20080868 Ver 2_Executive Summary 2021 PCS Creeks Report_20220605

EXECUTIVE SUMMARY
• This report on 2021 data collection is the ninth of the annual PCS creek reports to
present and emphasize summary data, per the ROD Special Condition V on Reporting
where "annual summaries of all data collected" are specified.
• This summary approach is also part of the continued attempt to meet requests of the
reviewers and the Science Panel to reduce the amount of material included in the report
and to simplify the presentation of data. This is the ninth report to utilize multivariate
techniques for multiple monitoring parameters. These techniques will continue to be
used in various combinations until findings warrant a change in methodology. Analyses
of large data sets often results in statistically significant differences among
parameters/variables; however, these differences are not necessarily also ecologically
significant. Detection, measurement, and identification of ecologically significant issues
present a challenge with any complex large-scale project, especially in coastal
environments where the "estuarine paradox" may confound, or at least obscure,
conclusions about flora and fauna which have evolved resilient adaptations to wide
fluctuations in abiotic conditions. This subject is covered at annual Science Panel
meetings.
• For the benefit of those who have never been to any of these creeks, or at least did not
visit them at the beginning of this study, Appendix J was prepared for the 2016 report.
Appendix J included selected photographs of vegetation monitoring plots from 1998 and
from the most recent (as of 2016) vegetation monitoring of the original three creeks
(Jacks Creek-2014; Tooley Creek and Huddles Cut-2016). This collection of
photographs provided a visual comparison of physical changes at some of the
wells/plots since 1998. A copy of this photo appendix is available upon request. For
this 2021 report, Appendix G includes photographs of the 1998 and 2021 vegetation
monitoring at Huddles Cut as well as photos at Porter Creek and Duck Creek from the
2012 and 2021 vegetation surveys.
• For all statistical analyses of laboratory results (sediment and water column metals and
ECU water quality parameters), when the limits of detection for a specific method
returned a "< the method detection limit", the "<" was removed and the limit entered as
a value in the spreadsheet. This value is the limit of 100 percent confidence in detection;
while the value may actually be less, if it were present it would not be higher than this
limit. This practice reduces "gaps" in the graphical depictions and increases the value
of the statistical analysis. Nonetheless, some "gaps" do occur due to environmental
conditions (e.g., water too shallow to collect a sample), or laboratory conditions (e.g.,
equipment malfunction), or human error. Tabular depictions of metals results do not
remove the "<" and do not include those entries in calculations of means/standard
deviations.
• 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.
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. 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.
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.
• Wetland water levels (measured by In -Situ Level TROLLs) at many locations document
the influence in the short-term of large rain events, or several smaller events in a short
amount of time; however, some do not appear to be influenced in the long-term and their
hydroperiods do not always respond logically to rainfall. These rainfall/hydroperiod
variations make it difficult to directly correlate mine activities to a decrease in wetland
hydroperiod in all cases. Aside from rainfall, hydrology at some wells can also be
influenced by large Tar River discharges and by wind tides, which further complicates
interpretation. With addition of 2021 data in the wetland hydrology analysis, both prongs
at Huddles Cut had significantly longer hydroperiods in post -Mod Alt L years when all
well data were combined, and two wells in the main prong were significantly different
from pre -Mod Alt L. The post -Mod Alt L hydroperiod length for one well at Tooley Creek
(TW5) was significantly longer from pre -Mod Alt L; however, the middle well on the
western prong has not shown any significant changes in the number of non -wetland
species present in the vegetation transect. The post -mod Alt L hydroperiod length for
one well at Drinkwater Creek (DWW1A) was significantly shorter from pre -Mod Alt L;
however, when all wells were combined there was a general increase in hydroperiods
in the post -Mod Alt L years. The post -mod Alt L hydroperiod lengths for three wells at
DCUT11 (DC11W1A, DC11W2B, and DC11W2C) were significantly different from pre -
Mod Alt L.
In previous reports, a dynamic multiple linear regression model was used to compare
water depth to rainfall, wind speed, wind direction, and discharge across three different
time periods: pre, during, and post deep well pump operation. No adverse trends on
hydroperiods were detected or attributed to the deep well pump operation during past
evaluations; and thus, this same evaluation was not repeated for this report. Past results
indicate that estuarine wind -driven water and/or discharge from the Pamlico River are
also not primary influences at these sites.
• Additional years of water quality data may yield different findings; however, the water
quality data analyzed by Dr. David Kimmel of ECU for the 2013 report did include all
years for all water quality monitoring stations and no deleterious effects related to the
mine were detected. For the 2014 report, all years of data were used again but grouped

in two data sets for spatial and temporal analysis and comparison. The first set included
all years between 1999-2011 for Jacks Creek, Tooley Creek, and Huddles Cut. The
second set included all years from 2012 through the current year for all creeks. For this
2021 report, and presumably going forward unless directed otherwise, only the second
data set will be used for analysis as the information in the first data set would never
change or produce a different result. For the 2012 - 2021 analyses and comparison, the
variability in water quality among the creeks continues to be typical of estuarine creeks
within the Pamlico River estuary, with a distinct, identifiable seasonal pattern. Creeks
impacted by Mod Alt L followed a temporal trend that was also influenced by the spatial
location of the water quality monitoring stations. Both creeks with the most recent impact
(Porter Creek and DCUT11) showed higher variability in water quality parameters,
although this was mixed. It is important to note that given their proximity to the Pamlico
River estuary, this variability was less pronounced than the previously impacted creeks
further from the river. In addition, the water quality data for the creeks that have been
impacted longer presented a persistent trend in terms of intra-annual variability. This
indicated that stabilization of the water quality parameters is likely to continue (Gigon,
1983). Water quality changes from pre- to post -Mod Alt L do not appear to be
ecologically significant, as no changes in ecosystem structure or function were detected.
Continued monitoring in conjunction with other ecological parameters will determine if
these changes remain ecologically insignificant; past analysis of the other creeks
suggests water quality conditions will become more consistent over time.
• For sediment and water column metals, results show that with the exception of Zn in the
sediment at Jacks Creek in 2015, concentrations of sediment metals or 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 data were 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 prior to 2015. The 2021 averages for all combined
post -Mod Alt L creeks, which includes Jacks Creek, were below both the ERL and ERM.
• Most of the dominant species surveyed in 2021 were dominants in previous years.
Comparisons of pre- and post -Mod Alt L percentages of brackish intolerant dominants
for creeks with the most years of data showed the number of dominant brackish
intolerant species decreased in Huddles Cut. Dominant non -wetland percentages
reduced over the years and were almost non-existent for all creeks except Porter Creek,
DCUT11, and DCUT19. Through a SIMPROF based on the presence/absence of
species, temporally closer years were more similar to one another than less recent years
for all creeks, including control creeks. For the creeks with many years of data (Jacks
Creek, Tooley Creek, and Huddles Cut), some of the differences seen between pre- and
post -Mod Alt L may be related to changes in the ecosystem over the years due to natural
processes, disturbances from hurricanes, and sea level rise.
• No change in fish forage base due to mine activities is apparent. Multivariate cluster
analysis of fish for all creeks, all collection years, and both gear types (fyke and trawl)
reveals separation in some pre -Mod Alt L and post -Mod Alt L years within clusters;
however, the multivariate cluster analysis did not reveal distinct changes in fish
assemblages due to mine activities within the drainage basins of Jacks Creek, Jacobs
xxxiv

Creek, Drinkwater Creek, Tooley Creek, Huddles Cut, Porter Creek, and/or DCUT11.
Comparison of interannual variability by means of ANOSIM detected spatial differences
of statistical significance between pre- and post -Mod Alt L fish assemblages within the
drainage basin of Jacks Creek, Drinkwater Creek, and Tooley Creek. It is believed that
low CPUE observed locally throughout South Creek and surrounding tributaries in both
2016-2017 trawl samples set post -Mod Alt years apart from pre -Mod Alt L years in Jacks,
Drinkwater, and Tooley creeks, especially in Jacks Creek where 2016-2017 represent
two of the six post -Mod Alt L years.
The multivariate cluster analysis of managed fish for all creeks, all collection years, and
both gear types reveals some separation between pre -Mod Alt L and post -Mod Alt L
years within clusters; however, the analysis does not reveal distinct changes in the
assemblages of managed fish due to mine activities within the drainage basins of Jacks
Creek, Jacobs Creek, Drinkwater Creek, Tooley Creek, Huddles Cut, Porter Creek,
and/or DCUT11. Comparison of interannual variability by means of ANOSIM detected
spatial differences of statistical significance between pre- and post -Mod Alt L managed
fish assemblages of Jacks Creek, Tooley Creek and Drinkwater Creek. Low total CPUE
observed locally throughout South Creek and surrounding tributaries in 2016-2017 trawl
samples also likely affected CPUE of all managed species in every creek; however, low
CPUE of spot and higher CPUE of Atlantic croaker likely contributed to separation of
post -Mod Alt L years from pre -Mod Alt L years in Tooley Creek. Lower CPUE of spot in
post -Mod Alt L years in Jacks Creek likely contributed to separation of post -Mod Alt
years from pre -Mod Alt L years as two of the six post -Mod Alt L years for Jacks Creek
were 2016 and 2017. An increase in Atlantic croaker CPUE in post -Mod Alt L years
likely caused separation between pre- and post -Mod Alt L years in Drinkwater Creek.
Although there is a decline in CPUE of some managed species in Huddles Cut in post -
Mod Alt L years, the continued increase in CPUE of spot at Huddles Cut in post -Mod Alt
L 2015-2020 and persistent catches of Atlantic menhaden in both pre- and post -Mod Alt
L years contributed to no detection of spatial differences of significance between pre -
and post -Mod Alt L managed fish assemblages through 2021. Both diversity and
abundance of managed fish captured at Huddles Cut remain higher than most all other
sampled creeks and higher than DCUT11 and DCUT19 for 2013-2021 (data period for
the only other creeks sampled via fyke nets).
• Refinements and modifications to taxonomic information often change over time based
on additional information collected about particular species or professional
consensus/agreement; in addition there are times when species are "lumped together"
and then later "split". With the PCS creeks benthic data, numerous name changes have
occurred over the years (e.g., Hobsonia florida became Amphicteus floridus, Tubificidae
became Naididae), often between one year's report and the next. Identification guides
published since the early years of the 22-year study also provide confidence that an
Apochorophium unidentified to species in a given earlier year was either A. lacustre or
A. louisianum, species which are now grouped in the multivariate database and treated
as one, A. lacustre/louisianum; for taxa richness and calculation of EBI, they are
separated. Every year, the creeks benthic database was updated to reflect the
taxonomy for each taxon collected that year; but not until multivariate analysis required
the entire benthic database across all years for the 2013 report was the entire database
updated taxonomically for the dendrograms produced in each subsequent report.
Interannual comparisons between pre- and post -Mod Alt L years indicated five
significant spatial differences among benthic macroinvertebrates for four creeks with
xxxv

post -Mod Alt L data (Sweeps -upstream Jacobs Creek, downstream Tooley Creek,
upstream Huddles Cut, and downstream Porter Creek; Ponar-downstream Tooley
Creek). This result suggests that close to 82 percent of the comparisons (23 out of 28)
in the impacted creeks showed the benthic macroinvertebrate community of post -Mod
Alt L years as similar to that of the pre -Mod Alt L years; thus, it is difficult to discern any
mine -related patterns in benthic macroinvertebrate communities. Variability displayed
at the Huddles Cut upstream benthic station could be attributed to mine activities, but it
could also be related to the sand bar which formed at the mouth of Huddles Cut in 2009
(completely blocked flow in some conditions in portions of that year). The sand bar has
remained a persistent feature since then and continues to periodically narrow the
channel near the mouth, which restricts exchange of water between Huddles Cut and
the Pamlico River. Temporal variability analysis showed that the macroinvertebrate
ponar (upstream/downstream) guilds/trophic levels displayed a strong positive
correlation with environmental variables within two creeks (DCUT19 and Jacobs Creek).
The environmental parameters strongly correlated to the macroinvertebrate
guilds/trophic levels were temperature, conductivity, nitrate, dissolved oxygen, and
salinity. These results suggest that changes in benthic macroinvertebrate community
structure are driven by environmental variables. Interannual comparisons between pre -
and post -Mod Alt L years for guilds indicated no significant spatiotemporal differences
among benthic macroinvertebrates for all seven creeks with post -Mod Alt L data;
however, Porter Creek, Drinkwater Creek, and Tooley Creek showed differences in pre -
and post -Mod Alt L guild structure composition when compared to concomitant
composition of years in control creeks.
The all creeks dendrograms for sweeps and ponar richness and abundance show no
clear trend among the pre- and post -Mod Alt L macrobenthic data that could indicate
potential effects from mine activities. Except for Huddles Cut, sweep and ponar
years/locations richness and abundance are distributed into clusters represented by
similar years/locations for the control creeks and/or other pre -Mod Alt L years. For
Huddles Cut, the analysis showed that most pre- and post -Mod Alt L years commonly
clustered together, usually with no other creek. The guild dendrograms also show no
clear trend among the pre- and post -Mod Alt L macrobenthic data that could indicate
potential effects from mine activities. There was only one cluster that consisted solely
of post -Mod L data (Huddles 2012 and 2020 Downstream Sweeps); however, Huddles
Cut illustrates some unique characteristic that differentiates it from other creeks in the
study. As with richness and abundance data, most other post -Mod Alt L years for the
guilds were distributed into clusters which also contained a pre -Mod Alt L year for the
same creek or a matched control creek year. The mixed model ANOVA on guild
composition showed that changes in the benthic communities of two impact creeks post -
Mod Alt L did significantly differ from the changes in benthic communities of their
respective control creeks during the same time periods. In upstream Porter Creek there
were more grazer, scraper, and shredder guilds in post -Mod Alt L years when compared
to Little Creek (control). In downstream Drinkwater Creek, a nearby impact creek, there
were more herbivore and detritivore when compared to PA2 (control). This trend was
similar among downstream Tooley, another nearby impact creek, when compared to two
control creeks (Muddy and Long).
xxxvi