20080868 Ver 2_Section III A Salinity 2021 PCS Creeks Report_20220605

III. ADDITIONAL DISCUSSION OF SUMMARY RESULTS BY PARAMETER
A. SALINITY AND ENVIRONMENTAL VARIABLES
For summary information on rainfall, other weather related events, and Tar River
discharge refer to Sections I-D through I-G. All salinity monitoring locations are associated with
South Creek and its tributaries, Pamlico River and its tributaries, or Durham Creek and its
tributaries. Both South Creek and Durham Creek are large tributaries to the Pamlico River (the
Tar River becomes the Pamlico River at Washington NC, approximately 16.9 miles upstream from
Durham Creek). The Pamlico River salinity monitor (PS1) was removed prior to Hurricane
Florence in September of 2018 for safety. Due to storm damage to the breakwater and pier, PS1
was not re -deployed until early 2020 when repairs were completed. Data from salinity monitors at
HS1 and HS2 have endured the most loss over recent sample years due to damage caused by
unstable and dry conditions. Because of this, 2020 represented the last full year of salinity data
for these two stations and salinity measurements are now observed twice a month by a YSI Pro
Plus instrument at these two sites.
Table III -Al shows the 2021 monthly mean, maximum and minimum, and annual salinity
for each salinity monitor location; salinity distributions at most locations were the highest in
October, November, and December. Appendix C contains a figure showing Tar River discharge
for 2021, as well as graphs depicting the semi -continuous salinity and depth data from each Aqua
TROLL monitor (Appendices B — I are included only on the flash drive that accompanies this
report). On the Appendix C graphs, salinity data omitted from analysis, or missing data, have
been categorized as one of the following: insufficient water, equipment malfunction, service error,
or other.
1.0 Environmental Variables
Salinity of coastal streams can be affected by a variety of biotic and abiotic factors. This section
will determine how salinity within the monitored creeks was affected by four environmental
variables: Tar River discharge, water depth, rainfall, and wind (Tar River discharge data were
obtained from USGS gauge station 02084000 and wind data were supplied by New Bern KEWN
Station).
a. Salinity and Tar River Discharge
Because the Tar River carries mostly freshwater, it is expected that
increases in discharge should result in decreases in salinity at all monitored PCS creeks (i.e., they
should be negatively correlated). Figure III -Al shows daily Tar River discharge from 1998 to 2021
(with the exception of 2006 when no creeks were monitored per the 1998 plan) and Figure III-A2
shows discharge at impact creeks during pre- and post -Mod Alt L periods. Tar River discharge
in 2021 was slightly below the average across all sample years.
As in last year's report, relationships between salinity and Tar River
discharge were analyzed using a cross -correlation function which incorporated daily time lags.
For example, correlations were computed between salinity on one day and the discharge of Tar
River one day prior, two days prior, three days prior, and so on. Discharge and salinity data were
log -transformed prior to analyses. Table III-A2 shows the time lag that yielded the strongest
negative correlation between discharge and salinity for each salinity station, as well as the value
of Pearson's r, the correlation coefficient used in the analysis (Pearson's r ranges from -1 to 1,
where -1 indicates a strong, negative relationship, 0 indicates no relationship, and +1 indicates a
strong, positive relationship). All Aqua TROLLs showed moderate to strong negative correlations
between salinity and Tar River discharge, ranging from -0.443 (BSCS1) to -0.648 (SC1 S3). HS1
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and HS2 represented the only stations without significant correlations. Regarding Tar River
discharge, all Aqua TROLLs had their most significant time lag occur between zero and seven
days.
Salinity/discharge correlations for impact creeks were similar to those for
control creeks, suggesting that mine activities have not altered how salinity in these creeks
responds to changes in Tar River discharge.
b. Salinity and Water Depth
Water depths for 2021 at each salinity station are displayed in the figures
presented in Appendix C. Because both the depth and salinity measurements are taken from the
Aqua TROLL or are both manually measured, no time lag is expected between these two
variables. Thus, a simple correlation between the daily means of salinity and depth was
conducted.
There were 12 stations out of 31 that displayed a significant negative
correlation between water depth and salinity, ranging from -0.125 (BSCS1) to -0.491 (SC1S2)
(Table III-A2). The seven significantly positive relationships ranged from +0.146 (DWS1) to
+0.442 (DKCS2) (Table III-A2). Since 2015, while many correlations have been significant
statistically, the relationship between salinity and water depth was mostly weak to intermediate
with a range of significant correlations from —0.61 (DWS2 2018) to +0.67 (DWS1 2017).
There does not appear to be any difference between impact and control
creeks in how salinity correlated with water depth.
c. Salinity and Rainfall
Rainfall is summarized in Section I-F (Figure I-F1, Table I-F1, and Table I-
F2). Figure III-A3 shows yearly rainfall at all impact creeks with pre- and post -Mod Alt L data.
Rainfall is expected to decrease salinity, as the rain introduces freshwater into the creeks. There
may also be some temporal lag in the relationship between rainfall and salinity, as it would take
time for precipitation on land to filter into the creeks and to the monitor locations. Thus, cross -
correlation functions were conducted between daily mean rainfall and daily mean salinity at each
salinity station, rainfall data were obtained from the nearest installed rain gauge to each station.
There were 25 out of 31 salinity stations that showed weak, significant
negative correlations between salinity and rainfall in 2021 (Table III-A2). Significant correlations
ranged from -0.131 (TS2) to -0.321 (LCS2). Significant time lags for salinity/rainfall relationships
ranged from one day to seven days.
The salinity in both impact and control creeks seems to have responded
similarly to changes in rainfall, both in terms of strength of the relationship as well as the time lag
with the strongest response.
d. Salinity and Wind
There are two important components of wind: speed and direction. Salinity
in the Pamlico River increases on a gradient from west to east, and strong easterly and
northeasterly winds are expected to push more saline waters into the PCS creeks study area.
Other factors which interact to some degree include duration of wind event, distance of monitor
from mouth of creek, width of mouth of creek, which side of creek/river the tributary occupies, and
orientation of creek axis relative to larger water body and to the wind. Summary salinity wind rose
graphs for PCS Aurora 6N for 1998 through 2015 were included in the 2015 creeks report, and
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quarterly and annual salinity rose graphs for each Aqua TROLL were included in the 2015-2018
reports. The salinity rose graphs showed some variability in salinity with percent frequency of
counts by wind direction, but also corroborated the following presumed factors:
■ overall predominant wind direction was northeast or southwest
■ salinity at the most upstream stations was less affected than those
closer to mouths of the study creeks
■ salinity variation for the downstream stations was dependent on
orientation of creek to the wind and creek mouth proximity to
Pamlico River, or South Creek, or Durham Creek.
The wind data (direction and speed) were used in the 2021 analysis of
correlation as usual but the salinity rose graphs were not prepared for this report due to the long
term consistent nature of the predominant winds at this locale.
Two sets of correlations were used to quantify the relationship between
wind and salinity at the 31 salinity stations. First, a Pearson's r correlation was found between
daily mean salinity and daily mean wind speed (mph). The results of these correlations are given
in Table III-A2. Correlations were weakly significant for 18 salinity stations, all of which were
negative.
The second set of correlations involved daily mean salinity and daily mean
wind direction. Because wind is a circular variable (i.e., values range from 1 to 360 and the
numerical distance between 360 and 1 is the same as the distance between 1 and 2), vector
averaging (Jammalamadaka and Lund 2006) was used to obtain daily mean wind direction. Then,
the correlation between salinity and wind direction was calculated using Mardia's r statistic
(Mardia 1976, and further described in Jammalamadaka and Lund 2006). This statistic ranges
from 0 to 1, in which 0 indicates no relationship and 1 indicates a strong relationship between the
two variables (Pewsey et al. 2013). Significance of Mardia's r was determined using a
randomization test outlined in Pewsey et al. (2013).
There were 29 salinity stations that exhibited a significant relationship
between daily mean salinity and daily mean wind direction in 2021 (Table III-A2). Mardia's r
correlations ranged from 0.210 (SC1S1) to 0.345 (DKCS2). Since 2015 the majority of the
correlations have been significant, although all have been weak with a range of 0.134 (LOCS2 in
2016) to 0.448 (JBS1 in 2018).
Salinity within the creeks in the PCS study seems to be driven by both
freshwater inputs (e.g., Tar River discharge and rainfall) and saline inputs (e.g., east winds move
more saline water from lower in the Pamlico estuary into the study area). Of these, Tar River
discharge showed the strongest relationships with salinity: salinity decreased with greater Tar
River discharge.
There did not seem to be any apparent effect of mine activities on the
relationships between salinity and the examined environmental variables. Salinity within post -
Mod Alt L creeks (Jacks, Jacobs, Drinkwater, Tooley, Huddles Cut, Porter, and DCUT11) showed
similar relationships with all environmental variables as the control and pre -Mod Alt L periods.
Thus, it does not seem that mine activity has affected how creek salinity is altered by external
environmental factors unrelated to the mine.
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2.0 Interannual and/or Monthly Comparisons
Annual salinity for each salinity station in the eight impact creeks, medians for pre -
and post -Mod Alt L years, and annual salinity for nearby control creeks are shown in boxplots
(Figure III-A4 through Figure III-A10). Figure III -Al 1 through Figure III-A13 display box plots of
monthly salinity at each impact creek salinity station with data combined into pre -Mod Alt L, post -
Mod Alt L, and 2021 year categories. Figure III-A14 and Figure III-A15 display box plots of
monthly salinity at each control creek salinity station for all years combined and for 2021. These
data and figures are discussed in more detail below for each creek.
The majority of the stations in 2021 had a median salinity level that was lower than
in 2020. Exceptions included SCSI , SCS2 and BSCS1. Generally, monthly salinity trends in 2021
saw low salinity ranges during the first half of the year and then saw an increasing trend from July
onward.
a. Broomfield Swamp Creek and SCUT1 (control)
The third year of pre -Mod Alt L salinity and depth data was collected in
2021 from three Aqua TROLLs in Broomfield Swamp Creek at the locations shown in Figure I-B1
and from three Aqua TROLLs in SCUT1 (control) as shown in Figure I-B2. The two creeks are
the most upstream tributaries to South Creek in the study and the Aqua TROLL locations are the
most distant from the Pamlico River in the study. Monthly and annual summary data for 2021 are
shown in Table III -Al . Although less saline, these creeks followed a similar seasonal trend to the
other creeks in 2021 with increased salinity distributions in the second half of the year (Table III-
A1). Salinity in Broomfield Swamp Creek in 2021 ranged from 0.0 to 14.2 and from 0.0 to 13.9 in
SCUT1. Mean salinity in Broomfield Swamp Creek at the three monitors ranged from 2.8 to 3.6
while the SCUT1 mean ranged from 2.0 to 3.8 (Table III-A1). All six stations across both creeks
in the three sample years represented low salinity distributions with little variation between years
(Figure III-A4).
3.0 Pre -/Post- Mod Alt L Comparisons
Two statistical tests were used to determine potential effects of Mod Alt L activities
on impact creeks. Welch's t-tests determined if mean post -Mod Alt L salinity significantly differed
than mean pre -Mod Alt L salinity. Concordance correlations determined if the similarity in salinity
between impact and control creeks significantly differed after Mod -Alt L activities. A concordance
correlation is similar to a normal correlation, but examines the similarity in values between two
variables, instead of the presence of a linear trend (Lin 1989). The concordance correlation
coefficient, rr, ranges from -1 to +1, in which -1 indicates no similarity between the variables and
+1 indicates the two variables are identical. For each impact creek, two concordance correlations
were conducted: one between salinity values of the impact and control creek for all samples taken
in pre -Mod Alt L years (and the corresponding years for the control creek) and one for the post -
Mod Alt L years. If Mod Alt L activities affected salinity, the concordance correlation between
impact and control should be lower for the post -Mod Alt L years than the pre -Mod Alt L years (i.e.,
salinity in the impacted creek should be less similar to the control creek). For some impacted
creeks, multiple control creeks were used.
Salinity measurements for pre- and post -Mod Alt L time periods are reported as
mean ± 1 SD.
a. Jacks Creek
There are two Aqua TROLLs located in Jacks Creek-JS2 approximately
400 feet upstream of the mouth and JS1 approximately 2,475 feet (0.46 mile) upstream of the
mouth where the main channel divides into two narrower channels (Figure I-B3). Monitors were
re -installed 20 July 2011 after CAMA-approved pier construction was completed. The first post-
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Mod Alt L year was 2015. The historic 645-acre drainage basin was reduced over many years to
approximately 317 acres pre -Mod Alt L and then to 150 acres by Mod- Alt L at the end of 2015;
no further Mod -Alt L drainage basin reduction is permitted to occur in Jacks Creek. In preparation
of this report, it was noted that JS1 and JS2 salinity data from several early Jacks Creek years
(2003-2005) had not been included in pre- and post -Mod Alt L analyses for the past several years;
the data gap appears to have occurred when analysis switched from Sigma Plot to R. Archived
raw data were used where retrievable and measures taken from the Appendix C salinity graphs
or the monthly min/max/avg values taken from the tables in the 2003-2005 reports were used for
periods of absent or corrupted archive data.
The JS1 and JS2 Aqua TROLLs showed a pattern of increased yearly
salinity distributions (2000-2002) before distributions decreased in 2003 (Figure III-A5). Salinity
distributions steadily decreased annually from 2011 to 2016 and fluctuated in years after at both
JS1 and JS2 (Figure III-A5). The year 2021 saw near post -Mod Alt L average rainfall and near
post -Mod Alt L median discharge (Figure III -Al and Figure III-A3), and resulting salinity
distributions were slightly below post -Mod Alt L medians at both stations (Figure III-A5). Pre -Mod
Alt L monthly salinity means and medians were generally higher than post -Mod Alt L means and
medians for both Jacks Creek monitors. Monthly salinity means and medians for 2021 were lower
than all post -Mod Alt L values except for October, November and December for both Aqua
TROLLs (Figure III-Al1).
Salinity at Jacks Creek was compared to both SS1 (a nearby control Aqua
TROLL in South Creek with data from 1999) and Little Creek (LCS1 and LCS2), the nearest
control creek with two monitors since 2011 (Figure III-A5). At JS1, pre -Mod Alt L salinity (8.02 ±
4.29 psu) was significantly higher than post -Mod Alt L salinity (6. 39 ± 3.82 psu; P < 0.001). At
SS1, salinity levels were significantly higher during corresponding pre -Mod Alt L years (8.79 ±
4.38 psu) and decreased during post -Mod Alt L years (6.91 ± 3.85 psu; P < 0.001). At LCS1,
salinity during corresponding pre -Mod Alt L years (5.44 ± 4.06 psu) was also significantly higher
than salinity during post -Mod Alt L years (3.04 ± 3.81 psu; P < 0.001).
The concordance correlation analysis between JS1 and SS1 showed that
salinity values were closely associated post -Mod Alt L (pre rr = 0.87 and post rr = 0.96). The
concordance correlation between JS1 and LCS1 showed that salinity values did not differ post -
Mod Alt L (pre rr = -0.16 and post rr = 0.55).
At JS2, pre -Mod Alt L salinity (8.62 ± 3.81 psu) was significantly higher than
post Mod Alt L salinity (6.98 ± 3.88 psu; P < 0.001). Corresponding pre- and post -Mod Alt L
statistics for SS1 are given above. At LCS2, salinity during corresponding pre -Mod Alt L years
(10.18 ± 3.35 psu) was also significantly higher than salinity during post -Mod Alt L (6.91 ± 3.85
psu; P < 0.001).
The concordance correlation analysis between JS2 and SS1 showed that
salinity values were more similar post -Mod Alt L (pre rr = 0.92 and post rr = 0.99); values between
JS2 and LCS2 did not differ post -Mod Alt L (pre rr = -0.26 and post rr = 0.94).
b. South Creek (SS1) (control)
The South Creek Aqua TROLL is located approximately 2,600 feet (0.5
mile) downstream from the mouth of Jacks Creek on the north bank of South Creek (Figure I-B4).
As noted for Jacks Creek, some SS1 salinity data (2004 only in this case) also had been
inadvertently omitted in the recent pre- and post -Mod Alt L analyses; the same approach was
used for SS1 data recovery as was done for Jacks Creek data (raw archived data where possible,
otherwise values from 2004 report Appendix C graphs, or min/max/avg values from 2004 report
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table). Salinity at SS1 was variable from the study years 1999-2002, with an increase in salinity
distributions between 2003 and 2008 and then a decrease in salinity distributions from 2012 to
2016. Salinity distributions fluctuated in the last five years with 2021 representing another
decrease. In 2021, the median salinity at SS1 was below the median for SS1 salinity in matched
Jacks Creek post -Mod Alt L years (Figure III-A5), Jacobs Creek Post Mod Alt L years (Figure III-
A6), Drinkwater post -Mod Alt L years (Figure III-A7), and Tooley post Mod Alt L years (Figure III-
A8). Similarly to most stations at other creeks, SS1 saw increases in salinity distributions in the
second half of the year with lower distributions in the first six months (Figure III-A14).
c. Little Creek (control)
There are two Aqua TROLLs located in Little Creek, which drains into
South Creek from the south and has a large mostly agricultural drainage basin (- 1,822 acres).
The downstream Aqua TROLL, LCS2, is approximately 1,000 feet upstream from the mouth and
LCS1 is approximately 4,800 feet (0.9 mile) upstream from the mouth (Figure I-B5). Aqua
TROLLs were installed 22 June 2011 after CAMA-approved pier construction was completed.
At LCS1, the median for 2021 was slightly lower than the median in 2020
and distributions have remained similar over the last three years, while LCS2 has fluctuated in
salinity distributions since 2014 (Figure III-A5, Figure III-A6, and Figure III-A7). Salinities at both
Aqua TROLLs in 2021 saw similar trends to other creeks, with low distributions in the first half of
the year and an increasing pattern from July onward (Figure III-A14).
d. Jacobs Creek
There are two Aqua TROLLs in Jacobs Creek, which is located on the
northwest side of South Creek. The downstream Aqua TROLL, JCBS2, is approximately 400 feet
upstream from the mouth and JCBS1 is approximately 3,306 feet (0.6 mile) upstream of the mouth
(Figure I-B6). Monitors were installed 20 July 2011 after CAMA-approved pier construction was
completed. The first post -Mod Alt L year was 2014. The historic 751-acre drainage basin was
reduced over many years to approximately 393 acres by the end of 2014; no further drainage
basin reduction from Mod Alt L is permitted in Jacobs Creek.
The salinity distribution, in 2021, at both Aqua TROLLs was below the post -
Mod Alt L median and well below the pre -Mod Alt L median (Figure III-A6) even though 2021
represented a near average year for both rainfall and discharge (Figure III -Al and Figure III-A3).
The two Aqua TROLLs have similar monthly salinity distributions over the years, with JCBS2
distributions usually slightly higher than the more variable upstream JCBS1 (Figure III -Al 1).
Excluding September, all post -Mod Alt L monthly medians were lower than pre -Mod Alt L values
at both Aqua TROLLs.
Jacobs Creek was compared to four nearby control creeks (SS1, PA2,
Little, and Long) to determine potential post -Mod Alt L differences. At JCBS1, pre -Mod Alt L
salinity (11.18 ± 2.84 psu) was significantly higher than post -Mod Alt L salinity (7.20 ± 3.68 psu;
P < 0.001). At all four control creeks, salinity during corresponding pre -Mod Alt L years was also
significantly higher than during corresponding post -Mod Alt L years (SS1 - pre: 11.81 ± 2.30 psu,
post: 6.97 ± 3.69 psu, P < 0 .001; PA2S1 - pre: 12.70 ± 2.11 psu, post: 7.69 ± 3.59 psu, P <
0.001; LCS1 - pre: 6.52 ± 4.10 psu, post: 3.02 ± 3.68 psu, P < 0.001; LOCS1 - pre: 12.76 ± 2.00
psu, post: 7.70 ± 3.70 psu, P < 0.001).
The concordance correlation analysis showed that salinity values between
JCBS1 and the four controls (LCS1, SS1, PA2S1, and LOCS1) were similar to each other
(comparison with LCS1: pre rr = 0.25 and post rr = 0.39; comparison with SS1: pre rr = 0.73 and
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post rc = 0.92; comparison with PA2S1: pre rc = 0.63 and post rc = 0.95; comparison with LOCS1:
pre rr = 0.57 and post rr = 0.92).
At JCBS2, pre -Mod Alt L salinity (12.73 ± 2.27 psu) was also significantly
higher than post -Mod Alt L salinity (7.89 ± 3.60 psu, P < 0.001). At all four control creeks, salinity
during corresponding pre -Mod Alt L years was also significantly higher than salinity during
corresponding post -Mod Alt L years (SS1 and PA2S1 given above; LCS2 — pre: 11.58 ± 2.70,
post: 6.52 ± 3.76 psu, P < 0.001; LOCS2 — pre: 12.91 ± 2.10 psu, post: 7.91 ± 3.64 psu, P <
0.001).
The concordance correlation analysis showed that salinity values between
JCBS2 and all four control creeks did not significantly differ post -Mod Alt L (comparison with
PA2S1: pre rr = 0.95 and post rr = 0.98; comparison with LOCS2: pre rr = 0.95 and post rr = 0.98;
comparison with LCS2: pre rr = 0.74 and post rr = 0.87; comparison with SS1: pre rr = 0.89 and
post rr = 0.95).
e. PA2 (control)
The small man-made creek and marsh PA2 drains into South Creek from
the northwest and has the smallest drainage basin (-22 acres) in the study. One Aqua TROLL
(PA2S1) is located near the middle of PA2, approximately 800 feet from the mouth; there is no
downstream salinity monitor in PA2 itself, but the downstream salinity monitor for Drinkwater
Creek is within 200 feet of the mouth of PA2 and is used for comparison/analysis (Figure I-B7).
The PA2 monitor was installed 13 July 2011 after CAMA-approved pier construction was
completed.
Salinity at this location followed similar pattern to that shown in South
Creek, Little Creek downstream, and Long Creek. The median salinity in 2021 was lower than
the median for matching post -years in Jacks, Jacobs and Drinkwater creeks. Like many of the
creeks in the study, the salinity distribution in 2016 at PA2S1 was the lowest in the study years
thus far (Figure III-A5, or Figure III-A6); in 2016, Tar River discharge was slightly above the mean
(Figure III-A1) and rainfall was slightly above the mean (Figure III-A3 and Table I-F2). Salinity
distributions in 2021 were similar to those at the downstream salinity monitor for Drinkwater Creek
(DWS2) as would be expected due to proximity. In 2021, like in most other creeks, salinity
distributions were the highest in October, November and December (Figure III-A15; Table III -Al ).
f. Drinkwater Creek
There are two Aqua TROLLs located in Drinkwater Creek, which is also on
the northwest side of South Creek. The downstream Aqua TROLL, DWS2, is located
approximately 400 feet upstream from the mouth and DWS1 is located approximately 3,520 feet
(0.7 mile) upstream from the mouth and just upstream of the out -of -use railroad crossing of the
creek (Figure I-B8). Monitors were installed 30 June 2011 after CAMA-approved pier construction
was completed. The first year of post -Mod Alt L data was 2013. The historic 605-acre drainage
basin was reduced over many years to approximately 152 acres by the end of 2014 and no further
basin reduction from Mod Alt L is permitted.
For all years, the downstream Aqua TROLL has had higher salinity
distributions than the upstream Aqua TROLL by about 2-3 psu (Figure III-A7). In 2021, median
salinity values represented the lowest for the upstream and second lowest for the downstream
Aqua TROLL throughout all sample years.
Drinkwater Creek was compared to four nearby control creeks (South
Creek, PA2, Little, and Long) to determine potential post -Mod Alt L differences. At DWS1, pre-
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Mod Alt L salinity (10.40 ± 3.66 psu) was significantly higher than post -Mod Alt L salinity (6.39 ±
3.89 psu, P < 0.001). At all four control creeks, salinity during corresponding pre -Mod Alt L years
was also significantly higher than salinity during corresponding post -Mod Alt L years (SS1 - pre:
12.01 ± 2.51 psu, post: 7.45 ± 3.79 psu, P < 0 .001; PA2S1 - pre: 13.14 ± 2.38 psu, post: 8.18 ±
3.68 psu, P < 0.001; LCS1 - pre: 7.58 ± 4.14 psu, post: 3.25 ± 3.76 psu, P < 0.001; LOCS1 - pre:
13.28 ± 2.12 psu, post: 8.19 ± 3.78 psu, P < 0.001).
The concordance correlation analysis showed that salinity values at DWS1
was similar to the four controls (SS1, PA2S1, LCS1, and LOCS1) (comparison with SS1: pre rr =
0.55 and post rr = 0.85; comparison with PA2S1: pre rr = 0.43 and post rr = 0.79; comparison with
LCS1: pre rr = 0.59 and post rr = 0.56; comparison with LOCS1: pre rr = 0.35 and post rr = 0.79).
At DWS2, pre -Mod Alt L salinity (13.22 ± 2.42 psu) was significantly higher
than post -Mod Alt L salinity (8.31 ± 3.74 psu, P < 0.001). At all four control creeks, salinity during
corresponding pre -Mod Alt L years was also significantly higher than salinity during corresponding
post -Mod Alt L years (SS1 and PA2S1 given above; LCS2 - pre: 12.21 ± 2.84, post: 6.97 ± 3.86
psu, P < 0.001; LOCS2 - pre: 13.38 ± 2.34 psu, post: 8.39 ± 3.72 psu, P < 0.001).
The concordance correlation analysis showed that post -Mod Alt L salinity
values between DWS2 and all four control creeks did not significantly differ (comparison with
PA2S1: pre rr = 0.96 and post rr = 0.99; comparision with LCS2: pre rr = 0.82 and post rr = 0.86;
comparison with LOCS2: pre rr = 0.96 and post rr = 0.98; comparison with SS1: pre rr = 0.90 and
post rr = 0.94).
g. Long Creek (control)
There are two Aqua TROLLs located in Long Creek, which is on the
southeast side of South Creek opposite Tooley Creek. The downstream Aqua TROLL, LOCS2,
is approximately 500 feet upstream from the mouth and LOCS1 is approximately 2,000 feet (0.4
mile) upstream from the mouth (Figure I-B9). The historic -630-acre basin of Long Creek was
reduced decades ago to -223 acres by previous mine reclamation activities. Units were installed
13 July 2011 after CAMA-approved pier construction was completed.
Salinity distributions in Long Creek at the two monitors have followed
similar patterns over their sample years (Figures III-A6, III-A7, or III-A8). Salinity distributions at
both Aqua TROLLs have fluctuated since 2016 (Figures III-A5, III-A6, or III-A7). In 2021, at both
Aqua TROLLs, distributions were the lowest earlier in the year and the highest in October,
November and December (Figure III-A14, Table III-A1).
h. Tooley Creek
There are two Aqua TROLLs located in Tooley Creek, which is on the
northwest side of South Creek, close to where South Creek joins Pamlico River. The downstream
Aqua TROLL, TS2, is approximately 336 feet upstream of the mouth and TS1 is approximately
2,468 feet (0.46 mile) upstream of the mouth (Figure I-B10). Monitors were re -installed in 2010
and the first year of post -Mod Alt L data was 2012. Mod -Alt L mine activities in the Tooley Creek
drainage basin, most of which occurred in 2012, reduced the basin to approximately 257 acres
from the approximately 571-acre pre -Mod Alt L basin. Mod -Alt L activities in Tooley Creek were
completed by the end of 2013 and no further basin reductions are permitted.
The two Aqua TROLLs have had similar salinity distributions since 1999;
both fluctuating alongside yearly discharge and rainfall (Figure III -Al and Figure III-A3). For both
Tooley Creek Aqua TROLLs, the 2021 salinity distribution was lower than both the pre- and the
post -Mod Alt L monthly values in the first eight months of the year, while September -December
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saw distributions higher than both pre- and post -Mod Alt L years (Figure III-Al2). The salinity
distribution for 2021 was nearly the same at both stations and both were below the post -Mod Alt
L median (Table III -Al and Figure III-A8).
To determine potential post -Mod Alt L differences, Tooley Creek was
compared to one control creek monitor (SS1; Long Creek is a control creek closer to Tooley but
only has data from 2011 forward and therefore includes only one Tooley Creek pre -Mod Alt L
year). At TS1, pre -Mod Alt L salinity (9.53 ± 3.48 psu) was significantly higher than post -Mod Alt
L salinity (8.84 ± 3.61 psu; P < 0.001). At SS1, salinity during corresponding pre -Mod Alt L years
(10.16 ± 4.36 psu) was also significantly higher than salinity during corresponding post -Mod Alt L
years (7.95 ± 3.96 psu; P = < 0.001).
The concordance correlation analysis between TS1 and SS1 showed that
salinity values were more similar post -Mod Alt L (pre rr = 0.87 and post rr = 0.90).
At TS2, pre -Mod Alt L salinity (10.25 ± 3.47 psu) was significantly higher
than post -Mod Alt L salinity (9.08 ± 3.84 psu; P < 0.001). Corresponding pre- and post -Mod Alt L
statistics for SS1 are given above.
The concordance correlation analysis between TS2 and SS1 showed that
salinity values were more similar post -Mod Alt L (pre rr = 0.84 and post rr = 0.92).
i. Pamlico River (PS1) (control)
The Pamlico River Aqua TROLL is located on the south shore of the river
more or less equidistant (approximately 1.7 miles) between the mouths of Huddles Cut and South
Creek (Figure I-B12). Salinity distributions at PS1 declined every year from 2012-2016, and the
median salinity in 2016 was half as much as in 2012; the 2018 salinity distribution was similar to
2001, 2007, and 2017. Due to damage from Hurricane Florence to the infrastructure to which the
Aqua TROLL was mounted, there were no salinity data for PS1 from mid -September 2018 through
entire 2019. Once reinstalled in 2020, the salinity distribution was near the post -Mod Alt L median
in 2020 then decreased below it in 2021 (Figure III-A9).
j. Huddles Cut
Due to the removal of the HS1 and HS2 Aqua TROLLS, there is now one
Aqua TROLL located in Huddles Cut, which is on the south side of Pamlico River. The
downstream Aqua TROLL, HS3, is at the mouth just upstream of the bridge across SR306 at the
Bayview-Aurora ferry landing. HS1, a site that is now measured twice a month, is approximately
3,020 feet (0.6 mile) upstream of the mouth on the main prong, and HS2, another site measured
bi-monthly, is approximately 1,800 feet (0.3 mile) upstream of the mouth on the west prong (Figure
I-B13). Direct mine impacts to the Huddles Cut watershed ended in 2011 and approximately 289
acres remain out of the approximately 552-acre pre -Mod Alt L basin. No further reductions are
permitted.
Salinity distributions at HS3 have been higher than either HS1 or HS2 for
almost every year, except 2015 when HS2 had a slightly higher distribution (Figure III-A9). Like
most other stations, all three sites saw below post -Mod Alt L median distributions in 2021 (Figure
III-A9). HS1 and HS2 represented the only two stations where post -Mod Alt L median salinity was
higher than pre -Mod Alt L, all three monitors recorded the highest salinity distributions in the last
four months of the year (Figure III-A13 and Table III -Al).
To determine potential Mod Alt L differences, Huddles Cut was compared
to the Pamlico River monitor (PS1) for all years and the Duck Creek monitors (DKCS1 and
III-A-9

DKCS2) only for the years 2011-2021 (Figure III-A9). PS1 has been monitored since 1999, almost
the same amount of years as Huddles; however, PS1 was not monitored during the year of 2019
due to infrastructure damage from Hurricane Florence. There were no pre -Mod Alt L monitoring
years coinciding with Huddles Cut from Duck Creek so these monitors were used to reference
patterns in upstream and downstream Huddles monitors from 2011-2021. Both sets of upstream
and downstream monitors from Duck Creek and Huddles Cut followed a similar but not identical
fluctuating trend throughout matching sample years (Figure III-A9). At HS1, pre -Mod Alt L salinity
(4.89 ± 3.43 psu) was significantly lower than post -Mod Alt L salinity (6.31 ± 3.60 psu; P < 0.001).
At PS1, salinity was significantly higher during corresponding pre -Mod Alt L years (11.39 ± 6.17
psu) and decreased by 19 percent during post -Mod Alt L years (9.24 ± 3.92 psu; P < 0.001).
The concordance correlation analysis between HS1 and PS1 showed that
salinity values were more similar post -Mod Alt L (pre rr = 0.05 and post rr = 0.50).
At HS2, pre -Mod Alt L salinity (4.87 ± 3.63 psu) was significantly lower than
post -Mod Alt L salinity (6.57 ± 3.48 psu; P < 0.001). Corresponding pre- and post -Mod Alt L
statistics for PS1 are given above.
Like HS1, the concordance correlation analysis between HS2 and PS1
showed that salinity values were more similar post -Mod Alt L (pre rr = 0.07 and post rr = 0.52).
At HS3, pre -Mod Alt L salinity (8.62 ± 4.47 psu) was significantly higher
than post -Mod Alt L salinity (8.07 ± 3.84 psu; P = 0.001). Corresponding pre- and post -Mod Alt L
statistics for PS1 are given above.
The concordance correlation analysis between HS3 and PS1 showed that
salinity values were more similar post -Mod Alt L (pre rr = 0.36 and post rr = 0.90).
k. Porter Creek
There are two Aqua TROLLs located in Porter Creek, which is on the south
side of Pamlico River upstream from Aurora and the PCS main facility. The downstream Aqua
TROLL, PCS2, is approximately 2,377 feet (0.45 mile) upstream from the mouth, at the outer
edge of a broad expanse of the creek and PCS1 is approximately 8,600 feet (1.6 miles) upstream
from the mouth in the middle of a narrow, deep channel (Figure I-B14). Monitors were installed
19 and 27 July 2011. The first year of post -Mod Alt L data was 2016. The estimated historic
3,745-acre drainage basin was reduced to approximately 1,154 acres by the end of 2016
(reductions include all mine activities, not only Mod Alt L). In 2017, the 1,154-acre Porter Creek
drainage basin was reduced by an additional 314 acres to roughly 840 acres; no additional
reduction is permitted.
While overall behavior was the same, the salinity distribution at PCS2 was
higher than PCS1 every year. Both Aqua TROLLs experienced a steady decline in their
distributions from 2011-2015, then fluctuated in the years after (Figure III-A10). The year 2020
represented the first increase in median yearly salinity since 2017 and was above the post -Mod
Alt L median but was followed by another decline in 2021 (Figure III-A10). In 2021, like other
creeks, PCS1 and PCS2 showed the highest salinity distributions from July onwards, while the
first half of the year saw lower values (Figure III-A13 and Table III -Al).
Salinity at Porter Creek was compared to nearby control Aqua TROLLs,
one in Durham Creek (DCS1), one in a small tributary DCUT19 (DC19S1), and two in Duck Creek
(DKCS1 and DKCS2), a control creek across the Pamlico River. At PCS1, pre -Mod Alt L salinity
(6.28 ± 4.06 psu) was significantly higher than post -Mod Alt L salinity (5.52 ± 4.01 psu; P < 0.001).
III-A-10

At DC19S1, salinity during corresponding pre -Mod Alt L years (6.34 ± 3.28 psu) was significantly
higher than salinity during corresponding post -Mod Alt L years (6.02 ± 4.09 psu; P = 0.061). At
DKCS1, salinity during corresponding pre -Mod Alt L years (5.48 ± 4.25 psu) was significantly
higher than salinity during corresponding post -Mod Alt L years (3.69 ± 4.30 psu; P < 0.001).
The concordance correlation analysis between PCS1 and DC19S1 showed
that salinity values were more closely associated post -Mod Alt L (pre rr = 0.75 and post rr = 0.95).
This was not the case between PCS1 and DKCS1, which showed that salinity values were
statistically more similar post -Mod Alt L (pre rr = 0.70 and post rr = 0.74).
At PCS2, pre -Mod Alt L salinity (8.06 ± 3.73 psu) was significantly higher
than post -Mod Alt I salinity (6.38 ± 3.99 psu; P < 0.001). At DCS1, salinity during corresponding
pre -Mod Alt L years (6.39 ± 3.24 psu) was also significantly higher than salinity during post -Mod
Alt L years (5.93 ± 4.12 psu; P = < 0.001). At DKCS2, salinity during corresponding pre -Mod Alt
L years (8.02 ± 4.25 psu) was also significantly higher than salinity during post -Mod Alt L years
(5.79 ± 4.23 psu; P < 0.001).
The concordance correlation analysis between PCS2 and DCS1 showed
that salinity values were more closely associated post -Mod Alt L (pre rr = 0.95 and post rr = 0.97).
The concordance correlation between PCS2 and DKCS2 showed that salinity values did not
statistically differ post -Mod Alt L (pre rr = 0.71 and post rr = 0.90).
I. Durham Creek DCS1 (control), DCUT11, and DCUT19 (control)
In 2013, three Aqua TROLLs were installed in Durham Creek basin, one
approximately 13,717 feet (2.6 miles) upstream of the mouth of Durham Creek (DCS1, a control,
Figure I-B15), one in an unnamed tributary to Durham Creek on its east side, approximately 365
feet upstream from where it drains into Durham Creek, DCUT11 (DC11S1 Figure I-B16), and
one in a second unnamed tributary to Durham Creek on its west side approximately 341 feet
upstream from where it drains into Durham Creek, DCUT19 (DC19S1, a control, Figure I-B17).
Durham Creek drains into the south side of Pamlico River. The entire Durham Creek drainage
basin totals 31,051 acres and encompasses three of the study creeks: Porter Creek (2,728 acres),
DCUT11 (166 acres), and DCUT19 (119 acres). The first post -Mod Alt L year for DCUT11 was
2018 when 84.50 acres were removed from the basin; no further impacts to DCUT11 are
permitted.
All three Aqua TROLLs had very similar salinity distributions in 2021 as well
as in the other years with a few slight exceptions (Figure III -Al 0). Salinity distributions at all three
Aqua TROLLs decreased since 2013, particularly between 2013 and 2014, until a rise in 2017
followed by fluctuation in years after (Figure III-A10). In 2021, salinity distributions at DC11S1,
DCS1 and DC19S1 all followed the same trend as most other creeks with low salinity in the first
half of the year, then increasing July onward and reaching a peak in December (Figure III-A13,
Figure III-A15 and Table III-A1).
Salinity at DC11S1 was compared to two nearby control Aqua TROLLs,
DCS1 and DC19S1. At DC11S1, pre -Mod Alt L salinity (5.22 ± 3.59 psu) was not significantly
different than post -Mod Alt L salinity (5.37 ± 4.30 psu; P = 0.265). At DC19S1, salinity during
corresponding pre -Mod Alt L years (5.97 ± 3.49 psu) was not significantly different than salinity
during corresponding post -Mod Alt L years (6.20 ± 4.22 psu; P = 0.154). At DCS1, salinity during
corresponding pre -Mod Alt L years (6.06 ± 3.43 psu) was significantly higher than salinity during
post -Mod Alt L years (6.11 ± 4.34 psu; P = < 0.001).
III-A-11

The concordance correlation analysis between DC11S1 and DCS1
showed that salinity values were equivalent pre- and post -Mod Alt L (pre rr = 0.94 and post rr =
0.94). The concordance correlation between DC11S1 and DC19S1 showed that salinity values
were as similar in post -Mod Alt L years as they were in pre -Mod Alt L (pre rr = 0.90 and post rr =
0.92).
m. Duck Creek (control)
There are two Aqua TROLLs in Duck Creek, a tributary to Pamlico River
with a confluence on the north side west of the town of Bath. The downstream Aqua TROLL,
DKS2, is approximately 1,400 feet (0.27 mile) upstream from the mouth and DKS1 is
approximately 7,780 feet (1.5 miles) upstream from the mouth (Figure I-B18). Much of the - 3,118
acre drainage basin is either in agriculture or silviculture. Aqua TROLLs were installed 26 July
2011 after the CAMA-approved pier construction was completed.
Salinity distributions declined since 2011 at DKCS1 and since 2012 at
DKCS2 until 2017 when salinity increased at both Aqua TROLLs, and has fluctuated in years
since (Figure III-A9 or III -Al 0). With the exception of 2011, when it was slightly higher, median
salinity at DKCS1 was always lower than at DKCS2; in most years it was 2-4 psu lower. In 2021,
the salinity median at both Aqua TROLLs were well below the median of the 11 sample years
(Figure III-A9 and III-A10).
4.0 Summary and Conclusions
Salinity steadily declined in the Pamlico River and tributaries from 2011-2016 (or
2012-2016 for some creeks) until a rise in salinity in 2017, and then fluctuated in years after. This
short-term trend has been observed at every Aqua TROLL regardless of location (upstream or
downstream), creek basin (within South, Durham, Porter, or Duck creeks or Pamlico River
drainages), creek type (impact or control), or size of drainage basin. In 2021, every Aqua TROLL
saw a decrease in salinity levels from 2020, except for SCSI , SCS2 and BSCS1.
Correlations with environmental factors showed that salinity was most strongly
associated with Tar River discharge; each Aqua TROLL showed a moderate to strong negative
correlation between salinity and discharge. Water depth had weak positive correlations in seven
of the 31 salinity stations and 12 weak negative correlations. Rainfall, and wind speed and wind
direction were only weakly correlated with salinity; 26 of 31 stations had a significant negative
correlation with rainfall, 18 had a significant negative correlation with wind speed, and 29 of 31
stations had a significant relationship with wind direction. Thus, salinity within the study creeks
declined mostly with increased Tar River discharge and, to a lesser extent, increased rainfall and
decreased wind speed, while east and northeast wind and decreased water depths tended to
increase salinity. Tar River discharge has fluctuated throughout sample years with 2020
representing one of the highest years recorded (Figure III -Al ). Total rainfall for across all sample
years has also seen fluctuations, with 2020 representing the highest total ever recorded for almost
every creek (Figure III-A3).
Since annual salinity distributions declined at all creeks for roughly five years until
all creeks increased in 2017 followed by fluctuating levels in years after, there is little evidence to
suggest that Mod Alt L activities have impacted creek salinity. Instead, salinity seems to be more
influenced by regional and climatic factors such as Tar River discharge, precipitation, and wind.
These large-scale factors, as well as others such as drought (which is a function of precipitation),
are known to be important determinants of the salinity of the Tar/Pamlico estuary (Stanley and
Nixon 1992, Kimmel 2016).
III-A-12

Because salinity has decreased in every Aqua TROLL since 2011 or 2012 with a
respectively high salinity year only in 2017 and 2020, it is not surprising that the creeks recently
impacted by Mod Alt L activity (Jacks, Drinkwater, Jacobs, Porter, and Tooley) had lower salinities
during post -Mod Alt L than pre -Mod Alt L. The control creeks for those five impact creeks also
showed the same pattern in their corresponding pre- and post -Mod Alt L years.
The concordance correlations showed that the similarity in salinity between impact
and control creeks was not greatly affected by Mod Alt L activities. If Mod Alt L activities did affect
salinity, it would be expected that salinity in impact and control creeks would become less similar
after a creek is considered post -Mod Alt L; however, salinity at most of the Aqua TROLLs in impact
creeks became more similar to salinity in control creeks after Mod Alt L activities. For those Aqua
TROLLs that became less similar, the concordance correlations were still very high and
significantly greater than zero, indicators of a sustained, close resemblance to the control creeks.
Therefore, the similar salinities observed at all salinity stations regardless of mine
impact, the t-tests which showed significant declines in salinity at most impact and control creeks,
and the concordance correlations which showed that salinity between impact and control creeks
was similar even post -Mod Alt L, all suggest that mine activities have had little impact on study
creek salinity.
III-A-13

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III-A-15

Total Annual Rainfall (in)
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Total Annual Rainfall (in)
Total Annual Rainfall (in)
- Pre
- Post
Jacks
i i i
1999 2001 2003 2005 2013 2015 2017 2019 2021 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Drinkwater
Jacobs
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2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Figure III-A3. Total annual rainfall at four long-term rain gauges over the years of the PCS creeks
study (early years used the PCS NOAA Station Aurora 6N for all creeks; rain gauges in each
creek were installed in 2011; Jacks, Drinkwater, and Jacobs creeks share the PA2 rain gauge;
Porter and DCUT11 share a rain gauge). If a particular site was missing data, data from the
closest rain gauge was used (including Aurora 6N). Black line is mean pre -Mod Alt L total annual
rainfall, violet is mean post -Mod Alt L total annual rainfall.
III-A-16

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Figure III-A4. Salinity boxplots for Broomfield Swamp Creek stations (BSCS1, BSCS2 and
BSCS3) compared to SCUT1 stations (SCSI , SCS2, and SCS3) on annual basis with all
years representing Broomfield Swamp Creek pre -Mod Alt L years. Solid lines indicate median
salinity for pre -Mod Alt L years (black). (Dots=5t"/95t" outliers, upper/lower whiskers=90th/10th
percentiles, upper/lower box edges=75t"/25th percentiles, solid line in boxes=median).
III-A-17

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III-A-18

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Figure III-A6. Salinity box plots for Jacobs Creek stations compared to Long Creek, Little Creek,
South Creek, and PA2 stations on annual basis with control creek data arranged to match pre- and
post -Mod Alt L years for Jacobs Creek. Solid lines indicate median salinity for pre -Mod Alt L years
(black) and post -Mod Alt L years (violet). NOTE: SS1 graph includes years when Jacobs Creek
was not monitored. (Dots=5th/95th outliers, upper/lower whiskers=90th/10th percentiles, upper/lower
box edges=75th/25th percentiles, solid line in boxes=median).
III-A-19

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Figure III-A7. Salinity box plots for Drinkwater Creek stations compared to Long Creek, Little
Creek, South Creek, and PA2 stations on annual basis with control creek data arranged to
match pre- and post -Mod Alt L years for Drinkwater Creek. Solid lines indicate median salinity
for pre -Mod Alt L years (black) and post -Mod Alt L years (violet). NOTE: SS1 graph includes
years when Drinkwater Creek was not monitored. (Dots=5t"/95t" outliers, upper/lower
whiskers=90t"/10t" percentiles, upper/lower box edges=75t"/25t" percentiles, solid line in
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III-A-20

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1 1 1 1
2011 2013 2015 2017 2019 2021
1 1 1 1 1 1 1 1 1 I
2011 2013 2015 2017 2019 2021
DC11S1
▪ T
1
En
07
0
fi
DKCS1
h
T 4
I T I
I _
_ 1 1 1
DC19S1
—
y y t
2011 2013 2015 2017 2019 2021 2013 2015 2017 2019 2021
1 1 1 1 1 1 1 1
2011 2013 2015 2017 2019 2021
DC19S1
—r
T * i
2013 2015 2017 2019 2021 2013 2015 2017 2019 2021
o _
a7
DCS1
i
I I I I I I I I
2013 2015 2017 2019 2021
Figure III-A10. Salinity boxplots for Porter Creek stations (PCS1 and PCS2) and
the DCUT11 station (DC11 S1) compared to Durham Creek stations (DC19S1 and
DCS1 for DCUT11) and Duck Creek stations (DKCS1 and DKCS2 for Porter
Creek) on annual basis with control creek data arranged to match pre- and post -
Mod Alt L years. Solid lines indicate median salinity for pre -Mod Alt L years (black)
and post -Mod Alt L years (violet). (Dots=5th/95th outliers, upper/lower
whiskers=90th/10th percentiles, upper/lower box edges=75th/25th percentiles, solid
line in boxes=median).
III -A-23

Salinity (PSU)
Salinity (PSU)
N
O
N
Jacks Creek - JS1
Jacobs Creek - JCBS1
In —
▪ -
O —
Jan
I T
I L
I
1 1
Feb
T,
Mar
Apr
T
T
I I
el
I
1
May
8
0 I
l
0 I
o
0
June
8
July
v
0 0
0
I
Aug Sep
T
11
1
Oct
0
Nov
i
0
Dec
T
T
I
, Z
6
Drinkwater Creek - DWS1
Jan
In
N
O
▪ -
0 -
Feb
T
Mar
O
Apr
T,
T �.
May
T
I �
0 1
June
T
T I
T
s
I
July
T
1
T
0
1
•
Aug
0
1
Sep
Oct
0
Nov
T
I ,
Dec
Salinity (PSU)
Salinity (PSU)
Jacks Creek - JS2
Jacobs Creek - JCBS2
co
u )
N
• -
0
I(] —
O —
0
N
lf)
Jan
Feb
T
I
I I
1
1
1 1
Mar
1 Z
Apr
Ti
1
41.
May
T
T
g
1 T
June
July
Aug
Sep
T
1I
Oct
T T
8 I T
1
1
Nov
Dec
Drinkwater Creek - DWS2
O —
Jan
Feb
Mar
M T
1
Apr
T
May
111 T
I
I
o
I
1
June
July
P
I
* 1
i
Aug
T
T
1
4
8
Sep
T
II
Oct
Nov
TT T
Dec
Figure III-Al1. Monthly salinities at non -control Aqua TROLLs: Jacks Creek, Jacobs Creek, and Drinkwater Creek. (Dots=5t"/95t" outliers, upper/lower whiskers=90t"/10t" percentiles, upper/lower box
edges=75t"/25t" percentiles, solid line in boxes=median).
III-A-24

Tooley Creek - TSI
Salinity (PSU)
Tooley Creek - TS2
Salinity (PSU)
Figure III-Al2. Monthly salinities at non -control Aqua TROLLs: Tooley Creek.
(Dots=5tt'/95th outliers, upper/lower whiskers=90t"/10t" percentiles, upper/lower box
edges=75th/25th percentiles, solid line in boxes=median, dotted line=mean).
III-A-25

Salinity (PSU)
Salinity (PSU)
Huddles Cut - HS1
Jan
POST
2021
T
—
1
MN
8
O
Feb
T
93
Mar
Apr
I
1 1
May
I I
I I
1 1
June
i
11
I I
I I
1 i
July
9
T I I
1 1 11
Aug
-
Sep
Oct
a
8
1
Nov
T
Dec
1
Huddles Cut - HS2
O _
N
Jan
CD
L{J
—
Feb
8
T
T
a
T
1
Mar
ILJ
Apr
T
May
T
1
I I
I I
I I
I I
1 1
8
June
T
a
1
Aug
I
I
I
1
T
Sep
Oct
1-
I 1
I
1 1
Nov
T
re
Ili
I
I I
I I
J. 1
a
T
Dec
Huddles Cut - HS3
Salinity (PSU)
Porter Creek - PCS1
Cs!
0
• -
m
N
-
Jan
T
T
T ,
1 1 1
T
Feb
1
0
10
T
1
Mar
T
Apr
May
1)�an
1 J.
June
T
1
T 1
J.
T
1
July
T T
T
I 1 1
1 1
1 1
T
Aug
Sep
Oct
T
rt
T
1 T
III
I I
1
T
1
Nov
Dec
Ia
1
Porter Creek - PCS2
0 —
LO
T
Jan
T
li
Feb
T
Mar
Apr
i
7�
1 4.
T
May
O
June
July
0
0
T O T
I O I
0
I I
"
T ri T
T'I
Aug
0
8
Sep
Oct
Nov
Dec
DCUT11 - DC1151
LC) —
O
Jan
T
T
Feb
Mar
Apr
May
T
TIT
1
T
June
O
T
1
1
4.
July
8
s8
O
1
1
1
Aug
0
T
Sep
00
0
0
T
I I
I I
�I
I ■
I
1
Oct
T
0
1
Nov
T
1
1
Dec
Figure III-A13. Monthly salinities at non -control Aqua TROLLs and two YSI stations: Huddles Cut, Porter Creek, and DCUT11 (DC11S1) (Dots=5tn/95th outliers, upper/lower whiskers=90th/10tn
percentiles, upper/lower box edges=75t"/25t" percentiles, solid line in boxes=median).
III-A-26

Little Creek - LCS1
South Creek - SS1
Long Creek - LOCS1
Little Creek - LCS2
PA2 - PA2 S 1
Long Creek - LOCS2
Figure III-A14. Monthly salinities at control Aqua TROLLs: Little Creek, PA2, Long Creek, and South Creek (SS1) (Dots=5t"&95t" outliers, upper/lower whiskers=90t"&10t" percentiles,
upper/lower box edges=75th&25th percentiles, solid line in boxes=median).
III-A-27

M
Duck Creek - DKCS1
Durham Creek - DCS1
-
Jan
T
1
T
Feb
1
Mar
T
1
Apr
1
May
T
T
June
I
I 1
July
1-
IME
Aug
Sep
Oct
7-
-1_ 1;1
Nov
T
I
1
Dec
T
Pamlico River - PS1
U)
Duck Creek - DKCS2
DCUT19 - DC19S1
Jan
Feb
Mar
Apr
T
1
4.
May
June
4
T
July
Aug
Sep
1-
Oct
0
T
1
Nov
T
Dec
Figure III-A15. Monthly salinities at control Aqua TROLLs: Duck Creek, Durham Creek, DCUT19, and Pamlico River (PS1) (Dots=5t"&95t" outliers, upper/lower whiskers=90t"&10t" percentiles,
upper/lower box edges=75t"&25t" percentiles, solid line in boxes=median).
III-A-28

N N a O O
UU w �00
Q>.2 �L
u)
O 2 U a)
0) s= -
N "-
- Q O 0
0_ -c(i)3 Q
O 0) = N a)
coo c -0 -o
N (B
(B N N N
i N a) O
o U : L
L _
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.-: c
0) 0 0 (B
co E
NU.c
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a) co a)
ou,
0
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2 JUY ("_n
E a) a)co U
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C U a) L
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—
E N In
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ai E
O
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a)
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H CO H o
N
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0
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U
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7
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CO 00 V V
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c
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w
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CO
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0 0 o v
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c
co x
a) c .c
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rn
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co O LO
LO I� T
CO O T CA
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N I� - N
T T 0
T (O T 00
N V O
N LO N V
(0 I� O
c
co x
a) ( .c
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CO (g)
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LriovO
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v co � v
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III-A-29

(V
O
N
U
N
O
Z
V
0
Q
N
u)
aI
A
2
N
LL
Table III -Al (continued).
N N 60)
• O N-
Ln
LC) d"
O
O 6) (O 0
O O V
• O 0
O a0 V
co co O
Ln a0 N V
co co O 0)
N V O
O N- CO 0
N N V
co N V co
N O V
V N co
N V O
V CO CO 0
C) O O V
C
N (( .c
EEEc
cn
cn
00 V O (r)
4
N N
N cO6j co
Ln 00 V co
00 O O V
O — Ln N
0Cooc
O N O
✓ I� N CO)
N- O N N
• C) O (Oi)
N 6) — LC)
CO Cj N
Ln co
C) V V
LO
• CO O (.8
CO N- CO 00
N Ln O
O 6) Ln co
V
C
N (( .c
EEEc
m
0
C) Ln Lf) (fl
V
co co C7
O V
co co. co O
0) O - Ico
N CO CO O
• Co CO 4
N V O N-
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Cj V V
LC) O LC) 0
N N V
O co 0
N LC) O J
r r r
6) co - co
N LC) O
C
N
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N
CO
0
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(O O ao
Ln
N LC) O
4
O o
co O V
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cn
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co. co. (o co
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CO N
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— (p
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Cj V V
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C
N (( .c
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cn
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LC)
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V
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N N C)
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CO V CO 0
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LC) LC) O O
N O O V
N LO co
N O
co 6) O O
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N- CO CO co
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N CO O (h
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CO N O co
O V O V
C
N (( .c
EEEc
0
J
(O N
co co O
O
(O N 0) CO
6j O - I V
CO LC) CO N-
(O Co O V
C) O 00
OO V CO)
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N V O (0i)
N
co. V op 1
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co Ln
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C
N (( .c
EEEc
N
0
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Ln
Ln Ln V (0
V
00 O 6) O
co 4
O
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CO N- O O
I� CO N V
V O LC) N-
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N C) C) O
Cj L( O V
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N () V
✓ I� V co
N V O
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cn
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(Ci. OLri
O O 00 (p
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co () O
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op
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N LO 6) 0
V O V
C
N (( .c
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N
0
0
J
III-A-30

Table III -Al (continued).
N
N
c.)
O
Z
U
0
Q
N
a)
7
7
f3
2
L
f3
2
N
LL
7
CS) N 6)
Cfl O
LO
co - a0 (0
(3)
LO CO O
CO V
co O Co (fl
O 6)
7 (3) cc) O
V V O Cfl
LO 6) Cfl
(fl 00 ( O V
6) CO N O
N V O
In ('O co co
N ('7
CO co 0
(0 Ln
LO LO CO
V
C
co x
N (3 .0
EEEc
co
1-
0) 0) LSO
Cfl ( O
In
6) V LO Cfl
co O 6) p
CO V
O V LO (fl
6)
O O
O O (3j ( .
Co co co co
6j V 4-
co O co C)
Cs) 6j V V
V N— O
LO O CO co
N ('7
N- 6) CO
( i In O
In LO 6) u)
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C
co x
N (3 .0
EEEc
1-
✓ ' CO
✓ N O N
N- CO LO
Cfl Cfl Cfl (v)
O V
N N
N- O LO
N
N 6) LO
N
O CO N-
✓ V ( N
6) N
6) O co N
N v
O O O
✓ V N
() (0 O N
CO CO CO
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a0 V N
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• NT N
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C
co x
✓ (3 .0
EEEc
co
V CO
✓ N O N
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O CO. Cr)
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LO CO CO
N
✓ LO V
N
CO CO CO N
CO N-
N V O N
CO N
( LriN
(� 0) CO
co co N N
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N I� N
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N (3 .0
EEEc
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CO CO V
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(D. 'Cr. 6) (C)
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co - co Cfl
Cfl a0 N
co V - Co
N— CO O 0
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co
co CO co 0
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CO N CO CO
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C
co x
N (3 .0
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O N N
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LO
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cri
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CD. V (v
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✓ CO N Cfl
Cfl 6j V V
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co x
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6)
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ci
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N
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N CO 6)
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co(oco
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C
co x
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0
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6) V O
('O 00 V (fl
Co (r) (+o 0
6j O Cfl co
In O O Co
In O) O
co a)
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CO 6)
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✓ LO N CO
• o
N CO CO CO
C
co x
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EEEc
CO
0
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CO
Cfl N 0 N
In (0 O
ID
N N V p
CO � V
(D. Cfl N
O N 6j V
LO 7 N 0
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6) co O
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O CO N 0
In CO cd
N CO CO 0
N ri o
O co
✓ LO (o
O O O
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CO 0 0 co
• N O
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N Cfl O
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co x
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co
0
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Lb
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in. Cfl CO
✓ L
V 00 Op
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N- CO CO 0
CC5In V
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( i O V
co. 0) CO N
co co co
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0
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III-A-31

CNI
CNI
u
cu
0
2
0
0.
$
7
-)
2
�
2
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I
-)
\ c cck
n r
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\
\
2
n CO r o
G 6 w
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6 $
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a $
a)( e
E E E _
\
O
2
n r
w
6
7
r
co co r
¢ \ $
0 0 cc0 / w $
co 0 0 co
• a w $
@ - Q
w ci
CO @ A CO
6 $
A n CO
w a a $
a)( e
E E E
/
0
0
@-A 32

Table III-A2. Correlations between 2021 salinity and several climatic variables: Tar River
discharge, water depth, rainfall, wind speed and wind direction. White = Pre -Mod Alt, Gray =
Post -Mod Alt L, and Blue = Control. Bold values indicate significant correlation.
Station
Sample Size
(# of days)
Pearson's r correlation
Mardia's r correlation
Wind Direction
Discharge
Water Depth
Rainfall
Wind Speed
Broomfield Swamp Creek
BSCS1
365
-0.443 (lag: 0 days)
-0.125
-0.232 (lag: 1 day)
-0.103
0.260
BSCS2
365
-0.584 (lag: 0 days)
-0.175
-0.205 (lag: 2 days)
-0.134
0.282
BSCS3
365
-0.611 (lag: 0 days)
+0.080
-0.189 (lag: 3 days)
-0.162
0.296
SCUT1
SC1S1
365
-0.552 (lag: 0 days)
-0.318
-0.219 (lag: 1 day)
-0.103
0.210
SC1S2
362
-0.610 (lag: 0 days)
-0.491
-0.228 (lag: 7 days)
-0.116
0.246
SC1S3
365
-0.648 (lag: 0 days)
+0.201
-0.191 (lag: 7 day)
-0.138
0.273
Jacks Creek
JS1
365
-0.507 (lag: 0 days)
+0.046
-0.281 (lag: 2 days)
-0.104
0.326
JS2
365
-0.529 (lag: 1 day)
-0.076
-0.216 (lag: 3 days)
-0.107
0.317
South Creek
SS1
365
-0.528 (lag: 1 day)
+0.040
-0.212 (lag: 3 days)
-0.114
0.330
Little Creek
LCS1
365
-0.614 (lag: 0 days)
-0.222
-0.310 (lag: 3 day)
-0.139
0.278
LCS2
358
-0.575 (lag: 0 days)
-0.133
-0.321 (lag: 1 day)
-0.129
0.304
Jacobs Creek
JCBS1
359
-0.501 (lag: 4 days)
+0.292
-0.301 (lag: 2 days)
-0.078
0.270
JCBS2
365
-0.538 (lag: 4 days)
-0.171
-0.243 (lag: 1 days)
-0.100
0.319
PA2 Creek
PA2S1
365
-0.500 (lag: 6 days)
+0.214
-0.183 (lag: 6 days)
-0.098
0.321
Drinkwater Creek
DWS1
365
-0.516 (lag: 0 days)
+0.146
-0.319 (lag: 1 day)
-0.098
0.314
DWS2
365
-0.531 (lag: 5 days)
-0.402
-0.162 (lag: 3 days)
-0.103
0.324
Long Creek
LOCS1
365
-0.578 (lag: 3 days)
-0.051
-0.177 (lag: 7 days)
-0.106
0.315
LOCS2
365
-0.568 (lag: 4 days)
+0.243
-0.157 (lag: 7 days)
-0.104
0.318
Tooley Creek
TS1
365
-0.514 (lag: 6 days)
+0.054
-0.155 (lag: 6 days)
-0.098
0.324
TS2
355
-0.514 (lag: 5 days)
+0.069
-0.131 (lag: 7 days)
-0.094
0.307
Pamlico River
PS1
365
-0.555 (lag: 3 days)
-0.350
-0.053 (lag: 3 days)
-0.107
0.278
Huddles Cut
HS1
26
-0.538 (lag: 3 days)
+0.039
+0.581 (lag: 3 days)
+0.029
0.269
HS2
26
-0.655 (lag: 3 days)
+0.134
+0.619 (lag: 1 days)
+0.068
0.295
HS3
365
-0.549 (lag: 2 days)
+0.137
-0.095 (lag: 6 day)
-0.104
0.294
Porter Creek
PCS1
365
-0.562 (lag: 0 days)
-0.129
-0.200 (lag: 3 day)
-0.087
0.298
PCS2
365
-0.588 (lag: 4 days)
-0.065
-0.081 (lag: 7 days)
-0.091
0.313
Durham Creek
DCS1
365
-0.575 (lag: 2 days)
-0.044
-0.164 (lag: 6 days)
-0.099
0.307
DC19S1
363
-0.558 (lag: 0 days)
-0.205
-0.175 (lag: 7 days)
-0.098
0.310
DC11S1
365
-0.577 (lag: 0 days)
+0.050
-0.219 (lag: 1 days)
-0.091
0.293
Duck Creek
DKCS1
365
-0.560 (lag: 0 days)
-0.019
-0.228 (lag: 1 day)
-0.155
0.319
DKCS2
365
-0.449 (lag: 7 days)
+0.442
-0.062 (lag: 6 day)
-0.111
0.345
III -A-33