for trend detection is actually environmentally
conservative in the context of an LTMO, if I understand the report correctly. Section 5.1 explains
that the "no trend" conclusion results in a recommendation to reduce sampling, since it indicates
that no additional information will be obtained by frequent sampling. Detection of a trend, on the
other hand may require more frequent monitoring, depending upon the location of the monitoring
point. In a sensitive location, then, detection of a trend would mean that additional data would be
collected and uncertainty reduced. It would help if the report could discuss the pros and cons of
the different approaches to setting the thresholds for trend determination.
Agreed that identifying trends can potentially be more
conservative (e.g., increasing or decreasing trends in a
source area, as almost all Bunker Hill wells are
classified) results in a "retain" recommendation.
Text was added to clarify the temporal trend
parameters, and a reference was provided
(USEPA/USACE's Roadmap to LTMO) that discusses
different LTMO approaches and considerations.
12.
However, according to p 5-13, a downgradient well with a decreasing trend might be excluded or
have sampling frequency reduced. It seems we would want to reduce uncertainty in these cases
as well, depending upon the number and location of such wells. This may simply be an example
be where the qualitative analysis comes back in and outweighs the statistical evaluation,
particularly if a decision point regarding compliance were approaching, for example.
Agree that the qualitative and/or spatial evaluations
would provide additional lines of evidence to reduce
uncertainty. Text was highlighted to emphasize that
the temporal evaluation related ONLY to the value of
temporal data, and that final recommendations are
based on a combination of all three evaluations.
13.
Similarly, it would be worth distinguishing between being willing to run a test with 4 samples,
and actually recommending beginning the LTMO process with only one year's worth of quarterly
samples. I think the report is doing the first, and not the second, but some discussion would be
helpful, especially with regard to my earlier comment about the report being used as an example.
Text added to clarify the decision to include >6
sampling points per USEPA/USACE Roadmap to
LTMO guidance.
Specific Comments
Item
No.
1.
2.
Table/Figure
Table 3 -5 and the
associated figures
Figure 5.4
Comment
use "most recent" data to describe current conditions, which is logical.
Although most of the most recent sample data were from October 2004, for
some locations, data from winter, spring, or summer samples are used. It
might be worth acknowledging that, taking a look at those locations, and
determining whether using only fall data, for example, would make any
difference. (With this dataset it might not, but I can imagine other cases
where the seasonality makes the difference between exceeding a standard
and not exceeding it.)
What is the criterion for the box labeled "high variation"?
Response
Discussion added to the text to describe selection of
"most recent" data and appropriateness of including
wells with different sampling dates.
High variation = coefficient of variation > 1 (consistent
with MAROS). Footnote added to table and
explanation added to text.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 Review Comments on the Draft Long-Term Monitoring
Network Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
General Comments.
Anne Dailey
Item
No.
Comment
Response
1.
The graphics should be readily copied in black and white. Most of document is already copiable
in black/white - but a few figures need some symbol adjustments (e.g., Fig. 3.3 and 3.4).
Figures adjusted to display symbology in black and
white.
Several of the Bunker Hill OU2 documents cited are draft documents (e.g., the OU2
Environmental Monitoring Plan, updated Conceptual Site Model, and Statistical Trend Analysis).
The documents are all still under revision but will be finalized in early 2006 - in part pending
integration of the result of the LTMO study. It would be good to be clear about this in the text
and in the references in Section 8 should note that these are draft documents.
Text will be revised accordingly.
Several other commenters noted the 90th%ile confidence interval that the LTMO review uses
versus the 95th%ile confidence interval used by CH2M Hill in their analysis of the data for EPA
Region 10. Given the high degree of scrutiny that this site continues to get (National Academy of
Sciences final report on the site due to be release in late December, litigation, high degree of
community interest), the report should expand on the selection of 90th%ile vs. 95th%ile
confidence interval. How different would the results be? Could you run some of the calculations
using the 95%ile confidence interval? If appropriate, perhaps we should schedule a conference
call to discuss.
"Probably Increasing" and "Probably Decreasing"
trends added to differentiate between 90% and 95%
confidence trend results. A 90% confidence interval
allows a great amount of trends to be identified.
Ultimately, the 90% vs. 95% confidence limits did not
affect the LTMO summary recommendations.
Specific Comments
Item
No.
Section/P
age
Line/para
Comment
Response
1.
Sect. 2.1
Especially for readers unfamiliar with the site, it would be helpful to
provide a bit of additional context regarding OU2 in the overall Bunker
Hill Mining and Metallurgical Complex Superfund Site. (If you
would like, I'd be happy to provide a paragraph or two). This is
important in part because there is an extensive environmental
monitoring program already in place for Operable Unit 3 (Coeur
d'Alene Basin) which is intended to dove-tail with the OU2 BMP. As
noted below, several of the surface water stations are sampled
routinely as part of the Basin Environmental Monitoring Plan (BEMP)
but the results are also used in the OU2 BMP. The following surface
water monitoring stations are funded and sampled as part of the
BEMP:
The Section 2.1 text will be revised as requested. We
will also add information about the dovetailing of the
OUs 2 and 3 monitoring programs to Sections 2.1 and
4.3. Please either provide some recommended text to
add or direct us to text in existing documents that we
should use.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 Review Comments on the Draft Long-Term Monitoring
Network Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/P
age
Line/para
2.
3.
4.
5.
6.
Sect. 2.2
Sect. 2.3
Sect. 3.2
p. 4-17
Table 7-1
1st line
2nd full
para
Comment
PC-3 3 9 - Pine Creek below Amy Gulch
SF-268 - SFCDR at Elizabeth Park
SF-270 - SFCDR at Smelterville
SF-27 1 - SFCDR at Pinehurst
It should also be noted that consideration of OU2 surface water data
needs was considered when we developed the OU3 BEMP.
Given that readers unfamiliar with the Bunker Hill Superfund Site will
be looking at this report, it might be helpful to include several of the
CSM figures cited in this section (e.g., Fig. 3-8 of the CSM).
For readers unfamiliar with the site, it may be helpful to provide a bit
more background on the cleanup actions taken to date and potential
future Phase II cleanup actions. Please advise if you would think this
would be a good addition and would like assistance on preparing such
text.
"plume" is probably an inadequate description for the extent of the
groundwater contamination at this site. As you know this site does not
a have a classical plume with a point source ... .at Bunker Hill the
groundwater contamination is extensive and widespread throughout the
upper aquifer.
As noted above in the comment on Sect. 2.1,4 surface water stations
from the OU3 BEMP contribute information to the OU2 monitoring
program.
It would be very helpful to include the recommended additional wells
in this table.
Response
We will add information about this issue to Sections
3. land 4.3
The CSM figures referenced in Section 2.2 will be
added as Appendix A. We will need to solicit clean
copies of some of these figures from CH2M Hill
because our copies of some of them are marked up.
The LTMO report is not meant to be stand-alone, but is
an addition to previously -prepared site reports. It is
assumed that readers using the LTMO report would
also have access to documents such as the CSM. The
discussion of cleanup actions performed to date
contained in the CSM report encompasses 15 pages. If
a summary of these topics is desired, Parsons would
appreciate assistance on preparing this text, especially
given that we are not familiar with the scope of
potential Phase II cleanup actions.
The words "this plume" will be replaced by "OU2".
See response to specific comment #1.
New wells added to summary table.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 Review Comments on the Draft Long-Term Monitoring
Network Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
7.
8.
9.
Section/P
age
Sect. 7
p. 2-5
Line/para
mid 1st
para
Comment
EPA RIO's main objective in updating the OU2 monitoring program
and engaging in the LTMO process is to ensure that we are collecting
the right data on which to base decisions about potential Phase II
remedial actions (likely costing 10s of millions of dollars). In addition,
we need to ensure that we will be able to evaluate the effectiveness of
those remedial actions. While we are aiming to make the program as
efficient and effective as possible, the data integrity question is the
primary reason for the Region to conduct the LTMO analysis. Cost
savings on the monitoring program is an important but definitely a
secondary objective. I believe that the report emphasizes the first
objective (data integrity) but with the closing paragraphs of the report
focusing on cost savings, I wonder there isn't undue emphasis on the
cost saving aspect?
- It would also be helpful to break out the cost savings due to reduction
in frequency and elimination of sampling locations.
0.54 ft/ft should be ft/day
Response
The cost-related text is about as minimal as it can be,
and comprises only a very tiny fraction of the report.
However, we are open to specific suggestions as to
how to further minimize the emphasis on this topic.
Retaining some cost discussion seems appropriate
given that it is a secondary objective.
Text was added to Section 7 to describe the specific
cost savings due to monitoring exclusion and
reduction.
ft/ft is correct given that it is referring to a hydraulic
gradient.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 Review Comments on the Draft Long-Term Monitoring
Network Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
General Comments. Bernie Zavala
Item
No.
Comment
I have reviewed the above-mentioned document and would like to offer the following comments
from a general perspective or from an overall approach to optimizing the long-term monitoring
networks. I found the document to be logical and a good mix of qualitative and quantitative
assessments tools which were used to make insightful recommendations on the monitoring
network at Bunker Hill Superfund OU 2. 1 didn't provide specific comments to the monitoring
locations because I lack intimate working knowledge of the site. I did provide specific comments
on the approach.
Overall, the evaluation was good and will be useful for the cleanup. Once the comments have
been addressed, the document should be finalized and recommendations implemented.
Response
Noted.
Noted.
Specific Comments
Item
No.
Section
Page
Line/Para
Comment
Response
1.
Section 1.0,
Introduction
Page 1-2
second
sentence,
line (3)
Minor comment, but important, this evaluation
(LTMO) is to determine the overall
effectiveness of the monitoring program and
then will optimize the existing program which
may include additional monitoring locations or
opportunities to streamline the monitoring
activities. Please include language in the
introduction to emphasis that the LTMO process
evaluates the overall effectiveness of the
monitoring program first.
The text starting on page 1-2, line 3 will be revised to
read: "A monitoring network consisting of 77
grounchvater monitoring wells and 18 surface water
stations was evaluated to assess its overall
effectiveness at achieving the O U2- specific monitoring
objectives, and to (1) identify potential opportunities to
streamline monitoring activities while still maintaining
an effective monitoring program, and (2) identify data
gaps that may require addition of additional
monitoring points."
2.
Section 2.2.1
Geology
Page 2-3
first
paragraph,
line (15)
It would be useful to include the geologic cross-
section to aid the reviewer of this report but it is
also understood that information was referenced
in the CSM report ( CH2M Hill, 2005a). It is
suggested that a generalized cross-section could
be produced similar to the verbal description
that was included in the last two paragraphs in
section 2.2.1.
See response to Anne Dailey's specific comment #2
above.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 Review Comments on the Draft Long-Term Monitoring
Network Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section
Page
Line/Para
Comment
Response
See response to Anne Dailey's specific comment #3
above.
An additional section is needed in Section 2
Site Background Information. It should be
Section 2.4 Summary of Remedial Action.
What was the history of the remedial actions
within the "Box?" Section 3.0 listed that one of
the objectives of the groundwater monitoring
program for OU 2 was to evaluate the
cumulative effects of the remedial action in
Phase 1. Please include that summary in Section
2.4.
Section 3
Long-Term
Monitoring
Program
Page 3-1
lines (4-7)
Similar to the above comment #1, the
monitoring network optimization (MNO) first
must determine the effectiveness of the network
in terms of the monitoring objectives then make
the appropriate optimization changes whether its
streamline or additions/increases to the
monitoring program.
The referenced text will be revised to read: "The
existing groundwater and surface water monitoring
program at OU2 was examined to assess its overall
effectiveness at achieving the O U2- specific monitoring
objectives, and to (1) identify potential opportunities to
streamline monitoring activities while still maintaining
an effective monitoring program, and (2) identify data
gaps that may require addition of additional
monitoring points."
Section 3.1
Description of
Monitoring
Program
Page 3-8
line (1)
Not sure how this monitoring program will
address the second objective, evaluate the
nature ofgroundwater/surface water interaction
and the impact of groundwater discharge on
surface water quality. This comment can't be
addressed by the LTMO process but this
comment should be addressed by the site team.
There is no monitoring program in the
groundwater transition zone with surface water.
The nature of groundwater/surface water interaction is
addressed at least partially by streamflow
measurements that indicate gaining and losing reaches
of the various surface water drainages. The impact of
groundwater discharge on surface water quality is
addressed by measuring surface water quality upstream
and downstream of gaining reaches. It is our
understanding that groundwater samples have been
collected from below the bed of the SFCDR to
facilitate assessment of this issue; however, we are
unclear whether this is a regular occurrence or a one-
time event. This comment does not appear to be
requesting specific changes in the LTMO report, and
none are proposed at this time.
6.
Page 3-8
line(13)
This comment is similar to the above comment,
how will this objective be answered without data
from the groundwater transition zone?
See response to specific comment #5 above.
Draft Long Term Monitoring Plan Comments - Final.doc
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United States Environmental Protection Agency, Region 10 Review Comments on the Draft Long-Term Monitoring
Network Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section
Page
Line/Para
Comment
Response
7.
Page 4-5
Table 4.3
Typo, first column of the table Training 2 should
be Transect 2.
Text fixed in table.
Section 4.4
Laboratory
Analytical
Program
Page 4-21
line (20)
I concur with the recommendations of collecting
and reporting the results of the water quality
field parameters during the purging and
sampling of the monitoring wells. The
parameters that should be collected are dissolved
oxygen, pH, oxidation-reduction potential,
specific conductance, turbidity and groundwater
elevations. Also, why are dissolved metals
collected instead of total for groundwater water
quality?
Line 20 will be revised to read: "// is assumed that pH,
specific conductance, turbidity, and depth to water are
being measured during well purging... .Measurement of
dissolved oxygen and oxidation-reduction potential
during purging is recommended for the same reason.
These are simple field measurements...."
Given that total metal concentrations can be heavily
influenced by sample turbidity, they may not be an
accurate reflection of what is actually migrating in the
groundwater. Dissolved metals probably provide a
more accurate measurement of the concentrations of
metals dissolved in and migrating with the
groundwater.
9.
Section 5.1
Methodology
for Temporal
Trend
Analysis of
Contaminant
Concentrations
Page 5-2&3
line (9& 2)
Four data points can be used to determine a
trend but that it would be better to recommend
in this report a minimum of eight data point or
two years of quarterly data. Also, why was a
90% confidence level used to define statistically
significant trend instead of 95% confidence
level?
Text added to clarify the decision to include >6
sampling points per LTMO guidance
recommendations.
"Probably" increasing/decreasing trend classifications
were added to differentiate between the 90% and 95%
confidence levels. Using a lower confidence level
allows for the earlier identification of trends.
10.
Section 7
Summary of
Long-Term
Monitoring
Optimization
Evaluation
Page 7-1
line (16)
This paragraph does imply that the existing
monitoring network is effective to monitor the
remedial action from Phase 1 but I believe a
statement is needed in this paragraph to state
that fact. Also, it would be good to add to the
last sentence that with theses changes or
refinements to the groundwater monitoring
network it will still meet the remedial action
objectives for the site cleanup within an
appropriate time frame.
The following text will be added to the end of line 16:
" and without sacrificing achievement of monitoring
objectives."
Draft Long Term Monitoring Plan Comments - Final.doc
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
General Comments. Nick Zilka
Item
No.
Comment
Response
1.
Overall the document is well written, the procedures used are clearly described, and the
conclusions well reasoned. We commend the authors on their efforts to analyze a large amount of
information and distill it into monitoring recommendations.
Noted.
2.
The primary source for dissolved metals in groundwater within OU2 is metal-rich sediment within
the vadose zone. The two release and transport mechanisms for metals from this source are
unsaturated flow downward through the vadose zone and the annual rise and fall of the water
table. The magnitude of dissolved metal release by these mechanisms is related to the magnitude
of the hydrologic event. The LTMO report does not deal with the primary metal source, the
release and transport mechanisms and the importance of major hydrologic events. This
topic is important and should be addressed in the document.
Detailed analysis of metals fate and transport in the
vadose zone is beyond the scope of this LTMO task.
However, by virtue of the fact that groundwater
quality data are used as the basis for the LTMO
evaluation, the LTMO assessment is influenced by
source zone release and transport mechanisms and
hydrologic events to the extent that these affect
groundwater quality. The following new paragraph
will be added between the first and second paragraphs
in Section 2.3:
"The primary source for dissolved metals in
groundwater within OU2 is metal-rich sediment within
the vadose zone. The two release and transport
mechanisms for metals from this source are
unsaturated flow downward through the vadose zone
and the seasonal rise and fall of the water table. The
magnitude of dissolved metal release by these
mechanisms is related to the magnitude of the
hydrologic event. Major hydrologic events, such as
occurred in 1996 to 1997, can result in a relatively
large influx of metals into the groundwater system due
to enhanced flushing of metals out of the vadose zone."
The LTMO report includes analysis of surface and groundwater data collected during the period
of February 2000 through October 2004. This time period does not include the major hydrologic
event that occurred in the basin in 1996-1997. Peak flows on the South Fork of the Coeur
d'Alene River (SFCDR) in February 1996 at the Elizabeth Park gage (7,400 cfs) are slightly less
than the 50-year recurrence interval flow (7,778 cfs) as presented in Table 3-3 in the Conceptual
Site Model Report (CH2M HILL 2005). The average annual flow of the SFCDR during the 1997
water year (564 cfs) was considerably higher than the average for the 1987-2003 period of record
The 2000-2004 data were used to correspond with the
period of time after the Phase I remedial activities
occurred, as including data from before these actions
could result in misleading trends. Because of the
frequent sampling, the 2000-2004 time frame provides
a large amount of data appropriate for a statistical
evaluation.
Draft Long Term Monitoring Plan Comments - Final.doc
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
4.
5.
Comment
(327 cfs) (CH2M HILL 2005, p.3-10). Groundwater levels peaked in many wells during this
period with associated metal release from the two mechanisms described under the previous
general comment. The 2000-2004 database included in the LTMO analysis does not include
this high flow event, the associated metal loading to groundwater and the possible impacts
on spatial statistical analysis of contaminant concentrations and statistical analysis of
temporal trends in contaminant concentrations. These topics are important and should be
addressed in the document.
Throughout the analysis the authors seem to attribute changes in COC concentrations to remedial
actions only. This is probably an invalid assumption. There are many environmental variables
that could impact the COC concentrations. This then calls into questions what the trends tell you.
If you do not understand the factors influencing the variability in the COC you can not attribute
the trends to the Phase 1 remedial action.
Does the shift to a reduced frequency of sampling negatively impact the statistical analyses in any
way?
Response
Recommendations were added to Section 4 to
temporarily increase the frequency of surface water and
groundwater monitoring in the event of an unusually
large hydrologic event to capture potential effects of
dissolved metal releases.
Text will be reviewed and revised as appropriate in
light of this comment.
Any future sampling will only serve to add to and
enhance the large amount of concentration trend
information already available for the site.
Draft Long Term Monitoring Plan Comments - Final.doc
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Specific comments
Item
No.
1.
2.
o
J.
4.
5.
6.
7.
8.
9.
10.
Section/Page
Title
Page 2-3
P.2-4
Table 3. 2
Page 3-8
P.3-8
Table 3.4
Table 3. 6
Page 4-3
Line
line 24
lines 17-
19
line 18
line 21
Tables 4.1
and 4.2
Comment
OU2 should appear in the title.
needs a period at the end of the sentence.
We're not sure the blanket statement that depth to groundwater is 8-
10 feet (east) and 10-25 feet (west and central) is correct, e.g.
Kellogg well values are greater than 10 feet.
Table indicates that BH-RR-0001 is sampled quarterly. In fact, it is
only sampled during the high flow sampling events. The same is
true for Portal Gulch.
Is "plume" the best word for the widespread contamination in the
BHSS?
Several RAs were not "designed" to impact water quality but it was
anticipated they would. Suggest "expected".
"wells" should be taken out of the title of the last 3 columns since
this is a surface water table. Same with the first column in Table 3.6.
Table compares the surface water concentrations to the AWQC.
The AWQC is for total metals not dissolved so the comparison to
the dissolved fraction is in error.
The concepts of performance and sentry wells mentioned on page 4-
1 do not fit well with the Bunker Hill site.
Excellent.
Response
Done.
Done.
This information came from Section 3.4.2.1 of the
CSM report. The word "generally" will be inserted in
line 17 between "table" and "ranges" to indicate that
this there is some variability. In addition, the end of
this sentence will be revised to read: " . . .western
portions; however, some variability exists"
Sampling frequencies changed in table.
Text modified.
Text changed to "expected".
"Wells" changed to "Surface Water Stations".
The AWQC was used for both total and dissolved
metals to be consistent with CSM Table 5-9.
Disagree; most wells screened in the upper aquifer at
the site can be termed "performance" wells given that
they are located within contaminated areas. Wells
installed at the far western edge of OU2 can be
considered sentry wells.
Noted.
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/Page
Line
Comment
Response
11.
Page 4-4
The mass flux justification in section 4.2.1 for sampling the transect
wells is not valid. The mass flux estimates from these wells have a
high range of potential error because of uncertainty in estimation of
a representative hydraulic conductivity value.
Agree that this is the case. However, if the same
hydraulic information and the same wells are used in
mass flux calculations from year to year, relative
changes in mass flux can be determined, which could
be useful indicators of remedial effectiveness. The text
in Section 4.2.1 will be revised per this comment and
the response.
12.
P.4-5
Table 4.3
Rationale for BH-GG-GW-0007 recommends a higher sampling
frequency but lists a reduced frequency.
The rationale given for use of a higher sampling
frequency is not entirely correct. The sampling
frequency will be retained as annual and the rationale
will be revised.
It is our experience that semiannual monitoring is
considered relatively frequent in the context of a long-
term monitoring program (i.e., beyond the
characterization stage).
13.
P.4-5
Table 4.3
Interesting. In the past we have done monthly and quarterly
sampling and now semiannual is considered frequent.
14.
We are surprised that all four of the wells at the mouth of
Government Gulch are included in Table 4-3 (GG-GW-0005, 6, 7
and 8). One of the well pairs could be excluded from the list with
little data loss.
Agree that these well pairs are in relatively close
proximity to each other and may be providing some
redundant information. GW-0006 and 0008 were
retained to further assess potential increasing trends in
metal concentrations (Cd in 0006 and Zn in 0008). Of
the shallow wells, GW-0007 has consistently higher
cadmium and zinc concentrations than 0005, but
consistently lower lead concentrations. The lead
concentrations in 0005 consistently exceed the MCL.
We recommend continued low-frequency sampling of
each of these wells for the time being to get the "full
story" regarding groundwater quality at the mouth of
Government Gulch.
15.
Page 4-10
The three bullets on page 4-10 raise several questions. Do we need
quarterly or even monthly sampling on a minimum number of wells
to gain an understanding of the seasonal changes to the groundwater
system? Rapid changes in water quality are present in the data set
prior to 2000, at least some of which are related to the extreme
hydrologic event. Second, does the change from quarterly to
semiannual and annual sampling impact the future statistical
analysis of the database? Finally, we need to select a time of year
From February 2000 to October 2004, a total of 66
wells had been sampled at least 8 times (59 of which
were sampled quarterly), and 32 wells had been
sampled quarterly at least 20 times. The maximum
number of sampling events performed on wells
reviewed for this LTMO evaluation during this
approximately 4.5-year period is 45. It is our opinion
that continuation of monthly to quarterly monitoring is
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
16.
17.
18.
19.
20.
Section/Page
Page 4-12
P.4-12
Page 4-14
Line
first bullet
lines
8,10,12,
14
line 3
Comment
for sampling the upper aquifer wells that will now go to annual
measurements.
When the recommendation is to go to annual monitoring the authors
do not discuss the time of year to perform this monitoring. We are
left to assume that it is during the late summer early fall low flow
period.
do those well names need "-U" at the end?
Are these pairs truly co-locations? For example, 402 and 403 are
near each other but don't behave the same.
says well BH-SF-W-0018-U has had exceedances of cadmium and
lead, but page 4-13 says there have been no exceedances at this well.
The statement on lines 15 and 16 in section 4.2.4 on page 4-16 that
no Phase II remedial actions will be done in Government Gulch
probably is incorrect and should be removed.
Response
not necessary. At this point, the money would be
better spent on remedial activities. However, as noted
in the response to General Comment #3,
recommendations were added to Section 4 to
temporarily increase the frequency of surface water
and groundwater monitoring in the event of an
unusually large hydrologic event to capture potential
effects of dissolved metal releases.
Collection of additional data (even at a reduced
frequency) will enlarge the data set and aid the
statistical analysis of the database.
Parsons has not performed sufficient analysis of the
historical data to recommend a specific time of year for
annual measurements. However, it makes sense to
perform annual sampling at a time of year when metal
concentrations have historically been relatively
elevated.
A recommendation to perform the annual sampling at a
time of year when metal concentrations in groundwater
are typically relatively elevated will be added to the
text.
Well names fixed in text.
These pairs are co-located in an areal sense but are not
screened over the same depth interval vertically. We
feel that continued monitoring of both wells that
comprise each pair is unnecessary for the reasons given
in the text of the report. While trends exhibited by 403
are not a carbon copy of the 402 trends they are
generally similar and 403 concentrations from 4/00 to
10/04 were always lower than 402 concentrations.
Text modified to clarify that the exceedances discussed
refer to well BH-SF-W-0121-U.
The following text will be added to the end of line 17:
"If this assumption is incorrect, then a semi-annual
sampling frequency is recommended to support Phase
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/Page
Line
Comment
Response
// remedial decisions, followed by a reduction to
annual sampling" Table 4.3 will be modified
accordingly.
21.
P. 4-16
We are not sure we understand Government Gulch as well as the
text implies. We don't know where gaining and losing reaches
occur and why the water quality changes are occurring.
Noted; see response to specific comment #20.
22.
Page 4-16
last
paragraph
starting on
that page
Well BH-ILF-GW-0001 was installed in 2000, but has only been
sampled twice (4/25/01 and 1/15/03) because it has been dry every
other quarter (and once could not be accessed due to snow). We
checked again on 10/24/05, and the depth to bottom was 18.98', and
the depth to water was 17.21', indicating only 1.77' of water. A low-
flow pump was not ordered for this well. This well has not been
included in the monitoring program since the change to the low-flow
method in April, 2003.
Noted; this information will be added to the text on
page 4-16. The text will also be amended to
recommend that this well be sampled when possible
using another feasible method given the small
thickness of the water column (e.g., non-dedicated
peristaltic pump). If a sample can be obtained, it
would be better to obtain data for this well using an
alternate method rather than not sample it because it
does not contain a dedicated low-flow pump.
23.
Page 4-17
line 13
Should not say "well" since this is discussing surface water
locations.
The term "monitoring station" will be used instead.
24.
P. 4-18
Table 4.4
The Milo outfalls are not redundant - one drains the old stormwater
system and the other the new. Also, retain seeps for technical and
public relations issues.
Both Milo outfalls will be retained.
25.
There is more going on here than just groundwater discharge. There
is speculation that an old CIA dividing dike is acting as a
preferential route, the Transportation Department used to have to
resurface the highway periodically due to subsidence, and the RI
identified the seeps as the largest loader to the river.
If the primary reason for sampling the seeps is to
determine metals loading to the river, it seems best to
determine the net impact of metals loading from the
CIA by sampling the river directly at the upstream and
downstream ends of the CIA (and perhaps also at
intermediate locations adjacent to the CIA depending
on the level of detail desired). The seeps only indicate
metals discharge at one point along a gaining reach of
the river adjacent to the CIA that is estimated to extend
for nearly 7000 feet (per Figure 3-41 of the CSM
report). However, continued sampling of the seeps
would serve to indicate how groundwater quality in
this portion of the CIA is changing over time in
response to the Phase I remedial actions that were
performed. We are not familiar with the public
relations issues alluded to in comment #24. Sampling
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
26.
27.
28.
29.
30.
31.
32.
33.
34.
Section/Page
Page 4-19
P. 4-20
Page 4-21
P. 4-23
Page 4-23
Page 4-24
Line
line 4
lines 11-
25
last
paragraph
lines 22
and 23
line 14
Comment
should "groundwater" instead be "surface water"?
See comment above for page 4-18.
Both pH and ORP are measured.
We are surprised no well additions are proposed for Smelterville
Flats. There are very few wells out there due to the removal action.
do these well names really need the "-U" ?
Doesn't this well name need the "-U" at the end?
The word "well" is included in the text in section 4.3 and on Table
4.4 and should be removed.
We question the value of the transect flux calculations mentioned in
section 4.5 and the addition of monitor wells to several transects to
help in flux calculations. However, these wells would be helpful in
better understanding subsurface sources and metal transport.
The introductory paragraph of section 5 on page 5-1 does not fit
well with the conceptual model of where and how metal sources
exist within the Box and how and where metals are introduced into
groundwater and surface water systems.
Response
of the seeps at a semiannual frequency will be
recommended in the final report.
Text changed to "surface water" .
Text refers to surface water.
Noted.
Agree. A recommendation for installation of at least 8
additional wells in the Smelterville Flats area (4 upper
aquifer and 4 lower aquifer) will be added to the
report.
U removed from well name.
U added to well name.
Changed from "well" to "surface water station".
See response to specific comment #11.
The referenced paragraph will be revised to read as
follows: "Target analyte concentrations measured at
different points in time (temporal data) can be
examined graphically or using statistical tests to
evaluate temporal trends. In general, if removal of
contaminant mass is occurring in the subsurface as a
consequence of attenuation processes (e.g., metals
precipitation) or remedial actions (e.g., source
removal), mass removal will be indicated by a
decrease in analyte concentrations through time at a
particular sampling location, as a decrease in analyte
concentrations with increasing distance from source
areas, and/or as a change in the suite ofanalytes
detected through time or with increasing migration
distance.
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
35.
36.
37.
38.
39.
40.
Section/Page
Line
Comment
Metal-rich sediment is present in the vadose zone throughout the
valley floor.
Dissolved metals are introduced into the groundwater seasonally by
water movement through the vadose zone and/or by seasonal
saturation of the lower portion of the vadose zone by water-level
changes.
Remedial actions have resulted in significant removal of the metal-
rich sediment in only a portion of OU2 (dominantly the Smelterville
Flats with partial removals in other areas).
The annual loading of dissolved metals to groundwater varies
widely dependent on hydrologic conditions. The 2000-2004 period
of data represents conditions after a significant hydrologic event.
The temporal statistical analysis must consider the database in light
of long-term hydrologic conditions.
The concept of "source wells" and "downgradient wells" in section
5.2 on page 5-5 is confusing. One would presume that wells
downgradient from metal source areas could have metal
concentrations above MCL levels.
Response
Temporal analysis ofanalyte concentrations for O U2
media is complicated by the fact that metal-rich
sediment is present in the vadose zone throughout the
SFCDR valley floor. In addition, the annual loading
of dissolved metals to groundwater can vary widely
with hydrologic conditions. Significant increases in
the rate of metal loading to groundwater can occur
following unusally high-magnitude rainfall or
snowmelt events. Therefore, the conclusions derived
from the temporal analysis should consider the
potential impacts of time-varying hydrologic
conditions."
Noted. See response to comment #34.
Noted. See response to comment #34.
Noted.
Please see response for General Comment #3 and
Specific Comment #34.
Noted. See response to comment #34. The temporal
analysis results will be reviewed in light of this
comment and the accompanying text will be revised as
appropriate.
We agree that designation of source and downgradient
wells for this site is more difficult and confusing than
for a typical site that has a defined contaminant plume.
However, we believe that the way the OU2 wells were
designated as source or downgradient is appropriate for
the Bunker Hill LTMO analysis. Most upper aquifer
wells were designated as source wells given the
widespread distribution of source material throughout
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
Section/Page
Line
Comment
Response
the area. However, if a well did not exhibit MCL
exceedances then it seems reasonable to assume that it
is not installed in a source area—hence the
downgradient designation. It is our understanding that
source material is not present in the lower aquifer
(beneath the bounding aquitard); therefore, these wells
were classified as being downgradient (in a vertical
sense) from source areas. In reality, some lower
aquifer wells may actually be cross-gradient or
upgradient (again, in a vertical sense) from source
areas but as long as they are not considered sentry
wells they are treated the same on Figure 5.4 (e.g., if a
lower aquifer well does not exhibit a temporal trend,
and is not a downgradient sentry well, then it follows
the same route on the flowchart regardless of whether
it is downgradient, cross-gradient, or upgradient).
41.
Figure 5.4
Interesting but does not fit the OU2 area because metal sources exist
over most of the area.
Although the Bunker Hill site does not fit the typical
mold of a groundwater monitoring site, the temporal
trend flow chart still is applicable because (as indicated
in the comment) most wells were classified as "source
wells" (as shown in Table 5.1) and temporal
recommendations were made on that basis.
42.
The utility of Table 5.1 is limited because the database does not
represent the range of hydrologic conditions that can and will occur
within the area.
The 2000-2004 data selection was appropriate for the
LTMO analysis. Please see response for comment
General #3.
43.
P. 5-8
Table 5.1
It would be good to differentiate between "exclude" and "reduce".
Table 5.1 presents only the results from 1 of 3 lines of
evidence in the evaluation. The decision whether to
reduce or exclude is based on the combined temporal,
spatial and qualitative evaluation and is presented in
Table 7.1.
44.
P. 5-8
Table 5.1
Reduce vs. exclude seems to rely heavily on the presence of a trend.
Lack of a trend may be good data to understand system or point out
a lack of understanding. Water quality is not changing - why?
As stated in Section 5.1, continued sampling of 'no-
trend' wells with low temporal variation provides
limited information in terms of temporal trend
evaluation (i.e., you're not likely to learn anything new
in the future). The qualitative and/or spatial
evaluation may identify other reasons that a well with
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TerraGraphics Environmental Engineering Review Comments on the Draft Long-Term Monitoring Network
Optimization Evaluation for Bunker Hill Mining and Metallurgical Complex Superfund Site
(Continued)
Item
No.
45.
46.
47.
48.
49.
50.
Section/Page
Table 6.2
and 6. 3
Tables 6.2,
6.3, and 6.4
P. 7-3
P. 7-4
Page 7-8
Line
Table 7.1
Table 7-2
line 21
Comment
page numbers say 5-9 and 5-10 instead of 6-9 and 6-10.
Do not have footnotes.
Within the constraints of the database selection, section 7 presents a
good comparison of the qualitative and quantitative approaches to
the evaluation of the monitoring network.
Retain 403 and sample semiannually; Qualitative - not a duplication
of depth, 14 vs. 22. Spatial - in a high density well area, true, but is
at CIA seeps. Temporal - 402 and 403 often don't behave the same
way in term of metal concentrations
Take surface samples at mouths of Grouse, Government, and
Deadwood quarterly to pair up with hillsides monitoring (turbidity).
add a space between "evaluation" and "of at the end of the line.
Response
no temporal trend may be important.
Fixed.
Footnotes added to tables.
Noted.
See response to CH2M Hill comment #14. Graphical
analysis of historical (2000-2004) data for wells 0402-
U and 0403-U indicates that sampling of 0402-U will
allow the maximum metal concentrations present in
groundwater at this location to be tracked over time
(concentrations decrease with depth in the upper
aquifer at this location).
The rationale for this recommendation is unclear. We
are not familiar with hillside monitoring being
performed in association with Grouse and Deadwood
gulches. In addition, the LTMO evaluation does not
recommend quarterly monitoring of Government
Gulch wells. The role of turbidity in supporting this
recommendation is not clear to us. No changes to the
LTMO report due to this comment are proposed at this
time; further clarification would be required.
Done.
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