Prepared in cooperation with the Virginia Department of Conservation and Recreation,

Fairfax County, and the City of Fairfax, Virginia

A Multiple-Tracer Approach for Identifying

Sewage Sources to an Urban Stream System

Scientific Investigations Report 2006–5317
Cover.  Tributaries to Accotink Creek in Virginia (top left photograph taken by Brian A. Hasty, U.S. Geological Survey; bottom left photograph 

taken by Kenneth E. Hyer, U.S. Geological Survey).
A Multiple-Tracer Approach for Identifying 

Sewage Sources to an Urban Stream System

By Kenneth E. Hyer

Prepared in cooperation with the Virginia Department of Conservation 

and Recreation, Fairfax County, and the City of Fairfax, Virginia

Scientific Investigations Report 2006–5317

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Dirk A. Kempthorne, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation:

Hyer, K.E., 2007, A multiple-tracer approach for identifying sewage sources to an urban stream system: U.S. Geological Survey Scientific Investigations Report 2006–5317, 89 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

The Accotink Creek Study Area ..................................................................................................................2

Multiple-Tracer Approach............................................................................................................................4

Description of the Sewage Tracers ...................................................................................................5

Sampling Site Selection.......................................................................................................................5

Sample Collection and Analysis.........................................................................................................6

Synoptic Sampling Plan.......................................................................................................................7

Additional Sampling..............................................................................................................................7

Optical Brighteners .....................................................................................................................7

Intensive Sampling ......................................................................................................................8

Sampling of Individual Storm-Drain Networks .......................................................................8

Identification of Sewage Sources to Accotink Creek .............................................................................9

Observation of a Sewage Source During Site Reconnaissance ..................................................9

Validation of the Multiple-Tracer Approach for Detecting Sewage in Water..........................10

Selection of Organic Compound Data Indicative of Sewage......................................................11

Synoptic Sampling Results................................................................................................................12

Summary of the Sampling Events ...........................................................................................13

Cases of Major Sewage Inputs ...............................................................................................15

Use of the Tracers for Identifying Minor Sewage Sources................................................17

Selection of the Most Sensitive Tracers for Identifying 

Minor Sewage Sources .....................................................................................17

Qualitative Summary of the Synoptic Sampling Results ............................................19

Quantitative Summary of the Synoptic Sampling Results..........................................22

Additional Sampling............................................................................................................................34

Optical Brightener Monitoring.................................................................................................34

Intensive Stream Sampling Using Automated Samplers ....................................................35

Additional Sampling of Storm-Drain Networks ....................................................................40

Transferability of This Approach......................................................................................................46

Next Steps and Future Directions....................................................................................................46

Summary and Conclusions.........................................................................................................................47

Acknowledgments.......................................................................................................................................47

Literature Cited.............................................................................................................................................48

 Figures

1. Map showing the location of the Accotink Creek watershed study area...........................3

2. Photograph of a short-lived sewage source to an unnamed tributary................................9

3. Map showing locations of sampling sites in the Accotink Creek watershed ..................14

4. Graph showing time series of specific conductance in Accotink Creek 

at the Braddock Road streamgaging station ...................................................................19

5. Map showing locations of 52 sites in the Accotink Creek watershed 

with relative impairment indices that include confirmatory tracer data.....................28
iv

6. Map showing locations of 149 sites in the Accotink Creek watershed 

with relative impairment indices that include only indicator tracer data ...................29

7–10. Graphs showing intensive automated water-quality sampling data collected from:

7. Site T35 ................................................................................................................................36

8. Site S7..................................................................................................................................37

9. Site T51 ................................................................................................................................38

10. Site S8..................................................................................................................................39

11–14. Generalized maps showing the storm-drain network sampling locations for:

11. Site S18................................................................................................................................41

12. Site S20................................................................................................................................43

13. Site S29................................................................................................................................44

14. Site S37................................................................................................................................45

Tables

1. Indicator tracer concentrations associated with the apparent sewage at site S7...........9

2. Indicator tracer concentrations for six raw sewage samples............................................11

3. The subset of 13 organic compounds identified as useful sewage tracers .....................12

4. Summary of the number and type of samples collected during each synoptic 

sampling event ......................................................................................................................13

5. Indicator tracer concentrations in samples collected during and following 

a sewer-line overflow that contributed sewage directly to an unnamed 

tributary ..................................................................................................................................15

6. Wastewater organic-compound concentrations observed at site T13 

in response to an overflowing sewer line ........................................................................16

7. Concentrations of indicator and confirmatory tracer compounds associated 

with sewage at storm-drain site T51BLD..........................................................................17

8. Ratio of median indicator tracer concentrations in six raw sewage samples 

to the median indicator tracer concentrations observed in stream samples 

at site A1.................................................................................................................................18

9. Median indicator tracer concentrations from the synoptic sampling sites .....................20

10. Relative impairment indices for 52 synoptic sampling sites based on indicator 

tracer data and confirmatory organic compound data..................................................22

11. Relative impairment indices for 149 synoptic sampling sites based on indicator 

tracer data only.....................................................................................................................24

12. Median absolute deviation values for the synoptic sampling sites ...................................31

13. Indicator tracer data from the storm-drain network sampling at sites S20, 

S18, S29, and S37 ..................................................................................................................42

Appendixes

1. Indicator tracer data from each synoptic sampling event ..................................................50

2. Confirmatory wastewater organic compound data from each synoptic 

sampling event ......................................................................................................................82

3. Cross-reference listing of study site identifications and official USGS site 

identifications........................................................................................................................86
v

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3

/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Abstract

The presence of human-derived fecal coliform bacteria 

(sewage) in streams and rivers is recognized as a human 

health hazard. The source of these human-derived bacteria, 

however, is often difficult to identify and eliminate, because 

sewage can be delivered to streams through a variety of 

mechanisms, such as leaking sanitary sewers or private 

lateral lines, cross-connected pipes, straight pipes, sewer-line 

overflows, illicit dumping of septic waste, and vagrancy. A 

multiple-tracer study was conducted to identify site-specific 

sources of sewage in Accotink Creek, an urban stream in 

Fairfax County, Virginia, that is listed on the Commonwealth’s 

priority list of impaired streams for violations of the fecal 

coliform bacteria standard. Beyond developing this multipletracer approach for locating sources of sewage inputs to 

Accotink Creek, the second objective of the study was to 

demonstrate how the multiple-tracer approach can be applied 

to other streams affected by sewage sources. The tracers used 

in this study were separated into indicator tracers, which are 

relatively simple and inexpensive to apply, and confirmatory 

tracers, which are relatively difficult and expensive to analyze. 

Indicator tracers include fecal coliform bacteria, surfactants, 

boron, chloride, chloride/bromide ratio, specific conductance, 

dissolved oxygen, turbidity, and water temperature. Confirmatory tracers include 13 organic compounds that are associated 

with human waste, including caffeine, cotinine, triclosan, 

a number of detergent metabolites, several fragrances, and 

several plasticizers. 

To identify sources of sewage to Accotink Creek, a 

detailed investigation of the Accotink Creek main channel, 

tributaries, and flowing storm drains was undertaken from 

2001 to 2004. Sampling was conducted in a series of eight 

synoptic sampling events, each of which began at the most 

downstream site and extended upstream through the watershed 

and into the headwaters of each tributary. Using the synoptic 

sampling approach, 149 sites were sampled at least one time 

for indicator tracers; 52 of these sites also were sampled for 

confirmatory tracers at least one time. Through the analysis 

of multiple-tracer levels in the synoptic samples, three major 

sewage sources to the Accotink Creek stream network were 

identified, and several other minor sewage sources to the 

Accotink Creek system likely deserve additional investigation. 

Near the end of the synoptic sampling activities, three 

additional sampling methods were used to gain better 

understanding of the potential for sewage sources to the 

watershed. These additional sampling methods included 

optical brightener monitoring, intensive stream sampling 

using automated samplers, and additional sampling of several 

storm-drain networks. The samples obtained by these methods 

provided further understanding of possible sewage sources to 

the streams and a better understanding of the variability in the 

tracer concentrations at a given sampling site. Collectively, 

these additional sampling methods were a valuable complement to the synoptic sampling approach that was used for the 

bulk of this study.

The study results provide an approach for local authorities to use in applying a relatively simple and inexpensive 

collection of tracers to locate sewage sources to streams. 

Although this multiple-tracer approach is effective in detecting 

sewage sources to streams, additional research is needed to 

better detect extremely low-volume sewage sources and better 

enable local authorities to identify the specific sources of the 

sewage once it is detected in a stream reach. 

Introduction 

The presence of elevated levels of fecal coliform bacteria 

in surface waters indicates the likely presence of pathogens, 

and poses a health risk to humans who come into contact 

with these waters. Of the approximately 9,900 miles of rivers 

that were included in the Commonwealth of Virginia’s 2004 

305(b) water-quality assessment, roughly 5,000 river miles (or 

about half the river miles assessed) were classified as impaired 

because of elevated levels of bacteria (Virginia Department of 

Environmental Quality, 2004). Cleanup of these contaminated 

waterways and achievement of bacterial water-quality 

standards require considerable information on the sources 

contributing to the problem. Fecal coliform bacteria are found 

in the fecal material of humans, domesticated animals, and 

warm-blooded wildlife. While animals may contribute fecal 

coliform bacteria to a stream, it is likely that the fecal coliform 

A Multiple-Tracer Approach for Identifying Sewage 

Sources to an Urban Stream System

By Kenneth E. Hyer
contributions from humans pose the greater public health 

risk because of the human-specific pathogens that typically 

are found in human sewage. In addition to the public health 

concerns associated with sewage in streams, sewage also 

may contribute substantial amounts of nutrients and organic 

compounds that can result in eutrophication problems and low 

concentrations of dissolved oxygen. 

 In a recent study (Hyer and Moyer, 2003), the patterns 

and sources of bacteria in Accotink Creek (fig. 1) and two 

other watersheds in Virginia were evaluated. The study results 

indicate that a substantial portion of the total fecal coliform 

load passing the U.S. Geological survey (USGS) streamgaging 

station 01654000 on Accotink Creek is contributed by human 

sources, although the exact geographic location and nature of 

the sewage sources are unknown. In the two other watersheds 

that were evaluated as part of the study, similar contributions 

from human sources were observed. In a neighboring urban 

watershed that is similar to Accotink Creek, bacteria-source 

tracking was used to identify humans as a major contributor of 

the fecal coliform bacteria in the stream (Simmons and others, 

2000). Samadpour and Chechowitz (1995) also documented 

substantial human-source contributions of fecal coliform 

bacteria to surface water. Human-source contributions of fecal 

coliform bacteria to surface waters appear to be a relatively 

common problem where humans are present. 

 Identifying specific geographic sources of sewage 

to complex watersheds is a challenging task that generally 

requires a large number of site-specific water samples and the 

application of sensitive environmental tracers. Furthermore, 

environmental tracers must be sufficiently cost effective that 

they can be applied throughout a watershed. Several biological 

and chemical tracers (some of which are relatively inexpensive 

to analyze) are available to identify the sources of sewage. 

These tracers have physical or chemical characteristics that, by 

their presence or magnitude of occurrence, indicate water that 

contains sewage. Ideally, these tracers also have environmental 

fate and transport characteristics that are similar to the fate and 

transport characteristics of sewage. The greatest success in 

identifying sewage sources is likely to occur through the use 

of multiple tracers that provide multiple lines of evidence of 

sewage. Taken together, these multiple environmental tracers 

are capable of providing conclusive evidence and defendable 

results. Other multiple-tracer studies have been applied successfully to identify sources of sewage in both ground water 

(Chen, 1988) and surface water (Juanico and others, 1990); 

however, a systematic approach for identifying sewage sources 

in urban basins is lacking and is needed to help address this 

apparently widespread problem. 

The USGS, in cooperation with Fairfax County, Virginia; 

the City of Fairfax, Virginia; and the Virginia Department of 

Conservation and Recreation (DCR), began an investigation 

in 2001 to identify specific geographic sources of sewage in 

Accotink Creek (fig. 1). The objectives of the investigation 

were to develop and demonstrate a multiple-tracer approach 

for identifying the geographic sources of sewage that have 

been observed in Accotink Creek, a heavily urbanized 

watershed in northern Virginia, and to evaluate the utility of 

each of the tracers for application in other watersheds throughout the Commonwealth. In addition to identifying geographic 

areas of sewage sources, the data collected during this study 

will enable watershed managers to identify areas in the basin 

that have elevated bacterial levels, even if these bacterial levels 

are not caused by sewage sources.

Purpose and Scope

This report documents the development and application 

of a multiple-tracer approach to identify specific geographic 

sources of sewage in Accotink Creek; a similar approach 

could be used in other watersheds to identify sources of 

sewage in streams. Surface-water data were collected from 

149 sites under low-flow conditions during the period 

December 2001 through September 2004. The samples were 

collected under low-flow conditions to characterize relatively 

stable water-quality conditions throughout the watershed and 

concentrated sources of sewage. All samples were analyzed 

for a suite of relatively inexpensive indicator tracers; samples 

from 52 sites also were analyzed for a suite of more expensive 

organic compounds that were used to confirm sewage sources. 

Samples from approximately 60 sites were analyzed for 

optical brighteners; 6 sites were sampled at hourly intervals 

with automated samplers; 4 storm-drain networks were 

sampled in greater detail. Through this multiple-tracer study, 

several sewage sources to the Accotink Creek watershed were 

identified, and several other sites were prioritized for further 

investigation. 

The Accotink Creek Study Area

The Accotink Creek watershed is a heavily urbanized 

watershed (fig. 1). The headwaters of Accotink Creek are 

in the city of Fairfax, Virginia, and the creek flows for 

approximately 10.9 miles (mi) before it drains into Lake 

Accotink in Fairfax County. At least 15 different tributaries 

drain into Accotink Creek between the headwaters and 

Lake Accotink. Additionally, many municipal separate 

storm-sewer systems (MS4s or storm drains) also contribute 

to the streamflow along the main channel and tributaries. The 

portion of the Accotink Creek watershed that was included 

in this study drains an area of 25 square miles (mi2) and 

includes a population of more than 110,000 people (2000 U.S. 

Census Bureau data). Approximately 600 feet (ft) upstream 

from the bridge at Braddock Road in the Accotink Creek 

watershed is a streamgaging station that has been active since 

1949. This station is managed by the Virginia Department 

of Environmental Quality (USGS station number 01654000, 

fig. 1) and was used to define the downstream watershed outlet 

for this study. There are no permitted fecal coliform bacteria 

point-source dischargers within the Accotink Creek watershed 

 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Figure 1. Location of the Accotink Creek watershed study area, Virginia.

The Accotink Creek Study Area 

7720'

Braddock

Road

Accotink

Creek

Accotink

Creek

Crook Branch

Daniels

Run

Little River Turnpike

Pickett Road

Arlington Boulevard

Lee Highway

Fairfax

FAIRFAX CO

495

Long

Branch

Bear

Branch

Hunter

Run

Nutley Street

Chain

Bridge

Road

66

0 1

0 1

2 MILES

2 KILOMETERS

01654000

01654000

EXPLANATION

U.S. Geological Survey streamgaging

station and number

Accotink Creek 

watershed

COASTAL PLAIN

PIEDMONT

BLUE RIDGE

APPALACHIAN

PLATEAU

VALLEY

AND

RIDGE

Figure 1. Location of the Accotink Creek watershed study area, Virginia.

Base from digital files:

Drainage basin from U.S. Geological Survey Open-File Report 2006-1308

U.S. Geological Survey, digital line graph hydrography 1:24,000

County boundaries from TIGER files; 1:100,000; 1994

Virginia State Plane projection, North zone, units feet, NAD 83, central meridian 7830’W

3852'

7718'

7716'

7714'

3854'

7712'

3850'
(J. Crowther, Virginia Department of Environmental Quality, 

written commun., 1999).

Although portions of the watershed are forested (especially adjacent to the stream), urban and residential land uses 

dominate the majority of the watershed and provide opportunities for many different potential sources of feces to the stream. 

Potential sources of fecal coliform bacteria in the watershed 

include domestic pets, such as dogs and cats; wildlife, such as 

raccoons, opossum, rats, squirrels, and deer; waterfowl, such 

as geese, ducks, and sea gulls; and humans, potentially from 

cross-connected pipes, leaking or overflowing sewer lines, and 

failing septic systems. In this study an attempt was made to 

develop an approach for identifying human sources of sewage 

from other sources in the watershed.

The Accotink Creek watershed lies in the Piedmont Physiographic Province of Virginia and is underlain by crystalline 

igneous and metamorphic rocks (Froelich and Zenone, 1985). 

The geology of the watershed is composed of five formations. 

The Wissahickon Formation dominates the watershed and 

is composed of quartz-mica schist, phyllite, and quartzite 

(Johnston, 1964). The Greenstone Contact Complex is present 

in some headwater areas of the catchment and is composed of 

chlorite schist, sericite-chlorite schist, chlorite-quartz schist, 

talc schist, and small amounts of quartzite (Johnston, 1962). 

Granitic rocks are distributed throughout the watershed; these 

rocks are of variable composition, including biotite granite, 

muscovite granite, biotite-muscovite granite, granodiorite, 

quartz monzonite, and quartz diorite (Johnston, 1964). A 

small portion of the watershed is underlain by the Sykesville 

Formation, which includes muscovite or sericite-biotite-quartz 

schist and gneiss, quartzite, epidote quartzite, and muscovitebiotite quartzite (Johnston, 1964). Alluvial material (composed 

of clay and sand, as well as quartz cobbles and pebbles) also 

is present along the channel and in the flood plain of Accotink 

Creek (Johnston, 1962). 

The soils of the Accotink Creek watershed are present as 

three distinct soil associations, described by Porter and others 

(1963). The Glenelg-Elioak-Manor association has developed 

from the weathering of the crystalline bedrock of the 

Piedmont. These well-drained and, in some places, excessively 

well-drained silt-loam soils dominate the watershed. The 

Fairfax-Beltsville-Glenelg association composes a relatively 

small portion of the watershed (limited to the headwater areas) 

and is formed from the residuum of piedmont bedrock and 

fluvial coastal plain sediments. These soils are present as silt 

or sand loams and range from somewhat poorly drained to 

well drained. The Chewacla-Wehadkee association occurs 

only on a limited basis within the watershed, generally in the 

bottomland and flood plains along the streams. These silt-loam 

soils range from moderately well drained to poorly drained 

and have developed from alluvial material that was washed 

from the piedmont uplands. 

 To investigate the potential sources of sewage in 

Accotink Creek, it is important to understand the different 

possible sewage sources and the different elements of sewage 

management in the watershed. Most (more than 95 percent) 

of the sewage that is generated in the watershed is transported 

by an extensive sewer-line network that underlies nearly the 

entire basin. Both Fairfax County and the City of Fairfax have 

sewer-line maintenance and inspection plans that include 

routine investigation of lines and replacement of older lines to 

prevent sewage leaks and other problems (U.S. Environmental 

Protection Agency, undated; City of Fairfax, undated). There 

are no combined storm-sewer and sanitary sewer lines in the 

basin. Approximately 900 homes in the watershed are served 

by septic systems rather than the sewer system. Inspections of 

these septic systems are made by the Fairfax County Health 

Department when new septic systems are installed and when 

permitted repairs are made to septic systems already in use. 

Fairfax County resources, however, prevent routine inspection 

of septic systems throughout the watershed (Fairfax County 

Department of Health, 2004). In addition, an important consideration in the sewage management within the watershed is that 

of lateral lines, which connect individual homes or businesses 

to sewer lines maintained by the city and county. All lateral 

lines are privately owned by the respective property owners 

whom they serve, and their maintenance is the responsibility 

of these property owners. Maintenance of lateral lines, 

however, typically is performed only when a problem occurs, 

such as a blockage or overflow. Minor leaks from lateral lines 

may never be noticed or identified by a homeowner; however, 

such leaks and failing lateral lines may be a potentially 

important source of sewage to Accotink Creek. Failure of any 

of the sewage-management elements in the watershed increase 

the likelihood of sewage in Accotink Creek. Other possible 

sources of sewage in Accotink Creek include sewer-line 

overflows and illicit dumping by septic-waste haulers. Both 

of these events are considered relatively rare in the basin; 

however, illicit septic-waste dumping has been reported, and 

between June 2001 and November 2002, two documented 

sewer-line overflows occurred in the Accotink Creek watershed area that was included as part of this study (Tom Russell, 

Fairfax County Public Works and Environmental Services, 

written commun., November 2002). 

Multiple-Tracer Approach

A broad selection of chemical and biological tracers were 

used during this investigation along with detailed sampling 

of the Accotink Creek stream network (the main channel, 

tributaries, and storm drains) to evaluate sources of sewage in 

the stream. All of the tracers used during this study have been 

applied individually elsewhere with some success in indicating 

sewage sources, but in no single previous study have all of the 

tracers been applied nor have direct comparisons of all these 

tracers been made. This multiple-tracer approach provides 

multiple lines of evidence with which to identify geographic 

sources of sewage. Each of the tracers likely has its own 

advantages and drawbacks, depending on project objectives, 

budget, and environmental setting. The detailed sampling 

 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
conducted during this investigation throughout the watershed 

allowed for the collection of extremely detailed information on 

the basin. Through this study, the effectiveness of the multiple 

tracers was evaluated, and an approach for investigating 

sources of sewage in any watershed was identified. 

Description of the Sewage Tracers

During field activities, close attention was paid to the 

occurrence of visual clues that indicated potential contamination. These visual clues included overflowing sewers, strongly 

discolored waters, and the presence of typical human-waste 

products (toilet paper, feces, and hygiene products) in the 

stream. The presence and frequency of distinctive odors were 

noted as encountered.

Water-quality characteristics and physical properties, 

such as specific conductance, temperature, turbidity, 

dissolved-oxygen concentrations, surfactants, optical brighteners, and fecal coliform bacteria, have all been used as tracers 

to determine the presence of sewage in streams. Concentrations of fecal coliform bacteria were used as the primary 

bacterial tracer for this study because they were being used by 

the Commonwealth of Virginia as the bacterial standard when 

the study was initiated. Water temperature measurements can 

be useful in identifying point sources of relatively cooler or 

warmer water into a stream, although the use of temperature as 

a tracer is likely limited to only the most major of temperature 

differences. The degradation of organic sewage material by 

in-stream biota consumes oxygen and can result in decreased 

dissolved-oxygen concentrations. The direct discharge of sewage into a stream can cause elevated turbidity levels, although 

the particulate material causing the elevated turbidity can 

settle out rapidly. Sewage has an ionic strength that usually is 

far greater than that of the natural environment; therefore, the 

presence of sewage in a stream increases the overall specific 

conductance of the water (Chen, 1988). Surfactants, which 

provide the cleaning action of detergents, are common in 

sewage; the presence of surfactants in stream water at elevated 

concentrations may indicate contamination by sewage (Brunner and others, 1988). Optical brighteners (present in virtually 

all laundry detergents) provide information on water samples 

that contain domestic wastewater from laundry activities and, 

therefore, also likely contain sewage (Aley, 1985).

 Specific ions and trace elements can be used as 

indicators of sewage. Chloride and bromide appear to be 

reliable tracers of sewage. Sewage contains elevated levels 

of chloride relative to both finished drinking water and the 

natural environment; thus, the presence of elevated chloride 

concentrations can indicate the presence of sewage (Chen, 

1988). Bromide data frequently are coupled with chloride data, 

because the ratio of the chloride concentration to the bromide 

concentration (Cl/Br ratio) is a good indicator of sewage 

(Thomas, 2000). Bromide concentrations in sewage are not 

elevated relative to those in the natural environment, so sewage 

that enters a stream should cause an increase in the 

Cl/Br ratio. Boron can be an effective tracer of sewage sources 

because natural stream-water concentrations are relatively low. 

Boron is used primarily in cleaning powders, which eventually 

are flushed into sewage lines. Stream samples with elevated 

concentrations of boron generally indicate contributions of 

sewage (Neal and others, 1998).

 Two additional approaches to the tracing of sewage 

were considered at the onset of this study—bacterial-source 

tracking and analyses of organic compounds (Zaugg and 

others, 2002) that frequently are associated with sewage (such 

as caffeine, coprostanol, cholesterol, nicotine metabolites, 

several detergent metabolites, and human pharmaceuticals). 

Both approaches already have been used in Accotink Creek 

as well as other watersheds in Virginia, and both appear to 

be reliable in their ability to accurately identify the presence 

of human-derived fecal coliform bacteria (Hyer and Moyer, 

2003). Although both approaches appear reliable, both are 

expensive to apply. Consequently, these approaches were used 

in this study only to confirm the results of the less expensive, 

more accessible tracers, which are termed indicator tracers.

On the basis of all the tracers being considered, the 

presence of relatively high specific conductance, chloride, 

boron, chloride/bromide ratio, surfactants, and fecal coliform 

bacteria, along with relatively low dissolved-oxygen concentrations provide strong evidence of sewage contamination. 

Water samples showing this collection of positive tracers then 

were evaluated for the presence of organic wastewater tracers 

or submitted for bacterial-source tracking analysis, both of 

which served to directly confirm the presence of sewage.

Sampling Site Selection

This study was designed to provide a detailed understanding of the water-quality conditions and sewage sources 

throughout the Accotink Creek watershed which lies upstream 

from Braddock Road (fig. 1). Accordingly, the sampling plan 

was developed to sample along the entire main channel of 

Accotink Creek, the tributaries to the creek, and all flowing 

storm drains. To develop the list of sampling sites, a detailed 

watershed reconnaissance was conducted to understand the 

flow conditions. As part of this reconnaissance, the headwaters 

of the major tributaries were located, and all storm-drain 

outfalls in the basin were visited at least once to determine 

whether the drain had flow under base-flow conditions. 

Through this reconnaissance, 410 storm drains were visited, 

and approximately 50 were observed to have flow under 

base-flow conditions. Therefore, all 50 of the storm drains 

with flow under these conditions were selected as sampling 

sites. Observance of approximately 10 percent of the storm 

drains to be flowing under base-flow conditions was consistent 

with the data that were collected previously by Fairfax County 

(Russell Smith, Fairfax County Department of Public Works, 

oral commun., 2000). Because several tributaries have been reengineered and buried underground, several of the storm-drain 

outfalls were actually the resurfacing of buried tributaries, 

Multiple-Tracer Approach 
and these sites could have been classified as either tributaries 

or storm drains. For consistency, samples that were collected 

from the end of a storm-drain outfall generally were classified 

as storm-drain samples. 

 After identifying storm drains with flow and the upper 

limits of the major tributaries, the sampling plan for the main 

channel of Accotink Creek and the tributaries was developed. 

Initially, sites were selected to include the main channel of 

Accotink Creek just upstream from each inflowing tributary. 

Each inflowing tributary was sampled just before it drained 

into Accotink Creek. Additional sampling sites were selected 

on the main channel, if the distance between inflowing tributaries was greater than 0.5 mi. Using this sampling scheme, 

16 sites were identified on the main channel of Accotink 

Creek. In addition to sampling each tributary just before it 

flowed into the main channel of Accotink Creek, at least two 

additional samples were collected from each major tributary, 

with the sampling locations dependent on the presence of 

storm drains with flow, branches in tributaries, and the overall 

tributary length. Based on this selection process, 55 tributary 

sampling sites were identified. Combining the 50 storm-drain 

sampling sites with the 16 main channel sites and the 55 tributary sampling sites yielded a total of 121 sampling sites 

initially selected for detailed water-quality sampling. These 

121 sites are termed synoptic sampling sites in this report. 

Sample Collection and Analysis 

At each synoptic sampling site, the physical properties 

of water temperature, specific conductance, pH, and dissolved oxygen were measured using hand-held water-quality 

monitors. These monitors were calibrated according to the 

manufacturer’s specifications each morning that they were 

used. Clean, sterile glass bottles were used to collect samples 

for surfactant, turbidity, and fecal coliform bacteria analyses. 

Acid-rinsed polyethylene bottles were used to collect samples 

for chloride, boron, and bromide analyses. Surfactants were 

determined within 6 hours of collection and were measured 

by using a colorimetric detergents kit (for determining 

anionic detergents), using a methylene blue active substances 

analysis (EPA Method 425.1). Turbidity was determined 

in the field using a Hach 2100 turbidimeter. Fecal coliform 

bacteria were determined by membrane filtration, following 

standard USGS protocols for bacteria (U.S. Geological survey, 

variously dated). The aliquots for analysis of chloride, boron, 

and bromide were kept chilled and delivered, usually within 

24 hours of collection, to the Fairfax Environmental Services 

Laboratory where they were analyzed using standard methods 

approved by the U.S. Environmental Protection Agency 

(USEPA). For all analyses, a minimum of 10 percent of the 

samples were analyzed as blind duplicates or split samples; 

the split samples were analyzed at the USGS National Water 

Quality Laboratory in Denver, Colorado. Results of the blind 

duplicates and split samples were used to ensure that dataquality objectives were being met. 

Because many of the storm drains and tributary sites 

were extremely shallow (flow less than 0.2-ft deep), sampling 

protocols had to be modified to collect a representative water 

sample from these locations. Whenever possible, a grab 

sample was collected from the approximate center of flow in 

what appeared to be a well mixed region. When flow was too 

low to permit a grab sample, clean, sterile, disposable syringes 

were used to collect a sample of the flowing water. Using the 

syringe for sampling allowed the collection of samples from 

sites with extremely low flow, while preventing the collection 

of bottom sediments. 

Following sample collection, flow measurements were 

made at all sites. When possible (usually only in the main 

channel and some of the major tributaries), streamflow 

measurements were made following standard USGS protocols 

(Rantz and others, 1982). When water depths and velocities were insufficient to permit the use of standard USGS 

streamgaging equipment and protocols, various other flowmeasurement techniques were used. In most cases, the stream 

channel was modified to create uniform flow conditions, 

allowed to stabilize, and then flow was determined by measuring both the stream area and velocity. Discharge is calculated 

as the product of stream velocity and area through which flow 

occurs. Stream velocity was determined by timing how long 

it took for a floating (or neutrally buoyant) marker (typically 

a leaf or small piece of tissue paper) to move a specified 

distance (usually 1–3 ft). Multiple time measurements 

typically were made and used to calculate mean velocity. The 

stream area was determined by making multiple width and 

depth measurements in the modified channel to determine 

the mean width and depth of the channel. Occasionally, site 

conditions enabled the direct collection of a known volume of 

water over a timed period, and discharge could be calculated 

directly. This condition was encountered primarily at storm 

drains where there was a drop between the storm-drain outfall 

and the receiving stream.

When wastewater organic compound confirmatory 

analysis was needed, samples were collected using 1-liter (L) 

baked amber glass bottles. The samples were kept chilled and 

sent by overnight courier to the USGS National Water Quality 

Laboratory, where the samples were processed according to 

the standard analytical methodology (Zaugg and others, 2002). 

Because the wastewater organic compound analysis was 

developed to analyze for endocrine-disrupting compounds, 

not all of the 46 compounds that are part of the analysis are 

indicative of sewage. A subset of 13 compounds that are 

specific to sewage was developed on the basis of sewage 

samples that were analyzed as a part of this and other studies; 

the methodology and data used for the selection of the 13 

subset compounds are presented in the results section. One 

unique element of this organic compound analysis is that the 

detection method used in the analysis is an “information rich” 

method; that is, the presence of a specific compound can be 

verified at concentrations that are below the defined minimum 

reporting level (Steve Zaugg, U.S. Geological Survey, oral 

commun., 2000). When the presence of a compound is verified 

 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
and the concentration is below the minimum reporting level 

(which actually represents a level of quantification), the 

reported concentration of the compound is noted with an “E” 

for estimated. 

Initially, the plan was to use the fecal coliform plates 

from the membrane filtration analysis for subsequent bacterialsource tracking (BST) analyses; however, the BST component 

of the study was eliminated for several reasons. First, the 

laboratory selected to perform the BST analyses had extreme 

difficulty providing data within a reasonable timeframe (prior 

to the next synoptic sampling). Secondly, further evaluation of 

the confirmatory tracers seemed to indicate that the wastewater 

organic compound analyses were more powerful than the BST 

analyses. The wastewater organic compound analysis is a 

whole-sample extraction, while the BST analysis is performed 

on a subset of the bacteria and typically accounts for less than 

1 percent of the total bacteria that are present in the sample. 

Thirdly, BST studies recently have come under sharp criticism 

by several methods-comparison studies (Stewart and others, 

2003; Stoeckel and others, 2004) that demonstrated the need 

for more extensive quality assurance and quality control 

(QA/QC) before BST results can be interpreted accurately. 

For all these reasons, BST was not performed as a part of 

this study; instead, additional wastewater organic compound 

analyses were performed. 

Synoptic Sampling Plan

To identify the sources that contribute sewage to 

Accotink Creek, a synoptic sampling approach was developed 

to intensively sample the entire watershed, including the storm 

drains, tributaries, and the main channel of Accotink Creek. 

Because sewage sources to the stream were assumed to be 

relatively constant in time, synoptic sampling was scheduled 

to be performed only during low-flow periods (when the 

effects of sewage dilution by the resident stream water were 

minimized). Eight sampling events were conducted, and 

each event required 4 to 5 days of field work to sample all 

the sites and collect all of the necessary data. To ensure that 

the sampling represented low-flow conditions, no sampling 

was performed within 48 hours of a precipitation event, and 

data from the Braddock Road streamgaging station were used 

to ensure that the sampling was performed during relatively 

steady-flow conditions. Because of these conditions, the 

synoptic sampling could be performed only during periods 

of at least 7 days of clear, dry weather. Obtaining these 

conditions proved to be much more difficult than initially 

anticipated and resulted in numerous project delays, especially 

during the relatively wet 2002 and 2003 water years1.

Eight synoptic sampling events were planned to provide 

sufficient data to document the water-quality conditions and 

to identify the potential sewage sources within the watershed. 

The eight sampling events were tiered such that the first four 

events were used to characterize the water quality throughout 

the basin and identify specific areas of potential sewage 

sources; the last four sampling events were used to more 

intensively sample and describe the specific locations where 

sewage sources were detected. Initially, the synoptic sampling 

was to occur on a quarterly basis; however, delays caused by 

weather and laboratory delays resulted in periods longer than 3 

months between some synoptic sampling events. 

As designed, 121 samples were collected during each 

of the first four sampling events, and each synoptic site was 

visited during each of these sampling events. In an effort 

to develop a consistent characterization of the Accotink 

Creek watershed before investing in expensive confirmatory 

analyses, no wastewater organic compound samples were 

collected during the first or second sampling events. Collection of wastewater organic compounds was initiated during 

the third sampling event and was conducted only at sites 

where tracer concentrations indicated the possible presence of 

sewage. Changes in the locations of the monitoring sites (but 

not the total number of sampling sites) were made after the 

first four sampling events were completed and the data were 

analyzed. Sampling sites that were similar to neighboring sites 

and sites that showed no indication of sewage contamination 

were eliminated. Additional sites were added for the last four 

sampling events to more intensively sample and describe the 

areas where sewage sources were indicated. New sites were 

selected based on the results of the earlier samplings and the 

associated watershed characteristics, such as different methods 

of sewage disposal, sewer systems compared to septic systems, 

sewer line crossings, and such. 

Additional Sampling

In addition to the methodology previously described 

for the collection of synoptic samples, several other types of 

samples were collected to understand further the potential 

sewage sources in the Accotink Creek watershed and the 

variability that was observed in the synoptic samples. All of 

the additional samples were collected as part of the eighth 

synoptic sampling event, and the methods associated with the 

sampling are described below.

Optical Brighteners

As reported in numerous other publications, optical 

brightener monitoring may offer an informative tool for 

identifying wastewater inputs to streams (Aley, 1985; Cinotto, 

2005). Optical brighteners are added to nearly all laundry 

detergents to make white fabrics appear whiter and brightly 

colored fabrics appear brighter. They are useful environmental 

tracers because they generally are well associated with sewage 

and are relatively recalcitrant in the natural environment. Near 

the end of this study, optical brighteners were monitored at 

many of the synoptic sampling sites that had either highly 

Multiple-Tracer Approach 

1

Water year is the period October 1 to September 30 and is defined by the 

year in which the period ends.
variable tracer concentrations or concentration levels that 

seemed to be indicative of sewage. The added benefit of 

optical brightener monitors is that they provide time-integrated 

sampling—something that grab sampling cannot achieve.

The optical brightener monitors were constructed using 

the methodology developed for use at the Ozark Underground 

Laboratory (Aley, 1985). The sampler consisted of a 5-inch 

square piece of unbleached cotton attached with a rubber 

band over the mouth of a 2-inch diameter, 6-inch long section 

of polyvinyl chloride (PVC) pipe. The sampler was placed 

in the stream and affixed in place horizontally using either 

aluminum wire or nylon mason’s line in a manner that allowed 

the streamflow to pass through the length of PVC pipe. When 

possible, the samplers were deployed in shaded locations at 

each site to minimize the effects of photodegradation of the 

optical brighteners. The samplers were deployed at numerous 

Accotink Creek sampling sites during a period of anticipated 

base-flow conditions and left in place for approximately 

3 days. 

Upon retrieval, the monitors were placed in labeled 

whirl-pak bags, placed on ice, and returned to the Virginia 

Water Science Center water-quality laboratory for analysis. In 

the laboratory, the cotton swatches were individually rinsed 

with tap water for several minutes to remove any sediment 

material that was present. This rinsing removed much of the 

sediment material without causing desorption of any optical 

brighteners (Tom Aley, Ozark Underground Laboratory, oral 

commun., February 3, 2004). After rinsing, the still-damp 

cotton swatches were evaluated in a dark room, using a 

long-wave ultraviolet (UV) light. Results of the readings were 

enhanced by using several optical brightener standards that 

were prepared using deionized water and a liquid detergent 

that contained optical brighteners. The following standards 

were used along with the fluorescence response that was 

observed:

Deionized water (negative control) Negative

1:10,000 Negative

1:5,000 Ambiguous

1:1,000 Positive

1:100 Positive

1:10 Positive

Pure detergent Positive

The sample readings were recorded categorically as being 

positive, negative, or ambiguous for optical brighteners. After 

the readings were completed, they were independently verified 

by two other analysts. 

•

•

•

•

•

•

•

Intensive Sampling

Intensive sampling of several synoptic sampling sites was 

performed to document the possible water-quality variability 

at some of the sites. These intensive samples were collected at 

hourly intervals over roughly a 24-hour period and provided 

much more detailed information than the grab samples. 

Therefore, these samples were useful in understanding the 

variability in some of the synoptic-sample data. 

During the eighth synoptic sampling event, automated 

samplers (autosamplers) were deployed at several potentially 

impaired sites in an attempt to document the variability in 

the stream-water composition. At each sampling site, the 

autosampler was programmed to draw a sample every hour, on 

the hour. The autosampler then was left in place and allowed 

to operate for nearly 24 hours before being moved to the next 

site.

The samples from the auto-samplers were analyzed in 

the field for surfactants, turbidity, and specific conductance. 

Bacteria could not be analyzed because the holding time was 

beyond the 6-hour limit. After analysis for surfactants, turbidity, and specific conductance, the samples were transported to 

the laboratory to be analyzed for chloride, boron, and bromide. 

The patterns in these tracers over the 24-hour period were 

evaluated and interpreted.

Prior to deploying each autosampler, all tubing and 

sample bottles were cleaned using 5-percent hydrochloric acid 

and rinsed with deionized water until the tubing was clean 

(when the final rinse water passing through the tubing and 

bottles had a specific conductance of approximately 1 microsiemen per centimeter (μS/cm). After being used at one 

synoptic sampling site, the tubing and bottles of each autosampler were rinsed with copious amounts of deionized water 

prior to reuse at another site. Bottle and tubing blanks were 

collected both before the autosamplers were first deployed and 

after each field cleaning to ensure that the cleaning procedures 

were adequate. 

Sampling of Individual Storm-Drain Networks 

After the sixth sampling event, several “priority” storm 

drains were identified as having elevated bacterial concentrations and(or) possible sewage sources. The Fairfax County 

Stormwater Management Division initiated a visual inspection 

of several of these priority storm drains, but the potential 

source of the elevated tracers could not be determined. Additional detailed sampling was conducted at four of the priority 

storm-drain sites in an attempt to better understand the sources 

of water in these storm-drain networks and to see if the source 

of the elevated-tracer concentrations could be located. 

The storm-drain network sampling associated with an 

individual storm-drain outfall was accomplished by first 

performing an investigation of the entire storm-drain network 

to identify the branches that were flowing and the relative 

discharge in each branch of the network. Using Fairfax County 

tax maps that also contained the storm-drain networks, this 

 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
investigation was accomplished by starting at the downstream 

end of the network and moving in an upstream direction. 

This investigation allowed the development of an overall 

understanding of each network.

On the basis of the initial investigation of the relative 

flow conditions, several within-network sampling sites 

were selected to segregate the storm-drain network into 

different components. For each storm-drain outfall that was 

investigated, between three and eight samples were collected 

from throughout the storm-drain network. During sampling, 

as many of the indicator tracers as possible were collected, 

but some characteristics could not be determined because 

of the site conditions (commonly, dissolved oxygen, water 

temperature, and flow). Site access proved to be a challenge, 

as many of the storm sewer-lines could not be easily accessed 

from the land surface. The challenges of site access cannot 

be overlooked in studies that include sampling of storm-drain 

networks. 

Identification of Sewage Sources to 

Accotink Creek

Below are the results from the sampling activities. 

Included are validations of this multiple-tracer approach and 

identification of the confirmatory organic compounds, as well 

as a presentation of the sampling results and a description of 

how these multiple tracers can be used for the identification of 

sewage sources to streams.

Observation of a Sewage Source During Site 

Reconnaissance

During the detailed reconnaissance, a condition was 

encountered that appeared to be a short-lived sewage 

source to an Accotink Creek tributary; this situation offered 

an early opportunity to evaluate the field application of 

several of the sewage tracers. This sewage source was 

discovered because the tributary in question was divided 

between two different tax maps which caused reconnaissance of the storm-drain outfalls on the south side of the 

tributary to occur on day 1 and reconnaissance of the storm 

drains on the north side of the tributary to be completed 

on day 2. During the day-1 reconnaissance, the flow in the 

tributary and the drains on the south side of the tributary 

were all clear and appeared to be typical of an urban 

stream. On day 2 of the reconnaissance, the flow in the 

tributary was dark gray and appeared to be sewage (fig. 2). 

Prior to arriving on the banks of the tributary on day 2, an 

extremely strong sewage odor was noticed all around the 

tributary (sufficiently strong that the field team began to 

search for the sewage source before reaching the tributary). 

The source of the gray water was traced upstream to a 

storm-drain outfall that functioned as the headwaters for the 

tributary. 

While investigating the source of this gray water in 

the tributary, it was determined that the flow in the outfall 

containing the gray water was decreasing steadily. For this 

reason, the search for the source of the water was halted, and 

water samples were collected to characterize the gray water. 

For comparison purposes, a sample also was collected from 

a nearby flowing storm-drain outfall on the south side of the 

tributary that visually was clear (even though nothing more 

was known about the water quality of this visually clear site). 

Because the study was only in the reconnaissance phase and 

sampling had not been anticipated, not all tracers could be 

determined for these samples. The storm-drain outfall with 

the gray water was labeled site S7, and the clear-flowing 

storm-drain site was labeled site S8. These site identifiers were 

retained for the remainder of the study. The tracer concentrations for these two samples are presented in table 1. 

Table 1. Indicator tracer concentrations at sites S7 and 

S8 associated with the apparent sewage at site S7 that 

was discovered during watershed reconnaissance and site 

selection in the Accotink Creek watershed, Virginia.

[mg/L, milligrams per liter; >, greater than; NTU, nephelometric turbidity 

units; mS/cm, microsiemens per centimeter; col/100 mL, colonies per 

100 milliliters] 

Indicator tracer Site S7

(fig. 3)

Site S8

(fig. 3)

Surfactants (mg/L) >3 0.25

Turbidity (NTU) 224 1

Specific conductance (mS/cm) 413 326

Dissolved oxygen (mg/L) 5.1 7

Fecal coliform bacteria (col/100 mL) 13,300 26,300

Figure 2. A short-lived sewage source to an unnamed tributary 

(site S7) to Accotink Creek, Virginia, September 28, 2001.

Identification of Sewage Sources to Accotink Creek 

Figure 2. Photograph of a short-lived sewage source to an unnamed tributary (site S7) to Accotink Creek, Virginia,

September 28, 2001.
The results from these samples demonstrate sharp differences in some sewage tracer concentrations and only minor 

differences in others. As anticipated, the gray-water site (S7) 

had substantially elevated levels of surfactants and turbidity 

relative to site S8 (table 1). Specific conductance was only 

slightly greater at site S7 than at site S8. Dissolved-oxygen 

(DO) levels were relatively low at both sites, but the DO 

concentration at site S7 was approaching the State ambient 

water-quality standard of 4.0 milligrams per liter (mg/L). 

Site S8 had elevated fecal coliform bacteria levels compared 

with those at site S7, but both sites had levels that were well in 

excess of the statewide instantaneous fecal coliform bacteria 

standard (1,000 colonies per 100 milliliters (col/100 mL)). 

These observed fecal coliform bacteria and DO concentrations 

indicate that site S8 may also have water-quality problems. 

Site S7 was revisited approximately 4 days later, and the 

turbid conditions had abated; site S7 was resampled for fecal 

coliform bacteria only, and the concentration had decreased to 

1,700 col/100 mL (still somewhat elevated, but substantially 

reduced relative to the gray-water conditions). Although 

the source of this gray water was never specifically located 

(because conditions were already abating when the situation 

was discovered), the elevated surfactants, turbidity, fecal 

coliform bacteria, and specific conductance (as well as the 

decreased DO) indicate that the gray water was likely a shortlived sewage source to this unnamed tributary to Accotink 

Creek. Possible sources of this sewage include illegal septictank truck dumping, which has been documented, or some 

type of a short-lived release from a septic system, sewer line, 

or lateral line. Although detailed information regarding sites 

S7 and S8 was unavailable at the time of this initial sampling, 

the results of further data collection during this study indicate 

that both sites may contribute sewage to Accotink Creek. 

These data will be presented later in the report. 

Validation of the Multiple-Tracer Approach for 

Detecting Sewage in Water

Useful sewage tracers have physical or chemical characteristics that, by their presence or magnitude of occurrence, 

indicate the presence of sewage in water. Ideally, these tracers 

also have environmental fate and transport characteristics 

that are similar to the fate and transport of sewage. Because 

no single sewage tracer available is likely to perfectly satisfy 

these criteria, the greatest success in identifying sewage 

sources is likely to occur through the use of multiple-tracer 

compounds that, taken collectively, can provide a “weight-ofevidence” approach for identifying waters that contain sewage. 

Although the potential tracer candidates, as presented in the 

methods section of this report, were identified, the applied 

value of these tracers for this study was evaluated. 

One way of theoretically evaluating the potential use of 

a particular tracer is to evaluate the background level of the 

tracer in the natural environment and compare the background 

level to the level of the tracer found in untreated sewage. 

Based on this comparison, useful sewage tracers have widely 

different tracer concentrations in these two environments.

To demonstrate this comparison, six untreated sewage 

samples were collected from different locations in Fairfax 

County and Fairfax City. Three sewage samples were collected 

by removing sewer-line manhole covers in the Accotink 

Creek watershed and grab sampling the flow in the sewer 

line. These three grab samples were identified as SS1–SS3. 

Two additional sewage samples were collected from the two 

main-sewer trunk lines that drain into the sewage-treatment 

plant that serves Fairfax County (the Noman M. Cole Pollution Control Plant). One trunk line drains directly from the 

Accotink Creek area (labeled NPC1), and the other drains 

sewage from a neighboring basin (NPC2). The sixth sewage 

sample was collected from a septic-tank truck as it arrived at 

the sewage-treatment plant (NCP4). This particular septic-tank 

truck contained sewage pumped from a single septic tank that 

served a 16-family development in Fairfax County. For comparison, the analytical results of indicator tracer concentrations 

in these sewage samples and the median tracer concentrations 

that were observed at USGS streamgaging station 01654000 

(fig. 1) at Braddock Road (site A1) are given in table 2.

These data demonstrate substantial differences between 

the tracer concentrations in sewage and those detected in 

the environmental samples from Accotink Creek (site A1). 

These substantial differences support the use of these tracers 

for detecting sewage inputs to Accotink Creek, and the data 

also establish relative upper limits that can be expected for 

each tracer in water that contains sewage. The difference in 

concentrations of several of the tracers is an order of magnitude or greater in the sewage samples than in the background 

stream sample, which indicates that stream samples containing 

sewage should be readily distinguishable from the background 

water-quality conditions. 

10 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Selection of Organic Compound Data Indicative 

of Sewage

As described in the methods section, not all of the 46 

wastewater organic compounds typically analyzed are strongly 

associated with sewage. Many are included in the analysis 

because they are suspected endocrine disrupters. To develop a 

set of compounds that are strongly associated with sewage, the 

untreated sewage samples from sites NCP1 and NCP4 were 

submitted to the USGS National Water Quality Laboratory 

for organic compound analysis. About the same time as these 

sewage samples were being analyzed at the laboratory, sewage 

data from the Wilkison and others (2002) study became available. In this study, at least 58 untreated sewage samples were 

collected from various sewage-treatment plants at different 

times. To improve the understanding of which compounds 

likely are associated with sewage, the data from Wilkison and 

others (2002) were considered in the development of a data 

subset of sewage-indicative organic compounds. The criteria 

used to determine the subset of organic compounds that are 

strongly associated with sewage are as follows:

The data from Wilkison and others (2002) were summarized to identify the compounds that were present in a 

high percentage of the sewage samples collected. To be 

considered, a compound must have been detected in at 

least 75 percent of the samples. 

Working only with the subset of compounds that were 

detected in at least 75 percent of the Wilkison and others 

(2002) sewage samples, the compounds that were present 

at relatively elevated concentrations were identified. Only 

1.

2.

compounds that were present at elevated levels were 

retained because dilution likely plays an important role 

in this system. Compounds that typically occur in sewage 

near the analytical detection limit probably are not very 

useful sewage tracers. An arbitrary rule was established 

to identify compounds that occurred at relatively elevated 

concentrations—both mean and median concentrations 

that were greater than or equal to 0.75 micrograms per 

liter (μg/L) in the Wilkison and others (2002) data set. 

Compounds that met criteria 1 and 2 above were scored as 

positive and given a rank of 1. All other compounds were 

scored as negative and given a rank of zero.

The organic compound results from the untreated sewage 

samples (NCP1 and NCP4) collected as a part of this 

study were summarized. The same 0.75-μg/L arbitrary 

concentration value was used to identify whether the 

compound occurred at a relatively elevated level. For 

each of these two sewage samples, organic compounds 

that were present at elevated concentrations were given 

a score of 1, and compounds that were not detected (or 

not detected at greater than the 0.75-μg/L threshold) were 

given a score of zero. 

Next, each organic compound was screened for whether 

or not it could be considered indicative of domestic 

sewage. For example, caffeine, cotinine (a nicotine 

metabolite), detergent metabolites, and triclosan (a 

common antimicrobial compound in hand soaps) were 

considered indicative of sewage because they result 

from domestic activities. However, DEET (a common 

insecticide) and para-cresol (a wood preservative) were 

not considered indicative of domestic sewage because 

3.

4.

Table 2. Indicator tracer concentrations for six raw sewage samples collected in or around the Accotink Creek watershed, and the 

median tracer composition observed at site A1, U.S. Geological Survey streamgaging station 01654000 at Braddock Road, which defines the 

downstream limit of the study area.

[mg/L, milligrams per liter; mS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/100 mL, colonies per 100 milliliters; nd, no data; >, greater 

than; USGS, U.S. Geological Survey]

Sample 

ID

Sampling 

date

Sampling 

time

Boron 

(mg/L)

Chloride 

(mg/L)

Specific 

conductance 

(mS/cm)

Turbidity 

(NTU)

Surfactants 

(mg/L)

Fecal coliform 

bacteria

(col/100 mL)

Wastewater 

organic

compounds

Sampling location

NCP1 7/12/02 1015 0.199 70 832 135 5.0 2,300,000 yes Accotink main trunk line.

NCP2 7/12/02 1030 .232 74 833 178 5.0 3,400,000 nd Pohick main trunk line.

NCP4 7/12/02 1120 .591 80 965 236 7.5 1,300,000 yes Septic system.

SS1 7/12/02 1115 .281 66 806 >1,000 7.5 3,800,000 nd Sanitary sewer line.

SS2 7/12/02 1030 .177 83 721 116 10.0 750,000 nd Sanitary sewer line.

SS3 7/12/02 1245 .239 61 739 257 7.5 4,100,000 nd Sanitary sewer line.

Median concentration in raw 

sewage

0.236 72 819 207 7.5 2,850,000 nd

Median concentration at site A1 0.025 40 237 5.54 0.13 89 nd USGS streamgaging station 

01654000

Identification of Sewage Sources to Accotink Creek 11
they result from other activities. Organic compounds that 

were associated with domestic sewage were given a score 

of 1, and compounds that were not strongly associated 

with domestic sewage were given a score of zero. 

This analysis resulted in four categories with which to 

evaluate each compound and its association with sewage:

The Wilkison and others (2002) untreated sewage data

The NCP1 sewer-line sample data

The NCP4 septic-system sample data

Whether the compound was indicative of domestic 

sewage

6. The results of the four categories were summed for each 

compound, and the compounds that scored 3 or 4 were 

considered to be useful sewage tracers for identifying 

stream waters that contain sewage. This analysis identified 

a subset of 13 compounds that are indicative of sewage, 

and the general uses of these compounds are presented in 

table 3. 

Although this approach for selecting organic compounds 

relies on several arbitrary decisions, the resulting subset 

represents a group of 13 compounds that commonly are found 

in domestic sewage at relatively elevated concentrations. All 

13 compounds were detected in the NCP1 sewer-line sample, 

and 11 compounds were detected in the NCP4 septic sample 

(table 3). The absence of two compounds in the NCP4 sample 

possibly is because the compounds were not used in the 

5.

•

•

•

•

16-family subdivision using the septic system, or the compounds may have been degraded in the septic system. 

The octanol-water partition coefficient (partition coefficient) is a measure of how relatively hydrophobic a compound 

is—the greater the partition coefficient, the more hydrophobic 

the compound and the more likely the compound is to partition 

out of solution by adsorbing onto solid mineral surfaces. For 

example, of the compounds with partition coefficients in 

table 3, caffeine is the most soluble and diethylhexyl phthalate 

is the least soluble and the most likely to adsorb to particulate 

surfaces.

Because the organic compound analysis is extremely 

sensitive, both spiked samples and blank samples were 

submitted as blind samples to the laboratory during the course 

of this study. The spike samples were prepared in duplicate; 

all 13 organic compounds of interest were identified in the 

spikes, and the concentrations that were determined in each 

spike were highly consistent. Six blank samples were prepared 

and submitted to the laboratory for analysis; on average, 

one organic compound was detected in these blanks, which 

demonstrated that more than one organic compound should be 

present in a given sample before concluding that the sample 

contains sewage. 

Synoptic Sampling Results

Below is an overview of the synoptic sampling results, 

including a summary of the sampling events, and an analysis 

of the synoptic sampling data for the identification of both 

major and minor sewage sources.

Table 3. The subset of 13 organic compounds identified as useful sewage tracers, their primary uses, and octanolwater partition coefficients. Also included are concentrations of these tracers in two raw sewage samples.

[Kow, octanol-water partition coefficient; nd, not detected; —, not available. Shading indicates estimated concentration value]

Compound Log Kow NCP1 NCP4 Usesa

Caffeine 0.16 36 160 Beverages, diuretic, very mobile/biodegradable.

Cotinine .34 1 nd Primary nicotine metabolite.

Diethyl phthalate (DEP) 2.82 6.8 11 Plasticizer for polymers and resins.

Diethylhexyl phthalate (DEHP) 8.39 3.5 5.5 Plasticizer for polymers and resins, pesticide inert.

Galaxolide (HHCB) 6.26 .77 5.8 Musk fragrance, persistent and widespread use in ground water.

Menthol 3.38 18 18 Cigarettes, cough drops, liniment, mouthwash.

NPEO1-total — 12 31 Nonionic detergent metabolite.

NPEO2-total — 9.9 24 Nonionic detergent metabolite.

OPEO1 — 1.8 nd Nonionic detergent metabolite.

para-Nonylphenol (total NP) 5.92 36 59 Nonionic detergent metabolite.

Skatol 2.60 1 38 Fragrance, stench in feces and coal tar.

Tonalide (AHTN) 6.35 3.8 8.2 Musk fragrance, persistent and widespread use in ground water.

Triclosan 4.66 5.2 6.8 Disinfectant, antimicrobial.

a

 Zaugg and others, 2002, 2006.

12  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Summary of the Sampling Events

Eight synoptic sampling events were conducted during 

this study from December 2001 to September 2004. Summary 

details related to each synoptic sampling event are presented 

in table 4, and a map of all the synoptic sampling sites is given 

in figure 3. Variations occurred in the number of samples collected during the first four sampling events because of slight 

variations in the flow conditions for each event; for example, 

123 samples were collected during the second sampling event 

when the streamflow in Accotink Creek (at USGS streamgaging station 01654000) was 8.1 cubic feet per second (ft3

/s), 

and only 90 samples were collected during the fourth sampling 

event when the flow in Accotink Creek was only 2.4 ft3/s and 

several of the synoptic sampling sites were dry. 

All of the sampling events were performed by starting at 

the most downstream location in the watershed and moving 

in an upstream direction. In this manner, none of the stream 

samples were compromised by any upstream sampling 

activity. Despite the similarity of all synoptic sampling events, 

there were differences associated with each sampling event 

that are noted here to provide the environmental context for 

each event:

First sampling event (December 2001): No samples 

were collected for analysis of wastewater organic compounds; 

these analyses did not occur until the third sampling event. 

Laboratory results for the bromide analyses failed all qualityassurance tests (related to blind duplicates and split samples), 

causing the bromide data to be rejected. Therefore, no bromide 

data are available for this event.

Second sampling event (April 2002): No samples were 

collected for analysis of wastewater organic compounds. 

Again, laboratory results for the bromide analyses failed 

several quality-assurance tests (related to blind duplicates 

and split samples that were run by the USGS National Water 

Quality Laboratory), causing the bromide data to be rejected. 

Therefore, no bromide data are available for this event.

Third sampling event (July 2002): This sampling event 

was the first for which selected samples were submitted for 

analysis of confirmatory organic compounds. Following day 2 

of sampling, there was a light overnight rainfall that did not 

appear to result in any runoff processes. By the morning of 

day 3, the streamgage at Braddock Road had not recorded 

an obvious runoff response, and investigation of a number of 

storm-drain outfalls indicated that the storm-drain networks 

were not responding to the rainfall. Because of these observations, sampling continued on the third and fourth days. When 

the bacteria samples from day 3 were enumerated, however, it 

became apparent that the fecal coliform counts were extremely 

elevated (relative to counts for the first 2 days), and that the 

rainfall had likely initiated a runoff response in the watershed. 

A subsequent detailed inspection of the Braddock Road hydrograph confirmed a very small increase (0.04 ft) in water level 

following the rainfall. Once the effects of the rainfall were 

realized, six sites that were sampled on day 3 were resampled 

on day 5. These data confirmed a substantial decrease in the 

bacterial concentrations between day 3 and day 5, and indicate 

that the samples collected on day 3 and possibly day 4 were 

affected by the rainfall and runoff. As such, only the data 

for days 1 and 2 (including the organic compound data for 

these two days) were retained in the database and analyzed as 

base-flow samples. In short, the data from the third sampling 

event represent only the lower half of the watershed. Lastly, 

the analytical results for bromide continued to fail the qualityassurance tests (related to blind duplicates and split samples 

that were run by the USGS National Water Quality Laboratory), causing the bromide data to be rejected. Therefore, no 

bromide data are available for this event.

Fourth sampling event (October 2002): The Fairfax 

Environmental Services Laboratory changed its analytical 

Table 4. Summary of the number and type of samples collected from the Accotink Creek watershed, Virginia, during 

synoptic sampling in relation to discharge at the Braddock Road streamgaging station.

[ft3/s, cubic feet per second]

Sampling 

event 

number

Sampling date Main-channel 

samples

Tributary 

samples

Storm-drain 

samples

Total 

samples 

collected

Organic 

samples 

analyzed

Accotink 

Creek flow 

at Braddock 

Road (ft3/s)

1 December 3–7, 2001 15 51 44 110 0 2.7

2 April 2–5, 2002 16 55 52 123 0 8.1

3 July 8–12, 2002 10 14 17 41 6 .32

4 October 21–24, 2002 15 46 29 90 18 2.4

5 April 14–17, 2003 19 56 47 122 34 19.8

6 November 10–11, 2003 11 26 20 57 12 19

7 February 17–20, 2004 21 55 33 109 18 18

8 September 12–14, 2004 8 63 44 115 15 4.9

Identification of Sewage Sources to Accotink Creek 13
Figure 3. Location of sampling sites in the Accotink Creek watershed, Virginia.

procedure for bromide, and the quality-assurance tests 

indicated that the bromide data were usable. This marks the 

first time that the chloride/bromide ratio could be calculated.

Fifth sampling event (April 2003): Having completed 

four sampling events, several new sampling sites were added 

in the watershed during this event to better characterize 

the areas with relatively elevated tracer concentrations. To 

accommodate these additional sampling sites, several sites 

with relatively low tracer concentrations were not sampled.

Sixth sampling event (November 2003): After 2 days of 

sampling in only the lower half of the watershed, a rainstorm 

occurred that clearly initiated runoff. Because samples already 

had been submitted to the Fairfax Environmental Services 

Laboratory and samples for wastewater organic compounds 

were already being analyzed at the USGS National Water 

Quality Laboratory, it was decided to use the data from this 

partial sampling event.

Seventh sampling event (February 2004): During this 

event, several new sampling sites were added to the basin 

to better characterize areas with relatively elevated tracer 

concentrations. To accommodate these additional sampling 

sites, several sites with relatively low tracer concentrations 

were not sampled. 

Eighth sampling event (September 2004): By this 

sampling event, many of the sampling sites were well characterized, and sites with consistently low tracer concentrations 

14  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System

77o16'

77o18'

77o20'

38o54'

38o52'

38o50'

77o14'

77o12'

Braddock

Road

Accotink

Creek

Accotink

Creek

Crook Branch

Daniels

Run

Little River Turnpike

Lee Highway

Fairfax

FAIRFAX CO

495

Long

Branch

Bear

Branch

Hunter

Run

Nutley Street

Chain

Bridge

Road

66

0 1

0 1

2 MILES

2 KILOMETERS

01654000

Figure 3. Location of sampling sites in the Accotink Creek watershed of Virginia.

01654000

EXPLANATION

U.S. Geological Survey streamgaging station and number (site A1)

Accotink Creek sampling site and number

Tributary site and number

Storm-drain site and number

A13

T18

S41

Arlington Boulevard

Base from digital files:

Drainage basin from U.S. Geological Survey Open-File Report 2006-1308

U.S. Geological Survey, digital line graph hydrography 1:24,000

County boundaries from TIGER files; 1:100,000; 1994

Virginia State Plane projection, North zone, units feet, NAD 83, central meridian 7830’W

A2

A3

A4

A5

A6

A7

A8

A9

A10 A11

A12 A13

A14

A15

A16 A13B

A14A

A15A1

A16A1

S1

S2

S3

S4

S5

S6

S7

S8

S9

S52

S10

S11

S12

S13 S14 S15

S16

S29

S17

S18

S19

S20

S22

S23

S24

S26

S25

S27

S30

S28

S31

S32

S37

S38

S39 S40

S42 S41

S45

S46

S47

S48

S49

S50

S51

T1

T2

T3 T4

T5 T6

T7

T9

T10

T12

T13 T14

T15

T16

T59

T17 T19

T20

T21

T22

T23

T24

T61

T26

T27

T29

T30

T28

T32

T33

T34

T36

T37

T38

T40

T41

T42

T43

T44

T45

T49

T50

T54

T51

T52

T53

T56

T57

T13A

T25A

T27A

T35A

T51B

T51A

T23A1

T23A2

T24A1

T24B1

T24A2

T31A1

T31A2

T51C

A13A A15B

A15A2

S21

S33

S34

S35

S36

S43

S44

T8

T58

T11

T18

T25

T31 T60

T35

T39

T47

T48

T46

T55

T51BLD
had been identified. Conversely, numerous sites exhibited 

extremely variable tracer levels; these inconsistent waterquality levels made it challenging to identify sites with sewage 

sources. Accordingly, only sites that were either relatively 

variable or sites with relatively elevated tracer levels were 

sampled. Additional sampling elements were added to this 

sampling event to permit improved characterization of the 

variability that had been observed at these sites. By reducing 

the overall number of sampling sites, each remaining site 

was sampled twice during this sampling event (roughly 

1–2 days apart). Additionally, optical brightener monitors 

were deployed at all the sites that were sampled, and intensive 

sampling over a 24-hour period was conducted at several of 

the sampling sites. Lastly, the additional sampling of stormdrain networks also was performed at the end of this sampling 

event. 

Cases of Major Sewage Inputs

During two synoptic sampling events, direct sewage 

sources to Accotink Creek were identified. These sewage 

sources were of sufficient volume that they caused extremely 

elevated tracer levels in the stream-water samples, which 

demonstrated how effective the suite of sewage tracers can be 

for identifying major sewage sources to streams. One sewage 

source occurred at site T13, and another occurred at site 

T51BLD (fig. 3), and both incidents are discussed in detail. 

The first major sewage source that was discovered 

during a synoptic sampling event occurred during the fourth 

sampling event. While sampling an unnamed tributary to 

Accotink Creek (site T13), the tributary water was decidedly 

gray in color and a sewage odor was prevalent. Elevated 

concentrations of the water-quality tracers also indicated the 

presence of sewage in this tributary. With knowledge that the 

tributary likely contained sewage, a field crew followed the 

gray water approximately 0.25 mile upstream from site T13 

and discovered an overflowing sewer-line manhole that was 

contributing untreated sewage to the tributary. Fairfax County 

Wastewater Management was contacted and they responded 

and removed a clog that had developed in the sewer line just 

below the overflowing manhole. 

The data that were collected downstream from this 

overflowing sewer line provided field validation of the 

multiple-tracer approach and demonstrated how far downstream the signal from this sewage source could be detected 

(table 5).

Table 5. Indicator tracer concentrations in samples collected during and following a sewer-line overflow that 

contributed sewage directly to an unnamed tributary, approximately 0.25 mile upstream from site T13, in the Accotink 

Creek watershed of Virginia.

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/100 mL, colonies per

100 milliliters; <, less than. Shading indicates estimated concentration value. Site A7 is located just upstream from where the sewageimpacted tributary drains into Accotink Creek and represents unimpacted conditions; sites A6–A1 are located downstream from the sewage 

input and are impacted by this overflowing sewer line. Also presented are the indicator tracer concentrations (at site T13 and site T13A, 

which are located 30 feet below the overflowing sewer line) that were observed following the repair of the sewer line]

Site ID

(fig. 3) Event Sampling date

Sampling 

time

Boron 

(mg/L)

Chloride 

(mg/L)

Specific 

conductance 

(mS/cm)

Dissolved

oxygen 

(mg/L)

Turbidity 

(NTU)

Surfactants 

(mg/L)

Fecal 

coliform 

bacteria 

(col/100 mL)

During the period of the overflowing sewer line

A7 4 10/22/02 1040 0.032 22 159.8 9.97 7 0.13 290

T13 4 10/22/02 1015 .166 64 674 3.13 19 5 870,000

A6 4 10/22/02 855 .060 28 213.1 8.07 7 .75 16,000

A5 4 10/21/02 1625 .042 27 206.2 7.33 8 .5 76,000

A4 4 10/21/02 1330 .046 27 180.1 8.67 5 .25 1,500

A3 4 10/21/02 1225 .048 26 181 8.50 6 .25 3,000

A2 4 10/21/02 1245 .029 23 168 9.65 6 .25 530

A1 4 10/21/02 1120 .029 22 163 8.96 6 .13 630

Following the repair of the overflowing sewer line

T13A 5 4/14/03 1630 0.010 53 265.5 9.26 4 0.13 123

T13A 6 11/10/03 1545 .013 52 159.3 9.15 2 .13 77

T13A 7 2/17/04 1600 .017 87 277.1 12.20 2 .13 3

T13 5 4/14/03 1725 .007 64 318 9.71 2 .13 87

T13 6 11/10/03 1645 .012 52 266.7 10.47 2 .13 43

T13 7 2/17/04 1700 .012 89 293.7 12.41 2 0 < 3

Identification of Sewage Sources to Accotink Creek 15
Although site T13 is located approximately 0.25 mile 

downstream from the overflowing sewer line, the sewagetracer concentrations at the site were similar to the raw-sewage 

samples in table 2. For comparison, a water-quality sample 

was collected from Accotink Creek just upstream from the 

confluence of the unnamed tributary and Accotink Creek 

(site A7, fig. 3). The tracer concentrations observed at site T13 

(affected by sewer overflow) and A7 in October 2002 are strikingly different (table 5). The sample collected at site T13 had 

elevated surfactant, turbidity, boron, fecal coliform bacteria, 

chloride, and specific conductance concentrations. The sample 

from site T13 also had dissolved-oxygen concentrations 

that were much less than those observed at site A7. These 

distinctly different tracer concentrations further support the 

effectiveness of this collection of sewage tracers for locating 

major sewage sources to a stream.

In addition, elevated downstream tracer concentrations 

from this overflow were evident in the Accotink Creek waterquality data nearly 2 miles downstream from the confluence of 

the unnamed tributary with Accotink Creek (table 5). Elevated 

fecal coliform bacteria and surfactant concentrations were 

detected in the samples collected from sites A6 downstream 

through site A2. By site A1, the sewage signal became sufficiently dilute that most of the water-quality data appeared to 

be similar to the background water quality typically observed 

at Braddock Road, with the exception of fecal coliform 

bacteria concentrations, which remained elevated relative to 

the background levels typically observed at this site. 

Following repair of the sewer line by the Fairfax County 

Wastewater Services, site T13 was sampled several more 

times, as was a new sampling site (T13A) that was located 

about 60 feet downstream from the overflowing sewer line. 

These post-repair data represent some of the lowest fecal 

coliform and surfactant concentrations of all samples in the 

watershed (table 5), indicating that the repair was effective.

Despite the fact that the overflowing sewer line was the 

obvious source of sewage in the unnamed tributary, a wastewater organic compound sample was collected at site T13 as a 

positive control. As expected, detectable concentrations of all 

13 compounds were observed in the sample, further supporting the use of this suite of wastewater organic compounds as a 

confirmatory tracer of sewage (table 6).

Another sewage incident was observed during the eighth 

sampling event. Data from earlier sampling events indicated 

that the tributary upstream from site T51 (fig. 3) likely was 

impaired by sewage. These data are presented and discussed 

later in this report. After sampling site T51, a detailed reconnaissance was performed upstream from the site, and a small, 

previously unsampled storm-drain outfall was observed to be 

flowing near site T51B. This storm drain was labeled as site 

T51BLD and was sampled for a subset of indicator tracers 

and a complete suite of confirmatory tracers. Site conditions 

prevented sampling for all the indicator tracers. The results of 

this sampling are presented in table 7. The site had relatively 

elevated concentrations of all sewage indicators, although 

the boron concentrations were not especially elevated. The 

Table 6. Wastewater organic-compound 

concentrations observed at tributary site T13 in 

response to an overflowing sewer line located 

0.25 mile upstream from site T13 in the Accotink 

Creek watershed of Virginia.

[mg/L, micrograms per liter. Shading indicates estimated 

concentration value]

Compound (mg/L) Site T13

Caffeine 27

Cotinine .78

Diethyl phthalate (DEP) 5.2

Diethylhexyl phthalate (DEHP) 3

Galaxolide (HHCB) .51

Menthol 15

NPEO1-total 18

NPEO2-total 7.5

OPEO1 1.7

para-Nonylphenol (total NP) 19

Skatol .66

Tonalide (AHTN) 2.2

Triclosan 2.7

presence of 11 confirmatory tracer compounds further 

demonstrates that the sample contained sewage. 

Because site T51BLD is located in Fairfax City, the City 

officials were informed of the sewage leak and location. City 

crews responded and conducted a visual inspection of the 

storm-drain line using a closed circuit video camera, but no 

obvious source of the sewage in the drain could be identified. 

City crews then inspected several nearby office buildings for 

cross-connected lines, malfunctioning systems, floor drains, 

and such. Despite these efforts, the source of the sewage was 

not identified. 

Following the City’s unsuccessful attempts to locate the 

source of the sewage in this storm drain, additional samples 

were collected from the storm drain during November and 

December 2004 to determine whether the sewage was a 

persistent problem. The additional samples were analyzed 

only for fecal coliform bacteria and surfactant concentrations, 

and the results are included in table 7. These additional 

samples indicate substantially reduced fecal coliform bacteria 

concentrations in the storm-drain outfall. Although surfactant 

concentrations were elevated in the two additional samples, 

only one sample had substantially elevated concentrations 

relative to background levels. These data seem to indicate that 

the sewage contributions in the storm drain are not persistent, 

which may be the reason that the Fairfax City staff could not 

locate the source of the sewage. As will be discussed later, 

there still may be a source of sewage in this tributary above 

site T51, as it does not appear that the sewage source has 

disappeared completely.

16  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
During this study, the occurrences of three major 

direct sewage sources to the Accotink stream network were 

documented:

The episodic occurrence of sewage at site S7 that was 

detected during the watershed reconnaissance.

The overflowing sewer line at site T13A.

The occurrence of sewage at site T51BLD that disappeared before the source could be identified.

•

•

•

Although the discovery and correction of the sewage 

source at site T13A is an important finding and resulted in a 

water-quality improvement in Accotink Creek, the other two 

sources were not identified. Such episodic occurrences of 

sewage could recur at any time, and it will be very difficult to 

identify the sources without detailed monitoring. 

 Initial expectations were that more than three major 

sources of sewage would have been observed in the Accotink 

Creek watershed during this study. Observing so few major 

sources is positive in that it indicates that the overall integrity 

of the sewage-handling infrastructure in the basin is not suffering from widespread, major occurrences of sewage contributions during relatively low streamflow conditions. Because 

so few major sewage sources to the streams were identified 

during the study, the possibility of low-volume (minor) sewage 

sources was evaluated. 

Use of the Tracers for Identifying Minor Sewage 

Sources

Although the suite of sewage tracers used in this study 

was selected specifically to identify sewage sources, the tracers were not selected for their ability to identify minor sewage 

sources. Minor sewage sources are here defined as those that 

contribute relatively low volumes of sewage to a stream and 

result in a water sample with some sewage characteristics that 

are greatly diluted by relatively clean stream water. 

Selection of the Most Sensitive Tracers for Identifying 

Minor Sewage Sources

To better understand which of the indicator tracers 

are most effective for identifying minor sewage sources to 

streams, dilution calculations were performed to evaluate the 

relative difference between the typical tracer concentrations 

that were observed in Accotink Creek and the tracer concentrations that were observed in untreated sewage. Conceptually, 

the tracers with the greatest relative concentration differences 

between the typical stream concentration and the untreated 

sewage concentration will be the best tracers to use in identifying minor sewage sources because they are least likely to be 

masked by the effects of dilution. For this analysis, the data in 

table 2, which includes the indicator tracer concentrations in 

raw sewage samples and the median concentration of a typical 

Accotink Creek sample, were used to calculate the relative 

difference. The ratio of the median sewage concentration 

to the median stream concentration was used to identify the 

tracers most likely to be useful in identifying minor sewage 

sources (table 8). Through this analysis, the concentrations of 

surfactants, fecal coliform bacteria, boron, and turbidity in raw 

sewage were all observed to be at least nine times greater than 

those typically observed in streams. Conversely, the ratios of 

chloride and specific conductance indicate that the stream levels were not very different from the levels typically observed 

in sewage. Consequently, neither chloride nor specific 

conductance was considered quantitatively in the evaluation 

Table 7. Concentrations of indicator and confirmatory tracer 

compounds associated with sewage at storm-drain site T51BLD 

in the Accotink Creek watershed, Virginia. Also presented are 

the fecal coliform and surfactant concentrations from two 

additional samples that were collected from site T51BLD several 

months later.

[mg/L, milligrams per liter; —, value not determined; NTU, nephelometric 

turbidity units; col/100 mL, colonies per 100 milliliters; mg/L, micrograms 

per liter; nd, compound not detected. Shading indicates estimated concentration value]

Indicator tracers

Compound Sampling date

9/14/04 11/30/04 12/12/04

Boron (mg/L) 0.031 — —

Chloride (mg/L) 67 — —

Turbidity (NTU) 229 — —

Surfactants (mg/L) 25 0.25 10

Fecal coliform bacteria 

(col/100 mL)

4,000,000 60 200

Confirmatory tracers

Compound (mg/L) 9/14/04

Caffeine 2.8

Cotinine 3.2

Diethyl phthalate (DEP) 1.2

Diethylhexyl phthalate 

(DEHP) 24

Galaxolide (HHCB) nd

Menthol 2.1

NPEO1-total 4

NPEO2-total 14

OPEO1 2.3

para-Nonylphenol (total 

NP) 5

Skatol .11

Tonalide (AHTN) nd

Triclosan .24

Identification of Sewage Sources to Accotink Creek 17
of minor sewage sources. Although turbidity appears to be a 

good indicator of minor sewage sources, it was not used in 

the quantitative analysis because many of the particulates that 

contribute to elevated turbidity levels in sewage will readily 

settle out in streams, thereby decreasing the effectiveness of 

turbidity to be a good indicator (note in table 5, for example, 

how quickly the turbidity signal decreased). Accordingly, 

it was decided that surfactants, fecal coliform bacteria, and 

boron were likely the most sensitive indicator tracers to use in 

identifying minor sewage sources. 

The use of several other tracers that were part of the 

indicator tracer suite also was considered for identifying minor 

sewage sources, but ultimately these tracers were not used for 

various reasons. These tracers included water temperature, 

DO, and the Cl/Br ratio. Water temperature initially was 

considered as a sewage tracer, presumably because the water 

temperature in the area around the sewage source would be 

relatively different from the temperature of nearby water 

samples. After several early sampling events, however, it was 

observed that many of the storm drains had pronounced water 

temperature fluctuations throughout the day (as much as 5 to 

10 degrees Celsius (°C)), depending on the daily change in 

air temperature. Therefore, differences in water temperature 

were considered unreliable as tracers of minor sewage sources 

in this system. Similarly, DO concentrations throughout the 

watershed were observed to fluctuate on a daily basis (more 

elevated in the afternoon); the temporal variability in this 

tracer made it poorly suited for the identification of minor 

sewage sources. Lastly, the Cl/Br concentrations ratio was 

expected to provide a powerful tool for the identification of 

sewage sources to streams. During the first three sampling 

events, however, problems with laboratory analyses resulted in 

the bromide data being rejected. For event 4 and all subsequent 

events, the bromide results met the data-quality needs of the 

project, and the ratios were calculated. The median Cl/Br ratio 

for the fourth sampling event was 667, which is considered 

elevated and indicative of either sewage or halite additions 

in Accotink Creek (Thomas, 2000). Although halite does not 

occur naturally in the basin, road salting is performed widely 

during the winter months. Road salting makes it difficult to 

identify whether the elevated Cl/Br ratio is the result of the 

presence of either sewage or halite in the streams. This issue 

was resolved, however, because of nearly continuous specific 

conductance data that were available at the Braddock Road 

streamgaging station for a portion of this study; approximately 

13 months of data are presented in figure 4. These data illustrate a specific conductance pattern that is highly indicative of 

road salt because the specific conductance values peak during 

the winter months, when the road salts are actively in use, and 

decline as the salts leach out of the watershed over the rest of 

the year. These specific conductance data indicate that the use 

of the Cl/Br ratio in identifying sewage sources to Accotink 

Creek is compromised by the road-salting pattern in the basin; 

consequently, this potentially powerful sewage tracer cannot 

be used quantitatively to identify minor sewage sources. 

Therefore, the most sensitive of the indicator tracers appear to 

be surfactants, fecal coliform bacteria, and boron; these most 

sensitive indicator tracers were subsequently used to evaluate 

the likelihood of minor sewage sources in the basin. 

In addition to the use of boron, surfactants, and fecal 

coliform bacteria for identifying minor sewage sources to 

Accotink Creek, the 13 organic compounds that were used 

as confirmatory tracers also were used for identifying minor 

sewage sources. These organic compounds were considered 

useful because the analytical method is able to detect the 

presence of these compounds at levels far below the reporting levels. Although the analysis of these compounds at 

levels below their reporting levels is no longer considered 

quantitative, the presence of the compound can be verified. 

Therefore, the number of organic compounds detected in a 

given sample (rather than the specific concentration of each of 

the compounds) was used as a measure of the likelihood that 

the given sample contains sewage. For example, a sample that 

contains detectable levels of 10 of the 13 organic compounds 

(regardless of the concentration at which the compounds 

occur) is likely to contain some sewage, while a sample that 

has detectable concentrations of only 1 or none of the organic 

compounds is unlikely to contain sewage. 

Table 8. Ratio of median indicator tracer concentrations in six raw sewage samples to the median indicator 

tracer concentrations observed in stream samples at site A1 for use in determining which tracers are most 

sensitive to minor sewage sources in the Accotink Creek watershed, Virginia.

[mg/L, milligrams per liter; mS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units;

col/100 mL, colonies per 100 milliliters]

Boron 

(mg/L)

Chloride 

(mg/L)

Specific 

conductance 

(mS/cm)

Turbidity 

(NTU)

Surfactants 

(mg/L)

Fecal 

coliform 

bacteria 

(col/100 mL)

Median concentration in raw sewage 0.236 72 819 207 7.5 2,850,000

Median concentration at site A1 .025 39.5 237 5.5 .13 89

Ratio of median concentrations in 

sewage to median concentrations 

at site A1

9 2 3 37 58 32,203

18  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Qualitative Summary of the Synoptic Sampling Results

The results of each sampling event were summarized for 

each site to provide an overall understanding of the waterquality conditions. Detailed indicator tracer data are available 

in Appendix 1, and detailed wastewater organic compound 

data are available in Appendix 2. The summary in table 9 can 

be used to qualitatively identify sites that may have minor 

sewage sources, based on the median concentrations of fecal 

coliform bacteria, surfactants, and boron that were calculated 

for each site and the number of water samples collected from 

each site. Additionally, the number of samples that were 

submitted for analysis of confirmatory organic compounds 

and the median number of compounds detected at each site are 

provided (table 9). 

 The summary in table 9 can be used to address two 

fundamental issues in the Accotink Creek watershed:

Identifying sites that have elevated fecal coliform 

bacteria concentrations

Identifying sites that may be subject to sewage inputs

The summary results are presented in decreasing order 

by the median fecal coliform concentration at each site, which 

allows direct determination of the sites in the basin with the 

most elevated fecal coliform concentrations. In theory, this list 

of sites could be used as a priority list for further investigation 

in an attempt to reduce fecal coliform contributions to the 

stream. Although not all bacteria from each sampling site are 

transported into Accotink Creek and contribute to the bacterial 

•

•

impairment at the Braddock Road streamgaging station, the 

data provide a starting point for remediation or implementation of best management practices (BMPs) that may occur as 

part of future watershed-management practices. Table 9 also 

offers a relatively simple mechanism for identifying the sites 

that may be affected by sewage. The median tracer concentrations and the median number of organic compounds that were 

detected were conditionally formatted based on the relative 

concentrations that were considered to be background levels. 

Although the selection of these background conditions were 

somewhat arbitrary (based on approximate median observed 

boron and surfactant concentrations throughout the watershed 

and the geometric mean standard for fecal coliform concentrations), they assisted in data analysis because sites that are 

subject to sewage inputs are more likely to have relatively 

elevated concentrations of fecal coliform bacteria, surfactants, 

and boron in addition to relatively elevated numbers of organic 

compound detections. For example, site S3 (near the bottom of 

table 9) had relatively low tracer concentrations and very few 

detections of organic compounds in the samples, but site S46 

(near the top of table 9) had relatively elevated indicator 

tracer concentrations and a relatively large number of organic 

compound detections in the samples (indicating that this site 

may have sewage sources). Caution is advised, however, when 

drawing inferences from any sites represented by only one 

or two samples, as these few samples may not fully represent 

the sites. Despite its qualitative nature, table 9 provides a 

mechanism for easily evaluating the water quality at each site 

relative to the water quality observed at other sampling sites 

and for identifying sites that may have sewage sources. 

Figure 4. Time series of specific conductance in Accotink Creek at the Braddock Road streamgaging station (01654000) in the 

Accotink Creek watershed, Virginia. To enhance resolution of the lower specific conductance values and the general flushing 

response over the year, the y-axis has been truncated at 1,000 microsiemens per centimeter. 

Identification of Sewage Sources to Accotink Creek 19

0

100

200

300

400

500

600

700

800

900

1,000

MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC JAN FEB MAR APR

DATE

0

50

100

150

200

250

300

350

400

450

500

DISCHARGE, IN CUBIC FEET PER SECOND

Specific conductance

Discharge

SPECIFIC CONDUCTANCE, IN MICROSIEMENS

PER CENTIMETER AT 25 DEGREES CELSIUS 

Figure 4. Time series of specific conductance in Accotink Creek at the Braddock Road streamgaging station (01654000) in the Accotink Creek

watershed, Virginia. To enhance resolution of the lower specific conductance values and the general flushing response over the year,

the y-axis has been truncated at 1,000 mS/cm.

Maximum in-stream specific conductance levels exceeded

6,000 microsiemens per centimeter during February 2002–April 2003.

2002 2003
Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/

100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number 

of 

organics 

samples

T51BLD 0.031 25.00 4,000,000 1 11 1

T51B .016 1.50 10,400 3 8 1

S37 .014 .12 6,400 6 1 2

T51A .022 2.50 4,800 5 10 1

T35A .014 .13 3,700 5 9 1

T35 .026 .13 3,500 7 7 3

T51C .020 .13 2,800 3 nd nd

S46 .087 .25 2,400 7 8 4

S18 .032 .13 2,000 9 2 2

A15B .021 .13 1,875 3 3 1

T23A2 .016 .13 1,571 4 nd nd

T24B1 .019 .13 1,255 4 nd nd

S41 .016 .13 1,233 7 3 1

S51 .035 .13 1,233 7 3 3

S42 .031 .13 1,200 7 1 1

S7 .009 .13 1,133 9 4 2

T59 .023 .00 1,100 1 nd nd

S8 .019 .20 1,033 9 4 3

T23A1 .017 .13 1,033 4 6 1

S20 .010 .13 933 9 6 2

T22 .027 .13 933 7 3 2

T31A1 .018 .19 927 4 nd nd

T3 .030 .13 910 6 nd nd

T50 .022 .13 800 7 1 2

T56 .023 .13 700 7 2 2

T51 .025 .38 664 8 8 5

T18 .020 .14 655 6 nd nd

T24 .021 .13 639 10 3 7

T24A1 .022 .25 600 5 nd nd

S23 .008 .13 570 7 0 1

S48 .020 .13 508 7 3 2

T25A .011 .13 470 5 nd nd

S24 .011 .13 445 8 nd nd

S5 .013 .13 410 9 2 1

T24A2 .022 .13 410 5 nd nd

T55 .036 .13 410 7 2 1

S29 .028 .13 400 9 2 3

A6 .022 .13 385 8 7 2

A13 .025 .13 370 8 3 2

T44 .024 .13 370 7 nd nd

T29 .025 .13 350 5 2 1

T33 .023 .13 330 8 1 1

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/

100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number 

of 

organics 

samples

T23 0.023 0.13 320 10 4 3

S44 .058 .13 310 7 4 3

T42 .021 .13 300 5 nd nd

T38 .012 .13 275 6 nd nd

T31 .027 .13 270 8 3 3

S16 .015 .15 250 3 nd nd

T37 .016 .13 240 7 nd nd

T25 .018 .13 235 8 3 1

T26 .026 .13 230 4 nd nd

S31 .023 .13 200 7 nd nd

A5 .022 .12 197 6 nd nd

A14 .019 .15 195 5 1 1

T27 .016 .13 195 6 nd nd

T41 .018 .13 193 5 nd nd

S47 .027 .13 190 6 nd nd

S28 .008 .13 182 4 nd nd

A11 .024 .13 180 7 nd nd

A9 .022 .13 180 7 nd nd

T1 .016 .13 180 7 nd nd

A16 .023 .13 177 5 2 1

S39 .009 .13 177 4 nd nd

A13B .016 .13 170 1 nd nd

A7 .022 .13 170 7 nd nd

S35 .051 .13 170 7 1 1

T52 .017 .13 170 5 nd nd

T60 .015 .13 170 3 nd nd

A13A .035 .13 163 2 nd nd

A12 .025 .13 162 6 nd nd

S6 .027 .44 162 8 6 3

A8 .022 .13 160 7 nd nd

S13 .021 .13 160 9 nd nd

S52 .037 .13 152 8 nd nd

S17 .021 .13 143 6 nd nd

T2 .019 .13 133 7 nd nd

A10 .022 .15 130 1 nd nd

S19 .034 .13 130 5 nd nd

S26 .012 .10 127 3 nd nd

A14A .018 .13 122 2 nd nd

T21 .022 .10 120 1 nd nd

T12 .020 .13 120 6 nd nd

A15A2 .023 .13 118 2 nd nd

T27A .013 .13 116 2 nd nd

Table 9. Median concentrations of fecal coliform bacteria, surfactant, and boron; the number of water samples collected and analyzed 

for confirmatory tracers; and the median number of organic compounds detected in these confirmatory tracer samples from the 

synoptic sampling sites in the Accotink Creek watershed, Virginia.

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters; nd, no data. Red indicates fecal coliform greater than or equal to 200, surfactants greater 

than 0.13, and boron greater than 0.020. Organic compound detections less than 2.5 are green, between 2.5 and 5.4 are blue, and greater than or equal to 5.5 are 

red. Conditional formatting has been used to identify which sites had elevated tracer concentrations or elevated numbers of organic compound detections. The 

table is sorted by the median fecal coliform concentrations]

20 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/

100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number 

of 

organics 

samples

T39 0.023 0.13 115 4 nd nd

T40 .026 .13 110 7 1 1

S22 .039 .13 105 8 nd nd

A15 .026 .13 103 7 3 3

T16 .016 .00 103 3 1 1

T20 .024 .13 103 5 nd nd

A15A1 .019 .19 102 2 nd nd

S50 .030 .13 100 7 2 2

T15 .017 .13 100 3 nd nd

T8 .020 .10 100 5 nd nd

T57 .026 .13 99 4 nd nd

T30 .039 .10 97 1 nd nd

T58 .005 .00 97 1 nd nd

T31A2 .020 .19 96 2 nd nd

T4 .024 .00 93 3 0 1

T43 .019 .13 90 5 nd nd

T9 .021 .13 90 7 1 3

A1 .025 .13 89 6 nd nd

A2 .019 .12 85 6 nd nd

S4 .010 .08 85 4 nd nd

T7 .010 .05 83 7 nd nd

A4 .024 .14 80 4 nd nd

S10 .039 .05 79 2 nd nd

T36 .020 .13 78 8 0 3

T13A .013 .13 77 3 0 1

T6 .020 .13 77 5 2 1

S33 .016 .13 75 4 nd nd

S15 .020 .13 73 7 1 2

T49 .015 .10 73 3 nd nd

T32 .024 .13 70 6 nd nd

A3 .019 .13 69 6 nd nd

T48 .024 .13 67 5 1 1

T53 .025 .10 67 5 nd nd

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/

100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number 

of 

organics 

samples

T28 0.012 0.12 64 2 nd nd

T19 .024 .13 63 7 nd nd

T13 .012 .00 59 5 7 2

S27 .008 .13 58 4 nd nd

T34 .014 .07 54 2 nd nd

T11 .022 .15 53 3 nd nd

T17 .015 .00 49 3 nd nd

T45 .033 .13 45 5 nd nd

S1 .009 .07 45 4 nd nd

S14 .012 .15 42 3 nd nd

T46 .024 .13 42 5 nd nd

T47 .017 .13 40 5 0 1

T10 .027 .13 39 3 nd nd

S2 .011 .13 37 3 nd nd

S43 .018 .00 35 3 nd nd

S21 .149 .25 32 2 nd nd

T54 .017 .12 32 4 nd nd

S49 .039 .13 28 5 nd nd

S25 .028 .00 25 3 nd nd

S30 .021 .07 23 2 nd nd

S34 .015 .10 23 4 nd nd

T5 .018 .00 22 1 nd nd

S32 .027 .13 20 6 nd nd

T14 .013 .13 20 3 nd nd

S9 .005 .15 18 3 nd nd

S3 .008 .00 16 7 2 3

S11 .012 .09 15 2 nd nd

S40 .007 .09 15 2 nd nd

A16A1 .018 .13 10 1 nd nd

S45 .047 .13 7 3 nd nd

S12 .037 .07 3 4 0 1

S36 .049 .20 3 3 nd nd

S38 .014 .13 3 3 nd nd

Table 9. Median concentrations of fecal coliform bacteria, surfactant, and boron; the number of water samples collected and analyzed 

for confirmatory tracers; and the median number of organic compounds detected in these confirmatory tracer samples from the 

synoptic sampling sites in the Accotink Creek watershed, Virginia. — Continued

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters; nd, no data. Red indicates fecal coliform greater than or equal to 200, surfactants greater 

than 0.13, and boron greater than 0.020. Organic compound detections less than 2.5 are green, between 2.5 and 5.4 are blue, and greater than or equal to 5.5 are 

red. Conditional formatting has been used to identify which sites had elevated tracer concentrations or elevated numbers of organic compound detections. The 

table is sorted by the median fecal coliform concentrations]

Identification of Sewage Sources to Accotink Creek  21
Quantitative Summary of the Synoptic Sampling Results

A quantitative summary of the data was developed 

based on the relative concentrations of the three most sensitive indicator tracers (fecal coliform bacteria, surfactants, 

and boron) and the relative number of organic compounds 

that were detected, to provide a quantitative mechanism 

for identifying the sampling sites that are most likely to be 

affected by sewage. Two analyses were conducted; the first 

considered only the sites where at least one organic compound 

sample was collected, and the second considered all sites 

that were sampled (regardless of whether organic compound 

analysis was performed). For the analytical approach, it was 

assumed that the results for the three indicator tracers and the 

organic compound analysis should be weighted equally—that 

is, each of the fecal coliform bacteria, surfactants, boron, and 

number of organic compounds detected contributed 25 percent 

of the overall computation. Because most of these properties 

were not normally distributed, the nonparametric approach of 

ranking the data was used. For each indicator tracer and confirmatory organic tracer, the median concentration at each site 

and the median number of organic compounds detected were 

ranked from greatest to smallest. This analytical approach was 

applied first on the 52 samples that had organic compound 

analytical results (table 10) and second on the limited data set 

for all 149 sites (table 11). 

The data were ranked for the 52 sites that had at least 

one organic compound detection by assigning a value of 52 

to the greatest median value of each of the three indicator 

tracers (surfactants, fecal coliform bacteria, and boron) and 

the median number of organic compounds detected. The 

lowest tracer values were assigned a value of 1 (table 10). For 

example, site T51B had the greatest concentration of fecal 

coliform bacteria and was assigned a rank of 52; site S3, 

however, had a median concentration of fecal coliform bacteria of 16 col/100 mL and a rank of 2. After ranking all four 

tracers, the rankings for each site were summed. The sum then 

was divided by the possible total of 208 (4x52) and multiplied 

by 100 to get a relative impairment index that ranged from 0 

to 100. The greater the value of the relative impairment index, 

the more likely a given site has sewage sources relative to the 

other sampled sites. The results of this analytical approach 

are given in table 10 and are sorted in descending order by the 

value of the relative impairment index for each site. This table 

provides a key summary of all the synoptic sampling data by 

identifying the sampling sites that are most likely to contain 

minor sewage sources. Theoretically, the relative impairment 

index could be used to prioritize sites (or stream sections) for 

additional investigation to identify minor sewage sources.

The relative impairment index also was calculated for all 

149 sampling sites based only on the data from the three most 

sensitive indicator tracers (fecal coliform bacteria, boron, and 

surfactants). For this approach, the median concentration data 

for each of these three tracers were ranked by assigning the 

greatest concentration a score of 149 and the lowest concentration a score of 1 (table 11). The rankings for the three indicator tracers were summed, divided by the total possible score 

of 447 (149x3), and multiplied by 100 to develop a relative 

impairment index that ranged from 1 to 100. This approach 

differs slightly from the approach presented in table 10 in 

that the organic compound data were excluded and a relative 

impairment index value was calculated for all 149 sites. The 

results of this calculation, presented in table 11, are sorted in 

descending order by the final relative impairment index value 

for each site. Table 11 provides a summary of the sites that are 

most likely to contain sewage, and the list potentially could 

be used for prioritizing sites that may be worthy of further 

investigation. Again, caution is advised when interpreting data 

Table 10. Relative impairment indices, listed in descending order, for 52 synoptic sampling sites based on indicator tracer 

data and confirmatory organic compound data. (The theoretical addition of sewage samples appears at the bottom of the 

table.) — Continued

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters]

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number of 

organic

compound 

samples

Ranking 

for

boron

Ranking 

for

surfactants

Ranking 

for fecal 

coliform 

bacteria

Ranking

for organic

compounds

Relative 

index 

(max=100)

S46 0.087 0.25 2,400 7 8 4 52 48 47 49 94.2

T51A .022 2.50 4,800 5 10 1 26 52 50 52 86.5

T51 .025 .38 664 8 8 5 35 49 34 49 80.3

T51B .016 1.50 10,400 3 8 1 11 51 52 49 78.4

T35 .026 .13 3,500 7 7 3 38 26 48 47 76.4

S6 .027 .44 162 8 6 3 41 50 16 43 72.1

S51 .035 .13 1,233 7 3 3 47 26 43.5 33 71.9

S8 .019 .20 1,033 9 4 3 16.5 47 39.5 40 68.8

S18 .032 .13 2,000 9 2 2 46 26 46 23 67.8

S44 .058 .13 310 7 4 3 51 26 22 40 66.8

22  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Table 10. Relative impairment indices, listed in descending order, for 52 synoptic sampling sites based on indicator tracer 

data and confirmatory organic compound data. (The theoretical addition of sewage samples appears at the bottom of the 

table.) — Continued

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters]

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number of 

organic

compound 

samples

Ranking 

for

boron

Ranking 

for

surfactants

Ranking 

for fecal 

coliform 

bacteria

Ranking

for organic

compounds

Relative 

index 

(max=100)

T35A 0.014 0.13 3,700 5 9 1 8.5 26 49 51 64.7

T22 .027 .13 933 7 2.5 2 41 26 37.5 28 63.7

A15B .021 .13 1,875 3 3 1 23 26 45 33 61.1

T55 .036 .13 410 7 2 1 48 26 29.5 23 60.8

S42 .031 .13 1,200 7 1 1 45 26 42 12.5 60.3

A6 .022 .13 385 8 6.5 2 26 26 27 45.5 59.9

T23A1 .017 .13 1,033 4 6 1 13.5 26 39.5 43 58.7

T31 .027 .13 270 8 3 3 41 26 21 33 58.2

S29 .028 .13 400 9 2 3 43 26 28 23 57.7

A13 .025 .13 370 8 3 2 35 26 26 33 57.7

T23 .023 .13 320 10 4 3 29.5 26 23 40 57.0

T24 .021 .13 639 10 3 7 23 26 33 33 55.3

S41 .016 .13 1,233 7 3 1 11 26 43.5 33 54.6

A15 .026 .13 103 7 3 3 38 26 13.5 33 53.1

S20 .010 .13 933 9 6 2 4 26 37.5 43 53.1

S48 .020 .13 508 7 3 2 19.5 26 31 33 52.6

T29 .025 .13 350 5 2 1 35 26 25 23 52.4

T56 .023 .13 700 7 1.5 2 29.5 26 35 18 52.2

S7 .009 .13 1,133 9 3.5 2 3 26 41 38 51.9

S35 .051 .13 170 7 1 1 50 26 17 12.5 50.7

S50 .030 .13 100 7 2 2 44 26 12 23 50.5

T50 .022 .13 800 7 1 2 26 26 36 12.5 48.3

A16 .023 .13 177 5 2 1 29.5 26 18 23 46.4

A14 .019 .15 195 5 1 1 16.5 46 19 12.5 45.2

T25 .018 .13 235 8 3 1 15 26 20 33 45.2

T33 .023 .13 330 8 1 1 29.5 26 24 12.5 44.2

T40 .026 .13 110 7 1 1 38 26 15 12.5 44.0

S5 .013 .13 410 9 2 1 6.5 26 29.5 23 40.9

S37 .014 .12 6,400 6 1 2 8.5 6 51 12.5 37.5

T48 .024 .13 67 5 1 1 32.5 26 5 12.5 36.5

T6 .020 .13 77 5 2 1 19.5 26 7.5 23 36.5

T9 .021 .13 90 7 1 3 23 26 10 12.5 34.4

S23 .008 .13 570 7 0 1 1.5 26 32 3.5 30.3

S12 .037 .07 3 4 0 1 49 5 1 3.5 28.1

S15 .020 .13 73 7 0.5 2 19.5 26 6 7 28.1

T36 .020 .13 78 8 0 3 19.5 26 9 3.5 27.9

T13 .012 .00 59 5 6.5 2 5 2.5 4 45.5 27.4

T4 .024 .00 93 3 0 1 32.5 2.5 11 3.5 23.8

T47 .017 .13 40 5 0 1 13.5 26 3 3.5 22.1

T13A .013 .13 77 3 0 1 6.5 26 7.5 3.5 20.9

T16 .016 .00 103 3 1 1 11 2.5 13.5 12.5 19.0

S3 .008 .00 16 7 2 3 1.5 2.5 2 23 13.9

Theoretical addition of results of the sample collected below the sewer-line overflow and the six raw sewage samples that were collected

T13 0.166 5 870,000 1 13 1 53 53 53 54 98.6

Sewage .236 7.5 2,850,000 6 12 2 54 54 54 53 99.5

Identification of Sewage Sources to Accotink Creek  23
Table 11. Relative impairment indices, listed in descending order, for 149 synoptic sampling sites

based on indicator tracer data only. (The theoretical addition of sewage samples appears at the end of the 

table. — Continued

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters; nd, no data. Shading indicates relative index values for the 11 sites 

with the greatest relative impairment indices in table 10]

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number of 

organic

compound

samples

Ranking

for 

boron

Ranking

for 

surfactants

Ranking 

for fecal 

coliform 

bacteria

Relative 

index 

(max=100)

S46 0.087 0.25 2,400 7 8 4 148 144 143 97.3

T51 .025 .38 664 8 8 5 112.5 146 125 85.8

T51A .022 2.50 4,800 5 10 1 86.5 149 147 85.6

S18 .032 .13 2,000 9 2 2 132 80.5 142 79.3

S51 .035 .13 1,233 7 3 3 135.5 80.5 137.5 79.1

T24A1 .022 .25 600 5 nd nd 86.5 144 122 78.9

S6 .027 .44 162 8 6 3 123.5 147 80.5 78.5

S42 .031 .13 1,200 7 1 1 131 80.5 136 77.7

T35 .026 .13 3,500 7 7 3 118 80.5 145 76.8

T3 .030 .13 910 6 nd nd 129.5 80.5 128 75.6

T51B .016 1.50 10,400 3 8 1 40 148 149 75.4

S44 .058 .13 310 7 4 3 147 80.5 107 74.8

T22 .027 .13 933 7 2.5 2 123.5 80.5 130.5 74.8

S8 .019 .20 1,033 9 4 3 60.5 141.5 132.5 74.8

T55 .036 .13 410 7 2 1 137 80.5 116 74.6

T18 .020 .14 655 6 nd nd 69 130.5 124 72.4

S29 .028 .13 400 9 2 3 127.5 80.5 114 72.0

T31A1 .018 .19 927 4 nd nd 53 139 129 71.8

S35 .051 .13 170 7 1 1 146 80.5 85 69.7

S21 .149 .25 32 2 nd nd 149 144 17.5 69.5

T31 .027 .13 270 8 3 3 123.5 80.5 104 68.9

A13 .025 .13 370 8 3 2 112.5 80.5 111.5 68.1

T29 .025 .13 350 5 2 1 112.5 80.5 110 67.8

T56 .023 .13 700 7 1.5 2 96.5 80.5 126 67.8

T26 .026 .13 230 4 nd nd 118 80.5 100 66.8

A15B .021 .13 1,875 3 3 1 77 80.5 141 66.8

A13A .035 .13 163 2 nd nd 135.5 80.5 82 66.7

S47 .027 .13 190 6 nd nd 123.5 80.5 94 66.7

T44 .024 .13 370 7 nd nd 105 80.5 111.5 66.4

S52 .037 .13 152 8 nd nd 138.5 80.5 77 66.2

A10 .022 .15 130 1 nd nd 86.5 134.5 73.5 65.9

T50 .022 .13 800 7 1 2 86.5 80.5 127 65.8

T51C .020 .13 2,800 3 nd nd 69 80.5 144 65.7

A14 .019 .15 195 5 1 1 60.5 134.5 96.5 65.2

S36 .049 .20 3 3 nd nd 145 141.5 2 64.5

S19 .034 .13 130 5 nd nd 134 80.5 73.5 64.4

S22 .039 .13 105 8 nd nd 141.5 80.5 64 64.0

T33 .023 .13 330 8 1 1 96.5 80.5 109 64.0

T23 .023 .13 320 10 4 3 96.5 80.5 108 63.8

T24A2 .022 .13 410 5 nd nd 86.5 80.5 116 63.3

A4 .024 .14 80 4 nd nd 105 130.5 45 62.8

T24 .021 .13 639 10 3 7 77 80.5 123 62.8

A6 .022 .13 385 8 6.5 2 86.5 80.5 113 62.6

T24B1 .019 .13 1,255 4 nd nd 60.5 80.5 139 62.6

24  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Table 11. Relative impairment indices, listed in descending order, for 149 synoptic sampling sites

based on indicator tracer data only. (The theoretical addition of sewage samples appears at the end of the 

table. — Continued

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters; nd, no data. Shading indicates relative index values for the 11 sites 

with the greatest relative impairment indices in table 10]

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number of 

organic

compound

samples

Ranking

for 

boron

Ranking

for 

surfactants

Ranking 

for fecal 

coliform 

bacteria

Relative 

index 

(max=100)

A11 0.024 0.13 180 7 nd nd 105 80.5 91 61.9

S31 .023 .13 200 7 nd nd 96.5 80.5 99 61.7

A12 .025 .13 162 6 nd nd 112.5 80.5 80.5 61.2

S16 .015 .15 250 3 nd nd 33 134.5 103 60.5

S48 .020 .13 508 7 3 2 69 80.5 120 60.3

S50 .030 .13 100 7 2 2 129.5 80.5 58 60.0

A16 .023 .13 177 5 2 1 96.5 80.5 88.5 59.4

T40 .026 .13 110 7 1 1 118 80.5 65 58.9

T42 .021 .13 300 5 nd nd 77 80.5 106 58.9

T31A2 .020 .19 96 2 nd nd 69 139 53 58.4

A15 .026 .13 103 7 3 3 118 80.5 62 58.3

T23A2 .016 .13 1,571 4 nd nd 40 80.5 140 58.3

T23A1 .017 .13 1,033 4 6 1 47 80.5 132.5 58.2

A15A1 .019 .19 102 2 nd nd 60.5 139 60 58.1

A9 .022 .13 180 7 nd nd 86.5 80.5 91 57.7

S41 .016 .13 1,233 7 3 1 40 80.5 137.5 57.7

T35A .014 .13 3,700 5 9 1 28.5 80.5 146 57.0

T57 .026 .13 99 4 nd nd 118 80.5 56 56.9

A7 .022 .13 170 7 nd nd 86.5 80.5 85 56.4

T11 .022 .15 53 3 nd nd 86.5 134.5 28 55.7

T20 .024 .13 103 5 nd nd 105 80.5 62 55.4

A8 .022 .13 160 7 nd nd 86.5 80.5 78.5 54.9

A15A2 .023 .13 118 2 nd nd 96.5 80.5 68 54.8

T39 .023 .13 115 4 nd nd 96.5 80.5 66 54.4

A1 .025 .13 89 6 nd nd 112.5 80.5 49 54.1

T45 .033 .13 45 5 nd nd 133 80.5 25.5 53.5

S49 .039 .13 28 5 nd nd 141.5 80.5 16 53.2

S13 .021 .13 160 9 nd nd 77 80.5 78.5 52.8

T59 .023 .00 1,100 1 nd nd 96.5 5.5 134 52.8

T25 .018 .13 235 8 3 1 53 80.5 101 52.5

S17 .021 .13 143 6 nd nd 77 80.5 76 52.2

S45 .047 .13 7 3 nd nd 144 80.5 4 51.1

T41 .018 .13 193 5 nd nd 53 80.5 95 51.1

T10 .027 .13 39 3 nd nd 123.5 80.5 21 50.3

S7 .009 .13 1,133 9 3.5 2 9 80.5 135 50.2

S20 .010 .13 933 9 6 2 12 80.5 130.5 49.9

T32 .024 .13 70 6 nd nd 105 80.5 37 49.8

T37 .016 .13 240 7 nd nd 40 80.5 102 49.8

S5 .013 .13 410 9 2 1 24.5 80.5 116 49.4

T48 .024 .13 67 5 1 1 105 80.5 34.5 49.2

T30 .039 .10 97 1 nd nd 141.5 23 54.5 49.0

T12 .020 .13 120 6 nd nd 69 80.5 69.5 49.0

T19 .024 .13 63 7 nd nd 105 80.5 32 48.7

T27 .016 .13 195 6 nd nd 40 80.5 96.5 48.5

Identification of Sewage Sources to Accotink Creek  25
Table 11. Relative impairment indices, listed in descending order, for 149 synoptic sampling sites

based on indicator tracer data only. (The theoretical addition of sewage samples appears at the end of the 

table. — Continued

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters; nd, no data. Shading indicates relative index values for the 11 sites 

with the greatest relative impairment indices in table 10]

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number of 

organic

compound

samples

Ranking

for 

boron

Ranking

for 

surfactants

Ranking 

for fecal 

coliform 

bacteria

Relative 

index 

(max=100)

T2 0.019 0.13 133 7 nd nd 60.5 80.5 75 48.3

S32 .027 .13 20 6 nd nd 123.5 80.5 10.5 48.0

T25A .011 .13 470 5 nd nd 15 80.5 119 48.0

A5 .022 .12 197 6 nd nd 86.5 29 98 47.8

S24 .011 .13 445 8 nd nd 15 80.5 118 47.8

T52 .017 .13 170 5 nd nd 47 80.5 85 47.5

T1 .016 .13 180 7 nd nd 40 80.5 91 47.3

T46 .024 .13 42 5 nd nd 105 80.5 23.5 46.8

T9 .021 .13 90 7 1 3 77 80.5 50.5 46.5

S23 .008 .13 570 7 0 1 5.5 80.5 121 46.3

A13B .016 .13 170 1 nd nd 40 80.5 85 46.0

S37 .014 .12 6,400 6 1 2 28.5 29 148 46.0

T38 .012 .13 275 6 nd nd 19.5 80.5 105 45.9

A14A .018 .13 122 2 nd nd 53 80.5 71 45.8

T60 .015 .13 170 3 nd nd 33 80.5 85 44.4

S10 .039 .05 79 2 nd nd 141.5 11.5 44 44.1

T36 .020 .13 78 8 0 3 69 80.5 43 43.1

T43 .019 .13 90 5 nd nd 60.5 80.5 50.5 42.8

T6 .020 .13 77 5 2 1 69 80.5 41.5 42.7

S15 .020 .13 73 7 0.5 2 69 80.5 38.5 42.1

T15 .017 .13 100 3 nd nd 47 80.5 58 41.5

T21 .022 .10 120 1 nd nd 86.5 23 69.5 40.0

S28 .008 .13 182 4 nd nd 5.5 80.5 93 40.0

S39 .009 .13 177 4 nd nd 9 80.5 88.5 39.8

S14 .012 .15 42 3 nd nd 19.5 134.5 23.5 39.7

A3 .019 .13 69 6 nd nd 60.5 80.5 36 39.6

T27A .013 .13 116 2 nd nd 24.5 80.5 67 38.5

T53 .025 .10 67 5 nd nd 112.5 23 34.5 38.0

T4 .024 .00 93 3 0 1 105 5.5 52 36.4

S33 .016 .13 75 4 nd nd 40 80.5 40 35.9

S12 .037 .07 3 4 0 1 138.5 14.5 2 34.7

T8 .020 .10 100 5 nd nd 69 23 58 33.6

T47 .017 .13 40 5 0 1 47 80.5 22 33.4

S25 .028 .00 25 3 nd nd 127.5 5.5 15 33.1

T13A .013 .13 77 3 0 1 24.5 80.5 41.5 32.8

S9 .005 .15 18 3 nd nd 1.5 134.5 9 32.4

A16A1 .018 .13 10 1 nd nd 53 80.5 5 31.0

A2 .019 .12 85 6 nd nd 60.5 29 47.5 30.6

S27 .008 .13 58 4 nd nd 5.5 80.5 30 26.0

T14 .013 .13 20 3 nd nd 24.5 80.5 10.5 25.8

S2 .011 .13 37 3 nd nd 15 80.5 20 25.8

S26 .012 .10 127 3 nd nd 19.5 23 72 25.6

S38 .014 .13 3 3 nd nd 28.5 80.5 2 24.8

T16 .016 .00 103 3 1 1 40 5.5 62 24.1

26  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Table 11. Relative impairment indices, listed in descending order, for 149 synoptic sampling sites

based on indicator tracer data only. (The theoretical addition of sewage samples appears at the end of the 

table. — Continued

[mg/L, milligrams per liter; col/100 mL, colonies per 100 milliliters; nd, no data. Shading indicates relative index values for the 11 sites 

with the greatest relative impairment indices in table 10]

Site ID

(fig. 3)

Median 

boron 

(mg/L)

Median 

surfactant 

(mg/L)

Median 

fecal 

coliform 

bacteria 

(col/100 mL)

Number 

of 

samples

Median 

organic

compound 

detections

Number of 

organic

compound

samples

Ranking

for 

boron

Ranking

for 

surfactants

Ranking 

for fecal 

coliform 

bacteria

Relative 

index 

(max=100)

S30 0.021 0.07 23 2 nd nd 77 14.5 13.5 23.5

T49 .015 .10 73 3 nd nd 33 23 38.5 21.1

T54 .017 .12 32 4 nd nd 47 29 17.5 20.9

T28 .012 .12 64 2 nd nd 19.5 29 33 18.2

S43 .018 .00 35 3 nd nd 53 5.5 19 17.3

S4 .010 .08 85 4 nd nd 12 17 47.5 17.1

T34 .014 .07 54 2 nd nd 28.5 14.5 29 16.1

T5 .018 .00 22 1 nd nd 53 5.5 12 15.8

S34 .015 .10 23 4 nd nd 33 23 13.5 15.5

T7 .010 .05 83 7 nd nd 12 11.5 46 15.5

T17 .015 .00 49 3 nd nd 33 5.5 27 14.7

T58 .005 .00 97 1 nd nd 1.5 5.5 54.5 13.8

T13 .012 .00 59 5 6.5 2 19.5 5.5 31 12.5

S1 .009 .07 45 4 nd nd 9 14.5 25.5 11.0

S11 .012 .09 15 2 nd nd 19.5 18.5 6.5 10.0

S40 .007 .09 15 2 nd nd 3 18.5 6.5 6.3

S3 .008 .00 16 7 2 3 5.5 5.5 8 4.3

Theoretical addition of results of the sample collected below the sewer-line overflow and the six raw sewage samples

that were collected

T13 0.166 5.00 870,000 1 13 1 150 150 150 99.3

Sewage .236 7.50 2,850,000 6 12 2 151 151 151 100.0

from sites represented by only 1 or 2 samples, as these results 

may not be fully representative of the site.

To further evaluate the use of the relative impairment 

indices, both the data in tables 10 and 11 were evaluated 

by the theoretical addition of two sewage samples. First, 

the data from the overflowing sewer line that was located 

upstream from site T13 was added (table 5). Second, the 

median concentrations from the six sewage samples that were 

collected at the start of the study (table 2) were added and the 

matrices were recalculated. The theoretical addition of these 

samples to the databases used in tables 10 and 11 resulted in 

the sewage samples scoring the highest relative impairment 

indices of any samples (actual results are listed at the bottom 

of tables 10 and 11). 

Calculating the relative impairment index with and 

without the organic compound data provides an opportunity 

to evaluate the extent to which the organic compound data are 

important in identifying minor sewage inputs. For example, 

11 of the top 12 sites in table 10, which includes the organic 

compound data (table 10), are in the upper 11 percent of 

table 11, which does not include the organic compound data. 

This seems to indicate that similar results would have been 

reached without the organic compound analyses. This supports 

the hypothesis, however, that the three relatively inexpensive 

indicator tracers appear to be useful for identifying minor 

sewage sources to streams. Although the organic compound 

analyses are not especially critical for identifying minor 

sewage sources, they likely serve a fundamental role as a 

confirmatory tracer. Therefore, organic compound analysis 

of confirmatory tracers seems particularly valuable before 

investing in a major operation to identify or repair a potential 

sewage source.

In addition to indicating the relative likelihood that 

a given site is subject to sewage, the relative impairment 

index scores can be plotted using GIS software to scale up 

from individual sites to more of a basinwide perspective of 

possible sewage sources throughout the watershed (figs. 5, 6). 

Although several of the sites with elevated relative impairment 

indices are scattered throughout the watershed, three intriguing 

clusters appear near sites S8, T35, and T51 (fig. 5). The area 

around S8 has been of interest since the initial study site 

reconnaissance was performed and the apparent illicit septic 

Identification of Sewage Sources to Accotink Creek  27
Figure 5. Location of 52 sites in the Accotink Creek watershed of Virginia with relative impairment indices that include 

confirmatory tracer data.

28  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System

77o16'

77o18'

77o20'

38o54'

38o52'

38o50'

77o14'

77o12'

Braddock

Road

Accotink

Creek

Accotink

Creek

Crook Branch

Daniels

Run

Little River Turnpike

Lee Highway

Fairfax

FAIRFAX CO

495

Long

Branch

Bear

Branch

Hunter

Run

Nutley Street

Chain

Bridge

Road

66

0 1

0 1

2 MILES

2 KILOMETERS

01654000

72.2–94.2

64.8–72.1

60.0–64.7

50.1–59.9

13.9–50.0

01654000 EXPLANATION

U.S. Geological Survey streamgaging

station and number

Figure 5. Location of 52 sites in the Accotink Creek watershed of Virginia with relative impairment indices that include

confirmatory tracer data.

RELATIVE IMPAIRMENT INDICES

Arlington Boulevard

Base from digital files:

Drainage basin from U.S. Geological Survey Open-File Report 2006-1308

U.S. Geological Survey, digital line graph hydrography 1:24,000

County boundaries from TIGER files; 1:100,000; 1994

Virginia State Plane projection, North zone, units feet, NAD 83, central meridian 7830’W
Figure 6. Location of 149 sites in the Accotink Creek watershed of Virginia with relative impairment indices that include only 

indicator tracer data.

Identification of Sewage Sources to Accotink Creek  29

77o16'

77o18'

77o20'

38o54'

38o52'

38o50'

77o14'

77o12'

Braddock

Road

Accotink

Creek

Accotink

Creek

Crook Branch

Daniels

Run

Little River Turnpike

Lee Highway

Fairfax

FAIRFAX CO

495

Long

Branch

Bear

Branch

Hunter

Run

Nutley Street

Chain

Bridge

Road

66

0 1

0 1

2 MILES

2 KILOMETERS

01654000

75.5–97.3

69.0–75.4

55.8–68.9

50.1–55.7

4.3–50.0

01654000 EXPLANATION

U.S. Geological Survey streamgaging

station and number

Figure 6. Location of 149 sites in the Accotink Creek watershed of Virginia with relative impairment indices that include only

indicator tracer data.

RELATIVE IMPAIRMENT INDICES

Arlington Boulevard

Base from digital files:

Drainage basin from U.S. Geological Survey Open-File Report 2006-1308

U.S. Geological Survey, digital line graph hydrography 1:24,000

County boundaries from TIGER files; 1:100,000; 1994

Virginia State Plane projection, North zone, units feet, NAD 83, central meridian 7830’W
dumping was identified at site S7. The data indicate that both 

sites S6 and S8 may have minor sewage contributions to the 

streams. No further investigation has been done at these sites 

to confirm or deny this possibility. Near the end of the study, 

when focus was on the stretch of tributary between sites T35 

and T35A, it was discovered that at least one lateral sewer 

line that runs from an adjacent condominium complex to the 

primary sewer line had failed. Although it is uncertain whether 

this was the only source of sewage to this section of tributary, 

it was a definitive source of sewage that was discontinued. The 

repair of the lateral line was accomplished after all sampling 

for this study had been completed. Although the area around 

site T51 has been repeatedly investigated by Fairfax City, no 

sewage sources to the stream have been identified despite 

the one major sewage contribution to the tributary that was 

identified at site T51BLD. Based on the relatively elevated 

impairment indices associated with the sampling sites along 

this stretch of tributary, it is hypothesized that there is likely 

a source of sewage somewhere upgradient from these sites, 

although the source remains undiscovered.

One of the more challenging aspects in identifying 

minor sewage sources is that the water quality at individual 

sampling sites was far more variable than initially expected, 

especially given that all the samples were collected under 

base-flow conditions. Consequently, it is meaningful to 

describe the variability in the tracer concentrations at each site, 

in addition to the median concentrations that are presented in 

table 9. To characterize this variability, the median absolute 

deviation (MAD) was used (Helsel and Hirsch, 2002) rather 

than a standard deviation calculation. The strength of the 

MAD calculation is that it is stable in the presence of outliers, 

whereas the standard deviation term is unstable and generally 

inflated. Outliers or extreme values result in a measure of 

variability that is greater than what actually is indicated by 

the data, because the standard deviation calculation relies on a 

comparison to the sample mean, which is strongly influenced 

by outliers (Helsel and Hirsch, 2002).

The MAD is calculated by first determining the absolute 

difference between each observed tracer concentration and the 

median tracer concentration for a given site. Next, the MAD is 

determined as the median of these absolute differences. Conceptually, this is best demonstrated by example. If five samples 

from a given site were analyzed for fecal coliform bacterial 

concentrations and the results were 3, 10, 60, 100, and 

900 col/100 mL, the standard deviation would be 385, which 

is largely inflated by the 900 col/100 mL value even though 

most of the samples had relatively low concentrations of fecal 

coliform bacteria. In this example, the median concentration of 

fecal coliform bacteria is 60, and the absolute deviations from 

this median are 57, 50, 0, 40, and 840. The median of these 

deviations (MAD) is 50, which more reasonably represents 

the variability in this data set. The MAD was calculated for 

141 sampling sites for which enough data were available to 

perform this calculation; only one water sample was collected 

at 9 sampling sites, and the MAD could not be calculated 

for these sites. Results of the MAD calculations performed 

on indicator tracer data from the 141 sites are presented in 

table 12. In addition to the calculation of the MAD for each 

constituent at each site, a ranking and summation routine 

similar to the protocol used in table 11 was used to summarize 

the data and quantify the sites that were most variable. For 

each indicator tracer, the MAD values were ranked from least 

to greatest and scored from 1 to 141. After ranking all three 

of the sensitive indicator tracers, the rankings for a given site 

were summed, divided by the total maximum score of 423 

(141x3), and multiplied by 100. This value provides a relative 

variability index for each study site represented by at least two 

water-quality samples. Sites with greater relative variability 

indices had more variable sample compositions than sites 

that were very consistent and had lower relative indices. To 

provide a point of reference, the MAD for each indicator 

tracer was calculated for the entire data set and used to apply 

conditional formatting. Although the use of these MAD values 

for the entire data set is arbitrary, it provides a mechanism 

for indicating the sites and indicator tracers that demonstrate 

relatively more variability.

This summary of water-quality variability for each tracer 

and each site is complementary to the median tracer concentrations that were observed at each sampling site (presented 

in tables 10 and 11). By summarizing the variability, both the 

median concentrations and the variability of the data around 

the median can be investigated. Not surprisingly, many of the 

sites with relatively large impairment indices also had relatively elevated variability indices. This indicates that although 

the sites with elevated relative impairment scores may be 

subject to sewage sources, the sites are also highly variable 

and the tracer concentrations are not always elevated. This 

also may indicate that many of the minor sewage sources in 

the watershed are transitory or otherwise short lived. Consequently, the use of only quarterly grab samples (as occurred 

in this study) may not be the best approach for identifying 

locations of varying sewage sources; therefore, several other 

methods for locating minor sewage sources were investigated 

near the end of the study. 

30 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Table 12. Median absolute deviation (MAD) values for the synoptic sampling sites and 

conditional formatting of the MAD scores to identify the sites with the greatest variability in 

tracer concentrations. — Continued

[MAD, median absolute deviation; red values indicate boron greater than 0.007, surfactants greater than

0.02, and fecal coliform bacteria greater than 157.5; nd, no data. MAD scores were ranked from greatest to

smallest for each tracer, and the ranks were used to calculate a relative variability index for each site. Sites are 

sorted according to their final relative variability index; sites with higher indices had more variable tracer

concentrations between sampling events]

Site ID

(fig. 3)

Boron 

MAD

Surfactant 

MAD

Fecal 

coliform 

bacteria

MAD

Number 

of 

samples

Ranking 

for boron

MAD

Ranking 

for 

surfactant 

MAD

Ranking 

for fecal 

coliform 

bacteria

MAD

Relative 

index 

(max=100)

S46 0.052 0.12 2,393 7 141 132.5 137 97.0

T51A .007 .50 4,790 5 113.5 140 139 92.8

T51 .009 .25 495 8 128.5 139 120 91.6

S8 .009 .07 1,025 9 128.5 124.5 132 91.0

S6 .013 .13 153 8 135 137.5 93 86.4

S19 .023 .13 127 5 138.5 137.5 89 86.3

T3 .007 .04 806 6 113.5 110.5 125 82.5

T56 .005 .12 555 7 93.5 132.5 123 82.5

S37 .004 .12 5,209 6 75.5 132.5 140 82.3

S17 .011 .04 133 6 133.5 110.5 91 79.2

T35 .005 .03 1,400 7 93.5 99.5 134.5 77.4

S22 .007 .08 101 8 113.5 128 84.5 77.1

S42 .007 .02 1,000 7 113.5 82 130 77.0

T22 .004 .12 367 7 75.5 132.5 112 75.7

T51B .002 1.25 10,335 3 36 141 141 75.2

T23 .007 .03 225 10 113.5 99.5 101 74.2

A15 .006 .12 74 7 103.5 132.5 73 73.1

T18 .007 .01 520 6 113.5 70.5 122 72.3

T23A1 .003 .06 384 4 55.5 119 113 68.0

S4 .005 .05 79 4 93.5 114.5 74.5 66.8

S18 .004 .01 1,500 9 75.5 70.5 136 66.7

S29 .010 .00 393 9 131.5 34 115 66.3

T7 .005 .05 73 7 93.5 114.5 71.5 66.1

T31A1 .002 .06 592 4 36 119 124 66.0

T24 .008 .00 444 10 123.5 34 119 65.4

A7 .007 .03 57 7 113.5 99.5 61.5 64.9

S31 .004 .03 191 7 75.5 99.5 98 64.5

S44 .011 .00 240 7 133.5 34 102 63.7

S35 .023 .00 160 7 138.5 34 94 63.0

A5 .008 .02 54 6 123.5 82 60 62.8

T40 .007 .02 72 7 113.5 82 69.5 62.6

S48 .007 .00 431 7 113.5 34 117 62.5

T29 .003 .03 332 5 55.5 99.5 109 62.4

A4 .009 .03 25 4 128.5 99.5 33 61.7

S52 .024 .00 113 8 140 34 87 61.7

S23 .001 .12 330 7 16.5 132.5 107.5 60.6

S49 .008 .03 25 5 123.5 99.5 33 60.5

T33 .007 .00 325 8 113.5 34 106 59.9

S50 .015 .00 95 7 136 34 81.5 59.5

T53 .008 .03 15 5 123.5 99.5 22.5 58.0

S30 .005 .07 18 2 93.5 124.5 26 57.7

A9 .006 .02 50 7 103.5 82 57.5 57.4

Identification of Sewage Sources to Accotink Creek  31
Table 12. Median absolute deviation (MAD) values for the synoptic sampling sites and 

conditional formatting of the MAD scores to identify the sites with the greatest variability in 

tracer concentrations. — Continued

[MAD, median absolute deviation; red values indicate boron greater than 0.007, surfactants greater than

0.02, and fecal coliform bacteria greater than 157.5; nd, no data. MAD scores were ranked from greatest to

smallest for each tracer, and the ranks were used to calculate a relative variability index for each site. Sites are 

sorted according to their final relative variability index; sites with higher indices had more variable tracer

concentrations between sampling events]

Site ID

(fig. 3)

Boron 

MAD

Surfactant 

MAD

Fecal 

coliform 

bacteria

MAD

Number 

of 

samples

Ranking 

for boron

MAD

Ranking 

for 

surfactant 

MAD

Ranking 

for fecal 

coliform 

bacteria

MAD

Relative 

index 

(max=100)

S47 0.007 0.00 169 6 113.5 34 95 57.3

T42 .003 .02 255 5 55.5 82 103 56.9

T9 .004 .03 64 7 75.5 99.5 65.5 56.9

S20 .004 .00 930 9 75.5 34 129 56.4

S10 .005 .05 22 2 93.5 114.5 28 55.8

T8 .005 .03 32 5 93.5 99.5 41 55.3

S5 .002 .03 174 9 36 99.5 97 55.0

T57 .004 .07 24 4 75.5 124.5 30.5 54.5

A6 .003 .01 280 8 55.5 70.5 104 54.4

S45 .008 .03 4 3 123.5 99.5 7 54.4

T35A .003 .00 2,633 5 55.5 34 138 53.8

T1 .002 .12 50 7 36 132.5 57.5 53.4

T20 .004 .02 64 5 75.5 82 65.5 52.7

S41 .003 .00 1,140 7 55.5 34 133 52.6

T45 .004 .03 38 5 75.5 99.5 46 52.2

T24A2 .004 .00 343 5 75.5 34 111 52.1

T24B1 .003 .00 1,024 4 55.5 34 131 52.1

S32 .007 .02 17 6 113.5 82 24.5 52.0

T2 .002 .03 101 7 36 99.5 84.5 52.0

T55 .004 .00 337 7 75.5 34 110 51.9

T6 .008 .02 7 5 123.5 82 13 51.7

S28 .001 .06 95 4 16.5 119 81.5 51.3

S51 .003 .00 893 7 55.5 34 127 51.2

T39 .006 .01 32 4 103.5 70.5 41 50.8

S24 .004 .00 320 8 75.5 34 105 50.7

A16 .003 .03 53 5 55.5 99.5 59 50.6

T12 .005 .00 97 6 93.5 34 83 49.8

T24A1 .003 .00 503 5 55.5 34 121 49.8

A3 .006 .01 27 6 103.5 70.5 36 49.6

T38 .004 .00 205 6 75.5 34 100 49.5

A13 .004 .00 172 8 75.5 34 96 48.6

T23A2 .003 .00 417 4 55.5 34 116 48.6

T10 .007 .02 4 3 113.5 82 7 47.9

T31A2 .000 .06 93 2 4 119 79 47.8

A1 .003 .03 35 6 55.5 99.5 44.5 47.2

S13 .004 .00 132 9 75.5 34 90 47.2

A15B .002 .00 925 3 36 34 128 46.8

T31 .004 .00 124 8 75.5 34 88 46.7

T4 .005 .00 72 3 93.5 34 69.5 46.6

S7 .002 .00 867 9 36 34 126 46.3

T16 .004 .00 93 3 75.5 34 79 44.6

S16 .004 .00 90 3 75.5 34 77 44.1

32  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Table 12. Median absolute deviation (MAD) values for the synoptic sampling sites and 

conditional formatting of the MAD scores to identify the sites with the greatest variability in 

tracer concentrations. — Continued

[MAD, median absolute deviation; red values indicate boron greater than 0.007, surfactants greater than

0.02, and fecal coliform bacteria greater than 157.5; nd, no data. MAD scores were ranked from greatest to

smallest for each tracer, and the ranks were used to calculate a relative variability index for each site. Sites are 

sorted according to their final relative variability index; sites with higher indices had more variable tracer

concentrations between sampling events]

Site ID

(fig. 3)

Boron 

MAD

Surfactant 

MAD

Fecal 

coliform 

bacteria

MAD

Number 

of 

samples

Ranking 

for boron

MAD

Ranking 

for 

surfactant 

MAD

Ranking 

for fecal 

coliform 

bacteria

MAD

Relative 

index 

(max=100)

A8 0.007 0.00 30 7 113.5 34 38.5 44.0

S26 .003 .03 24 3 55.5 99.5 30.5 43.9

A14 .002 .02 65 5 36 82 67 43.7

S12 .003 .07 0 4 55.5 124.5 2 43.0

T26 .002 .02 59 4 36 82 63 42.8

T48 .005 .00 44 5 93.5 34 52 42.4

A11 .005 .00 40 7 93.5 34 50 42.0

T15 .001 .02 93 3 16.5 82 79 42.0

T34 .001 .07 26 2 16.5 124.5 35 41.6

A13A .020 .00 1 2 137 34 4 41.4

S15 .004 .00 63 7 75.5 34 64 41.0

T51C .000 .00 1,400 3 4 34 134.5 40.8

A2 .002 .02 44 6 36 82 52 40.2

S21 .009 .00 4 2 128.5 34 7 40.1

T37 .002 .00 204 7 36 34 99 40.0

T50 .001 .00 433 7 16.5 34 118 39.8

S36 .010 .00 0 3 131.5 34 2 39.6

T47 .005 .00 30 5 93.5 34 38.5 39.2

T25A .001 .00 390 5 16.5 34 114 38.9

T46 .006 .00 19 5 103.5 34 27 38.9

T36 .004 .00 45 8 75.5 34 54 38.7

T27 .002 .00 134 6 36 34 92 38.3

T25 .004 .00 44 8 75.5 34 52 38.2

A15A2 .003 .00 73 2 55.5 34 71.5 38.1

S25 .006 .00 15 3 103.5 34 22.5 37.8

T28 .001 .02 57 2 16.5 82 61.5 37.8

S11 .002 .04 7 2 36 110.5 13 37.7

T14 .001 .12 5 3 16.5 132.5 9.5 37.5

T44 .001 .00 330 7 16.5 34 107.5 37.4

A12 .004 .00 39 6 75.5 34 48 37.2

T41 .003 .00 66 5 55.5 34 68 37.2

S1 .001 .07 10 4 16.5 124.5 16 37.1

A15A1 .001 .06 9 2 16.5 119 15 35.6

S2 .002 .03 7 3 36 99.5 13 35.1

S34 .005 .00 14 4 93.5 34 21 35.1

T13A .003 .00 46 3 55.5 34 55 34.2

T19 .001 .02 33 7 16.5 82 43 33.5

T11 .005 .00 6 3 93.5 34 11 32.7

T27A .001 .00 104 2 16.5 34 86 32.3

S9 .001 .05 3 3 16.5 114.5 5 32.2

S40 .000 .04 12 2 4 110.5 18 31.3

T54 .002 .02 5 4 36 82 9.5 30.1

Identification of Sewage Sources to Accotink Creek  33
Table 12. Median absolute deviation (MAD) values for the synoptic sampling sites and 

conditional formatting of the MAD scores to identify the sites with the greatest variability in 

tracer concentrations. — Continued

[MAD, median absolute deviation; red values indicate boron greater than 0.007, surfactants greater than

0.02, and fecal coliform bacteria greater than 157.5; nd, no data. MAD scores were ranked from greatest to

smallest for each tracer, and the ranks were used to calculate a relative variability index for each site. Sites are 

sorted according to their final relative variability index; sites with higher indices had more variable tracer

concentrations between sampling events]

Site ID

(fig. 3)

Boron 

MAD

Surfactant 

MAD

Fecal 

coliform 

bacteria

MAD

Number 

of 

samples

Ranking 

for boron

MAD

Ranking 

for 

surfactant 

MAD

Ranking 

for fecal 

coliform 

bacteria

MAD

Relative 

index 

(max=100)

T13 0.003 0.00 28 5 55.5 34 37 29.9

T43 .001 .00 83 5 16.5 34 76 29.9

S27 .002 .00 49 4 36 34 56 29.8

S39 .001 .00 79 4 16.5 34 74.5 29.6

S38 .002 .02 0 3 36 82 2 28.4

T52 .000 .01 35 5 4 70.5 44.5 28.1

S33 .002 .00 39 4 36 34 48 27.9

T32 .002 .00 39 6 36 34 48 27.9

A14A .002 .00 25 2 36 34 33 24.4

S43 .001 .00 32 3 16.5 34 41 21.6

S3 .002 .00 11 7 36 34 17 20.6

T60 .001 .00 13 3 16.5 34 19.5 16.5

T49 .000 .00 23 3 4 34 29 15.8

T17 .000 .00 17 3 4 34 24.5 14.8

S14 .000 .00 13 3 4 34 19.5 13.6

A10 nd nd nd 1 nd nd nd nd

A13B nd nd nd 1 nd nd nd nd

A16A1 nd nd nd 1 nd nd nd nd

T21 nd nd nd 1 nd nd nd nd

T30 nd nd nd 1 nd nd nd nd

T5 nd nd nd 1 nd nd nd nd

T51BLD nd nd nd 1 nd nd nd nd

T58 nd nd nd 1 nd nd nd nd

T59 nd nd nd 1 nd nd nd nd

Additional Sampling 

Three additional types of sampling were performed as 

part of the final sampling event to better understand the variability in water quality at a given site and to further evaluate 

minor sewage sources to Accotink Creek. These additional 

sampling techniques included optical brightener monitoring, 

intensive stream sampling over a 24-hour period, and detailed 

sampling of several storm-drain networks. 

Optical Brightener Monitoring

The optical brightener monitoring was performed at 

approximately 60 of the synoptic sampling sites that had either 

highly variable conditions or conditions that seemed indicative 

of sewage contamination. After the samplers were deployed, 

they were left in place for approximately 3 days. By the third 

day, several of the samplers were missing altogether or, in 

several cases, the cotton swatches were missing (often with the 

retaining rubber bands lying nearby). In many cases where the 

sampler or cotton swatch were missing, fresh wildlife tracks 

(predominantly raccoon) were observed in the vicinity of the 

sampler. In total, nine of the optical brightener samples were 

lost during deployment (S18, T24A2, S50, S48, S51, A15B, 

T37, S24, and T42). 

The remaining optical brightener samples were 

transported to the laboratory, rinsed, and interpreted in a dark 

room; strongly positive results were obtained for sites T35, 

34  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
T35A, S7, and S8 (fig. 3). Ambiguous results were obtained 

for site T33, and all other samples were negative. Results 

were confirmed by two other independent analysts. The 

optical brightener results are most readily interpreted in the 

context of the relative impairment indices that are presented in 

table 10. Sites T35, T35A, and S8 are among the first 12 sites 

listed, supporting the notion that these sites are influenced by 

sewage. Site S7 appears farther down on table 10 (number 

29), which indicates that this site is influenced less by sewage; 

however, it was site S7 that had the apparent illicit septic-tank 

dumping that was observed during watershed reconnaissance. 

Interestingly, none of the sites around site T51 had positive 

results for optical brighteners. This seems to indicate that the 

sewage source near site T51 (and even the raw sewage at site 

T51BLD) did not contain laundry detergents, and the sewage 

in this tributary was from a source that was free of optical 

brighteners—possibly a nearby business or office complex.

Although these analyses seem fairly useful, they are 

likely more so when used in conjunction with other methods 

to support the inferences that are drawn. For example, a 

negative optical brightener result does not confirm the absence 

of sewage, because the sewage source may not contain laundry 

detergent (likely the case with the sites around T51). Similarly, 

a positive result is strongly indicative of sewage, although 

some humic and fulvic acids fluoresce under an ultraviolet 

light and may cause a false-positive reading. Overall, the 

optical brightener monitoring further indicated the presence of 

sewage at sites T35, T35A, and S8, as well as possible sewage 

at site S7. 

Intensive Stream Sampling Using Automated 

Samplers

Intensive sampling of several synoptic sampling sites was 

performed to document the possible water-quality variability 

that can occur at some of the sites. These intensive samples 

were collected using an automated sampler programmed to 

sample hourly over approximately a 24-hour period. These 

samples provide a level of time integration and much more 

detailed information than the grab samples, which essentially 

represent a “snap shot” in time.

All intensive sampling was conducted in conjunction 

with the eighth sampling event. The automated sampler was 

deployed for approximately 24 hours, the samples were 

retrieved and analyzed, the bottles were cleaned, and the 

automated sampler was re-deployed at another sampling site. 

Using this approach, sites T35 and T51 were sampled first, 

sites A15 and T23 were sampled next, and sites S8 and S7 

were sampled thereafter. Unfortunately, the samples from sites 

A15 and T23 were affected by rainfall soon after the samplers 

were deployed, and these samples did not represent variability 

under base-flow conditions. The remaining four sites were 

successfully sampled under base-flow conditions, and the data 

from these four sites (T35, T51, S7, and S8) were interpreted 

(figs. 7–10). 

Little interpretable variability in the water-quality data 

was observed during sampling at sites T35 and S7 (figs. 7, 8), 

although boron concentrations varied at both sites, indicating 

that the timing of sample collection at these sites could be 

important. The water-quality data at sites T51 and S8 were 

considerably variable (figs. 9, 10), and the variable patterns 

may be indicative of sewage sources. The data from site S8 

(fig. 10) illustrate a rapid increase in surfactants, turbidity, and 

specific conductance with the sixth sample, while boron has a 

slightly later increase in concentration that actually may represent a separate input rather than a delayed input. After several 

hours, tracer concentrations at site S8 eventually returned to 

initial concentrations. Similarly, site T51 had a pronounced 

increase in surfactants, turbidity, specific conductance, and 

boron (fig. 9). The results from this intensive sampling of 

sites T51 and S8 indicate highly variable tracer concentrations 

depending on the time of day, and this variability likely has 

caused some of the variability in the synoptic sampling data. 

In addition, the intensive data from sites T51 and S8 may be 

indicative of short-lived sewage sources, rather than a steady 

sewage source. A variable-rate sewage source is more difficult 

to identify, and synoptic sampling may or may not identify the 

input depending on the time that the sample is collected. 

Identification of Sewage Sources to Accotink Creek  35
Figure 7. Intensive automated water-quality sampling data collected during September 2004 from siteT35 

in the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from 

all eight sampling events) is plotted as a horizontal dashed line.)

36  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System

0

0.02

0.04

0.06

0.08

0.10

0.12

0.14

SURFACTANTS, IN MILLIGRAMS PER LITER 

0

0.5

1.0

1.5

2.0

2.5

TURBIDITY, IN NEPHELOMETRIC 

TURBIDITY UNITS 

Surfactants

Median surfactants 

Turbidity

Median turbidity 

0

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0 5 10 15 20 25

SAMPLE NUMBER 

BORON, IN MILLIGRAMS PER LITER 

295

300

305

310

315

320

325

330

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS

Boron

Median boron 

Specific conductance 

Median specific conductance 

Figure 7. Intensive automated water-quality sampling data collected during September 2004 from site T35

in the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from

all eight sampling events) is plotted as a horizontal dashed line on each plot.)
Figure 8. Intensive automated water-quality sampling data collected during September 2004 from site S7 in 

the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from all eight 

sampling events) is plotted as a horizontal dashed line.)

Identification of Sewage Sources to Accotink Creek  37

0

0.05

0.10

0.15

0.20

0.25

0.30

0

1

2

3

4

5

6

7

8

0

0.005

0.010

0.015

0.020

0.025

0.030

0.035

252

254

256

258

260

262

264

266

268

270

272

Surfactants

Median surfactants 

Turbidity

Median turbidity 

Boron

Median boron 

Specific conductance 

Median specific conductance 

SURFACTANTS, IN MILLIGRAMS PER LITER 

0 5 10 15 20 25 30

SAMPLE NUMBER 

BORON, IN MILLIGRAMS PER LITER 

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS 

TURBIDITY, IN NEPHELOMETRIC 

TURBIDITY UNITS 

Figure 8. Intensive automated water-quality sampling data collected during September 2004 from site S7

in the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from

all eight sampling events) is plotted as a horizontal dashed line on each plot.)
Figure 9. Intensive automated water-quality sampling data collected during September 2004 from site T51 in 

the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from all eight 

sampling events) is plotted as a horizontal dashed line.)

38  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System SURFACTANTS, IN MILLIGRAMS PER LITER 

Surfactants

Median surfactants 

Turbidity

Median turbidity 

0 5 10 15 20 25

SAMPLE NUMBER 

BORON, IN MILLIGRAMS PER LITER 

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS 

Boron

Median boron 

Specific conductance 

Median specific conductance 

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0

1

2

3

4

5

6

7

0

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

350

360

370

380

390

400

410

420

TURBIDITY, IN NEPHELOMETRIC 

TURBIDITY UNITS 

Figure 9. Intensive automated water-quality sampling data collected during September 2004 from site T51

in the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from

all eight sampling events) is plotted as a horizontal dashed line on each plot.)
Figure 10. Intensive automated water-quality sampling data collected during September 2004 from site S8 in 

the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from all eight 

sampling events) is plotted as a horizontal dashed line.)

Identification of Sewage Sources to Accotink Creek  39

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

310

315

320

325

330

335

Surfactants

Median surfactants 

Turbidity

Median turbidity 

Boron

Median boron 

Specific conductance 

Median specific conductance 

SURFACTANTS, IN MILLIGRAMS PER LITER 

0 5 10 15 20 25 30

SAMPLE NUMBER 

BORON, IN MILLIGRAMS PER LITER 

SPECIFIC CONDUCTANCE, IN

MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS 

TURBIDITY, IN NEPHELOMETRIC 

TURBIDITY UNITS 

Figure 10. Intensive automated water-quality sampling data collected during September 2004 from site S8

in the Accotink Creek watershed, Virginia. (For reference, the median concentration of each tracer (from

all eight sampling events) is plotted as a horizontal dashed line on each plot.)
Additional Sampling of Storm-Drain Networks

Shortly after the eighth sampling event, further sampling 

of the storm-drain networks associated with sites S18, S20, 

S29, and S37 was conducted to characterize the sources of 

water that contributed to each of the storm-drain outfalls. 

These storm drains were selected for additional sampling 

based on relatively elevated concentrations of fecal coliform 

bacteria, surfactants, and(or) boron, which indicated the 

possible presence of sewage. In each storm-drain network, 

between three and eight water-quality samples were collected 

depending on the hydrology, size, and complexity of the 

storm-drain network. 

Site S18 had two primary network branches that were 

flowing during sampling (fig. 11). The outfall (site S18) had 

slightly elevated concentrations of fecal coliform bacteria and 

boron but rather low concentrations of surfactants (table 13); 

this pattern is consistent with the results of the previous 

sampling at this site. Although the conditions observed during 

this sampling were not particularly indicative of sewage, the 

elevated concentrations of bacteria and boron could indicate 

some sewage contributions. The storm-drain sampling indicated relatively low surfactant concentrations throughout the 

network and relatively elevated boron concentrations in much 

of the network. Elevated concentrations of fecal coliform 

bacteria were observed in only one storm drain—the drain 

that originates upstream from site S18F, routes flow down to 

site S18C, and then to the storm-drain outfall (site S18). It is 

likely that this one line (S18F) is primarily responsible for the 

elevated concentrations of fecal coliform bacteria observed at 

site S18. 

Site S20 is a relatively complex storm-drain network 

(fig. 12), but sampling the network was relatively simple 

because only one branch of the network had flow and the 

remainder of the network did not. In addition to the stormdrain outfall, two samples were collected near the upgradient 

end of the flowing line. Overall, the tracer concentrations at 

the outfall (site S20) were relatively low on the day of the 

sampling with the exception of the concentrations of fecal 

coliform bacteria, which were relatively elevated (table 13). 

The surfactant and boron concentrations indicate that this 

outfall likely did not contain sewage on the day that sampling 

was conducted. The upstream sampling sites (S20A and S20B) 

had relatively different water-quality properties, however. Site 

S20A had elevated concentrations of fecal coliform bacteria, 

surfactants, and turbidity but relatively low concentrations 

of boron. While it is unclear whether the composition of the 

water observed at site S20A was influenced by sewage, the 

source of the flow at S20A may justify additional investigation. Alternatively, site S20B had low concentrations of 

fecal coliform bacteria, surfactants, and turbidity but slightly 

elevated boron concentrations. Additionally, while sampling 

this storm-drain network, a white discharge was observed 

occasionally in the flow from site S20B. The whitish flow 

occurred as a short-lived pulse that only lasted about 30 seconds at a time before flow conditions returned to the typical 

clear conditions. The source of this whitish discharge was not 

determined.

During earlier sampling events, the water-quality composition of the storm-drain outfall at site S29 was highly variable 

with respect to concentrations of fecal coliform bacteria, 

surfactants, and boron. On the day of the storm-drain network 

sampling at site S29 (fig. 13), the composition of the water 

was slightly elevated with respect to concentrations of boron 

and fecal coliform bacteria but not surfactants (table 13). 

Although the conditions observed during this sampling were 

not particularly indicative of sewage, the elevated concentrations of bacteria and boron could indicate some sewage 

sources. Most of the flow on the sampling day was identified 

to be coming from site S29A, and the chemical composition 

of water samples from sites S29A and S29 were very similar. 

Samples collected from flow in another arm of the network 

indicated that the concentrations of fecal coliform bacteria and 

surfactants were relatively low. One interesting observation 

while sampling the flow at site S29D was the relatively warm 

temperature (35 °C); in addition, site S29D had the highest 

concentrations of fecal coliform bacteria of all the sites in this 

storm-drain network. The source of the warm water was not 

located. 

The final storm-drain network that was sampled was 

site S37 (fig. 14), most of which underlies the Oakton High 

School complex. This site is characterized by strongly 

elevated concentrations of fecal coliform bacteria (median of 

6,400 col/100 mL, table 9) but typically low surfactant and 

boron concentrations. Several organic compound samples 

indicated a very low number of detections (typically only 

one compound was detected), indicating that this storm 

drain likely was a source of elevated concentrations of fecal 

coliform bacteria but not sewage. During sampling, a strong 

chloride odor was detected; network reconnaissance identified 

the source, which was a bleach and water solution that was 

being used to clean an ice maker in the athletic field concession stand. Through additional investigation, it was deduced 

that the sink drains from the concession stand were plumbed 

directly into the storm-drain system and not into a sewer line. 

Upon learning of this, the school administrators stopped using 

these drains. As beneficial as it was to identify this improperly 

connected drain line, the use of the bleach cleaning solution 

appears to have reduced the bacteria concentrations in the 

storm-drain network to the lowest ever observed at this site. 

Although the use of bleach in this storm-drain network may 

have reduced fecal coliform concentrations, all the tracer 

concentrations were rather low in the network samples, even in 

the sample from site S37F, which is located above the bleachaffected storm drain (table 13). Overall, it seems reasonable to 

conclude that this site is a source of elevated concentrations of 

fecal coliform bacteria but not sewage.

Cumulatively, the additional analyses that were performed near the end of the study offered several mechanisms 

for understanding the potential for minor sewage sources and 

the variability that was observed among the sampling sites. 

Although the synoptic grab sampling offered the best way 

40 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Figure 11. Generalized map of the storm-drain network sampling locations for site S18 (fig. 3). (Roads, tax parcels, and 

building footprints have been added to better identify the location of the sampling sites.)

Identification of Sewage Sources to Accotink Creek  41

S18

S18G

S18F

S18C

S18A

S18D

S18B

S18E

Arlington Boulevard

Prosperity Avenue

EXPLANATION

BUILDING FOOTPRINT

TAX PARCEL

STORM SEWER

SANITARY SEWER

STREAM

SAMPLING SITE S18F

NOT TO SCALE

Figure 11. Generalized map of the storm-drain network sampling locations for site S18 (fig. 3). (Roads, tax parcels, and building

footprints have been added to better identify the location of the sampling sites.)
Table 13. Indicator tracer data from the storm-drain network sampling at sites S20, S18, S29, and S37 in the

Accotink Creek watershed, Virginia.

[mg/L, milligrams per liter; oC, degrees Celsius; mS/cm, microsiemens per centimeter at 25 degrees Celsius; NTU, nephelometric turbidity units; 

col/100 mL, colonies per 100 milliliters; ft3/s, cubic feet per second; —, not determined; <, less than. Shading indicates estimated

concentration value]

Site 

ID

(figs. 

11–14)

Sampling 

date

Sampling 

time

Boron 

(mg/L)

Chloride 

(mg/L)

Water 

temperature

(oC)

Specific 

conductance 

(mS/cm)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTU)

Surfactants 

(mg/L)

Fecal 

coliform 

bacteria 

(col/

100 mL)

Discharge 

(ft3/s)

S20 9/23/04 1045 0.010 20 — 169 — 11 0.13 2,700 0.0280

S20A 9/23/04 1130 .012 20 20.0 181 — 32 .25 1,933 .0001

S20B 9/23/04 1135 .032 18 — 215 — 2 .13 43 .0000

S18 9/23/04 1205 .039 96 19.0 263 7.1 1 .13 480 .0290

S18A 9/23/04 1215 < .007 141 — 585 — 0 .13 < 10 —

S18B 9/23/04 1230 .010 < 1 — 63 — 2 .13 290 .0060

S18D 9/23/04 1255 .059 85 — 390 — 1 .13 69 .0010

S18C 9/23/04 1245 .075 43 — 404 — 1 .13 1,133 .0020

S18E 9/23/04 1330 .065 < 1 — 69 — 2 .13 < 3 .0001

S18F 9/23/04 1355 .075 50 — 291 — 2 0 1,333 .0002

S18G 9/23/04 1354 .487 < 1 — 108 9.0 1 0 < 3 .0002

S29 9/23/04 1425 .045 49 21.7 285 7.8 2 .13 440 .2070

S29A 9/23/04 1445 .048 62 21.3 208 8.9 3 .13 380 .0118

S29B 9/23/04 1530 — — — — — 3 .25 < 3 —

S29C 9/23/04 1635 .039 28 29.6 68.5 6.3 1 .13 44 .0118

S29D 9/23/04 1650 .030 17 35.0 199 — 2 .13 500 .0118

S37 9/24/04 950 .013 7 19.5 149 — 6 0 460 .0320

S37A 9/24/04 1010 .020 6 21.0 110 — 1 0 114 .0032

S37D 9/24/04 1100 .024 6 — 107 — 0 0 100 —

S37E 9/24/04 1105 < .007 4 — 147 — 2 0 230 —

S37F 9/24/04 1130 .044 23 — 276 — 2 .13 29 —

42  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Figure 12. Generalized map of the storm-drain network sampling locations for site S20 (fig. 3). (Roads, tax parcels, and 

building footprints have been added to better identify the location of the sampling sites.)

Identification of Sewage Sources to Accotink Creek  43

S20

S20B

S20A

Interstate 66

Prosperity Avenue

Long Branch

NOT TO SCALE

Figure 12. Generalized map of the storm-drain network sampling locations for site S20 (fig. 3). (Roads, tax parcels, and building

footprints have been added to better identify the location of the sampling sites.)

EXPLANATION

BUILDING FOOTPRINT

TAX PARCEL

STORM SEWER

SANITARY SEWER

STREAM

SAMPLING SITE S20B
Figure 13. Generalized map of the storm-drain network sampling locations for site S29 (fig. 3). (Roads, tax parcels, and 

building footprints have been added to better identify the location of the sampling sites.)

44  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System

S29

Beverly Drive

S29B

S29C

S29D

Woodburn Village Drive

Innova Fairfax Hospital

NOT TO SCALE

Figure 13. Generalized map of the storm-drain network sampling locations for site S29 (fig. 3). (Roads, tax parcels, and building

footprints have been added to better identify the location of the sampling sites.)

EXPLANATION

BUILDING FOOTPRINT

TAX PARCEL

STORM SEWER

SANITARY SEWER

STREAM

SAMPLING SITE S29B

S29A
Figure 14. Generalized map of the storm-drain network sampling locations for site S37 (fig. 3). (Roads, tax parcels, and 

building footprints have been added to better identify the location of the sampling sites.)

Identification of Sewage Sources to Accotink Creek  45

S37

Blake Lane

EXPLANATION

BUILDING FOOTPRINT

TAX PARCEL

STORM SEWER

SANITARY SEWER

STREAM

SAMPLING SITE S37E

NOT TO SCALE

Figure 14. Generalized map of the storm-drain network sampling locations for site S37 (fig. 3). (Roads, tax parcels, and building

footprints have been added to better identify the location of the sampling sites.)

S37A

S37E

S37F

S37D

Sutton Road

Interstate 66

Oakton

High

School

Concession stand
to develop a watershed-level understanding of the system, 

each of the other tools provided information in addition to 

synoptic sampling, and their usefulness likely is dependent on 

the system being investigated. These tools add another line of 

evidence (in addition to synoptic sampling) that can be used to 

identify sewage sources.

Transferability of This Approach

 One objective of this study was to develop an approach 

that could be transferred and applied to other watersheds 

throughout Virginia and the mid-Atlantic region. It was 

because of this objective that a relatively simple and inexpensive collection of indicator tracers was used. Although the 

analyses for the 13 organic compounds as confirmatory tracers 

are not as easy or inexpensive to apply as the indicator tracers, 

these analyses for organic compounds are becoming more cost 

efficient and common in analytical chemistry laboratories. 

Using theoretical results from direct sewage sampling as 

well as an overflowing sewer line, this study has demonstrated 

the effectiveness of this suite of sewage tracers in identifying 

major sewage sources to a stream. Consequently, a similar 

synoptic sampling study could be developed in other watersheds where sustained major sewage sources are a concern. In 

application, it likely would take only a few sampling events to 

identify whether a watershed was affected by major sewage 

sources.

Additionally, a subset of indicator tracers appears to 

be effective in identifying minor sewage sources to streams, 

but the approach likely is not as powerful as it is for locating 

major sewage sources. Although this subset of the indicator 

tracers can be used to identify minor sewage sources to 

streams, it is important to use confirmatory organic compound 

analyses and other tracer tools, such as optical brightener 

monitoring. Identifying minor sewage sources requires more 

sampling than does identifying major sewage sources. Minor 

sewage sources become increasingly more difficult to identify 

as the percentage of sewage contribution to total streamflow 

becomes smaller and smaller.

In addition to the challenges of locating minor sewage 

sources to a stream reach, it can be difficult to identify the 

specific manner in which sewage is being contributed to 

the stream. Both Fairfax County and the City of Fairfax 

investigated their respective sites that had elevated relative 

impairment indices; however, the identification of minor 

sewage sources was very challenging. For example, the City 

of Fairfax was unable to identify the source of sewage along 

the T51 tributary, despite data that indicated a sewage source. 

Additionally, Fairfax County was unable to identify a source 

of sewage at sites T35 and T35A until residents of a nearby 

condominium complex complained to property management 

about sewage problems, and at least one broken lateral line 

was discovered and replaced. Because minor sewage sources 

are difficult to locate using standard sampling techniques 

and difficult to identify and repair, minor sewage sources to 

streams are a continuing challenge in urbanized watersheds.

Next Steps and Future Directions

This study was designed to develop a suite of tracers 

that can be used effectively for identifying sewage sources to 

streams. Because of the complex pathways in which sewage 

can be routed into streams, the sampling design for this study 

included synoptic sampling under base-flow conditions. 

Sampling under base-flow conditions ensured the greatest 

opportunity for relatively stable water-quality conditions 

throughout the watershed and the highest concentrations of 

sewage. Although the study was successful in the development 

of an approach for identifying major sewage sources and 

appears to have been successful in the development of an 

approach for identifying minor sewage sources, a number of 

future directions remain to be considered.

Although a list of priority sites that are most likely to be 

affected by sewage sources have been identified (tables 10 

and 11), it has been extremely difficult for local authorities 

to confirm minor sewage sources even at some of the most 

likely sites, such as T35 and T51. Locating minor sources is 

a challenge because of the inherently low volumes of sewage 

that are contributed to a stream and because the sewage generally is transported through subsurface pathways rather than 

over the land surface. Furthermore, some potential sewage 

sources are outside the management of local governments. 

For example, a thorough evaluation of sites T35 and T35A 

revealed no problems with the sewer lines and no problems 

with cross-connected pipes; it was not until several months 

had passed that the damaged lateral line at a nearby condominium complex was discovered and repaired. Situations such 

as these will always be difficult for local authorities to identify. 

In addition to the difficulties associated with locating 

minor sewage sources, there also are difficulties associated 

with episodic and wet-weather sources of sewage. Episodic 

sources are short-lived sewage releases similar to the 

occurrence at site S7, which was identified during the initial 

watershed reconnaissance. By the time the input was discovered the flows had begun to decrease. Wet-weather sources are 

sewage sources that occur only in conjunction with rainfall, 

such as overland runoff of pooled sewage from a failed septic 

system or episodic sewage overflow caused by the temporary 

pressurization of a sewer line. The synoptic sampling design 

used in this study was not designed to locate these types of 

sewage sources, and it would be very difficult to develop a 

study to specifically investigate these types of sources. As 

such, it remains unknown how significant either of these 

sources may be in the Accotink Creek watershed. 

An additional consideration that likely compounded the 

difficulty in locating sewage sources to Accotink Creek is 

related to the actions taken by both the City of Fairfax and 

Fairfax County authorities in rehabilitating the sewer-line 

infrastructure; both local governments are proactive in 

46  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
reviewing the condition of the sewer lines, maintaining them 

as needed, and replacing or re-lining them as necessary 

(U.S. Environmental Protection Agency, undated; City of 

Fairfax, undated). It would be interesting to apply this same 

study approach in another watershed where such a proactive 

maintenance approach for sewer lines is not being used. 

Summary and Conclusions

The U.S. Geological Survey, in cooperation with the 

Virginia Department of Conservation and Recreation, Fairfax 

County, and the City of Fairfax, conducted a multiple-tracer 

study to investigate the sources of the sewage observed in 

Accotink Creek, an urban watershed in northern Virginia. The 

suite of tracers used in this study was selected on the basis 

of earlier sewage-tracer studies, even though none of these 

earlier studies attempted to apply all the tracers at one time. 

The tracers used in this study were indicator tracers that are 

relatively simple and inexpensive to apply, and confirmatory 

tracers that are relatively difficult and expensive to analyze. 

Indicator tracers included fecal coliform bacteria, surfactants, 

boron, chloride, chloride/bromide ratio, specific conductance, 

dissolved oxygen, turbidity, and water temperature. The 

confirmatory tracers included 13 organic compounds that 

are associated with human waste and include caffeine, 

cotinine, triclosan, a number of detergent metabolites, several 

fragrances, and several plasticizers. Following a literature 

review to identify the suite of sewage tracers, raw sewage was 

sampled and compared to background stream-water tracer 

concentrations to validate that the selected tracers were indeed 

indicative of sewage sources. Based on the validation of the 

tracers for identifying sewage sources to a stream, the study 

was designed as a series of eight base-flow synoptic sampling 

events to characterize the tracer concentrations in the main 

channel of Accotink Creek, its tributaries, and all storm drains 

with flow. 

Through the synoptic sampling and subsequent data 

analysis, several major sewage sources were identified 

using the suite of tracers selected. To the extent possible, all 

major sewage sources were addressed immediately by the 

appropriate local authorities to ensure that the sources of 

sewage were eliminated. In addition, several other sampling 

sites were identified that likely have minor sewage sources, 

and these sites may need additional study and investigation. 

Surfactants, boron, and fecal coliform bacteria were the most 

efficient indicator tracers for identifying minor sewage sources 

because they had the greatest relative concentration differences between the background Accotink Creek stream-water 

tracer composition and the composition of raw sewage. In 

the identification of both major and minor sewage sources, 

the wastewater organic compound tracers were valuable for 

confirming the results of the indicator tracers. Although the 

project was successful at identifying several sewage inputs to 

Accotink Creek, the variabilities in the tracer concentrations 

between synoptic sampling events at some sampling sites 

proved to be challenging in regard to data interpretation.

Near the end of the synoptic sampling, several additional 

sampling techniques were used to better characterize the sites 

with potential sewage sources and to better understand the 

variabilities in tracer concentrations that were observed at 

certain sampling sites. These additional sampling techniques 

included optical brightener monitoring, intensive stream 

sampling using automated samplers, and additional sampling 

of several storm-drain networks. Collectively, the additional 

sampling techniques provided a complement to the synoptic 

sampling approach that was used for the bulk of this study.

Through this multiple-tracer study, several sewage 

sources to the Accotink Creek watershed were identified and 

several other sites were prioritized for further investigation. 

In addition to directly resulting in improved water quality in 

Accotink Creek, this study serves as a template for investigating sewage sources to other watersheds. 

Although this multiple-tracer approach was demonstrated 

to be effective for detecting sewage sources to streams, 

additional research is needed to better detect extremely 

low-volume sewage sources and enable local authorities to 

identify the specific sources of sewage once it is detected in a 

stream reach.

Acknowledgments

The extensive water-quality sampling for this study was 

only possible because of the assistance provided by many 

hard-working, highly motivated USGS and Fairfax County 

staff members. USGS employees who participated in collecting samples include: Douglas Moyer, Trisha Baldwin, John 

Jastram, Russell Lotspeich, Brent Banks, Alan Simpson, 

Jefferson Keaton, Jennifer Krstolic, Steven Schriver, and Dawn 

Land. Fairfax County staff who participated in collecting 

samples include: Laura Grape, Shannon Curtis, Chad Grupe, 

Danielle Derwin, Amanda Pennock, Gayle England, Matthew 

Handy, and Russell Smith. Fairfax County Environmental 

Laboratory personnel, including David Bushman, Brian 

Polick, Judy Fincham, Amro Veun, Gerry Shero, Nedson 

Dumbo, Roger Rionda, Pat O’Connor, and LaWanda Posey, 

are thanked for performing the boron, chloride, and bromide 

analyses. Steven Zaugg, of the USGS, analyzed the wastewater 

organic compounds for this study and was extremely helpful 

in the interpretation of these data. Peter Cinotto and Denise 

Dumouchelle, both of the USGS, are thanked for providing 

technical reviews of this report. 

Acknowledgments  47
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Brunner, P.H., Capri, S., Marcomini, A., and Giger, W., 1988, 

Occurrence and behaviour of linear alkylbenzenesulphonates, nonylphenol, nonylphenol mono- and nonylphenol 

diethoxylates in sewage and sewage sludge treatment: Water 

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Chen, M., 1988, Pollution of ground water by nutrients and 

fecal coliforms from lakeshore septic tank systems: Water, 

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City of Fairfax, undated, Utilities department, sanitary sewer 

capacity, management, operations and maintenance program 

(CMOM). Document provided in 2005 by Adrian Fremont, 

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on the environment, chapter III, water resources; accessed 

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Froelich, A.J., and Zenone, Chester, 1985, The relation of 

water quality to geology and land use changes in Fairfax 

County and vicinity, Virginia: U.S. Geological Survey 

Miscellaneous Investigations Series Map I–1561, scale 

1:48,000.

Helsel D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources: U.S. Geological Survey Techniques of 

Water Resources Investigations, book 4, chap. A3, 512 p.; 

accessed July 7, 2005, at http://water.usgs.gov/pubs/twri/

twri4a3/ .

Hyer, K.E., and Moyer, D.L., 2003, Patterns and sources of 

fecal coliform bacteria in three streams in Virginia, 1999–

2003: U.S. Geological Survey Water-Resources Investigations Report 03–4115, 76 p.

Johnston, P.M., 1962, Geology and ground-water resources of 

the Fairfax quadrangle, Virginia: U.S. Geological Survey 

Water-Supply Paper 1539–L, 61 p.

Johnston, P.M., 1964, Geology and ground-water resources 

of Washington D.C., and vicinity: U.S. Geological Survey 

Water-Supply Paper 1776, 97 p.

Juanico, M., Ronen, D., and Shelef, G., 1990, The use of 

non-conservative parameters to trace wastewater effluents in 

water bodies: Water Research, v. 24, p. 1245–1250.

Neal, C., Fox, K.K., Harrow, M., and Neal., M., 1998, Boron 

in the major UK rivers entering the North Sea: The Science 

of the Total Environment, v. 210/211, p. 41–51.

Porter, H.C., Derting, J.F., Elder, J.H., Henry, E.F., and Pendleton, R.F., 1963, Soil survey of Fairfax County, Virginia: 

U.S. Department of Agriculture, 103 p.

Rantz, S.E., and others, 1982, Measurement and computation 

of streamflow, Volume 1—Measurement of stage and discharge: U.S. Geological Survey Water-Supply Paper 2175, 

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microbial source tracking—A survey: Seattle, University of 

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Simmons, G.M., Waye, D.F., Herbein, S., Myers, S., and 

Walker, E., 2000, Estimating nonpoint fecal coliform 

sources in Northern Virginia’s Four Mile Run watershed 

[abs.], in Younos, T., and Poff, J., eds., 2000, Abstracts of 

the Virginia Water Resource Symposium 2000: Blacksburg, 

Virginia Water Resources Research Center Special Report 

SR–19–2000, p. 248–267.

Stewart, J.R., Ellender, R.D., Gooch, J.A., Jiang, S., Myoda, 

S.P., and Weisberg, S.B., 2003, Recommendations for 

microbial source tracking—Lessons learned from a methods comparison study: Journal of Water Health, v. 1, no. 4, 

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Stoeckel, D.M., Mathes, M.V., Hyer, K.E., Hagedorn, C., 

Kator, H., Lukasik, J., O’Brien, T.L., Fenger, T.W., Samadpour, M., Strickler, K.M., and Wiggins, BA., 2004, Comparison of seven protocols to identify fecal contamination 

sources using Escerichia coli: Environmental Science and 

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48  A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
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Effects of wastewater and combined sewer overflows on 

water quality in the Blue River basin, Kansas City, Missouri 

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Literature Cited  49
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

A1 1 12/3/2001 1715 na 0.028 na nd 33 9.5 9.6 7.2 178 

A11 1 12/5/2001 1240 na 0.024 na nd 38 22.0 10.0 7.0 257 

A12 1 12/6/2001 1005 na 0.025 na nd 50 17.0 9.3 7.0 292 

A13 1 12/6/2001 1140 na 0.029 na nd 54 20.5 10.0 6.9 323 

A14 1 12/6/2001 935 na 0.029 na nd 79 15.5 9.5 7.1 421 

A15 1 12/6/2001 1505 na 0.080 na nd 111 22.5 12.6 7.3 542 

A16 1 12/6/2001 1138 na 0.028 na nd 118 21.0 9.8 7.2 544 

A2 1 12/4/2001 950 na 0.027 na nd 31 17.0 7.4 7.4 234 

A3 1 12/3/2001 1202 na 0.028 na nd 35 15.5 8.8 7.3 232 

A4 1 12/3/2001 1315 na 0.030 na nd 34 16.0 9.8 7.2 145 

A5 1 12/4/2001 835 na 0.030 na nd 34 5.0 7.8 6.8 245 

A6 1 12/4/2001 851 na 0.029 na nd 32 5.7 7.0 7.8 235 

A7 1 12/4/2001 1601 na 0.026 na nd 31 13.0 8.9 7.5 236 

A8 1 12/5/2001 1030 na 0.022 na nd 36 18.0 8.8 6.8 254 

A9 1 12/5/2001 1031 na 0.025 na nd 36 21.5 8.9 7.0 261 

S1 1 12/4/2001 1650 na 0.010 na nd 21 17.5 12.5 6.5 224 

S10 1 12/4/2001 1350 na 0.034 na nd 12 20.0 10.0 6.0 182 

S12 1 12/5/2001 1620 na 0.037 na nd 44 21.0 22.5 6.8 449 

S13 1 12/5/2001 1240 na 0.021 na nd 52 25.5 12.2 7.4 375 

S14 1 12/5/2001 1603 na 0.007 na nd 38 23.0 16.0 7.3 248 

S15 1 12/5/2001 1650 na 0.013 na nd 77 17.0 nd 7.1 353 

S16 1 12/5/2001 935 na 0.011 na nd 34 15.0 8.6 6.9 182 

S17 1 12/5/2001 1120 na 0.014 na nd 41 25.0 nd 5.7 259 

S18 1 12/5/2001 1530 na 0.032 na nd 63 20.0 11.8 6.9 253 

S2 1 12/4/2001 1118 na 0.013 na nd 100 18.5 10.2 7.2 288 

S20 1 12/5/2001 1555 na 0.016 na nd 18 23.0 nd 5.6 168 

S22 1 12/5/2001 1715 na 0.057 na nd 35 16.0 14.6 8.0 445 

S23 1 12/6/2001 820 na 0.013 na nd 12 12.0 nd 5.5 164 

S24 1 12/6/2001 825 na 0.011 na nd 12 12.0 nd 5.7 166 

S25 1 12/6/2001 1135 na 0.028 na nd 15 19.0 nd 5.8 125 

S26 1 12/6/2001 1120 na 0.015 na nd 16 19.0 11.4 7.2 122 

S29 1 12/5/2001 1035 na 0.016 na nd 17 17.0 12.0 7.3 233 

S3 1 12/4/2001 1550 na 0.006 na nd 26 19.5 15.0 6.3 205 

S31 1 12/6/2001 1410 na 0.023 na nd 15 24.5 13.0 6.5 133 

S32 1 12/6/2001 1520 na 0.041 na nd 32 20.0 15.0 6.3 418 

S33 1 12/6/2001 1610 na 0.015 na nd 28 18.0 15.0 6.5 231 

S34 1 12/6/2001 840 na 0.011 na nd 17 13.0 11.0 6.6 170 

S35 1 12/6/2001 905 na 0.028 na nd 94 14.0 nd 6.1 440 

S36 1 12/6/2001 855 na 0.059 na nd 269 14.0 nd 5.8 1,111 

S37 1 12/7/2001 925 na 0.026 na nd 6 14.5 8.0 7.3 144 

S38 1 12/7/2001 1449 na 0.022 na nd 29 19.0 14.1 7.1 193 

S39 1 12/7/2001 1040 na 0.016 na nd 19 17.0 11.5 7.6 144 

S4 1 12/3/2001 1700 na nd na nd nd nd nd nd nd 

S41 1 12/7/2001 1359 na 0.018 na nd 35 21.5 13.5 6.6 238 

S42 1 12/7/2001 1236 na 0.038 na nd 88 19.0 13.1 7.4 458 

S43 1 12/6/2001 1600 na 0.019 na nd 38 20.0 nd 6.4 296 

S44 1 12/6/2001 1308 na 0.098 na nd 27 26.0 nd 6.2 367 

S45 1 12/7/2001 900 na 0.047 na nd 18 14.5 16.5 7.2 253 

S46 1 12/7/2001 1120 na 0.162 na nd 98 18.0 nd 8.0 1,039 

S47 1 12/7/2001 1315 na 0.061 na nd 124 19.0 nd 6.1 619 

50 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

9.0 na 4.7 0.15 na 87 na nd nd e 2.7

6.8 na 6.1 0.20 na 203 na nd nd e 0.852

6.8 na 4.8 0.00 na 117 na nd nd e 0.395

5.7 na 7.0 0.15 na 147 na nd nd e 1.02

7.4 na 3.0 0.15 na 208 na nd nd e 0.466

8.9 na 4.0 0.10 na 103 na 93 nd e 0.238

8.9 na 2.0 0.25 na 177 na nd nd e 0.385

10.0 na 5.8 0.00 na 140 na nd nd e 1.64

9.0 na 4.2 0.00 na 147 na nd nd e 1.626

9.5 na 3.6 0.15 na 117 na nd nd e 1.394

9.4 na 5.0 0.00 na 133 na nd nd e 1.53

10.4 na 3.4 0.13 na 867 na nd nd e 1.26

9.2 na 5.3 0.25 na 113 na nd nd e 1.48

6.6 na 5.0 0.00 na 83 na nd nd e 1.08

5.6 na 9.0 0.25 na 130 na nd nd e 1.371

nd na 3.0 0.00 na 200 na nd nd na nd

nd na 27.5 0.00 e 57 na nd nd e 0.000

nd na 3.0 0.00 e,< 3 na nd nd e 0.009

8.2 na 10.0 0.15 e 20,200 na nd nd e 0.002

nd na 1.0 0.15 e 42 na nd nd e 0.000

nd na 1.0 0.15 na 4,000 na nd nd e 0.045

9.2 na 15.0 0.15 na 340 na nd nd e 0.009

nd na 1.4 0.00 e 10 na nd nd e 0.007

5.7 na 20.1 0.13 na 2,000 na nd nd e 0.025

7.4 na 16.5 0.22 na 260 na nd nd e 0.002

nd na 12.1 0.30 na 933 na nd nd e 0.051

7.8 na 31.0 0.25 e 20 na nd nd e 0.007

nd na 0.9 0.10 na 1,533 na nd nd e 0.003

nd na 0.5 0.00 e 11,000 na nd nd e 0.007

nd na 8.4 0.00 e 25 na nd nd e 0.005

10.1 na 2.4 0.00 na 103 na nd nd e 0.014

9.0 na 3.0 0.10 na 400 na nd nd e 0.002

nd na 8.2 0.45 e 30 na nd nd e 0.009

nd na 11.1 0.75 na 200 na 150 nd e 0.001

nd na 23.6 10.00 na 97 na nd nd na nd

nd na 15.0 0.15 e 36,500 na nd nd e 0.000

nd na 1.0 0.10 e 15 na nd nd e 0.001

nd na 2.0 0.15 e 26 na nd nd e 0.002

nd na 65.0 0.20 e 54 na nd nd e 0.001

nd na 0.9 0.25 e 18,000 na nd nd e 0.001

10.4 na 2.0 0.15 e,< 3 e,< 3 nd e 0.003

nd na nd nd na 163 na nd nd e 0.000

nd na nd 0.25 e 200 na nd nd e 0.000

5.1 na 4.0 0.15 na 469 na nd nd e 0.055

10.4 na 3.0 0.15 na 193 na 200 nd e 0.023

nd na 6.0 0.00 na 127 na 140 nd e 0.000

nd na 6.0 0.25 na 2,700 na nd nd e 0.004

nd na 0.9 0.20 e 7 na nd nd e 0.001

nd na 3.5 0.13 e 16 e 16 nd e 0.001

nd na 2.2 0.25 na 90 na nd nd e 0.001

Appendixes 51
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

S48 1 12/7/2001 1010 na 0.019 na nd 132 16.5 13.0 7.1 600 

S49 1 12/7/2001 1530 na 0.059 na nd 68 18.0 14.5 8.8 547 

S5 1 12/4/2001 1205 na 0.014 na nd 25 19.0 13.2 6.4 192 

S50 1 12/7/2001 1210 na 0.045 na nd 108 17.0 14.0 7.0 538 

S51 1 12/7/2001 1710 na 0.035 na nd 65 16.0 13.9 7.9 97 

S6 1 12/4/2001 1100 na 0.044 na nd 14 17.0 10.5 6.3 265 

S7 1 12/4/2001 1340 na 0.008 na nd 24 20.5 12.0 6.8 201 

S8 1 12/4/2001 1325 na 0.112 na nd 34 20.5 13.0 6.5 349 

S9 1 12/4/2001 1340 na 0.005 na nd 14 25.0 9.0 5.6 188 

T1 1 12/4/2001 915 na 0.008 na nd 33 17.0 9.1 6.7 141 

T10 1 12/3/2001 1700 na 0.027 na nd 39 14.0 10.2 6.7 236 

T11 1 12/4/2001 1110 na 0.027 na nd 18 17.5 9.0 7.2 64 

T12 1 12/4/2001 1140 na 0.025 na nd 42 13.0 7.6 7.3 99 

T13 1 12/4/2001 1619 na 0.016 na nd 62 14.5 10.2 7.4 305 

T14 1 12/5/2001 900 na 0.014 na nd 13 9.5 8.5 7.2 139 

T15 1 12/5/2001 1400 na 0.017 na nd 22 18.5 11.6 6.9 239 

T16 1 12/5/2001 1535 na 0.016 na nd 17 21.0 13.2 6.9 145 

T17 1 12/5/2001 955 na 0.015 na nd 16 15.0 8.5 5.9 161 

T18 1 12/5/2001 1105 na 0.028 na nd 34 21.5 9.6 7.1 251 

T19 1 12/5/2001 1357 na 0.023 na nd 64 19.0 12.6 7.2 339 

T2 1 12/4/2001 1205 na 0.029 na nd 35 21.5 9.4 7.1 95 

T20 1 12/5/2001 1424 na 0.024 na nd 32 24.0 10.9 7.2 228 

T22 1 12/5/2001 830 na 0.027 na nd 25 12.0 8.2 7.2 224 

T23 1 12/5/2001 1220 na 0.028 na nd 46 22.0 9.7 7.2 291 

T24 1 12/5/2001 1345 na 0.024 na nd 52 27.0 11.0 7.1 326 

T25 1 12/5/2001 1635 na 0.020 na nd 138 16.0 11.8 6.9 650 

T26 1 12/6/2001 945 na 0.028 na nd 44 17.0 9.1 7.1 244 

T27 1 12/6/2001 1210 na 0.019 na nd 50 22.0 11.7 6.8 207 

T3 1 12/4/2001 1300 na 0.025 na nd 47 22.5 13.3 6.8 110 

T30 1 12/6/2001 1340 na 0.039 na nd 17 22.0 nd 5.8 241 

T31 1 12/6/2001 1040 na 0.027 na nd 67 21.0 9.6 6.7 325 

T32 1 12/6/2001 1635 na 0.025 na nd 97 16.0 12.7 6.8 434 

T33 1 12/6/2001 1740 na 0.028 na nd 59 17.5 10.5 6.3 340 

T35 1 12/6/2001 831 na 0.030 na nd 52 14.0 9.4 7.3 326 

T36 1 12/7/2001 1425 na 0.024 na nd 46 17.5 12.7 7.0 254 

T37 1 12/6/2001 1430 na 0.026 na nd 20 26.5 13.2 7.0 104 

T39 1 12/7/2001 850 na 0.027 na nd 23 16.0 10.6 7.0 181 

T4 1 12/4/2001 1405 na 0.024 na nd 26 19.5 13.3 6.6 159 

T40 1 12/7/2001 1000 na 0.043 na nd 26 15.5 11.1 6.9 145 

T41 1 12/7/2001 1020 na 0.024 na nd 23 15.0 10.9 6.9 182 

T42 1 12/7/2001 1125 na 0.023 na nd 24 17.5 11.6 7.1 55 

T43 1 12/6/2001 1201 na 0.019 na nd 35 18.0 12.8 7.2 242 

T44 1 12/7/2001 1350 na 0.031 na nd 26 17.5 12.7 7.4 236 

T45 1 12/7/2001 1000 na 0.033 na nd 47 14.5 11.5 7.2 288 

T46 1 12/7/2001 940 na 0.024 na nd 107 14.5 10.9 7.4 481 

T47 1 12/7/2001 845 na 0.018 na nd 76 14.5 11.0 7.4 371 

T48 1 12/7/2001 905 na 0.024 na nd 121 14.5 10.8 7.4 527 

T49 1 12/7/2001 1035 na 0.015 na nd 58 14.5 12.1 7.2 309 

T50 1 12/7/2001 1145 na 0.022 na nd 148 20.0 11.9 7.2 605 

T51 1 12/7/2001 1205 na 0.034 na nd 86 20.0 12.8 7.1 428 

52 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

nd na 0.8 0.10 e 1,133 na nd nd e 0.011

nd na 3.0 0.10 na 80 na nd nd e 0.017

8.0 na 1.0 0.00 na 3,600 na nd nd e 0.073

nd na 3.2 0.25 na 515 na 450 nd e 0.006

9.2 na 0.3 0.00 na 165 na nd nd e 0.028

nd na 7.0 0.25 na 73 na nd nd e 0.000

8.5 na 4.1 0.13 e 42,000 na nd nd e 0.025

6.0 na 3.3 0.10 e 30,000 na nd nd e 0.004

nd na 5.6 0.15 e 14,000 na nd nd e 0.000

3.8 na 29.3 0.00 na 867 na nd nd e 0.019

7.2 na 0.8 0.00 e 35 na nd nd e 0.029

6.0 na 1.4 0.15 e 47 na nd nd e 0.01

8.9 na 1.1 0.15 na 77 na nd nd e 0.147

9.3 na 1.0 0.00 na 113 na nd nd e 0.038

nd na 2.0 0.25 e 15 na nd nd e 0.014

9.5 na 8.0 0.00 na 1,667 na nd nd e 0.055

8.6 na 2.0 0.00 na 103 na nd nd e 0.013

nd na 15.0 0.00 na 800 na nd nd e 0.002

6.9 na 5.0 0.15 na 103 na nd nd e 0.199

9.5 na 3.0 0.15 na 540 na nd nd e 0.115

7.7 na 2.7 0.13 na 133 na nd nd e 0.051

10.0 na 2.0 0.15 e 39 na nd nd e 0.189

7.4 na 3.5 0.00 na 3,000 na nd nd e 0.03

8.5 na 2.0 0.00 na 100 na nd nd e 0.33

9.4 na 2.3 0.13 e 777 na nd nd e 0.132

2.7 na 30.4 0.25 na 900 na nd nd e 0.004

8.1 na 8.7 0.20 na 1,667 na nd nd e 0.288

5.2 na 3.4 0.00 na 350 na nd nd e 0.08

7.9 na 1.9 0.20 na 220 na nd nd e 0.003

nd na 1.5 0.10 na 97 na nd nd e 0.000

5.0 na 6.0 0.20 na 310 na nd nd e 0.114

9.2 na 2.0 0.10 na 190 na nd nd e 0.074

nd na 4.0 0.20 na 390 na nd nd e 0.013

8.3 na 3.0 0.25 na 1,333 na nd nd e 0.1

8.2 na 1.1 0.13 e 70 na nd nd e 0.137

5.7 na 2.0 0.10 na 205 na nd nd e 0.13

9.4 na 2.0 0.15 na 733 na 623 nd e 0.071

8.6 na 16.7 0.00 na 93 na nd nd e 0.032

4.6 na 2.0 0.15 na 550 na nd nd e 0.009

7.9 na 2.0 0.15 na 193 na 150 nd e 0.062

6.0 na 2.0 0.15 na 210 na nd nd e 0.017

10.2 na 1.0 0.15 e 64 na nd nd e 0.122

9.4 na 4.6 0.10 na 1,033 na nd nd e 0.031

8.3 na 1.7 0.00 na 117 na nd nd e 0.198

9.3 na 1.8 0.13 e 23 na nd nd e 0.217

9.7 na 3.3 0.13 e 40 na nd nd e 0.141

9.8 na 2.9 0.20 e 23 na nd nd e 0.218

9.2 na 2.5 0.10 e 50 na nd nd e 0.144

10.1 na 3.8 0.00 na 430 na nd nd e 0.116

6.4 na 6.4 1.00 na 198 na nd nd e 0.054

Appendixes 53
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

T52 1 12/7/2001 1250 na 0.017 na nd 168 19.0 11.8 7.0 662 

T53 1 12/7/2001 900 na 0.033 na nd 43 12.5 11.4 7.3 294 

T54 1 12/7/2001 1345 na 0.020 na nd 25 17.5 12.5 7.7 260 

T55 1 12/7/2001 1115 na 0.036 na nd 53 16.5 11.5 8.7 336 

T56 1 12/7/2001 1055 na 0.028 na nd 32 16.5 12.5 7.3 244 

T57 1 12/7/2001 1250 na 0.024 na nd 34 18.0 14.8 6.7 196 

T6 1 12/3/2001 1105 na 0.028 na nd 48 15.5 7.6 7.2 316 

T7 1 12/3/2001 1218 na 0.018 na nd 25 16.0 9.0 6.8 13 

T8 1 12/3/2001 1245 na 0.025 na nd 61 15.0 9.8 7.2 282 

T9 1 12/4/2001 900 na 0.023 na nd 71 17.0 7.1 7.0 390 

A1 2 4/2/2002 1005 na 0.018 na nd 41 16.0 10.8 7.2 228 

A10 2 4/3/2002 1025 na 0.022 na nd 48 26.5 14.5 7.3 250 

A11 2 4/3/2002 905 na 0.02 na nd 48 25.0 13.6 7.2 250 

A12 2 4/4/2002 855 na 0.024 na nd 68 10.5 9.9 7.2 327 

A13 2 4/4/2002 925 na 0.028 na nd 71 11.0 10.0 7.2 350 

A14 2 4/4/2002 945 na 0.018 na nd 77 8.0 10.0 7.4 383 

A15 2 4/4/2002 1240 na 0.02 na nd 86 13.5 11.7 8.0 423 

A16 2 4/4/2002 1600 na 0.02 na nd 102 13.0 15.1 8.4 465 

A2 2 4/2/2002 1035 na 0.018 na nd 47 26.5 11.8 7.7 232 

A3 2 4/2/2002 1300 na 0.018 na nd 43 20.5 13.6 7.7 253 

A4 2 4/2/2002 1430 na 0.017 na nd 43 21.5 14.3 8.2 249 

A5 2 4/2/2002 1020 na 0.029 na nd 40 19.0 10.4 7.3 237 

A6 2 4/3/2002 915 na 0.021 na nd 41 25.5 13.8 7.7 229 

A7 2 4/3/2002 1225 na 0.022 na nd 40 25.0 15.4 7.7 230 

A8 2 4/3/2002 1545 na 0.018 na nd 46 13.0 15.2 7.2 249 

A9 2 4/3/2002 1024 na 0.022 na nd 46 22.5 14.2 7.0 256 

S1 2 4/2/2002 1600 na 0.008 na nd 26 25.0 11.0 7.2 236 

S10 2 4/3/2002 1010 na 0.044 na nd 8 nd nd 7.4 205 

S11 2 4/2/2002 1610 na 0.013 na nd 19 19.5 nd 7.6 239 

S12 2 4/3/2002 1500 na 0.031 na nd 41 13.5 20.0 8.0 350 

S13 2 4/3/2002 1240 na 0.018 na nd 35 21.5 11.5 7.6 251 

S14 2 4/3/2002 1415 na 0.012 na nd 38 15.5 11.0 7.6 236 

S15 2 4/3/2002 1455 na 0.02 na nd 69 14.5 11.5 7.1 315 

S16 2 4/3/2002 1120 na 0.015 na nd 28 24.0 16.2 6.8 107 

S17 2 4/3/2002 1140 na 0.026 na nd 37 27.0 18.0 6.9 223 

S18 2 4/3/2002 1255 na 0.03 na nd 92 22.0 14.5 6.7 465 

S19 2 4/3/2002 1350 na 0.072 na nd 28 22.0 16.8 7.4 318 

S2 2 4/2/2002 1150 na 0.011 na nd 167 26.5 11.1 6.9 179 

S20 2 4/3/2002 1325 na 0.032 na nd 28 22.0 16.8 7.4 189 

S21 2 4/3/2002 1440 na 0.14 na nd 872 nd 16.2 9.2 2,470 

S22 2 4/3/2002 1510 na 0.037 na nd 41 13.5 14.9 7.9 283 

S23 2 4/3/2002 1530 na 0.012 na nd 14 nd 14.0 7.5 146 

S24 2 4/3/2002 1535 na 0.014 na nd 19 nd 14.4 7.3 185 

S25 2 4/4/2002 1105 na 0.022 na nd 18 18.0 nd 6.5 120 

S26 2 4/4/2002 1045 na 0.012 na nd 18 18.0 nd 6.4 170 

S27 2 4/4/2002 1305 na 0.008 na nd 21 19.0 nd 6.4 157 

S28 2 4/4/2002 1325 na 0.008 na nd 23 nd nd 6.4 191 

S29 2 4/3/2002 1110 na 0.028 na nd 30 22.5 17.9 7.2 276 

S3 2 4/2/2002 1340 na 0.007 na nd 27 21.0 12.5 7.4 218 

S30 2 4/4/2002 1345 na 0.016 na nd 36 17.5 nd 6.3 208 

54 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

11.5 na 0.8 0.13 e 20 e 21 nd e 0.137

9.1 na 0.4 0.00 e 52 na nd nd e 0.077

nd na 4.1 0.10 e 520 na nd nd e 0.012

nd na 0.9 0.15 na 167 na 163 nd e 0.075

nd na 0.9 0.00 e 700 na nd nd e 0.073

7.0 na 1.0 0.30 na 143 na nd nd e 0.229

10.3 na 0.6 0.00 na 77 na nd nd e 0.034

9.0 na 2.3 0.00 e 671 na nd nd e 0.04

9.8 na 0.9 0.00 na 73 na nd nd e 0.097

8.3 na 1.0 0.00 na 250 na nd nd e 0.044

10.3 na 7.0 0.00 na 160 na nd nd e 8.084

10.7 na 6.0 0.15 na 130 na nd nd na nd

9.9 na 6.0 0.10 e 64 na nd nd e 3.25

9.0 na 4.8 0.10 na 190 na nd nd e 1.57

9.6 na 5.1 0.10 na 340 na nd nd e 1.6

10.3 na 3.9 0.15 na 130 na nd nd e 1.28

13.0 na 4.5 0.00 e 29 na nd nd e 1.49

12.8 na 3.4 0.10 e 13 e 20 nd e 0.888

11.8 na 6.0 0.10 na 120 na nd nd e 5.75

12.8 na 6.5 0.20 e 51 na nd nd e 6.56

12.2 na 5.6 0.20 e 93 na nd nd e 4.99

10.8 na 6.0 0.10 na 240 na nd nd e 5.54

10.1 na 5.2 0.15 na 250 na nd nd e 4.23

9.7 na 4.0 0.13 na 200 na nd nd e 4.39

10.4 na 5.0 0.13 e 160 na nd nd e 4.71

9.8 na 6.0 0.15 na 180 na nd nd e 4.53

nd na 1.0 0.00 e 25 na nd nd e 0.013

nd na 4.4 0.10 na 100 na nd nd e 0.000

nd na 37.6 0.05 e 8 na nd nd e 0.000

nd na 0.7 0.15 e,< 3 na nd nd e 0.004

nd na 16.0 0.10 e 28 na nd nd e 0.007

nd na 4.4 0.15 e 55 na nd nd e 0.002

11.0 na 3.1 0.15 na 1,000 na nd nd e 0.072

9.9 na 18.0 0.15 na 70 na nd nd e 0.037

nd na 0.8 0.20 na 93 na nd nd e 0.014

7.8 na 4.5 0.20 na 200 na nd nd e 0.015

nd na 1.0 0.50 na 130 na nd nd e 0.011

8.6 na 4.0 0.10 e 37 na nd nd e 0.001

nd na 2.5 0.25 e 29 na nd nd e 0.022

nd na 1.9 0.25 e 28 na nd nd e 0.001

nd na 6.0 0.10 e,< 3 na nd nd e 0.000

nd na 1.6 0.00 na 570 na nd nd e 0.006

nd na 1.5 0.00 na 340 na nd nd e 0.076

nd na 0.8 0.00 na 430 na nd nd e 0.01

nd na 1.9 0.10 na 170 na nd nd e 0.001

nd na 1.0 0.00 e 15 e 21 nd e 0.001

nd na 2.0 0.00 na 2,200 na 2,400 nd e 0.007

nd na 7.4 0.25 e 22,000 na nd nd e 0.01

nd na 2.0 0.00 e 7 na nd nd e 0.016

nd na 1.0 0.00 e 5 e 14 nd e 0.001

Appendixes 55
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

S31 2 4/4/2002 1030 na 0.037 na nd 20 14.0 10.1 6.8 155 

S32 2 4/4/2002 1050 na 0.03 na nd 36 14.0 12.0 6.8 217 

S33 2 4/4/2002 1140 na 0.014 na nd 25 12.5 11.0 6.8 142 

S34 2 4/4/2002 1415 na 0.009 na nd 43 12.5 9.5 6.3 261 

S35 2 4/4/2002 905 na 0.057 na nd 71 11.5 14.0 7.4 396 

S36 2 4/4/2002 1035 < 0.005 na nd 251 23.0 12.0 6.0 998 

S37 2 4/5/2002 900 na 0.019 na nd 8 nd nd 6.6 130 

S38 2 4/5/2002 1455 na 0.012 na nd 35 14.8 10.4 6.4 204 

S39 2 4/5/2002 1120 na 0.009 na nd 35 11.5 9.0 7.6 150 

S4 2 4/2/2002 1510 < 0.005 na nd 79 25.5 nd 7.3 368 

S40 2 4/5/2002 1215 na 0.007 na nd 31 14.0 7.0 6.4 218 

S41 2 4/5/2002 1405 na 0.016 na nd 44 14.5 12.4 6.2 249 

S42 2 4/5/2002 1330 na 0.025 na nd 65 14.5 9.9 7.9 361 

S43 2 4/4/2002 1425 na 0.012 na nd 47 15.0 11.0 6.7 322 

S44 2 4/4/2002 1458 na 0.076 na nd 31 9.5 9.5 6.6 376 

S45 2 4/5/2002 830 na 0.025 na nd 23 nd nd 6.5 240 

S46 2 4/5/2002 1040 na 0.172 na nd 140 18.0 nd 6.1 1,124 

S47 2 4/5/2002 1205 na 0.024 na nd 297 18.5 11.9 8.2 1,013 

S48 2 4/5/2002 910 na 0.02 na nd 136 9.0 10.8 7.6 590 

S49 2 4/5/2002 1040 na 0.028 na nd 164 10.5 12.0 6.4 644 

S5 2 4/2/2002 1425 na 0.011 na nd 24 21.5 12.8 6.3 201 

S50 2 4/5/2002 1158 na 0.022 na nd 87 12.5 9.5 6.5 433 

S51 2 4/5/2002 1220 na 0.037 na nd 70 10.0 10.4 7.8 413 

S52 2 4/2/2002 1530 na 0.062 na nd 36 24.5 14.3 7.0 186 

S6 2 4/2/2002 1305 na 0.033 na nd 108 26.0 13.0 7.6 520 

S7 2 4/2/2002 1205 na 0.012 na nd 29 22.0 14.5 7.0 223 

S8 2 4/2/2002 1220 na 0.016 na nd 27 22.0 13.4 6.4 292 

S9 2 4/3/2002 1030 na 0.007 na nd 15 nd nd 6.8 149 

T1 2 4/2/2002 1030 na 0.016 na nd 46 26.5 14.3 6.9 226 

T10 2 4/2/2002 1550 na 0.02 na nd 48 19.0 13.7 7.1 267 

T11 2 4/3/2002 1040 na 0.022 na nd 35 27.5 14.4 7.1 204 

T12 2 4/3/2002 1050 na 0.02 na nd 36 27.5 14.9 7.7 224 

T13 2 4/3/2002 1200 na 0.015 na nd 64 24.5 15.8 7.4 314 

T14 2 4/3/2002 1340 na 0.013 na nd 12 18.0 13.7 7.2 128 

T15 2 4/3/2002 1430 na 0.018 na nd 20 16.0 15.8 7.1 161 

T16 2 4/4/2002 900 na 0.012 na nd 21 nd nd 6.8 151 

T17 2 4/3/2002 1630 na 0.015 na nd 34 13.0 10.5 7.2 192 

T18 2 4/3/2002 945 na 0.019 na nd 33 22.0 13.6 7.0 219 

T19 2 4/3/2002 1255 na 0.027 na nd 67 20.5 14.9 7.1 315 

T2 2 4/2/2002 1215 na 0.017 na nd 27 19.0 12.9 7.3 175 

T20 2 4/3/2002 1330 na 0.02 na nd 34 18.0 15.9 7.2 196 

T21 2 4/3/2002 1010 na 0.022 na nd 23 26.5 14.9 7.5 158 

T23 2 4/3/2002 845 na 0.025 na nd 52 25.0 13.4 7.2 252 

T24 2 4/3/2002 1225 na 0.03 na nd 57 28.0 16.9 7.3 302 

T25 2 4/3/2002 1405 na 0.017 na nd 47 16.0 14.2 7.5 250 

T26 2 4/4/2002 820 na 0.017 na nd 49 10.5 8.9 7.4 250 

T27 2 4/4/2002 1015 na 0.015 na nd 63 18.0 9.7 7.1 304 

T28 2 4/4/2002 1205 na 0.013 na nd 69 12.0 11.6 7.5 321 

T29 2 4/4/2002 1145 na 0.022 na nd 35 12.0 10.1 7.4 222 

T3 2 4/2/2002 1250 na 0.034 na nd 46 26.0 18.8 6.8 207 

56 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

nd na 1.9 0.10 e 3 na nd nd e 0.006

nd na 0.4 0.10 e,< 3 na nd nd e 0.002

nd na 1.0 0.13 na 70 na nd nd e 0.004

nd na 1.0 0.10 e,< 3 na nd nd e 0.035

9.0 na 1.6 0.00 na 500 na nd nd e 0.056

nd na 13.5 0.20 e,< 3 na nd nd e 0.004

nd na 0.6 0.10 e 44,000 e 40,400 nd e 0.004

7.6 na 7.2 0.10 e,< 3 na nd nd e 0.007

11.8 na 1.4 0.05 e 33 na nd nd e 0.008

nd na 37.6 0.10 e,< 10 na nd nd e 0.000

nd na 4.2 0.05 e 27 na nd nd e 0.008

8.3 na 1.3 0.10 e 42,800 na nd nd e 0.043

12.6 na 6.3 0.15 e 200 na nd nd e 0.048

nd na 1.9 0.00 e,< 3 e 10 nd e 0.001

nd na 2.1 0.35 na 310 na 330 nd e 0.006

nd na 2.6 0.10 e 20 e 3 nd e 0.004

nd na 4.6 0.30 na 93 na nd nd e 0.000

11.2 na 2.8 0.20 e 13 na nd nd e 0.101

11.1 na 3.8 0.10 e 6,200 na nd nd e 0.293

nd na 2.1 0.20 e 3 na nd nd e 0.004

4.7 na 3.0 0.10 e 27 na nd nd e 0.024

nd na 18.0 4.50 e 20 na nd nd e 0.008

10.1 na 1.0 0.00 na 340 na nd nd e 0.048

7.4 na 3.0 0.13 na 77 na nd nd e 0.007

nd na 8.0 0.50 e 35 na nd nd e 0.000

7.2 na 3.0 0.00 na 130 na nd nd e 0.045

5.7 na 2.0 0.10 na 73 na nd nd e 0.012

nd na 5.5 0.10 e 18 na nd nd e 0.000

10.4 na 4.0 0.00 na 180 na nd nd e 0.428

11.8 na 2.3 0.15 e 39 na nd nd e 0.101

10.8 na 1.8 0.15 na 140 na nd nd e 0.106

12.4 na 1.7 0.10 e 1,300 na nd nd e 0.188

9.3 na 3.0 0.00 e 59 na nd nd e 0.082

9.6 na 2.0 0.00 na 230 na nd nd e 0.034

7.6 na 7.1 0.15 na 100 na nd nd e 0.122

nd na 1.4 0.00 e 10 na nd nd e 0.258

nd na 19.0 0.00 e 32 na nd nd e 0.016

10.0 na 2.6 0.15 na 1,100 na nd nd e 0.406

10.5 na 2.3 0.10 e 30 na nd nd e 0.128

11.6 na 2.0 0.00 e 32 na nd nd e 0.534

10.9 na 1.1 0.10 e 53 na nd nd e 0.423

10.8 na 8.2 0.10 na 120 na nd nd e 0.342

8.4 na 2.4 0.15 e 58 na nd nd e 0.685

12.0 na 5.5 0.15 na 100 na nd nd e 0.957

9.9 na 2.3 0.10 na 210 na nd nd e 0.253

9.7 na 5.1 0.10 na 240 na nd nd e 0.566

11.6 na 1.6 0.15 na 83 na nd nd e 0.679

12.2 na 2.0 0.10 na 120 na 140 nd e 0.123

12.9 na 2.0 0.10 e 18 na nd nd e 0.139

9.2 na 1.0 0.00 e 18 na nd nd e 0.013

Appendixes 57
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

T31 2 4/4/2002 845 na 0.035 na nd 95 13.0 9.0 7.0 416 

T32 2 4/4/2002 1220 na 0.021 na nd 95 16.0 11.7 6.9 409 

T33 2 4/4/2002 1315 na 0.031 na nd 376 13.0 13.5 7.0 1,300 

T34 2 4/4/2002 1330 na 0.013 na nd 24 13.0 12.2 6.7 158 

T35 2 4/4/2002 1055 na 0.02 na nd 64 10.0 11.3 7.9 337 

T36 2 4/5/2002 1320 na 0.016 na nd 62 12.5 11.1 7.6 277 

T37 2 4/4/2002 1155 na 0.016 na nd 33 12.0 12.5 8.5 205 

T38 2 4/5/2002 835 na 0.016 na nd 28 9.0 7.5 7.3 154 

T39 2 4/5/2002 920 na 0.016 na nd 35 8.0 8.2 7.8 211 

T4 2 4/2/2002 1320 na 0.019 na nd 20 22.5 16.5 6.7 97 

T40 2 4/5/2002 950 na 0.028 na nd 53 8.0 8.0 7.3 256 

T41 2 4/5/2002 1030 na 0.015 na nd 36 9.0 8.4 7.4 211 

T42 2 4/5/2002 1228 na 0.016 na nd 43 12.5 11.8 8.6 237 

T43 2 4/4/2002 1530 na 0.018 na nd 50 16.5 15.6 9.1 296 

T44 2 4/5/2002 1255 na 0.024 na nd 34 15.0 13.6 8.3 226 

T45 2 4/5/2002 810 na 0.02 na nd 57 7.0 7.3 7.3 294 

T46 2 4/5/2002 840 na 0.016 na nd 192 7.0 8.4 7.9 698 

T47 2 4/5/2002 920 na 0.01 na nd 71 13.0 8.8 8.2 325 

T48 2 4/5/2002 855 na 0.019 na nd 214 9.0 8.1 7.8 857 

T49 2 4/5/2002 955 na 0.014 na nd 59 14.0 9.7 7.2 239 

T5 2 4/2/2002 1340 na 0.018 na nd 19 22.5 16.3 7.5 129 

T50 2 4/5/2002 1055 na 0.021 na nd 275 13.0 10.3 8.2 590 

T51 2 4/5/2002 1120 na 0.023 na nd 78 13.0 9.8 7.1 380 

T52 2 4/5/2002 1215 na 0.012 na nd 182 18.5 11.1 7.5 660 

T53 2 4/5/2002 820 na 0.025 na nd 58 6.0 7.3 7.9 321 

T54 2 4/5/2002 1330 na 0.017 na nd 42 10.5 10.7 7.4 267 

T55 2 4/5/2002 940 na 0.037 na nd 62 8.0 8.0 8.1 376 

T56 2 4/5/2002 1005 na 0.023 na nd 40 8.0 9.3 7.5 248 

T57 2 4/5/2002 1300 na 0.028 na nd 45 10.0 12.1 6.9 258 

T6 2 4/2/2002 1045 na 0.015 na nd 85 15.0 12.2 7.5 398 

T7 2 4/2/2002 1335 na 0.01 na nd 25 20.0 14.7 7.2 156 

T8 2 4/2/2002 1410 na 0.019 na nd 57 21.0 15.3 7.5 278 

T9 2 4/2/2002 1030 na 0.025 na nd 176 19.0 12.6 7.0 674 

A1 3 7/8/2002 1100 na 0.028 na nd 29 29.0 21.7 6.9 207 

A11 3 7/9/2002 900 na 0.025 na nd 28 26.0 22.2 6.9 211 

A2 3 7/8/2002 1200 na 0.019 na nd 30 29.5 22.0 7.2 208 

A3 3 7/8/2002 1230 na 0.019 na nd 36 30.0 21.5 7.2 216 

A4 3 7/8/2002 1350 na 0.035 na nd 38 29.5 23.2 7.2 201 

A5 3 7/8/2002 1100 na 0.012 na nd 37 31.7 24.7 7.2 121 

A6 3 7/8/2002 1600 na 0.02 na nd 26 35.5 25.1 8.5 190 

A7 3 7/9/2002 915 na 0.03 na nd 27 23.2 21.6 7.1 206 

A8 3 7/9/2002 1115 na 0.03 na nd 32 29.3 22.7 6.9 238 

A9 3 7/9/2002 835 na 0.028 na nd 32 24.0 21.9 6.8 235 

S12 3 7/9/2002 1230 na 0.05 na nd 39 31.0 28.0 7.5 403 

S13 3 7/9/2002 1100 na 0.026 na nd 52 27.0 20.5 7.4 337 

S15 3 7/9/2002 1210 na 0.026 na nd 92 21.5 17.8 7.7 413 

S17 3 7/9/2002 1035 na 0.113 na nd 60 34.0 19.5 7.3 160 

S18 3 7/9/2002 1145 na 0.146 na nd 36 28.0 21.0 6.8 309 

S19 3 7/9/2002 1240 na 0.034 na nd 7 37.0 22.0 7.4 92 

S20 3 7/9/2002 1235 na 0.026 na nd 14 37.0 22.0 7.1 162 

58 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

7.9 na 4.8 0.10 na 280 na nd nd e 0.197

11.3 na 3.0 0.20 na 70 na nd nd e 0.285

10.2 na 2.0 0.25 e 5 na nd nd e 0.088

8.9 na 13.0 0.00 na 80 na nd nd e 0.075

13.5 na 9.2 0.10 na 4,300 na nd nd e 0.255

13.1 na 2.0 0.05 e 26 na nd nd e 0.195

13.0 na 1.8 0.10 e 36 na nd nd e 0.274

11.5 na 3.1 0.10 na 3,500 na nd nd e 0.082

14.2 na 1.5 0.10 na 130 na nd nd e 0.229

10.4 na 1.0 0.00 e 21 na nd nd e 0.216

9.8 na 1.8 0.00 na 4,100 e 2,200 nd e 0.042

12.6 na 3.0 0.10 e 50 e 44 nd e 0.247

13.9 na 4.1 0.15 e 45 na nd nd e 0.265

15.1 na 0.9 0.10 e 7 e,< 3 nd e 0.181

12.2 na 3.3 0.10 na 67 na nd nd e 0.175

11.3 na 1.7 0.10 e 45 na nd nd e 0.406

12.3 na 2.2 0.15 e 42 na nd nd e 0.568

12.3 na 1.7 0.10 e 10 na nd nd e 0.024

11.2 na 2.9 0.25 e 3 na nd nd e 0.544

10.9 na 4.9 0.10 na 73 na nd nd e 0.235

10.4 na 1.0 0.00 e 22 na nd nd e 0.216

15.0 na 2.6 0.25 e 40 na nd nd e 0.026

11.4 na 5.4 0.15 e,< 3 na nd nd e 0.1

13.1 na 0.5 0.10 e 52 na nd nd e 0.215

12.7 na 1.7 0.10 e 63 na nd nd e 0.24

11.7 na 1.0 0.00 e 35 na nd nd e 0.069

13.1 na 4.8 0.10 e 28 na nd nd e 0.108

13.4 na 1.2 0.00 na 73 na nd nd e 0.078

8.3 na 1.0 0.00 e 63 na nd nd e 0.092

11.0 na 1.4 0.15 na 150 na nd nd e 0.032

9.7 na 4.1 0.15 e 74 na nd nd e 0.131

10.8 na 3.8 0.10 e 68 na nd nd e 0.348

11.3 na 5.0 0.10 e 52 na nd nd e 0.166

5.3 na 5.1 0.10 na 97 na nd nd e 0.32

3.1 na 8.2 0.25 na 59 na nd nd e 0.221

6.5 na 4.3 0.00 na 77 na nd nd e 0.23

5.9 na 5.0 0.15 na 120 na nd nd e 0.238

6.5 na 4.0 0.10 na 67 na nd nd e 0.298

8.7 na 8.0 0.10 na 600 na nd nd e 0.537

10.7 na 2.5 0.00 na 260 na nd nd e 0.35

6.6 na 3.0 0.10 na 170 na nd nd e 0.274

5.2 na 8.0 0.10 na 190 na nd nd e 0.329

2.0 na 6.4 0.05 na 320 na nd nd e 0.809

nd na 2.0 0.00 e,< 3 na nd yes e 0.046

nd na 1.8 0.05 na 160 na nd nd e 0.001

9.2 na 4.7 0.10 na 3,000 na nd yes e 0.023

nd na 2.6 0.50 e 690 na nd nd e 0.009

nd na 4.2 0.10 na 2,700 na nd nd e 0.014

nd na 7.8 0.00 na 4,200 na nd nd e 0.003

nd na 1.0 0.00 e 7,700 na nd nd e 0.009

Appendixes 59
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

S22 3 7/9/2002 1350 na 0.035 na nd 18 39.5 25.9 7.6 208 

S24 3 7/9/2002 1410 na 0.018 na nd 12 23.5 18.0 7.2 230 

S29 3 7/9/2002 955 na 0.078 na nd 23 26.0 21.5 7.5 286 

S3 3 7/8/2002 1450 na 0.047 na nd 33 30.0 21.7 7.5 253 

S34 3 7/9/2002 1250 na 0.024 na nd 119 25.0 20.7 7.5 479 

S4 3 7/8/2002 1510 na 0.01 na nd 76 nd nd 6.9 362 

S5 3 7/8/2002 1530 na 0.013 na nd 25 27.0 18.0 6.2 209 

S52 3 7/8/2002 1345 na 0.115 na nd 58 30.0 21.5 6.8 455 

S7 3 7/8/2002 1630 na 0.039 na nd 277 30.0 27.2 7.5 1,190 

S8 3 7/8/2002 1650 na 0.063 na nd 65 30.0 20.7 6.9 567 

T1 3 7/8/2002 1135 na 0.008 na nd 37 29.5 20.9 6.7 280 

T19 3 7/9/2002 1010 na 0.024 na nd 44 27.0 20.9 7.1 276 

T2 3 7/8/2002 1320 na 0.018 na nd 35 29.0 22.5 6.7 209 

T20 3 7/9/2002 1035 na 0.047 na nd 33 29.0 21.8 7.0 211 

T22 3 7/9/2002 1430 na 0.054 na nd 46 31.0 27.0 7.6 393 

T23 3 7/9/2002 830 na 0.039 na nd 46 26.0 21.2 7.1 325 

T24 3 7/9/2002 1115 na 0.046 na nd 46 27.0 21.7 7.4 340 

T3 3 7/8/2002 1350 na 0.045 na nd 56 nd nd 7.0 266 

T58 3 7/8/2002 1530 < 0.005 na nd 141 35.5 22.6 7.1 582 

T59 3 7/9/2002 1345 na 0.023 na nd 7 33.0 22.1 6.7 52 

T6 3 7/8/2002 1110 na 0.028 na nd 68 28.0 20.1 7.2 371 

T7 3 7/8/2002 1253 < 0.005 na nd 21 31.0 nd 7.1 170 

T8 3 7/8/2002 1320 na 0.02 na nd 42 nd 20.9 7.1 215 

T9 3 7/8/2002 1218 na 0.017 na nd 102 35.0 24.9 7.5 485 

A11 4 10/22/2002 850 na 0.029 na 0.035 25 9.0 10.6 7.2 183 

A12 4 10/23/2002 830 na 0.029 na 0.036 26 8.0 10.5 7.2 195 

A13 4 10/23/2002 834 na 0.025 na 0.042 22 8.0 10.8 6.9 158 

A14 4 10/23/2002 915 na 0.039 na 0.047 36 10.0 10.9 7.1 226 

A15 4 10/23/2002 1025 na 0.027 na 0.051 37 16.0 10.9 7.3 242 

A16 4 10/23/2002 1205 na 0.031 na 0.052 45 17.0 11.0 7.5 261 

A7 4 10/22/2002 1040 na 0.032 na 0.028 22 13.0 10.8 7.3 160 

A8 4 10/22/2002 845 na 0.039 na 0.034 26 9.5 10.5 7.1 171 

A9 4 10/22/2002 835 na 0.035 na 0.035 26 10.0 10.6 7.1 179 

S12 4 10/22/2002 1230 na 0.036 < 0.002 36 16.0 16.4 7.8 394 

S13 4 10/22/2002 1155 na 0.029 na 0.045 92 nd nd 7.6 286 

S15 4 10/22/2002 1250 na 0.024 na 0.085 90 nd nd 7.4 399 

S17 4 10/22/2002 1110 na 0.016 na 0.132 44 12.5 14.5 7.4 286 

S18 4 10/22/2002 1225 na 0.032 na 0.090 44 18.0 13.1 6.8 259 

S20 4 10/22/2002 1255 na 0.010 na 0.061 15 17.5 17.0 8.1 137 

S22 4 10/22/2002 1340 na 0.087 na 0.036 14 nd nd 7.3 324 

S29 4 10/22/2002 1025 na 0.029 na 0.180 150 10.0 14.5 9.7 441 

S3 4 10/21/2002 1303 na 0.016 na 0.081 29 15.0 16.0 7.9 233 

S31 4 10/23/2002 1043 na 0.036 na 0.038 20 13.0 13.0 7.2 165 

S32 4 10/23/2002 1115 na 0.023 na 0.122 15 13.5 6.9 136 

S33 4 10/23/2002 1140 na 0.017 na 0.085 24 14.0 14.5 7.2 142 

S35 4 10/23/2002 820 na 0.051 na 0.103 62 9.0 16.0 7.4 338 

S4 4 10/21/2002 1425 na 0.016 na 0.028 49 16.0 15.0 7.3 259 

S41 4 10/24/2002 1200 na 0.025 na 0.114 47 11.0 14.8 6.0 246 

S42 4 10/24/2002 1135 na 0.045 na 0.069 46 11.0 12.0 7.3 318 

S43 4 10/23/2002 1145 na 0.018 na 0.163 40 15.0 nd 7.7 302 

60 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

6.1 na nd 0.00 na 190 na nd nd e 0.001

nd na 2.7 0.10 e 30,000 na nd nd e 0.000

nd na 26.7 0.35 e,> 50,000 na nd nd e 0.005

10.8 na 1.0 0.00 e 12,000 na nd yes e 0.036

8.5 na 1.2 0.10 na 830 na nd nd e 0.01

nd na 5.0 0.05 e,< 3 na nd nd e 0.000

6.5 na 2.0 0.15 na 240 na nd nd e 0.015

nd na 1.0 0.10 na 490 na nd nd e 0.003

7.6 na 1.0 0.25 na 440 na nd nd e 0.535

7.0 na 1.0 0.20 na 3,100 na nd nd e 0.016

7.2 na 10.2 0.00 na 77 na nd nd e 0.011

6.0 na 0.9 0.05 e 59 na nd nd e 0.006

2.3 na 7.0 0.10 na 770 na nd nd e 0.037

5.9 na 0.8 0.05 na 320 na nd nd e 0.06

nd na 5.0 0.00 na 900 na nd nd e 0.018

5.0 na 5.7 0.10 na 370 na nd nd e 0.466

9.3 na 4.1 0.10 na 4,300 na nd yes e 0.388

nd na 1.3 0.00 e 9,700 na nd nd e 0.001

9.6 na 4.4 0.00 na 97 na nd nd e 0.001

7.2 na 8.0 0.00 na 1,100 na nd nd e 0.027

6.2 na 1.0 0.10 na 70 na nd yes e 0.024

nd na 2.0 0.05 na 87 na nd nd e 0.000

7.0 na 2.0 0.10 na 140 na nd nd e 0.013

11.5 na 7.0 0.10 na 700 na nd yes e 0.096

8.5 na 5.0 0.13 na 140 na 185 nd e 0.926

8.7 na 6.0 0.13 e 200 na nd nd e 0.002

8.4 na 7.0 0.13 na 260 na nd nd e 0.443

8.8 na 5.0 0.25 e 2,100 na nd nd e 0.17

9.5 na 4.0 0.00 na 90 na nd yes e 0.147

10.8 na 3.0 0.13 na 230 na nd nd e 0.279

10.0 na 7.0 0.13 na 290 na nd nd e 1.759

9.0 na 5.0 0.13 na 160 na nd nd e 1.612

8.6 na 5.0 0.13 na 370 na nd nd e 0.563

9.5 na 2.0 0.13 e,< 3 na nd nd e 0.01

nd na 5.0 0.13 na 470 na nd nd e 0.002

nd na 1.0 0.13 e 37 e 33 nd e 0.031

nd na 1.0 0.13 e 10 na nd nd e 0.002

6.4 na 2.0 0.13 e 2,400 na 1,700 nd e 0.001

nd na 1.0 0.00 e 3 e 3 nd e 0.002

nd na 4.0 0.13 e 230 na nd nd e 0.000

nd > 1,000.0 0.00 e 1,750 na nd yes e 0.197

nd na 2.0 0.00 e 10 na nd yes e 0.002

nd na 2.0 0.13 e 230 na 390 nd e 0.004

nd na 5.0 0.13 e 37 na nd nd e 0.001

nd na 3.0 0.13 na 80 na nd nd e 0.009

8.2 na 1.0 0.13 na 170 na 130 nd e 0.023

nd na 7.0 0.00 na 160 na nd nd e 0.001

4.1 na 1.0 0.13 e 640 na nd nd e 0.028

9.7 na 6.0 0.13 na 1,300 na nd nd e 0.000

nd na 1.0 0.00 e 35 e 21 nd e 0.000

Appendixes 61
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

S44 4 10/23/2002 1305 na 0.127 na 0.119 26 nd nd 7.0 410 

S45 4 10/23/2002 1230 na 0.055 na 0.065 18 17.0 22.5 7.2 260 

S46 4 10/24/2002 1040 na 0.055 na 0.037 18 13.0 13.5 7.3 438 

S48 4 10/24/2002 903 na 0.039 na 0.186 118 12.5 13.5 7.2 565 

S49 4 10/24/2002 1025 na 0.039 na 0.062 51 nd nd 7.2 380 

S5 4 10/21/2002 1320 na 0.026 na 0.081 23 15.5 15.5 6.3 201 

S50 4 10/24/2002 1053 na 0.045 na 0.067 71 10.5 14.0 7.1 442 

S51 4 10/24/2002 1308 na 0.058 na 0.120 65 10.0 13.9 8.0 414 

S52 4 10/21/2002 1230 na 0.141 na 0.039 63 14.5 13.1 7.0 422 

S6 4 10/21/2002 1435 na 0.012 < 0.002 5 16.5 nd 7.6 73 

S7 4 10/21/2002 1412 na 0.026 na 0.056 22 14.5 14.1 6.7 228 

S8 4 10/21/2002 1345 na 0.109 na 0.050 30 13.5 14.8 6.2 313 

T1 4 10/21/2002 1210 na 0.018 na 0.039 21 nd 13.1 6.9 179 

T10 4 10/21/2002 1510 na 0.043 na 0.035 27 15.0 13.0 6.8 154 

T12 4 10/22/2002 810 na 0.029 na 0.055 49 8.0 8.9 7.1 290 

T16 4 10/22/2002 1300 na 0.021 na 0.058 15 16.5 11.0 8.4 118 

T18 4 10/22/2002 1020 na 0.030 na 0.043 17 11.0 10.4 7.0 125 

T19 4 10/22/2002 1105 na 0.058 na 0.294 79 12.0 10.5 7.2 365 

T2 4 10/21/2002 1400 na 0.022 na 0.040 24 nd 12.7 6.8 182 

T20 4 10/22/2002 1130 na 0.035 na 0.038 23 12.0 10.8 7.0 159 

T23 4 10/22/2002 830 na 0.031 na 0.074 39 6.0 10.4 7.2 247 

T24 4 10/22/2002 1200 na 0.031 na 0.105 48 12.0 10.9 7.2 321 

T25 4 10/22/2002 1320 na 0.029 na 0.042 73 18.5 11.9 7.0 175 

T26 4 10/23/2002 810 na 0.027 na 0.030 21 8.5 10.2 7.0 160 

T27 4 10/23/2002 920 na 0.022 na 0.050 33 11.0 10.3 6.8 178 

T29 4 10/23/2002 1030 na 0.025 na 0.031 61 14.5 11.0 7.2 331 

T31 4 10/23/2002 930 na 0.030 na 0.045 40 9.0 10.3 7.0 219 

T32 4 10/23/2002 1210 na 0.030 < 0.002 101 12.5 15.5 7.0 440 

T33 4 10/23/2002 1300 na 0.100 na 0.052 73 17.0 12.2 6.8 352 

T35 4 10/23/2002 840 na 0.038 na 0.065 44 9.0 10.3 7.0 270 

T36 4 10/23/2002 1355 na 0.019 na 0.042 30 17.5 11.9 6.8 165 

T37 4 10/23/2002 1105 na 0.014 na 0.028 15 15.0 11.3 7.2 118 

T38 4 10/24/2002 815 na 0.016 na 0.049 14 13.0 11.9 7.2 103 

T39 4 10/24/2002 840 na 0.031 < 0.002 17 13.0 10.5 7.1 132 

T4 4 10/21/2002 1440 na 0.036 na 0.039 43 nd nd 7.3 263 

T40 4 10/24/2002 920 na 0.036 < 0.002 20 11.5 10.9 6.9 155 

T41 4 10/24/2002 940 na 0.019 na 0.025 17 11.5 11.0 6.8 128 

T42 4 10/24/2002 1035 na 0.024 na 0.028 21 10.5 11.3 6.6 154 

T43 4 10/23/2002 1240 na 0.028 na 0.057 36 19.0 14.6 7.3 255 

T44 4 10/23/2002 1200 na 0.055 na 0.053 25 16.0 11.8 7.2 148 

T45 4 10/24/2002 835 na 0.037 na 0.058 37 10.0 11.1 7.2 214 

T46 4 10/24/2002 845 na 0.030 na 0.090 124 10.0 10.6 7.4 296 

T47 4 10/24/2002 805 na 0.017 na 0.070 62 11.0 10.8 7.3 318 

T48 4 10/24/2002 915 na 0.030 na 0.089 89 10.5 10.8 7.4 417 

T49 4 10/24/2002 1005 na 0.015 na 0.089 74 11.0 11.2 7.3 284 

T50 4 10/24/2002 1105 na 0.024 na 0.093 156 11.0 11.1 7.3 640 

T51 4 10/24/2002 1115 na 0.044 na 0.156 101 11.0 12.0 7.2 499 

T52 4 10/24/2002 1225 na 0.019 na 0.071 182 11.5 10.7 7.1 167 

T53 4 10/24/2002 815 na 0.048 na 0.038 37 10.5 10.6 7.4 252 

T55 4 10/24/2002 933 na 0.048 na 0.073 57 12.0 10.6 7.3 331 

62 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

nd na 1.0 0.13 na 70 na nd yes e 0.000

nd na 1.0 0.13 e 3 e 3 nd e 0.005

nd na 8.0 0.75 na 5,300 na nd yes e 0.000

nd na 1.0 0.13 e 56 na nd yes e 0.016

nd na 2.0 0.13 na 520 na nd nd e 0.012

6.8 na 2.0 0.00 na 460 na nd nd e 0.017

nd na 8.0 0.13 na 570 na nd yes e 0.034

9.7 na 1.0 0.13 na 2,000 na nd yes e 0.032

7.7 na 3.0 0.13 e 210 na nd nd e 0.034

nd na 7.0 0.25 na 250 na nd nd e 0.002

8.3 na 1.0 0.13 na 160 na nd nd e 0.028

5.4 na 2.0 0.37 na 2,100 na nd nd e 0.004

8.5 na 3.0 0.13 na 130 na nd nd e 0.045

4.3 na 2.0 0.13 na 260 na nd nd e 0.023

10.2 na 1.0 0.13 na 300 na nd nd e 0.026

nd na 2.0 0.13 na 360 na nd yes e 0.005

11.0 na 3.0 0.13 e 210 na nd nd e 0.157

12.1 na 2.0 0.13 na 360 na nd nd e 0.025

7.4 na 14.0 0.13 na 1,600 na nd nd e 0.049

10.6 na 1.0 0.13 na 190 na nd nd e 0.088

7.6 na 4.0 0.13 na 400 na nd nd e 0.292

8.9 na 4.0 0.25 na 2,200 na nd yes e 0.226

4.3 na 5.0 0.13 na 220 na nd nd e 0.000

8.6 na 6.0 0.13 e 220 na nd nd e 0.141

7.4 na 4.0 0.13 na 870 na nd nd e 0.042

nd na 2.0 0.13 na 200 na nd nd e 0.002

8.0 na 7.0 0.13 na 260 na nd yes e 0.142

10.0 na 3.0 0.13 e 59 na nd nd e 0.056

7.1 na 1.0 0.13 na 970 na nd nd e 0.019

7.5 na 2.0 0.13 na 770 na nd yes e 0.051

9.4 na 1.0 0.13 na 260 na nd nd e 0.087

9.7 na 2.0 0.13 na 970 na 770 nd e 0.038

10.0 na 4.0 0.13 na 340 na nd nd e 0.068

9.8 na 1.0 0.13 na 100 na nd nd e 0.062

nd na 6.0 0.13 na 200 na nd yes e 0.000

9.0 na 1.0 0.13 e 65 na nd nd e 0.025

8.5 na 1.0 0.13 na 240 na nd nd e 0.011

4.7 na 1.0 0.13 na 300 na nd nd e 0.074

11.3 na 10.0 0.13 na 550 na nd nd e 0.157

8.3 na 1.0 0.13 na 370 na 300 nd e 0.023

9.2 na 1.0 0.13 e 220 na nd nd e 0.304

9.4 na 2.0 0.13 na 80 na nd nd e 0.161

9.1 na 1.0 0.13 na 170 na nd yes e 0.007

9.7 na 3.0 0.13 na 100 na nd nd e 0.154

9.2 na 3.0 0.13 na 900 na nd nd e 0.092

9.5 na 4.0 0.13 na 800 na nd yes e 0.01

7.3 na 3.0 0.50 na 560 na nd yes e 0.025

9.7 na 3.0 0.25 na 170 na nd nd e 0.062

9.9 na 1.0 0.13 na 830 na nd nd e 0.312

9.6 na 1.0 0.13 na 550 na nd nd e 0.049

Appendixes 63
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

T56 4 10/24/2002 957 na 0.040 na 0.027 34 9.5 11.9 7.4 298 

T57 4 10/24/2002 1212 na 0.032 na 0.085 40 11.0 15.5 6.6 241 

T6 4 10/21/2002 1104 na 0.020 na 0.082 44 14.5 12.0 7.2 270 

T7 4 10/21/2002 1240 na 0.018 na 0.032 15 16.0 12.1 6.7 115 

T8 4 10/21/2002 1300 na 0.028 na 0.037 40 16.5 12.1 7.2 189 

T9 4 10/21/2002 1525 na 0.033 na 0.078 60 16.5 12.5 7.2 339 

A1 5 4/14/2003 1020 na 0.028 na 0.069 73 13.0 11.4 7.4 372 

A11 5 4/15/2003 746 na 0.035 na 0.073 87 10.5 12.9 7.2 427 

A12 5 4/16/2003 826 na 0.027 na 0.054 103 19.0 15.5 7.0 467 

A13 5 4/16/2003 846 na 0.027 na 0.073 106 21.0 15.0 7.3 450 

A13A 5 4/16/2003 1144 na 0.055 na 0.081 118 30.0 16.2 8.1 402 

A14 5 4/16/2003 940 na 0.019 na 0.066 105 21.5 15.4 7.5 458 

A14A 5 4/16/2003 1400 na 0.019 na 0.047 99 34.0 18.1 8.7 427 

A15 5 4/16/2003 1520 na 0.036 na 0.061 106 31.0 18.5 8.7 151 

A15A1 5 4/16/2003 1710 na 0.02 na 0.084 115 29.0 19.9 8.7 477 

A15A2 5 4/16/2003 1815 na 0.025 na 0.087 120 26.5 19.6 8.4 487 

A16 5 4/17/2003 844 na 0.022 na 0.087 140 15.0 14.3 7.2 579 

A2 5 4/14/2003 1110 na 0.022 na 0.068 76 20.0 12.0 7.8 372 

A3 5 4/14/2003 1120 na 0.01 na 0.076 78 22.5 11.9 7.5 369 

A4 5 4/14/2003 1220 na 0.009 na 0.08 79 29.0 13.2 8.1 372 

A5 5 4/14/2003 1430 na 0.014 na 0.081 77 30.5 15.2 8.3 359 

A6 5 4/14/2003 1540 na 0.010 na 0.083 77 21.0 15.0 8.7 366 

A7 5 4/14/2003 1650 na 0.011 na 0.083 78 20.0 15.1 8.1 368 

A8 5 4/14/2003 1610 na 0.015 na 0.076 77 22.0 15.3 8.0 386 

A9 5 4/15/2003 945 na 0.022 na 0.163 85 21.0 13.1 7.1 399 

S1 5 4/14/2003 1028 na 0.003 na 0.045 61 11.5 11.3 7.1 334 

S11 5 4/14/2003 1415 na 0.01 na 0.065 38 24.0 16.2 7.0 161 

S13 5 4/15/2003 1240 < 0.005 na 0.085 36 32.0 12.4 6.8 251 

S14 5 4/15/2003 1320 na 0.012 na 0.049 44 30.5 11.9 7.0 221 

S15 5 4/15/2003 1357 na 0.017 na 0.129 75 28.5 12.2 6.7 303 

S16 5 4/15/2003 925 na 0.022 na 0.063 45 16.0 10.6 6.5 255 

S17 5 4/15/2003 1030 na 0.039 na 0.16 83 22.5 14.0 6.7 501 

S18 5 4/15/2003 720 na 0.032 na 0.11 139 12.0 12.7 6.6 528 

S19 5 4/15/2003 1130 na 0.022 na 0.016 36 24.5 nd 7.0 263 

S2 5 4/14/2003 1225 na 0.009 na 0.031 124 19.0 11.8 6.6 539 

S20 5 4/15/2003 1110 na 0.009 na 0.079 39 24.5 nd 6.6 208 

S21 5 4/15/2003 1115 na 0.158 na 0.138 1,500 23.0 14.4 8.3 3,080 

S22 5 4/15/2003 1159 na 0.032 na 0.045 54 28.0 13.1 7.3 285 

S23 5 4/15/2003 1220 na 0.01 na 0.048 20 16.0 10.8 6.6 171 

S24 5 4/15/2003 1215 na 0.018 na 0.052 49 16.0 11.0 8.4 273 

S25 5 4/16/2003 1115 na 0.038 na 0.037 21 28.0 14.2 6.1 133 

S26 5 4/16/2003 1055 < 0.005 na 0.106 25 23.0 13.8 7.0 214 

S27 5 4/16/2003 1405 na 0.015 na 0.065 37 24.5 11.0 6.4 206 

S28 5 4/16/2003 1336 na 0.011 na 0.049 34 20.5 10.8 7.1 221 

S29 5 4/15/2003 955 na 0.013 na 0.059 27 16.5 13.2 6.4 200 

S3 5 4/14/2003 1210 na 0.008 na 0.08 83 20.5 13.5 7.0 386 

S30 5 4/16/2003 1445 na 0.026 na 0.106 59 25.5 15.5 6.6 282 

S31 5 4/16/2003 1415 na 0.029 na 0.038 34 29.0 14.0 6.4 168 

S32 5 4/16/2003 1346 na 0.032 na 0.119 51 28.5 11.5 6.2 261 

S33 5 4/16/2003 1315 na 0.028 na 0.09 68 31.5 13.0 6.3 265 

64 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

9.4 na 2.0 0.13 na 145 na nd nd e 0.229

6.4 na 1.0 0.13 na 110 na nd nd e 0.012

8.5 na 1.0 0.13 na 100 na nd nd e 0.034

8.7 na 1.0 0.13 na 510 na nd nd e 0.015

9.7 na 2.0 0.13 na 350 na nd nd e 0.046

9.3 na 1.0 0.13 na 90 na nd yes e 0.095

11.0 na 5.0 0.25 e 28 na nd nd e 19.8

8.7 na 4.0 0.13 na 180 na nd nd e 8.775

7.8 na 4.0 0.13 na 133 na nd nd e 2.207

8.9 na 6.0 0.13 na 490 na nd yes e 5.242

12.9 na 5.0 0.13 na 162 na nd nd e 5.431

12.1 na 5.0 0.13 na 70 na nd yes e 4.812

14.1 na 3.0 0.13 na 147 na nd nd e 3.888

14.6 na 5.0 0.13 na 420 na 340 yes e 4.134

13.8 na 3.0 0.13 na 93 na nd nd e 3.065

12.7 na 3.0 0.13 na 190 na nd nd e 3.939

9.9 na 3.0 0.13 na 193 na nd yes e 2.095

11.3 na 5.0 0.13 e 22 na nd nd e 15.498

11.2 na 4.0 0.13 e 33 na nd nd e 15.548

11.8 na 3.0 0.13 e 37 na nd nd e 16.123

12.8 na 3.0 0.13 e 23 na nd nd e 15.22

12.5 na 3.0 0.25 e 30 na nd nd e 13.67

12.2 na 4.0 0.25 e 51 na nd nd e 12.66

11.8 na 5.0 0.13 e 67 na nd nd e 12.471

10.6 na 6.0 0.13 na 205 na nd nd e 11.08

9.8 na 2.0 0.13 e 44 na nd nd e 0.142

7.6 na 4.0 0.13 e 22 na nd nd e 0.009

10.1 na 62.0 0.13 e 23,500 na nd nd e 0.016

10.5 na 1.0 0.13 e 20 na nd nd e 0.046

9.7 na 3.0 0.13 na 73 na nd yes e 0.394

9.9 na 9.0 0.13 na 250 na nd nd e 0.045

7.0 na 5.0 0.13 e 814 na nd nd e 0.032

7.4 na 3.0 0.13 e,< 3 na nd yes e 0.058

8.0 na 7.0 0.13 e 29 na nd nd e 0.000

9.1 na 6.0 0.13 e 30 na nd nd e 0.001

8.0 na 1.0 0.13 e,< 3 na nd yes e 0.036

7.8 na 1.0 0.25 e 35 na nd nd e 0.000

8.5 na 3.0 0.13 e 10 na nd nd e 0.089

10.0 na 2.0 0.13 na 310 na nd yes e 0.066

9.0 na 6.0 0.13 na 93 na nd nd e 0.143

14.1 na 2.0 0.13 e 10 na nd nd e 0.021

9.8 na 6.0 0.13 na 127 na nd nd e 0.029

8.0 na 1.0 0.13 e 3 na nd nd e 0.018

10.3 na 3.0 0.13 e 10 e 30 nd e 0.119

7.3 na 2.0 0.13 na 77 na nd yes e 0.060

9.1 na 7.0 0.13 e 5 na nd nd e 0.043

9.7 na 1.0 0.13 e 40 na nd nd e 0.130

5.0 na 2.0 0.25 e 9 na nd nd e 0.010

5.0 na 2.0 0.13 e< 3 na nd nd e 0.000

8.0 na 1.0 0.13 e,< 3 na nd nd e 0.014

Appendixes 65
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

S34 5 4/16/2003 1115 na 0.018 na 0.044 44 27.0 11.8 7.0 189 

S35 5 4/16/2003 820 na 0.596 na 0.03 370 22.0 nd nd nd 

S35 5 4/16/2003 825 na 0.618 na 0.026 385 22.0 12.3 9.6 1,511 

S36 5 4/16/2003 1020 na 0.049 na 0.179 306 26.0 16.0 6.4 1,127 

S37 5 4/16/2003 1725 na 0.013 na 0.071 14 31.5 12.2 7.0 131 

S38 5 4/17/2003 1140 na 0.014 na 0.041 86 15.5 12.2 6.8 355 

S39 5 4/17/2003 940 na 0.008 na 0.055 63 14.5 11.1 6.9 289 

S40 5 4/17/2003 1010 na 0.007 na 0.034 29 14.5 12.0 7.0 178 

S41 5 4/17/2003 1110 na 0.019 na 0.089 80 14.5 12.3 6.2 357 

S42 5 4/17/2003 1040 na 0.031 na 0.101 110 16.5 11.7 7.6 508 

S44 5 4/17/2003 907 na 0.058 na 0.101 56 14.5 11.6 7.5 329 

S46 5 4/17/2003 1000 na 0.035 na 0.031 136 14.0 11.4 6.9 614 

S47 5 4/17/2003 1115 na 0.026 na 0.082 316 12.0 12.4 7.7 1,164 

S48 5 4/17/2003 1034 na nd na nd nd 15.5 12.0 nd nd 

S49 5 4/17/2003 1200 na 0.047 na 0.518 283 19.0 14.5 nd nd 

S5 5 4/14/2003 1307 na 0.012 na 0.073 38 24.0 12.8 6.4 267 

S50 5 4/17/2003 1301 na 0.030 na 0.223 164 18.0 12.0 nd nd 

S51 5 4/17/2003 1334 na 0.033 na 0.132 109 16.0 12.0 7.7 563 

S52 5 4/14/2003 1129 na 0.014 na 0.049 52 19.5 12.8 7.2 215 

S6 5 4/14/2003 1235 na 0.021 na 0.021 144 22.0 nd 7.0 588 

S7 5 4/14/2003 1427 na 0.007 na 0.078 69 25.5 12.7 6.8 383 

S8 5 4/14/2003 1408 na 0.003 na 0.048 30 25.5 14.3 6.4 253 

S9 5 4/14/2003 1730 na 0.004 na 0.049 23 21.0 nd 6.4 178 

T1 5 4/14/2003 1055 na 0.017 na 0.037 36 20.0 13.6 7.2 216 

T11 5 4/14/2003 1458 na 0.012 na 0.076 41 26.5 16.4 7.3 219 

T12 5 4/14/2003 1524 na 0.011 na 0.081 45 24.5 16.3 8.0 257 

T13 5 4/14/2003 1725 na 0.007 na 0.085 64 22.0 15.2 7.2 318 

T13A 5 4/14/2003 1630 na 0.010 na 0.082 53 24.0 15.3 7.0 266 

T14 5 4/14/2003 1510 na 0.008 na 0.073 15 23.0 15.0 7.1 58 

T15 5 4/14/2003 1500 na 0.010 na 0.028 35 23.0 24.5 7.2 167 

T17 5 4/14/2003 1545 na 0.010 na 0.045 28 28.5 12.2 6.7 165 

T18 5 4/15/2003 1045 na 0.021 na 0.083 113 25.5 13.0 7.1 263 

T19 5 4/15/2003 1150 na 0.024 na 0.106 62 26.0 13.6 6.8 289 

T2 5 4/14/2003 1256 na 0.030 na 0.019 352 21.0 15.1 7.1 1,375 

T20 5 4/15/2003 1155 na 0.024 na 0.08 67 26.0 14.0 7.1 355 

T22 5 4/15/2003 920 na 0.020 na 0.907 35 18.0 12.0 7.0 237 

T23 5 4/15/2003 735 na 0.027 na 0.1 77 10.5 12.0 6.9 394 

T24 5 4/15/2003 730 na 0.021 na 0.1 81 11.0 11.1 6.7 399 

T24A1 5 4/15/2003 920 na 0.023 na 0.07 164 17.0 11.5 7.1 440 

T24A2 5 4/15/2003 1019 na 0.022 na 0.063 95 25.0 12.4 7.1 428 

T25 5 4/15/2003 1110 na 0.019 na 0.059 93 23.0 12.7 7.4 382 

T25A 5 4/15/2003 1244 na 0.015 na 0.051 33 32.5 15.7 8.6 205 

T26 5 4/16/2003 835 na 0.025 na 0.076 92 19.0 15.2 7.3 428 

T27 5 4/16/2003 1146 na 0.015 na 0.067 59 28.0 15.5 7.0 294 

T28 5 4/16/2003 1310 na 0.011 na 0.054 35 28.0 17.5 7.4 211 

T29 5 4/16/2003 1254 na 0.025 na 0.072 49 29.5 16.8 7.4 274 

T3 5 4/14/2003 1330 na 0.038 na 0.121 66 22.5 16.5 6.5 150 

T31 5 4/16/2003 1015 na 0.018 na 0.046 112 25.5 15.3 7.1 457 

T32 5 4/16/2003 1457 na 0.024 na 0.082 147 30.0 18.0 7.4 262 

T33 5 4/16/2003 1621 na 0.019 na 0.122 76 29.0 17.8 7.3 372 

66 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

11.5 na 16.0 0.13 e 30 na nd nd e 0.110

nd na 2.0 0.13 na 110 na nd yes na nd

11.1 na 32.0 0.25 na 492 na nd Not sent na nd

4.6 na 53.0 0.13 e 3 na nd nd e 0.021

10.3 na 1.0 0.13 na 2,600 na 2,100 yes e 0.067

9.3 na 30.0 0.13 e 10 e 23 nd e 0.055

10.5 na 4.0 0.13 e 8,100 na nd nd e 0.034

nd na 2.0 0.13 e,< 3 na nd blank e 0.004

8.4 na 2.0 0.13 na 1,233 na nd yes e 0.09

11.1 na 2.0 0.13 na 520 na nd yes e 0.183

9.0 na 2.0 0.13 na 177 na nd yes e 0.013

8.3 na 2.0 0.13 e 7 na nd yes e 0.003

10.3 na 2.0 0.13 na 290 na nd nd e 0.135

9.0 na 9.0 0.13 na 77 na nd yes e 0.043

6.0 na 3.0 0.25 e 28 na nd nd e 0.026

7.6 na 15.0 0.37 na 230 na nd nd e 0.065

7.0 na 7.0 0.13 e 100 e 45 yes e 0.101

10.4 na 3.0 0.13 na 340 na 320 yes e 0.093

10.8 na 2.0 0.25 e 64 na nd nd e 0.047

7.0 na 15.0 0.37 e 15 na nd nd e 0.001

9.1 na 3.0 0.13 na 546 na nd nd e 0.104

7.7 na 2.0 0.25 e 8 na nd yes e 0.011

8.0 na 2.0 0.25 e 15 na nd nd e 0.011

10.8 na 10.0 0.25 e 32 na nd nd e 1.423

10.1 na 2.0 0.13 e 53 na nd nd e 0.771

10.4 na 1.0 0.13 na 162 na nd nd e 0.392

9.7 na 2.0 0.13 na 87 na nd yes e 0.299

9.3 na 4.0 0.13 na 123 na nd yes e 0.257

8.8 na 6.0 0.13 e 20 na nd nd e 0.17

10.0 na 6.0 0.13 e 7 na nd nd e 0.000

9.2 na 7.0 0.13 e 49 na nd nd e 0.148

10.7 na 5.0 0.13 na 167 na nd nd e 1.59

10.2 na 3.0 0.13 na 73 na nd nd e 0.395

10.1 na 30.0 0.37 e 163 na nd nd e 0.730

11.0 na 2.0 0.13 na 103 na nd nd e 1.11

10.3 na 4.0 0.13 na 192 na nd yes e 0.446

8.4 na 3.0 0.13 na 260 na nd nd e 1.709

8.9 na 3.0 0.13 na 350 na nd yes e 1.42

10.2 na 2.0 0.13 na 600 na nd nd e 0.788

11.2 na 3.0 0.13 na 250 na nd nd e 0.623

12.3 na 3.0 0.13 na 208 na nd nd e 1.009

12.5 na 6.0 0.13 na 470 na nd nd e 0.314

8.7 na 4.0 0.13 na 123 na nd nd e 6.449

11.5 na 3.0 0.13 na 120 na nd nd e 0.807

11.4 na 2.0 0.13 e 7 na nd nd e 0.234

12.0 na 3.0 0.13 na 350 na 400 nd e 0.357

9.7 na 2.0 0.13 e 21 na nd nd e 0.135

8.9 na 5.0 0.13 na 93 na nd yes e 0.674

14.2 na 5.0 0.13 na 70 na nd nd e 0.502

10.2 na 2.0 0.13 na 107 e 154 yes e 0.109

Appendixes 67
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

T34 5 4/16/2003 1600 na 0.015 na 0.298 60 30.0 17.6 6.9 245 

T35 5 4/16/2003 900 na 0.026 na 0.07 77 22.0 13.7 7.3 343 

T35A 5 4/16/2003 1110 na 0.017 na 0.073 69 29.0 14.0 7.2 327 

T36 5 4/16/2003 1235 na 0.020 na 0.058 62 32.0 16.7 7.2 282 

T36 5 4/17/2003 1420 na 0.033 na 0.062 58 13.0 14.3 7.5 284 

T37 5 4/16/2003 1550 na 0.014 na 0.062 56 34.0 20.4 9.1 273 

T38 5 4/17/2003 825 na 0.008 na 0.055 29 11.0 12.1 6.6 154 

T39 5 4/17/2003 840 na 0.019 na 0.067 67 11.0 13.7 7.0 315 

T40 5 4/17/2003 900 na 0.026 na 0.062 77 11.0 13.6 7.2 335 

T41 5 4/17/2003 915 na 0.018 na 0.073 71 11.0 14.0 7.5 342 

T43 5 4/17/2003 855 na 0.022 na 0.057 85 15.0 13.1 7.4 369 

T44 5 4/16/2003 1540 na 0.024 na 0.054 33 27.0 17.8 8.4 230 

T45 5 4/17/2003 850 na 0.033 na 0.09 80 11.0 14.0 7.1 410 

T46 5 4/17/2003 855 na 0.027 na 0.083 188 11.0 14.1 7.5 780 

T47 5 4/17/2003 930 na 0.024 na 0.063 212 12.0 13.8 7.7 882 

T48 5 4/17/2003 915 na 0.024 na 0.094 185 12.0 14.2 7.3 744 

T50 5 4/17/2003 1015 na 0.023 na 0.08 244 21.0 13.9 7.3 959 

T51 5 4/17/2003 1030 na 0.026 na 0.123 88 15.5 13.0 7.4 436 

T51A 5 4/17/2003 1300 na 0.029 na 0.106 78 17.5 13.6 7.3 409 

T52 5 4/17/2003 1135 na 0.017 na 0.078 256 17.5 13.3 7.3 965 

T53 5 4/17/2003 945 na 0.025 na 0.09 77 18.0 13.7 7.7 369 

T54 5 4/17/2003 1200 na 0.017 na 0.068 51 13.5 14.4 8.0 322 

T55 5 4/17/2003 1113 na 0.033 na 0.114 108 17.0 14.0 8.5 495 

T56 5 4/17/2003 1125 na 0.022 na 0.049 45 17.5 13.0 7.3 256 

T6 5 4/14/2003 1025 na 0.008 na 0.092 133 15.0 10.7 7.5 476 

T60 5 4/16/2003 1005 na 0.014 na 0.07 53 21.0 15.2 7.4 272 

T7 5 4/14/2003 1130 < 0.005 na 0.06 44 28.0 12.6 7.0 224 

T8 5 4/14/2003 1150 na 0.008 na 0.058 66 23.5 12.8 7.3 303 

T9 5 4/14/2003 1400 na 0.009 na 0.121 143 29.5 12.8 7.0 420 

A1 6 11/10/2003 1119 na 0.022 na 0.103 38 8.0 7.5 7.3 247 

A11 6 11/11/2003 935 na 0.016 na 0.094 52 11.5 7.7 7.1 298 

A12 6 11/11/2003 1120 na 0.020 na 0.096 56 14.5 8.4 6.6 328 

A13 6 11/11/2003 1610 na 0.016 na 0.096 59 nd 9.4 6.8 335 

A2 6 11/10/2003 1203 na 0.019 na 0.105 40 11.5 8.1 7.3 256 

A3 6 11/10/2003 1055 na 0.035 na 0.106 44 5.0 7.0 6.2 269 

A5 6 11/10/2003 1220 na 0.025 na 0.107 40 13.5 7.8 6.7 271 

A6 6 11/10/2003 1355 na 0.022 na 0.106 40 10.0 7.8 6.7 272 

A7 6 11/10/2003 1700 na 0.018 na 0.097 41 12.0 7.9 7.2 261 

A8 6 11/10/2003 1538 na 0.023 na 0.111 44 11.5 8.2 7.1 270 

A9 6 11/10/2003 1715 na 0.009 na 0.099 45 5.0 8.0 7.1 280 

S13 6 11/10/2003 1550 na 0.025 na 0.112 20 10.0 12.0 7.1 238 

S15 6 11/10/2003 1625 na 0.019 na 0.139 61 8.5 13.8 6.9 311 

S18 6 11/11/2003 1040 na 0.021 na 0.130 101 14.0 14.5 6.5 445 

S20 6 11/11/2003 1250 < 0.005 na 0.078 15 13.0 6.5 7.8 146 

S22 6 11/11/2003 1410 na 0.048 na 0.106 226 nd 12.1 7.4 864 

S23 6 11/11/2003 1515 na 0.008 na 0.079 13 13.0 13.6 7.1 152 

S24 6 11/11/2003 1525 na 0.007 na 0.089 25 14.0 13.3 7.1 196 

S27 6 11/11/2003 1440 na 0.005 na 0.092 13 15.0 13.5 7.1 163 

S28 6 11/11/2003 1410 na 0.008 na 0.074 23 14.0 13.4 7.2 202 

S29 6 11/11/2003 915 na 0.018 na 0.079 29 10.0 14.9 6.4 214 

68 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

11.1 na 3.0 0.13 e 28 e 22 nd e 0.202

10.5 na 2.0 0.13 na 3,500 na nd yes e 0.425

10.2 na 2.0 0.13 e 1,700 na nd nd e 0.430

13.0 na 2.0 0.13 e 60 na nd yes e 0.335

14.0 na 2.0 0.13 e 41 e 48 nd e 0.328

12.4 na 3.0 0.13 e 24 na nd nd e 1.097

10.8 na 4.0 0.13 na 210 na nd nd e 0.254

11.7 na 3.0 0.13 e 66 na nd nd e 0.646

9.7 na 4.0 0.13 e 61 na nd yes e 0.113

12.0 na 2.0 0.13 na 127 na nd nd e 0.370

11.5 na 2.0 0.13 na 450 na nd blank e 0.407

12.2 na 3.0 0.13 na 230 na nd nd e 0.395

9.9 na 2.0 0.13 e 18 na nd blank e 1.142

10.4 na 3.0 0.13 na 580 na nd nd e 1.337

11.3 na 6.0 0.13 e 11,400 na nd nd e 0.372

9.3 na 5.0 0.13 na 400 na nd yes e 0.965

11.3 na 3.0 0.13 na 210 na nd yes e 0.497

11.3 na 2.0 0.13 na 140 na nd yes e 0.340

10.6 na 24.0 2.50 na 4,800 na nd nd e 0.203

12.5 na 2.0 0.13 e 205 na nd nd e 0.51

11.8 na 3.0 0.13 na 67 na nd nd e 0.853

15.3 na 2.0 0.13 e 28 e 20 nd e 0.113

13.2 na 2.0 0.13 na 73 na nd yes e 5.444

11.4 na 2.0 0.13 na 380 e 311 yes e 2.723

11.0 na 2.0 0.13 na 77 na nd nd e 0.113

10.2 na 4.0 0.13 na 183 na nd nd e 1.214

10.9 na 2.0 0.13 e 10 na nd nd e 0.339

11.3 na 3.0 0.25 na 100 na nd nd e 0.547

10.8 na 4.0 0.13 e 26 na nd yes e 0.433

12.1 na 6.0 0.13 na 90 na nd nd e 19

14.0 na 5.0 0.13 na 198 na nd nd e 6.582

11.9 na 5.0 0.13 na 200 na nd nd e 5.02

10.4 na 4.0 0.13 na 400 na nd yes e 4.217

10.7 na 6.0 0.13 na 93 na nd nd e 13.94

nd na 6.0 0.13 na 80 na nd nd e 11.95

nd na 7.0 0.13 na 200 na nd nd e 12.211

11.1 na 6.0 0.13 na 180 na nd nd e 10.646

11.0 na 7.0 0.13 na 260 na nd nd e 8.753

10.6 na 6.0 0.13 na 330 na nd nd e 10.66

11.1 na 5.0 0.25 na 180 na nd nd e 8.999

nd na 5.0 0.13 e 32 na nd nd e 0.011

9.7 na 3.0 0.13 na 70 na 93 nd e 0.368

7.7 na 1.0 0.25 na 155 na nd yes e 0.026

7.0 na 1.0 0.13 na 1,267 na nd yes e 0.029

11.3 na 2.0 0.25 e 220 na nd nd e 0.023

12.9 na 1.0 0.25 na 145 na nd nd e 0.067

13.6 na 3.0 0.13 na 157 na nd nd e 0.136

9.6 na 1.0 0.13 na 100 na nd nd e 0.015

10.1 na 2.0 0.13 na 200 na nd nd e 0.118

9.9 na 2.0 0.13 na 3,600 na nd yes e 0.064

Appendixes 69
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

S3 6 11/10/2003 1200 na 0.006 na 0.113 39 14.0 13.9 7.0 274 

S31 6 11/11/2003 1635 na 0.021 na 0.066 20 15.0 13.9 6.5 132 

S32 6 11/11/2003 1720 na 0.018 na 0.166 19 13.5 nd 6.8 191 

S5 6 11/10/2003 1305 na 0.014 na 0.117 25 14.0 13.8 6.7 216 

S52 6 11/10/2003 1125 na 0.024 na 0.082 40 17.0 8.0 6.7 167 

S6 6 11/10/2003 1230 na 0.008 na 0.044 5 13.0 nd 7.1 139 

S7 6 11/10/2003 1345 na 0.009 na 0.111 27 13.0 12.6 6.9 234 

S8 6 11/10/2003 1415 na 0.01 na 0.079 30 12.5 13.8 6.4 281 

T1 6 11/10/2003 1158 na 0.018 na 0.065 9 11.5 11.8 6.9 138 

T12 6 11/10/2003 1500 na 0.015 na 0.109 31 13.0 8.1 7.2 227 

T13 6 11/10/2003 1645 na 0.012 na 0.146 52 12.0 8.8 7.2 267 

T13A 6 11/10/2003 1545 na 0.013 na 0.154 52 12.5 10.2 7.0 159 

T19 6 11/10/2003 1530 na 0.023 na 0.139 47 12.5 9.5 6.9 285 

T2 6 11/10/2003 1434 na 0.019 na 0.110 26 13.5 8.9 7.1 195 

T22 6 11/11/2003 835 na 0.023 na 0.151 28 10.0 8.7 6.3 207 

T23 6 11/11/2003 835 na 0.015 na 0.114 51 8.0 7.8 7.1 301 

T23A1 6 11/11/2003 840 na 0.015 na 0.115 53 9.0 8.3 6.7 207 

T23A2 6 11/11/2003 920 na 0.014 na 0.116 53 11.0 9.0 6.8 310 

T24 6 11/11/2003 1133 na 0.013 na 0.110 51 14.0 10.2 7.0 302 

T24A1 6 11/11/2003 1105 na 0.014 na 0.107 65 14.0 9.2 6.9 340 

T24A2 6 11/11/2003 1235 na 0.014 na 0.094 61 14.0 9.8 6.9 322 

T24B1 6 11/11/2003 1200 na 0.016 na 0.097 68 12.5 9.8 7.1 273 

T25 6 11/11/2003 1345 na 0.013 na 0.091 59 16.0 9.9 7.1 302 

T25A 6 11/11/2003 1420 na 0.011 na 0.084 20 16.0 10.9 7.2 140 

T27 6 11/11/2003 1240 na 0.017 na 0.090 42 12.0 9.5 6.4 260 

T27A 6 11/11/2003 1330 na 0.013 na 0.094 46 15.5 10.0 6.5 277 

T31 6 11/11/2003 1530 na 0.027 na 0.099 71 14.0 9.7 6.6 352 

T31A1 6 11/11/2003 1600 na 0.016 na 0.106 72 16.0 10.5 6.9 310 

T31A2 6 11/11/2003 1655 na 0.020 na 0.102 84 15.0 11.2 6.8 287 

T32 6 11/11/2003 1635 na 0.023 na 0.094 84 14.0 11.8 6.8 389 

T33 6 11/11/2003 1705 na 0.017 na 0.134 59 11.0 10.8 7.1 345 

T60 6 11/11/2003 1045 na 0.017 na 0.092 37 12.5 8.2 6.4 241 

T7 6 11/10/2003 1110 na 0.015 na 0.104 30 5.0 7.6 6.7 204 

T9 6 11/10/2003 1230 na 0.021 na 0.159 71 13.5 8.7 6.7 393 

A1 7 2/17/2004 1105 na 0.016 na 0.092 102 nd 1.7 7.4 458 

A11 7 2/18/2004 920 na 0.013 na 0.096 112 2.0 2.0 7.3 513 

A12 7 2/18/2004 1120 na 0.013 na 0.11 123 7.5 2.6 7.3 539 

A13 7 2/18/2004 1605 na 0.017 na 0.104 116 6.0 4.4 7.4 512 

A13A 7 2/19/2004 935 na 0.015 na 0.087 114 10.0 2.7 nd 500 

A13B 7 2/19/2004 838 na 0.016 na 0.093 118 5.0 2.4 7.1 500 

A14 7 2/19/2004 820 na 0.017 na 0.109 121 3.5 2.2 7.3 528 

A14A 7 2/19/2004 905 na 0.016 na 0.108 119 5.0 2.4 7.4 526 

A15 7 2/19/2004 945 na 0.016 na 0.113 135 6.5 2.9 7.4 575 

A15A1 7 2/19/2004 1125 na 0.018 na 0.115 137 15.5 3.6 nd 600 

A15A2 7 2/19/2004 1150 na 0.020 na 0.114 135 10.0 4.4 7.2 544 

A15B 7 2/19/2004 1105 na 0.019 na 0.116 132 12.0 3.1 7.2 572 

A16 7 2/19/2004 1215 na 0.023 na 0.121 139 16.5 5.5 nd 600 

A16A1 7 2/19/2004 1320 na 0.018 na 0.121 139 17.5 6.0 nd 600 

A2 7 2/17/2004 1300 na 0.013 na 0.074 100 5.0 2.0 7.5 460 

A3 7 2/17/2004 1105 na 0.015 na 0.089 104 3.0 1.4 7.4 463 

70 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

9.5 na 4.0 0.00 e 16 na nd nd e 0.058

6.5 na 1.0 0.13 na 330 na 340 nd e 0.010

5.0 na 1.0 0.13 e,< 3 e 3 nd e 0.001

7.6 na 1.0 0.13 na 480 na nd yes e 0.044

7.6 na 1.0 0.13 na 93 na nd nd e 0.026

12.0 na 9.0 0.25 na 523 na nd yes e 0.002

8.8 na 2.0 0.13 e 53,900 na nd yes e 0.061

7.0 na 1.0 0.13 na 700 na nd yes e 0.012

9.2 na 5.0 0.13 na 193 na nd nd e 0.609

10.5 na 1.0 0.13 e 36 na nd nd e 0.261

10.5 na 2.0 0.13 e 43 na nd nd e 0.168

9.2 na 2.0 0.13 e 77 na nd nd e 0.21

10.3 na 1.0 0.13 e 63 e 43 nd e 0.213

10.1 na 2.0 0.13 na 103 na 120 nd e 0.410

11.3 na 2.0 0.13 na 767 na nd nd e 0.223

12.8 na 2.0 0.13 na 270 na nd yes e 1.231

10.3 na 2.0 0.13 na 933 na nd nd e 1.182

9.9 na 2.0 0.13 na 1,367 na nd nd e 1.204

12.8 na 2.0 0.13 na 500 na nd yes e 1.074

10.3 na 1.0 0.13 na 290 na nd nd e 0.426

8.9 na 1.0 0.13 na 410 na nd nd e 0.883

9.9 na 1.0 0.13 na 410 na nd nd e 0.835

9.4 na 1.0 0.13 na 250 na nd yes e 0.327

9.7 na 1.0 0.13 na 360 na nd nd e 0.252

11.3 na 1.0 0.13 na 270 na nd nd e 0.835

10.6 na 1.0 0.13 na 220 na nd nd e 0.758

9.2 na 8.0 0.13 na 200 na nd yes e 0.726

9.0 na 9.0 0.13 e 621 na nd nd e 0.614

9.1 na 8.0 0.13 na 188 na 185 nd e 0.481

12.6 na 7.0 0.13 na 240 na nd nd na nd

nd na 1.0 0.13 na 270 na nd nd e 0.111

11.7 na 2.0 0.13 na 170 na nd nd e 1.196

nd na 1.0 0.00 na 83 na nd nd e 0.503

nd na 2.0 0.13 na 110 na nd nd e 0.563

13.9 na 6.0 0.13 e 15 na nd nd e 18

13.3 na 5.0 0.13 na 240 na nd nd e 7.89

15.1 na 7.0 0.13 na 83 na nd nd e 6.334

17.0 na 5.0 0.13 e 20 e 9 nd e 8.02

11.9 na 5.0 0.13 na 163 na nd nd e 4.247

12.0 na 4.0 0.13 na 170 na nd nd e 6.332

12.6 na 7.0 0.25 na 195 na nd nd e 4.118

13.2 na 5.0 0.13 na 97 na 83 nd e 3.789

13.2 na 6.0 0.25 na 80 na nd blank e 2.965

12.5 na 7.0 0.25 na 110 na nd nd e 2.857

16.3 na 5.0 0.13 e 45 na nd nd e 2.992

15.4 na 4.0 0.25 na 147 na nd yes e 2.923

13.3 na 14.0 0.25 e 10 na nd nd e 2.643

13.6 na 5.0 0.13 e 10 na nd nd e 0.946

14.5 na 8.0 0.13 e 33 na nd nd e 14.3

15.9 na 4.0 0.13 e 58 na nd nd e 14.62

Appendixes 71
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

A5 7 2/17/2004 1255 na 0.019 na 0.1 105 5.5 2.0 7.6 472 

A6 7 2/17/2004 1410 na 0.017 na 0.084 105 5.0 2.2 7.6 475 

A7 7 2/17/2004 1649 na 0.015 na 0.08 106 6.0 2.6 7.4 470 

A8 7 2/17/2004 1445 na 0.014 na 0.109 108 6.0 2.7 7.3 479 

A9 7 2/17/2004 1520 na 0.015 na 0.111 113 5.5 2.8 7.4 497 

S1 7 2/17/2004 1053 na 0.010 na 0.06 39 4.5 7.7 7.3 300 

S13 7 2/17/2004 1520 na 0.015 na 0.097 76 5.0 nd 7.2 405 

S15 7 2/17/2004 1605 na 0.027 na 0.162 133 4.0 9.1 7.1 539 

S17 7 2/18/2004 955 < 0.007 na 0.109 69 5.0 9.6 6.6 208 

S18 7 2/18/2004 1043 na 0.025 na 0.145 180 3.0 7.9 7.0 898 

S19 7 2/18/2004 1140 na 0.011 na 0.116 132 8.0 6.5 7.1 680 

S20 7 2/18/2004 1155 < 0.007 na 0.139 78 8.0 nd 7.3 372 

S22 7 2/18/2004 1255 na 0.033 na 0.098 919 8.5 7.1 8.1 2,893 

S23 7 2/18/2004 1420 < 0.007 na 0.074 16 8.0 7.4 7.0 133 

S24 7 2/18/2004 1440 na 0.010 na 0.078 42 8.0 6.2 7.1 248 

S27 7 2/18/2004 1443 < 0.007 na 0.099 56 6.5 6.6 7.2 282 

S28 7 2/18/2004 1418 < 0.007 na 0.067 34 6.0 7.1 7.2 225 

S29 7 2/18/2004 915 na 0.009 na 0.08 32 5.0 11.1 6.4 214 

S3 7 2/17/2004 1145 na 0.012 na 0.103 48 5.5 9.0 7.1 325 

S31 7 2/18/2004 1439 na 0.022 na 0.052 33 6.5 nd 6.3 198 

S32 7 2/18/2004 1501 na 0.013 na 0.098 88 6.0 nd 6.4 433 

S35 7 2/19/2004 823 na 0.030 na 0.094 103 3.0 13.5 6.9 483 

S37 7 2/19/2004 1035 na 0.011 na 0.092 10 12.5 9.0 7.5 140 

S39 7 2/19/2004 1250 na 0.009 na 0.074 51 12.0 7.4 7.1 270 

S41 7 2/19/2004 1325 na 0.012 na 0.102 62 17.5 9.8 6.2 303 

S42 7 2/19/2004 1415 na 0.023 na 0.140 145 16.5 7.0 7.6 648 

S44 7 2/19/2004 1338 na 0.051 na 0.193 51 13.0 6.5 7.6 439 

S46 7 2/20/2004 935 na 0.022 na 0.050 214 4.5 4.9 7.0 934 

S47 7 2/20/2004 1115 na 0.028 na 0.114 375 10.0 6.0 7.6 1,304 

S48 7 2/20/2004 842 na 0.015 na 0.262 204 11.0 10.0 7.4 828 

S49 7 2/20/2004 1150 na 0.033 na 0.814 96 10.0 12.9 6.9 925 

S5 7 2/17/2004 1332 na 0.015 na 0.091 26 3.0 9.1 6.8 229 

S50 7 2/20/2004 925 na 0.014 na 0.280 141 6.5 8.4 7.0 565 

S51 7 2/20/2004 1015 na 0.030 na 0.191 166 12.5 7.2 7.7 807 

S52 7 2/17/2004 1225 na 0.013 na 0.075 57 5.5 2.5 7.4 343 

S6 7 2/17/2004 1302 na 0.016 na nd 1,572 5.5 nd 6.9 4,880 

S7 7 2/17/2004 1416 na 0.013 na 0.110 48 3.5 8.1 7.0 320 

S8 7 2/17/2004 1439 na 0.021 < 0.050 33 6.0 10.0 6.5 304 

T1 7 2/17/2004 1230 na 0.015 na 0.054 57 5.0 4.4 7.0 278 

T12 7 2/17/2004 1512 na 0.019 na 0.096 40 3.5 4.3 7.4 232 

T13 7 2/17/2004 1700 na 0.012 na 0.108 89 5.0 4.0 7.3 294 

T13A 7 2/17/2004 1600 na 0.017 na 0.104 87 6.0 4.9 7.3 277 

T19 7 2/17/2004 1505 na 0.019 na 0.101 54 5.0 4.4 7.4 293 

T2 7 2/17/2004 1340 na 0.018 na 0.081 33 5.5 3.9 7.4 162 

T22 7 2/18/2004 830 na 0.014 na 0.133 38 -1.0 3.3 7.0 226 

T23 7 2/18/2004 845 na 0.015 na 0.1 100 1.5 2.3 7.3 477 

T23 7 2/19/2004 1515 na 0.015 na 0.1 97 16.0 6.7 8.0 445 

T23A1 7 2/18/2004 904 na 0.013 na 0.1 104 2.5 2.6 7.1 458 

T23A2 7 2/18/2004 956 na 0.009 na 0.1 104 4.0 3.2 7.1 484 

T24 7 2/18/2004 1040 na 0.012 na 0.1 108 5.0 4.2 7.3 468 

72 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

16.9 na 6.0 0.13 na 193 na nd nd e 13.7

18.4 na 5.0 0.13 na 510 na nd yes e 13.13

15.3 na 5.0 0.25 na 143 na nd nd e 12.52

14.5 na 5.0 0.13 na 140 na nd nd e 11.29

14.9 na 5.0 0.13 e 20 na nd nd e 10.99

10.9 na 2.0 0.13 e 45 na nd nd e 0.129

9.0 na 7.0 0.13 e 7 na nd nd e 0.014

nd na 3.0 0.13 e 10 na nd nd e 0.348

11.8 > 1000.0 0.13 na 193 na nd nd e 0.157

9.9 na 6.0 0.25 e,< 3 na nd nd e 0.051

10.0 na 4.0 0.13 e,< 3 na nd nd na nd

nd na 1.0 0.13 e 18 na nd nd e 0.017

13.4 na 3.0 0.25 e 5 na nd nd e 0.041

11.6 na 5.0 0.13 na 480 na nd nd e 0.107

12.2 na 13.0 0.13 e 59 na nd nd e 0.204

13.7 na 3.0 0.13 na 523 na nd nd e 0.027

11.5 na 7.0 0.25 na 163 na 147 nd e 0.123

8.9 na 1.0 0.13 e 7 na nd nd e 0.063

8.0 na 6.0 0.00 na 290 na nd yes e 0.075

6.0 na 3.0 0.13 e 8 na nd nd e 0.009

7.0 na 29.0 3.80 e 43 na nd nd e 0.014

10.5 na 1.0 0.13 e 10 e 15 nd e 0.042

10.0 na 1.0 0.00 e 10,200 na nd nd e 0.037

11.0 na 2.0 0.13 na 190 na nd nd e 0.025

10.6 na 2.0 0.13 na 93 na nd nd e 0.062

12.1 na 3.0 0.13 e 11,800 na nd nd e 0.178

nd na 3.0 0.25 e 2,300 na nd yes e 0.062

11.0 na 3.0 0.13 na 5,500 na nd yes e 0.01

12.9 na 3.0 0.13 e 30 e 27 nd e 0.219

11.0 na 6.0 0.13 na 137 na nd nd e 0.026

8.8 na 7.0 0.13 e 5 na nd nd na nd

8.8 na 1.0 0.00 na 177 na nd nd e 0.050

10.8 na 1.0 0.13 e 5 na nd nd e 0.041

12.5 na 5.0 0.13 na 4,300 na nd yes e 0.141

12.6 na 1.0 0.13 e 14 na nd nd e 0.038

7.0 na 11.0 0.50 e 3 na nd yes e 0.001

10.2 na 2.0 0.13 na 2,000 na nd yes e 0.094

8.1 na 3.0 0.13 e 3 na nd nd na nd

13.6 na 10.0 0.13 na 220 na nd nd e 0.785

12.9 na 2.0 0.13 e 10 na nd nd e 0.4

12.4 na 2.0 0.00 e,< 3 na nd nd e 0.226

12.2 na 2.0 0.13 e,< 3 na nd nd e 0.291

16.6 na 3.0 0.00 e 25 na nd nd e 0.541

15.5 na 1.0 0.00 e 9 na nd nd e 0.534

18.5 na 3.0 0.13 na 933 na 1,167 yes e 0.345

12.3 na 9.0 0.25 na 550 na 600 yes e 1.354

15.3 na 5.0 0.13 e 20 na nd nd e 1.581

13.3 na 7.0 0.25 na 340 na nd yes e 1.514

14.8 na 10.0 0.13 na 240 na nd nd e 0.848

12.7 na 13.0 0.13 na 290 na nd yes e 1.32

Appendixes 73
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

T24 7 2/19/2004 1600 na 0.013 na 0.1 110 15.0 8.0 7.2 494 

T24A1 7 2/18/2004 1112 na 0.011 na 0.11 124 5.0 3.3 7.1 546 

T24A2 7 2/18/2004 1230 na 0.018 na 0.101 130 9.0 4.6 7.2 555 

T24B1 7 2/18/2004 1205 na 0.015 na 0.10 129 5.0 3.9 7.2 554 

T25 7 2/18/2004 1220 na 0.010 na 0.093 122 8.0 3.7 7.4 530 

T25A 7 2/18/2004 1320 na 0.011 na 0.075 32 9.5 5.6 7.6 204 

T27 7 2/18/2004 1229 na 0.008 na 0.092 62 9.0 4.0 7.0 323 

T27A 7 2/18/2004 1315 na 0.012 na 0.095 69 8.5 5.0 7.1 344 

T31 7 2/18/2004 1538 na 0.028 na 0.111 184 6.0 3.9 7.2 686 

T31A1 7 2/18/2004 1404 na 0.019 na 0.112 176 7.0 5.5 7.1 690 

T31A2 7 2/18/2004 1540 na 0.020 na 0.107 188 4.5 5.3 7.1 743 

T32 7 2/18/2004 1515 na 0.015 na 0.102 172 6.5 6.4 7.0 690 

T33 7 2/18/2004 1540 na 0.016 na 0.144 85 5.5 5.9 7.6 425 

T35 7 2/19/2004 850 na 0.021 na 0.10 85 4.0 4.2 7.3 402 

T35A 7 2/19/2004 930 na 0.014 na 0.091 80 5.0 4.5 7.3 373 

T35A 7 2/20/2004 1200 na 0.013 na 0.089 76 14.0 6.1 7.4 358 

T36 7 2/19/2004 1010 na 0.014 na 0.078 69 7.5 4.5 7.1 329 

T37 7 2/19/2004 1024 na 0.015 na 0.099 88 10.0 3.2 7.5 399 

T38 7 2/19/2004 1120 < 0.007 na 0.080 30 13.0 8.0 7.1 186 

T40 7 2/19/2004 1205 na 0.019 na 0.092 119 16.0 4.1 7.2 505 

T41 7 2/19/2004 1220 na 0.013 na 0.122 125 12.0 4.5 7.4 538 

T43 7 2/19/2004 1255 na 0.018 na 0.082 80 12.0 8.4 7.5 195 

T44 7 2/19/2004 1415 na 0.023 na 0.072 29 15.0 10.3 7.5 211 

T45 7 2/19/2004 1415 na 0.012 na 0.11 113 12.0 6.0 nd 500 

T46 7 2/19/2004 1507 na 0.017 na 0.111 154 12.0 6.1 7.5 649 

T47 7 2/19/2004 1539 na 0.012 na 0.107 82 12.0 8.2 7.7 312 

T48 7 2/19/2004 1610 na 0.017 na 0.113 190 12.0 6.0 7.6 744 

T50 7 2/20/2004 1000 na 0.012 na 0.10 252 8.5 4.8 7.2 958 

T51 7 2/19/2004 1505 na 0.017 na 0.106 97 14.0 7.1 nd 400 

T51 7 2/20/2004 913 na 0.012 na 0.125 91 6.0 5.7 7.2 445 

T51A 7 2/19/2004 1540 na 0.019 na 0.121 77 15.0 7.3 nd 400 

T51A 7 2/20/2004 1035 na 0.022 na 0.119 76 14.5 6.0 7.2 405 

T51B 7 2/20/2004 1000 na 0.016 na 0.121 78 11.0 5.8 7.2 405 

T51C 7 2/20/2004 1133 na 0.020 na 0.085 65 11.0 7.3 7.4 331 

T52 7 2/20/2004 1046 na 0.017 na 0.090 242 8.5 5.9 7.2 923 

T53 7 2/20/2004 835 na 0.016 na 0.14 102 1.5 3.9 7.1 495 

T54 7 2/20/2004 1102 na 0.013 na 0.093 53 11.0 6.1 6.5 345 

T55 7 2/20/2004 835 na 0.019 na 0.182 124 4.0 4.0 7.6 567 

T56 7 2/20/2004 900 na 0.011 na 0.093 67 7.0 5.7 7.1 360 

T57 7 2/20/2004 1110 na 0.014 na 0.096 86 10.0 2.6 7.0 424 

T60 7 2/18/2004 1045 na 0.015 na 0.10 76 4.0 2.2 7.2 367 

T7 7 2/17/2004 1040 na 0.009 na 0.08 53 2.5 2.7 7.3 254 

T9 7 2/17/2004 1230 na 0.011 na 0.132 128 4.0 2.6 7.4 490 

A13 8 9/12/2004 1230 na 0.017 na 0.016 40 25.0 21.0 6.7 257 

A13 8 9/14/2004 915 na 0.025 na 0.078 54 22.5 20.7 6.9 314 

A15 8 9/12/2004 1035 na 0.023 na 0.016 54 26.0 20.8 6.7 324 

A15 8 9/14/2004 1322 na 0.026 na 0.079 76 25.0 21.5 6.1 394 

A15B 8 9/12/2004 1055 na 0.021 na 0.070 54 27.0 21.0 6.7 328 

A15B 8 9/14/2004 1409 na 0.023 na 0.077 74 nd 21.5 6.2 312 

A6 8 9/12/2004 1000 na 0.022 na 0.059 36 22.5 20.2 6.6 236 

74 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

12.0 na 5.0 0.25 na 410 na nd yes e 1.39

12.9 na 4.0 0.25 na 97 na nd nd e 0.747

12.5 na 4.0 0.13 na 67 na nd nd e 0.546

12.4 na 3.0 0.13 e 52 na nd nd e 1.086

13.1 na 4.0 0.13 na 175 na nd nd e 0.484

12.5 na 2.0 0.13 na 80 na nd nd e 0.259

13.8 na 2.0 0.13 e 12 na nd nd e 1.081

16.3 na 2.0 0.13 e 12 na nd nd e 0.951

15.0 na 9.0 0.13 e 3 na nd nd na nd

13.0 na 6.0 0.25 e 49 na nd nd e 0.861

12.1 na 16.0 0.25 e 3 na nd nd e 0.804

13.5 na 15.0 0.13 e,< 3 na nd nd e 1.388

13.9 na 3.0 0.13 e 5 na nd nd e 0.175

15.1 na 2.0 0.13 na 2,500 na 5,200 nd e 0.4

14.6 na 2.0 0.13 na 3,700 na nd yes e 0.459

8.5 na 3.0 0.13 na 1,067 na nd nd e 0.454

15.6 na 3.0 0.13 na 86 na nd yes e 0.354

13.4 na 5.0 0.25 na 240 na nd nd e 1.189

12.2 na 9.0 0.13 na 67 na nd nd e 0.208

12.5 na 4.0 0.13 e 7 na nd nd e 0.14

13.4 na 5.0 0.13 na 320 na 340 nd e 0.440

15.2 na 5.0 0.13 e 90 na nd nd e 0.599

13.2 na 2.0 0.13 e 40 e 53 nd e 0.274

13.6 na 6.0 0.25 e 7 na nd nd e 0.554

14.2 na 5.0 0.13 e 35 na nd nd e 1.451

12.6 na 2.0 0.13 e 23 na nd nd e 0.544

14.4 na 7.0 0.13 na 67 na nd nd e 1.036

14.4 na 2.0 0.13 na 967 na 900 nd e 0.669

10.5 na 5.0 0.75 na 767 na nd yes e 0.556

11.1 na 7.0 0.13 na 1,100 na nd yes e 0.595

10.7 na 6.0 0.75 e 10 na nd nd e 0.51

11.2 na 5.0 0.25 na 87 na nd nd e 0.581

11.6 na 8.0 0.25 e 65 na nd nd e 0.450

11.2 na 4.0 0.13 na 360 na nd nd na nd

14.0 na 4.0 0.13 na 190 na nd nd e 0.354

13.4 na 2.0 0.00 na 290 na nd nd e 0.656

12.4 na 2.0 0.13 e 25 na nd nd e 0.267

12.6 na 4.0 0.13 na 410 na 290 nd e 0.316

12.5 na 2.0 0.13 na 4,100 na nd yes e 0.272

10.8 na 2.0 0.13 na 87 na nd nd e 0.157

14.7 na 4.0 0.13 e 58 na nd nd e 1.658

15.5 na 2.0 0.00 e 10 na nd nd e 0.366

15.3 na 3.0 0.25 e 7 na nd nd e 0.437

6.5 na 8.0 0.13 na 1,100 na nd nd na nd

6.5 na 7.0 0.13 na 1,700 na 1,133 nd e 1.185

7.6 na 3.0 0.25 na 2,000 na nd yes na nd

7.7 na 3.0 0.13 na 1,833 na nd nd e 0.763

7.7 na 3.0 0.13 na 1,875 na nd nd na nd

7.9 na 4.0 0.13 na 2,800 na nd nd e 1.067

8.1 na 7.0 0.50 na 1,067 na nd yes na nd

Appendixes 75
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

A6 8 9/13/2004 1205 na 0.025 na 0.070 40 27.0 20.9 7.4 244 

S13 8 9/12/2004 1130 na 0.018 na 0.073 28 25.0 nd 7.9 258 

S13 8 9/13/2004 1345 na 0.021 na 0.075 29 27.0 21.0 7.5 241 

S18 8 9/12/2004 1510 na 0.028 na 0.083 79 29.0 21.5 6.4 468 

S18 8 9/13/2004 1425 na 0.039 na 0.016 71 31.0 21.7 6.1 441 

S19 8 9/13/2004 1240 na 0.073 na 0.014 2 27.0 21.0 6.6 59 

S20 8 9/12/2004 1535 < 0.007 na 0.051 19 33.0 21.0 7.2 153 

S20 8 9/13/2004 1210 na 0.014 na 0.059 19 27.0 19.5 7.2 153 

S22 8 9/13/2004 1410 na 0.041 na 0.041 38 26.0 22.0 7.4 108 

S23 8 9/12/2004 1630 < 0.007 na 0.056 15 26.0 19.0 7.2 162 

S23 8 9/13/2004 1530 < 0.007 na 0.059 12 27.5 17.5 7.3 153 

S24 8 9/12/2004 1635 < 0.007 na 0.060 19 26.0 19.0 7.2 175 

S24 8 9/13/2004 1545 < 0.007 na 0.059 18 27.5 19.0 7.3 170 

S29 8 9/12/2004 1425 na 0.036 na 0.011 43 29.0 21.8 7.0 376 

S29 8 9/13/2004 1415 na 0.032 na 0.080 51 28.0 21.5 7.0 392 

S31 8 9/12/2004 1500 na 0.019 na 0.016 21 26.0 22.0 6.6 156 

S35 8 9/12/2004 1315 na 0.026 na 0.127 85 28.5 22.7 7.4 457 

S37 8 9/12/2004 1600 < 0.007 na 0.088 7 20.0 20.0 7.4 150 

S37 8 9/14/2004 1054 na 0.014 na 0.101 7 24.0 nd 7.9 145 

S41 8 9/12/2004 1615 na 0.006 na 0.098 48 26.5 18.0 5.2 255 

S41 8 9/14/2004 1350 na 0.016 na 0.101 44 26.0 18.2 5.9 261 

S42 8 9/12/2004 1630 na 0.018 na 0.092 49 26.5 19.8 6.8 306 

S42 8 9/14/2004 1325 na 0.034 na 0.092 45 24.0 19.7 7.2 311 

S44 8 9/12/2004 1835 na 0.047 na 0.122 31 27.0 22.4 7.4 305 

S44 8 9/14/2004 1520 na 0.055 na 0.127 30 25.0 7.6 302 

S46 8 9/12/2004 1805 na 0.087 na 0.016 60 27.0 22.0 7.8 643 

S46 8 9/14/2004 1330 na 0.098 na 0.047 64 nd nd 7.9 728 

S47 8 9/12/2004 1900 na 0.017 na 0.016 155 23.0 20.8 8.0 698 

S47 8 9/14/2004 1647 na 0.037 na 0.060 114 24.5 21.2 7.1 600 

S48 8 9/12/2004 1715 na 0.007 na 0.151 131 26.5 19.3 7.5 601 

S48 8 9/14/2004 1607 na 0.028 na 0.158 104 24.0 19.4 6.9 500 

S5 8 9/12/2004 1110 na 0.009 na 0.080 23 23.0 18.9 6.3 208 

S5 8 9/13/2004 1005 na 0.010 na 0.091 25 23.0 18.5 6.2 214 

S50 8 9/12/2004 1800 na 0.024 na 0.137 74 26.5 20.5 6.2 373 

S50 8 9/14/2004 1510 na 0.063 na 0.107 70 24.5 20.0 6.8 345 

S51 8 9/12/2004 1430 na 0.032 na 0.167 86 26.0 21.3 7.4 505 

S51 8 9/14/2004 1530 na 0.045 na 0.165 82 26.0 21.1 7.5 513 

S52 8 9/12/2004 1050 na 0.038 na 0.056 30 26.5 19.6 6.9 231 

S52 8 9/13/2004 940 na 0.036 na 0.066 33 24.5 19.4 6.6 251 

S6 8 9/12/2004 1135 na 0.037 na 0.016 5 23.5 nd 7.1 147 

S6 8 9/13/2004 1040 na 0.045 na 0.016 34 26.5 19.5 6.6 266 

S7 8 9/12/2004 1200 na 0.007 na 0.087 27 25.5 19.5 7.0 257 

S7 8 9/13/2004 1120 na 0.009 na 0.092 29 26.0 19.5 6.9 253 

S8 8 9/12/2004 1210 na 0.018 na 0.005 34 26.0 19.1 6.3 328 

S8 8 9/13/2004 1135 na 0.019 na 0.051 32 26.0 18.9 6.3 319 

T18 8 9/12/2004 1100 na 0.014 na 0.016 33 24.5 20.4 6.0 242 

T18 8 9/13/2004 1315 na 0.012 na 0.069 36 27.0 21.7 6.6 257 

T22 8 9/12/2004 1125 na 0.028 na 0.269 35 28.0 20.7 7.2 295 

T22 8 9/13/2004 1034 na 0.031 na 0.443 37 23.0 19.6 6.0 299 

T23 8 9/12/2004 1150 na 0.017 na 0.100 53 28.0 20.3 6.8 320 

76 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

9.7 na 4.0 0.13 na 867 na nd nd e 3.295

7.0 na 6.0 0.13 na 167 na nd nd na nd

8.4 na 5.0 0.13 na 93 na nd nd e 0.006

7.4 na 2.0 0.13 na 3,500 na nd nd na nd

5.8 na 2.0 0.13 na 2,100 na nd nd e 0.037

4.0 na 4.0 0.00 e 600 na 625 nd e 0.000

8.0 na 3.0 0.13 e 2,075 na nd nd na nd

6.0 na 2.0 0.13 na 2,000 na nd nd e 0.015

6.6 na 1.0 0.13 na 210 na 203 nd e 0.037

8.0 na 1.0 0.25 na 1,775 na nd nd na nd

7.0 na 1.0 0.00 na 900 na nd nd e 0.033

8.0 na 2.0 0.13 e 627 na nd nd na nd

6.0 na 4.0 0.13 na 550 na 562 nd e 0.033

8.4 na 3.0 0.13 na 330 na nd nd na nd

8.8 na 4.0 0.13 na 340 na nd nd e 0.14

4.0 na 5.0 0.25 na 1,733 na nd nd na nd

7.4 na 2.0 0.13 na 1,533 na nd nd na nd

7.0 na 2.0 0.25 na 1,775 na nd yes na nd

7.0 na 1.0 0.00 na 608 na nd nd e 0.009

5.1 na 1.0 0.13 na 5,100 na nd nd na nd

4.8 na 2.0 0.00 e 12,900 na nd nd e 0.037

8.4 na 2.0 0.00 na 3,500 na nd nd na nd

9.1 na 3.0 0.00 na 1,200 na nd nd e 0.013

5.3 na 4.0 0.13 na 1,200 na nd nd na nd

7.0 na 3.0 0.13 na 100 na nd nd e 0.01

5.5 na 4.0 0.75 e 9,000 na nd yes na nd

5.0 na 2.0 0.25 na 2,400 na nd nd e 0.001

7.9 na 1.0 0.13 na 2,100 na nd nd na nd

7.3 na 1.0 0.13 na 933 na nd nd e 0.043

8.1 na 2.0 0.50 na 833 na nd nd na nd

8.6 na 4.0 0.13 na 508 na nd nd e 0.023

6.4 na 2.0 0.13 na 410 na nd nd na nd

7.2 na 6.0 0.13 na 584 na 420 nd e 0.035

7.1 na 6.0 0.50 na 420 na nd nd na nd

8.3 na 3.0 0.13 na 70 na nd nd e 0.073

7.4 na 1.0 0.13 na 2,200 na nd nd na nd

8.5 na 1.0 0.13 na 1,233 na nd nd e 0.061

5.0 na 7.0 0.13 na 833 na nd nd na nd

5.3 na 2.0 0.13 na 390 na nd nd e 0.011

8.0 na 10.0 1.50 e 22,000 na nd yes na nd

3.7 na 5.0 0.50 na 1,900 na nd nd e 0.001

7.4 na 8.0 0.13 na 1,133 na nd nd na nd

8.2 na 3.0 0.13 na 2,000 na nd nd e 0.033

5.3 na 9.0 7.50 na 1,067 na nd yes na nd

6.6 na 1.0 0.25 na 1,033 na nd nd e 0.01

3.0 na 26.0 0.25 e 1,975 na nd nd na nd

2.4 na 35.0 0.13 na 2,900 na nd nd e 0.017

8.5 na 7.0 0.25 na 2,000 na nd nd na nd

7.2 na 6.0 0.25 na 1,300 na 1,767 nd e 0.17

6.8 na 7.0 0.25 na 2,500 na nd yes na nd

Appendixes 77
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

T23 8 9/13/2004 939 na 0.020 na 0.113 55 23.5 19.7 6.0 317 

T23A1 8 9/12/2004 1220 na 0.018 na 0.122 55 27.0 20.1 6.8 336 

T23A1 8 9/13/2004 1145 na 0.025 na 0.097 58 25.5 20.1 7.3 335 

T23A2 8 9/12/2004 1240 na 0.017 na 0.102 55 28.5 20.9 6.8 348 

T23A2 8 9/13/2004 1226 na 0.019 na 0.099 59 27.0 20.5 6.2 342 

T24 8 9/12/2004 1455 na 0.015 na 0.091 58 28.5 21.6 6.7 358 

T24 8 9/13/2004 1350 na 0.020 na 0.090 64 31.0 21.8 6.2 357 

T24A1 8 9/12/2004 1245 na 0.022 na 0.076 80 24.0 20.0 7.2 414 

T24A1 8 9/13/2004 1501 na 0.025 na 0.027 80 29.5 20.6 6.3 404 

T24A2 8 9/12/2004 1335 na 0.024 na 0.062 79 26.5 20.8 7.0 338 

T24A2 8 9/13/2004 1621 na 0.104 na 0.051 108 29.0 22.1 6.1 417 

T24B1 8 9/12/2004 1305 na 0.021 na 0.017 80 26.5 20.1 7.1 237 

T24B1 8 9/13/2004 1548 na 0.024 na 0.015 81 29.5 21.0 6.4 399 

T25 8 9/12/2004 1600 na 0.014 na 0.016 44 30.0 20.3 6.6 396 

T25 8 9/13/2004 1315 na 0.021 na 0.056 71 25.5 20.6 7.1 380 

T25A 8 9/12/2004 1355 na 0.008 na 0.059 25 24.0 20.9 7.5 178 

T25A 8 9/13/2004 1455 na 0.010 na 0.054 24 26.5 21.6 7.5 155 

T29 8 9/12/2004 1715 na 0.015 na 0.054 31 26.0 20.4 6.7 228 

T29 8 9/14/2004 1240 na 0.031 na 0.061 39 25.0 19.8 7.2 161 

T3 8 9/12/2004 1020 na 0.019 na 0.107 40 25.0 18.9 6.7 221 

T3 8 9/13/2004 915 na 0.024 na 0.113 42 25.0 18.1 6.2 220 

T31 8 9/12/2004 1215 na 0.018 na 0.059 56 27.0 20.6 6.3 304 

T31 8 9/14/2004 850 na 0.022 na 0.085 93 22.5 19.7 6.8 419 

T31A1 8 9/12/2004 1515 na 0.015 na 0.061 73 26.0 21.1 7.1 356 

T31A1 8 9/14/2004 926 na 0.026 na 0.090 105 21.5 19.8 6.2 455 

T33 8 9/12/2004 1540 na 0.013 na 0.106 57 26.5 21.3 7.2 361 

T33 8 9/14/2004 1022 na 0.027 na 0.101 58 24.5 20.0 6.6 363 

T35 8 9/12/2004 1330 na 0.015 na 0.081 51 26.5 20.8 6.4 265 

T35 8 9/14/2004 1005 na 0.028 na 0.090 58 24.5 19.7 7.0 319 

T35A 8 9/12/2004 1345 na 0.011 na 0.079 51 26.0 20.0 6.4 292 

T35A 8 9/14/2004 1045 na 0.020 na 0.092 58 23.5 19.9 7.0 306 

T36 8 9/12/2004 1415 na 0.011 na 0.066 45 25.5 19.8 6.1 260 

T36 8 9/14/2004 1120 na 0.023 na 0.073 49 23.5 19.1 6.7 270 

T37 8 9/12/2004 1015 na 0.016 na 0.016 24 23.5 20.8 6.7 183 

T37 8 9/14/2004 1257 na 0.023 na 0.050 28 25.5 21.8 7.5 192 

T38 8 9/12/2004 1500 < 0.007 na 0.055 10 28.0 25.3 7.5 110 

T38 8 9/14/2004 1200 na 0.016 na 0.054 12 25.0 22.8 7.1 112 

T40 8 9/12/2004 1515 na 0.014 na 0.016 29 26.5 20.3 6.7 188 

T40 8 9/14/2004 1220 na 0.025 na 0.051 31 nd 19.8 7.0 194 

T42 8 9/12/2004 1530 na 0.007 na 0.051 39 28.5 20.9 6.3 217 

T42 8 9/14/2004 1250 na 0.021 na 0.055 35 24.0 20.1 6.9 211 

T44 8 9/12/2004 1850 na 0.023 na 0.045 23 26.0 22.8 8.1 210 

T44 8 9/14/2004 1129 na 0.032 na 0.051 20 24.0 21.5 8.5 202 

T50 8 9/12/2004 1825 na 0.011 na 0.086 171 28.0 22.8 7.5 714 

T50 8 9/14/2004 1410 na 0.022 na 0.092 173 26.0 21.1 7.6 718 

T51 8 9/12/2004 1640 na 0.014 na 0.070 61 24.5 22.6 7.1 363 

T51 8 9/14/2004 1425 na 0.029 na 0.108 57 25.0 22.0 7.1 315 

T51A 8 9/12/2004 1720 na 0.015 na 0.060 50 27.5 23.0 6.9 328 

T51A 8 9/14/2004 1550 na 0.036 na 0.060 74 26.0 22.0 7.1 325 

T51B 8 9/12/2004 1700 na 0.014 na 0.060 49 27.5 23.3 7.4 331 

78 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

6.1 na 3.0 0.25 na 1,500 na 1,133 nd e 0.494

8.1 na 4.0 0.13 na 1,700 na nd nd na nd

7.1 na 2.0 0.00 na 1,133 na 1,775 nd e 1.685

10.3 na 6.0 0.13 na 1,775 na nd nd na nd

8.9 na 3.0 0.13 na 2,200 na nd nd e 0.462

8.5 na 4.0 0.13 na 3,500 na nd yes na nd

7.6 na 4.0 0.13 na 2,000 na nd nd e 0.484

7.2 na 3.0 0.25 na 1,300 na nd nd na nd

6.8 na 3.0 0.25 na 1,850 na nd nd e 0.08

5.9 na 8.0 0.13 na 2,500 na nd nd na nd

5.5 na 6.0 0.13 e 8,600 na nd nd e 0.124

6.9 na 6.0 0.13 na 2,100 na nd nd na nd

6.5 na 4.0 0.13 na 3,100 na nd nd e 0.196

5.6 na 4.0 0.13 na 2,025 na nd nd na nd

5.5 na 6.0 0.13 na 1,750 na nd nd e 0.1

7.1 na 2.0 0.13 na 1,033 na nd nd na nd

7.3 na 2.0 0.00 na 1,567 na nd nd e 0.053

8.6 na 2.0 0.25 na 1,667 na nd nd na nd

8.4 na 2.0 0.38 e 6,300 na nd yes e 0.057

6.1 na 3.0 0.13 na 1,633 na nd nd na nd

6.1 na 2.0 0.13 na 1,600 na nd nd e 0.035

6.2 na 13.0 0.13 na 2,800 na nd nd na nd

6.2 na 9.0 0.13 na 1,533 na nd nd na nd

7.2 na 8.0 0.25 na 2,600 na nd nd na nd

7.0 na 6.0 0.13 na 1,233 na 1,133 nd e 0.279

5.8 na 2.0 0.13 na 2,200 na nd nd na nd

6.0 na 1.0 0.38 na 1,300 na 1,167 nd e 0.06

7.3 na 2.0 0.50 e 48,000 na nd yes na nd

7.3 na 4.0 0.25 na 4,900 na 5,900 nd e 0.163

7.4 na 3.0 0.25 e 10,700 na nd nd na nd

7.9 na 2.0 0.25 e 7,000 na nd nd e 0.108

7.6 na 3.0 0.13 na 1,400 na nd yes na nd

8.2 na 2.0 0.00 na 1,133 na nd nd e 0.093

7.5 na 4.0 0.13 e 686 na nd nd na nd

9.1 na 3.0 0.13 na 260 na nd nd e 0.288

7.3 na 4.0 0.25 e 721 na nd nd na nd

8.7 na 3.0 0.13 na 73 na nd nd e 0.167

7.2 na 5.0 0.25 e 182 na nd nd na nd

8.0 na 3.0 0.00 na 110 na nd nd e 0.014

6.2 na 4.0 0.13 na 2,500 na nd nd na nd

6.3 na 2.0 0.00 na 1,633 na nd nd e 0.085

8.9 na 1.0 0.13 na 2,600 na nd nd na nd

10.4 na 1.0 0.00 na 933 na nd nd na nd

11.4 na 8.0 0.13 na 2,700 na nd nd na nd

9.2 na 7.0 0.13 na 1,233 na nd nd e 0.209

6.5 na 5.0 0.87 e 8,400 na nd yes na nd

6.9 na 3.0 0.25 na 6,000 na nd nd e 0.186

7.0 na 5.0 3.00 e 24,000 na nd nd na nd

4.0 na 7.0 2.50 e 11,100 na nd yes e 0.255

6.8 na 7.0 5.00 e 24,000 na nd yes na nd

Appendixes 79
Appendix 1.  Indicator tracer data from synoptic sampling events for sites sampled in the Accotink Creek watershed, Virginia. — Continued

[rem, remark; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter; NTU, nephelometric turbidity units; col/10 0mL, colonies per 100 milliliters; 

ft3/s, cubic feet per second; na, not applicable; nd, not determined]

Site ID Event Sampling 

date

Sampling 

time Bo rem Boron (mg/L) Br rem Bromide (mg/L)

Chloride 

(mg/L)

Air 

temp

Water 

temp pH

Specific 

conductance 

(μS/cm)

T51B 8 9/14/2004 1450 na 0.027 na 0.058 43 25.0 22.5 7.3 326 

T51BLD 8 9/14/2004 1500 na 0.031 < 0.250 67 nd nd nd nd 

T51C 8 9/12/2004 1750 na 0.007 na 0.094 56 27.0 21.0 6.6 264 

T51C 8 9/14/2004 1630 na 0.020 na 0.090 53 24.0 21.0 7.1 253 

T55 8 9/12/2004 1730 na 0.024 na 0.071 58 28.0 21.6 7.6 331 

T55 8 9/14/2004 1425 na 0.040 na 0.117 60 25.0 20.6 7.2 344 

T56 8 9/12/2004 1745 na 0.008 na 0.065 33 26.0 21.0 7.2 268 

T56 8 9/14/2004 1440 na 0.027 na 0.072 34 25.0 20.1 7.1 273 

80 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Dissolved 

oxygen 

(mg/L)

Turbidity 

rem

Turbidity 

(NTU)

Surfactants 

(mg/L) FC rem

Fecal 

coliform 

bacteria 

(col/100 mL)

Dup FC 

rem

Fecal coliform bacteria 

duplicate 

(col/100 mL)

Organics Discharge 

rem

Discharge 

(ft3/s)

7.2 na 3.0 1.50 e 10,400 na nd nd e 0.165

nd na 229.0 25.00 e 4,000,000 na nd yes na nd

6.0 na 6.0 0.37 na 4,200 na nd nd na nd

6.0 na 4.0 0.13 na 2,800 na nd nd e 0.005

7.4 na 1.0 0.13 na 1,450 na nd nd na nd

7.3 na 2.0 0.13 na 2,100 na nd nd e 0.122

7.3 na 13.0 0.25 na 1,100 na nd nd na nd

7.9 na 2.0 0.00 na 2,000 na nd nd e 0.071

Appendixes 81
Appendix 2.  Confirmatory wastewater organic compound data from each synoptic sampling event in the Accotink Creek watershed,

Virginia. — Continued

[mg/L, milligrams per liter; PCODE, U.S. Geological Survey parameter code; nd, not detected; --, not available; light gray shading indicates quantitative 

concentration; dark gray shading indicates estimated concentration]

Event 3

Compound (mg/L) PCODE Log Kow S12 S15 S3 T24 T6 T9 NCP1 NCP4

Caffeine 81436Z 0.16 nd nd 0.12 nd 0.097 0.061 36 160

Cotinine 61945Z 0.34 nd nd 0.21 0.18 nd nd 1 nd

Diethyl phthalate (DEP) 34336B 2.82 nd nd 6 nd nd nd 6.8 11

Diethylhexyl phthalate (DEHP) 39100C 8.39 nd nd nd nd nd nd 3.5 5.5

Galaxolide (HHCB) 62823Z 6.26 nd nd nd nd nd nd 0.77 5.8

Menthol 62827Z 3.38 nd nd 0.57 nd nd nd 18 18

NPEO1-total 61704A -- nd nd 1.2 nd nd nd 12 31

NPEO2-total 61703Z -- nd nd 1.7 nd nd nd 9.9 24

OPEO1 61706Z -- nd nd nd nd nd nd 1.8 nd

para-Nonylphenol (total NP) 62829Z 5.92 nd nd 1 nd 0.65 0.56 36 59

Skatol 62807Z 2.60 nd nd nd nd nd nd 1 38

Tonalide (AHTN) 62812Z 6.35 nd nd 0.043 nd nd nd 3.8 8.2

Triclosan 61708Z 4.66 nd nd nd nd nd nd 5.2 6.8

Number of detections 0 0 8 1 2 2 13 11

Event 4

Compound (mg/L) PCODE Log Kow A15 S29 S3 S44 S46 S48 S50 S51 T13 T16 T24 T31 T35 

Caffeine 81436Z 0.16 0.06 0.34 nd 0.57 0.18 nd nd 0.065 27 nd 0.069 0.065 0.097 

Cotinine 61945Z 0.34 nd nd nd nd nd nd nd nd 0.78 nd nd nd nd 

Diethyl phthalate (DEP) 34336B 2.82 nd nd nd nd 1.5 nd nd nd 5.2 nd nd nd nd 

Diethylhexyl phthalate (DEHP) 39100C 8.39 4.3 nd nd 8.4 nd nd nd nd 3 2.2 3.7 46 nd 

Galaxolide (HHCB) 62823Z 6.26 nd nd nd nd nd nd nd nd 0.51 nd nd nd 0.051 

Menthol 62827Z 3.38 nd nd nd nd nd nd 0.17 nd 15 nd nd nd nd 

NPEO1-total 61704A -- nd nd nd nd 1.7 nd 0.88 nd 18 nd nd nd 1.3 

NPEO2-total 61703Z -- 2.5 nd nd 1.6 6.9 1 4.5 1.1 7.5 nd nd 1.5 3.1 

OPEO1 61706Z -- nd nd nd nd nd nd nd nd 1.7 nd nd nd nd 

para-Nonylphenol (total NP) 62829Z 5.92 nd nd nd 1.6 3.3 nd nd nd 19 nd nd nd 2.8 

Skatol 62807Z 2.60 nd nd nd nd 0.29 nd nd nd 0.66 nd nd nd nd 

Tonalide (AHTN) 62812Z 6.35 nd nd nd nd nd nd nd nd 2.2 nd nd nd 0.13 

Triclosan 61708Z 4.66 nd 0.16 nd nd nd nd nd 0.2 2.7 nd nd nd 0.26 

Number of detections 3 2 0 4 6 1 3 3 13 1 2 3 7 

Event 5

Compound (mg/L) PCODE Log Kow A13 A14 A15 A16 S15 S18 S20 S23 S29 S35 S37 S41 S42 

Caffeine 81436Z 0.16 nd 0.079 0.08 0.048 nd 0.06 nd nd nd nd nd 0.32 nd 

Cotinine 61945Z 0.34 nd nd nd nd nd nd nd nd nd nd nd 0.22 nd 

Diethyl phthalate (DEP) 34336B 2.82 nd nd nd nd nd nd nd nd nd nd nd nd nd 

Diethylhexyl phthalate (DEHP) 39100C 8.39 nd nd nd 0.38 0.84 nd nd nd nd nd nd nd 2.4 

Galaxolide (HHCB) 62823Z 6.26 nd nd nd nd nd nd nd nd nd nd nd nd nd 

Menthol 62827Z 3.38 nd nd nd nd nd nd nd nd nd nd nd nd nd 

NPEO1-total 61704A -- nd nd nd nd nd nd nd nd nd nd nd nd nd 

NPEO2-total 61703Z -- nd nd nd nd nd nd 2.6 nd nd nd nd nd nd 

OPEO1 61706Z -- nd nd nd nd nd nd nd nd nd nd nd nd nd 

para-Nonylphenol (total NP) 62829Z 5.92 nd nd nd nd nd nd 0.79 nd nd nd nd nd nd 

Skatol 62807Z 2.60 0.019 nd nd nd nd nd nd nd nd 0.014 nd 0.026 nd 

Tonalide (AHTN) 62812Z 6.35 nd nd nd nd nd nd nd nd nd nd nd nd nd 

Triclosan 61708Z 4.66 nd nd nd nd nd nd nd nd 0.22 nd nd nd nd 

Number of detections 1 1 1 2 1 1 3 0 1 1 0 3 1 

82 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
T4 T47 T50 T51 T9

nd nd nd 0.12 nd

nd nd nd nd nd

nd nd nd 0.55 nd

nd nd 4.1 nd nd

nd nd nd nd nd

nd nd nd nd nd

nd nd nd 0.98 nd

nd nd nd 4.1 nd

nd nd nd nd nd

nd nd nd 1.3 nd

nd nd nd nd nd

nd nd nd nd nd

nd nd nd nd nd

 0 0 1 5 0

S44 S46 S48 S50 S51 S8 T13 T22 T24 T31 T33 T35 T36 T40 T48 T50 T51 T55 T56 T9 T13A

4.3 0.27 0.19 0.18 0.29 nd nd nd 0.064 0.076 nd 0.061 nd nd 0.079 nd 0.047 0.074 nd nd nd

nd nd 0.24 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

nd nd 0.3 nd nd 0.32 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

0.41 nd 1.2 nd nd 1.6 nd nd 4.2 nd nd nd nd 1.1 nd nd nd 8.5 nd nd nd

nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

nd 0.62 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

2.5 2.8 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

nd 0.18 0.17 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

1.6 1.4 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

nd nd nd nd nd 0.066 nd nd 0.014 0.015 0.015 0.028 nd nd nd 0.013 nd nd nd 0.034 nd

nd nd nd nd nd nd nd nd nd nd nd 0.13 nd nd nd nd nd nd nd nd nd

nd nd nd nd nd 0.11 nd nd nd nd nd nd nd nd nd nd nd nd nd nd nd

4 5 5 1 1 4 0 0 3 2 1 3 0 1 1 1 1 2 0 1 0

Appendixes 83
Appendix 2.  Confirmatory wastewater organic compound data from each synoptic sampling event in the Accotink Creek watershed,

Virginia. — Continued

[mg/L, milligrams per liter; PCODE, U.S. Geological Survey parameter code; nd, not detected; --, not available; light gray shading indicates quantitative 

concentration; dark gray shading indicates estimated concentration]

Event 6

Compound (mg/L) PCODE Log Kow A13 S18 S20 S29 S5 S6 S7 S8 T23 T24 T25 T31

Caffeine 81436Z 0.16 0.081 0.018 0.045 0.2 nd 0.74 nd 0.025 0.068 0.068 0.02 0.094

Cotinine 61945Z 0.34 nd nd nd nd nd 0.28 nd nd nd nd nd 0.2

Diethyl phthalate (DEP) 34336B 2.82 nd 0.1 0.096 0.052 nd 0.23 nd 0.11 nd nd 0.077 nd

Diethylhexyl phthalate (DEHP) 39100C 8.39 2.2 nd nd 1.7 nd nd nd nd nd nd nd nd

Galaxolide (HHCB) 62823Z 6.26 0.052 nd 0.072 nd nd nd nd nd nd nd nd 0.063

Menthol 62827Z 3.38 nd nd nd nd nd nd nd nd nd nd nd nd

NPEO1-total 61704A -- nd nd 1.4 nd nd 3.7 nd nd nd 0.71 nd 0.77

NPEO2-total 61703Z -- nd nd 4.7 nd nd 7.4 nd nd nd 1.8 nd 1.5

OPEO1 61706Z -- nd nd 0.62 nd nd nd nd nd nd nd nd nd

para-Nonylphenol (total NP) 62829Z 5.92 nd nd 1.5 nd 0.74 nd 0.85 0.77 0.8 0.9 nd 0.79

Skatol 62807Z 2.60 0.04 0.04 nd nd 0.014 0.2 0.014 0.024 0.039 0.057 0.14 0.023

Tonalide (AHTN) 62812Z 6.35 0.014 nd 0.017 nd nd nd nd nd nd nd nd nd

Triclosan 61708Z 4.66 nd nd 0.045 1 nd nd nd nd nd nd nd nd

Number of detections 5 3 9 4 2 6 2 4 3 5 3 7

Event 7

Compound (mg/L) PCODE Log Kow A15B A6 S3 S44 S46 S51 S6 S7 T22 T23 T23A1 T24 T24 

Caffeine 81436Z 0.16 0.22 0.3 nd 0.11 0.29 0.12 0.64 0.019 0.024 0.15 0.084 0.066 0.18 

Cotinine 61945Z 0.34 nd nd nd 0.17 0.16 0.16 0.24 nd nd nd nd nd nd 

Diethyl phthalate (DEP) 34336B 2.82 nd nd nd 0.64 0.16 nd 0.32 0.098 0.12 0.22 0.12 0.08 nd 

Diethylhexyl phthalate (DEHP) 39100C 8.39 nd nd nd nd 2.4 nd 0.73 nd nd nd nd 1.4 nd 

Galaxolide (HHCB) 62823Z 6.26 nd 0.044 nd nd 0.04 nd 0.044 nd 0.043 0.045 0.043 nd nd 

Menthol 62827Z 3.38 nd 0.062 0.056 0.078 0.17 nd 0.34 0.05 nd 0.05 0.046 0.05 nd 

NPEO1-total 61704A -- 0.55 0.66 nd 1.2 0.71 nd 0.76 nd nd nd nd nd nd 

NPEO2-total 61703Z -- nd 0.41 nd 3.8 2 nd 0.87 nd nd nd nd nd nd 

OPEO1 61706Z -- nd nd nd nd nd nd 0.42 nd nd nd nd nd nd 

para-Nonylphenol (total NP) 62829Z 5.92 0.87 0.91 1 1.8 1.4 0.95 1.1 0.96 0.85 0.93 0.94 1.2 0.86 

Skatol 62807Z 2.60 nd 0.009 nd nd 0.007 nd 0.046 0.004 nd 0.005 0.008 0.007 0.009 

Tonalide (AHTN) 62812Z 6.35 nd 0.036 nd nd 0.011 nd 0.023 nd nd nd nd nd nd 

Triclosan 61708Z 4.66 nd 0.052 nd nd nd 0.096 nd nd 0.05 nd nd nd nd 

Number of detections 3 9 2 7 11 4 12 5 5 6 6 6 3 

Event 8

Compound (mg/L) PCODE Log Kow A15 A6 S37 S46 S6 S8 T23 T24 T29 T35 T36 T51 T51B 

Caffeine 81436Z 0.16 0.028 0.046 0.009 0.089 0.1 0.21 nd 0.056 0.015 0.04 nd 0.22 0.87 

Cotinine 61945Z 0.34 0.17 0.17 nd 0.19 0.22 nd nd nd nd 0.19 nd 0.22 nd 

Diethyl phthalate (DEP) 34336B 2.82 0.036 nd nd 0.49 0.072 0.29 0.12 nd 0.053 0.04 nd 0.42 0.65 

Diethylhexyl phthalate (DEHP) 39100C 8.39 nd 0.26 nd nd nd 1.3 nd 1.7 nd nd nd 0.34 2.5 

Galaxolide (HHCB) 62823Z 6.26 nd nd nd 0.048 nd 0.053 nd nd nd 0.055 nd nd nd 

Menthol 62827Z 3.38 nd nd nd 0.15 nd 0.16 nd nd nd 0.058 nd 0.089 nd 

NPEO1-total 61704A -- 0.54 nd nd 0.8 nd 0.94 nd nd nd 0.58 nd 1.3 6.6 

NPEO2-total 61703Z -- 1.1 nd nd 1.5 nd 4.2 1.1 1.6 nd 1.2 nd 4.5 9 

OPEO1 61706Z -- 0.27 nd nd 0.29 nd 0.31 nd nd nd 0.26 nd nd 0.34 

para-Nonylphenol (total NP) 62829Z 5.92 0.81 0.76 nd 2.1 nd nd 0.79 0.86 nd 0.88 nd 1.2 2.2 

Skatol 62807Z 2.60 nd nd 0.006 nd nd nd 0.007 nd nd 0.011 nd nd nd 

Tonalide (AHTN) 62812Z 6.35 0.033 nd nd 0.025 nd 0.12 nd nd nd 0.088 nd nd nd 

Triclosan 61708Z 4.66 nd nd nd nd nd 0.19 nd nd nd 0.11 nd 0.11 8.1 

Number of detections 8 4 2 10 3 10 4 4 2 12 0 9 8 

84 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
T35A T36 T51 T51 T56

0.078 0.024 2.1 2.1 0.052

0.14 nd 0.19 0.16 0.14

0.12 0.1 0.28 0.12 nd

nd nd nd nd nd

0.042 nd nd 0.042 nd

0.27 nd 0.13 0.1 nd

nd nd 1.2 0.72 nd

nd nd 1.2 0.55 nd

nd nd nd nd nd

0.86 0.87 1.2 1 0.9

0.008 0.003 0.019 0.03 nd

0.045 nd nd nd nd

0.057 nd nd nd nd

9 4 8 9 3

T51BLD T51A

2.8 0.32

3.2 0.2

1.2 2.2

24 2.3

nd nd

2.1 nd

4 29

14 22

2.3 0.32

5 1.8

0.11 0.017

nd nd

0.24 0.32

11 10

Appendixes 85
Appendix 3.  Cross-reference listing of study site identifications and official USGS site identifications in the Accotink

Creek watershed of Virginia, including site names and coordinates. — Continued

[Latitude and longitude in decimal degrees. Station locations shown in figure 3. Sites are ordered by site number, from upstream to downstream]

Site Site number Station name Latitude Longitude

T57 0165388130 ACCOTINK CREEK AT CEDAR AVENUE AT FAIRFAX, VA 385110.97 771853.97

T56 0165388205 ACCOTINK CREEK AB CHAIN BRIDGE RD AT FAIRFAX, VA 385103.19 771829.37

S51 0165388210 STORM DRAIN AT HALLMAN STREET AT FAIRFAX, VA 385102.13 771916.42

S50 0165388250 STORM DRAIN AT MAIN STREET AT FAIRFAX, VA 385053.50 771843.78

S49 0165388255 STORM DRAIN ABOVE PAGE AVENUE AT FAIRFAX, VA 385043.05 771840.62

T55 0165388290 ACCOTINK CR TRIB 1 AT CHAIN BR ROAD AT FAIRFAX, VA 385102.64 771829.19

S48 0165388320 STORM DRAIN AT KENMORE DRIVE AT FAIRFAX, VA 385103.89 771820.35

T53 0165388460 ACCOTINK CREEK AT DALE DRIVE AT FAIRFAX, VA 385126.21 771753.40

T45 0165388630 ACCOTINK CREEK BELOW STAFFORD DRIVE AT FAIRFAX, VA 385153.36 771717.69

S47 0165388695 STORM DRAIN AT OAKTON PARK AT FAIRFAX, VA 385157.50 771820.51

T52 0165388705 ACCOTINK CR TRIB 2 AT OAKTON PARK AT FAIRFAX, VA 385156.45 771820.89

T50 0165388740 ACCOTINK CR TRIB 2 BL EATON PLACE AT FAIRFAX, VA 385142.05 771801.34

T54 0165388785 ACCOTINK CR TRIB 1 TRIB 2 AT ORCHRD AT FAIRFAX, VA 385133.25 771836.03

T51BLD 0165388795 ACCOTINK CR TRIB 1 TO TRIB 1 TO 2 AT FAIRFAX, VA 385128.15 771836.09

T51C 0165388840 ACCOTINK CR TRIB 1 TRIB 2 BL CHN BR AT FAIRFAX, VA 385128.15 771821.51

T51A 0165388845 ACCOTINK CR TRIB 1 TRIB 2 NR EATON AT FAIRFAX, VA 385134.60 771817.17

T51B 0165388850 ACCOTINK CR TRIB 1 TRIB 2 AB EATON AT FAIRFAX, VA 385134.73 771816.14

T51 0165388880 ACCOTINK CR TRIB 1 TRIB 2 AT MOUTH AT FAIRFAX, VA 385141.95 771801.34

S46 0165388895 STORM DRAIN AT LEE HIGHWAY AT FAIRFAX, VA 385141.12 771755.67

T48 0165388995 ACCOTINK CR TRIB 2 BL STAFFORD DR AT FAIRFAX, VA 385157.54 771722.46

T49 0165389060 ACCOTINK CR TRIB 2 TO TRIB 2 AT FAIRFAX, VA 385211.02 771749.70

T47 0165389120 ACCOTINK CR TRIB 2 TRIB 2 AT MOUTH AT FAIRFAX, VA 385159.68 771722.24

T46 0165389140 ACCOTINK CREEK TRIB 2 AT MOUTH AT FAIRFAX, VA 385156.32 771716.62

A16A1 0165389205 ACCOTINK CREEK NEAR RANGER ROAD AT FAIRFAX, VA 385153.52 771709.15

A16 0165389220 ACCOTINK CREEK ABOVE LEE HIGHWAY AT FAIRFAX, VA 385152.13 771702.13

S45 0165389225 STORM DRAIN AT STRATHAVEN PLACE AT FAIRFAX, VA 385239.49 771725.31

T44 0165389250 ACCOTINK CREEK TRIB 3 AT PLATTEN DR AT FAIRFAX, VA 385229.29 771716.02

S44 0165389360 STORM DRAIN BELOW BEECH DRIVE AT FAIRFAX, VA 385157.35 771657.19

T43 0165389380 ACCOTINK CREEK TRIB 3 AT MOUTH AT FAIRFAX, VA 385153.05 771659.75

A15A2 0165389420 ACCOTINK CREEK BELOW ARLINGTON BLVD AT FAIRFAX, VA 385147.37 771651.77

S43 0165389440 STORM DRAIN AT GREAT OAKS WAY AT FAIRFAX, VA 385146.22 771645.97

A15A1 0165389450 ACCOTINK CREEK ABOVE OLD LEE HWY AT FAIRFAX, VA 385144.56 771642.76

A15B 0165389480 ACCOTINK CREEK BELOW OLD LEE HWY AT FAIRFAX, VA 385140.82 771636.87

A15 0165389490 ACCOTINK CREEK ABOVE DANIELS RUN AT FAIRFAX, VA 385138.83 771634.20

S42 0165389605 STORM DRAIN BELOW MAIN STREET AT FAIRFAX, VA 385046.38 771801.99

S41 0165389615 STORM DRAIN AT COVER PLACE AT FAIRFAX, VA 385045.39 771747.82

T42 0165389680 DANIELS RUN AT HERITAGE LANE AT FAIRFAX, VA 385104.90 771723.68

S40 0165389685 STORM DRAIN AT HERITAGE LANE AT FAIRFAX, VA 385106.84 771724.24

S39 0165389710 STORM DRAIN AT EMBASSY LANE AT FAIRFAX, VA 385108.25 771715.33

T41 0165389715 DANIELS RUN AT EMBASSY LANE AT FAIRFAX, VA 385105.97 771712.00

T40 0165389730 DANIELS RUN TRIBUTARY 1 AT MOUTH AT FAIRFAX, VA 385104.00 771710.00

S38 0165389740 STORM DRAIN AT ESTEL ROAD AT FAIRFAX, VA 385101.52 771657.90

T39 0165389770 DANIELS RUN AT ST ANDREWS DRIVE AT FAIRFAX, VA 385110.00 771646.00

T38 0165389785 DANIELS RUN TRIBUTARY 2 AT MOUTH AT FAIRFAX, VA 385111.60 771644.90

T37 0165389890 DANIELS RUN AT MOUTH AT FAIRFAX, VA 385135.68 771632.52

86 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Appendix 3.  Cross-reference listing of study site identifications and official USGS site identifications in the Accotink

Creek watershed of Virginia, including site names and coordinates. — Continued

[Latitude and longitude in decimal degrees. Station locations shown in figure 3. Sites are ordered by site number, from upstream to downstream]

Site Site number Station name Latitude Longitude

A14A 0165389920 ACCOTINK CREEK ABOVE PICKETT ROAD AT FAIRFAX, VA 385138.24 771626.13

A14 01653900 ACCOTINK CREEK AT PICKETT ST AT FAIRFAX, VA 385139.00 771617.00

S36 0165390048 STORM DRAIN BELOW PICKETT ROAD AT FAIRFAX, VA 385141.44 771611.75

S35 0165390050 STORM DRAIN AT OLD PICKETT ROAD AT FAIRFAX, VA 385143.84 771613.16

S37 0165390230 STORM DRAIN ABOVE SUTTON ROAD AT FAIRFAX, VA 385240.27 771650.31

T36 0165390505 ACCOTINK CR TRIB 4 ABOVE LEE HWY AT FAIRFAX, VA 385205.56 771622.02

T35A 0165390670 ACCOTINK CR TRIB 4 BL ARLINGTON AT FAIRFAX, VA 385150.95 771611.39

T35 0165390730 ACCOTINK CREEK TRIB 4 AT MOUTH AT FAIRFAX, VA 385145.09 771610.87

A13A 0165390845 ACCOTINK CREEK AB MILL SPRINGS DR AT FAIRFAX, VA 385142.55 771559.72

A13B 0165390850 ACCOTINK CREEK NEAR MILL SPRINGS DR AT FAIRFAX, VA 385141.39 771559.14

S34 0165390890 STORM DRAIN AT MILL SPRINGS DRIVE AT FAIRFAX, VA 385137.39 771558.02

A13 0165391005 ACCOTINK CREEK ABOVE EDENVALE ROAD AT FAIRFAX, VA 385139.08 771546.37

T34 0165391120 ACCOTINK CR TRIB 5 AB TAPAWINGO RD AT VIENNA, VA 385308.98 771615.29

T33 0165391150 ACCOTINK CR TRIB 1 TRIB 5 AT MOUTH AT VIENNA, VA 385308.98 771615.08

T32 0165391460 ACCOTINK CREEK TRIB 5 AT HERMOSA DR AT VIENNA, VA 385225.11 771552.56

T31A2 0165391505 ACCOTINK CREEK TRIB 5 BELOW LEE HWY NR FAIRFAX, VA 385216.25 771551.04

S33 0165391550 STORM DRAIN AT NUTLEY STREET AT FAIRFAX, VA 385212.87 771548.48

S32 0165391580 STORM DRAIN ABOVE BARRICK STREET AT FAIRFAX, VA 385206.83 771546.84

S31 0165391630 STORM DRAIN AT BARRICK STREET AT FAIRFAX, VA 385201.77 771545.43

T31A1 0165391660 ACCOTINK CREEK TRIB 5 AB ARLINGTON NR FAIRFAX, VA 385158.08 771548.05

T31 0165391805 ACCOTINK CREEK TRIB 5 AT MOUTH NEAR FAIRFAX, VA 385142.13 771542.69

A12 0165392005 ACCOTINK CREEK ABOVE BARKLEY DRIVE AT FAIRFAX, VA 385133.38 771524.12

S28 0165392098 STORM DRAIN BELOW COTTAGE STREET AT VIENNA, VA 385306.22 771511.50

T28 0165392145 BEAR BRANCH AT WARE STREET AT VIENNA, VA 385247.02 771510.06

S30 0165392148 STORM DRAIN AT ONONDIO CIRCLE AT VIENNA, VA 385349.00 771439.00

S27 0165392298 STORM DRAIN NEAR PATRICK STREET AT VIENNA, VA 385300.96 771458.63

T30 0165392305 BEAR BRANCH TRIB 1 BELOW COTTAGE ST AT VIENNA, VA 385300.99 771458.67

T29 0165392338 BEAR BRANCH TRIB 1 AT MOUTH AT VIENNA, VA 385247.84 771507.89

T27A 0165392363 BEAR BRANCH AT ALBANY COURT AT VIENNA, VA 385240.60 771513.26

T27 0165392387 BEAR BRANCH ABOVE HUNTER ROAD AT VIENNA, VA 385229.73 771515.03

S25 0165392390 STORM DRAIN 1 AT ESPANA COURT AT VIENNA, VA 385229.10 771510.65

S26 0165392395 STORM DRAIN 2 AT ESPANA COURT AT VIENNA, VA 385225.99 771510.64

T60 0165393045 BEAR BRANCH NEAR KAREN DRIVE NEAR FAIRFAX, VA 385139.60 771522.53

T26 0165393070 ACCOTINK CREEK ABOVE BARKLEY DRIVE NR FAIRFAX, VA 385133.61 771520.27

A11 0165394250 ACCOTINK CR ABOVE PROSPERITY AVE NEAR FAIRFAX, VA 385114.69 771458.76

S24 0165394258 STORM DRAIN 1 BELOW STONEWALL DRIVE AT VIENNA, VA 385319.27 771405.38

S23 0165394260 STORM DRAIN 2 BELOW STONEWALL DRIVE AT VIENNA, VA 385319.27 771405.34

T25A 0165394490 LONG BRANCH BELOW COTTAGE STREET AT VIENNA, VA 385303.24 771412.43

T61 0165394660 LONG BRANCH AT WESLEYAN STREET AT VIENNA, VA 385251.93 771418.51

S22 0165394695 STORM DRAIN AT PROSPERITY AVENUE AT VIENNA, VA 385251.85 771402.74

S21 0165394710 STORM DRAIN BELOW INTERSTATE 66 AT VIENNA, VA 385247.31 771419.69

T25 0165394715 LONG BRANCH BELOW INTERSTATE 66 AT VIENNA, VA 385246.88 771419.88

S20 0165394775 STORM DRAIN 1 NR PROSPERITY AVENUE AT VIENNA, VA 385242.43 771416.63

S19 0165394780 STORM DRAIN 2 NR PROSPERITY AVENUE AT VIENNA, VA 385241.51 771415.86

Appendixes 87
Appendix 3.  Cross-reference listing of study site identifications and official USGS site identifications in the Accotink

Creek watershed of Virginia, including site names and coordinates. — Continued

[Latitude and longitude in decimal degrees. Station locations shown in figure 3. Sites are ordered by site number, from upstream to downstream]

Site Site number Station name Latitude Longitude

T24A2 0165394960 LONG BRANCH ABOVE OLD LEE HIGHWAY AT VIENNA, VA 385227.40 771431.18

T24B1 01653950 LONG BRANCH AT LEE HWY AT VIENNA, VA 385223.00 771434.00

T24A1 0165395130 LONG BRANCH AT DOGWOOD LANE AT VIENNA, VA 385214.14 771434.08

S18 0165395865 STORM DRAIN AT EXECUTIVE PARK AVE NEAR FAIRFAX, VA 385201.83 771422.99

T24 0165395975 LONG BRANCH ABOVE ARLINGTON BLVD NEAR FAIRFAX, VA 385156.66 771435.65

T23A2 0165396330 LONG BRANCH NEAR COPELAND POND CT NEAR FAIRFAX, VA 385145.75 771444.72

T23A1 0165396825 LONG BRANCH NEAR MANTUA DRIVE NEAR FAIRFAX, VA 385131.47 771453.36

T23 0165397320 LONG BRANCH AT MOUTH NEAR FAIRFAX, VA 385116.73 771457.54

A10 0165397510 ACCOTINK CR BELOW PROSPERITY AVE NEAR FAIRFAX, VA 385111.00 771445.00

S17 0165397515 STORM DRAIN AT SHANDWICK PLACE NEAR FAIRFAX, VA 385143.27 771354.53

S29 0165397550 STORM DRAIN AT APPLEGATE COURT NEAR FAIRFAX, VA 385131.15 771406.02

T22 0165397590 ACCOTINK CR TRIB 6 AT HILLSIDE PL NR FAIRFAX, VA 385129.37 771426.00

T21 0165397640 ACCOTINK CR TRIB 6 AT MOUTH NEAR FAIRFAX, VA 385113.00 771444.00

A9 0165397705 ACCOTINK CREEK NEAR BEVERLY DRIVE NEAR FAIRFAX, VA 385055.40 771421.57

S16 0165397715 STORM DRAIN NEAR BEVERLY DRIVE NEAR FAIRFAX, VA 385054.25 771418.67

S15 0165397840 STORM DRAIN AT BOSWORTH COURT NEAR FAIRFAX, VA 385038.90 771549.98

S14 0165397875 STORM DRAIN AT CHANTAL LANE NEAR FAIRFAX, VA 385041.63 771533.14

T20 0165397915 CROOK BRANCH AT GLADE HILL ROAD NEAR FAIRFAX, VA 385042.93 771510.79

T19 0165397925 CROOK BRANCH TRIBUTARY 1 AT MOUTH NEAR FAIRFAX, VA 385042.22 771510.60

S13 0165397950 STORM DRAIN AT GLADE HILL ROAD NEAR FAIRFAX, VA 385039.32 771506.73

T18 0165398350 CROOK BRANCH AT MOUTH NEAR FAIRFAX, VA 385049.63 771422.72

A8 01653985 ACCOTINK CR AT WOODBURN DR NEAR ANNANDALE, VA 385046.00 771416.00

T17 0165398530 ACCOTINK CREEK TRIB 7 AT MOUTH NEAR ANNANDALE, VA 385045.26 771415.70

T59 0165398550 ACCOTINK CR TRIB 8 AT WOODBURN RD NR ANNANDALE, VA 385118.18 771336.61

S12 0165398555 STORM DRAIN ABOVE WOODBURN ROAD NEAR ANNANDALE, VA 385118.05 771336.65

T16 0165398590 ACCOTINK CR TRIB 8 AB CHIVALRY RD NR ANNANDALE, VA 385102.34 771337.61

T15 0165398660 ACCOTINK CREEK TRIB 8 AT MOUTH NEAR ANNANDALE, VA 385044.22 771402.02

T14 0165398670 ACCOTINK CREEK TRIB 9 AT MOUTH NEAR ANNANDALE, VA 385039.60 771404.49

S11 0165398685 STORM DRAIN AT KAY COURT NEAR ANNANDALE, VA 385032.26 771356.67

A7 0165399020 ACCOTINK CREEK NR HILLCREST LANE NR ANNANDALE, VA 385038.38 771319.69

T13A 0165399035 ACCOTINK CR TRIB 10 NR REBEL DR AT ANNANDALE, VA 385052.58 771309.97

T13 0165399055 ACCOTINK CREEK TRIB 10 AT MOUTH NR ANNANDALE, VA 385038.45 771319.41

S10 0165399060 STORM DRAIN NEAR THOR DRIVE AT ANNANDALE, VA 385039.94 771309.50

A6 0165399095 ACCOTINK CR AB LITTLE RIVER TPKE NR ANNANDALE, VA 385010.39 771312.81

S9 0165399132 STORM DRAIN AT MACGREGOR COURT AT ANNANDALE, VA 385036.29 771248.19

T11 0165399155 ACCOTINK CR TRIB 11 NR HIRST DR AT ANNANDALE, VA 385014.11 771256.13

T12 0165399190 ACCOTINK CR TRIB 1 TO TRIB 11 AT ANNANDALE, VA 385013.01 771256.22

T58 0165399215 ACCOTINK CREEK TRIB 11 AT MOUTH AT ANNANDALE, VA 385005.25 771307.01

A5 0165399225 ACCOTINK CREEK NEAR ACCOTINK PKWY AT ANNANDALE, VA 384957.34 771311.86

S8 0165399235 STORM DRAIN 1 AT CARMELO DRIVE AT ANNANDALE, VA 384950.33 771230.59

S7 0165399237 STORM DRAIN 2 AT CARMELO DRIVE AT ANNANDALE, VA 384950.40 771230.64

S6 0165399252 STORM DRAIN AT AMERICANA DRIVE AT ANNANDALE, VA 384957.83 771249.44

S5 0165399255 STORM DRAIN NEAR IVYMOUNT COURT AT ANNANDALE, VA 384949.35 771251.84

88 A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System
Appendix 3.  Cross-reference listing of study site identifications and official USGS site identifications in the Accotink

Creek watershed of Virginia, including site names and coordinates. — Continued

[Latitude and longitude in decimal degrees. Station locations shown in figure 3. Sites are ordered by site number, from upstream to downstream]

Site Site number Station name Latitude Longitude

T9 0165399285 ACCOTINK CREEK TRIB 12 AT MOUTH AT ANNANDALE, VA 384956.51 771311.01

A4 0165399313 ACCOTINK CREEK NEAR WOODLARK DR AT ANNANDALE, VA 384942.61 771325.71

T10 0165399345 ACCOTINK CR TRIB 13 AT HILLCREST NR ANNANDALE, VA 385017.57 771346.34

S4 0165399368 STORM DRAIN AT CAMPUS DRIVE NEAR ANNANDALE, VA 385006.13 771404.31

T8 0165399430 ACCOTINK CREEK TRIB 13 AT MOUTH AT ANNANDALE, VA 384942.05 771327.85

A3 0165399438 ACCOTINK CREEK NR BRIAR CREEK DR NR ANNANDALE, VA 384935.07 771326.14

T7 0165399495 ACCOTINK CREEK TRIB 14 AT MOUTH NEAR ANNANDALE, VA 384934.65 771327.79

S3 0165399507 STORM DRAIN AT PATRIOT LANE AT ANNANDALE, VA 384930.28 771305.47

T6 0165399515 ACCOTINK CREEK TRIB 15 AT MOUTH NEAR ANNANDALE, VA 384931.54 771325.95

S52 0165399522 STORM DRAIN NEAR COMMONS DRIVE AT ANNANDALE, VA 384920.27 771316.52

A2 0165399535 ACCOTINK CREEK ABOVE TURKEY RUN NEAR ANNANDALE, VA 384859.27 771340.95

T5 0165399573 TURKEY RUN NEAR BANFF STREET NEAR ANNANDALE, VA 384933.20 771428.66

T4 0165399575 TURKEY RUN ABOVE SUGARBUSH COURT NR ANNANDALE, VA 384933.20 771428.24

T3 0165399585 TURKEY RUN TRIB 1 NR SUGARBUSH CT NR ANNANDALE, VA 384929.37 771416.84

T2 0165399645 TURKEY RUN ABOVE PRIVATE LANE NEAR ANNANDALE, VA 384914.81 771356.15

S2 0165399675 STORM DRAIN AT OLD WELL ROAD NEAR ANNANDALE, VA 384905.14 771358.13

T1 0165399715 TURKEY RUN AT MOUTH NEAR ANNANDALE, VA 384859.00 771343.00

S1 0165399770 STORM DRAIN AT KALORAMA ROAD AT ANNANDALE, VA 384848.78 771304.14

Appendixes 89

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Hyer—A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System USGS SIR 2006–5317