I-31_Draft Report - Sandy Creek Tributary A

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DRAFT REPORT I Prepared for
City of Durham Department of Public Works
Pollutant Source Tracking and
Improvement Opportunities -
Sandy Creek Tributary A
February 25, 2022

DRAF-
Pollutant Source Tracking
and Improvement
Opportunities - Sandy
Creek Tributary A
Prepared for
City of Durham
North Carolina
February 25, 2022

DRAFT
Pollutant Source Tracking and Improvement Opportunities -
Sandy Creek Tributary A
Prepared for
City of Durham, North Carolina
February 25, 2022
This is a draft and is not intended to be a final representation
of the work done or recommendations made by Brown and Caldwell.
It should not be relied upon; consult the final report.
Brown ANn
Caldwell '
5430 Wade Park Boulevard, Suite 200
Raleigh, NC 27607
T: 919.233.9178

Table of Contents
Listof Figures.............................................................................................................................................. iv
Listof Tables............................................................................................................................................... vi
Listof Abbreviations...................................................................................................................................vii
ExecutiveSummary...................................................................................................................................viii
1. Introduction
.......................................................................................................................................1-1
2. Baseline Data Review.......................................................................................................................2-1
2.1
Watershed Characteristics and Potential Sources...............................................................2-1
2.2
Water Quality Data..................................................................................................................2-6
2.2.1 2009-2020 Ambient Monitoring Data....................................................................2-6
2.2.2 2017 City Investigations..........................................................................................2-6
3. Investigative Methods.......................................................................................................................3-1
3.1
Stream Condition Assessment...............................................................................................3-1
3.1.1 Visual Assessment of Channel Condition...............................................................3-1
3.1.2 Characterization of Streambed Sediments............................................................3-1
3.1.3 Streamflow Measurement.......................................................................................3-2
3.2
Longitudinal Field Parameter Survey....................................................................................3-2
3.3
Water Quality Sampling..........................................................................................................3-5
3.4
Thermal Imaging.....................................................................................................................3-7
3.5
Survey of Upper Drainage Area..............................................................................................3-9
3.5.1 Visual Inspection......................................................................................................3-9
3.5.2 On -Site Testing.......................................................................................................
3-10
3.5.3 Water Quality Sampling.........................................................................................
3-10
3.6
Microbial Source Tracking...................................................................................................
3-10
4. Results of Field Investigations.........................................................................................................4-1
4.1
Stream Condition Assessment...............................................................................................4-1
4.2
Field Parameter Survey.......................................................................................................4-21
4.3
Water Quality Sampling.......................................................................................................
4-21
4.3.1 Ionic Composition..................................................................................................4-24
4.3.2 CBOD5 and Carbon...............................................................................................
4-24
4.3.3 Iron and Manganese.............................................................................................4-27
4.3.4 Nutrients................................................................................................................
4-27
4.3.5 Other Indicators.....................................................................................................4-27
4.4
Thermal Imaging..................................................................................................................4-27
4.4.1 Findings in Sandy Creek Tributary A.....................................................................
4-27
4.4.2 Lessons for Broader Application..........................................................................
4-32
4.5
Survey of Upper Drainage Area...........................................................................................4-34
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4.6 Microbial Source Tracking...................................................................................................4-41
5. Summary of Pollutant Sources and Causes....................................................................................5-1
5.1 External Pollutant Sources.....................................................................................................5-1
5.2 Stream Morphology and Processes.......................................................................................5-3
5.2.1 Hydrologic Characteristics.......................................................................................5-3
5.2.2 Water Quality Processes..........................................................................................5-4
5.2.3 Summary of Conceptual Model...............................................................................5-5
6. Recommended Improvement Strategies.........................................................................................6-1
6.1 Addressing Known Pollutant Sources....................................................................................6-1
6.2 Potential In -Stream Projects..................................................................................................6-1
6.2.1 Priority 2/Priority 3 Stream Restoration.................................................................6-4
6.2.2 Forced Riffle Enhancement.....................................................................................6-4
6.2.3 Cost Opinion..............................................................................................................6-5
6.3 Other MS4 Control Measures................................................................................................6-6
6.3.1 Public Education and Outreach...............................................................................6-7
6.3.2 Public Involvement...................................................................................................6-7
6.3.3 Illicit Discharge Detection and Elimination.............................................................6-8
6.3.4 Construction Site Run-Off........................................................................................6-8
6.3.5 Post -Construction Runoff.........................................................................................6-8
6.3.6 Pollution Prevention and Good Housekeeping for Municipal Operations.............6-9
6.3.7 Program to Monitor and Control Pollutants.........................................................
6-10
6.3.8 Water Quality Assessment and Monitoring..........................................................
6-10
6.3.9 Total Maximum Daily Load (TMDL) Programs .....................................................
6-10
7. References........................................................................................................................................7-1
AppendixA: Data Catalog.........................................................................................................................A-1
8. Data Catalog......................................................................................................................................A-2
9. Water Quality Pollutant.....................................................................................................................A-2
10. Source Tracking.................................................................................................................................A-2
SANDY CREEK TRIBUTARY A............................................................................................................A-2
Appendix B: Field Parameter Survey Results......................................................................................... B-1
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List of Figures
Figure 1-1. Sandy Creek Tributary A study area and City of Durham water quality sampling location. 1-
2
Figure 2-1. Approximate watershed area (as delineated by USGS StreamStats) and land use
characteristics - Sandy Creek Tributary A........................................................................................ 2-2
Figure 2-2. Potential point sources including stormwater and sewer infrastructure ...........................
2-3
Figure 2-3. Historic topographical map and imagery showing appearance and location of sewage
disposalfacility in 1993.....................................................................................................................2-4
Figure 2-4. Locations of IDDE investigations in the watershed from 1996-2020,
includingdates of SSOs.....................................................................................................................
2-5
Figure 2-5. Monthly average DO concentration and DO saturation at station NH1.7SCTA, 2009-2020.
.............................................................................................................................................................2-6
Figure 3-1. Locations of cross -sections evaluated on October 5, 2020...............................................
3-3
Figure 3-2. Longitudinal field parameter survey conducted on October 5, 2020................................
3-4
Figure 3-3. Grab samples collected October 6-7, 2020 in Sandy Creek Tributary A ............................3-6
Figure 3-4. Thermal image locations in Sandy Creek Tributary A and upper drainage area . ..............
3-8
Figure 3-5. Upper drainage area DWS survey and sample locations .................................................
3-11
Figure 4-1. Observations from stream assessments (Martin Luther King Jr Parkway to Ivy Creek
Boulevard) ...........................................................................................................................................4-2
Figure 4-2. Bank erosion and large pool features holding stagnant water downstream of Martin
LutherKing Jr. Parkway......................................................................................................................4-3
Figure 4-3. Example of impervious area directly adjacent to areas of bank instability ........................4-4
Figure 4-4. Observations from stream assessments (Ivy Creek Boulevard to University Drive) ..........
4-5
Figure 4-5. Stagnant water upstream of University Drive......................................................................
4-6
Figure 4-6. Stream conditions near University Drive facing downstream . ............................................
4-6
Figure 4-7. Stream conditions near University Drive facing upstream..................................................4-7
Figure 4-8. Observations from stream assessments (University Drive to Garrett Road) . ....................
4-8
Figure 4-9. Examples of bank instability, sand bars, and shifting stream morphology between
University Drive and Garrett Road.....................................................................................................4-9
Figure 4-10. Example of debris dam between University Drive and Garrett Road ............................
4-10
Figure 4-11. Example of Stream widening and sediment aggradation between University Drive and
GarrettRoad . ...................................................................................................................................
4-11
Figure 4-12. Stabilized stream banks upstream of Garrett Road .......................................................
4-12
Figure 4-13. Observations from stream assessments (Garrett Road to confluence with Sandy Creek).
..........................................................................................................................................................
4-13
Figure 4-14. Example of stream channel widening and sediment aggradation downstream of Garrett
Road.................................................................................................................................................
4-14
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Table of Contents
Figure 4-15. Example of bank erosion and channel incision downstream of Garrett Road .............
4-15
Figure 4-16. Example of the iron -oxidizing bacteria observed at multiple locations along Sandy Creek
TributaryA........................................................................................................................................
4-16
Figure 4-17. Aerial sewer line crossing.................................................................................................4-17
Figure 4-18. Example of stormwater drainage into stream upstream of Ivy Creek Blvd ...................
4-18
Figure 4-19. Evidence of flooding and erosion near sewer manholes ...............................................
4-19
Figure 4-20. Measured specific conductance and calculated streamflow estimates along Sandy
Creek Tributary A, October 5, 2020...............................................................................................
4-22
Figure 4-21. Measured dissolved oxygen concentrations and calculated streamflow estimates along
Sandy Creek Tributary A, October 5, 2020....................................................................................
4-23
Figure 4-22. Water quality results for Sandy Creek Tributary A, October 6-7, 2020.........................
4-26
Figure 4-23 - Left bank image at site 2, showing relatively uniform water temperatures and the lack
of visible seepage plumes..............................................................................................................
4-28
Figure 4-24 - Right bank image at site 1, showing cooler water near bank .....................................
4-29
Figure 4-25 - Left bank photo at site 34, showing cooler water near bank ......................................
4-29
Figure 4-26 - Right bank photo at site 10, showing seep in bank .....................................................
4-30
Figure 4-27 - Left bank photo at site 22, showing seep....................................................................
4-30
Figure 4-28 - Groundwater -fed pool on right bank at 29. Sandy sediments separated this pool from
the main channel flow except for a small connect channel.........................................................
4-31
Figure 4-29 - Plume of water entering the main channel of Sandy Creek Tributary 1 from the
groundwater -fed pool on the right bank at site 29.......................................................................
4-31
Figure 4-30 - Image from site 3, showing effect of differential shading ...........................................
4-33
Figure 4-31 - Right bank of site 1. Example of picture -in -picture mode from ...................................
4-33
Figure 4-32. Observations and sampling sites from the DWS............................................................
4-35
Figure 4-33. Suspected sewage observed in stormwater manhole (Site B)......................................
4-36
Figure 4-34. Suspected water main break (Site H). ............................................................................
4-37
Figure 4-35. Dumpster leachate flowing into tributary to Sandy Creek Tributary A ..........................
4-38
Figure 4-36. HF183 gene marker versus fecal coliform concentration .............................................
4-41
Figure 48. Priority 1 Restoration (Courtesy North Carolina Stream Restoration Institute and North
CarolinaSea Grant)............................................................................................................................6-2
Figure 49. Priority 2 Restoration (Courtesy North Carolina Stream Restoration Institute and North
CarolinaSea Grant)............................................................................................................................6-3
Figure 6-1. Priority 3 Restoration (Courtesy North Carolina Stream Restoration Institute and North
CarolinaSea Grant)............................................................................................................................6-3
Figure 6-2. Schematic of reducing width of stream bed to create baseflow riffle channel . ................
6-5
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Table of Contents
List of Tables
Table 3-1. Summary of Major Field Investigations.................................................................................3-1
Table 3-2. Sites investigated in Sandy Creek Tributary A and upper drainage area ............................ 3-9
Table 4-1. Flow Estimates and Stream Observations along Sandy Creek Tributary A, October 5, 2020
.......................................................................................................................................................... 4-20
Table 4-2. Field Parameter Results at Grab Sample Locations in Sandy Creek Tributary A ............. 4-24
Table 4-3. Laboratory Results for Sandy Creek Tributary A Grab Samples ........................................ 4-25
Table 4-5. Sites Investigated in Sandy Creek Tributary A and upper drainage area ......................... 4-34
Table 4-6. Grab Sample Results and Field Parameters......................................................................4-40
Table 4-7. On -Site Testing Results....................................................................................................... 4-40
Table 5-1. Screening -Level Streeter Phelps DO Sag Calculation..........................................................5-1
Table 5-2. Inferred Water Quality Processes in Sandy Creek Tributary A..............................................5-4
Table 6-1. Opinion of Probable Total Project Costs for Restoration......................................................6-5
Table 6-2. Opinion of Probable Total Project Costs for Forced Riffles...................................................6-6
Table B-1. Field Parameter Results from the October 5, 2020 Stream Survey - Sandy Creek Tributary
A (downstream to upstream)............................................................................................................ B-2
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Table of Contents
List of Abbreviations
AST
above ground storage tank
BMP
best management practice
BOD5
five-day biochemical oxygen demand
CAPP
Critical Area Protection Plan
CBOD5
carbonaceous biochemical oxygen
demand
cfs
cubic feet per second
cfu
colony forming unit
City
City of Durham
cm
centimeter
CS
cross -sectional
DI
deionized
DO
dissolved oxygen
DOC
dissolved organic carbon
DWM
Department of Water Management
DWS
dry weather screening
EPA
U.S. Environmental Protection Agency
ESC
erosion control
fps
feet per second
GIS
geographic information system
GPS
Global Positioning System
IDDE
illicit discharge detection and elimination
m
meter
MBAS
methylene blue active substances
MCL
maximum contaminant level
MDL
method detection limit
meq
milliequivalents
mg/L
milligrams per liter
mL
milliliter
mS
milliSiemens
MS4
municipal sanitary storm sewer system
MST
microbial source tracking
my
millivolt
NCDOT
NC Department of Transportation
NO2+3
nitrite -plus nitrate nitrogen
NTU
nephelometric turbidity unit
OPCC
Opinion of Probable Construction Cost
PIP
picture inside picture
PO4
orthophosphate
QAPP quality assurance project plan
SMP Stormwater Management Plan
SSO sanitary sewer overflow
s.u.
standard units
TKN
total Kjeldahl nitrogen
TMDL
Total Maximum Daily Load
TOC
total organic carbon
TP
total phosphorus
TRI
Toxics Release Inventory
TSS
total suspended solids
USGS
U.S. Geological Survey
UST
underground storage tank
WLA
wasteload allocations
vii
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Executive Summary
Water quality monitoring by the City has demonstrated low dissolved oxygen (DO) concentrations and
elevated bacteria concentrations in Sandy Creek Tributary A (station NH1.7SCTA). The area of
concern extends about one mile along Sandy Creek Tributary A from a point where a storm drainage
network daylights at Martin Luther King Jr. Parkway to downstream of Garrett Road. Evaluation of
historical water quality and mapping data did not indicate a primary cause of the low DO
concentrations. In 2020, the City's Stormwater and Geographic Information System (GIS) Services
Division of the Public Works Department engaged Brown and Caldwell to perform a field
investigation of the causes of low DO and other water quality issues. The overall project approach
included the following activities for Sandy Creek Tributary A:
A desktop review of water quality data, watershed characteristics, and potential pollutant
sources
Various field investigations to identify sources and causes of water quality problems
Identification of water quality improvement strategies.
Baseline Data Review: Sandy Creek Tributary A drains an area of about 1.8 square miles (mi2). A
notable characteristic of this drainage area is the high degree of developed land uses, including
large commercial developments and associated impervious surfaces in the upper drainage area. A
sanitary gravity main runs parallel to Sandy Creek Tributary A for its entire exposed length, and the
sewer crosses the tributary in several locations. Although some sanitary sewer overflows and other
illicit discharges have sometimes occurred in the watershed, the watershed has no toxic release
inventory (TRI) sites, industrial point sources, or municipal operations facilities.
A review of the historical monitoring data demonstrated that DO concentrations were highly variable
in Sandy Creek Tributary A but often fell below 4 milligrams per liter (mg/L) in the summer and
sometimes below 2 mg/L. DO percent saturation values were 50 to 80 percent even in most cooler
months. Fecal coliform was variable but often very high, with a median value of 980 colony forming
units per 100 milliliters (mL). Limited investigations by the City concluded that no source of pollution
could be found to explain the in stream measurements. This conclusion was a motivation for
performing the present investigation.
Field Investigations: Two rounds of field investigations were performed for this study, one in early fall
2020, and the other in early fall 2021. The field investigations included the elements discussed
below.
• A stream condition assessment found many of the common characteristic of streams with higher
impervious drainage areas and high rates of urban runoff. These include eroding banks,
channelization, and segments of low velocity/stagnation. Base flows to the channel are very low
due to natural conditions of Triassic basin streams, exacerbated by a highly impervious
watershed.
Water quality sampling confirmed low DO and elevated bacteria concentrations in the stream.
The DO was already relatively low (<4 mg/L) at the stream daylight point and continued to
decrease, reaching concentrations of less than 1 mg/L throughout much of the stream length.
Carbonaceous biological oxygen demand (CBODS) and ammonia were relatively low at most
locations, but ammonia was above background levels at the stream daylight point. There was
little algal growth in the stream. Other chemical characteristics included high iron and
viii
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Executive Summary
manganese and persistently high turbidity (100-150 Nephelometric Turbidity Units [NTU])
despite relatively low total suspended solids concentrations.
A thermal imaging study concluded that most groundwater inputs to the stream were low in
magnitude and relatively diffuse. Few discrete seeps were observed. But the study confirmed
that segments of the stream receive inputs of low -DO groundwater. These are most obvious as
marginal, relatively stagnant areas with iron -reducing bacteria. The water in these areas flows
slowly into the main channel of the creek.
An investigation of the upper drainage area revealed several external pollution sources to the
stream, including a sewer leak, a water main break, pet waste, and a leaking dumpster. A high
proportion of the stormwater sewer sites that were investigated had evidence of dry weather
flows.
Microbial source tracking samples resulted in widespread detection of the human marker,
HF193, confirming sewer leaks as a source of bacteria and oxygen demand to Sandy Creek
Tributary A. However, pet waste and wildlife sources were also concluded to be important
sources of bacteria to the creek.
Summary of Pollutant Sources and Causes: Based on the results of the field investigation, the
project concluded that low DO and other water quality issues in Sandy Creek are caused by
(1) external pollution to the stream; and (2) in -stream hydrologic conditions. Screening -level
calculations demonstrated that —due to the very low baseflows in the stream —sewer leaks or other
sources of oxygen demand could cause DO concentrations to fall below 4 mg/L, without necessarily
causing high CBOD5 concentrations in the stream. The impact of external pollution and low baseflow
rates is exacerbated by a low channel gradient and modifications that cause stagnancy and low
reaeration rates. Groundwater inputs to the stream tend to be low in DO and thus do little to aid DO
recovery.
Recommended Improvement Projects: This project resulted in three categories of recommended
improvement projects:
• Elimination of known pollutant sources. This category of potential improvements includes
fixing/eliminating the pollutant sources that were discovered as part of the upper drainage area
investigation of Sandy Creek Tributary A, including the sanitary sewer leak, water main break,
and leaking dumpsters.
• Instream Improvements. In conjunction with reducing external pollution sources, reaeration and
DO could be improved by stream restoration. The recommended project includes a combination
of new floodplain creation, floodplain widening, stream realignment, and bank stabilization. It
would create a narrower baseflow channel as part of the reconfigured cross section for the
stream. By restoring the stream and speeding up the evolutionary process, the pattern and
profile can be manipulated to create a stable stream profile with riffles to produce the higher
velocities or turbulence to increase DO. The restoration could be performed for the entire stream
or in selected segments. As an alternative to complete restoration, the City could perform a more
limited project that would involve removing obstructions and creating riffles at key locations
within the stream.
• Implementation of MS4 Control Strategies and Sewer Inspections. This category of improvement
includes the continued or focused application of ongoing City programs for pollution prevention.
Among the most important control strategies for Sandy Creek Tributary A are:
o Maintenance of the pollution reporting hotline and other means to allow the public to
identify potential pollutant sources.
o The illicit discharge and detection program, including dry weather screening to detect sewer
leaks and other pollutant sources.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Executive Summary
Sewer inspections and maintenance, including camera inspections and follow-up
maintenance.
Post -construction runoff controls that would make hydrologic improvements over time as the
watershed redevelops. Examples include infiltration practices and conversion of existing
impervious surface to green space.
o Continued monitoring at station NH1.7SCTA to verify that DO and other water quality
parameters improve in response to the implementation of improvement projects.
Draft Report - Sandy Creek Tributary A.docx

Section 1
Introduction
The City of Durham (City) values the integrity of local streams and seeks to improve sites with known
water quality or sediment issues. As required by its municipal separate storm sewer system (MS4)
permit, the City currently monitors the quality of local water bodies and implements various minimum
control measures to improve water quality. The City also implements a range of other structural or
non-structural control measures to address water quality impairments. Given the public investment
in these activities, a strong understanding of the causes/sources of water quality impacts is
important to verify that the City's implementation efforts result in tangible improvements to local
streams.
Water quality monitoring by the City has demonstrated low dissolved oxygen (DO) concentrations in
Sandy Creek Tributary A (station NH1.7SCTA), which could potentially stress aquatic life. The area of
concern extends along Sandy Creek Tributary A from a point where a storm drainage network
daylights at Martin Luther King Jr. Parkway to downstream of Garrett Road (Figure 1-1). Previous
analyses of available water quality data (nutrients, biochemical oxygen demand, etc.) did not indicate
a primary cause of the low DO concentrations, and field inspections for illicit discharges have also
been inconclusive. A field survey performed by the City in 2017 indicated that DO concentrations
decreased steadily downstream from where the stream daylights and decreased more abruptly in the
vicinity downstream of Ivy Creek Boulevard.
In 2020, the City's Stormwater and Geographic Information System (GIS) Services Division of the
Public Works Department engaged Brown and Caldwell (BC) to perform a field investigation of the
causes of low DO. The overall project approach included the following activities for Sandy Creek
Tributary A:
A desktop review of water quality data, watershed characteristics, and potential pollutant
sources
Various field investigations to identify sources and causes of water quality problems
Development of water quality improvement strategies
This report describes the method results of all major study components. Section 2 describes the
baseline data review and watershed characteristics. Section 3 describes the field investigative
methods including stream channel characterization, water quality sampling, a thermal imaging
survey, inspections of the drainage network, and microbial source tracking. Section 4 summarizes
the results of the individual investigations, whereas section 5 synthesizes these results to describe
the sources and causes of low DO in Sandy Creek Tributary A. Finally, section 6 recommends specific
strategies for improving water quality in the stream, addressing both external pollutant sources and
in -stream function.
1-1
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Final Report - Sandy Creek Tributary A
Section 1
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Figure 1-1. Sandy Creek Tributary A study area and City of Durham water quality sampling location.
1-2
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Section 2
Baseline Data Review
The project team conducted a review of available various data sources in 2020, prior to additional field
investigations. These data sources included water quality data, GIS layers, and public databases on potential
pollutant sources. Appendix A summarizes the available geographic and water quality data available for the
study area. The project team reviewed these data with respect to watershed characteristics and potential
contaminant sources within the watershed, with particular attention to potential sources of oxygen demand.
Results of searches of the Toxics Release Inventory (TRI) database, industrial permit databases, and other
public databases were also included to determine if pollutant hotspots are or were present in the Sandy
Creek Tributary A subwatershed. This information was used to inform the design of additional field
investigations.
2.1 Watershed Characteristics and Potential Sources
Sandy Creek Tributary A drains an area of about 1.65 square miles (mi2). A notable characteristic of this
drainage area is the high degree of developed land uses, including large commercial developments and
associated impervious surfaces (Figure 2-1). Overall, about 38 percent of the tributary's drainage area is
impervious, and that percentage is higher for the headwaters. Sandy Creek Tributary A daylights near the
Martin Luther King Jr. Parkway, so much of the upper drainage area simply consists of buried stormwater
pipes.
In addition to urban stormwater runoff, sanitary sewer represents a potential pollutant source. A sanitary
gravity main runs parallel to Sandy Creek Tributary A for its entire exposed length, and the sewer crosses the
tributary in several locations (Figure 2-2). The stream bottom contains multiple manholes. Old topographic
maps and aerial photos (1993) display a sewage disposal facility next to Sandy Creek Tributary A, near the
junction of University Place and Ivy Creek Boulevard (Figure 2-3).
Potential sources of hazardous pollution within close proximity to the stream were also identified including
above ground storage tank (AST) incidents, underground storage tank (UST) incidents, hazardous waste
sites, soil remediation permits for petroleum contaminated soils, and dry cleaning sites. The TRI database
was also consulted. Close to the stream, only three UST sites and one AST site were identified (Figure 2-2).
No TRI facilities were identified within the watershed.
Finally, illicit discharge detection and elimination (IDDE) investigations occurring within the watershed were
mapped. Between June 1996 and January 2020, approximately 115 reports of water quality issues or illicit
discharges were identified within close proximity to the stream (Figure 2-4). The majority of these incidents
involved improper grease storage and disposal practices or discharge from car washing facilities. Several
sanitary sewer overflow (SSO) incidents have also occurred within close proximity to the stream (Figure 2-4).
The oldest incident was reported in 2001 with the most recent incident occurring in 2019.
2-1
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Figure 2-1. Approximate watershed area (as delineated by USGS StreamStats) and land use characteristics - Sandy Creek Tributary A.
Section 2
2-2
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Figure 2-2. Potential point sources including stormwater and sewer infrastructure.
Section 2
2-3
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
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Figure 2-3. Historic topographical map and imagery showing appearance and location of sewage disposal facility in 1993.
Section 2
2-4
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 2
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- �; gvckin9ham R°a
N 0=1 002 0.4 Miles Sandy Creek Tributary A
Brown, .
Reports Caldwell '
Figure 2-4. Locations of IDDE investigations in the watershed from 1996-2020, including dates of SSOs.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 2
2.2 Water Quality Data
The data review step revealed two major sources of water quality data for Sandy Creek Tributary A,
prior to the October 2020 investigation. The City's Water Quality Data Portal included water quality
data collected by the City at station NH1.7SCTA (Sandy Creek Tributary A at Ivy Creek Boulevard) over
2009-2020. The City also performed more detailed field investigations in 2017.
2.2.1 2009-2020 Ambient Monitoring Data
The data from the Water Quality Data Portal consist of monthly grab samples for a range of
constituents including field parameters, five-day biochemical oxygen demand (BOD5), nutrients,
metals, and fecal coliform. These data provided the original information that DO concentrations were
low in the tributary. DO concentrations were highly variable in the tributary but often fell below
4 milligrams per liter (mg/L) in the summer (Figure 2-5) and sometimes below 2 mg/L. DO showed a
strong seasonal pattern, with the lowest concentrations in the summer months of July, August, and
September. However, average DO percent saturation values were 50 to 80 percent even in most
cooler months. The 2009-2020 DO and DO percent saturation data did not display a marked
temporal trend.
12
10
0
1 2 3 4 5 6 7 8 9 10 11 12
Month
90
80
70
60
50
m
40
cn
o 30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12
Month
Figure 2-5. Monthly average DO concentration and DO saturation at station NH1.7SCTA, 2009-2020.
The data did not reveal an obvious cause of the low DO values. The median BOD5 value was
<2 mg/L, although higher values were sometimes measured. For example, the 901h percentile BOD5
of the 2009-2020 dataset was —7 mg/L, and the maximum BOD5 value was 11 mg/L. Ammonia
nitrogen was usually less than 0.1 mg/L. DO correlated inversely with temperature as expected and
also showed some weak to moderate inverse correlations with water quality parameters such as
BOD5, total phosphorus (TP), total Kjeldahl nitrogen (TKN), and total suspended solids (TSS). Fecal
coliform was variable but often very high. For example, the median value was 980 colony forming
unit (cfu)/100 milliliter (mL), and the 90th percentile value was 22,260 cfu/100 mL. For reference,
North Carolina's water quality criteria for fecal coliform are 200 cfu/100 mL (geometric mean) and
400 cfu/100 mL (not be exceeded in more than 20 percent of samples).
2.2.2 2017 City Investigations
In the spring and summer of 2017, the City conducted additional investigations of the low DO values
of Sandy Creek Tributary A. In several different months, City staff walked portions of the stream and
took photographs, field notes, and water quality measurements to locate pollution sources.
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The results were summarized in Water Quality Investigation No. 17WQ105 (City of Durham, 2017).
The investigation confirmed the low DO values. Field notes include reports of abundant orange iron
bacteria, various odors (fishy, musty), and turbid or black water in some locations. Field test kits
indicated that some locations may have had higher ammonia concentrations (0.3-2 mg/L) than
represented by most of the laboratory analytical data for station NH1.7SCTA. Field test kits for
detergents (methylene blue active substances [MBAS]) indicated relatively low concentrations in the
0.5-0.75 mg/L range.
On September 22, 2017, City staff used a hand-held meter to measure DO at various locations
upstream and downstream of station NH1.7SCTA. Those measurements showed a steady
downstream decrease of DO from the location where the tributary daylights (~7.8 mg/L) to near Ivy
Creek Boulevard (3 to 4 mg/L). Downstream of Ivy Creek Boulevard, DO decreased somewhat
abruptly to less than 1 mg/L. This occurred in the vicinity of where the old sewage disposal facility
was located.
Ultimately, the stormwater investigators concluded that "no source of pollution could be found to
explain the in -stream measurements" (City of Durham, 2017). This conclusion was a motivation for
performing the present investigation.
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Section 3
Investigative Methods
The investigation of pollutant sources in Sandy Creek Tributary A included two rounds of field
activities under dry weather conditions (Table 3-1). The initial field investigations were performed in
early fall 2020, and follow-up investigations were performed in early fall 2021. This section
describes the methods that the project team employed for each major activity. Additional details on
these methods are provided in quality assurance projects plans (QAPPs) that were developed for
initial (Brown and Caldwell, 2020) and follow-up (Brown and Caldwell, 2021) investigations.
Round Activity Date(s)
Initial Stream condition assessment Oct. 5, 2020
Longitudinal field parametersurvey
Oct. 5, 2020
Water quality sampling Oct. 6-7, 2020
Thermal imaging survey Sep. 27, 2021
Follow -Up
Survey of upper drainage area Oct. 20-21, 2021
Microbial source tracking Oct. 20-21, 2021
3.1 Stream Condition Assessment
The project team performed a stream condition assessment on Oct. 5, 2020 as part of the initial
field investigations. The purpose of the assessment was to identify potential pollutant sources near
Sandy Creek Tributary A and inform how the channel's physical and hydraulic conditions contribute
to water quality conditions. This activity included a visual assessment, characterization of streambed
sediments, and measurement of streamflow.
3.1.1 Visual Assessment of Channel Condition
A visual assessment was conducted to characterize the physical condition of the channel in the
region of interest. During the assessment, detailed notes were taken to identify areas of geomorphic
or manmade alteration, flow conditions, ponded/stagnant areas, presence of vegetation/debris, and
algal conditions. Additionally, any point sources for contaminants (e.g., MS4 outfalls or other pipes
that could discharge to the stream), nutrients, and sediment were noted. Field staff also took notes
of areas of erosion or bank instability. Locations of potential groundwater seepage as indicated by
iron -oxidizing bacteria were noted.
3.1.2 Characterization of Streambed Sediments
Field characterization of streambed sediments was characterized with respect to grain size, color,
and visual organic content at up to five representative locations. To minimize disturbance, the
sediment characterization occurred after the water quality sampling was conducted. The team
collected shallow cores to characterize the upper —10 centimeters (cm) of bed sediment.
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Section 3
Quantitative measurement of streambed particle size was determined using Wolman pebble counts
at site locations where coarse -grained sediment was present (Fitzpatrick et al, 1998). At sites where
sand and finer -grained sediments were present, the field team noted qualitative descriptions of the
sediment texture using a method similar to that of Ritchey and others (2015). The field team also
visually estimated the percentage of organic detritus in the sediment and documented areas where
films or muck had accumulated.
3.1.3 Streamflow Measurement
The project team took cross -sectional measurements of stream depth, width, and velocity at eight
locations labeled "CS" on Figure 3-1. Velocity measurements at selected locations were obtained
using a handheld velocity meter equivalent to a Global Flow Probe. Streamflow was estimated at
selected locations along the stream length using the velocity -area method (Turnipseed and Sauer,
2010). At the selected stream sites, the stream cross-section was divided into segments of equal
widths. The water depth and velocity were measured within these segments, and the streamflow was
estimated for each segment by multiplying the segment area by the measured velocity. The total
streamflow was then determined by summing the streamflow from each segment. Velocity
measurements were made using the two -point method (Turnipseed and Sauer, 2010). When using
this method, two velocity measurements were taken in each segment. One was taken at a depth
equal to 20 percent of the total depth and another was taken at a depth equal to 80 percent of the
total segment depth. The average of these two observations was used as the mean velocity of each
segment. Water Quality Sampling
3.2 Longitudinal Field Parameter Survey
As part of the initial field investigations (October 5, 2020), the project team measured field water
quality parameters in Sandy Creek Tributary from the daylight point to below Garrett Road (Figure
3-2). The purpose of the survey was to characterize the longitudinal variability of these parameters,
with special interest to the extent of low DO. Field water quality parameters were measured at
intervals of approximately 50 meters (m) along the —1,500 m study segment, and shorter intervals in
regions where field parameters change by more than 10 percent between 50 m intervals, or where
notable inflows or changes to field conditions occur (e.g., large pool). The following parameters were
recorded at each location:
• Time of day
• Latitude/longitude
• Water temperature
• Specific conductance
• pH
• DO (concentration and % saturation)
• Oxidation-reduction potential
• Turbidity
The turbidity measurements will be taken with a hand-held turbidity meter while other field
parameters were measured with a hand-held multiparameter probe.
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Figure 3-1. Locations of cross -sections evaluated on October 5, 2020.
Section 3
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Figure 3-2. Longitudinal field parameter survey conducted on October 5, 2020.
Section 3
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 3
3.3 Water Quality Sampling
The field team collected eight water quality grab samples in the study area during the initial
investigations (October 6-7, 2020). The primary purpose of the sampling was to determine if water
quality was indicative of pollutant source categories such as wastewater or urban stormwater. A
related purpose was to gain insights on in -stream processes such as oxygen demand,
eutrophication, and mixing of different source waters. Sample locations were chosen based on
where field parameters (especially DO) changed over a short distance or where potential pollutant
sources enter the creek. The 2020 sampling locations are displayed on Figure 3-3 and included:
• Location 1: Tributary A where stream daylights; upstream -most location
• Location 2: Pool feature
• Location 4: Riffle on Tributary A between location 2 and station NH1.7SCTA
• Location 5: A second pool feature on Tributary A between location 4 and station NH1.7SCTA
• Location 6: Tributary A at station NH1.7SCTA
• Location 8: Tributary Ajust downstream of old sewage disposal facility
• Location 9: Tributary A between location 8 and confluence with Sandy Creek
• Location 10: Tributary Ajust upstream of confluence with Sandy Creek
Water quality field parameters were measured at each grab sampling location. Grab samples were
delivered to laboratories for analysis of the following parameters:
• Carbon -related parameters: carbonaceous biochemical oxygen demand (CBOD5), total organic
carbon (TOC), and dissolved organic carbon (DOC).
• Nutrient species: TP, orthophosphate (PO4), ammonia nitrogen, nitrite -plus nitrate nitrogen
(NO2+3), and TKN
• Major ions: sodium, potassium, calcium, magnesium, potassium, sulfate, chloride, fluoride, and
bicarbonate alkalinity
• Redox-active substances: total iron, dissolved iron, total manganese, dissolved manganese, and
sulfide
• TSS
• Detergents -MBAS
• Fecal coliform
The QAPP developed for the initial field investigations (Brown and Caldwell, 2020) describes major
quality assurance procedures that were employed, including the collection of field blanks and
duplicate samples.
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Figure 3-3. Grab samples collected October 6-7, 2020 in Sandy Creek Tributary A.
Section 3
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3.4 Thermal Imaging
The initial field investigations revealed that Sandy Creek Tributary A likely experiences both
groundwater inputs and hyporheic exchanges. A thermal imaging survey was performed as part of
the follow-up field investigations (September 27, 2021) to provide insights into the locations and
nature of groundwater inputs to the stream. In this method, infrared cameras are used to capture
images along the stream length. Under warm weather conditions, groundwater inputs are typically
cooler than surface water and can be identified by color in the images. In addition to providing
specific information for Sandy Creek Tributary A, a secondary purpose of this effort was to determine
if this technology would be useful the City to apply on other similar streams.
Thermal and visible light images were collected at 41 locations in Sandy Creek using a FLIR T650sc
Thermal Imaging Camera. The thermal survey extended from the stream daylight point near Martin
Luther King Jr Boulevard to the confluence with Sandy Creek. The survey was performed during late
morning to late afternoon hours, and under dry weather conditions at least 48 hours after significant
(>O.1 in) rainfall.
The field crew first employed the camera in continuous mode to identify locations of potential
thermal anomalies, i.e., where cooler or warmer water (more than 2 degrees Celsius different than
the ambient stream temperature) appeared to be entering the stream. The team then took still
images (infrared and visible light) of these locations and field notes regarding the nature of the flow
and possible origins. In addition to taking thermal images at these anomalies, the field team took
thermal images of the stream approximately every 50 m, roughly estimated in the field, regardless of
whether thermal anomalies appeared to be present or not. Global Positioning System (GPS)
coordinates were recorded for each image location. These locations are identified in Figure 3-4
below. The DO concentration was measured with a hand-held meter at each imaging location.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Lrh a�
F Sno
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2�Ltp — Stormwater Pipe
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Figure 3-4. Thermal image locations in Sandy Creek Tributary A and upper drainage area.
r 1
Section 3
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Section 3
3.5 Survey of Upper Drainage Area
Both the desktop survey and initial field investigations revealed the potential presence of pollutant
sources in the upper drainage of Sandy Creek Tributary A, upstream of the daylight point near Martin
Luther King, Jr. Boulevard. As previously noted, this portion of the drainage area is highly impervious,
and the drainage network primarily consists of buried pipes rather than open channels. A dry
weather screening (DWS) survey of the upper drainage network was conducted from October 20,
2021 to October 21, 2021, with the purpose of identifying potential pollution sources in this area.
The DWS was conducted in accordance with standard procedures that BC developed for another
Phase 1 MS4 locality (City of Virginia Beach. 2018).
In preparation for the DWS, field staff consulted local weather forecasts and reviewed rainfall data
from the USGS to ensure there was no more than 0.10 inches of precipitation during the previous
72 hours. Four locations in the upper drainage area had been previously flagged for inspection by
field staff. Additional sites were identified in the field using the locations of past odor complaints or
by visually inspecting manholes and stormwater channels for dry weather flow.
Not including the stream daylight point, nine locations were ultimately investigated in the upper
drainage area (Table 3-2; Figure 3-5). Of these nine locations, three had enough dry weather flow for
sample collection. At one site, there was only enough flow for on -site testing. The remaining areas
were either inaccessible to field staff or did not show any signs of dry weather flow.
On -Site
Grab
Site
Description
Testing
Sample
Performed
Collected
A
Proposed DWS site near stormwater inlet. No dry weather flow noted.
No
No
B
Stormwater manhole behind restaurant near proposed DWS site. Location of suspected
Yes
Yes
sewer leak.
c
Stormwater inlet near proposed DWS site. Dry weather flow noted butwas unable to access
No
No
for water quality testing or sampling.
D
Natural stream channel before enteringthe piped stormwater drainage network.
Yes
Yes
E
Daylight point of the natural stream channel sampled at Site D. Location of potential illicit
No
Yes
discharge from dumpsters.
F
Daylight point of Sandy Creek Tributary A.
No
Yes
G
Sandy CreekTributary A downstream of University Drive. Location of low DO hotspot
identified during thermal imaging study.
No
Yes
No
I
Stormwater inlet near new development. Small amount of dry weatherflow observed.
Yes
No
H Location of water main break near apartment complex. No
3.5.1 Visual Inspection
The project team conducted a visual screening at each location being investigated. This included
recorded notes of overall condition of the pipe or structure being inspected and other conditions
such as flow, odors, turbidity, surface sheens, foams or scum, staining, benthic growths, etc.
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3.5.2 On -Site Testing
The field team conducted onsite water quality testing at four sites in the upper drainage network
using a DR900 Multiparameter Portable Colorimeter. Onsite testing parameters included ammonia,
fluoride, chloride, copper, and turbidity. The collection container was triple -rinsed with deionized (DI)
water before collecting each sample and, when possible, rinsed twice with the sample water prior to
testing. Following analysis, field test samples were treated as regulated waste and disposed of
properly. Water quality field parameters were recorded wherever an onsite field sample was
analyzed.
3.5.3 Water Quality Sampling
Field staff collected water quality grab samples at five locations (Table 3-2; Figure 3-5). Staff
collected the sample from the center of the channel/pipe while avoiding disturbing bottom sediment
or collecting excess floating debris (City of Virginia Beach, 2018). Samples were dropped off at a
local laboratory for analysis of the following parameters:
Ammonia
Fecal coliform
Carbonaceous Biochemical Oxygen Demand
3.6 Microbial Source Tracking
Although Sandy Creek Tributary A was known to sometimes experience elevated fecal coliform level,
it was not known whether these indicated the presence of wastewater contamination versus other
sources typical of urban stormwater. Therefore, five microbial source tracking (MST) samples were
collected during the DWS investigations. Three samples were collected in the upper drainage
network, one sample was collected at the stream daylight point, and one sample was collected
further downstream along the mainstem of the tributary near University Drive (Figure 3-5). MST
samples were shipped to Microbial Insights, Inc., (Knoxville, TN) for analysis of the Bacteroides
HF183 gene marker (Environmental Protection Agency [EPA] Method 1696 or equivalent) which is an
indicator of human fecal pollution. For comparison purposes, grab samples were also collected at
these sites and analyzed for fecal coliform.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
t
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Figure 3-5. Upper drainage area DWS survey and sample locations.
Brown>�.c .
Caldwell '
Section 3
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Section 4
Results of Field Investigations
This section presents the major findings of the field investigations identified in section 3, with a focus on
results that provide insights into pollutant sources or other controls on stream water quality conditions.
4.1 Stream Condition Assessment
Prior to sample collection in October 2020, BC staff conducted a visual stream survey beginning upstream at
the stormwater network daylight near Martin Luther King Jr. Parkway and ending at a downstream point near
Garrett Road. In January of 2022, a follow-up assessment was conducted to identify opportunities for stream
restoration. For the purpose of this report, the stream was divided in four segments based on major road
crossings. Locations of water quality concerns and stream condition observations noted during both stream
assessments are shown in Figure 4-1, Figure 4-4, Figure 4-8, and Figure 4-13.
Between the stormwater daylight at Martin Luther King Jr Parkway and the culvert under Ivy Creek
Boulevard, significant bank erosion, channel widening, and stream incision were observed in Sandy Creek
Tributary A (Figure 4-2). Along this segment, the stream is surrounded by impervious surfaces (roads, parking
areas, shopping centers, and apartment complexes) and multiple large stormwater outfalls. Additionally, the
stream is no longer connected to the historic floodplain which has contributed to entrenchment and bank
instability (Figure 4-3). Steep stream banks, fallen trees, debris dams, large pool features, and areas of
stagnant water were all observed along this segment of the stream.
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Figure 4-1. Observations from stream assessments (Martin Luther King Jr Parkway to Ivy Creek Boulevard).
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
Figure 4-2. Bank erosion and large pool features holding stagnant water downstream of
Martin Luther King Jr. Parkway.
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Figure 4-3. Example of impervious area directly adjacent to areas of bank instability.
Downstream of Ivy Creek Boulevard, bank erosion and debris blockages were observed. Just
upstream of University Drive, a large amount of riprap placed at the culvert inlet partially blocks the
flow of water during baseflow conditions (Figure 4-6 and Figure 4-7). Additionally, it appears that
stream dredging may have occurred in the past with excess sediment being placed directly along the
stream banks. As a result of the riprap blockage and floodplain buildup, this segment of the stream
is more channelized so that there are very few meanders or riffle/run features. Stream velocities are
close to zero and water depths are significantly higher in this area (Figure 4-5). There are also
multiple sewer manholes that are vulnerable to flooding and bank erosion.
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Figure 4-4. Observations from stream assessments (Ivy Creek Boulevard to University Drive).
Section 4
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Figure 4-5. Stagnant water upstream of University Drive.
Figure 4-6. Stream conditions near University Drive facing downstream.
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Figure 4-7. Stream conditions near University Drive facing upstream.
Further downstream between University Drive and Garrett Road, the stream channel is more
connected to the historic floodplain with lower bank heights and surrounding wetland areas. Bank
erosion was observed along with multiple, braided channels, tight meanders, sandy sills, and point
bars (Figure 4-9). Areas of significant stream channel widening and sediment aggradation indicate a
shifting stream morphology (Figure 4-11). Massive blockages within the stream consisting of fallen
trees and litter/debris have also contributed to low flow conditions (Figure 4-10). Further
downstream near Garrett Road, the stream is more channelized with its banks stabilized by riprap
(Figure 4-12).
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Figure 4-8. Observations from stream assessments (University Drive to Garrett Road).
Section 4
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
Figure 4-10. Example of debris dam between University Drive and Garrett Road.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Section 4
i
I NO
k
C: jy
Figure 4-11. Example of Stream widening and sediment aggradation between University Drive and
Garrett Road.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
Figure 4-12. Stabilized stream banks upstream of Garrett Road.
The final segment of Sandy Creek Tributary A includes the area between Garrett Road and the
confluence with Sandy Creek. Channel incision and bank erosion were primarily observed along this
portion of Sandy Creek Tributary A (Figure 4-14, Figure 4-15). As with upstream segments of the
stream, multiple debris blockages were noted, but large, deep pools of stagnant water were not as
common.
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Figure 4-13. Observations from stream assessments (Garrett Road to confluence with Sandy Creek).
Section 4
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Section 4
Figure 4-14. Example of stream channel widening and sediment aggradation downstream of Garrett Road.
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Section 4
- W
Apr
Figure 4-15. Example of bank erosion and channel incision downstream of Garrett Road.
In addition to evaluating the physical condition of the stream, potential sources of water quality issues in the
vicinity of the stream were also noted. For example, at multiple locations, iron -rich groundwater flow was
indicated by the presence of iron -oxidizing bacteria (Figure 4-16). Stormwater runoff was identified as
another potential point source with multiple large stormwater pipes outfalling to the stream (Figure 4-1;
Figure 4-18). Other observations included an unprotected aerial sewer line crossing (Figure 4-17) and a large
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Section 4
amount of litter and debris along the entirety of the project area. Additionally, flooding and erosion around
manholes upstream of University Drive near the historic sewage disposal facility may increase the risk of
SSOs during major storm events (Figure 4-19).
Figure 4-16. Example of the iron -oxidizing bacteria observed at multiple locations along Sandy Creek Tributary A.
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Section 4
Figure 4-17. Aerial sewer line crossing.
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Section 4
Figure 4-18. Example of stormwater drainage into stream upstream of Ivy Creek Blvd.
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Section 4
Figure 4-19. Evidence of flooding and erosion near sewer manholes.
Following the October 2020 stream assessment, water velocity, stream width, and water depth was
measured at eight cross sections along Sandy Creek Tribitary A (Table 4-1). From this information, stream
flow values in units of cfs were estimated. It should be noted that along each cross-section, many velocity
measurements were at or below the meter's detection limit of 0.05 feet per second (fps). Therefore,
streamflow measurements should be considered estimates rather than highly accurate values.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Section 4
Stream Max Maximum Calculated
Cross- Cross -Section Width Water Velocity Streamflow Pebble Streambed Sediment Other
Section Description Depth Measurement Count Characteristics Notes/Observations
(ft) Estimate (cfs)
Channel too deep for
Stream channel
pebble count. Large
downstream of
pieces of concrete Metal culverts are
CS-1 stormwater
17
2.0
0.5
0.9
No observed in pool. Little corroded. Increased water
daylight
to no organic matter velocities observed.
observed in the
streambed sediment.
Sandy streambed with
Despite tree roots and
gravel observed along
vegetation growing along
Channel
banks. Broken glass and
banks, significant erosion
CS-2
Downstream of
7
1.5
0.06
0.3a
No other debris observed.
observed. Multiple fallen
First Pool
Little to no organic
trees and large pool
matter observed in the
features were also
streambed sediment.
observed in the areas
around this cross-section.
Channel too deep for
Stream channel deepens
pebble count. Riprap
and widens at this point.
Channel
observed in stream and
Water becomes more
CS-3
upstream of
26
1.4
0.06
0.2a
No along banks. Little to no
turbid with lower
triple culvert
organic matter observed
velocities. Stagnant water
in the streambed
observed upstream of this
sediment.
site.
Pool nearwater
Sand with low organic
Turbid water and low-
CS-4
quality site 9
8
1.2
0.04
0.1a
No matter content.
velocity conditions
observed.
D50 = 0.5-1.0 mm
Riffle near
(coarse sand)
Sandy streambed with
CS-5
water quality
4
0.2
0.39
0.2a
Yes
Little to no organic
large amount of trash and
debris. Very shallow water
site 9
matter observed in the
depths.
streambed sediment.
No pebble count -
CS-6
Pool near
13.5
1.3
0.15
0.6
No
uniformly sand/siltwith
Fallen tree within pool.
Garrett Road
low organic matter
content.
Banks lined with
No pebble count (too
Channel near
much riprap). Little to no
CS-7
waterquality
6
1
0.06
0.2
No
organic matter observed
Stagnant water observed
Stagnant wal ater
sitel0
in the streambed
near this crosssection.
sediment.
D50 = 32-45 mm
Stream channel
Riffle just
(very coarse gravel)
straightens and has been
CS-8
upstream of
3
0.4
1.0
0.7
Yes
Little to no organic
stabilized with riprap.
Garrett Road
matter observed in the
Highest watervelocities
streambed sediment.
observed.
I Flow estimated. All stream velocity measurements were less than 0.05 fps at this station.
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Measured water velocities appeared to be highest just upstream of Garrett Road and just below the
stormwater daylight near Martin Luther King Jr. Parkway. Between these two points, changes to the stream's
morphology lead to decreases in measurable water velocity. For example, in the areas around CS-2, the
stream is dominated by large pool features with little to no measurable flow. Further downstream at CS-3, an
excessive amount of riprap placed within the stream blocks the flow of water and results in much lower
measured velocities. The pool feature at CS-4, where flow was estimated to be 0.1 cfs, is located in an area
of the stream where multiple side channels divert flow from the mainstem of the stream. Estimated
streamflow then increased to 0.6 cfs where the stream converges back into one channel at CS-6. Near CS-7,
multiple fallen trees, log sills, and sand bars may have impacted measured water velocities, resulting in
lower flow estimates.
4.2 Field Parameter Survey
The longitudinal field parameter survey was performed by Dramby and Associates on October 5, 2020. Full
results of the field parameter survey are provided in Attachment B.
Water temperatures were between 13 and 18 degrees C on the day of the survey. Specific conductance
decreased from -0.40 milliSiemens (mS)/cm at the daylight point to -0.28 mS/cm near Garrett Road
(Figure 4-20). The pH was 8.0- 8.3 standard units (s.u.) throughout most of the tributary except for some
lower values (7.1-8.0 s.u.) near Garrett Road. The stream was turbid despite the lack of recent rain.
Turbidity ranged from 100-150 nephelometric turbidity units (NTU) throughout the study's reach.
DO concentrations were already depressed (<3 mg/L) at the point that the tributary daylights near Martin
Luther King Jr. Parkway (Figure 4-21). DO concentrations decreased to less than 1 mg/L within 300 meters
of the daylight point and remained <1 mg/L for most of the length of the tributary. In some locations, DO was
observed to increase at locations of noticeable stream velocity, with the return to lower values in
downstream stagnant areas. The stream had higher DO (3-5 mg/L) in the downstream segments near
Garrett Road where flows were higher. DO percent saturation followed a similar spatial pattern and was less
than 10 percent in most of the stream.
Redox potential was about 170-200 millivolt (mV) in most of the upstream half of the study reach, with
slightly higher values (200-220 mV) in the downstream half of the tributary. These positive values indicate
oxidizing conditions, despite the low DO measurements.
4.3 Water Quality Sampling
Water quality grab samples were collected at eight locations (Figure 3-3) on October 6-7, 2020. The sample
numbering corresponds to the locations identified in the QAPP (Brown and Caldwell, 2020). All sampled
locations were on the mainstem of Sandy Creek Tributary A. The QAPP (Brown and Caldwell, 2020) described
the possibility of collecting additional grab samples from side channels or other inflows to the tributary
(locations 3 and 7). However, on the days of sample collection, there was little to no observable inflow to the
channel from most side channels or stormwater outfalls, and the locations of observable inflow (Figure 4-1)
had too little inflow to either measure or sample. The three downstream samples (8, 9, and 10) were
collected on October 6, whereas the remaining grab samples were collected on October 7.
The grab sample data met data quality objectives for almost all constituents. All constituents were below the
method detection in the field blank sample except for TKN. The value recorded for that constituent
(0.39 mg/L) was less than the reporting limit (0.5 mg/L) in the field blank, so the concentration was
estimated by the laboratory. The relative percent difference between the duplicate samples at site 8 was
less than 15 percent for all constituents except dissolved iron (38 percent) and sulfide (18 percent).
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Figure 4-20. Measured specific conductance and calculated streamflow estimates along Sandy Creek Tributary A, October 5, 2020.
Section 4
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Figure 4-21. Measured dissolved oxygen concentrations and calculated streamflow estimates along Sandy Creek Tributary A, October 5, 2020
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Section 4
Field parameters were measured at each grab sampling location (Table 4-2). These are largely consistent
with the results of the longitudinal field parameter survey discussed in section 3.2. DO was already low
(<4 mg/L) at the stream daylight point and decreased to <1 mg/L within a few hundred meters. DO only
returned to -3 mg/L at the most downstream station. As in the longitudinal survey, the field measurements
associated with the grab samples showed turbidity consistently greater than 100 NTU and oxidizing redox
conditions. The data also show modest downstream decreases in pH and specific conductance over most of
the study reach.
Site Water Temperature (deg. C) Specific Conductance (MS/cm) pH DO (%) DO (mg/L) I ORP (mV) I Turbidity (NTU)
1
17.99
0.403
2
16.93
0.401
4
15.86
0.409
5
15.47
0.394
6
15.68
0.412
8
15.72
0.358
9
15.78
0.329
10
14.2
0.500
7.98 43.3 3.97
161
202
104
106
7.9
9.4 0.88
7.55
<5
<1
211
120
7.27
<5
<1
232
121
6.3
<5
<1
239
121
7.4
<5
<1
183
108
7.1
<5
<1
181
127
7.44
32.1
3.19
125
105
The grab sample results are presented as bar charts in Figure 4-22 and discussed in subsections below.
Laboratory results for each grab sample are also presented in Table 4-3.
4.3.1 Ionic Composition
The specific conductance of Sandy Creek Tributary A (0.3-0.4 mS/cm) indicated freshwater conditions and
would be consistent with a salinity in the 200-300 mg/L range. The stream had a mixed ionic composition
during the October 2020 sampling event. Calcium was the most abundant cation in milliequivalents
(meq)/L, but sodium and magnesium also comprised a significant proportion of the anionic composition.
Bicarbonate was the most abundant anion in meq/L, with chloride as the second most abundant. The water
became slightly fresher between the point of daylighting and just upstream of Garret Road, as reflected in
the modest decreases in specific conductance, sodium, and chloride (Figure 4-22).
4.3.2 C130D5 and Carbon
CBOD5 was relatively low (<2 mg/L) at most locations in Sandy Creek Tributary A. Slightly higher values were
measured at site 2 (-3 mg/L) and station 6 (-4 mg/L), both of which are located between the daylight point
and Ivy Creek Boulevard. DOC and TOC concentration were both in the 4.4-5.5 mg/L range, indicating that
most of the organic carbon was dissolved. Both DOC and TOC showed a small steady increase downstream
over the reach.
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Section 4
Parameter
Table 4-3. Laboratory
Unit Site 1 Site 2 Site 4 Site 5
mg/L 0.190 0.180 0.120 0.110
Site 8 Site 8 Site 9 Site Equip -
Duplicate 10 ment
Blank
<0.024 <0.024 <0.024 <0.024 <0.024
Site 6
Ammonia
0.069
Bicarbonate Alkalinity asCaCO3
mg/L
160
160
140
140
150
150
140
130
130
<0.5
Calcium
Carbonaceous Biochemical Oxygen
Demand (5 day)
mg/L
44
46
44
41
44
53
51
46
42
<0.084
mg/L
<2.0
3.3
<2.0
<2.0
4.3
<2.0
<2.0
<2.0
<2.0
<2.0
Chloride
mg/L
32
32
30
30
30
29
29
27
24
<1.4
Dissolved Iron
mg/L
0.390
0.086
0.220
0.140
<0.075
0.110
0.075
0.170
0.100
<0.075
Dissolved Manganese
mg/L
0.39
0.34
0.38
0.32
0.21
0.11
0.10
0.17
0.11
<0.003
Dissolved Organic Carbon
mg/L
4.6
4.7
4.9
4.9
5.3
5.5
5.6
5.6
5.9
<O.5
Fecal Coliform RAL
CFU/100 mL
1000
560
2000
2100
1270
250
270
455
99
ND
Fluoride
mg/L
0.19
0.20
0.19
0.20
0.20
0.18
0.18
0.21
0.16
<0.032
Iron
mg/L
2.20
1.80
1.80
1.30
1.30
0.95
0.90
1.20
1.10
<0.075
Magnesium
mg/L
12.0
12.0
12.0
11.0
11.0
14.0
13.0
12.0
11.0
<0.12
Manganese
mg/L
0.39
0.35
0.43
0.30
0.26
0.14
0.14
0.20
0.13
<0.003
Methylene Blue Active Substances
mg/ 340 MW
<0.067
0.074
0.070
0.074
<0.067
<0.067
0.070
0.070
<0.067
<0.067
Nitrate Nitrite as N
mg/L
0.69
0.72
0.64
0.65
0.56
0.47
0.47
0.38
0.27
<0.018
Nitrogen, Kjeldahl
mg/L
1.10
1.10
0.85
1.10
1.10
0.44
0.43
0.46
0.36
0.39
Orthophosphate
mg/L
<0.015
<0.015
<0.015
<0.015
<0.015
<0.015
<0.015
<0.015
<0.015
<0.015
Phosphorus, Total
mg/L
0.052
0.045
0.049
0.051
0.094
<0.032
<0.032
<0.032
<0.032
<0.032
Potassium
mg/L
2.4
2.6
2.7
2.5
2.8
2.8
2.7
2.8
2.8
<0.34
Sodium
mg/L
34
35
35
32
34
33
33
30
27
<0.92
Sulfate
mg/L
22
22
21
22
21
21
21
19
18
<1.4
Sulfide
mg/L
<0.81
<0.81
<0.81
<0.81
<0.81
<0.81
0.97
<
1.10
<0.81
Total Organic Carbon
mg/L
4.4
4.4
4.6
4.7
4.9
5.0
5.0
5.2
5.4
<O.5
Total Suspended Solids
mg/L
8
<5
12
8
13
7
8
5
11
<1
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Section 4
Bicarbonate Alkalinity as CaCO3, mgfL Carbonaceous Biochemical Oxygen Demand. mg1L Methylene Blue Active Substances, mi LAS
MW 340
150- 4
0 06
1D0- 3
50- 0-HNE HHH0.00-
Calcium, mgfL Chloride, mgfL Fluoride, mgfL
30 - 0,20 -
40 20-
0.15 -
2010 0.05 -
0- 0- 0.00-
Iron, mi
2.0
1.5
0.0 -
Manganese, mglL
Dissolved Iron, m91L
0.4 -
0.3 - 10
02
0.1
- ■ ■0■■■ 5-
0.0 - 0-
Dissolved Manganese, mgfL
0.4
0.3 - 0.3 2
0.11■■■■ 0.1■■■■ 1
0.0- O.D_ 0_
Magnesium, mgfL
11111111
Potassium, mgfL
Sodium, mgfL Sulfate, mi Sulfide, mgfL
30-
0.9 -
15
20 - 10 - 0.B
10 - 5 0-3 -
0- 0- 0-0-
Ammonia, mgfL Nitrate Nitrite as N, mgfL Nitrogen, Kjeldahl, mgfL
0.15
1010-
0.00 0 0
Phosphorus, Total, mgfL Ortho-Phosphate, mgfL Total Organic Carbon, mgfL
0 015-
0.075
4
110,
-
-11111111
0.050 ■■■■ MEN
0025-
D_005- 2"
0.000 - 0.000 0-
Dissolved Organic Carbon, mgfL Total Suspended Solids, mgfL Fecal Col'rform i CFU1100 mL
6
2000-
4" 10 1500"
11
0- 0-■� ■ ■■ 0-
5■■ ■. . .
2 010000- ,
A 5 ro � � ,�O
Figure 4-22. Water quality results for Sandy Creek Tributary A, October 6-7, 2020.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
4.3.3 Iron and Manganese
A comparison of total versus dissolved iron and manganese concentrations in Sandy Creek
Tributary A indicates that most of the iron was particulate, but most of the manganese was
dissolved. Total iron concentrations were in the 1-2 mg/L range at most stations, and total
manganese was in the 0.15-0.4 mg/L range. Both of these ranges are relatively high for surface
water. (As points of reference, the secondary maximum contaminant level [MCL] for iron in drinking
water is 0.3 mg/L, and secondary MCL for manganese is 0.05 mg/L.) Iron and manganese
decreased from upstream to downstream, possibly due to settling and precipitation. Dissolved iron
was in the 0.1-0.4 mg/L range at most stations, and dissolved manganese was at similar
concentrations.
The dissolved iron and manganese concentrations exceeded the expected solubility of iron and
manganese under the prevailing pH and redox conditions. In combination with the low DO and field
observations of abundant iron oxidizing bacteria, it provides additional evidence of the entry of low -
DO, high -iron groundwater into Sandy Creek Tributary A. Some forms of bacterially -mediated iron
oxidation are alkalinity -consuming reactions (Hegler and others, 2008), which might contribute to the
downstream decrease in pH and alkalinity in Sandy Creek Tributary A.
4.3.4 Nutrients
Ammonia nitrogen concentrations were detectable but relatively low (<0.190 mg/L) at the daylight
point, decreasing to non -detectable (<0.024 mg/L) concentrations by station 8 downstream of Ivy
Creek Boulevard. Nitrate -plus -nitrite nitrogen concentrations were -0.7 mg/L at upstream stations
and decreased downstream to 0.3-0.5 mg/L at downstream stations. TKN was mostly comprised of
organic nitrogen. TKN also decreased downstream from 1.1 mg/L at the daylight point to ~0.4 mg/L
at downstream stations. TP concentrations were also higher (0.5-1.0 mg/L) at the upstream
stations and below the 0.032 mg/L method detection limit (MDL) at downstream stations 8 to 10.
Orthophosphate P concentrations were consistently non -detectable (i.e., less than 0.015 mg/L).
4.3.5 Other Indicators
Fecal coliform concentrations were variable, but most exceeded North Carolina's criterion of
400 CFU/100 mL for single samples. The fecal coliform concentration was already elevated
(1,000 CFU/100 mL) at the daylight point and had the highest values about 250 meters
downstream (station 5). Fecal coliform concentrations were lower (<300 CFU/100 mL) at the
downstream stations 8, 9 and 10. Detergent (MBAS) concentrations were low (<0.075 mg/L)
throughout Sandy Creek Tributary A. Most sulfide concentrations were less than the MDL of
0.81 mg/L. Despite the elevated turbidity values, TSS concentrations were relatively low (5-13 mg/L)
at most stations. The high turbidity appeared to be caused by very fine materials, possibly colloidal
material or bacteria.
4.4 Thermal Imaging
The results of the thermal imaging study are presented in two subsections below. The first
subsection (4.4.1) presents findings specific to Sandy Creek Tributary A, and the second subsection
(4.4.2) discusses implications for applying this technology to other streams in the Durham area.
4.4.1 Findings in Sandy Creek Tributary A
This section discusses the stream -specific major results from the thermal imaging survey of Sandy
Creek Tributary A. The thermal and visible images presented into this section were selected as
examples of key observations in Sandy Creek Tributary A. The compilation of all thermal and visible
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Section 4
light images and an associated to key will be provided to the City separately. The day of the survey
(September 27, 2021) was relatively warm and sunny, with a high temperature of 81 degrees F.
Velocity measurements and DO readings were taken the following day at the daylight point and
upstream of major road crossings along the stream and are presented in Table 4-4.
Cross -Section Description
Stream channel downstream of
stormwater daylight
Channel upstream of Ivy Creek Blvd
Channel upstream of University Dr
Channel upstream of Garrett Road
Streamflow Estimate (cfs)
0.6
0.22
0.10
0.25
Dissolved Oxygen Concentration (mg/L)
7.46
6.61
4.84
8.57
1. Most groundwater inputs to Sandy Creek Tributary A are low in magnitude or diffuse rather than
discrete plumes. The great majority of thermal images did not provide thermal evidence of
concentrated groundwater seeps or springs to the stream. Very few survey locations displayed
obvious plumes of cooler or hotter water entering the stream from the bank or streambed. This
was not due to the lack of sensitivity of the camera, because the technology is highly sensitive to
small changes in temperature and did detect such plumes where present. Rather, the lack of
marked thermal plumes in most segments suggests that groundwater inputs are low or diffuse in
most sections of the stream. With some exceptions, the majority of the bed and bank material is
relatively coarse -grained (e.g., sand). Hence, groundwater can infiltrate (or exfiltrate) the stream
at low rates over a distance rather than be concentrated at discrete pinch points or fractures. In
these cases, the thermal camera will display similar temperatures over the water surface (e.g.,
Figure 4-23).
23.0 °C
k:172C
Figure 4-23 - Left bank image at site 2, showing relatively uniform water temperatures and the lack of
visible seepage plumes.
Diffuse inflows could theoretically also be detected by thermal imaging, if they were of sufficient
magnitude to cause measurable differences in water temperature in near -bank versus mid-
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channel water. Many of the thermal imagery from Sandy Creek Tributary A did show cooler water
near the banks (e.g., Figures 4-24 and 4-25), and diffuse groundwater inputs might contribute to
this thermal difference. However, near -bank water is also subject to a greater degree of shading
from overhanging banks and vegetation than mid -channel water, making it difficult to distinguish
distributed near -bank inflows from shading effects. The capabilities of thermal imaging to detect
different types of groundwater inputs is discussed further in section 4.4.2.
23.4 °C
I
23A "C
19.4 c
Figure 4-24 - Right bank image at site 1, showing cooler water near bank.
w s..
�r R4
t
1
U
Figure 4-25 - Left bank photo at site 34, showing cooler water near bank.
2. A small number of discrete groundwater inputs to Sandy Creek Tributary A were observed.
Although most groundwater flow into in Sandy Creek Tributary A is diffuse, the study confirmed
that thermal imaging is capable of detecting discrete groundwater inputs. These inputs took two
forms as follows:
a. Preferential flow structures in clayey bank materials: Although most of the bank and bank
materials of Sandy Creek Tributary A is sandy, some areas have clayey banks, especially
downstream of Garrett Road. A few groundwater seeps were noted in this clayey bank
material and were associated with roots (Figure 4-26) or other preferential flow structures
within the banks (Figure 4-27). The magnitude of the seepage at these locations was very
low and insufficient to sample. Overall, these types of seeps were uncommon and did not
appear to contribute large amounts of flow to the stream.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
24.4 "C
17.8 IC
25.1 °C l
19.1 'C
Figure 4-26 - Right bank photo at site 10, showing seep in bank.
Figure 4-27 - Left bank photo at site 22, showing seep.
b. Groundwater -fed pools: Site 29 provided the single best example of typical groundwater
inputs to Sandy Creek Tributary A. At this location, a near -bank pool appeared to receive
groundwater inputs as evidence by abundant iron bacteria, and to release that water to the
main channel (Figure 4-28). The release to the stream appeared in the thermal imagery as a
plume that was slightly warmer (not cooler) than the main channel flow (Figure 4-29). The
field team inferred that the water in the pool was warmed by solar radiation prior to release
to the main channel.
Sandy Creek has many locations of abundant iron bacteria, and such bacteria are a more
readily apparent indicator of groundwater inputs than thermal imagery. The main benefit of
thermal imagery for site 29 was to confirm the active flow from the pool to the main
channel, which was especially marked on video (provided separately). The plume from the
pool to the main channel was actually slightly warmer than the main channel flow,
presumably due to solar heating of the pool. The ability to observe the active flow was
facilitated by the concentration of the flow through a small channel that connected the pool
to the main channel. Many of the areas of groundwater upwellings (as indicated by iron
bacteria) lack such discrete connecting channels between the area of groundwater input
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25.2 C:
20Z °C
and the main channel, and so would be more difficult to detect with thermal imagery.
Hence, site 29 should be considered the most thermally -apparent example of other areas of
groundwater contributions to Sandy Creek Tributary A.
Figure 4-28 - Groundwater -fed pool on right bank at 29. Sandy sediments separated this pool from the main
channel flow except for a small connect channel.
23.7 'C
19.6 'C
go
*FLIK
Figure 4-29 - Plume of water entering the main channel of Sandy Creek Tributary 1 from the groundwater -
fed pool on the right bank at site 29.
3. In combination with other field data, the thermal survey confirmed that groundwater inputs
contribute to low dissolved conditions in Sandy Creek Tributary A. Site 29 once again provides
the best proof of low DO groundwater inputs to Sandy Creek Tributary A. Most segments of
Sandy Creek Tributary A had moderate to high DO (6-10 mg/L) on the day of the thermal survey.
However, the groundwater -fed pool at site 29 had a significantly lower DO (-2.2 mg/L) and was
confirmed by thermally imagery to be actively flowing into the main channel of Sandy Creek
Tributary A. The magnitude of the flow was too low to measure and was insufficient to cause a
noticeable decrease in the main channel DO. However, as mentioned above, this site can be
considered as representative of many other locations which could collectively contribute to low
DO in the main channel under baseflow conditions.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
4.4.2 Lessons for Broader Application
This section provides general observations on the thermal imaging technology and how it might be
applied to other streams in the City.
1. Thermal surveys are capable of detecting discrete groundwater seeps but less useful for
characterizing distributed/diffuse groundwater inputs. This general conclusion follows directly
from the Sandy Creek Tributary A -specific observations discussed in section 4.4.1. The utility of
the thermal surveys will thus depend in part on the streambed/bank materials and nature of the
groundwater inputs. Streams that flow though bedrock or low -permeability materials are more
likely to have discrete seeps in fractures or other preferential flow zones. Such discrete seeps
could also occur in coarse -grained materials in some circumstances. For example, concentrated
flows (e.g., from a near -stream sewer break) would be expected to be detectable even if
delivered through sandy materials.
In addition to scouting for concentrated inflows, thermal cameras would also be useful
confirming inputs that are suspected based on other lines of field evidence, such as visible
flows, staining, presence of iron bacteria, odors, or locations of changes in water quality.
Although thermal imagery is useful for detecting concentration inflows, streams set in coarse -
grained materials may primarily receive groundwater inputs in diffuse/distributed zones with
insufficient concentration of flow to cause clear thermal signatures.
2. Groundwater inputs that "pool" might be similar in temperature or even warmer than the main
channel flow. The paradigm of thermal surveys is that groundwater inputs will tend to be cooler
than surface water under warm seasonal conditions, and warmer than surface water under cold
seasonal conditions. Site 29 on Sandy Creek Tributary provided an example of where
groundwater infiltrated the stream in a relatively still pool, and the pool reached a temperature
similar to (actually slightly warmer) than the main channel flow prior to discharging to the main
channel. In this case, the presence of iron bacteria is a more readily apparent indicator of
groundwater inputs than thermal differences. Thermal imagery can still be useful in these
circumstances for visually verifying active flow from the pool to the main channel, which can be
difficult to detect with only visible light.
3. Thermal surveys results will be more conclusive if performed under consistently shaded
conditions. Thermal cameras such as the FLIR650sc and other commonly -used field models are
sensitive enough to detect small differences (<1 deg C) in water temperatures. This provides an
obvious advantage in detecting thermal irregularities. However, the high sensitivity also means
that they will readily detect temperature differences caused by non -hydrologic factors such as
differential shading of the water surface. Figure 4-30 provides an example of a thermal image
where the water surface displays varying temperatures due to variable shading, such as tree
shadows. Differential shading makes it more difficult to detect temperature differences that are
due to hydrologic factors.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
24,3 'C
Ii
19.2 'C
M
Figure 4-30 - Image from site 3, showing effect of differential shading.
To minimize the interference of differential shading, thermal surveys could be performed at
times of day when the stream is not receiving direct sunlight. For warm season surveys, late in
the day would be preferable to early in the day, to allow the surface water to warm and attain a
greater temperature contrast with cooler groundwater. Surveys could also be performed on
warm but overcast days.
4. Other practical advice for performing thermal surveys. Following are miscellaneous
recommendations for performing thermal camera surveys:
Figure 4-31 - Right bank of site 1. Example of
a. Scout for seeps with live image mode and
picture -in -picture mode: The results of a thermal
survey are mostly captured in still thermal images
with associated visible light images. Video
recordings are also useful to capture dynamic flow
conditions. But in the field it is useful to scout for
temperature anomalies using live image mode, in
which the camera displays (but does not record)
the real-time thermal image in the field of view.
This allows the camera operator to view large
areas without using camera memory, and focus
on areas with thermal anomalies. Similarly, the
picture -in -picture (PIP) mode overlays a thermal
image on the visible light image (e.g.,
Figure 4-31). This mode is useful for scouting
picture -in -picture mode. because it is sometimes difficult to identify
objects or judge distances in the thermal image without the visible light perspective.
b. Use autofocus. Field experience with the camera demonstrated that the autofocus
feature was useful for focusing the image prior to recording. It is also necessary to hold
the camera as still as possible, which would be facilitated with a monopod.
c. Consider needs for extra batteries. Different model cameras have different batteries
lives. For example, the FUR 650cs camera used for Sandy Creek Tributary A uses a
lithium ion battery with approximately 4 hours of battery life if continuously operated in
live image mode. Extra batteries would thus be advised for a full day of field work.
d. Consider memo► s� e needs. The thermal cameras utilize standard SD memory
cards, and the number of images that can be stored depends on the SD card memory
and the camera resolution. Most of the high -resolution images captured in Sandy Creek
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Section 4
area approximately 1-2 kilobytes each, and two such images (thermal and visible) are
stored with each recording. Hence, even a 32 gigabyte SD card could store thousands of
images. Video will obviously take up more memory. For reference, a 17-second thermal
video in Sandy Creek Tributary A used approximately 6.2 KB of memory.
4.5 Survey of Upper Drainage Area
During the survey of the upper drainage area, field staff investigated nine areas of concern as
described in section 3.5. Table 4-5 and Figure 4-32 summarize the visual observations from each
site.
Dry Observed or
Weather
Suspect
Site
Site Description
Summary of Observations
Flow
Pollution
Proposed DWS site near
No dry weather flow observed but an uncapped sewer cleanout
Observed
No
Sources
None
A
stormwater inlet. No dry weather
was noted in the vicinity of the stormwater inlet
flow noted.
Stormwater manhole behind
Stormwater manhole near a restaurant; location of previous
Yes
Suspected
B
restaurant near proposed DWS
odor complaint
sewage
site. Location of suspected sewer
leaking into
leak.
Odor and water quality results indicated that raw sewage was
stormwater
Stormwater inlet near proposed
flowingthrough manhole
Yes
pipe
Unknown
C
DWS site. Dryweatherflow noted
Orange benthic growth noted
but was unable to access forwater
quality testing or sampling.
Natural stream channel before
Visual appearance of stream prior to entering stormwater
Yes -
None
D
entering the piped stormwater
network did not indicate any pollution sources
perennial
I
drainage network.
Daylight point of the natural
Stream
Yes -
Dumpster
E
stream channel sampled at Site D.
Petwaste and dumpster leachate noted in the vicinity of the
Perennial
leachate
Location of potential illicit
stream
Stream
adjacent to
discharge from dumpsters.
Daylight point of Sandy Creek
I
Yes -
stream
Unknown
F
Tributary A.
Appearance of stream consistent with past site visits
Perennial
Sandy Creek TributaryA
Stream
Yes-
Unknown
G
downstream of University Drive.
Perennial
Location of low DO hotspot
Iron -oxidizing bacteria noted in -stream
Stream
identified during thermal imaging
study.
Location of water main break near
Odor and color indicated high chlorine concentration.
Yes
Chlorinated
H
apartment complex.
Suspected water main break
drinking
water
Stormwater inlet near new
Observed flow was colorless and odorless. Unable to
Yes
Unknown
development. Small amount of dry
determine origin
weather flow observed.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Figure 4-32. Observations and sampling sites from the DWS.
Section 4
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At four of these sites, staff observed dry weather flow in the stormwater drainage network. The
sources of dry weather flow were unknown at two sites but a sewer line break (Figure 4-33) and
water main break (Figure 4-34) were the suspected sources of flow at the other two sites.
Figure 4-33. Suspected sewage observed in stormwater manhole (Site B).
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
Figure 4-34. Suspected water main break (Site H).
A small tributary to Sandy Creek Tributary A was also inspected with samples being collected at an
upstream location before the stream becomes a piped channel as well as at a downstream location
where the stream briefly daylights before entering another pipe beneath the parking lot for a
shopping center. At the downstream location, staff identified potential sources of pollution that
included pet waste and a leaking dumpster (Figure 4-35).
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Figure 4-35. Dumpster leachate flowing into tributary to Sandy Creek Tributary A.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
Ultimately, on -site testing was conducted at four sites and grab samples were collected at three sites
in the upper drainage network (Table 4-6, Table 4-7). Two additional grab samples were collected
along the mainstem of Sandy Creek Tributary A the daylight point as well as at a location further
downstream near University Drive. Field parameters were also measured at each grab sample
location.
Water quality testing results are described below:
Site B
o Elevated ammonia, CBOD, fecal coliform, and HF183 results strongly indicate that raw
sewage was flowing into the stormwater manhole.
Site D/E
o At the upstream site along this tributary (Site D), grab sample and onsite testing results do
not indicate any specific sources of pollution.
o Further downstream (Site E), ammonia, fecal coliform, and HF183 concentrations appear to
increase. This indicates a potential source of pollution entering the tributary along the piped
section of the stream.
Pet waste and dumpster leachate observed within the vicinity of this downstream sampling
location may be another source of pollution.
• Site F/G
Between the daylight point (Site F) and the University Drive road crossing (Site G), ammonia
and HF183 values decrease. If raw sewage from Site B is reaching Sandy Creek Tributary A,
this may indicate that this source of pollution becomes diluted in downstream reaches.
However, fecal coliform concentrations increase. Therefore, it is possible that a non -human
source of fecal contamination is reaching the stream between these two points through
stormwater runoff.
Site I
o On -site testing only was conducted on dry weather flow collected from a drop inlet near a
newly developed shopping center and apartment complex.
o The origin of this colorless and odorless dry weather flow was not identified by field staff.
o However, higher chlorine concentrations may indicate the source of this flow is treated
water.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Section 4
I Carbonaceous
Biochemical
Fecal
Dissolved
Specific
Temp -
Collection
Ammonia,
HF183,gene Oxygen,
ORP,
Site
Site Type
Oxygen
Coliform,
pH
Conduct.,
erature,
Date
mg/L as N
copies/mL mg/L
mV
Demand,
CFU/100
mL
MS/cm
C
mg/L
B
Upper Drainage Area
10/20/2021
7.8
60.6
6,000
3,37E+06
4.97
-7.3
6.94
0.580
21.8
D
Upper Drainage Area
10/20/2021
0.05
1
150
1.46E+01
5.31
148.4
6.63
0.148
14.3
E
Upper Drainage Area
10/21/2021
0.11
1
80
1.04E+03
6.76
174.1
6.63
0.258
15.7
F
Mainstem
10/21/2021
0.265
1
65
8.08E+03
6.02
13.3
7.23
0.278
19.4
G
Mainstem
10/21/2021
0.05
1
1,580
4.84E+02
5.22
40.8
6.89
0.263
15.9
Table 4-7. On
-Site Testing
Results
Ammonia,
Chlorine,
Copper,
Fluoride,
Turbidity,
Site
Site Type
Collection Date
mg/L as N
mg/L
mg/L
mg/L
FAU
B
Upper Drainage Area
10/20/2021
>2.5
0.03
0.01
ND
67
D
Upper Drainage Area
10/20/2021
0.04
0.03
ND
ND
21
E
Upper Drainage Area
10/21/2021
0.12
0.02
0.02
0.2
8
1
Upper Drainage Area
10/21/2021
ND
0.12
ND
ND
8
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 4
4.6 Microbial Source Tracking
Microbial source testing was conducted on samples from sites B, D, E, F, and G (Table 4-6). Of the
five grab samples, the samples from site B had the highest levels of both fecal coliform
(6,000 cfu/100 mLO and the HF183 marker *3.37E+06 gene copies/mL). The literature indicates
that raw sewage typically has concentrations in the range of 1E+06 to 1E+08 copies/mL (Ahmed
and others, 2016; Feng and McLellan, 2019). Hence, the fecal contamination at Site B was
confirmed to have HF183 concentrations levels consistent with raw sewage with relatively little
dilution. The other four samples had detectable levels of the HF183 marker, but at concentrations
much lower than site B (Table 4-6, Table 4-7). Among these four samples, there was no apparent
correlation between the HF183 marker the fecal coliform concentrations (Figure 4-36).
1.00E+07
• B
1.00E+06
1.00E+05
i=
N
2 1.00E+04 s F
C_
0
V
- 1.00E+03 s E
00 • G
LL
= 1.00E+02
1.00E+01 6 D
1.00E+00
1. E+00 1. E+01 1. E+02 1. E+03 1. E+04
Fecal Coliform (cfu/100 rnl-)
Figure 4-36. HF183 gene marker versus fecal coliform concentration.
The scientific literature indicates that HF183 concentration in most stormwater and surface waters
can vary over several from orders of magnitude from 1E+00 to 1E+03 (Ahmed and others, 2016).
Hence, the HF183 concentrations observed during this study within the wide range expected for
stormwater and surface water in most locations, except for the sewer leak at Site B. Although the
test method for HF183 does not always exclusively detect human pollution, it has a human
specificity of greater than 90 percent (LISEPA, 2019). The widespread detection of the HF183
marker —including in Sandy Creek Tributary A itself —suggests that sewer leaks such as the one found
at Site B are partly responsible for elevated fecal coliform concentrations in the creek. However, the
lack of correlation between fecal coliform and the human marker HF183 suggests that non -human
sources such as pet waste (observed at Site E) or wildlife (abundant in the stream bottom) are also
partly responsible for the observed fecal coliform levels.
For example, Site G in Sandy Creek Tributary had a high fecal coliform concentration
(1,580 cfu/100 mQ, but a relatively low HF183 concentration (4.84E+02). The upstream sewer leak
is unlikely to be the only or principal source of fecal coliform at this location, as further evidenced by
lower fecal coliform concentrations at the upstream daylight point daylight point at Martin Luther
King Jr Parkway. A local wildlife source might be elevating fecal coliform concentrations at Site G.
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Section b
Summary of Pollutant Sources and
Causes
This study has demonstrated that water quality issues in Sandy Creek Tributary A are caused by (1)
external pollution to the stream; and (2) in -stream hydrologic conditions. Both of these factors are
important controls on the ambient DO concentrations, and their combined effect causes lower DO
concentrations than either factor would alone. The low in -stream flows and velocities are partly
natural but have been exacerbated by development -associated hydrologic alterations. Similarly,
bacteria appear to be derived both from sewer leaks and other sources such as wildlife. The external
pollutant sources and in -stream conditions are summarized in separate subsections below.
5.1 External Pollutant Sources
The investigation of the upper drainage area discovered multiple locations of dry weather flow or
observable pollution. One of these sites (location B) was confirmed to be a raw sewage leak. The
high CBODS, ammonia, and human -derived fecal contamination from this leak is a contributor to the
low DO and detectable ammonia at the daylight point of Sandy Creek Tributary A. A relatively high
proportion (4 of 5) of the stormwater sewer sites that were inspected had observable dry weather
flow. This suggests that there might be other sites with dry weather flow or pollution in the upper
drainage area, and that the drainage area should be prioritized for DWS under the City's Illicit
Discharge Detection and Elimination (IDDE) program. This recommendation is discussed further in
section 6.3.
A simple calculation was performed to predict the in -stream DO sag (e.g., difference from DO
saturation) that a combined 0.1 cfs of sewer leaks might cause in Sandy Creek Tributary A
(Table 5-1). The Streeter -Phelps formulation assumes complete mixing of an effluent in a stream and
predicts the magnitude and location of the downstream DO sag. This calculation should not be
considered an accurate estimate of the DO sag in Sandy Creek Tributary A, but rather a screening -
level inquiry into whether sewage leaks of this magnitude have the potential to significantly affect
the DO of the stream.
Category
Parameter
Leak flow
Value
0.1 cfs
Notes
Assumed for screening purposes
Assumed input
parameters
Stream background flow
0.8 cfs
Combined with the assumed leak flow, this equals the streamflow
observed near daylight point in Oct. 2020
Leak CBOD5
60.6 mg/L
Value measured in sample from site B Oct. 2021
Stream background CBOD5
0.5 mg/L
Assuming low background value
Leak ammonia N
7.8 mg/L
Value measured in sample from site B Oct. 2021
Stream background
0.1 mg/L
Assuming low background value
ammonia N
Stream width
17 feet
Based on stream measurements near daylight point, Oct. 2020
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- Sandy Creek Tributary A Section 5
Table 5-1. Screening
-Level
Streeter Phelps DO Sag Calculation
Category Parameter
Value
Notes
Stream depth
2 feet
Based on stream measurements near daylight point, Oct. 2020
Saturation DO conc.
7.8 mg/L
Based on hot seasonal conditions
In -stream reaeration coeff.
0.33/day
Based on Churchill equation
Ratio of ultimate to 5-day
1.2
Typical value for untreated wastewater
oxygen demand
Ultimate oxygen demand
0.35/day
Typical value for untreated wastewater
decay rate
Results Maximum DO sag
4.2 mg/L
Maximum difference from DO saturation
Distance downstream of
1.7 miles
maximum DO sag
Minimum in -stream DO
3.6 mg/L
This result is sensitive to inputflow assumptions and could be <1 mg/L if
concentration
the background streamflow was very low (-0.1 mg/Q
The results of the screening -level calculation (Table 5-1) confirm that 0.1 cfs of sewage leaks could
cause DO concentrations in Sandy Creek Tributary A to fall below the water quality criterion of
5 mg/L. The results of the calculation are sensitive to the leak flow rate, streamflow, and resulting in -
stream reaeration coefficient, which are uncertain or variable. If the background streamflow was
essentially stagnant or of similar magnitude as the leak itself, combined leaks of this magnitude
could cause DO concentrations <1 mg/L. Hence, the results of the calculation are not only sensitive
to the assumed magnitude of the pollution source but to the extremely low base flows of the stream.
Another interesting result of the screening -level DO sag calculation is the prediction that the
maximum DO sag could occur ~1.7 mile downstream of the sewage leak. The leak discovered at
site B was only about —1 mile upstream (in pipe distance) of the stream daylight point. Hence, this
result would be consistent with DO concentrations continuing to decrease downstream of the
daylight point, which what was observed during the October 2020 field investigations.
A final note on the screening -level DO calculation is that the in -stream CBOD5 was predicted to be
the —4 mg/L at the point of maximum DO sag. This is similar to the maximum CBOD5 values
(3-4 mg/L) measured in Sandy Creek Tributary A during the October 2020 field work, although most
values were less than the reporting values of 2 mg/L. A potential lesson is that under conditions of
very low stream flow, high CBOD5 and ammonia concentrations would not be needed to explain low
DO in the creek. Rather, even CBOD5 values in the lower single digits could explain significant DO
sags in the stream.
Other discrete pollution sources observed in the watershed included a likely water line break, pet
waste, and a leaking dumpster. The widespread detection of the HF183 marker demonstrated that
human sources contribute to elevated bacteria in Sandy Creek Tributary A. But non -human sources
such as pet waste and wildlife are also probably important, as evidenced by a lack of correlation
between HF183 and fecal coliform and visual observation of pet waste and wildlife droppings.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 5
5.2 Stream Morphology and Processes
Relevant instream factors include both hydrologic characteristics and water quality processes,
discussed in subsections below.
5.2.1 Hydrologic Characteristics
Sandy Creek Tributary A has many of the common characteristics of streams with higher impervious
drainage areas and high rates of urban runoff. These include unstable banks, channelization, and a
shifting streambed characterized by areas of scour and areas of sedimentation. Base flows to the
channel appear to be very low, as evidenced by the low flow rates measured on October 5, 2021.
This is typical of impervious watersheds with flashy hydrology - high but short-lived peak flows during
storms followed by low baseflows. Streams in Triassic basins tend to have flashy hydrology and low
baseflows due to poorly conductive soils (Dreps, 2011), so the high imperviousness of the watershed
is likely exacerbating a natural condition. As stated by USGS (2001):
The area ... with the lowest potentials for sustained base flows is underlain by the Triassic basin in
parts of Durham, Wake, and Chatham Counties. Typically, these soils are derived from basalt and
fine-grained sedimentary rocks that allow very little infiltration of water into the shallow aquifers
for storage and later release to streams during periods of base flow.
The naturally -low base flow rates in the Sandy Creek Tributary A have likely been decreased further
by the high imperviousness of the upper watershed, which further reduced infiltration and recharge
of the surficial aquifer.
In addition to the low baseflow rates, stagnant conditions are caused by channel obstructions
including rip rap, logs, and sandy sills. These have caused much of the stream to take the form of
elongated pools with very low velocities. Blaszczak and others (2019a) found that geomorphic
changes to urban stream channels were a major factor in causing stream hypoxia in the North
Carolina Piedmont. These authors associated urban stream hypoxia with low gradient channels, low
baseflow, heterotrophy, and channel features that dissected the stream into pools of high residence
time. Sandy Creek Tributary A fits this profile very well.
During the October 2020 field event, most side channels and stormwater outfalls were not
contributing observable flow to the stream. Under dry weather conditions, most of the flow in Sandy
Creek Tributary A is already present at the stream daylight point, as evidenced by the fact that the
highest streamflow was measured at this location. The stream actually had lower streamflow
downstream of the daylight point. This suggests that much of the tributary is either a losing stream,
or that it has both losing and gaining subsegments. Where the channel is highly braided, visual
observations indicate that the streamflow can be bifurcated among multiple channels, and
streamflow is likely to both enter and emerge from the sandy bed sediments.
The thermal imaging study suggested that most groundwater inputs to Sandy Creek Tributary A are
diffuse and low in magnitude, rather than discrete or high flow seeps. However, this study did
confirm that groundwater inputs contribute to low dissolved conditions in the creek. Site 29 of the
thermal imaging study was representative of other sites where low -DO groundwater enters the
stream. Other evidence for exchange with shallow groundwater includes (1) the freshening of water
and decrease of sodium chloride concentrations from the daylight point to just upstream of Garrett
Road; (2) abundance of iron oxidizing bacteria, which are common in streams that receive low -DO
groundwater inputs; and (3) an increase in streamflow in the downstream segment near Garrett
Road. Therefore, it is expected that groundwater exchange and hyporheic processes are important to
water quality in the tributary.
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Section 5
5.2.2 Water Quality Processes
The longitudinal profile of water quality in Sandy Creek Tributary A as measured in October 2020
provides insights into water quality processes occurring in the stream. Some changes downstream in
water quality can be attributed simply to dilution from groundwater or diffuse inputs that are fresher
than the headwater flow. This probably accounts for the downstream decrease in conservative
parameters such as specific conductance, sodium, and chloride. However, other water quality
processes in the stream appear to include heterotrophic oxygen demand, ammonia
uptake/nitrification, denitrification, iron and manganese oxidation/precipitation, and the generation
or input of DOC (Table 5-2).
Process
Lines of Evidence
Contamination from sources in upper drainage
Observed sewer leak and other pollutant sources in upper drainage area
causing poor water quality at stream daylight
Detectable ammonia concentration, high fecal coliform at daylight sampling station,
point
low DO
• Widespread detection of HF183 marker
Entry of low DO groundwater/diffuse flows.
Downstream decrease in DO and conservative parameters such as specific
conductance, sodium, and chloride.
• Abundant iron -reducing bacteria.
• Thermal imaging of groundwaterfed pool contributing low DO waterto main channel.
Heterotrophic respiration; decay of oxygen-
Downstream decrease in DO from daylight point and stream riffles.
demanding substances
Low orthophosphate concentrations, suggesting biological uptake.
Downstream decrease in ammonia concentrations
Downstream decrease in nitrate+nitrate concentrations
Ammonia uptake/nitrification
Nitrate uptake/denitrification
• Literature shows denitrification common in hyporheic zone
Abundant iron -reducing bacteria.
Iron and manganese oxidation/precipitation.
• Downstream decrease in iron and manganese.
Generation or input of dissolved organic carbon I • Downstream increase in DOC/TOC.
• Could be caused by both in -situ decay of plant material and input of high DOC
groundwater
Although ammonia and CBOD5 concentrations were relatively low in Sandy Creek Tributary A, the
persistently low DO concentration in Sandy Creek Tributary A provides direct evidence that the
oxygen demand in the stream is greater than the reaeration rate. As discussed in section 5.1, under
very low streamflow conditions, reaeration rates can be sufficiently low that even relatively low rates
of oxygen demand are sufficient to maintain low DO concentrations.
The simultaneous decrease in both ammonia and nitrate shows the potential complexity of the water
column and hyporheic processes in the stream. Ammonia nitrification is a relatively rapid process in
streams and can occur even under relatively low DO concentrations (<1 mg/L) (Stenstrom and
Poduska, 1980). Denitrification (i.e., conversion of nitrate to nitrogen gas) is a common process in
the hyporheic zone where surface water and shallow groundwater mix (Harvey and others, 2013),
and nitrate can also be reduced by bacterial or algal uptake.
The low orthophosphate concentrations indicate that in -stream biological processes are likely
phosphorus -limited rather than nitrogen -limited, which is common for freshwaters. At the time of the
field work, there was relatively little filamentous algae noted in -stream but abundant iron -oxidizing
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 5
bacteria as noted in previous sections. Much of the stream bottom is relatively well -shaded, such
that light may be a strong limitation on instream algae growth. The low daytime DO concentrations
provide additional evidence of low in -stream algal levels. Hence, we infer that heterotrophic
processes such as bacterial respiration are more important to the stream chemistry than autotrophic
processes such as in -stream photosynthesis.
Blaszczak and others (2019b) found that sewer density near streams correlated with sulfate
concentrations in streams in the Raleigh -Durham area. This study did not cite a sulfate threshold by
which to detect the influence of leaky sewers on streams. The mean sulfate concentration measured
in Sandy Creek Tributary A was 21 mg/L both in the historical monitoring database and in the
October 2020 results. This is only slightly higher than Blaszczak and others (2019a) reported values
of the mean sulfate in Triassic basin watersheds (16.0 mg/L) and highly developed watersheds
(18.5 mg/L). Hence, it can only be concluded that the sulfate concentrations in Sandy Creek
Tributary A are typical for Triassic basins and those draining highly developed areas.
5.2.3 Summary of Conceptual Model
Multiple pollutant sources —including a least one significant sewer leak —contributed to low DO,
detectable ammonia, and elevated bacteria in Sandy Creek Tributary A at the daylight point near
Martin Luther King Jr Parkway. DO concentration continues to decrease downstream from that point
due to ongoing oxygen demand, low reaeration rates, and inputs of low -DO groundwater. The low
rates of baseflow are typical of Triassic basin streams, but are exacerbated by the high
imperviousness of the watershed. Similarly, in -stream modifications such as channel widening and
obstructions cause stagnant flow conditions and lower stream reaeration rates. Water quality
improvement would thus be dependent on reduction of external pollution sources and improvement
of in -stream flow/velocity conditions.
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Section 6
Recommended Improvement
Strategies
As discussed in previous sections, the poor water quality of Sandy Creek Tributary A is caused by
both external pollution sources and internal stream conditions. Therefore, recommended strategies
address these two areas of potential improvement. The continued application of MS4 control
measures is also necessary to identify and correct additional pollution sources.
6.1 Addressing Known Pollutant Sources
This category of potential improvements includes fixing/eliminating the pollutant sources that were
discovered as part of the upper drainage area investigation of Sandy Creek Tributary A. These
include:
• The sanitary sewer leak at site B
Leaking dumpsters and pet waste at site E
• The water main break at site H
Small amounts of dry weather flow were also observed at sites C and I, of unknown origin. Therefore,
it is also recommended that the City IDDE program include these sites on future inspection
schedules and perform additional investigation if the flows appear to be significant and persistent.
Additional recommendations related to the IDDE program are provided in section 6.3.
6.2 Potential In -Stream Projects
The three reaches of stream channel (Martin Luther King Jr. Parkway to Ivy Creek Boulevard; Ivy
Creek Boulevard to University Drive; and University Drive to the confluence with Sandy Creek) have
very little riffle/pool sequence throughout and are dominated primarily by long stretches of stagnant
pools. These stream reaches are actively eroding by evidence of vertical banks and a widening and
incising stream channel. Points along the stream are impacted by fallen trees from the widening
channel resulting in debris blockages that have created long sections of pooled water and lack of
riffles. Eroding streams experience a common sequence of physical adjustments following
disturbance. This process of channel evolution is the stream's way of adjusting to upstream
conditions before it reaches a state of equilibrium. It appears this stream is in the early stages of this
evolution process where the channel is actively widening and incising. There are areas of
aggradation which then begin the process of the stream establishing a meandering base flow
channel within the widened corridor.
Using the City of Durham GIS storm drain data, the approximate slope of the stream from Martin
Luther King Jr. Parkway to the confluence of Sandy Creek is 0.3 percent. This is a relatively flat slope
for a stream and is on the lower range of a Rosgen "C" type stream (0.1 percent to 3.9 percent).
Rosgen "C" type streams are the typical stable stream type in this geographic area and consist of
riffle/pool sequences in a meandering pattern with pools located in the meander bends and riffles
connecting the pools.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
Mixing and turbulence (flow over riffles or drops) in a stream channel improves the overall DO in a
stream. As noted earlier, the stream consists primarily of long pools with standing water, mostly due
to stream widening/incising and instream debris blockage. Removing these areas of stagnant water
and creating mixing or turbulence zones in the stream can help increase the DO levels. Based on the
current evolutionary stage of the stream, two methods to improve overall flow would be full stream
restoration or identifying appropriate areas where grade control structures (cross vane) or riffles
could be installed.
There are essentially four stream restoration options when considering how to repair degraded
streams: Priority 1, Priority 2, Priority 3, and Priority 4. Priority 1 restoration generally includes
connecting the bankfull stage with the historical floodplain elevation - typically includes replacing
the incised channel with a new, stable stream at a higher elevation (Figure 6-1).A Priority 2
restoration generally includes creating a new floodplain and stream pattern with the stream bed
remaining at the present elevation - typically includes realignment of the stream (Figure 6-2).
Priority 3 restoration includes widening the floodplain at the existing bankfull elevation - typically
without shifting the stream pattern but remaining in its current corridor (Figure 6-3). Lastly, a Priority
4 restoration includes stabilizing existing streambanks in place using various stabilization
techniques to amour the bank in place. This type of restoration does not correct dimension, pattern,
or profile issues and is used mostly for point repair along streams.
Figure 6-1. Priority 1 Restoration (Courtesy North Carolina Stream Restoration Institute and
North Carolina Sea Grant)
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
Figure 6-2. Priority 2 Restoration (Courtesy North Carolina Stream Restoration Institute and
North Carolina Sea Grant)
Figure 6-3. Priority 3 Restoration (Courtesy North Carolina Stream Restoration Institute and
North Carolina Sea Grant)
With established elevations of existing culverts and road crossings and consideration of impacting
floodplain elevations, Priority 1 restoration was not seen to be practical or feasible for these reaches.
Since Priority 4 restoration does not address dimension, pattern, or profile, this option is not
practical for improving velocities for improved DO. Stream restoration for these three reaches would
most likely include a combination of a Priority 2 restoration and Priority 3 restoration and are
overviewed in section 6.2.1. Both selected restoration options would create a narrower baseflow
channel as part of the reconfigured cross section for the stream. By restoring the stream and
speeding up the evolutionary process, the pattern and profile can be manipulated to create a stable
stream profile with riffles to produce the higher velocities or turbulence to increase DO. For the
purposes of this discussion, the channelized portions of the stream are assumed to receive the
Priority 2 restoration while the portions of the stream with existing meander and sinuosity would
likely receive the Priority 3 restoration. Additionally, any portions of stream that are in narrow
corridors and adjacent to parallel utilities (sanitary sewer), a Priority 3 restoration is assumed due to
those restrictions for realigning the stream pattern.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
6.2.1 Priority 2/Priority 3 Stream Restoration
Reach Restoration - Martin Luther King Jr. Parkway to Ivy Creek Boulevard
The stream reach between Martin Luther King Jr. Parkway to Ivy Creek Boulevard is approximately
1,250 linear feet with an approximate slope of 0.3 percent. This reach is in a narrow corridor with a
parallel sanitary sewer main on the right bank (looking downstream) and a fill slope with buildings
and parking lot on the left. The stream is incised and widened with severe active bank erosion and
areas of fallen trees in the stream - a Priority 3 restoration is assumed for this reach. Stable Rosgen
"C" type streams can have anywhere from 30 percent to 50 percent of the stream length be riffles. If
restored, this would result in an average riffle slope of 1.0 percent to 0.6 percent, respectively.
Reach Restoration - Ivy Creek Boulevard to University Drive
The stream reach between Ivy Creek Boulevard to University Drive is approximately 700 linear feet
with an approximate slope of 0.2 percent. The upper half of the reach has a meandering pattern with
a parallel sanitary sewer main along the left bank; bank erosion is migrating toward several sanitary
sewer manholes. The lower half of the reach is channelized with a built-up berm along the floodplain;
a sanitary sewer main is located to the left of the stream but, further away. A Priority 3 restoration is
assumed for the upper reach since there is some existing meander/sinuosity to the stream, and a
Priority 2 restoration is assumed for the lower half to remove the channelized length of stream. By
restoring to a Rosgen "C" type stream, riffle slopes would average 0.7 percent to 0.4 percent
depending upon the riffle to pool ratio.
Reach Restoration - University Drive to Sandy Creek Confluence
The stream reach between University Drive and the confluence with Sandy Creek is approximately
4,100 linear feet with an approximate slope of 0.3%. In general, this reach of stream has more
sinuosity and meandering and is incised and widened but with lower bank heights, multiple areas of
debris in the stream impeding flow, and multiple braided channels in the floodplain area. Multiple
sanitary sewer mains cross the stream at approximately the mid -point of the reach between
University Drive and Garrett Road, with one of the crossings exposed. A Priority 3 restoration is
assumed for this entire reach, utilizing the current sinuosity and establishing a new cross section
throughout. By restoring to a Rosgen "C" type stream, riffle slopes would average 1.1 percent to
0.6 percent depending upon the riffle to pool ratio.
6.2.2 Forced Riffle Enhancement
The second option includes creating riffles at specific points along the existing stream alignment.
This would include installing riffles in existing straight sections of the stream and manipulating the
stream bed profile to force a steeper slope on the profile (Figure 6-4). Since the streams are
widened, these riffle sections would have a narrowed baseflow width and include a bankfull bench
on either both sides or one side of the stream bank. The riffle would be forced by placing a cross
vane, or similar grade control structure, at the downstream location of the riffle. This will help to hold
the grade of the riffle in an unstable stream. These riffles would be located at areas of debris
blockage where there is a grade drop between the upstream and downstream elevations of the
blockage and in straight sections of the stream where riffles naturally occur. Identifying the exact
location and elevations for these riffles would require detailed survey of the stream bed profile and
then topographic survey of the stream bed and banks where the riffles could be installed.
For the purposes of this report, it was assumed that only 10 percent of each reach length would be
suitable for a forced riffle enhancement. The average length of each riffle was also assumed to be
15 linear feet so a quantity of grade control structures could be assumed (one per riffle placed at the
end of the riffle) for the cost opinion in section 6.2.3.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
Figure 6-4. Schematic of reducing width of stream bed to create basef low riffle channel.
6.2.3 Cost Opinion
A Class 5 Opinion of Probable Construction Cost (OPCC) was developed for each reach. A Class 5
estimate is defined as a conceptual planning level estimate. This level of estimate has an accuracy
range of -50 percent to +100 percent based on the stage of the project and to account for the
volatility of the current market. Detailed data collection, analysis, and design would be required to
provide a more refined OPCC for these projects.
The cost opinion for the restoration was developed based on a linear foot cost for each priority type.
The survey, permitting, and design was assumed to be 20 percent of the construction costs and a
30 percent contingency was applied. Table 6-1 below provides an OPCC of the Priority 2 and 3
restoration options at the three reaches.
Martin Luther King Jr
Item Parkway to Ivy Creek Ivy Creek Boulevard to University Drive to Sandy
University Drive Creek
Boulevard
Linear Feet of Stream
- Priority 2
Linear Feet of Stream
- Priority 3
Cost per Linear Foot -
Priority 2
Cost per Linear Foot -
Priority 3
Priority 2 Subtotal
Priority 3 Subtotal
Combined Subtotal
1,250
350
350
0
0
4,100
$500
$500
$500
$350
1 $350
1 $350
$625,000
$175,000
$0
$0
$122,500
$1,435,000
$525,000
$297,500
$1,435,000
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Section 6
Martin Luther King Jr
Ivy Creek Boulevard to
University Drive to Sandy
Item
Parkway to Ivy Creek
University Drive
Creek
Boulevard
Survey/Permitting/ Engineering (20%)
$125,000
$59,500
$287,000
Subtotal
$ 750,000
$357,000
$1, 722,000
Contingency (30%)
$2225,000
$107,100
$516,600
Total
$975,000
$464,100
$2,238, 600
The forced riffles are based on a linear foot cost that includes clearing, erosion control and pump
around, earthworks, one grade control structure per riffle, and revegetation. Since these will be
mostly spot treatments along the stream reaches, the survey, permitting, design, and modeling were
assumed to require less effort and was set at 15 percent of the construction costs, or a minimum of
$40,000; a 30 percent contingency was also applied. Table 6-2 below provides an OPCC of the
forced riffles at the three reaches.
Table 6-2. Opinion of Probable
Martin Luther King Jr Ivy Creek Boulevard to University Drive to Sandy
Item Parkway to Ivy Creek
University Drive Creek
Boulevard
Total Linear Feet of Riffle 1251 702 4103
Cost per Linear Foot $850 $780 $870
Subtotal $106,250 $54,600 $356, 700
Survey/Permitting/Engineering (15%)4
Gihtntni
Contingency (30%)
$40,000
$146,250
$43,900
Total $190,150
'Assumed (8) riffle complexes with (8) grade control structures
2Assumed (4) riffle complexes with (4) grade control structures
3Assumed (27) riffle complexes with (27) grade control structures
4Assumed 15% of construction costs with a minimum of $40,000
6.3 Other MS4 Control Measures
$40,000
$53,500
$94,600
$410,200
$28,400
$123,100
$123,000
$533,300
The City of Durham is a Phase 1 MS4 community and is authorized by the State of North Carolina to
discharge stormwater under NPDES permit NCS000249. Clean Water Act regulations require MS4
communities to implement six minimum control measures to reduce pollutant discharges: (1) public
education and outreach, (2) public participation/ involvement, (3) illicit discharge detection and
elimination, (4) construction site runoff control, (5) post -construction runoff control, and (6) pollution
prevention/ good housekeeping for municipal operations. North Carolina also requires Phase 1 MS4
communities to implement three additional measures: (7) a program to monitor and control
pollutants in stormwater discharges to municipal systems, (8) water quality assessment and
monitoring, and (9) total maximum daily load programs. In addition to the permit itself, the City's
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
approaches to control measures are described in the City's Stormwater Management Plan (SMP)
(City of Durham, 2019) and annual reports (e.g., City of Durham, 2021).
Sandy Creek Tributary A has a highly developed watershed, and this study confirmed the potential for
runoff and pollution from the stormwater sewer system to adversely impact the stream. If
implemented consistently over time, MS4 control measures could reduce pollutant loading to the
stream. The watershed might need to be prioritized for some control measures, and some of these
measures might need to be applied in a focused manner in this watershed. The subsections below
describe the City's existing control measures and discuss manners in which these actions could
reduce PAH and metals loads to surface waters.
6.3.1 Public Education and Outreach
The City's SMP implements various types of public education and outreach to reduce or prevent
stormwater pollution, most of which are under the leadership of the City's Public Education
Coordinator. These include:
• Promotion and maintenance of the Stormwater Services Website
(www.durhamnc.gov/stormwater) that provides information on water quality and pollution
prevention
• Financial support and contribution of information material to the Clean Water Education
Partnership (www.NC-cleanwater.org)
• Distribution of public education materials (e.g., brochures, flyers, videos, utility bill inserts) to
target groups
• Organization or participation in community events and school programs
• Outreach through traditional media (newspaper articles, public service announcements) and
social media (e.g., Don't Waste Durham Facebook site)
The City's target pollutants for stormwater education include bacteria, nitrogen, phosphorus, low DO,
turbidity, copper, and zinc. The City's outreach materials on preventing bacteria and low DO in
streams focus on proper disposal of pet waste, grease, household/yard wastes, and reporting
potential pollution sites. These activities should continue to be applied to the Sandy Creek
Tributary A subwatershed.
6.3.2 Public Involvement
As with public education and outreach program, the public involvement opportunities could serve to
reduce a wide variety of pollutants. The pollution reporting hotline is an especially important
opportunity for the public to inform City of pollutant sources or discharges that could include bacteria
or low DO sources. Similarly, odor complaints can help identify sewer leaks, as was the case at site B
in the upper drainage of Sandy Creek Tributary A. Other City Programs to involve the public include:
• Offering of volunteer opportunities such as stream cleanup campaigns, adopt -a -drain, and
adopt -a -street
• Soliciting public comments on the annual stormwater reports and the stormwater management
plan
• Holding public notice, meetings, and opportunities for input on watershed plans, major
construction projects, retrofit plans, ordinance revisions, etc.
• Promoting and maintaining a stormwater pollution reporting hotline
• Support of the non-profit group Keep Durham Beautiful
• Presentation to the City -County Environmental Affairs Board
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
6.3.3 Illicit Discharge Detection and Elimination
Various illicit discharges could be sources of low DO and elevated fecal coliform to surface water,
including wastewater leaks, illegal discharges, and improper disposal of yard waste. As previously
noted, a relatively high proportion of the sites that were inspected in the upper drainage area of
Sandy Creek Tributary had observable dry weather flow. This project resulted in the indication of
specific illicit discharges to investigate and eliminate, as discussed in section 6.1. Previous City IDDE
inspection also identified illicit discharges to eliminate (Figure 2-4). However, there might be other
sites with dry weather flow or pollution that have not yet been discovered. And routine maintenance
issues with aging infrastructure will cause new discharges to periodically occur. As demonstrated in
section 6.5, Sandy Creek Tributary A (and probably other Triassic basin streams) are vulnerable to
DO impacts from sewer leaks due to very low base flow and reaeration rates.
In order to address these potential illicit discharge sites, the City could prioritize the Sandy Creek
Tributary A watershed its longstanding IDDE program to be applied to the Sandy Creek Tributary A
watershed. This program includes procedures and schedules for screening outfalls, investigating
concerns, training municipal employees, fixing leaks, and reporting illicit discharges to the State if
necessary.
Separate from the IDDE program, City's Department of Water Management (DWM) also performs
routine sewer inspections as required by City's wastewater collection system permit. Generally, pipes
are cleaned by hydro jetting, inspected by camera, and assigned scores that indicate the need for
maintenance or repairs. Due to the time and cost involved, it is only practical for the City to fully
inspect a small percentage of its entire sanitary sewer system in any one year. It would be
recommended that the City stormwater staff coordinate with DWM to ensure that the Sandy Creek
Tributary A watershed is prioritized for inspection reasonably soon. It would especially be useful to
inspect sewers in the upper drainage area as well as sewer lines buried below the stream bed.
6.3.4 Construction Site Run -Off
Controlling construction site runoff is most directly correlated with mitigating sediment runoff and/or
erosion. Construction site runoff is not considered a major stressor to Sandy Creek Tributary.
However, suspended sediment correlates with many other pollutants including bacteria and metals,
and sedimentation can degrade in -stream functions. Hence. construction site runoff controls are an
important protective measure for any stream.
The Durham County Stormwater and Erosion Control Division has delegated authority over an
erosion control program that would apply to most private construction projects within the Sandy
Creek Tributary A watershed. Permits are required for activities that disturb 12,000 square feet or
more, and an approved erosion control (ESC) plan is required for activities that disturb more than
20,000 square feet. Similarly, the NC Department of Transportation (NCDOT) is responsible for
erosion control on state road construction projects. The Land Quality Section of the NC Division of
Energy, Mineral and Land Resources regulates land disturbing activity for construction projects that
have public funding, projects by agencies with the power of eminent domain, and projects by state
and federal agencies. The City's SMP cites all these programs as components of construction site
runoff controls.
6.3.5 Post -Construction Runoff
The City's SMP describes various management practices that the City employs to control post -
construction pollutant loading. The most important of these is an ordinance (Chapter 70, Article X,
Sections 70-736 through 70-744) that authorizes a post -construction stormwater control program.
This code section contains post -construction performance standards applicable throughout the City.
6-8
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
Within the Jordan Lake Basin (including the Sandy Creek Tributary A watershed), the thresholds for
limits of application of the stormwater pollutant requirements are:
1.0 acres of land disturbance (limited residential)
1.0 acres of land disturbance (multifamily and other)
The City program was developed primarily to control nutrients (nitrogen and phosphorus) and TSS.
While there are no specific nutrient export loading rate limits for activities that exceed disturbance
thresholds in the Jordan Lake basin, the City requires post -development controls that limit loading
nitrogen and phosphorus from that loading area for such development which is not otherwise
exempt. The program regulates post -construction control measurements by utilizing design
standards of the North Carolina Division of Water Quality Stormwater Best Management Practice
(BMP) Manual and City's own addendum to this manual. Common post -construction BMPs include
wet ponds, dry ponds, bioretention cells, and constructed wetlands. Permeable pavers, green roofs,
infiltration practices, and vegetated swales are also employed to treat small areas.
The upper drainage area of Sandy Creek Tributary A is largely built out, but the post -construction
controls would apply as this area is redeveloped over time. As this occurs, it would be recommended
that the City work with developers to select practices that would increase baseflow rates to Sandy
Creek Tributary A. Examples of such practices include:
• Conversion or existing impervious surface to green space.
• Direction of stormwater runoff to green space
• Infiltration practices such as pervious pavers, bioretention, infiltration basins, and dry wells
The City of Durham also uses several non-structural BMPs to mitigate the effects of development,
including Natural Resource Protection that address tree protection and tree coverage, floodplain
protection, stream buffer protection, steep slope protection, and wetlands protection. The City's Park
and Recreation Department and Planning Department manages a program for maintaining and
increasing open space. This program concentrates on preserving environmentally sensitive and
natural resource areas within the City including wetlands and riparian buffers. The City's Critical Area
Protection Plan (CAPP) identifies privately -owned parcels with high -quality riparian buffers that might
be conserved or protected. According to the New Hope River and Little Creek Watershed
Improvement Plan (AECOM, 2020), 22 of the 103 "keystone" parcels within this area of study are in
the Sandy Creek watershed.
The NCDOT is subject to a specific state regulation under the Jordan Lake Rules (15A NCAC
02B .0262-.0273). In accordance with this regulation, NCDOT has developed a Jordan Lake GREEN
Program. This program relies on a combination structural BMPs, non-structural BMPs, riparian buffer
protection, education programs, and nutrient offset payments to reduce nutrient loads to Jordan
Lake and its tributaries, such as Sandy Creek Tributary A.
6.3.6 Pollution Prevention and Good Housekeeping for Municipal Operations
The City's Stormwater Management Plan lists a large number of pollution prevention and good
housekeeping programs for municipal operations. Examples include the development of site
pollution prevention plans, spill response procedures, inspections and maintenance, and staff
training. The City maintains an inventory of 32 municipal operation facilities, none of which are
located in the Sandy Creek Tributary A watershed. Similarly, there are no fire stations within this
watershed, but there is one police station and several public schools. Some relevant programs that
could reduce pollution in the watershed include routine inspections and maintenance of:
• City streets/roads, and parking lots (e.g., prevent use of coal tar -based pavement sealants)
• Sanitary sewer infrastructure, especially those within Sandy Creek Tributary A's floodplain
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Section 6
• Stormwater infrastructure, including periodic removal of accumulated sediment that could
contain a variety of pollutants
6.3.7 Program to Monitor and Control Pollutants
Section 7.8 of the City's SMP describes measures that the City undertakes to monitor and control
pollutants entering the MS4. Most of these relate to the inspection and control of pollution of
permitted industrial sites, none of which are present in the Sandy Creek Tributary A watershed. While
this measure would be most relevant if a future industrial site was constructed in the watershed, the
field staff did notice some dry weather discharges from outfalls in the stream during this study.
Therefore, it is recommended that the City conduct dry weather screening of these outfalls for
potential illicit discharges and identify the discharge sources.
6.3.8 Water Quality Assessment and Monitoring
The City's maintains an extensive water quality and biological monitoring network and uses the
results to detect water quality problems and plan improvements. Monitoring results from station
NH1.7SCTA (Sandy Creek Tributary A at Ivy Creek Blvd) showing low DO levels in the stream were the
impetus behind this special pollutant source tracking project. It is recommended to continue
monitoring at this station to verify that DO and other water quality parameters improve in response
to the implementation of improvement projects.
6.3.9 Total Maximum Daily Load (TMDL) Programs
The City's MS4 permit requires the development of plans to address the City's wasteload allocations
(WLAs) in USEPA-approved TMDLs. Sandy Creek Tributary A is not currently listed as impaired on
North Carolina's draft 2022 303(d) list, and no TMDL is currently planned for this water body.
6-10
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Section 7
References
AECOM. 2020. New Hope and Little Creek Watershed Improvement Plan. Report prepared for the City of Durham.
Ahmed, W., Hughes, B., and Harwood, V.J. 2016. Current Status of Marker Genes of Bacteroides and Related Taxa
for Identifying Sewage Pollution in Environmental Waters. Water 2016 8(6)
Blaszczak, Joanna R., Joseph M. Delesantro, Dean L. Urban, Martin W. Doyle, and Emily S. Bernhardt. 2019a.
Scoured or suffocated: Urban stream ecosystems oscillate between hydrologic and dissolved oxygen extremes.
Limnol. Oceanogr. 64, 2019, p. 877-894
Blaszczak, Joanna R., Joseph M. Delesantrom, Ying Zhong, Dean L. Urban, and Emily S. Bernhardt. 2019b.
Watershed urban development controls on urban streamwater chemistry variability. Biogeochemistry 144, p. 61-
94.
Brown and Caldwell. 2020. Quality Assurance Project Plan for Initial Field Investigations - Sandy Creek Tributary A.
Technical memo submitted to the City of Durham. 22 p.
Brown and Caldwell. 2021. Quality Assurance Project Plan for Follow-up Field Investigations - Sandy Creek Tributary
A. Technical memorandum submitted to the City of Durham. 24 p.
Chowdhury, Sinchan Roy, Jay P. Zarnetske, Mantha S. Phanikumar, Martin A. Briggs, Frederick D. Day -Lewis, and
Kamini Singha. 2020. Formation Criteria for Hyporheic Anoxic Microzones: Assessing Interactions of Hydraulics,
Nutrients, and Biofilms. Water Resources Research 56 (3).
City of Durham. 2017. Water Quality Investigation No. 17WQ105. Summary of 2017 investigation of low DO and
ammonia in Sandy Creek Tributary A. Accessed on 8/31/2020 by J.V. Loperfido.
City of Durham. 2019. Stormwater Management Plan, Permit No. NCS000249.
City of Durham. 2021. Annual Report. NPDES Municipal Stormwater Permit No. NCS000249. July 1, 2020 - June
31, 2021.
City of Durham. 2021. Critical Areas Protection Plan (CAPP), City of Durham Public Works Department.
City of Virginia Beach. 2018. Dry Weather Screening Program Guidance Manual prepared for the City of Virginia
Beach, Virginia Stormwater Management Regulatory Division.
Dreps, C.L. 2011. Water Storm Dynamics and Water Balances of Two Piedmont North Carolina Headwater
Catchments. Master's thesis, North Carolina State University
Feng, S. and McLellan, S.L. 2019. Highly Specific Sewage -Derived Bacteroides Quantitative PCR Assays Target
Sewage -Polluted Waters. Appl Environ Microbiol. 2019 Mar 15; 85(6).
Harvey, Judson W., J. K. B6hlke Mary A. Voytek Durelle Scott and Craig R. Tobias. 2013. Hyporheic zone
denitrification: Controls on effective reaction depth and contribution to whole -stream mass balance. Water
Resources Research 49 (1), p. 6298-6316.
Hegler, Florian; Posth, Nicole R.; Jiang, Jie; Kappler, Andreas (1 November 2008). "Physiology of phototrophic iron(Il)-
oxidizing bacteria: implications for modern and ancient environments". FEMS Microbiology Ecology. 66 (2): 250-
260.
NC DEQ. 2018. NPDES Permit No. NCS000249, City of Durham. October 10, 2018 - October 9, 2023.
NC DEQ. 2009. 15A NCAC 02B .0262 - .0273 ("Jordan Lake Rules"). Effective August 11, 2009.
Stenstrom, M.K., and R.A. Poduska. 1980. The effect of dissolved oxygen concentration on nitrification. Water
Research Volume 14, Issue 6, 1980, Pages 643-649.
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DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A References
U.S. Environmental Protection Agency. 2019. Method 1696: Characterization of Human Fecal Pollution in Water by
HF183/BacR287 TagMan® Quantitative Polymerase Chain Reaction (gPCR) Assay. EPA 821-R-19-002. 56 p.
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Appendix A
Appendix A: Data Catalog
A-1
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Appendix A
Data Catalog
Water Quality Pollutant
Source Tracking
SANDY CREEK TRIBUTARY A
155504 February 25, 2022
Lauren Strader and Clifton Bell
This data catalog provides a tabular summary of available sediment and water quality data, watershed characteristics and environmental
elements obtained from relevant records for Sandy Creek Tributary A. This summary also includes a desktop review of potential
contaminant sources within the watershed, with particular attention to potential sources of oxygen demand. Results of consultation with
the Toxics Release Inventory (fRI) database, industrial permit databases and other public databases are also included, to determine if
known hotspots are or were present in the Sandy CreekTributaryA subwatershed. This information was used to inform sampling locations
and methods in October 2020, and will continue to be used as a resource for interpretation of data from Sandy Creek Tributary A.
A-2
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Waterand Thermal Imaging Study Results
Sediment Quality
Waterand Flow Characteristics and Dissolved
Sediment Quality Oxygen Results
Waterand Dry Weather Screening Water Quality
Sediment Quality Results
Waterand Field Parameter Survey Results
Sediment Quality
Waterand Water Quality Sample Results
Sediment Quality
Waterand Flow Characteristics
Sediment Quality
Waterand"durham_data_SandyCreekTribA.csv"
Sediment Quality
Field sheets/Photo
Brown and
Directory/Spreadsheet
Caldwell
Summary of Results
Field
Brown and
Notes/Spreadsheet of
Caldwell
Results
Field sheets/Lab
Brown and
EDDs/Spreadsheet
Caldwell
Summary of Results
Field sheets/
Spreadsheet Summary
of Results
Lab
EDDs/Spreadsheet
Summary of Results
Field
Notes/ PowerPo i nt
Summary of Results
Comma -delimited file,
Excel Spreadsheet
Brown and
Caldwell
Appendix A
September I Directory of thermal images taken during the September27,
2021
2021 thermal imaging study by Brown and Caldwell. Also
includes a spreadsheet linking photo names to field
observations.
Locations and results of streamflow and dissolved oxygen
September
2021
measurements collected during the September27, 2021
thermal imaging study by Brown and Caldwell.
October
Locations and results of water quality samples collected on
2021
October 20-21, 2021 by Brown and Caldwell during the survey
of the upper drainage area. Includes water quality samples
sent to Pace Analytical for testi ng, MST samples sent to
Microbial Insights forTesting, as well as on -site testing results
measured in the field by Brown and Caldwell staff.
Locations and results of longitudinal field parameters survey
October
2020
performed on October 5, 2020 by Dramby Environmental
Consultants.
Brown and
October
Locations and results of grab samples collected on October 6-
Caldwell
2020
7, 2020 by Brown and Caldwell and Dramby Environmental
Consultants.
Locations and results of streamflow measurements collected
Brown and
October
Caldwell
2020
on October 5, 2020 by Brown and Caldwell.
Water quality data from the City GIS data portal for Sandy
City of Durham,
November
Dept of Public
2020
Creek (station NH1.7SCTA, station NH1.8SCTA). Includes
Works
2009-2020 data for various WQ parameters.
Stormwater &
GIS Services
A-3
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Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Appendix A
Water and
City 2017 City Investigation
pdf report, jpg maps,
City of Durham,
August
Results of special City's 2017 special investigation into low
Sediment Quality
photos, Excel
Dept of Public
2020
DO on Sandy Creek Tributary A. Includes results of longitudinal
workbook
Works
DO survey, ammonia field testing, notes on field observations,
Stormwater &
etc.
GIS Services
GIS Shapefile
City GIS
Admin Boundary
City of Durham,
September
GIS Shapefiles provided by City. Provides locations of the City
Dept of Public
2020
of Durham municipal boundary as well as the boundaries of
Works
the surrounding counties.
Stormwater &
GIS Shapefile
GIS Services
GIS Shapefiles provided by City. Provides information about
City GIS
Environmental
City of Durham,
September
Dept of Public
2020
underlying soil classifications.
Works
Stormwater &
GIS Services
GIS Shapefiles provided by the city. Provides locations of
City GIS
IDDE
GIS Shapefile
City of Durham,
September
Dept of Public
2020
Illicit Discharge Detection and Elimination (IDDE) occurrences.
Works
Stormwater &
GIS Services
GIS shapefiles provided by the city. Provides locations of
City GIS
Impervious
GIS Shapefile
City of Durham,
September
Dept of Public
2020
impervious surfaces.
Works
Stormwater &
GIS Services
GIS shapefiles provided by the city. Provides locations of major
City GIS
Roads
GIS Shapefile
City of Durham,
September
Dept of Public
2020
roads and bridges.
Works
Stormwater &
GIS Services
A-4
Draft Report - Sandy Creek Tributary A.docx

Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
City GIS
Sewer System
GIS Shapefile
City of Durham,
September
Dept of Public
2020
Works
Stormwater &
GIS Services
City GIS
Storm Water
GIS Shapefile
City of Durham,
September
Dept of Public
2020
Works
Stormwater &
GIS Shapefile
GIS Services
September
City GIS
USGS
City of Durham,
Dept of Public
2020
Works
Stormwater &
Petroleum Contaminated Soil
GIS Services
NC State
GIS Shapefile
NC DEQ, Div of
October
Agencies
Remediation Permits
Waste Mgmt
2020
NC State
Hazardous Waste Sites
GIS Shapefile
NC DEQ
October
Agencies
2020
Appendix A
GIS Shapefiles provided by City. Provides locations of sewer
lines and manholes.
GIS Shapefiles provided by City. Provides locations of
stormwater piping, channels and outfalls.
GIS Shapefiles provided by City. Contains locations of nearby
streams and waterbodies from the USGS National Hydrography
Dataset (NHD).
Represents sites that have received a permit or Certificate of
Approval from the NC Underground Storage Tank Section. Data
extracted from the UST Section's Soil Permit database.
https://data-
ncdenr.oDendata.arc>ris.com/datasets/i)etroleu m-
contaminated-soi I-remed i ation-perm its
Represents the locations of sites that are regulated by the
hazardous waste portions of the Resource Conservation and
Recovery Act (RCRA). Includes Large Quantity and Small
Quantity Generators, Transporters of Hazardous Waste,
permitted treatment, storage or disposal (fSD) facilities and
TSD facilities that are under an Order or a Consent Agreement.
Data is extracted from the EPA RCRAInfo database.
https://data-
ncdenr.opendata.arcgis.com/datasets/ hazardous -waste -
sites
A-5
Draft Report - Sandy Creek Tributary A.docx

Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Appendix A
Date o
Data Category
Name
File
Format(s)
Source
Agency
Version
or
Notes
Download
NC State
Inactive Hazardous Sites
GIS Shapefile
NC DEQ
October
Represents hazardous substance spill and disposal sites and
Agencies
2020
includes active and inactive facilities and a variety of property
types. Includes closed remediation sites that have land use
restrictions recorded as part of the remedy. https://data-
ncdenr.opendata.arcgis.com/datasets/inactive-hazardous-
sites-1
NC State
Dry-cleaning Sites
GIS Shapefile
NC DEQ
October
Sites that have been certified into the Dry -Cleaning Solvent
Agencies
2020
Cleanup Act Program (DSCA) Program; sites that are being
investigated by the DSCA Program for dry-cleaning solvent
contamination; sites that have been investigated and
determined not to have been contaminated by dry-cleaning
solvent contamination. https://data-
ncdenr.opendata.arcgis.com/datasets/drycleaning-1
"Google Earth screen shot Feb 1993"
jpg
USGS
Historical USGS topo maps that show the location of the
NC State
September
Agencies
"NC -Durham
2020
former wastewater treatment plant.
South 162432 1951 62500"
"NC Southwest
Durham 163191 1973 24000"
"NC Southwest
Durham 163193 1993 24000"
—r
TRI Mapper
Toxics Release
Online Mapping
USEPATRI
Current
Toxics Release Inventory (TRI) tracks the management of
Inventory
Program
(October
certain toxic chemicals that may pose a threat to human health
2020)
and the environment. https://www.epa.gov/toxics-release-
inventory-tri-program#trisearch
Interpretative "Summary of Existing Stream
Report PDF
City of Durham,
September
Report that summarizes available stream sediment chemistry
Reports Sediment Chemistry Data in Durham
Dept of Public
2020
data from monitoring locations within Durham, Chatham,
County, NC and Surrounding
Works
Granville, Orange, and Wake counties. Includes monitoring
Counties"
Stormwater &
data for Sandy Creek and its tributaries.
GIS Services
A-6
Draft Report - Sandy Creek Tributary A.docx

Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A
Interpretative "Eno River Watershed Report PDF
Reports Implementation Plan Data Collection"
City of Durham, Drafted
Dept of Public October
Works 2014
Appendix A
Reportthat summarizes additional environmental quality data
collected within the Eno River Watershed. The report includes
monitoring data from 3 sites located on the mainstem Eno
River and 4 sites located on its tributaries.
A-7
Draft Report - Sandy Creek Tributary A.docx

Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Appendix C
Appendix B: Field Parameter Survey Results
B-1
Draft Report- Sandy Creek Tributary A.docx

Pollutant Source Tracking and Improvement Opportunities - Sandy Creek Tributary A Appendix C
Table B-1.
Station Name
Field Parameter Results from the October 2020 Stream Survey -Sandy Creek
(downstream to upstream)
Water Temperature Specific Conductance pH DO o DO
Time (/o)
(deg. C) (MS/CM) (mg/L)
Tributary
A
Turbidity
(NTU)
ORP
(MV)
SCT 5
13:49
15.27
0.28
7.12
43
4.17
201
123
SCT 6
14:00
15.33
0.28
7.48
37.2
3.6
201
118
SCT 7
14:13
15.9
0.28
7.6
31.2
3.04
205
106
SCT C1
14:19
15.32
0.11
7.53
0
0
206
325
SCT 8
14:36
15.45
0.28
7.6
37.8
3.17
197
107
SCT 9
14:58
16.06
0.29
7.96
44.4
4.24
195
105
SCT 10
15:05
15.88
0.29
7.92
45.2
4.33
205
103
SCT 11
15:14
15.31
0.29
7.94
21.8
2.12
213
106
SCT 12
15:21
15.41
0.26
8.09
0
0
211
141
SCT 13
15:29
15.45
0.32
8.11
12.8
1.24
212
113
SCT 14
15:33
15.59
0.3
8.09
13.2
1.28
214
111
SCT 15
15:45
15.66
0.31
8.06
2.6
0.25
216
104
SCT 16
15:50
15.75
0.31
8.08
0
0
213
137
SCT 17
15:59
15.5
0.32
8.1
0
0
215
115
SCT 18
16:07
15.82
0.29
8.12
0
0
183
128
SCT 19
16:15
15.74
0.35
8.18
0
0
167
127
SCT 20
16:24
15.94
0.35
8.29
0
0
178
141
SCT 21
16:31
15.79
0.37
8.17
0
0
191
119
SCT 22
16:37
16.26
0.38
8.27
0
0
189
144
SCT 23
16:43
16.14
0.38
8.25
0
0
191
107
SCT 24
16:48
15.96
0.38
8.28
0
0
190
107
SCT 25
16:52
15.65
0.39
8.27
0
0
195
108
SCT 26
16:59
16.22
0.4
8.23
0
0
197
113
SCT 27
17:05
16.33
0.4
8.27
0
0
196
108
SCT 28
17:15
16.74
0.39
8.24
13.2
1.24
184
105
SCT 29
17:25
17.33
0.39
8.32
27.2
2.53
174
122
SCT 30
17:15
17.51
0.39
8.4
15.2
1.41
180
110
SCT 31
17:39
18.01
0.39
8.35
31.4
2.88
182
110
B-2
Draft Report- Sandy Creek Tributary A.docx