U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2016–3096

November 2016

Selected Streambed Sediment Compounds and Water Toxicity 

Results for Westside Creeks, San Antonio, Texas, 2014 

Introduction

The Alazán, Apache, Martínez, and San Pedro Creeks in 

San Antonio, Texas, are part of a network of urban tributaries 

to the San Antonio River, known locally as the Westside 

Creeks (fig. 1). The Westside Creeks flow through some of 

the oldest neighborhoods in San Antonio. The disruption of 

streambed sediment is anticipated during a planned restoration 

to improve and restore the environmental condition of 14 miles 

of channelized sections of the Westside Creeks in San Antonio. 

These construction activities can create the potential to 

reintroduce chemicals found in the sediments into the ecosystem 

where, depending on hydrologic and environmental conditions, 

they could become bioavailable and toxic to aquatic life. 

Elevated concentrations of sediment-associated contaminants 

often are measured in urban areas such as San Antonio, 

Tex. (Ging and others, 1999; Chalmers and others, 2007). 

Contaminants found in sediment can affect the health of aquatic 

organisms that ingest sediment. The gradual accumulation of 

trace elements and organic compounds in aquatic organisms 

can cause various physiological issues and can ultimately result 

in death of the aquatic organisms; in addition, subsequent 

ingestion of aquatic organisms can transfer the accumulated 

contaminants upward through the food chain (a process called 

biomagnification).

 The U.S. Geological Survey, in cooperation with the San 

Antonio River Authority, collected sediment samples and water 

samples for toxicity testing from sites on the Westside Creeks 

as part of an initial characterization of selected contaminants in 

the study area. Samples were collected in January 2014 during 

base-flow conditions and again in May 2104 after a period of 

Leon Creek

Elmendorf 

Lake

Woodlawn

Lake

San

AntonioRiver

Apache Cr eek

Martínez Creek

San Antonio River

San Pedro Creek

Alazán Creek

410 10

£¤281

35

151

10

37

35

90

MTZ-US

ALZ-US

APC-US SPD-US

APC-DS

SPD-MD

ALZ-DS

SPD-DS

SAR

MTZ-DS

Base modified from City of San Antonio digital data

State Plane Texas South Central Projection

North American Datum of 1983 

98°35'15" 98°32'00" 98°28'45"

29°26'15"

29°22'30"

BEXAR COUNTY

TEXAS

BEXAR COUNTY

Area enlarged

San

Antonio

EXPLANATION

Stream segments representing the extent of the planned restoration project

 (San Antonio River Authority, 2016)

U.S. Geological Survey sampling site with map identifier where streambed-sediment

 samples and samples for water-toxicity testing were collected SAR

0 1 2 MILES

0 1 2 KILOMETERS

MTZ-US

MTZ-DS

ALZ-US

ALZ-DS

APC-US

APC-DS

SPD-US

SPD-MD

SPD-DS

SAR

Upstream Martínez

Downstream Martínez

Upstream Alazán

Downstream Alazán

Upstream Apache

Downstream Apache

Upstream San Pedro

Middle San Pedro

Downstream San Pedro

San Antonio River

Short name for

sampling site

Map

identifier 

Figure 1. Locations of sites where streambed-sediment samples and samples for water-toxicity testing were collected from the Westside 

Creeks and San Antonio River, San Antonio, Texas, 2014.

ISSN 2327-6916 (print) ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20163096
stormwater runoff (poststorm conditions). Sediment samples 

were analyzed for selected constituents, including trace elements 

and organic contaminants such as pesticides, brominated flame 

retardants, polychlorinated biphenyls (PCBs), and polycyclic 

aromatic hydrocarbons (PAHs). In addition, as an indicator of 

ecological health (and possibly bioavailability of contaminants 

in disturbed streambed sediments), the toxicity of water samples 

to the indicator species Pimephales promelas (fathead minnow) 

was evaluated by using standard 7-day water-toxicity testing. 

Sediment Quality Results

Potential risks of contaminants in sediment were evaluated 

by comparing concentrations of contaminants in sediment to 

effects-based sediment quality guidelines (SQGs). The SQGs 

evaluate the potential toxicity of bed sediments to benthic 

biota. Two SQG concentration levels were used: (1) a lower 

level, called the threshold effect concentration (TEC), below 

which harmful effects to benthic biota are not expected; and 

(2) a higher level, the probable effect concentration (PEC), 

above which harmful effects are expected to occur frequently 

(MacDonald and others, 2000). 

Trace Elements

The concentrations of the trace elements arsenic, cadmium, 

mercury, and nickel were less than the TEC in all of the samples. 

Lead and zinc were most frequently detected at concentrations 

greater than the TEC (fig. 2). Concentrations of lead in all 

four samples collected from the upper and middle San Pedro 

Creek sites were greater than the PEC. Sources of the lead 

concentrations in the samples collected at these two sites might 

include older petroleum storage tanks that held leaded fuel or 

possibly from a variety of automobile components used in the 

numerous automobile-related businesses in the area (Texas 

Commission on Environmental Quality, 2009).

Pesticides

Of the 19 pesticides investigated in this study, historicaluse pesticides that have been banned or are being phased out 

because of their toxicity and persistence in the environment 

were more frequently detected in streambed-sediment samples 

compared to current-use pesticides. Three chlordane compounds 

(cis-chlordane, trans-chlordane, and trans-nonachlor) were 

detected in all of the samples collected during both base-flow 

and poststorm conditions. Pesticides were most frequently 

detected in concentrations greater than their PECs in samples 

from the upstream and middle San Pedro sites. During base-flow 

conditions, concentrations of DDD, DDE, and DDT exceeded 

their PECs in the sample collected from the middle San Pedro 

site. During poststorm conditions, chlordane, DDD, and DDE 

concentrations in samples collected at the upstream San Pedro 

site, and DDD and DDE concentrations at the middle San Pedro 

site exceeded their PECs.

Flame Retardants

Brominated flame retardants are generally added to plastics, 

foams, and fabrics to increase the fire resistance of products 

such as electronics, automobiles, clothing, and furniture (Shaw 

and others, 2010). Brominated flame retardants (such as the 

SPD-US

SPD-MD

MTZ-US

MTZ-DS

ALZ-US

ALZ-DS

APC-USAPC-DS

SPD-DS

SAR

Map identifier (fig. 1)

0

50

100

150

200

250

300

0

50

100

150

200

250

300

350

400

450

500

Concentration, in milligrams per kilogram

[TEC, threshold effect concentration; PEC, probable effect concentration]

TEC

TEC

PEC

PEC

Lead

Zinc

Streambed-sediment sample

 concentration

 Base-flow sample

 Poststorm sample

EXPLANATION

Figure 2. Comparison of consensus-based sediment quality 

guidelines (MacDonald and others, 2000) with concentrations of lead 

and zinc in streambed-sediment samples collected from sites on the 

Westside Creeks and San Antonio River, San Antonio, Texas, 2014.

polybrominated biphenyl ether congeners 85, 153, and 154) were 

found at every site where streambed sediments were collected; the 

concentrations measured were typically greater than the available 

guidelines for aquatic life, and not all compounds have guidelines 

(Environment Canada, 2013). Brominated flame retardants were 

more frequently detected in samples collected during poststorm 

conditions than in those collected during base-flow conditions, 

with the greatest increase in the number of brominated flame 

retardants detected when comparing samples collected from the 

San Pedro Creek sites during base-flow and poststorm conditions. 

Polychlorinated Biphenyls 

The most common sources of PCBs are plasticizers, 

hydraulic lubricants, and dielectric fluids used in electrical 

capacitors (Smith and others, 1988). Streambed-sediment 

samples collected from 10 sites were analyzed for 18 common 

PCB congeners. The PCBs 174, 187, and 194 were found in every 

streambed-sediment sample collected during both base-flow and 

poststorm conditions. The concentrations of total PCBs, computed 

as the sum of the 18 reported congeners, did not exceed the TEC 

in any of the samples. The concentrations of total PCBs in the 

samples collected during base-flow and poststorm conditions from 
the upstream and middle sites on San Pedro Creek were greater 

than the concentrations in the samples collected from the other 

study sites.

Polycyclic Aromatic Hydrocarbons 

Concentrations for the majority of the individual PAHs 

analyzed and the total PAH concentration exceeded their 

TECs. The PECs were exceeded in 30 of 220 analyses. At the 

upstream Apache site, 6 of the individual PAHs concentrations 

measured in the sample collected during base-flow conditions 

exceeded the 9 established PECs and 8 PECs were exceeded 

in the sample collected during poststorm conditions. The total 

PAH concentration in the sample collected during poststorm 

conditions was 3.3 times greater than the PEC developed for 

total PAHs, making it the most contaminated site in regards to 

total PAHs in the study area (fig. 3).

Average PAH profiles for samples collected during baseflow and stormflow conditions at sites in the study area were 

computed by averaging each of the 12 normalized compound 

concentrations measured in the 10 samples collected during 

the different hydrologic conditions; the ratio of concentration 

of each of the 12 PAH compounds to the total sum of the PAH 

compound concentrations was used to normalize concentrations. 

Average PAH profiles computed for base-flow samples and 

poststorm samples were compared to seven published PAH 

source profiles (Van Metre and Mahler, 2010) including, but not 

limited to, coal-tar sealants, automobile emissions, and coalfired powerplant emissions. The graphical representations of the 

average base flow and average poststorm streambed-sediment 

PAH profiles most closely resemble that of the parking lot coaltar sealcoat dust PAH source profile (fig. 3). 

Map identifier (fig. 1) SPD-US

SPD-MD

MTZ-US

MTZ-DS

ALZ-US

ALZ-DS

APC-US

APC-DS

SPD-DS

SAR

Phenanthrene

Anthracene

Fluoranthene

Pyrene

Benzo(a)anthracene

Chrysene

Benzo(b)fluoranthene

Benzo(k)fluoranthene

Benzo(e)pyreneBenzo(a)pyrene

Indenopyrene

Benzo(ghi)perylene

Individual PAH

0

4,000

8,000

12,000

16,000

20,000

24,000

Total PAH concentration,

in micrograms per kilogram

0

0.05

0.10

0.15

0.20

0.25

0.30

Ratio of individual PAH to total PAHs

[TEC, threshold effect concentration; PEC, probable effect concentration]

TEC

PEC Total PAH

Parking lot coal-tar

sealcoat dust

(99,000) (27,000)

(99,000)

EXPLANATION

Streambed-sediment sample concentration

 Base-flow sample, detection

 Poststorm sample, detection

Concentration value off scale

PAH source

Average base-flow streambed sediment

 1 standard deviation error bar

Average poststorm streambed sediment

 1 standard deviation error bar

EXPLANATION

Figure 3. Comparison of consensus-based sediment quality 

guidelines (MacDonald and others, 2000) with concentrations of 

total polycyclic aromatic hydrocarbons (PAHs) and comparison of 

PAH source profile for parking lot coal-tar sealcoat dust (Van Metre 

and Mahler, 2010) to PAH profiles for average streambed sediment 

computed from samples collected during base-flow and poststorm 

conditions from sites on the Westside Creeks and San Antonio River, 

San Antonio, Texas, 2014. 
Water Toxicity Results

Six of the ten environmental water samples collected 

during base-flow conditions at the 10 sites were toxic to fathead 

minnow, causing appreciable reductions in survival rates 

and biomass (fig. 4). The relations between fathead minnow 

survival and concentrations of major ions measured in the 

water samples were examined and no appreciable correlations 

were observed. The relations between fathead minnow survival 

and concentrations of selected constituents in the streambedsediment samples collected during base-flow conditions also 

showed no significant correlations. Fathead minnow populations 

in all 10 environmental water samples collected during 

poststorm conditions did not indicate any reductions in survival 

compared to the control water.

The compounds detected in the Westside Creeks are 

common in urban streams, but the San Pedro Creek sites 

were of specific concern because the sediments contained 

elevated concentrations of lead and historical-use pesticides 

that consistently exceeded applicable PECs. Additionally, the 

total PCB concentrations in samples at two San Pedro Creek 

sites, although less than the TEC, were the largest total PCB 

concentrations measured among all of the sites in the study area. 

During both base-flow and poststorm conditions, six individual 

PAHs were greater than their PECs, and total PAHs were greater 

than the PEC in samples collected during poststorm conditions at 

the upstream San Pedro Creek site.

SPD-US

SPD-MD

MTZ-USMTZ-DS

ALZ-US

ALZ-DS

APC-USAPC-DS

SPD-DS

SAR

Control Sample 1Control Sample 2

Map identifier (fig. 1)

0

20

40

60

80

100

120

10

30

50

70

90

110

Fathead minnow survival, in percent

EXPLANATION

Water sample with 1 standard deviation error bar—Base-flow condition

 Sample nontoxic to fathead minnows

 Sample toxic to fathead minnows

Water sample with 1 standard deviation error bar—Poststorm condition

 Sample nontoxic to fathead minnows

Figure 4. Responses of Pimephales promelas (fathead minnow) in 

7-day exposure to water samples collected during base-flow and 

poststorm conditions from sites on the Westside Creeks and San 

Antonio River, San Antonio, Texas, 2014.

This fact sheet is based on the following U.S. Geological Survey 

report:

Crow, C.L., Wilson, J.T., and Kunz, J.L., 2016, Occurrence 

and concentrations of selected trace elements, halogenated 

organic compounds, and polycyclic aromatic hydrocarbons 

in streambed sediment and results of water-toxicity testing 

in Westside Creeks and the San Antonio River, San Antonio, 

Texas, 2014: U.S. Geological Survey Scientific Investigations 

Report 2016–5136, 56 p. 

References

Chalmers, A.T., Van Metre, P.C., and Callender, Edward, 2007, The 

chemical response of particle-associated contaminants in aquatic 

sediments to urbanization in New England, U.S.A.: Journal of 

Contaminant Hydrology, v. 91, nos. 1–2, p. 4–25.

Environment Canada, 2013, Canadian Environmental Protection 

Act, 1999, Federal Environmental Quality Guidelines, 

polybrominated diphenyl ethers (PBDEs): Environment Canada, 

25 p. [Also available at http://www.ec.gc.ca/ese-ees/05DF7A37-

60FF-403F-BB37-0CC697DBD9A3/FEQG_PBDE_EN.pdf.]

Ging, P.B., Van Metre, P.C., and Callender, Edward, 1999, Bottom 

sediments of Lorence Creek Lake, San Antonio, Texas, reflect 

contaminant trends in an urbanizing watershed: U.S. Geological 

Survey Fact Sheet FS–149–99, 4 p.

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 2000, 

Development and evaluation of consensus-based sediment quality 

guidelines for freshwater ecosystems: Archives of Environmental 

Contamination and Toxicology, v. 39, p. 20–31.

San Antonio River Authority, 2016, Westside Creeks Restoration 

Project, accessed January 12, 2016, at http://www.westsidecreeks.

com.

Shaw, S.D., Blum, Arlene, Weber, Ronald, Kannan, 

Kurunthachalam, Rich, David, Lucas, Donald, Koshland, 

C.P., Dobraca, Dina, Hanson, Sarah, Birnbaum, L.S., 2010, 

Halogenated flame retardants—Do the fire safety benefits justify 

the risks?: Reviews on Environmental Health, v. 25, no. 4, 

p. 261–305.

Smith, J.A., Witkowski, P.J., and Fusillo, T.V., 1988, Manmade 

organic compounds in the surface water of the United States—A 

review of current understanding: U.S. Geological Survey Circular 

1007, 92 p.

Texas Commission on Environmental Quality, 2009, Source water 

assessment, accessed August 31, 2015, at https://www.tceq.texas.

gov/drinkingwater/SWAP/index_swa.html.

Van Metre, P.C., and Mahler, B.J., 2010, Contribution of PAHs from 

coal-tar pavement sealcoat and other sources to 40 U.S. lakes: 

Science of the Total Environment, v. 409. p. 334–344.

By Cassi L. Crow, Jennifer T. Wilson, and James L. Kunz

For more information, please contact:

Director, Texas Water Science Center

U.S. Geological Survey

1505 Ferguson Lane

Austin, TX 78754– 4501

http://tx.usgs.gov/