I-34_Brier Creek, Lick Creek, and Stirrup Iron Creek Watershed Study- Final- 02252022

CITY OF DURHAM
Department of Public Works
Stormwater & GIS Services
Water Quality Report #20-002
February 25, 2022
CITY OF
DURHAM
Brier Creek, Lick Creek, & Stirrup Iron Creek Watershed Study- Final Report
Executive Summary
The Brier Creek, Lick Creek, & Stirrup Iron Creek Watershed Study was conducted in support of the City of Durham's
(COD) Stormwater Management Plan and Watershed Implementation Plans. This study was conducted between August
2020 and July 2021 with monitoring at four sites: BC6.6LBCTA (Brier Creek watershed), LC1.1LC (Lick Creek watershed),
LC2.ORBC (Lick Creek watershed), and 511.6SIC (Stirrup Iron Creek watershed). Monitoring in this study focused on water
quality, sediment quality, and biological community health. Water quality parameters were collected during seasonal
baseflow conditions and also during two storm events. Bankfull cross -sections and baseflow discharge were measured
during four baseflow sampling events. Benthic macroinvertebrate sampling was conducted at sites representing the Lick
Creek and Stirrup Iron Creek watersheds. Habitat assessments surveys were conducted at all four monitoring sites and
at six additional sites chosen to represent areas within their associated watershed.
Elevated concentrations of dissolved copper (Cu) were observed in baseflow and stormflow samples at 511.6SIC and in
stormflow samples at BC6.6BCTA and LC1.1LC. A geometric mean for fecal coliform greater than 400 CFU/100 mL was
observed at LC2.ORBC in baseflow samples. Elevated total aluminum (AI) concentrations that were above the criteria
continuous concentration (CCC) were present in some samples at all four sites during baseflow. Elevated turbidity in
baseflow samples was observed once at LC1.1LC and twice at 511.6SIC. Elevated hardness occurred once at LC1.1LC in
baseflow samples.
In sediment quality samples, toxic effect concentrations (TEC) were exceeded for multiple polycyclic aromatic
compounds (PAHs) at BC6.6BCTA and 511.6SIC. PAHs are generally products of combustion and sources include the
burning of fossil fuels such as gasoline and diesel, coal tar, asphalt, and wood burning.
The benthic macroinvertebrate community was rated as "Good- Fair" at LC1.1LC, and "Poor" at 511.6SIC. From 2014 to
2020, ratings for LC1.1LC have ranged from "Fair" to "Good- Fair", while 511.6SIC had not been rated prior to this study.
Habitat assessments scores ranged from 39 to 70 in the study watersheds, with the lowest score reported at S11.6SIC,
and the highest reported at LBC1, a habitat assessment site located in the Brier Creek watershed. The majority of survey
sites in all three watersheds received lower rankings due to nearly homogenous sandy substrate. While sand substrate
naturally occurs in the Triassic Basin, it is rated lower in habitat assessments when compared to rock and cobble
substrate found in other ecoregions. Sites were also generally ranked lower due to indicators of high -flow erosion
including steep, incised banks, and limited bank vegetation.

Contents
ExecutiveSummary................................................................................................................................................................. 1
Figures............................................................................................................................................................................. 2
Abbreviations.......................................................................................................................................................................... 3
Introduction............................................................................................................................................................................ 4
Brier & Stirrup Iron Creek Watersheds- HUC030202010801, Class C, NSW......................................................................4
Lick Creek Watershed- HUC:030202010502, Class WS-IV, C, NSW....................................................................................
5
SiteDescriptions................................................................................................................................................................. 5
Methods..................................................................................................................................................................................
7
Deviationsfrom the QAPP..................................................................................................................................................
8
Weather................................................................................................................................................................................
10
WaterQuality Sampling Results............................................................................................................................................
11
BaseflowWater Quality Sampling....................................................................................................................................
11
StormflowMonitoring Results..........................................................................................................................................
15
SedimentQuality Sampling Results......................................................................................................................................
21
PhysicalAnalysis...............................................................................................................................................................
21
ChemicalParameter Results.............................................................................................................................................
22
SedimentToxicity Results.................................................................................................................................................
23
Benthic Macroinvertebrate Community Sampling Results...................................................................................................
25
Stream Cross Sections and Discharge...................................................................................................................................
26
HabitatAssessments.............................................................................................................................................................
30
BrierCreek Watershed.....................................................................................................................................................
31
LickCreek Watershed.......................................................................................................................................................
31
StirrupIron Creek Watershed...........................................................................................................................................
32
Conclusions...........................................................................................................................................................................
33
References............................................................................................................................................................................
35
Appendix I Baseflow Monitoring Data..................................................................................................................................
36
Figures
Figure 1 Sampling and habitat assessment sites for the Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
6
Figure 2 Taken at the original location for BC6.6BCTA, stagnant pools were visible throughout the reach on 8/27/2020.
8
Figure 3 Original and New Location of BC6.6BCTA. All samples in this report were collected at the new location. The
Original location was never sampled.
9
Figure 4 Drought Conditions for the County of Durham during the study period 2020-2021.
10
Figure 5 Monthly total precipitation at KRDU during the study period, August 2020 to June 2021.
11
Figure 6 Stormflow sampling times (symbols) and hourly rainfall totals (blue bars), 9/17-9/18/2020.
15
Figure 7 Facing upstream of LC2.ORBC on 06/02/2021.
16
Figure 8 Stage and sample times at BC6.6BCTA, 6/2/2021.
16
Figure 9 Stage and sample times at LC2.ORBC, 6/2/2021.
17

Figure 10 Stage and sample times at 511.6SIC, 6/2/2021.
Figure 11 Stage and sample times at LC1.1LC, 6/20/2021.
Figure 12 Stage and sample times at LC2.ORBC, 6/20/2021.
Figure 13 Cross Section measurements at BC6.6BCTA, facing upstream.
Figure 14 Cross section measurements at LC1.1LC, facing upstream.
Figure 15 Cross section measurements at LC2.ORBC, facing upstream.
Figure 16 Cross section measurements at S11.6SIC, facing upstream.
Figure 17 511.6SIC on 2/13/2013, taken as part of routine ambient monitoring.
Figure 18 511.6SIC facing downstream, 6/30/2021.
Abbreviations
17
Error! Bookmark not defined.
18
27
27
28
28
29
30
AFO
Animal Feeding Operations
Al
Aluminum
NH3
Ammonia
As
Arsenic
BLM
Biotic Ligand Model
CCC
Criteria Continuous Concentration
Cd
Cadmium
CFU
Colony -forming Unit
Cl-
Chloride
CIVIC
Criteria Maximum Concentration
Cr
Chromium
COD
City of Durham
Cu
Copper
DOC
Dissolved Organic Carbon
DO
Dissolved Oxygen
ft.
Feet
in
Inch
Pb
Lead
Hg
Mercury
MDL
Method Detection Limit
mL
Milliliter
MRL
Method Reporting Limit
Ni
Nickel
NOx
Nitrate & Nitrite
K
Potassium
PAHs
Polycyclic Aromatic Hydrocarbons
PEC
Probable Effect Concentration
CA
Quality Assurance
QAPP
Quality Assurance Project Plan
RDU
Raleigh Durham International Airport
Na
Sodium
SOP
Standard Operating Procedures
SOa
Sulfate
TEC
Threshold Effect Concentration
TV
Tolerance Values
TKN
Total Kjeldahl Nitrogen
TOC
Total Organic Carbon
TP
Total Phosphorous
TSS
Total Suspended Solids
WIPs
Watershed Improvement Plans
WQU
Water Quality Unit
Zn
Zinc
3

Introduction
As directed in the City of Durham's (COD) Stormwater Management Plan, this project was conducted in support of the
following Assessment and Monitoring Core and Supplemental goals [1]:
Core Goals
• to identify pollution problem areas within the City
• to assess compliance with state water quality programs, including Total Maximum Daily Loads (TMDLs), water
quality standards, and nutrient management strategies
Supplemental Goals
• to assess the overall quality of streams within the City of Durham
• to evaluate the water quality impacts of urban stormwater on area streams
Results generated by this study may also be used during the development of watershed improvement plans (WIPs) to
plan for the implementation of best management practices within the study watersheds. For this study, the Brier Creek,
Lick Creek, and Stirrup Iron Creek watersheds were selected for monitoring that included water quality, sediment
quality, hydrology, and biological assessments. While the City has routine ambient monitoring sites in the Lick Creek and
Stirrup Iron Creek watersheds, the Brier Creek watershed has not been sampled by the Water Quality Unit (WQU) before
this study. A description of the watersheds and their characteristics are further discussed below.
Brier & Stirrup Iron Creek Watersheds- HUC030202010801, Class C, NSW
Brier Creek and Stirrup Iron Creek are both contained in the Upper Crabtree Creek watershed. The Brier Creek
watershed consists of a relatively small drainage area of 2.96 square miles. Drainage areas include parts of southern
Durham and northern Wake Counties. It is made up of two major tributaries, Brier Creek and Little Brier Creek, as well as
numerous intermittent streams; less than 10 in the Brier Creek subwatershed and more than 20 in Little Brier Creek
subwatershed. The Brier and Little Brier Creeks converge at the Brier Creek Reservoir; which also receives drainage from
a large portion of the Raleigh Durham International Airport (RDU). Brier Creek continues flowing south, converging with
the Stirrup Iron Creek to form the northwest backwaters of Lake Crabtree. Currently, the City of Durham city limits
include approximately 1.40 square miles of the Brier Creek watershed [2]. Land use in the Brier Creek watershed is a
majority mixed -developed land use (57%) that includes RDU Airport, as well as major thoroughfares including Interstate
Highways 40, 70, and 540 [2] [3]. The second-largest land use is various forest types covering 29% of the watershed [3].
Immediately adjacent and upstream of the monitoring site in the Brier Creek Watershed, the area is classified as
medium to high density development with some mixed forest [3]. The site is also located immediately adjacent to
Highway 70. This site is slightly upstream of future North Carolina Department of Transportation Project U-5518, U.S. 70
Improvements at Brier Creek Parkway & T.W. Alexander Drive [4].
The Stirrup Iron Creek watershed has a total drainage area of 11.94 square miles with 8.12 square miles contained
within city limits [2]. This watershed consists of Stirrup Iron Creek, three additional unnamed tributaries, as well as more
than 10 intermittent streams [1]. Visual review of GIS maps also indicates that at least two minor reservoirs are located
within the Stirrup Iron Creek watershed. The majority of land use of this watershed is classified as differing intensities of
developed land (56%), with 32% of the remaining usage classified as various forest types. Portions of Interstate
Highways 40 and 540 are located within this watershed [2]. Areas adjacent to the sampling site are mixed industrial use
along Miami Boulevard, Chin Page Road, and T.W. Alexander Drive.
Both the Brier Creek and Stirrup Iron Creek watersheds are located entirely in the Triassic Basin Geologic Terrane, a
geological region characterized by conglomerates, sandstone, siltstone, and mudstone, with diabase intrusions [2]. Soil
surveys of the area containing both watersheds indicate a dominant soil type of "Urban Land" (25.3%), which is
characterized as "impervious layers over human -transported material" reflective of the development intensity in this
area. Hydrologic soil types for the Brier Creek watershed are majority type C (49.2%) with Type B (35.6%) and the
remainder consisting of Type D soils, while Stirrup Iron Creek watershed is majority Type D (43.2%) and Type C (32.3%)
4

with the remainder consisting entirely of Type B soils [5]. Type C and Type D soils present in Stirrup Iron Creek and Brier
Creek indicated that these watershed have low infiltration rates and are highly erodible [5].
Lick Creek Watershed- HUC:0302O2O1O5O2, Class WS-IV, C, NSW
The Lick Creek watershed is located in the eastern part of the County of Durham and is relatively less developed when
compared to other watersheds within the City. The watershed drainage area is 21.83 square miles, 3.70 of which are
located within COD city limits [2]. The watershed consists of three major tributaries, Laurel Creek, Lick Creek, and Rocky
Branch Creeks, and more than 50 intermittent streams. The Lick Creek watershed ultimately discharges into the Falls of
the Neuse Reservoir. The watershed is predominantly undeveloped, with 69.2 % of overall land use categorized as either
deciduous, evergreen, or mixed forest. The second highest land use in the watershed, encompassing 12.9%, is
categorized as various types of development, a majority of which is located within the current COD city limits [3]. The
Lick Creek and Rocky Branch Creek subbasins are located entirely within the Triassic Basin Terrane, while Laurel Creek is
contained in the Carolina Slate Belt and Raleigh Terranes. Those terranes differ from the Triassic Basin in that generally,
they are dominated by metamorphosed argillite, mudstone, gabbro, and diorite, in contrast to the sandstone, siltstone,
and mudstone that dominate Triassic soils [2]. Soil surveys of the areas including the Lick and Rocky Branch Creeks
indicate that the predominant soil type is White Store Sandy Loam at 6- 25% slopes, consistent with the weathered
residuum of the parent Triassic Basin, while the Laurel Creek watershed consists of various types of Fine Sandy Loams,
with the majority classified as Type B (55.9%), and Type D (27.9%), with the remainder consisting of Type C soils [5]. Type
B soil is indicative of moderate to well -drained soils. Due to the differences between base geology, and that a majority of
the Laurel Creek drainage basin is located outside of COD city limits in Wake County, the Laurel Creek drainage area was
not part of this study. Areas upstream of the monitoring site on Lick Creek are mostly undeveloped forest game lands
maintained by the U.S. Army Corps of Engineers. Areas upstream of the monitoring site on Rocky Branch Creek are
mostly undeveloped meadow or grass land, with historical animal feeding operations (AFOs).
Site Descriptions
The WQU is responsible for routine ambient water quality monitoring and biological community assessments at
representative sites in and around the City. As part of this routine monitoring, two sites in the Lick Creek watershed are
monitored in even years, and one site in the Stirrup Iron Creek watershed is monitored in odd years. Benthic
macroinvertebrate sampling was also conducted in even years at one site in the Lick Creek watershed. These ambient
monitoring sites were selected as sampling sites for water quality, sediment quality, and hydrology assessments for this
study. A new site was created in the Brier Creek watershed because monitoring had never been conducted in the
watershed by the WQU. Water quality, sediment quality, discharge, and cross -sections were collected at all four sites.
Benthic macroinvertebrate sampling was also conducted at the monitoring site in the Stirrup Iron Creek watershed as
part of this study. Benthic macroinvertebrate samples were collected as part of routine benthic monitoring in 2020 at
the Lick Creek sampling site. Habitat assessment surveys were conducted at the four monitoring sites in this study, as
well as an additional six sites representative of the watersheds. Sites are shown below in Figure 1 with descriptions in
Table 1.
5

, e*
Franklin
Wake
Chatham
Johnston
Miles
C rossings
' Gc If Club
ry -
Stirrup Iron Creek watershed
t�r k
Clu
Falls Lake States
Rec realron Area
f a Its Lake `
� I I
Lick Creek watershed f
1
V
i
Falls a LG Ci
I �
z
�tXon G� e
f Upo e" 0
,
5�3 K
~ Brier Creek watershed Lo,'.-r'Q'-al�on C[e
o`
C
r n'
I
Rale h-
D am
I Au�,-rt
f
W: rlltam
8 Um;tead
State Par k
Sources: Esri, HERE, Garmin, Intern
NIPS, NRCAN, GeoBase, IGIN, Kadaster NIL. ordna4� SLu vey, Esri Japan, MFTI,
Esri China (Hong Kong), (c) OpenStreetddd' contributors, and h GIS User
Community. „
Map prepared byStormwater & CIS Servicies N Brier Creek,
Dept. Public Works on 11/15/2021. Lick Creek, &
Information depicted is for reference purposes only.
The City of Durham assumes no responsiblity for errors Stirrup Iran Creek
CITY OF arising from use or misuse of this map. Miles watersheds
DURHAM o 1 2
Figure 1 Sampling and habitat assessment sites for the Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
A

Table 1 Monitoring and habitat assessment sites for the Brier Creek, Lick Creek & Stirrup Iron Creek watershed study.
Site ID
Site designation
Stream
Description
Latitude, Longitude(dec. degrees)
BC6.6LBCTA
Monitoring
Little Brier Creek
Little Brier Creek Tributary @
35.93038,-78.806381
Hwy 70 and Quate Industrial Dr.
S11.6SIC
Monitoring
Stirrup Iron Creek
Stirrup Iron Crk at Chin Page Rd.
35.89749,-78.84598
LC1.1LC
Monitoring
Lick Creek
Lick Crk at Southview Rd south of
35.97811,-78.74988
Hwy 98
LC2.ORBC
Monitoring
Rocky Branch Creek
Rocky Branch Crk at Kemp Rd @
35.96329,-78.54057
intersection with Southview rd.
LBC1
Habitat
Little Brier Creek
Little Brier Crk NR Oysterwood Ln
35.92590,-78.79040
LC1
Habitat
Lick Creek
Lick Crk NR Laurel Mist Way
35.96220,-78.79700
LC2
Habitat
Lick Creek
Lick Crk @ Olive Branch Rd NR
35.96680,-78.78330
Doc Nichols Rd
LC32
Habitat
Lick Creek
Lick Crk @ Olive Branch Rd
35.95000,-78.77290
S11
Habitat
Stirrup Iron
Stirrup Iron Crk NdR TW Alexander
35.92010,-78.83130
S12
Habitat
Stirrup Iron
Stirrup Iron Crk Trib A NR TW
35.92220,-78.83640
Alexander Rd
S13
Habitat
Stirrup Iron
Stirrup Iron Crk Trib C @ Roche
35.91510,-78.82480
D
1. Original location for BC6.6LBCTA, 35.92709,-78.80134, was not sampled in this study due to intermittent flow and non -ideal sampling
conditions.
2. LC3 was not assessed due to safety concerns.
Methods
Four representative baseflow water quality samples were collected quarterly at all monitoring sites beginning in August
of 2020. A baseflow sampling event included collecting physical and chemical water quality parameters, discharge
measurements, and cross -sections. Physical and chemical parameters collected are shown below in Table 2. For this
study, baseflow was defined as stream conditions with at least 72 hours of preceding dry weather conditions. Physical
and chemical parameters were collected according to COD standard operating procedures (SOP) [6] [7]. Cross sections
and discharges were measured at transects established near the sampling site. Stream discharge measurements were
collected using a Flowtracker ADV flow meter according to COD SOP [8].
Table 2 Baseflow physical and chemical parameters measured as part of the Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
Physical parameters
Chemical parameters
Dissolved oxygen (DO)
Ammonia (NH3)
Cadmium (Cd)
Potassium (K)
DO Saturation (%)
Nitrate + nitrite as N (NOx as N)
Chromium (Cr)
Magnesium (Mg)
Specific Conductance (µS /cm)
Total Kjeldahl nitrogen (TKN)
Copper (Cu)
Sodium (Na)
pH (s.u)
Total phosphorus (TP)
Iron (Fe)
Sulfates (SO4)
Temperature (°C)
Total suspended solids (TSS)
Manganese (Mn)
Chloride (CI-)
Turbidity
Fecal Coliform
Nickel (Ni)
Alkalinity
Aluminum (AI)
Lead (Pb)
Organic carbon
Antimony (Sb)
Zinc (Zn)
Arsenic (As)
Calcium (Ca)
Water chemistry parameters were also collected for two stormflow events at each monitoring site using automated
samplers. Due to the timing and safety hazards associated with sampling during storm conditions, physical
measurements were not collected during stormflow sampling. Chemical parameters matched those shown in Table 2
7

except for fecal coliform due to issues with submittal hold times. Dissolved metals and organic carbon samples were
field filtered by WQU staff prior to submittal to the laboratory for analysis.
Sediment quality samples were collected on 6/30/2021 as composite samples at all four monitoring sites. At each site,
multiple sediment subsamples were collected using clean plastic sample scoops. Subsamples were collected from
depositional areas where fines were more likely to accumulate within 100 m of the monitoring site. These subsamples
were then composited and homogenized in -field for two minutes before aliquoting for physical and chemical analysis.
Duplicate samples were collected at LC1.1LC for quality control. A field blank for sediment samples was not prepared.
Benthic macroinvertebrate community sampling was conducted at LC1.1LC as part of routine benthic monitoring in the
spring of 2020. 511.6SIC was sampled for benthic macroinvertebrates on 4/8/2021. With a drainage area of 11.94 square
miles located entirely within the Triassic Basin Ecoregion, 511.6SIC was sampled using the Qua14 method [9].
Habitat assessment surveys were conducted by members of WQU on 7/1/2021 at all four monitoring sites and six
additional sites including: one in the Little Brier Creek watershed, two in the Lick Creek watershed, and three in the
Stirrup Iron Creek watershed. Habitat assessment surveys are rapid and subjective assessments of stream conditions in a
given reach on an accumulative score of 1 to 100 across various metrics. All sampling and assessment tasks were
conducted per the study's quality assurance project plan (QAPP). [10]
Deviations from the QAPP
The original sampling location for BC6.6BCTA was chosen to maximize coverage of the watershed within COD city limits.
On 8/27/ 2021, during the first scheduled baseflow sampling event, staff observed indicators of intermittent streamflow
including emergent vegetation, stagnation, and a high concentration of iron -oxidizing bacteria in pools (Figure 2).
Sampling was not conducted at BC6.613CTA on 8/27/2021.
Figure 2 Taken at the original location for BC6.6BCTA, stagnant pools were visible throughout the reach on 812712020.
WQU Staff decided to move the site approximately 500 ft. upstream to an area of sustained flow adjacent to Quate
Industrial Drive and Highway 70. Considering that sampling was never conducted at the original site, the decision was
made to keep the sampling site name with new coordinates (Figure 3). While this new location for BC6.6BCTA was not
sampled on 8/27/2021 due to low flow conditions, all subsequent sampling events were conducted at this new site
location.
M

,148 ft
E
Tamarisk
4511 ft Montaglf
Leesville Rd
Kalmia [)r
Sailfish Ct ni 111 0-
Tee Pee Tri
L
Original Location of BC6.6LBCTA
o Minnu)i
Gaston
Rosedale
70
Franke
�
Fun Fail,
A/C -"a rAj
j,
C,\.b Di
Trrb9Y 1314 Pb 3
Bay
ourc6i: Esri, HERE, Gamin, Intermap, increment Iorp., GEBCO, U 8�s FAOP,
V\ LAPS, KRCAN, GeoBase, IGN, Kaqaster NL, Ordna ce�Survey, Esri Japan,, , METI,
110% t
Esri China (Hong Kong),,(,b) Opei;�!��VM,,a ri tofr� r BF
con ,and the GIS Use'
T community Cr
N
Map prepared byStormwater & GIS Services, Little Brier Creek
Dept. Public Works on 11/10/2021. A
Informationdepicted is for reference purposes only. The Watershed
CITY OF City of Durham assumes no responsibility for the errors 0 0.125 0.25
DURHAM arising from use or misuse of this map. Miles
�eegvWe Rd
Figure 3 Original and New Location of BC6.6BCTA. All samples in this report were collected at the new location. The Original location was never
sampled.
9

Due to the nature of soils found in the Triassic Basin ecoregion, streams are often braided with limited discharge,
particularly during the summer months or after extended periods of dry weather. This made discharge monitoring
difficult, particularly at site BC6.6BCTA, where the flow was estimated by staff to be <0.01 cubic feet per second (CFS)
during two sampling events.
Multiple attempts were made to capture the two storm events concurrently at all sites using automated samplers,
however, equipment failure frequently occurred. Additionally, a storage box used to house equipment at LC2.ORBC was
removed by unknown parties and never located. As a result, sampling was completed with automated samplers when
possible. Staff manually sampled LC2.ORBC using a bridge pole sampler for both sampling events. All sites were sampled
twice during this study.
Field staff were unable to safely access the habitat assessment site designated as LC3 in the QAPP. The decision was
made to not survey this site as part of the habitat assessments. Staff did note elevated turbidity during baseflow
conditions on this day, and a possible sediment and erosion issue was referred to the Durham County Soil Erosion
Control Program for further investigation.
Weather
The KRDU weather station was selected for precipitation monitoring due to proximity to all sampling sites. This weather
station is maintained by the North Carolina State Climate Office at RDU. Based on total annual precipitation data, 2020
was the second wettest year from 2011 to 2021 with a total of 55.3 inches (in). This was second only to 2018 when total
precipitation equaled 60.3 in.
Based on drought monitoring conducted by the National Integrated Drought Information System, (Figure 4) [11]
abnormally dry conditions were observed briefly at the beginning of August 2020, before the start of baseflow sampling.
Abnormally dry conditions were observed again beginning in May 2021, coinciding with final baseflow samples.
Moderate drought conditions preceded stormflow, sediment, and habitat assessment sampling events conducted during
June 2021.
Severity and Percent Area of Drought Conditions in Durham County,
July 2020 to July 2021
100%
90%
80%
70%
60%
Q 50%
40%
30%
20%
10%
0%
Month
❑O- Abnormally Dry ■ D1- Moderate Drought
Figure 4 Drought Conditions for the County of Durham during the study period 2020-2021.
Monthly rainfall totals mirror drought conditions and are shown in Figure 5. A maximum monthly precipitation total of
8.3 in. was recorded in August 2020, and a minimum of 0.6 in. was recorded in March 2021. From September 17-18,
10

2020 the remnants of Hurricane Sally passed through the region. During these two days, the weather station at KRDU
measured 2.2 in. of rainfall over the course of 34 hours. This storm flow event was captured by automated samplers
deployed by the WQU at some sites.
Monthly total precipitation, August 2020 to June 2021
10
9
8
c� 7
Z17-
c 6
0
m 5
a 4
V
a
3
2
0 ■ ,
titi
���,� ��et oar ��e�• ��ei, ��a� �a��
Q ye��e pie �e �a Ikev
� Q
Month
Figure 5 Monthly total precipitation at KRDU during the study period, August 2020 to June 2021.
Water Quality Sampling Results
Sampling conducted by WQU staff was based on a seasonal approach to best capture representative conditions
throughout the year. A total of four baseflow sampling events were conducted at all four monitoring sites. Two
stormflow events were also captured at each sampling site, however not all storm sampling was conducted concurrently
at all sites. Results for baseflow and stormflow sampling are further discussed below.
Baseflow Water Quality Sampling
Minimum, maximum, and median values are below in Table 3 for baseflow sampling results. Fecal coliform minimum,
maximum, and geometric mean values are below in Table 4.
11

Table 3 Baseflow monitoring results, Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
BC6.6LBCTA
LC1.1LC
LC2.01113C
511.6SIC
Parameters
min
max
median
min
max
median
min
max
median
min
max
median
Physical Measurements
Conductivity, µS/cm3
366
435
405
164
266
189
146
221
190
140
250
156
Dissolved Oxygen, mg/L
7.4
11.7
8.1
6.2
12.4
9
5.4
11.9
9
5.2
12.4
9.3
DO Saturation, %
70
91
74
73
96
84
65
95
83.5
54
113
90
pH, s.u.
6.6
7.1
6.8
6.4
7.5
6.6
6.3
7.0
6.5
6.7
7.6
7.0
Temperature, °C
4.7
15.4
9.2
4.6
24.2
12.7
5.8
24.2
12.8
4.8
28
12.9
Turbidity, NTU
12.7
49.1
28
6.0
74.9
20.6
9.4
13.5
11.2
12.1
79.0
51.2
Nutrients
Ammonia Nitrogen, mg/L
ND
0.12
0.09
ND
0.082J
0.05
0.07 J
0.15
0.08
ND
0.07 J
0.05
Nitrate + Nitrite as N, mg/L
0.04 J
0.20
0.08
0.06 J
0.28
0.13
0.04J
0.08 J
0.07
0.06 J
0.88
0.24
Total Kjeldahl Nitrogen, mg/L
0.56
0.78
0.60
0.32 J
0.46 J
0.45
0.52
0.68
0.56
0.50
0.69
0.61
Total Phosphorus, mg/L
ND
0.16
0.13
0.02 J
0.17
0.06
ND
0.07 J
0.05
0.04 J
0.09 J
0.08
Total Suspended Solids, mg/L
11.0
45.0
32.0
ND
40.5
8.6
ND
6.8
4.8
6.8
17.0
11.8
Metals
Aluminum, µg/L
386
861
624
70J
635
328
89
607
226
324
955
546
Dissolved Aluminum, µg/L
49 J
407
241
ND
645
200
ND
471
80
81 J
900
504
Antimony, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Antimony, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Cadmium, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Cadmium, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Chromium, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Chromium, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
1.43 J
1.40
Copper, µg/L
ND
ND
ND
ND
3.7 J,J7
1.6
ND
3.2 J,J7
1.6
6.6 J
10.9
8.5
Dissolved Copper, µg/L
ND
ND
ND
ND
3.8 J,J7
1.6
ND
3.2 J,J7
1.6
5.0 J
9.8 J
6.5
Iron, µg/L
1,770
3,480
1,860
1,060
1,705
1,233
1,200
2,460
1,415
599
1,180
922
Dissolved Iron, µg/L
528
1,740
1,190
251
1,425
443
386
1,620
837
247
922
503
Lead, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Lead, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Manganese, µg/L
222
605
288
149
1,014
304
251
1,420
347
48
218
64
Dissolved Manganese, µg/L
224
266
262
147
977
306
246
1,420
329
42
223
60
Nickel, µg/L
ND
ND
ND
ND
ND
ND
ND
2.8 J
2.2
ND
ND
ND
Dissolved Nickel, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Zinc, µg/L
5.4 J
14.8
6.1
ND
ND
ND
ND
ND
ND
ND
7.9 J
5.8
Dissolved Zinc, µg/L
ND
6.6 J
4.4
ND
ND
ND
ND
ND
ND
ND
ND
ND
Hardness, mg as CaCO3/L
111 J7
135
132
54
104
70
45
76
65
46
77
51
Alkalinity, mg as CaCO3/L
110
120
120
44
99
58
43
68
52
40
71
53
Ions
Calcium, µg/L
30,100.17
34,500
33,500
14,700
28,600
18,600
12,200
21,600
17,950
12,750
21,050
14,350
Chloride, mg/L
33.0
49.0
47.0
11.0
23.0
12.0
9.0
14.0
10.2
8.3
27.0
11.7
Magnesium, µg/L
8,860
11,900
11,700
4,230
7,990
5,752
3,470
5,510
4,810
3,440
5,820
3,775
Potassium, µg/L
2,020
2,990
2,220
1,310
2,790
2,122
4,610
8,780
6,200
1,705
3,100
2,442
Sulfate, mg/L
11.0
19.0
15.0
4.2 J
7.1
5.1
3.5 J
6.8
5.6
4.1 J
7.3
4.8
Sodium, µg/L
25,300 J7
37,000
33,200
10,210 J7
18,750
11,650
8,870
12,600
11,250
%300 J7
19,050
12,950
Organic Carbon
Total Organic Carbon, mg/L
3.8
14.0
8.2
5.0
8.3
6.2
6.6
9.1
8.0
5.7
9.0
6.9
Dissolved Organic (DOC), mg/L
3.6
13.0
7.5
4.3
8.1
6.0
6.1
9.2 J7
7.8
4.9
9.1
7.4
ND- Sample was analyzed for, but not detected above the method report limit (MRL).
J- The reported value is between the Laboratory method detection limit (MDL) and the MRL.
J7- Blank contamination evident, value may not be accurate.
Table 4 Baseflow monitoring results for fecal coliform, Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
BC6.6LBCTA
LC1.1LC
LC2.01113C
S11.6SIC
Parameter
min max geomean
min max geomean
min max geomean
min max geomean
Fecal Coliform, CFU/100 mL
34 800 100
205 1,100 225
145 2,450 1,220
300 4,350 329
12

Relatively higher values for conductivity, total phosphorus (TP), total suspended solids (TSS), aluminum (Al), hardness,
alkalinity, and the majority of the ion parameters were observed at BC6.6BCTA when compared to other monitoring
stations in this study. Turbidity values greater than 50 NTU were observed at 511.6SIC (79 NTU) on 8/27/2020. Elevated
turbidity was also observed at LC1.1LC (75 NTU) and 511.6SIC (72 NTU) on 11/18/2020. No precipitation was recorded in
the preceding five days before either sampling event. Sampling conducted on 11/18/2020 occurred during a period that
was characterized by the highest observed discharges during the study and followed leaf out which may have caused in
higher turbidity values in both watersheds. Maximum fecal coliform concentrations exceeded 400 CFU/100 mL at all
four sites. Maximum values were observed on 8/27/2020 at LC1.1LC, LC2.ORBC, and 511.6SIC. Fecal coliform
concentrations greater than 2,000 CFU/100 mL were reported on 8/27/2020 and 5/20/2021 at LC2.ORBC. An exceedance
of the state standard for hardness in Class WS-IV waters (100 mg as CaCO3/Q was observed at LC1.1LC on 11/18/2020
with a reported concentration of 104 mg as CaCO3/L. Hardness remained below this standard in all other sampling
conditions.
Metals concentrations measured during baseflow in this study were largely unremarkable except for copper and
aluminum. Antimony (Sb), arsenic (As), cadmium (Ccl), and lead (Pb) were not detected in total or dissolved fractions at
any of the study sites during baseflow sampling. Dissolved chromium (Cr) was detected and qualified at S11.6SIC in one
sample on 8/27/2020 at 1.43 µg/L, J. A J-qualified result indicates that the reported value is between the MDL and MRL,
and may not be accurate. Furthermore, this value was part of a duplicate sample split, and dissolved chromium was not
detected in the paired sample. Results as compared to State water quality standards (WQS, Table 5), the Environmental
Protection Agency's (EPA) Biotic Ligand Model (BLM), and the EPA's Total Aluminum Aquatic Life Model are further
discussed below [12] [13].
Table 5 North Carolina surface water quality hardness- dependent metals standards calculations for acute and chronic levels.
Parameter
Calculation Used
Cadmium, acute
WER'*[11.136672-[In hardness](0.041838)1*e^{0.9151[In hardness]-3.14851]
Cadmium, chronic
WER*[{1.101672-[In hardness](0.041838)1*e^{0.7998[ln hardness]-4.44511]
Chromium III, acute
WER*[0.316*e^{0.8190[In hardness]+3.72561]
Chromium III, chronic
WER*[0.860*eA10.8190[In hardness]+0.68481]
Copper, acute
WER*[0.960*eA10.9422[In hardness]-1.7001]
Copper, chronic
WER*[0.960*eA10.8545[in hardness]-1.7021]
Lead, acute
WER*[{1.46203-[In hardness] (0.145712)1*eAll .273[In hardness]-1.4601]
Lead, chronic
WER*[11.46203-[In hardness] (0.145712))*eAll .273[In hardness]-4.7051]
Nickel, acute
WER*[0.998*eA10.8460[In hardness]+2.2551]
Nickel, chronic
WER*[0.997*eA10.8460[In hardness]+0.05841]
Zinc, acute
WER*[0.978*eA10.8473[In hardness]+0.8841]
Zinc, chronic
WER*[0.986*e^{0.8473[in hardness]+0.8841]
1- WER- Water Effects Ratio
Total and dissolved copper (Cu) was not detected in any sample at BC6.6BCTA during baseflow conditions. As Table 6
below shows, concentrations remained below limits at LC1.1LC and LC2.ORBC. exceedances of the hardness -dependent
Cu concentrations for Class C waters were observed at both the acute and chronic levels at 511.6SIC during the baseflow
sampling conducted in August and November of 2020. Additionally, the criteria continuous concentration (CCC) of the
BLM was exceeded in March 2021 at this site. The total Al CCC for aquatic life was also exceeded at LC1.1LC and 511.6SIC
in November, 2020, and at all sites in March, 2021, but the criteria maximum concentration (CIVIC) was not exceeded at
any site during this study.
13

Table 6 Ratios of baseflow sample concentrations to North Carolina State Standards or EPA Aquatic Life Criteria for select metals.
BC6.6LBCTA
LC1.1LC
LC2.ORBC
S11.6SIC
Parameter
8/20 11/20 3/21
5/21
8/20
11/20 3/21
5/21
8/20
11/20 3/21
5/21
8/20
11/20
3/21
5/21
Dissolved
WQS- Acute
-1 - -
-
-
- -
-
-
- -
-
-
-
-
-
Cadmium
WQS- Chronic
- - -
-
-
- -
-
-
- -
-
-
-
-
-
Dissolved
WQS- Acute
- - -
-
-
- -
-
-
- -
-
<0.01
-
-
-
Chromium
WQS- Chronic
- - -
-
-
- -
-
-
- -
-
0.04
-
-
-
WQS- Acute
- - -
-
0.3
- -
-
0.3
- -
-
1.5
1.0
0.6
0.6
Dissolved
WQS- Chronic
- - -
-
0.5
- -
-
0.5
- -
-
2.1
1.4
0.9
0.9
Copper
EPA- BLM
- - -
-
0.77
- -
-
0.52
- -
-
0.53
0.79
1.11
0.72
Dissolved
WQS- Acute
- - -
-
-
- -
-
-
- -
-
-
-
-
-
Nickel
WQS- Chronic
- - -
-
-
- -
-
-
- -
-
-
-
-
-
Dissolved
WQS- Acute
- - -
-
-
- -
-
-
- -
-
-
-
-
-
lead
WQS- Chronic
- - -
-
-
- -
-
-
- -
-
-
-
-
-
Dissolved
WQS- Acute
- - -
<0.01
-
- -
-
-
- -
-
-
-
-
-
Zinc
WQS- Chronic
- - -
<0.01
-
- -
-
-
- -
-
-
-
-
-
Total
EPA Aquatic Life CIVIC
- 0.2 0.3
0.2
0.1
0.5 0.5
<0.01
0.1
0.2 0.7
<0.01
0.1
0.5
0.4
0.2
Aluminum
EPA Aquatic Life CCC
- 0.8 1.2
0.6
1 0.2
1.1 1.3
0.1
0.2
0.6 1.4
0.1
0.5
1.6
1.2
0.5
1-Ratios were not calculated for metals when results were reported as not detected.
14

Stormflow Monitoring Results
Stormflow sampling was completed over three distinct precipitation events on 9/18/2020, 6/2/2021, and 6/20/2021.
Remnants of Hurricane Sally passed through the area of study from 9/17-9/18/2020. Automated samplers successfully
triggered at three of four sites; BC6.613CTA, LC1.11-C, and S11.6SIC during this storm event. Level loggers failed to record
stage data so best professional judgment was used to select representative samples from the storm for composition.
Hourly rainfall and sample bottles composited for each site are shown below in Figure 6.
Stormflow Sampling Times with Hourly Precipitation, 9/17- 9/18/2020
[0167
0.4
- 0.3
0
:U ♦ ■ ♦ ■
a0.2 ■ ♦ BC6.6BCTA
d ♦
■ S11.6SIC
0.1 ■ ■ ■ LC1.1LC
01 1 11I 1 .1 _�_ ■ _
-_ o°o°o°o°o°o°o°o°o°o°o°o°o°o°( .61S9('<_ S9(9(96cPo°
o� oC �°. . by b, N. ti`'. ti(6. op �C6. ti0i. ti°' titi tip' ti'' o° oti oy o� o° o`'lb\o° A'- o� aC). tio
,,g, �ti�1�gl���olti����ti��°lti��gl����lti����ti��°lti��olti���lti����ti��°1���olti����,�'�, �"� a�'*' ''$, �tiy �"I� ��'*Y ''*Y �ti1'11 ����1��lp
Date & TI me
Figure 6 Stormflow sampling times (symbols) and hourly rainfall totals (blue bars), 9117-911812020.
Precipitation data from KRDU recorded a total of 1.8 in. on 6/2/2021. Automated samplers were deployed at three sites,
and field staff sampled LC2.ORBC manually. The County of Durham transitioned from "abnormally dry' to "moderate
drought" conditions in early June (Figure 4). Field notes indicated that all study sites were experiencing low flow
conditions. These conditions were most significant upstream of LC2.ORBC (Figure 7). The stream gage deployed at
LC2.ORBC was placed in a pool which maintained standing water even during low flow conditions. This resulted in a
muted response to the rain event (Figure 9). On the following day field staff recorded a stage of 0.47 ft., close to the
peak flow of 0.50 ft. observed on 6/2/2021. Automated samplers completed sampling at BC6.613CTA and S11.6SIC, but
failed at LC1.11-C. Stage graphs and samples used in composites for successfully sampled sites are shown below in Figure
8,Figure 9, and Figure 10.
15

Figure 7 Facing upstream of LC2.ORBC on 0610212021.
Stage at BC6.6 BCTA, 06/02/2021
2.0
1.8
1.6
1.4
1.2
1.0
a
p 0.8
0.6
0.4
0.2
0.0
■ Samples
,�° °° ,�O 00 '>iO 00 'i° 00 30 °O 30 °O "�° °° •`'�° o°
y4i y�o• y�o• y1• ti1• tip• tip• ,S6i,yoi.�0• .10• ��. ��. ��. rye. '13
Time
Figure 8 Stage and sample times at BC6.6BCTA, 61212021.
16

Stage at LC2.ORBC, 6/2/2021
0.6
0.5
0.4
■ Samples
'OPP
Time
Figure 9 Stage and sample times at LC2.ORBC, 61212021.
Stage at S11.6S1C, 6/2/2021
3.0
2.5
Of
4=
1.5
a�
1.0
0.5
■ Samples
0.0
Ti me
Figure 10 Stage and sample times at S11.651C, 61212021.
A third stormflow sampling event occurred on 6/20/2021. Samples were collected at LC1.11-C and LC2.ORBC where
equipment failure on previous sampling attempts had occurred. KRDU reported a total rainfall of 1.28 in. on 6/20/2021,
with an hourly total of 0.59 in. measured from 10:00 to 11:00 am. An automated sampler was deployed again at
LC1.11-C, while LC2.ORBC was sampled by WQU staff manually using a bridge pole sampler. The precipitation on
6/20/2021 began during setup at LC1.11-C. Because of the delay initial stage rise was not recorded by the deployed depth
loggers or sampled by the automated sampler. As with the sampling on 6/2/2021 low flow conditions were observed at
LC2.ORBC. Low flow conditions resulted in a muted response in the hydrographs again. Two storm peaks were observed
in stage data at LC1.11-C. Two samples were used from this second stage increase to provide adequate volume for
composition. The stage and times of samples that were composited are shown below in
Figure 11 and Figure 12.
17

Stage at LC1.1LC, 6/20/2021
3.0
2.5
2.0
a
1.5
a�
1.0
0.5
0.0
12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00
Time
0.5
0.4
0.3
4=
t
a�
❑ 0.2
0.1
Figure 11 Stage and sample times at LC1.1LC, 612012021.
Stage at LC2.6RBC, 6/20/2021
ov 3v ov
Time
Figure 12 Stage and sample times at LC2.ORBC, 612012021.
■ Samples
■ Samples
18

Results for stormflow sampling are shown below in Table 7. In general, higher concentrations of nitrate + nitrite as N
(NO,,), total Kjeldahl nitrogen (TKN), TP, and TSS were observed in stormflow concentrations compared to baseflow
medians. Minor increases in ammonia were also observed. Chloride concentrations slightly above baseflow medians
were reported at LC1.1LC and LC2.ORBC. Potassium concentrations above baseflow medians were reported at
BC6.613CTA and LC1.11-C. In general, other ion concentrations showed signs of dilution in stormflow conditions. Metals
parameters showed increased concentrations at all four sites when compared to median values from baseflow
monitoring. Of note is the increase in both dissolved and total Cu concentrations at BC6.613CTA and SI1.6SIC when
compared to baseflow conditions. While Pb was not detected in baseflow sampling, total Pb concentrations were
reported at BC6.613CTA, LC1.1LC, and SI1.6SIC during storm events. Metals concentrations compared to hardness -
specific water quality standards are further discussed below in Table 8.
19

Table 7 Stormflow monitoring results, Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
BC6.6BCTA
LC1.1LC
LC2.0RBC
S11.6SIC
Parameter
9/18/20
6/02/21
9/18/20
6/20/21
6/02/21
6/20/21
9/18/20
6/02/21
Nutrients
Ammonia Nitrogen, mg/L
0.12 J7
0.07 J
0.01 J,J7
ND
0.11
0.05 J
0.09 J,J7
0.04 J
Nitrate + Nitrite as N, mg/L
0.19
0.46
ND
0.08 J
0.17
0.75
ND
0.21
Total Kjeldahl Nitrogen, mg/L
1.30
1.70
1.30
0.50
1.55
0.75
0.83
1.30
Total Phosphorus, mg/L
0.41
0.65 J7
0.36
0.11 J7
0.79 J7
0.10 J7
0.15
0.33 J7
Total Suspended Solids, mg/L
100
460
230
55
130
71
125
540
Metals
Aluminum, µg/L
1,670
2,930
1,020
283
508
288
1,129
1,120
Dissolved Aluminum, µg/L
543
ND
623
ND
ND
ND
492
ND
Antimony, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Antimony, µg/L
ND
ND
ND
ND
NO
ND
ND
ND
Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Cadmium, µg/L
ND
ND
ND
ND
ND
ND
ND
0.41
Dissolved Cadmium, µg/L
ND
ND
ND
ND
0.4J,J7
ND
ND
ND
Chromium, µg/L
2.7 J
2.4 J
1.5 J
ND
ND
ND
1.5 J
ND
Dissolved Chromium, µg/L
ND
ND
1.6 J
ND
ND
ND
ND
ND
Copper, µg/L
12.0
21.4
7.7 J,J7
ND
ND
ND
23.1
39.2
Dissolved Copper, µg/L
7.6 J,17
5.0 J
6.1 J,17
ND
ND
ND
16.8
8.7 J
Iron, µg/L
2,300
7,300
1,260
915
3,135
1,670
1,046
2,040
Dissolved Iron, µg/L
654
62
749
34 J
132
141
464
73
Lead,µg/L
ND
7.34J
3.14J
ND
ND
ND
3.18J
4.15J
Dissolved Lead, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Manganese,µg/L
132
972
198
302
1,115
783
123
567
Dissolved Manganese, µg/L
17
28
70
99
745
471
32
12
Nickel, µg/L
ND
5.7 J
2.3 J
ND
ND
ND
ND
2.4 J
Dissolved Nickel, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Zinc, µg/L
39.2
180
10.8
5.7 J
9.8 J
5.11
28.2
53.3
Dissolved Zinc, µg/L
11.8
11.5
4.9 J
ND
ND
ND
14.6
4.8 J
Hardness, mg as CaCO3/L
15
53
33
72
53
50
30
31
Alkalinity, mg as CaCO,/L
ND
28
ND
71
43
53
16
22
Ions
Calcium, µg/L
8,060
13,500
8,490
19,500
15,500
14,400
8,250
8,600
Chloride, mg/L
5.1
10.0
6.3
14.0
12.0
8.6
5.8
8.2
Magnesium, µg/L
2,480
4,760
2,750
5,540
3,520
3,360
2,200
2,310
Potassium, µg/L
3,550
3,740
3,240
2,370
3,185
4,270
2,230
2,110
Sulfate, mg/L
5.6
6.8
3.9 J
4.1 J
3.7 J
3.6 J
4.5 J
3.9 J
Sodium, µg/L
6,310
9,860
5,900
11,600
7,595
8,140
6,015
6,700
Organic Carbon
Total Organic Carbon, mg/L
8.8
6.5
14.0
7.0
7.6
7.3
7.5
6.0
Dissolved Organic Carbon, mg/L
9.4
5.1
14.0
6.6
6.7
6.7
7.8
5.7
ND- Sample was analyzed for, but not detected above the method report limit (MRL).
J- The reported value is between the Laboratory method detection limit (MDL) and the MRL.
J7- Blank contamination evident, value may not be accurate.
20

Table 8 Ratios of stormflow sample concentrations to North Carolina State Standards for select metals.
BC6.6LBCTA
LC1.1LC
LC2.ORBC
S11.6SIC
Parameter
9/18/20 6/2/21
9/18/20 6/20/21
6/2/21 6/20/21
9/18/20 6/2/21
Dissolved WQS- Acute
1
- -
- -
- -
Cadmium WQS- Chronic
-
1.4
Dissolved WQS- Acute
0.01
-
Chromium WQS- Chronic
0.05
- -
Dissolved WQS- Acute
3.3 0.7
1.3
3.9 1.9
Copper WQS- Chronic
4.2 1.0
1.8
5.3 2.6
Dissolved WQS- Acute
- -
-
- -
Nickel WQS- Chronic
Dissolved WQS- Acute
Lead WQS- Chronic
- -
-
- -
Dissolved WQS- Acute
0.5 0.2
0.1
0.3 0.1
Zinc WQS- Chronic
0.5 0.2
0.1
0.3 0.1
1- Ratios were not calculated for metals when results were reported as not detected.
Ratios for observed concentrations in stormflow samples when compared to North Carolina State standards were
calculated. Dissolved Cu above acute and chronic thresholds were observed on 9/18/2020 at BC6.6BCTA, LC1.1LC, and
S11.6SIC, and on 6/2/2021 at S11.6SIC. Copper was not detected in any baseflow samples at BC6.6BCTA, but total or
dissolved fractions of Cu were reported during both storm events above chronic or acute toxicity levels. Dissolved Cd
concentrations above the chronic hardness -specific water quality standard were observed at LC2.ORBC on 6/2/2021. It
should be noted that the reported concentration was J and J7 qualified, indicating both blank contamination and an
elevated MRL with the laboratory, and therefore reported concentrations may not be accurate. Because physical
parameters were not collected during stormflow conditions the BLM for dissolved Cu and Aquatic Life CIVIC and CCC for
total Al were not calculated. Higher concentrations of total aluminum above maximum reported concentrations in
baseflow conditions were observed at BC6.6BCTA, LC1.1LC, and S11.6SIC, indicating possible exceedances of CIVIC and
CCC levels during stormflow conditions.
Sediment Quality Sampling Results
Sediment samples for physical and chemical analyses were collected on 6/30/2021 at all four monitoring sites. Results
for physical and chemical analyses are discussed below.
Physical Analysis
Results from the physical analysis of the sediment samples showed all sites had predominantly silty -sandy soils with a
majority (50% or more) of various grades of sands. S11.6SIC showed higher levels of fines, porosity, and natural moisture,
indicating higher levels of organic particulate matter compared to other study sites (Table 9).
21

Table 9 Physical properties of soil samples collected on 613012021 for the Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
Parameter
BC6.6BCTA
LC1.1LC
LC2.0RB
S11.6SIC
Bulk density, g/mL
1.3
1.3
1.3
1.0
Porosity, %
51
50
53
62
Natural Moisture, %
32.1
28.7
40.1
101.3
Fine Gravel, %
0.2
0.0
0.2
0.0
Coarse sand, %
0.3
0.1
0.3
0.0
Medium Sand, %
16.7
18
32.6
7.2
Fine Sand, %
62.4
68.2
48.4
55.3
Fines( Silt or Clay), %
20.4
13.8
18.5
37.5
Chemical Parameter Results
Concentrations for select metals and PAHs are shown below (Table 10). In general, higher metal concentrations were
reported at S11.6SIC when compared to other study sites with the exception of Mn, where higher concentration were
reported at LC2.ORBC. Antimony (Sb), As, and Cd were not detected in sediment at any of the sampling sites. PAHs were
observed at all four sites in sediment samples. Highest concentrations of total PAHs and most individual parameters
were observed at BC6.613CTA, with the exception of Anthracene, which was only detected at LC2.ORBC. Anthracene was
also the only detected PAH at LC2.ORBC. Naphthalene was not detected at any site during sampling. Relatively higher
concentrations of PAHs were detected at both BC6.61-13CTA and S11.6SIC. As previously noted, both of these sampling
sites are located in areas with more mixed and industrial land use when compared to LC1.1LC and LC2.ORBC. Pavement,
pavement sealant (especially coal -tar -based pavement sealant), and tires are noted as potential sources of PAHs [14).
Table 10 Chemical parameter concentrations in sediment, 613012021. Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
Parameter
BC6.6LBCTA
LC1.1LC
LC2.0RBC
S11.6SIC
Total Organic Carbon, mg/kg
5,600
5,650
6,600
10,000
Metals
Aluminum, mg/kg
2,350
1,805
2,610
4,280
Antimony, mg/kg
ND
ND
ND
ND
Arsenic, mg/kg
ND
ND
ND
ND
Cadmium, mg/kg
ND
ND
ND
ND
Chromium, mg/kg
2.58
3.12
3.37
5.42
Copper, mg/kg
4.34
1.78
2.66
18.50
Iron, mg/kg
4,170
3,575
5,580
5,900
Lead, mg/kg
2.45
2.36
3.21
5.30
Manganese, mg/kg
82
169
305
194
Nickel, mg/kg
2.59 J
1.64
2.16 J
4.12
Zinc, mg/kg
18.10
6.69
10.10
31.30
PAHs
Anthracene, mg/kg
ND
ND
0.050
ND
Benzo(a)anthracene, mg/kg
0.3501
ND
ND
0.1401
Benzo(a)pyrene, mg/kg
0.450
ND
ND
0.1901
Benzo(g,h,i)perylene, mg/kg
0.250
ND
ND
0.120 J
Chrysene, mg/kg
0.530
ND
ND
0.240 J
Fluoranthene, mg/kg
0.840
0.056
ND
0.4401
Ideno(1,2,3-cd)pyrene, mg/kg
0.210 J
ND
ND
0.1001
Naphthalene, mg/kg
ND
ND
ND
ND
Phenanthrene, mg/kg
0.270 J
0.040
ND
0.200 J
Pyrene, mg/kg
0.630
0.048
ND
0.320 J
Total PAHs, mg/kg
1 3.530
0.388
1 0.050
1.750
ND- Sample was analyzed for, but not detected above the method reporting limit (MRL).
J- The reported value is between the Laboratory method detection limit (MDL) and the MRL.
22

In 2019 WQU staff prepared a report summarizing existing stream sediment data from monitoring sites in Durham and
four other surrounding counties (Chatham, Granville, Orange, and Wake) [15]. Summary statistics were prepared for
sediment quality data from 123 sites representing monitoring stations collected by the COD, USGS, and Duke University.
These monitoring sites represented 26 watersheds, and four ecoregions. Summary statistics included minimum,
maximum, and the non -parametric Kaplan -Meier (KM) estimation of population mean and standard deviation (Table
11). Metals and PAH KM means in this historical dataset reported were higher than concentrations measured at all sites
in this study.
Table 11 Minimum, maximum, and Kaplan- Meir Means for select parameters, taken from Summary of Existing Stream Sediment Chemistry Data in
Durham County, NC and Surrounding Counties [151.
Parameter
Minimum
Maximum
KM Mean
KM Std. Dev
Total Organic Carbon, mg/kg
412
1,630,0001
75,022
220,895
Metals
Aluminum, mg/kg
2,360
182,399
34,820
27,220
Antimony, mg/kg
ND
1.3
0.6
0.3
Arsenic, mg/kg
ND
22.0
2.9
3.7
Cadmium, mg/kg
ND
0.50
0.01
0.09
Chromium, mg/kg
0.9
270.0
25.2
31.2
Copper, mg/kg
1.5
258.9
21.0
28.7
Iron, mg/kg
8,300
38,000
18,871
8,696
Lead, mg/kg
1.01
48
12.9
10.1
Manganese, mg/kg
160
3,400
1,212
765
Nickel, mg/kg
ND
60
7.8
8.5
Zinc, mg/kg
4.4
190.0
43.6
37.8
PAHs
Anthracene, mg/kg
ND
13
110
8.1
Benzo(a)anthracene, mg/kg
ND
350
38
56
Benzo(a)pyrene, mg/kg
ND
340
40
56
Benzo(g,h,i)perylene, mg/kg
ND
300
42
44
Chrysene, mg/kg
ND
620
57
97
Fluoranthene, mg/kg
ND
1700
114
248
Ideno(1,2,3-cd)pyrene, mg/kg
ND
270
41.2
41
Naphthalene, mg/kg
ND
25
11
4.5
Phenanthrene, mg/kg
ND
36
26
179
Pyrene, mg/kg
ND
1300
99
209
1- The maximum TOC value provided in the original report may not be accurate and likely affected, mean and standard deviation
calculations. However, these metrics are provided in Table 11 for qualitative comparison to results from Brier Creek, Lick Creek,
and Stirrup Iron Creek that were collected in this study.
Sediment Toxicity Results
As non -polar compounds, PAHs regularly bind to organic material found in sediment under certain conditions. When
complexed to sediment, PAHs are less bioavailable to surrounding organisms. To account for differences in
bioavailability PAH concentrations are standardized to 1% TOC by dividing the reported concentration of a detected PAH
by the percentage of TOC reported in the sample. Furthermore, when pollutants combine with sediment it is difficult to
accurately quantify their potential toxic effects on organisms [16], [17]. Due to this, screening levels cover two ranges;
the Threshold Effect Concentration (TEC) and the Probable Effect Concentration (PEC). The TEC is the level at which a
toxicant is unlikely to affect test organisms, while the PEC is the level at which a toxicant is highly likely to affect a test
organism (Table 12). To account for multiple toxicants at PEC levels, a PEC quotient (PEC-Q) is calculated which is also
normalized to total organic carbon (TOC) levels for non -polar compounds like PAHs [16] using the following formula:
PEC-Q _
Chemical Concentration(dry wt. )
' PEC (dry wt. )
Equation 1 Probable Effect Concentration quotient calculation.
23

Table 12 Threshold Effect (TEC) and Probable Effect (PEC) Concentrations for Metals and PAHs at 1% TOC.
Parameter
TEC (mg/kg) PEC (mg/kg)
Metals
Aluminum (Al)
N/A
N/A
Antimony (Sb)
2
25
Arsenic (As)
9.79
33
Cadmium (Cd)
0.99
4.98
Chromium (Cr)
43.4
111
Copper (Cu)
31.6
149
Iron (Fe)
N/A
N/A
Lead (Pb)
35.8
128
Manganese (Mn)
N/A
N/A
Nickel (Ni)
22.7
48.6
Zinc (Zn)
121
459
PAHs
At 1% TOC
Anthracene
57.2
845
Benzo(a)pyrene
150
1,450
Chrysene
166
1,290
Fluoranthene
423
2,230
Naphthalene
176
561
Pyrene
195
1,520
Benzo(a)anthracene
108
1,050
Benzo(g,h,i)perylene
N/A
N/A
Dibenzo(a,h)anthracene
33.0
N/A
Indenol(1,2,3-cd)pyrene
N/A
N/A
Phenanthrene
204
1,170
TOTAL PAH
1,610
22,800
Samples collected as part of this study had relatively low TOC concentrations, and as noted in [16], this can result in
overprotective screening levels. The converse of this is that reported PAHs are more bioavailable than those bound to
organic matter and therefore may have a greater impact on aquatic life. Corrections for TOC at 1% are not made to
metals results. Calculated ratios to TEC-Q and PEC-Q screening levels for metals concentrations and PAH concentrations
at 1% TOC are shown below in Table 13.
24

Table 13 Ratios to TEC-Q and PEC-Q screening levels in sediment. Brier Creek, Lick Creek, & Stirrup Iron Creek watershed study.
Parameter
BC6.6LBCTA
LC1.11LC
LC2.01113C
S11.6SIC
TEC-Q
PEC-Q
TEC-Q
PEC-Q
TEC-Q
PEC-Q
TEC-Q
PEC-Q
Metals
Antimony
1
Arsenic
Cadmium
Chromium
0.06
0.02
0.07
0.03
0.08
0.03
0.12
0.05
Copper
0.14
0.03
0.06
0.01
0.08
0.02
0.59
0.12
Lead
0.07
0.02
0.07
0.02
0.09
0.03
0.15
0.04
Nickel
0.11
0.05
0.07
0.03
0.10
0.04
0.18
0.08
Zinc
0.15
0.04
0.06
0.01
0.08
0.02
0.26
0.07
PAHs
Anthracene
-
-
-
-
1.32
0.09
-
-
Benzo(a)anthracene
5.79
0.60
-
-
1.30
0.13
Benzo(a)pyrene
5.36
0.55
1.27
0.13
Benzo(g,h,i)perylene
-
-
-
-
Chrysene
5.70
0.73
-
-
1.45
0.19
Fluoranthene
3.55
0.67
0.23
0.04
1.04
0.20
Ideno(1,2,3-cd)pyrene
-
-
-
-
-
-
Naphthalene
-
-
-
-
-
-
Phenanthrene
2.36
0.41
0.35
0.06
0.98
0.17
Pyrene
5.77
0.74
0.44
0.06
-
-
1.64
0.21
Total PAHs
1 3.96
0.28
1 0.33
0.02
1 0.24
0.02
1.12
0.08
1- Ratios were not calculated for metals when results were reported as not detected.
2- PAHs were corrected to 1% TOC prior to calculating ratios.
No exceedances of screening levels were observed in reported metals concentrations at any of the monitoring sites. A
comparatively elevated TEC-Q ratio was observed for Cu at S11.6SIC (0.59), which is notable given the elevated
concentrations of total and dissolved Cu observed at this site in water quality samples collected as part of this study.
Multiple exceedances of TEC threshold levels for individual PAHs, as well as exceedances for total PAHs levels, were
observed at both BC6.6BCTA and S11.6SIC. The TEC screening level for anthracene was exceeded at LC2.ORBC. No
exceedances of PEC screening levels were observed in any samples.
Benthic Macroinvertebrate Community Sampling Results
Benthic samples were collected as part of routine ambient sampling in 2020 at LC1.1LC and as part of this study at
S11.6SIC. Both sites were located in the Triassic Basin Ecoregion, so the Qual 4 sampling method was used as per COD
SOP [9]. Benthic macro invertebrate community assessment results for both are shown below (Table 14). LC1.1LC
received an overall rating of "Good -Fair" with a biotic index score of 5.80. S11.6SIC received a "Poor" rating and a biotic
index score of 6.98. This lower rating indicates a potentially impacted benthic macroinvertebrate community.
Table 14 Benthic m acroin vertebrate community assessment results.
Site Information
Monitoring Results
t
E
m
L
a ",
°_
C�
v
o
E
x
a
x
-0
N
Z
E
bn
vm
0
E
WY /6
(6co
UO
mO!
E
on
�
fX
0
yi
°ai
zN
amn
w
O
H
m
co
Good -
Neuse
Lick
LCIALC
10.8
TB
Qua14
42
156
47
9
5.80
Fair
Neuse
Stirrup Iron
S11.6SIC
11.9
TB
Qua14
52
159
41
6
7.15
Poor
25

Stream Cross Sections and Discharge
Despite relatively consistent rainfall, baseflow discharges remained low during the study period. Flowing water was not
observed at BC6.613CTA on 8/27/2020 so discharge could not be measured. Discharges could also not be collected on
5/20/2021 at three of four sites due to similar low flow conditions. Measured discharges, and summary statistics are
shown below in Table 15. Cross sections were collected as part of baseflow monitoring events. Cross sections are shown
below in Figure 13, Figure 14, Figure 15, and Figure 16.
Table 15 Recorded discharge values during baseflow monitoring events August 2020 to May 2021.
Site Date
Discharge (CFS)
Total Wetted Width (ft.)
8/27/2020
-
-
11/18/2020
0.04
8.6
CO
3/8/2021
0.01
5.0
5/20/2021
-
5.7
CO
Mean
0.02
6.4
SD
0.03
1.6
8/27/2020
0.48
13.9
11/18/2020
3.49
20.4
u
3/8/2021
3.90
18.2
J
5/20/2021
-
3.9
Mean
2.62
14.1
SD
1.52
6.3
8/27/2020
0.03
8.3
U
11/18/2020
0.50
9.1
c
3/8/2021
0.87
9.6
5/20/2021
-
8.3
J
Mean
0.47
8.8
SD
0.34
0.6
8/27/2020
0.02
9.5
11/18/2020
1.54
10.9
3/8/2021
1.01
10.8
5/20/2021
0.06
12.0
Mean
0.66
10.8
SD
0.65
0.9
26

rrr:�r:�:r•�r=►
Distance from Left Bank Monument (ft.)
0 2 4 6 8 10 12 14 16
0
4
6
L
10
5 10
Figure 13 Cross Section measurements at BC6.6BCTA, facing upstream.
LC1.1 LC
Distance from Left Bank Monument (ft.)
15 20 25
...
18 20
30 35 40
Figure 14 Cross section measurements at LC1.1LC, facing upstream.
......••• 1V18/2020
----- 3/8/2021
— • — 5/20/2021
8/27/2020
......••• 1V18/2020
----- 3/8/2021
— • — 5/20/2021
27

0
0 .
2
4
t
6
8
10
0
0
2
4
t
a
6
8
10
LC2.ORBC
Distance from Left Monument (ft.)
5 10 15 20 25
�W V
Figure 15 Cross section measurements at LC2.ORBC, facing upstream.
M,
S11.6SIC
Distance from Left Monument (ft.)
5 10 15 20 25 30 35
— r
Figure 16 Cross section measurements at 511.651C, facing upstream.
8/27/2020
......... 1V18/2020
----- 3/8/2021
— • — 5/20/2021
8/27/2020
......... 1V18/2020
----- 3/8/2021
— • — 5/20/2021
28

Overall, cross sections show a relatively stable bank and channel structure at BC6.6BCTA and LC2.ORBC. Both are incised
and modified channels with relatively well -established and vegetated banks. BC6.6BCTA had a deeply incised channel
that had reached bedrock and had major controlling features including large trees and boulders at the cross section site.
LC2.ORBC cross sections were collected downstream of the roadway, and has extensive manmade stabilization in place.
The channel at LC1.1LC was characterized by steep and undercut banks with little vegetative stabilization. The channel at
this site experienced sediment infill over time. A maximum bankfull depth of 8.29 ft. was recorded at the start of the
study (8/27/2020), and this had decreased to 7.3 ft. by the end of the study (5/20/2021). Moving bed conditions were
observed in areas upstream and downstream of the cross section site at LC1.1LC and the stream was frequently
observed to be braided with recent depositional areas of sediment. 511.6SIC had a large depositional bar that had
converted to a shelf on the right side of the channel, also indicative of depositional sediment. Field notes from routine
ambient monitoring indicate that in March 2019 water levels at 511.6SIC dropped approximately three feet [18]. It is
believed that prior to 2019 a beaver dam downstream had inundated the area around the monitoring site. Evidence of
this inundation extends back to 2013 (Figure 17), and the beaver dam was likely present for at least a decade prior to be
breaching. From 2019 to present stream levels have remained at this lower level (Figure 18).
Figure 17 511.6SIC on 211312013, taken as part of routine ambient monitoring.
IJ

Habitat Assessments
Habitat assessments were performed at the four monitoring sites and at one site in the Little Brier Creek watershed, two
sites in the Lick Creek watershed, and three sites in the Stirrup Iron Creek watershed. Habitat assessments were
performed by a member of the WQU on 7/1/2021. Habitat assessment scores are subjective rankings of overall stream
conditions on a scale of 1-100, with higher scores being "more natural" or healthy. It should be noted that the habitat
assessments were performed during drought conditions, which may have affected ratings. Habitat assessment scores
are shown below in Table 16 and further discussed below.
Table 16 Habitat assessment scores by watershed, 71112021.
Habitat Assessment
Watershed
Site ID
Score
BC6.6LBCTA
46
Brier Creek
LBC1
70
LC1.1LC
56
LC2.ORBC
51
Lick Creek
LC1
44
LC2
66
LC3
N/A1
S11.6SIC
39
SI1
46
Stirrup Iron Creek
SI2
47
SI3
57
1- LC3 was not rated due to unsafe conditions.
30

Brier Creek Watershed
LBC6.6LBTA- Habitat Score: 46
LBC6.6LBTA was characterized as a deeply incised, low flow, urban stream adjacent to Highway 70. The stream enters a
culvert to pass under Highway 70 and receives stormwater runoff from a small, mixed -use industrial watershed. The
survey area extended downstream of this culvert section. Rip -rap was used to stabilize the area around the culvert, but
was mostly absent downstream. Instream habitat was mostly limited to sticks, leafpack, and limited areas with undercut
banks. The substrate was almost homogeneously bedrock, with only one sandy pool adjacent to a stormwater outfall.
Riffle -pool features were almost entirely absent in the reach surveyed, limited to the single pool near the culvert. Banks
were deeply incised and showed evidence of historical erosion, but had mostly stabilized due to mature trees and
vegetation as well as controlling features including exposed bedrock. Canopy coverage was rated as good, with frequent
breaks for sunlight penetration. The riparian zone was relatively intact, but also narrow with Highway70 and an unpaved
parking lot located within twenty yards of the stream.
LBC1- Habitat Score: 70
LBC1 was located adjacent to a large residential development with stormwater control measures. Instream conditions
showed evidence of flashy, high flow including depositional areas of sediment, steep incised banks, and undercutting in
bends. The reach was noted to have characteristics of streams found in both the Triassic Basin and Eastern Slate Belt
Ecoregions including large boulders and fractured features commonly found in Slate Belt streams, and large depositional
pools with unconsolidated sand and sediment similar to those found in the Triassic Basin. The characteristics possibly
indicate that this area is part of the transitional zone between the two ecoregions. Field staff noted that water color was
tannic in nature, possibly the result of higher organic matter loads from the surrounding forest. Sinuosity of the channel
was classified as mostly natural, with frequent bends. Multiple forms of instream habitat were noted in the survey area
and included snags, logs, rootmats, and undercut banks. The bottom substrate was nearly homogenously sand and soft
with the exception of the aforementioned isolated boulders and fracture features found approximately 100 yards
downstream. Pools were frequent and varied, with numerous riffles. Banks showed signs of recent erosion, with steep
angles and unconsolidated exposed soil in some areas. The surrounding riparian zone was dominated by mature trees
with good canopy coverage and a mature forest. Breaks in the riparian zone were rare but included downed trees and a
hiking path adjacent to the creek.
Lick Creek Watershed
LC1.1LC- Habitat Score: 56
LC1.1LC is located in a forested game land owned by the U.S. Army Corps of Engineers. The area surveyed was
characterized by steep incised banks made up of unconsolidated sandy soils. Instream areas exhibited extensive
sediment infill and depositional bar development, with braided and shallow flow. Field staff rated the channel as
natural, but with infrequent bends, possibly indicating historical channelization. Instream habitat consisted of sticks,
leafpacks, snags, and logs. However, during low flow, some of this habitat may not be readily accessible by aquatic
organisms. The bottom substrate consisted almost entirely of unconsolidated sand. Pools were infrequent but did have a
variety of sizes, however, riffles were almost absent with the exception of isolated areas of braided stream. The
surrounding riparian vegetative zone is dominated by mature forest, and extensive, however the banks themselves were
either bare, or had grasses and small shrubs.
LC2.ORBC- Habitat Score: 51
The area surrounding LC2.ORBC was privately owned and moderately forested. The survey area located upstream of the
road crossing featured incised banks, sediment infill of the channel, and depositional bars throughout. Field staff noted
that the channel was natural with frequent bends. Instream habitat included sticks, leafpacks, and a few snags and logs.
The bottom substrate was nearly all sand with some areas of unconsolidated fine sediment located in pools. The pools
were relatively infrequent but were of various sizes, while riffles were infrequent and mostly limited to areas with
manmade stabilization around the roadway. The banks were noted as mostly stable, with some erosion present in
meanders. Near bank vegetation was predominately made up of mature trees with a good canopy and frequent breaks.
The riparian zone had frequent breaks including drainage ditches adjacent to the roadway, but was extensive on both
sides.
31

LC1- Habitat Score: 44
LC1 was located upstream of an active sewer easement project along Lick Creek. Both streambanks in the area surveyed
were heavily incised and showed signs of significant erosion, with subsiding banks and recent depositional bars.
Instream habitat was sparse and limited to sticks, leafpack, snags, and logs. The bottom substrate was almost uniformly
sand, with infrequent pools located in bends, and only a few riffles. The banks were almost free of vegetation, with only
a few shrubs and grasses present. While the surrounding riparian zone was forested, the banks were relatively open and
canopy coverage was limited. This riparian zone was also relatively wide, but breaks including downed trees and rills in
banks were common.
LC2- Habitat Score: 66
LC2 was located downstream of an active sewer easement project along Doc Nichols Road. Both banks were deeply
incised and depositional bars were noted throughout the survey area. Field staff noted that the channel appeared
natural with frequent bends. Instream habitat was abundant, and included sticks, leafpacks, snags, logs, undercut banks,
and rootmats. The bottom substrate was characterized as being predominantly sand with some areas of exposed
bedrock. Pools and riffles were noted to be frequent and of various sizes. While banks showed signs of extensive erosion
and consisted of unconsolidated sand, the riparian zone consisted of mostly small trees and shrubs near bank, and larger
trees in the floodplain. The canopy cover was rated as good, with some breaks present for light penetration. While the
riparian zone was dominated by trees and wide, breaks were frequent due to unconsolidated soils and downed trees.
LC3-Habitat Score: N/A
LC3 was not rated due to unsafe conditions at the site. Staff noted elevated turbidity at the road crossing and referred
these conditions to Durham County Soil Erosion Control Program for further investigation.
Stirrup Iron Creek Watershed
S11.6SIC- Habitat Score: 39
S11.6SIC was located upstream of Chin Page Road and showed historical signs of beaver activity downstream including
water marks roughly two feet above current stream high watermarks. The creek near the roadway showed signs of
channelization although it does appear to be returning to natural meanders over time. The left bank floodplain included
a sewer easement. Instream habitat consisted of mostly sticks and leafpacks with undercut banks and rootmats also
present in the reach. The bottom substrate was homogenous and consisted of sand. Pools were infrequent with near -
uniform depth in the reach. Riffles were present but infrequent and small. Tree canopy coverage was minimal, with a
majority of the stream located in full sun at the time of survey. Portions of the bank had subsided due to undercutting in
some areas. Bank vegetation was dominated by shrubs and grasses on the left bank, and small trees and shrubs on the
right. The riparian zone had some breaks including cut drainage ditches but was relatively wide.
S11- Habitat Score: 46
S11 was located on a tributary to Stirrup Iron Creek adjacent to industrial facilities located along TW Alexander Drive. The
survey area consisted of the stream that flowed under TW Alexander Dr through a culvert which then braided into a
wetland area before returning to a single stream roughly 0.25 miles downstream. Field staff noted deeply incised banks,
over -bank deposits and bar development in the stream, indicating frequent high flows and erosion. Staff also noted
areas of bank failure present throughout the survey area. The channel was characterized as natural with frequent bends.
Instream habitat was noted as sparse and limited to undercut banks and rootmats. The bottom substrate was nearly all
sand, with some exposed areas of bedrock in scour zones. Pools and riffles were relatively infrequent and limited in size.
Canopy coverage was rated as relatively good due to the presence of large trees and the riparian zone was relatively
wide. However, breaks due to stream bank failure and erosional rills were frequent.
32

512- Habitat Score: 47
SI2 was also located off of TW Alexander Drive. on a tributary to Stirrup Iron Creek which includes a small reservoir in
Lake Shore. Stream banks were deeply incised and undercut. The channel was noted as natural with infrequent bends,
possibly from historical channelization. Instream habitat consisted of rocks, macrophytes, snags, logs, and undercut
banks. Water was slightly turbid, and field staff noted surface blue-green algae rafted near a log, most likely discharged
from the small reservoir upstream. The bottom substrate was predominantly silt or clay. Pools were infrequent but
varied in size while riffles were practically absent. Banks were mostly stable with erosion confined to meanders and bank
vegetation was mostly small trees. The riparian zone was wide and dominated by large trees with good canopy and
frequent breaks for light, but breaks were common on both banks.
513- Habitat Score: 57
S13 was located on a small tributary upstream and adjacent to Roche Drive. Field staff noted extensive channelization
and stabilization with manmade riprap at the culvert with the appearance of a channelized ditch. However, areas
located upstream of the culvert exhibited a natural channel with frequent bends. Instream habitat in this area was also
relatively extensive for such a small stream and included sticks, leafpacks, snags, logs, and abundant undercut banks and
rootmats with attached periphyton. The bottom substrate was noted as nearly all sand, with limited areas of
consolidated clay. Pools were infrequent but varied in size. Culvert that had been installed led to inundation in the area,
causing riffles to be almost completely absent. Banks were noted as relatively stable, with erosion confined mostly to
meanders. Bank vegetation was mostly small trees and shrubs apart from a few large trees in the floodplain which
provided good canopy and frequent breaks for light penetration. Field staff noted distinct differences between the left
and right banks, while the left bank had frequent breaks with a narrow width and a steep slope to Roche Drive, while the
right bank contained no breaks and featured an extensive forested floodplain.
Conclusions
Monitoring sites BC6.6BCTA, LC1.1LC, and S11.6SIC showed geomorphology typical of flashy, urban, Triassic Basin
streams with deeply incised banks, signs of erosion during high flow, and low discharge during baseflow. Elevated
turbidity was observed at LC1.1LC and 511.6SIC during baseflow winter samples and may be a result of instream
conditions typical of those found in Triassic Basin streams including unconsolidated or readily erodible soil at the
streambank. LC2.ORBC has a smaller watershed than LC1.1LC and 511.6SIC and is less developed than all three of the
other monitoring sites. Stormflow stage graphs for LC2.ORBC reflected relatively less urban land cover with less flashy
peaks in discharge, and streambank erosion that was less severe.
As noted in Table 4, the fecal coliform geometric mean of 1,220 CFU/100 mL at LC2.ORBC was the highest of the four
sites. While the small sample size is not conclusive, historically elevated fecal coliform concentrations were associated
with discharges from AFOs located upstream. Although these operations are believed to have ceased in 2015 [19], an
elevated fecal coliform geomean detected in this study may warrant further investigation. Annual geometric means for
fecal coliform at LC2.ORBC collected as part of routine monitoring from 2016-2020, the period following closure of the
AFO, ranged from 357 to 607 CFU/100 mL [18], lower than the calculated geomean from this study. Elevated fecal
coliform was also observed at LC1.1LC, but remained in line with annual geometric means from 2010-2020 which ranged
from 97- 936 CFU/100 mL [18]. At 511.6SIC from 2010-2019 fecal coliform geomeans ranged from 71 to 1318 CFU/100
mL, with values that consistently increased from 2011-2019 when a geomean of 1318 CFU/ 100 mL was observed [18].
This was initially noted in the study QAPP [10], however the fecal coliform geomean was 329 CFU/100 mL during this
study (Table 4), and reported as 658 CFU/100mL in routine ambient monitoring for 2021. These values do not continue
the upward trend observed, but remain elevated. As previously noted, maximum fecal coliform concentrations
exceeded 400 CFU/100mL at all four sites during the study.
Physical parameters at all four sites remained within recommend screening limits at all four sites. Relatively low DO was
frequently noted to occur at 511.6SIC from May to October based on reviews of routine ambient data conducted prior to
this study, and noted in the QAPP [10]. However, DO remained above levels of concern at all sites during this study.
33

Copper concentrations above water quality screening limits and standards were observed during baseflow and
stormflow samples at 511.6SIC. This may be related to related to roadway runoff, industry, or legacy pollution. Concern
about copper levels in 511.6SIC is further supported by a "poor' benthic macro invertebrate community rating and the
highest ratio for copper toxic threshold effect concentrations in sediment of the four monitoring sites. Dissolved
cadmium that was above the TEC was observed once at LC2.ORBC during stormflow water quality samples on 6/2/2021,
though results were qualified and dissolved Cd was not detected in other water or sediment quality samples at this site.
The single elevated hardness concentration reported at LC1.1LC (104 mg as CaCO3/L) exceeded all maximum reported
values (74-88 mg as CaCO3/L) from 2010- 2019 reported as part from routine ambient monitoring [18]. While noted in
this study, baring future exceedances of the standard during routine monitoring it is not believed to be a parameter of
concern at this time.
Multiple PAHs were detected in concentrations above TECs at BC6.6BCTA and 511.6SIC. BC6.6BCTA has a relatively small
watershed, predominantly made up of mixed -use industrial facilities that include a high concentration of parking lots
and roadways. PAHs are a product of combustion and are found in vehicle exhaust as well as pavement sealers and
asphalt. Land use in the Stirrup Iron Creek watershed is also predominantly developed with some industrial usage
upstream, so sources for PAHs could potentially be similar in the BC6.6BCTA and 511.6SIC watersheds. Anthracene was
detected above the TEC at LC2.ORBC in sediment samples and was the only PAH detected at this site. as previously
noted, samples collected as part of this study had relatively low TOC concentrations which can result in overprotective
screening levels.
Habitat assessments scores ranged from 39 to 70 in the study watersheds. The habitat assessment gives higher marks
for natural streams with established riffle -pool features and rocks or cobble substrate in natural forests or undeveloped
areas. Triassic Basin streams typically score lower even in relatively untouched areas due to the surrounding geology,
which erodes into a predominantly sandy or silty bottom substrate. Triassic Basin streams are also subject to low flows
and flashy conditions due to the relatively low infiltration rates of surrounding soils. Habitat assessment scores for the
Stirrup Iron Creek watershed ranged from 39 to 57 with low rankings for incised banks with evidence of erosion, both of
which are indicative of impacts from flashy urban stormwater runoff. Habitat scores in the Lick Creek watershed ranged
from 44 to 66, again signs of erosion, including depositional infilling which resulted in the loss of the riffle -pool structure,
and homogenous sandy bottom substrates were reasons listed for lower scores. In the Little Brier Creek watershed,
habitat assessment scores were 46 and 70. LBC1 was rated higher for riffle -pool features and an abundance of good
habitat including snags, logs, rootmats, and undercut banks. However, deeply incised banks at both sites in the
watershed were noted for reduced scores. Overall, habitat scores are reflective of urbanized stream conditions
prevalent throughout the area, compounded with the natural erodibility of Triassic Basin soils.
34

References
[1] City of Durham, "City of Durham Stormwater Management Plan Permit Number NCS000249," 1 January 2019.
[Online]. Available: https://durhamnc.gov/DocumentCenter/View/33415/SWMP-2018-final-small. [Accessed 1
October 2021].
[2] City of Durham, Public Works Department, Internal GIS layers, Durham: City of Durham, 2015.
[3] Multi -resolution Land Characteristics Consortium, "Data," 2 5 2019. [Online]. Available: https://www.mrlc.gov/.
[Accessed 15 12 2019].
[4] NCDOT, "U.S. 70 Improvements at Brier Creek Parkway & T.W. Alexander Drive," NCDOT, 16 February 2021.
[Online]. Available: https://www.ncdot.gov/projects/us-70-brier-creek/Pages/default.aspx. [Accessed 30 October
2021].
[5] NRCS, "Web Soil Survey," 9 May 2019. [Online]. Available: https://websoilsurvey.nres.usda.gov/app/. [Accessed 15
December 2019].
[6] Stormwater & GIS Services, Water Quality Unit, "Standard Operating Procedures for Field Measurements and
Observations," City of Durham, Durham, 2020.
[7] Stormwater & GIS Services, Water Quality Unit, "Standard Operating Procedures for Water Chemistry Sampling,"
City of Durham, Durham, 2020.
[8] Stormwater & GIS Services, Water Quality Unit, "Procedure for Determining Wadable Stream Discharge with Hand-
held Current Meters Standard Operating Procedures," City of Durham, Durham, 2008.
[9] Stormwater & GIS Services, Water Quality Unit, "Standard Operating Procedures for Benthic Macroinvertebrate
Community Monitoring," City of Durham, Durham, 2022.
[10] Stormwater & GIS Services, Water Quality Unit, "Brier Creek, Lick Creek, and Stirrup Iron Creek Watershed Study
(Project 20-002) Quality Assurance Project Plan," City of Durham, Durham, 2020.
[11] NIDIS, "Drought Conditions for Durham County," National Integrated Drought Information System, [Online].
Available: https://www.drought.gov/states/north-carolina/county/Durham. [Accessed 30 August 2021].
[12] United States Environmental Protection Agency, "Copper Biotic Ligand Model," EPA, 2007. [Online]. Available:
https://www.epa.gov/wqs-tech/copper-biotic-Lgand-model. [Accessed 01 August 2020].
[13] United States Environmental Protection Agency, "Aquatic Life Criteria - Aluminum," EPA, 2018. [Online]. Available:
https://www.epa.gov/wgc/aquatic-life-criteria-aluminum. [Accessed 8 August 2021].
[14] Agency for Toxic Substances and Disease Registry, "Polycyclic Aromatic Hydrocarbons (PAHs)," 1 September 1996.
[Online]. Available: https://www.epa.gov/sites/default/files/2015-04/documents/walter_atsdr_pahs.pdf.
[Accessed 1 October 2021].
[15] Stormwater & GIS Services, Water Quality Unit, "Summary of Existing Stream Sediment Chemistry Data in Durham
County, NC and Surronding Counties," City of Durham, Durham, 2020.
[16] C. M. D. W. N. e. a. Ingersoll, "Prediction of Sediment Toxicity using Consensus- Bases Freshwater Sediment Quality
Guidelines. EPA 905/R-00/007," US environmental Protection Agency, Great Lakes National Program Office, 2000.
[17] D. I. C. B. T. MacDonald, "Development and Evaluation of Consensus -Based Sediment Quality Guidelines for
Freshwater Ecosystems.," Archives of Environmental Contamination and Toxicology, vol. 39, pp. 20-31, 2000.
[18] Stormwater & GIS Services, Water Quality Unit, "Durham Water Quality Web Portal," City of Durham, Public
Works, 1 January 2021. [Online]. Available: http://www.durhamwaterquality.org/. [Accessed 1 August 2021].
[19] Stormwater & GIS Services, Water Quality Unit, "Manure Spill Summary for Rocky Branch Creek in the Lick Creek
Watershed in Durham County, North Carolina," City of Durham, Durham, 2019.
35

Appendix I Baseflow Monitoring Data
BC6.6LBCTA
LC1.1LC
Parameters
11/18/2020
3/8/2021
5/20/2021
8/27/2020
11/18/2020
3/8/2021
5/20/2021
Nutrients
Ammonia Nitrogen, mg/L
6.8 U
ND
0.011
0.06 J
0.05 U, J
ND
0.08 J
Nitrate + Nitrite as N, mg/L
0.05 J
0.08 J
0.2
0.16
0.09 J
0.28
0.06 J
Total Kjeldahl Nitrogen, mg/L
0.78
0.6
0.56
0.45 J
0.44 J
0.321
0.455 J
Total Phosphorus, mg/L
0.16
ND
0.13
0.17
0.011
0.03 J
0.03 J, U
Total Suspended Solids, mg/L
32.0
11.0
45.0
ND
40.5
10.0
7.1
Metals
Aluminum, µg/L
624
861
386
145
634.5
511
70.15 J
Dissolved Aluminum, µg/L
407
49.21
241
63.7 J
644.5
337
ND
Antimony, µg/L
ND
ND
ND
ND
ND
ND
ND
Dissolved Antimony, µg/L
ND
ND
ND
ND
ND
ND
ND
Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
Dissolved Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
Cadmium, µg/L
ND
ND
ND
ND
ND
ND
ND
Dissolved Cadmium, µg/L
ND
ND
ND
ND
ND
ND
ND
Chromium, µg/L
ND
ND
ND
ND
ND
ND
ND
Dissolved Chromium, µg/L
ND
ND
ND
ND
ND
ND
ND
Copper, µg/L
ND
ND
ND
ND
ND
ND
ND
Dissolved Copper, µg/L
ND
ND
ND
ND
ND
ND
ND
Iron, µg/L
1,860
1,770
3,480
1,060
1,705
1,310
1,155
Dissolved Iron, µg/L
1,190
528
1,740
251
1,425
578
308
Lead, µg/L
ND
ND
ND
ND
ND
ND
ND
Dissolved Lead, µg/L
ND
ND
ND
ND
ND
ND
ND
Manganese,µg/L
288
222
605
382
226
149
1,014
Dissolved Manganese, µg/L
262
224
266
384
227
147
977
Nickel, µg/L
ND
ND
ND
ND
ND
ND
ND
Dissolved Nickel, µg/L
ND
ND
ND
ND
ND
ND
ND
Zinc, µg/L
5.38J
6.1J
14.8
ND
ND
ND
ND
Dissolved Zinc, µg/L
ND
ND
6.61 J
ND
ND
ND
ND
Hardness, mg as CaCO3/L
111.6
135.2
131.8
82.9
57.3 J7
54.1
104.3
Alkalinity, mg as CaCO3/L
120.0
120.0
110.0
61.0
55.5
44.0
99.0
Ions
Calcium, µg/L
30,100 J7
34,500
33,500
22,000
15,200 J7
14,700
28,600
Dissolved Calcium, µg/L
30,100 J7
35,500
32,900
22,300
15,200 J7
14,700
28,600
Chloride, mg/L
33
49
47
11
12
12
23
Magnesium, µg/L
8,860
11,900
11,700
6,800
4,705
4,230
7,990
Dissolved Magnesium, µg/L
8,910
12,100
11,400
6,930
4,745
4,270
7,995
Potassium, µg/L
2,990
2,020
2,220
2,790
2,345
1,310
1,900
Dissolved Potassium, µg/L
2,920
1,980
2,160
2,900
2,355
1,340
1,880
Sulfate, mg/L
11
15
19
4.2 J
5.2
7.1
5.0
Sodium, µg/L
25,300 J7
33,200
37,000
12,500
10,210
10,800
18,750
Dissolved Sodium, µg/L
25,300 J7
33,800
36,600
12,800
10,300 J7
11,000
18,800
Organic Carbon
Total (TOC), mg/L
14
8.2
3.8
7
8.3
5.4
4.95
Dissolved (DOC), mg/L
13
7.5
3.6
7.3 J7
8.1
4.6
4.25
Fecal Coliform, CFU/100mL
800
35
100
1,100
205
230
220
Field Parameters
Specific Conductance, µS/cm at 25' C
366
435
405
205
172
164
266
Dissolved Oxygen, mg/L
8.1
11.7
7.4
6.2
9.9
12.4
8.1
Dissolved Oxygen Saturation, %
70
91
74
73
83
96
85
pH
6.6
6.8
7.1
6.6
6.5
6.4
7.5
Temperature, °C
9.2
4.7
15.4
24.2
8.1
4.6
17.3
Turbidity, NTU
28.0
12.7
49.1
6.0
74.9
32.7
8.6
36

LC2.ORBC
SI1.6SIC
Parameters
8/27/2020
11/18/2020
3/8/2021
5/20/2021
8/27/2020
11/18/2020
3/8/2021
5/20/2021
Nutrients
Ammonia Nitrogen, mg/L
0.07 J
0.08 J
R
0.15
ND
0.05 J
0.05 U, J
0.07 J
Nitrate + Nitrite as N, mg/L
0.07 J
0.081
0.07 J
0.05 J
0.88
0.31
0.06 J
0.16
Total Kjeldahl Nitrogen, mg/L
0.54
0.52
0.58
0.68
0.64
0.58
0.495
0.69
Total Phosphorus, mg/L
ND
0.07
ND
0.07 J
0.09 J
0.07 J
ND
0.04 J
Total Suspended Solids, mg/L
3.7
6.8
ND
5.9
9.6
14
6.8
17
Metals
Aluminum, µg/L
121.0
330.0
607.0
88.6 J
389.0
955.0
702.5
324.0
Dissolved Aluminum, µg/L
78.21
81.4 J
471.0
ND
230.5
778.0
899.5
81.3 J
Antimony, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Antimony, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Arsenic, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Cadmium, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Cadmium, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Chromium, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Chromium, µg/L
ND
ND
ND
ND
1.43 U, J
ND
ND
ND
Copper, µg/L
3.21 J, J7
ND
ND
ND
10.85
8.32 J
8.66 J
6.55 J
Dissolved Copper, µg/L
3.17 J, J7
ND
ND
ND
9.845 J
6.37 J
6.685 J
4.99 J
Iron, µg/L
1,420
1,410
1,200
2,460
599
1,180
873
970
Dissolved Iron, µg/L
386
678
995
1,620
337
922
669
247
Lead, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Dissolved Lead, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Manganese,µg/L
438
255
251
1,420
48
58
70
218
Dissolved Manganese, µg/L
410
248
246
1,420
42
54
67
223
Nickel, µg/L
ND
ND
ND
2.76J
ND
ND
ND
ND
Dissolved Nickel, µg/L
ND
ND
ND
ND
ND
ND
ND
ND
Zinc, µg/L
ND
ND
ND
ND
ND
5.04J
ND
7.89J
Dissolved Zinc, µg/L
ND
ND
ND
ND
6.495 U, J
ND
ND
ND
Hardness, mg as CaCO3/L
75.4
54.7 J7
44.8
75.8
46.0
47.017
76.5
55.8
Alkalinity, mg as CaCO3/L
68.0
51.0
43.0
52.0
39.5
44.0
62.5
71.0
Ions
Calcium, µg/L
21,100
14,800 J7
12,200
21,600
12,750
12,800 J7
21,050
15,900
Dissolved Calcium, µg/L
20,900
14,800 J7
12,000
21,000
12,600
12,200 J7
21,100
15,400
Chloride, mg/L
9.3
11.0
9.0
14.0
8.3
9.3
27.0
14.0
Magnesium, µg/L
5,510
4,300
3,470
5,320
3,440
3,650
5,820
3,900
Dissolved Magnesium, µg/L
5,500
4,280
3,400
5,110
3,380
3,510
5,830
3,780
Potassium, µg/L
8,780
6,860
5,540
4,610
2,715
3,100
1,705
2,170
Dissolved Potassium, µg/L
8,690
6,880
5,490
4,380
2,655
2,990
1,765
2,160
Sulfate, mg/L
5.3
5.8
6.8
3.51
4.81
4.8 J
7.3
4.1 J
Sodium, µg/L
12,600
10,000 J7
8,870
12,500
13,100
9,300 J7
19,050
12,800
Dissolved Sodium, µg/L
12,500
10,100 J7
8,760
12,500
13,000
9,170 J7
19,250
12,900
Organic Carbon
Total (TOC), mg/L
9.1
9.1
6.9
6.6
5.9
9.0
8.0
5.7
Dissolved (DOC), mg/L
9.2 J7
9.1
6.5
6.1
R
9.1
7.4
4.9
Fecal Coliform, CFU/100mL
2,450
145
440
2,000
4,350
300
355
304
Field Parameters
Specific Conductance, µS/cm at 250
202
177
146
221
140
141
250
170
Dissolved Oxygen, mg/L
5.4
10.6
11.9
7.4
8.8
9.8
12.4
5.2
Dissolved Oxygen Saturation, %
65
91
95
76
113
83
97
54
pH
6.6
6.4
6.3
7.0
7.6
6.8
6.7
7.1
Temperature, °C
24.2
8.6
5.8
17
28
8.3
4.8
17.5
Turbidity, NTU
13.5
12.1
10.4
9.4
79.0
72.2
31.5
12.1
37