20080868 Ver 2_Section II E Q5 Metals 2021 PCS Creeks Report_20220605

E. Question 5- Has mining increased contaminate [sic] levels within creek
sediments to levels that could impact fish or invertebrates?
To be compliant with the 2015 EPA Publication SW-846, in 2016 certified laboratories
replaced Method 6010C with Method 6010D and Method 6020A with Method 6020B. With
the change in methods, the limit of quantification, control limit, or report limit (LOQ/CL/RL) had
to be raised for some metals in order to meet the QA/QC criteria for analysis which resulted
in a higher LOQ/CL/RL for some metals in some creeks than previous limits for the same
metal. (As explained by Greg Dickson, Technical Director of SGS laboratory, the QA/QC
criteria for the lowest level standard run by the SGS lab with each batch were much tighter
than before. These criteria provide better data for results that are at the lower end of the
calibration range). For tabular depictions of the data, the current year is shown but not
included in the calculation of the mean for the previous years so that it is readily apparent how
the current year value compares to the value of the ongoing mean of the previous years and
to the Effects Range Low/Effects Range Medium (ERL/ERM); also, only the detected
concentrations are used in calculations of the means for these tables. However, when the
raw data are entered into the spreadsheets for statistical comparisons and figure depictions
the < sign is removed and the reporting limit value is used as the concentration "detected" for
that metal that year and the current year is combined into the data set for analysis. The
reporting limit for any given metal can vary from year to year and from creek to creek within a
year due to different factors applied to the laboratory analysis of each sample; these factors
may include differences in initial sample volume and dilution factors.
The ERL/ERM concepts represent water quality concentrations for specific elements
or compounds below which adverse toxicological effects rarely occur and above which
adverse toxicological effects frequently occur (NOAA 1999). The ERL is generally the 10th
percentile concentration and the ERM is generally set to the 50th percentile concentration.
Concentrations that occur between the ERL and ERM reflect the "possible effects range" and
concentrations below the ERL reflect the "low end of a continuum roughly relating bulk
chemistry with toxicity" (O'Conner 2004). Therefore, ERL and ERM are not predictive of
toxicity, but do indicate sediment toxicity probability values and are guidelines that relate
sediment contaminant concentration with possible toxicological outcomes in exposed
organisms, either through the sediment directly, or through the aquatic environment. The
National Oceanic and Atmospheric Administration (NOAA) has published additional
guidelines and recommendations that include threshold effects levels (TELs) and probable
effects levels (PELs), which are sometimes lower (i.e., more protective) than ERLs and ERMs
(NOAA 2008).
In estuarine and coastal areas, metal concentrations are influenced by a large variety
of physical and chemical factors, which include the combination of natural and anthropogenic
inputs, erosion, activities of organisms in the environment, and interactions of metals with
particles and sediments (Khan et al., 2014). Therefore, due to these dynamic physical and
chemical factors present in estuarine and coastal areas, collected samples can exhibit
enormous temporal variability even when collected repeatedly from the same physical site. In
addition, retention time of samples in collection containers also can influence apparent metal
concentrations in solution due to sorption of metals to certain types of plastics (samples are
collected in amber glass jars provided by lab to reduce this effect). These multiple factors
affect metal concentrations from year to year, even from the same creeks, and may cause
increased variability.
II-E-1

Figure II-E1 illustrates metal sediment data only for the seven creeks for which both
pre- and post -Mod Alt L data are available (Jacks Creek, Jacobs Creek, Drinkwater Creek,
Tooley Creek, Huddles Cut, Porter Creek, and DCUT11). Pre -Mod Alt L data were compared
to post -Mod Alt L data for each creek. If only one year of data was available, values represent
data from that year and if multiple years of data were available, values represent average data
across the multiple years for each metal and each creek. Figure II-E2 (a — d), Figure II-E3
(bar chart), and Figure II-E4 (a - b; line graph) show sediment metals averages combined into
various categories for comparison. When all creeks with pre- and post -Mod Alt L data were
combined and all years were combined into either pre- or post -Mod Alt L years, of the 10
metals included in the evaluation, three (Ag, Mo, Se) were significantly higher in the post,
three (Al, Cr, Zn) were significantly lower, and four (As, Cd, Cu, Fe) showed no significant
post -Mod Alt L change (Table II-E1).
Also of note: only one creek may have served as a control creek, pre -Mod Alt L non -
control creek, or post -Mod Alt L non -control creek for a given year (Table II-E2). Twelve (12)
years and seven creeks comprise the post -Mod Alt L period, and many of the creeks do exhibit
some variability in metals values, often due to more or less sand in the samples from year to
year, particularly in Huddles Cut.
Evaluation of metals within each individual creek resulted in the following significant
increases between pre- and post -Mod Alt L data sets (p=<0.05) with direct replacement of
censored data (inequalities) as the detection limit(s): Jacks Creek — increase in Ag, Mo, and
Se; Jacobs Creek — increase in Ag, Cd, Mo, and Se; Drinkwater Creek — increase in Ag, Cd,
Mo, and Se; Tooley Creek — increase in Ag, Mo, and Se; Huddles Cut — increase in Ag; and
Porter Creek — increase in Ag, Cd, Cu, Mo, and Se (Table II-E1). One impact creek (Porter
Creek) showed a post -Mod Alt L increase for Copper, however, Cu detections have never
exceeded the ERL or ERM for this metal. Six impact creeks showed post -Mod Alt L increases
for Ag, three for Cd, and five for Mo; however, it is important to note that for many years of the
entire data set and almost all of the post -Mod Alt L years for these creeks, including 2021, Ag
Cd, and Mo concentrations used in the analysis were the LOQs. Therefore, significant
differences reflect changes in the LOQ rather than in situ changes in detected concentrations
for these three metals. When the LOQ is excluded from the analysis statically significant
increases between pre- and post -Mod Alt L data sets (p=<0.05) are still observed in the
following individual metals: Copper in Porter Creek and Selenium in Jacks Creek, Jacobs
Creek, Tooley Creek, and Porter Creek.
Since 2016, there has been a general increase of Se in all creeks including most
control creeks. Average concentrations of Se were significantly higher in post -Mod Alt L years
compared to pre -Mod Alt L years when all impact creeks were combined and for all individual
impact creeks with the exception of Huddles Cut and DCUT11. Average concentrations of Se
were also higher in all control creeks when pre- and post -Mod Alt L years for each impact
creek were used to divide control creek data for comparison. Se decreased in 12 creeks in
2021 relative to 2020 (six impact creeks: Jacks, Jacobs, Drinkwater, Tooley, Porter, and
DCUT11 and five control creeks: Little, Long, Muddy, PA2, and DCUT19). Se increased in
2021 relative to 2020 in two impact creeks (Broomfield and Huddles Cut) and remained the
same in one control creek (Duck). Comparison of averages for the same years in control
creeks (Muddy for Jacks and Tooley creeks, Little and Long creeks for Jacobs and Drinkwater
creeks, and Duck for Porter Creek) showed similar significant differences in each comparison
(Figure II- E6).
II-E-2

Figures II E2 a - d display average sediment metal concentrations: pre -Mod Alt L years
compared to control creeks (Figure II-E2 a), post -Mod Alt L years compared to control creeks
(Figure II-E2 b), post -Mod Alt L creeks compared to control creeks for 2021 only (Figure II-E2
c), and pre -Mod Alt L years compared to post -Mod Alt L years (impact creeks combined).
Although it is not possible to do statistical analyses on 2021 data for individual creeks as there
was only one replicate per creek, Figure II-E2 c illustrates that metal concentrations in control
creeks were equal to or slightly exceeded metal concentrations in post -Mod Alt L creeks. A
summary chart of sediment metal and Total Organic Carbon (TOC) averages combined into
four categories: all years (impact and control creeks), all pre -Mod Alt L years (impact creeks
only), all post -Mod Alt L years (impact creeks only), and all control creek years is shown in
Figure II-E3. Note that TOC was first measured in 2013; therefore, pre -Mod Alt L values for
TOC are limited to two years in Jacks Creek, one year in Jacobs Creek, three years in Porter
Creek, and five years in DCUT11.
For sediment metals, summary combined information for all creeks by three categories
was also compared across the course of the study for six metals with published ERLs and
ERMs (Table II-E2). Average concentrations for all previous years (2020 and earlier) for all
six metals were below the ERLs for pre -mod Alt L creeks, post -mod Alt L creeks, and control
creeks. For 2021, average concentrations were below the ERLs for all previous years for pre -
mod Alt L creeks, post -mod Alt L creeks, and control creeks. The ERL is not a threshold of
degradation; it represents a 10 percent likelihood of toxicity.
Data in Table II-E2 indicate that the long term average (+/- 1 S.D. for all comparisons
to ERLs/ERMs) for metals detected in the sediment samples in all control creeks was below
the ERL for five of the six metals; Cd was the exception at 0.18 µg/g above the ERL. All 2021
control creek average detections were below the ERL (Ag and Cd were not detected). For
the pre -Mod Alt L creeks, the long term average was below the ERLs for five of the six metals;
again Cd was the exception at 0.58 µg/g above the ERL. For post -Mod Alt L creeks, the long
term average was below the ERLs for four metals; Cd exceeded the ERL by 0.33 µg/g and
the Zn long term average exceeded the ERM by 336.09 µg/g (due to the aforementioned
anomalously high Zn reading in 2015). However, the 2021 seven -creek mean was below the
ERL. All long term pre- and post -Mod Alt L averages (alone and within +/- 1 S.D.) were well
below the ERMs with the exception of Zn. On average, concentrations of all metals in all
creeks have remained about the same or declined over time, although yearly fluctuations up
and down have become more apparent as the dataset grows. The addition of new creeks
can also modify the seven -creek means of both pre- and post -Mod Alt L years. Regardless,
results indicate that metals in the sediment of the studied creeks are unlikely to be associated
with biological effects in exposed organisms as they are consistently below the published
ERMs.
For water column metals, 10 years of data have been collected as part of this study
compared to the 20 years for sediment metals. Figures II-E4 a — II-E4 b show the pre -Mod
Alt L water column metal values combined and compared to post -Mod Alt L values. Figures
II-E5 a — II-E5 b illustrate the water column metal averages across the years- comparing all
creeks averages combined to control creeks averages and impact creek averages, and show
that concentrations are similar among the creek types; no statistical differences were found
between water column metals in post -Mod Alt L creeks compared to controls (as was done
for the sediments, LOQs were substituted for all non -detects in these figures and analysis).
When post -Mod Alt L years were compared to pre -Mod Alt L years, no metal water column
values in post -Mod Alt L years were significantly different relative to pre -Mod Alt L years.
II-E-3

Table II-E3 shows the percentage of years for each creek where metals were below
the LOQ/CL/RL for the sediment and the water column. For some metals, the change in
methods in 2016 mentioned above did not seem to affect the percentage of non -detects where
a metal had seldom been detected up to 2016; however, for other metals (e.g. Cr and Cu), it
did seem to affect detection. No sediment metals have been detected for every sample year
in each creek; As, Cr, Cu, and Zn were detected in most years in most creeks; Ag and Mo
were seldom detected. Within the water column, Ag has never been detected in any creek
sample and Cd and Mo were seldom detected (Cd has not been detected to date in either
DCUT19, Duck Creek, Broomfield Swamp Creek, or SCUT1).
Answer: Results show that with the exception of Zn in the sediment at Jacks
Creek in 2015, concentrations of sediment metals or concentrations of water column
metals in the studied creeks are not likely to be associated with detectable biological
effects. No statistical differences and no obvious trends have been found to indicate
that mine continuation has changed either sediment or water column metal
concentration relative to changes observed in control creeks or relative to changes
observed pre -Mod Alt L in all creeks but Jacks Creek. In 2015, the first year for which
post -Mod Alt L was available for Jacks Creek, levels of Zn in the sediment exceeded
the ERL and ERM. Two samples from Jacks Creek in 2016 showed values for Zn within
the range of all years previous to 2015. The 2021 averages for all combined post -Mod
Alt L creeks, which includes Jacks Creek, were below both the ERL and ERM.
II-E-4

♦ Drinkwater Pre -Mod Alt L
• Jacobs Post -Mod Alt L
• Jacobs Pre -Mod Alt L
• Jacks Post -Mod Alt L
• Jacks Pre -Mod Alt L
X Huddles Cut Pre -Mod Alt L X Huddles Cut Post -Mod Alt L
• Tooley Post -Mod Alt L
♦ Drinkwater Post -Mod Alt L • Tooley Pre -Mod Alt L
— DCUT11 Post -Mod Alt L
— DCUT11 Pre -Mod Alt L
+ Porter Post -Mod Alt L
+ Porter Pre -Mod Alt L
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II-E-5

SEDIMENTS
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METALS (ALLYEARS COMBINED)
C
AVERAGE SEDIMENT METALS ( ALL SITES)
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50
40
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*Al and Fe reported in %and all other metals reported in µg g
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METALS (2021 ONLY)
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AVERAGE SEDIMENT METALS ( ALL SITES)
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*Al and Fe reported in %and all other metals reported in µe•g
80
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40
30
20
10
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As
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METALS (ALLYEARS COMBINED)
8
Al Fe
Figure II-E2 a - d. Average sediment metals (µg/g) for all control creeks combined across years and creeks with both pre-
b) Average sediment metals for post -Mod Alt L creeks relative to control creeks. c) Average sediment metals for post -Mod
Alt L years relative to post -Mod Alt L years. When comparing combined creek data from pre -Mod Alt L years to post -Mod
for Ag, Mo, and Se. Significantly higher concentration of Ag and Mo reflect changes in the LOQ rather than changes in det
and post -Mod Alt L data. a) Average sediment metals for pre -Mod Alt L creeks relative to control creeks.
Alt L creeks relative to control creeks, 2021 concentrations only. d) Average sediment metals for pre -Mod
Alt L years, statistical (p < 0.05) elevations in average sediment metals for post -Mod Alt L years occurred
ected concentrations for these metals.
I I-E-6

Sediment Metal Averages (µgig) and TOC(g/kg)
8
Q Q Q Q Q Q Q a Q a
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I I-E-7

1200.0
1000.0
800.0
J
600.0
400.0
200.0
0.0
Pre- and Post -Mod Alt L Creeks
Water Column Metal Averages
All Years Combined
Ag As Cd Cr Cu Mo Se Zn Fe
Reporting limit used for non -detections
■ Pre -Mod
■ Post -Mod
Figure II-E4a. Combined pre -Mod Alt L water column metals
concentrations compared to combined post -Mod Alt L values with all
detected values and any <LOQs as detected values.
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
Pre- and Post -Mod Alt L Creeks
Water Column Metal Averages
All Years Combined
r
As Cd Cr Cu Mo Se Zn
Only detections at or above reporting limit used
Ag has never been detected
■ Pre -Mod
Post -Mod
Figure II-E4b. Combined pre -Mod Alt L water column metals
concentrations compared to combined post -Mod Alt L values with only
detections at or above LOQ.
II-E-8

Water Column Metal Averages All Years All Creeks
1,200
1,000
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c 800
r.
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L
a.)600
V
0
To
w
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111 --- ...
Ag As Cd Cr Cu Fe Ma Se Zn
All creeks
Control creeks Other creeks
Figure II-E5a. Water column metal means for all years (2011-2021) for all
creeks by classification. LOQ/Reporting limit used as data point when metal
was not detected or detected below the limit.
Metal concentration pg/L
Water Column Metal Averages All Years All Creeks
(without Fe)
100
90
80
70
60
50
40
30
20
10
0
. . I . .
Ag As Cd Cr Cu Mo Se Zn
All Creeks • Control Creeks Other Creeks
Figure II-E5b. Water column metal means compared for all years (2011-2021)
by classification without Fe shown. LOQ/Reporting limit used as data point
when metal was not detected or detected below the limit.
I I-E-9

Figure II-E6 a - e. Sediment selenium values for individual impact creeks and control creeks where significant increases were found pre- vs post -Mod Alt L. Black line indicates the separation between pre -
and post -Mod Alt L years.
Sediment Selenium (p ig)
7
6
5
4
3
2
1
0
Jacks Creek Yearly Reported Sediment Selenium
No sample
for Muddy
Creek in
2002
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N N N N N N N
—0—Jacks --f--Muddy (Control Creek)
Sediment Selenium (pg/g)
Sediment Selenium (peg)
Jacobs Creek Yearly Reported Sediment Selenium
7 -
6 -
5 -
4 -
3 -
2 -
1
0
2011 2012
—e—Jacobs
/
/ /
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. •. /
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2013 2014 2015 2016 2017 2018 2019 2020 2021
Years
--l-- Little (Control Creek)
Tooley Creek Yearly Reported Sediment Selenium
Years
—0— Tooley --♦-- Muddy (Control Creek)
d
Sediment Selenium (µg/g)
Long (Control Creek)
Sediment Selenium (ug/g)
Drinkwater Creek Yearly Reported Sediment Selenium
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6
5
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2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Years
—di— Drinkwater --k-- Little (Control Creek) Long (Control Creek)
Porter Creek Yearly Reported Sediment Selenium
7
6
5
4
3
1
0
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Years
+ Porter — ■— Duck (Control Creek)
e
II-E-10

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II-E-11

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II-E-12

Table II-E3. Percent of samples for each creek where metals were not detected (below LOQ/CL/RL) in
sediment (a) or the water column (b). The data set varies by creek from 21 years for Muddy Creek
sediment to three years for Broomfield Swamp Creek and SCUT1 sediment and water column; number
of sample years are shown in parenthesis next to creek name.
Percent of sample years in each creek where metals were below detection (<LOQ/CL/RL)
a. sediment
Metal (µg/g; % for Fe)
Creek
Broomfield (3)
SCUT1 (3)
Jacks (18)
Little (11)
Jacobs (11)
PA2 (11)
Drinkwater (11)
Long (11)
Tooley (15)
Muddy (21)
Huddles Cut (18)
Porter (11)
DCUT11 (9)
DCUT19 (9)
Duck (11)
Al Ag As Cd Cr Cu Fe Mo Se Zn
0 100 0 100 0 0 0 67 0 0
0 100 0 100 0 0 0 100 0 0
6 50 0 22 0 0 6 50 0 0
9 91 0 36 0 0 9 82 9 0
9 82 0 45 0 0 9 91 0 0
9 91 0 36 0 0 9 82 9 0
9 91 0 36 0 0 9 91 0 0
9 82 0 36 0 0 9 91 0 0
7 60 0 27 0 0 7 67 0 0
5 38 0 19 0 0 5 43 0 0
11 56 28 33 6 33 11 50 39 11
9 82 0 36 0 0 0 91 0 0
11 89 0 56 0 0 11 89 0 0
11 100 11 56 0 0 11 78 11 0
0 91 0 64 0 0 0 73 0 0
b. water column (per the plan, Al is not measured)
Metal (µg/L)
Creek Al Ag As Cd Cr Cu Fe Mo Se Zn
Broomfield (3) NA 100 100 100 100 100 33 100 100 100
SCUT1 (3) NA 100 100 100 100 100 0 100 100 100
Jacks (11) NA 100 55 91 55 55 45 91 55 82
Little (11) NA 100 55 91 55 55 45 82 64 64
Jacobs (11) NA 100 55 91 55 55 55 91 55 73
PA2 (11) NA 100 36 91 55 55 64 82 45 73
Drinkwater(11) NA 100 64 91 55 55 55 82 45 82
Long (11) NA 100 55 91 55 55 64 73 55 73
Tooley(11) NA 100 64 91 55 45 64 91 55 73
Muddy(11) NA 100 55 91 55 55 64 82 45 73
Huddles Cut (11) NA 100 55 91 55 55 36 82 55 73
Porter (11) NA 100 64 91 55 45 64 91 45 73
DCUT11 (9) NA 100 67 89 67 56 22 78 67 67
DCUT19 (9) NA 100 67 100 67 67 44 56 56 67
Duck(11) NA 100 64 100 64 55 45 91 45 73
Note: Laboratory equipment changed once and laboratory methods changed twice over the course of
the study to date.
II-E-13