U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2014–3011

March 2014

Prepared in cooperation with the South Carolina Department of Transportation

Characterization of Stormwater at Selected South Carolina 

Department of Transportation Maintenance Yards and 

Section Shed Facilities in Ballentine, Conway, and 

North Charleston, South Carolina, 2010–12

 Introduction

Increased impervious surfaces (driveways, parking lots, and 

buildings) and human activities (residential, industrial, and commercial) have been linked to substantial changes in both the quality 

and quantity of stormwater on a watershed scale (Brabec and others, 

2002; Pitt and Maestre, 2005). Small-scale storage and equipment 

repair facilities increase impervious surfaces that prevent infiltration of 

stormwater, and these facilities accommodate activities that can introduce trace metals, organic compounds, and other contaminants to the 

facility’s grounds. Thus, these small facilities may contribute pollutants 

to the environment during storm events (U.S. Environmental Protection 

Agency, 1992). 

The South Carolina Department of Transportation (SCDOT) 

operates section shed and maintenance yard facilities throughout the 

State. Prior to this investigation, the SCDOT had no data to define the 

quality of stormwater leaving these facilities. To provide these data, 

the U.S. Geological Survey (USGS), in cooperation with the SCDOT, 

conducted an investigation to identify and quantify constituents that 

are transported in stormwater from two maintenance yards and a 

section shed in three different areas of South Carolina (fig. 1). The 

two maintenance yards, in North Charleston and Conway, S.C., were 

selected because they represent facilities where equipment and road 

maintenance materials are stored and complete equipment repair operations are conducted. The section shed, in Ballentine, S.C., was selected 

because it is a facility that stores equipment and road maintenance 

material. Characterization of the constituents that were transported in 

stormwater from these representative SCDOT maintenance facilities 

may be used by the SCDOT in the development of stormwater management plans for similar section shed and maintenance yard facilities 

throughout the State to improve stormwater quality. 

Description of the Study Area 

The Ballentine section shed has a drainage area of 

12,133 square meters (m2) (0.0047 square mile (mi2)), and 79 percent of the area is composed of impervious surface (table 1; fig. 2). 

Stormwater drainage from the study area is surficial sheet flow that is 

diverted by a curb-and-gutter system to a retention basin or pond that is 

dry except during storms. Stormwater enters the retention pond through 

drainage pipes. Stormwater accumulates in the retention pond until 

there is enough water depth and flow to exit the retention pond through 

the main outfall that then directs the stormwater off the facility to a 

roadside ditch. 

The Conway maintenance yard has a drainage area of 41,207 m2

(0.01590 mi2) with a curb-and-gutter system to capture stormwater as it 

runs off the facility (fig. 3). The total impervious surface of the facility 

is 70 percent. Water drainage from the study area is surficial sheet flow 

that discharges to two outfalls within the study site. The Conway1 

outfall, near the fuel island at the southern end of the property, was 

modified by installing a 6-inch polyvinyl chloride (PVC) pipe to 

sample the stormwater discharge (fig. 3). This outfall has a drainage 

area of 1,200 m2 (0.00046 mi2), and the area is entirely (100 percent) 

composed of impervious surface (table 1). The Conway2 outfall is at 

the beginning of a grass-lined ditch that drains the northern part of the 

site (fig. 3). Stormwater was captured and directed to this outfall by 

a curb-and-gutter system. The drainage area is 9,912 m2 (0.0038 mi2) 

with 100 percent impervious surface (table 1).

Stormwater discharges from the North Charleston maintenance 

yard to Turkey Creek, a perennial stream, through a combination of 

pipes, ditches, and overland flow. In order to sample stormwater from 

all areas of the yard, samples were collected from the main channel of 

Turkey Creek at the upstream (North Charleston1) and downstream 

(North Charleston2) limits of the North Charleston maintenance yard 

facility (fig. 4). Drainage area of the maintenance yard is 85,999 m2

(0.033 mi2), and the total impervious surface is 62 percent (table 1). 

Stormwater constituents in the water samples at the upstream site 

(North Charleston1) represent stormwater contributions from the headwater drainage area above the North Charleston property.

Data Collection and Analysis

From January 2010 through January 2012, the USGS operated 

data-collection stations at the five study sites (table 1). The datacollection effort included monitoring the quantity of rainfall and the 

collection of stormwater-quality samples. Established guidelines and 

protocols were used to ensure the data were of the highest quality. 

As many as nine storm samples were collected at five locations that 

received stormwater discharge from the Ballentine (one outfall, nine 

samples), North Charleston (two locations on Turkey Creek, eight 

samples each), and Conway (two outfalls, Conway1 eight samples, 

Conway2 seven samples) facilities. The samples were analyzed for 

nutrients, fecal indicator bacteria, total and dissolved concentrations of 

six trace metals (cadmium, copper, chromium, lead, nickel, and zinc), 

and suspended sediment. Stormwater samples also were analyzed for 

synthetic and semivolatile organic compounds, including 10 herbicides, 

18 organochlorine pesticides, 7 Aroclor congeners, 44 volatile organic 

compounds, and 16 polycyclic aromatic hydrocarbons.
Ê

Piedmont

Lower Coastal Plain

Upper Coastal Plain

Blue Ridge

Columbia

AIKEN

HORRY

YORK

LEE

COLLETON

JASPER

SUMTER

OCONEE

ORANGEBURG

UNION

LAURENS

KERSHAW

FLORENCE

CHARLESTON

ANDERSON

FAIRFIELD

LEXINGTON

CHESTER

MARION

PICKENS

SALUDA

NEWBERRY

HAMPTON

CLARENDON

DILLON

CHESTERFIELD

BARNWELL

LANCASTER

ABBEVILLE

EDGEFIELD

DARLINGTON

CALHOUN

CHEROKEE

BERKELEY

RICHLAND

GREENVILLE

WILLIAMSBURG

SPARTANBURG

DORCHESTER

MARLBORO

BAMBERG

GREENWOOD

ALLENDALE

MCCORMICK

82°

81° 83°

80°

79°

35°

34°

82°

34°

83°

81°

80°

33°

79°

0 10 20 30 MILES

Base from U.S. Department of Agriculture, 2009, 1 meter 

Projection: Universal Transverse Mercator, zone 17 

North American Datum of 1983 (NAD 83)

Ballentine

study area

Charleston

study area

Conway

study area

0 10 20 30 KILOMETERS

Line

NORTH CAROLINA

SOUTH CAROLINA

Turkey Creek

basin from DOT site

325427080015000

Figure 1. Location of South Carolina Department of Transportation (DOT) Ballentine section shed, Conway and North Charleston 

maintenance yards, Turkey Creek Basin in South Carolina.
Table 1. Description of South Carolina Department of Transportation maintenance yard and section shed sites in North Charleston, Conway, and 

Ballentine, South Carolina. 

[NWIS, National Water Information System database of the U.S. Geological Survey; ID, identification; m2, square meters; mi2, square miles; ft3/s, cubic feet per second; 

SCDOT, South Carolina Department of Transportation; S.C., South Carolina; NS, not sampled; ND, not determined]

NWIS station 

identification 

number

NWIS station name Site ID

Drainage area

Impervious 

surface 

(percent)

Number of 

samples 

collected

Average 

event-mean 

stormwater 

discharge 

(ft3

/s)

Average eventmean unit-area 

stormwater 

discharge 

([ft3

/s]/mi2)

m2 mi2

340801081142000 SCDOT maintenance yard 

outfall near Ballentine, 

S.C. 

Ballentine 12,133 0.005 79 9 0.33 70.2

335444079024500 Outfall 1 from SCDOT 

maintenance yard, 

Conway, S.C.

Conway1 1,200 0.000 100 9 0.16 348

335448079024500 Outfall 2 from SCDOT 

maintenance yard, 

Conway, S.C. 

Conway2 9,912 0.004 100 8 0.67 176

ND Conway maintenance yard41,207 0.016 70 NS NS NS

021720646 Turkey Creek at SCDOT 

maintenance yard, North 

Charleston, S.C. 

North Charleston1 3,909,680 1.510 ND 8 3.06 2.0

325427080014600 Turkey Creek below SCDOT 

maintenance yard, North 

Charleston, S.C.

North Charleston2 3,995,679 1.543 ND 8 5.39 3.5

ND North Charleston 

maintenance 

yard

85,999 0.033 62 NS 2.35 71.2

Retention 

pond

Roadside ditch

Ballentine DOT 

drainage area

Ballentine 

Outfall

0 50 100 150 FEET N

0 10 20 30 40 METERS

Base from U.S. Department of Agriculture, 2009, 1 meter

Projection: Universal Transverse Mercator, zone 17

North American Datum of 1983 (NAD 83) 

Figure 2. Aerial photograph of drainage area delineation of the 

South Carolina Department of Transportation (DOT) section shed 

and outfalls, Ballentine, South Carolina.

Conway DOT 

drainage area

Conway1 Outfall

Conway2 Outfall

0 50 100 150 FEET N

0 10 20 30 40 METERS

Flow

Base from U.S. Department of Agriculture, 2009, 1 meter

Projection: Universal Transverse Mercator, zone 17

North American Datum of 1983 (NAD 83) 

Figure 3. Aerial photograph of drainage area delineation of the 

South Carolina Department of Transportation (DOT) maintenance 

yard and outfalls, Conway, South Carolina.
Creek

North Charleston1 Outfall

North Charleston2 Outfall

Charleston DOT 

drainage area

Base from U.S. Department of Agriculture, 2009, 1 meter N

Projection: Universal Transverse Mercator, zone 17 

North American Datum of 1983 (NAD 83) 

Turkey

0

0

200 400 600 FEET

50 100 150 METERS

.

Flow

Figure 4. Aerial photograph of drainage area delineation of the South Carolina Department of 

Transportation (DOT) maintenance yard and outfalls, North Charleston, South Carolina.

Summary and Conclusions

The storms sampled during this study had a wide range of 

rainfall amounts, durations, and intensities at each of the facilities and, 

therefore, were considered to be reasonably representative of the potential for contaminant transport. At all facilities, stormwater discharge 

was significantly correlated to rainfall amount and intensity. Eventmean unit-area stormwater discharge increased with increasing impervious surface at the Conway and North Charleston maintenance yards. 

The Ballentine facility, with 79 percent impervious surface, had a mean 

unit-area discharge similar to that of the North Charleston maintenance 

yard (62 percent impervious surface). That similarity may be attributed, 

in part, to the effects of the retention pond on the stormwater runoff at 

the Ballentine facility and to the greater rainfall intensities and amounts 

at the North Charleston facility. 

Stormwater often transports large quantities of sediment and 

sediment-bound contaminants, including nutrients and fecal indicator bacteria. Median event-mean concentrations of suspended sediment in stormwater at these facilities ranged from 54 milligrams per 

liter (mg/L) in Turkey Creek at North Charleston2 to 147 mg/L in 

stormwater discharging from the Ballentine retention pond outfall. In 

general, event-mean concentrations of total nitrogen consisted mainly 

of total Kjeldahl nitrogen (organic nitrogen plus ammonia) rather than 

nitrate plus nitrite in stormwater, and the median event-mean concentrations of total nitrogen ranged from 1.59 mg/L at the Conway1 pipe 

outfall to 2.00 mg/L at the Ballentine retention pond outfall. Median 

event-mean concentrations of total phosphorus in stormwater ranged 

from 0.15 mg/L at the Conway1 outfall to 0.42 mg/L in Turkey Creek 

at North Charleston1. 

Escherichia coli (E. coli) and enterococcus concentrations often 

varied by 3 to 4 orders of magnitude in grab samples collected during 

the “first flush” of stormwater discharging to the sampled outfalls of 

Turkey Creek. Additionally, enterococcus concentrations consistently 

were greater than the corresponding E. coli concentrations in stormwater samples. Specifically, median “first-flush” E. coli concentrations 

ranged from 30 colonies per 100 milliliters (col/100 mL) at the Conway1 

outfall to 4,359 col/100 mL in Turkey Creek at North Charleston2, 

whereas enterococcus concentrations ranged from 512 col/100 mL at 

the Conway1 outfall to 6,329 col/100 mL in Turkey Creek at North 

Charleston2. Compared to the proposed South Carolina Department of 

Health and Environmental Control primary and secondary body contact 

criterion of 349 col/100 mL (South Carolina Department of Health and 

Environmental Control, 2012), stormwater samples had E. coli concentrations 

that were greater than the criterion in 

four of the nine storms at the Ballentine 

retention pond outfall, one of the eight 

storms at the Conway1 pipe outfall, 

five of the seven storms at the Conway2 

grass-lined ditch outfall, two of the eight 

storms at North Charleston1 on Turkey 

Creek, and eight of the eight storms at 

North Charleston2 on Turkey Creek.

Of the six trace metals measured 

in stormwater, only copper and zinc had 

event-mean concentrations greater than 

the hardness-dependent South Carolina 

Department of Health and Environmental Control aquatic life criteria maximum 

concentrations (South Carolina Department of Health and Environmental Control, 2012). Measured dissolved copper 

event-mean concentrations in stormwater were greater than the criterion in five 

of the samples at the Ballentine facility, 

one of the samples at Conway1, two of 

the samples at Conway2, and one of the 

samples at North Charleston2. Measured 

dissolved zinc event-mean concentrations in stormwater were greater than 

the criterion in three of the samples 

at the Ballentine facility, one of the 

samples at Conway1, two of the samples 

at Conway2, and zero of the samples at North Charleston2. At North 

Charleston1 upstream from the North Charleston maintenance yard, the 

measured dissolved trace-metal concentrations were all less than the 

criterion maximum concentrations.

Among the three facilities, Conway1 outfall had the greatest 

range in event-mean yields in stormwater for total phosphorus, total 

nitrogen, total suspended solids, and suspended sediment, and both 

Conway outfalls tended to have median event-mean yields greater than 

those of the Ballentine and North Charleston yard facilities. “Firstflush” yields of E. coli in stormwater were not statistically different 

among the three facilities. 

 Median event-mean yields of suspended sediment, total nitrogen, 

total phosphorus, total copper, and total zinc in stormwater demonstrated a strong linear relation to impervious surface at the three facilities. However, median “first-flush” fecal indicator bacterial yields did 

not have a linear relation to impervious surface.

References

Brabec, E., Schulte, S., and Richards, P.L., 2002, Impervious surfaces and 

water quality—A review of current literature and its implications for 

watershed planning: Journal of Planning Literature, v. 16, no. 4, p. 499–514, 

accessed March 25, 2013, at http://dandelion-patch.mit.edu/afs/athena.mit.

edu/dept/cron/project/urban-sustainability/Stormwater_Sarah%20Madden/

References/Brabec_etal2002.pdf.

Pitt, R.E., and Maestre, A., 2005, Stormwater quality as described in the 

National Stormwater Quality database (NSQD): Proceedings of the 10th 

International Conference on Urban Drainage, Copenhagen, Denmark, 

August 21–25, 2005, p. 1–8.

South Carolina Department of Health and Environmental Control, 2012, Water 

classifications and standards: South Carolina Department of Health and 

Environmental Control, Code of Regulations, State Register, Regulation 

61–68, accessed January 31, 2013, at http://www.scdhec.gov/environment/

water/regs/r61-68.pdf.

U.S. Environmental Protection Agency, 1992, NPDES storm water sampling 

guidance document: U.S. Environmental Protection Agency, Office of 

Water, EPA 833–B–91–001.

By Celeste A. Journey (cajourney@usgs.gov) and 

Kevin J. Conlon (kjconlon@usgs.gov),

South Carolina Water Sceince Center

ISSN 2327-6932 (online)

http://dx.doi.org/10.3133/fs20143011