20080868 Ver 2_Section II F Q6 Water Quality 2020 PCS Creeks Report_20210701

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 spatial and temporal 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 -Fla shows the pre- to post- Mod Alt L change in water quality parameters for
seven 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. We have included Tooley Creek and Huddles Cut without an accompanying control
creek in spite of both creeks having incomplete data records. 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-(2012-2013) to post-(2014-
2020)) and small DCUT19, 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 a greater intra-annual variability (Figure II-F1). After post -Mod
Alt L impact, all creeks generally experienced increases in depth, temperature and dissolved
oxygen and decreases in turbidity, conductivity, and pH, while nutrients showed a more mixed
response. These were essentially similar changes as seen in the control creeks during the
same years, indicating 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). For both Jacobs Creek and Drinkwater Creek, the post -Mod Alt L
period is longer than pre- which might explain the mixed response for the biological parameters.
However, from an ecological perspective, it seems that the impacted creeks reach a stable
phase in which parameter values are maintained but not necessarily returned to baseline
conditions (Grimm and Wissel, 1997).
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
parameters continue to show similar values upstream and were more typical of freshwater
conditions than estuarine conditions.
a Table II-F1 shows the water quality data in a specific arrangement of data years. The cumulative effects of time,
weather, land use (e.g., silviculture, agriculture, and/or pre- and post -Mod Alt L mine activities) are unique to each
creek and time period, whether a control or one impacted by permitted mine activity.
II-F-1

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 station. 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 creeks that have been impacted
longer, the combined both post -Mod Alt L conditions and weather, the water quality
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). The
majority of water quality changes from pre- to post -Mod Alt L were not ecologically
significant, as no changes in ecosystem structure or function were detected. Continued
monitoring will determine if these changes remain ecological insignificant whereas the
analysis of the other creeks suggests water quality conditions become more consistent
over time.
II-F-2

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Figure II-F1. Conceptual diagram to show temporal and spatial patterns among impact and control creeks.
II-F-3

Table II-F1. Percent differences in water quality parameters between seven 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-(1999-2011)
to post-(2012-2020)
Differences pre-(2012-2014) to post-(2015-
2020)
Differences pre-(2012-2013) to post-(2014-
2020)
Differences pre-(2012) to post-(2013-2020)
Differences pre-(2012-2015) to post-(2016-2020)
Huddles Cut
Tooley Creek
Jacks
Creek
Little
Creek
Long
Creek
PA2
Jacobs
Creek
Little
Creek
Long
Creek
PA2
Drinkwater
Creek
Little
Creek
Long
Creek
PA2
Porter
Creek
Little
Creek
Long
Creek
PA2
Duck
Creek
DEP
14.8%
4.5%
-0.4%
10.3%
5.4%
11.4%
8.7%
13.0%
-16.7%
21.8%
8.9%
13.3%
-4.2%
21.8%
17.7%
12.7%
9.2%
10.3%
27.7%
TEMP
16.7%
6.4%
2.4%
3.1 %
0.9%
4.3%
4.6%
4.3%
-3.2%
6.0%
1.9%
3.3%
4.8%
4.9%
1.3%
3.8%
1.3%
4.3%
2.9%
SAL
23.3%
14.9%
-40.5%
-55.9%
-43.7%
-41.9%
-50.4%
-83.8%
29.6%
-59.7%
-25.2%
-88.1 %
32.7%
-57.6%
9.2%
-32.8%
-26.8%
-23.7%
-33.0%
COND
73.1%
15.7%
-32.0%
-45.2%
-36.3%
-34.7%
-44.5%
-67.6%
-2.2%
-50.4%
-22.0%
-68.8%
2.5%
-48.7%
-4.2%
-25.3%
-21.3%
-18.7%
-25.9%
TURB
-55.2%
-92.5%
-12.6%
48.4%
17.3%
15.8%
68.8%
59.7%
78.9%
14.6%
29.7%
70.6%
81.5%
35.8%
59.2%
42.5%
20.9%
16.3%
31.1cYo
DO
19.7%
6.1 %
2.9%
-0.3%
-12.7%
2.1 %
8.4%
2.9%
59.6%
6.0%
-4.8%
7.3%
64.7%
8.4%
-7.4%
0.01 %
-15.0%
-4.6%
-11.9%
pH
-0.1 %
-3.2%
-0.2%
-2.9%
-4.5%
-1.5%
-1.3%
-4.0%
57.4%
-2.4%
2.1 %
-3.4%
62.0%
-2.2%
4.7%
-1.3%
-4.2%
-1.7%
-2.2%
NH4
-3.2%
15.4%
-107.0%
2.3%
56.8%
43.7%
-7.0%
21.8%
99.9%
27.7%
33.3%
12.0%
99.9%
41.1 %
44.0%
7.5%
60.0%
49.4%
32.1cYo
NO3
-81.0%
33.3%
-48.3%
16.7%
-57.6%
-71.3%
-62.7%
33.3%
99.9%
-134.1 %
10.0%
51.6%
99.9%
-6.0%
-71.4%
14.8%
-22.3%
-61.8%
44.7%
DKN
11.0%
7.6%
-15.7%
6.2%
0.6%
-2.6%
-2.3%
9.1 %
95.5%
-12.2%
-8.4%
2.0%
95.7%
-23.2%
26.4%
8.3%
5.3%
4.0%
20.7%
PN
4.4%
3.0%
-44.7%
-14.0%
3.7%
-6.1 %
-1.9%
-18.0%
98.5%
-11.9%
-25.9%
-44.1 %
98.7%
-32.4%
27.8%
-15.6%
1.2%
-7.4%
-15.5%
TDN
-11.3%
15.6%
21.9%
10.9%
1.9%
19.7%
97.4%
1.0%
-1.1 %
28.1 %
97.8%
10.7%
23.1 %
11.5%
14.1 %
6.7%
20.0%
PO4
28.1 %
11.1 %
24.7%
-60.2%
-9.8%
8.1 %
13.2%
-47.2%
99.9%
26.0%
-38.6%
-43.6%
99.9%
26.4%
38.5%
-62.9%
-25.1 %
-5.0%
-11.5%
TDP
22.0%
9.4%
15.4%
-32.3%
0.7%
7.4%
10.0%
-23.4%
99.7%
11.5%
-34.6%
_21.5%
99.8%
10.6%
22.2%
-38.5%
-5.3%
-6.2%
-2.8%
PP
-138.1%
-133.3%
-3.8%
-13.4%
-12.1 %
-19.3%
-28.6%
-30.1 %
99.6%
-42.5%
-36.7%
-41.2%
99.7%
-52.7%
23.1 %
-7.1 %
-8.7%
-15.0%
-19.4%
CHL
-11.9%
-19.4%
-229.7%
-76.5%
16.5%
-29.9%
-10.3%
_111.9%
40.8%
-44.8%
-82.0%
_185.4%
40.0%
-83.5%
32.7%
-64.1%
17.0%
-14.6%
-45.6%
DOC
0.5%
8.8%
15.4%
4.9%
3.1 %
6.2%
47.7%
2.0%
-41.5%
_1.5%
51.2%
-2.4%
9.5%
11.1 %
14.9%
9.4%
8.2%
I I-F-4

Table II-F1 (concluded).
Differences pre-(2013-2017) to post-(2018-2020)
DCUT11
Little Creek
Long Creek
PA2
DCUT19
DEP
8.9%
15.3%
8.6%
9.2%
30.3%
TEMP
4.1%
1.8%
0.8%
0.7%
-0.8%
SAL
4.1%
1.4%
-5.4%
-0.3%
7.2%
COND
8.9%
3.1%
-4.0%
1.4%
6.8%
TURB
-55.7%
14.1 %
-1.5%
18.3%
-92.0%
DO
4.9%
0.4%
-11.2%
-7.7%
19.2%
pH
3.8%
1.4%
-0.4%
0.3%
1.4%
NH4
-50.0%
-44.0%
-21.3%
-27.9%
-159.9%
NO3
15.4%
-8.1%
-75.3%
-64.3%
25.0%
DKN
2.6%
-6.3%
6.1%
7.9%
-39.4%
PN
-22.2%
-6.6%
-7.6%
1.1%
-26.7%
TDN
7.1%
-2.8%
5.8%
3.5%
-8.8%
PO4
-33.3%
-43.7%
-45.8%
-15.2%
-48.1%
TDP
-14.3%
-30.7%
0.6%
-3.3%
-25.6%
PP
-25.0%
-6.1%
-11.2%
-0.9%
-30.8%
CHL
-4.3%
5.8%
18.2%
2.9%
15.3%
DOC
9.8%
11.2%
12.4%
12.4%
2.1%
II-F-5