20080868 Ver 2_Section II F Q6 Water Quality 2021 PCS Creeks Report_20220605

F. Question 6-Has mining altered overall water quality within creeks?
Temporal and spatial variability among the creeks is summarized in Figure II-F1. Control
and pre -Mod Alt L impact creeks continue to exhibit the typical seasonal pattern detected in
previous years: a spatiotemporal pattern where increased freshwater flow in the spring has led to
low salinities, increased depths, increased turbidity, and higher nutrient concentrations. Summer
peaks in temperature and chlorophyll a concentration followed spring. Salinity and dissolved
oxygen values peaked as fall transitioned to winter, a time when temperatures and nutrient
concentrations were lowest. The majority of creeks showed this seasonal pattern and experienced
minimal intra-annual variability.
Table II-F1 shows the pre- to post- Mod Alt L change in water quality parameters for five
study creeks impacted by permitted mine activity under Mod Alt L and five control creeks
unimpacted by Mod Alt L. The control creek data in this table were arranged to match pre- and
post -Mod Alt L years for Jacks Creek, Jacobs Creek, Drinkwater Creek, Porter Creek and
DCUT11. Overall, the water quality in control creeks can be attributed to the yearly weather
conditions and unknown watershed activities. The control creeks, with the exception of Long
Creek (pre-(2012) to post-(2013-2021)) and small DCUT19 (pre-(2013-2017) to post-(2018-
2021)), showed some increases in temperature, albeit not significantly, depth, and turbidity, while
overall there were increases in some nutrient species. Most controls also showed a strong,
significant decrease in salinity, conductivity, and pH.
Impacted creeks showed greater intra-annual variability (Figure II-F1). After post -Mod Alt
L impact, most of the creeks generally experienced increases in depth, temperature, turbidity,
dissolved oxygen, and pH and decreases in salinity and conductivity, while nutrients showed a
more mixed response. These were similar changes as seen in the control creeks during the same
years, indicating what appear to be system -wide changes. Locations where post -Mod Alt L
impacts have been longer than four years showed no major changes in their pattern for most
water quality parameters (Table II-F1).
In addition, we have included Huddles Cut, Tooley Creek and Jacks Creek into a separate
table (Table II-F2) without an accompanying control creek, since those impacted creeks have
been monitored longer than the control creeks. Jacks Creek was the only impacted creek present
in both Table II-F1 and Table II-F2, because this specific site has pre years that align with the
control creeks. All creeks in Table II-F2 showed increases in temperature, dissolved oxygen, and
conductivity, while the pH and turbidity decreased. Most of the nutrients also presented a mixed
response as observed for the impacted creeks in Table II-F1.
There appeared to be no significant overall trends in water quality over time when principal
components were analyzed (refer to Section III-C for details); however, some stations have
experienced differences pre- and post -Mod Alt-L as shown in Table II-F1 and as described above.
The majority of these changes did not appear to affect the phytoplanktonic community (changes
in chlorophyll a and dissolved oxygen are not significant and do not indicate eutrophication), and
neither do changes in nutrient concentrations.
Creeks vary on their distance from the Pamlico River estuary which has some influence
on the water quality parameters. For example, nutrients became diluted at stations closer to the
influence of estuarine water, with the exception of Porter Creek, which continues to show
significant increases in most nutrient values. Upstream locations differed only in water level, as
some downstream stations had much higher average depths. Otherwise, water quality
II-F-1

parameters continue to show similar values upstream and were more typical of freshwater
conditions than estuarine conditions.
Answer: Overall, 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 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.
II-F-2

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II-F-3

Table II-F1. Differences in water quality parameters between five study creeks impacted by Mod Alt L (names in bold) and five creeks unimpacted by Mod Alt L (control creeks). Control creek (Little Creek, Long
Creek, PA2, DCUT19, and Duck Creek) data years are arranged to match the pre- and post -Mod Alt L data years for each impact creek (Jacks Creek, Jacobs Creek, Drinkwater Creek, Porter Creek, and DCUT11).
Water quality parameters are: Depth (DEP, in), Temperature (TEMP, C), Salinity (SAL), Conductivity (COND, mS), Turbidity (TURB, NTU), Dissolved oxygen (DO, mg L-1), pH (pH), Ammonium (NH4, mg L-1), Nitrate
(NO3, mg L-1), Dissolved Kjeldahl Nitrogen (DKN, mg L-1), Particulate Nitrogen (PN, mg L-1), Total Dissolved Nitrogen (TDN, mg L-1), Orthophosphate (PO4, mg L-1), Total Dissolved Phosphate (TDP, mg L-1),
Particulate Phosphate (PP, mg L-1), Chlorophyll a (CHL, pg L-1) and dissolved organic carbon (DOC, mg L-1). Empty cells signify no change between pre- and post -Mod Alt L. Shading within cells indicates statistically
significant differences between pre- and post -Mod -Alt L values.
Differences pre-(2012-2014) to post-(2015-2021)
Differences pre-(2012-2013) to post-(2014-2021)
Differences pre-(2012) to post-(2013-2021)
Differences pre-(2012-2015) to post-(2016-2021)
Jacks
Creek
Little
Creek
Long
Creek
PA2
Jacobs
Little
Long
Creek
PA2Creek
PA2Creek
Drinkwater
Little
Creek
Long
Creek
PA2
Porter
Little
Long
Creek
PA2Creek
PA2Creek
Duck
DEP
-0.5%
9.4%
6.0%
10.6%
7.3%
12.3%
10.5%
13.8%
8.6%
12.8%
10.2%
21.3%
21.3%
11.4%
9.5%
9.2%
28.4%
TEMP
2.6%
2.8%
1.0%
4.2%
4.5%
4.1%
1.9%
5.9%
1.8%
3.2%
-1.1%
4.9%
1.7%
3.4%
1.3%
4.1%
2.9%
SAL
-40.8%
-52.5%
-45.9%
-44.6%
-52.7%
-80.2%
-64.7%
-62.4%
-26.1%
-86.7%
-64.6%
-61.0%
13.4%
-30.3%
-29.5%
-27.1%
-31.1%
COND
-33.3%
-44.3%
-38.9%
-37.8%
-47.2%
-66.6%
-56.3%
-53.5%
-23.0%
-69.3%
-57.4%
-52.1%
-1.3%
-25.1%
-24.4%
-22.4%
-26.0%
TURB
-17.3%
46.3%
19.7%
20.7%
66.7%
58.4%
24.2%
19.3%
28.1%
69.9%
24.3%
38.9%
56.8%
39.5%
22.9%
21.5%
28.5%
DO
3.8%
.1.9%
-12.3%
1.7%
7.5%
1.5%
-8.5%
5.5%
-3.8%
6.1%
-4.1%
8.0%
-6.2%
-1.8%
-14.1%
-4.7%
-11.3%
pH
-0.3%
-3.4%
-4.7%
-1.8%
-1.7%
-4.4%
-5.5%
-2.7%
2.4%
-3.8%
-4.0%
-2.5%
4.8%
-1.9%
-4.4%
-2.0%
-2.4%
NH4
-117.5%
-5.4%
51.1%
37.4%
-16.5%
16.2%
42.3%
21.1%
31.6%
6.6%
39.3%
36.5%
36.8%
-1.3%
53.7%
42.5%
29.2%
NO3
-54.1%
5.2%
-64.1%
-83.1%
-69.7%
25.3%
-57.4%
-147.0%
-11.8%
46.6%
-17.2%
-13.0%
-85.0%
0.7%
-29.6%
-74.3%
43.6%
DKN
-16.8%
4.6%
-1.3%
-3.6%
-2.5%
7.7%
-9.8%
-12.9%
-9.6%
0.9%
-17.2%
-23.9%
23.8%
6.2%
3.0%
2.5%
19.0%
PN
-49.9%
-17.5%
1.5%
-9.6%
-5.1%
-21.3%
7.1%
-15.0%
-31.4%
-47.5%
4.6%
-35.6%
27.5%
-19.4%
-1.3%
-11.4%
-19.3%
TDN
-11.3%
11.0%
21.3%
11.9%
3.4%
16.0%
11.5%
2.5%
0.1%
25.2%
19.2%
11.7%
21.2%
5.9%
13.5%
8.0%
19.2%
PO4
30.2%
57.6%
-5.1%
12.8%
26.7%
-46.7%
14.9%
29.0%
-35.2%
-44.0%
21.8%
29.4%
47.7%
-57.9%
-17.0%
2.4%
-10.2%
TDP
18.0%
-32.9%
1.8%
8.3%
17.9%
-24.7%
1.6%
12.3%
-33.0%
-22.9%
5.6%
11.5%
23.7%
-38.0%
-3.4%
-3.9%
-5.0%
PP
-10.9%
-15.2%
-12.3%
-20.8%
-31.6%
-31.6%
-26.0%
-43.5%
-47.4%
-42.9%
-27.4%
-54.2%
19.3%
-9.4%
-8.8%
-16.5%
-23.4%
CHL
-214.5%
-69.4%
20.2%
-23.3%
-6.3%
-104.1%
23.7%
-38.1%
-83.6%
-177.5%
10.7%
-76.2%
39.4%
-55.7%
20.8%
-8.6%
-39.7%
DOC
3.5%
12.5%
17.0%
9.1%
8.1%
9.8%
15.0%
6.0%
-38.6%
2.2%
10.1%
1.4%
13.3%
14.9%
16.5%
13.5%
11.0%
I I-F-4

Table II-F1 (concluded'.
Differences pre-(2013-2017) to post-(2018-2021)
DCUT11
Little Creek
Long Creek
PA2
DCUT19
DEP
9.4%
12.2%
8.5%
6.8%
28.4%
TEMP
3.6%
1.2%
0.9%
0.6%
-0.3%
SAL
6.3%
2.8%
-9.1%
-5.2%
5.8%
COND
6.6%
2.0%
-8.2%
-4.1%
4.7%
TURB
-56.6%
7.9%
4.7%
23.8%
-87.7%
DO
4.9%
-2.6%
-9.6%
-7.4%
15.9%
pH
3.9%
0.2%
-1.0%
-0.4%
1.4%
NH4
-54.2%
58.6%
-48.3%
-49.8%
-166.2%
NO3
21.9%
-36.0%
-79.5%
-80.7%
36.0%
DKN
1.8%
-8.0%
2.7%
5.6%
-42.5%
PN
-27.1%
-11.3%
-10.79
-4.5%
-37.4%
TDN
10.2%
-12.1%
5.0%
5.4%
-10.2%
PO4
-16.0%
-35.6%
-26.9%
-2.3%
-47.7%
TDP
-14.1%
-28.6%
2.3%
-0.5%
-27.6%
PP
-20.0%
-8.1%
-9.8%
-3.0%
-37.9%
CHL
1.0%
10.4%
22.6%
10.5%
12.4%
DOC
11.7%
16.2%
14.4%
17.4%
3.8%
II-F-5

Table II-F2. Differences in water quality parameters between three study creeks impacted by
Mod Alt L; Huddles Cut, Tooley Creek, and Jacks Creek. These three study creeks are not
compared to control creeks within this table because these creeks have a longer running
dataset than other monitored creeks in this study. Water quality parameters are: Depth (DEP,
in), Temperature (TEMP, C), Salinity (SAL), Conductivity (COND, mS), Turbidity (TURB, NTU),
Dissolved oxygen (DO, mg L-1), pH (pH), Ammonium (NH4, mg L-1), Nitrate (NO3, mg L-1),
Dissolved Kjeldahl Nitrogen (DKN, mg L-1), Particulate Nitrogen (PN, mg L-1), Total Dissolved
Nitrogen (TDN, mg L-1), Orthophosphate (PO4, mg L-1), Total Dissolved Phosphate (TDP, mg L-
1), Particulate Phosphate (PP, mg L-1), Chlorophyll a (CHL, pg L-1) and dissolved organic carbon
(DOC, mg L-1). Empty cells signify no change between pre- and post -Mod Alt L. Shading
within cells indicates statistically significant differences between pre- and post -Mod -Alt L values.
Differences pre-(1999-2009)
to post-(2010-2021)
Differences pre-(1999-2011)
to post-(2012-2021)
Differences pre-(1999-2014)
to post-(2015-2021)
Huddles Cut
Tooley Creek
Jacks Creek
DEP
5.7%
4.6%
-8.4%
TEMP
17.4%
6.1%
8.2%
SAL
42.9%
13.5%
-5.5
COND
76.3%
13.9%
0.1%
TURB
-26.3%
-87.2%
-17.3%
DO
16.5%
5.7%
13.8%
pH
-0.7%
-3.2%
-1.5%
NH4
10.3%
8.3%
-63.6%
NO3
-100.0%
33.3%
-33.3%
DKN
13.4%
9.2%
-7.1%
PN
12.9%
0.0%
-34.5%
TDN
-10.1%
PO4
26.8%
14.3%
25.0%
TDP
20.3%
12.1%
12.5%
PP
-93.8%
-154.5%
-9.1
CHL
11.0%
-15.2%
-121.1%
DOC
3.6%
I I-F-6