U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 

Evaluation of Water Quality for Two 

St. Johns River Tributaries Receiving Septic 

Tank Effluent, Duval County, Florida

Prepared in cooperation with the

City of Jacksonville

03–4299

By Shaun M. Wicklein

Tallahassee, Florida

2004
For additional information Copies of this report can be purchased

from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225-0286

888-ASK-USGS

Use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey.

Additional information about water resources in Florida is available on the World Wide Web at

http://fl.water.usgs.gov

write to:

U.S. Geological Survey

2010 Levy Avenue

Tallahassee, FL 32301

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director
Contents III

CONTENTS

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

Introduction............................................................................................................................................... 2

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

Description of Study Area ........................................................................................................................................... 2

Data Collection and Analysis ...................................................................................................................................... 4

Basin Characteristics ............................................................................................................................................................. 9

Fishing Creek............................................................................................................................................................... 9

Big Fishweir Creek...................................................................................................................................................... 10

Streamflow............................................................................................................................................................................. 10

Evaluation of Water Quality and Potential Effects of Septic Tank Effluent.......................................................................... 13

Major Ions.................................................................................................................................................................... 14

Nutrients ...................................................................................................................................................................... 16

Wastewater Constituents.............................................................................................................................................. 18

Bacteria........................................................................................................................................................................ 19

Summary................................................................................................................................................................................ 22

References ............................................................................................................................................................................. 23

Appendixes

Appendix 1: Constituents analyzed as part of major ion and nutrient sampling ....................................................... 25

Appendix 2: Constituents analyzed as part of the U.S. Geological Survey National Water-Quality Laboratory

organic wastewater sample series...................................................................................................................................... 26

Appendix 3: Fecal coliform bacteria counts for surface-water samples................................................................................ 27

Appendix 4: Discriminant analysis of antibiotic resistance patterns used to classify fecal coliform bacteria 

from known sources into source categories for surface-water samples ............................................................................ 28

FIGURES

1-3. Maps showing:

1. Location of study areas and selected monitoring sites in Jacksonville, Duval County, Florida ........................ 3

2. Streamflow and water-quality data collection sites for Fishing Creek basin, Jacksonville, Florida.................. 5

3. Streamflow and water-quality data collection sites for South Branch Big Fishweir Creek basin, 

Jacksonville, Florida .......................................................................................................................................... 6

4-10. Plots showing:

4. Measured streamflow at data collection sites, Jacksonville, Florida, 2000-2002.............................................. 12

5. Comparison of daily mean streamflow for Ortega River near Jacksonville for the period of record, 

January 1, 1965, to September 30, 2002; January 1, 2000, to September 30, 2002; and daily mean 

streamflows for days on which measurements were made at Fishing Creek at 110th Street and 

South Branch Big Fishweir Creek at Blanding Boulevard ................................................................................ 12

6. Concentrations of dissolved sodium at data collection sites, Jacksonville, Florida........................................... 15

7. Concentrations of nitrogen species at data collection sites, Jacksonville, Florida............................................. 16

8. Concentrations of total nitrogen at data collection sites, Jacksonville, Florida................................................. 17

9. Concentrations of total phosphorus at data collection sites, Jacksonville, Florida............................................ 18

10. Concentrations of fecal coliform bacteria at data collection sites, Jacksonville, Florida .................................. 21

TABLES

1. Data collection and compilation sites, Jacksonville, Florida .................................................................................. 5

2. Subdivision and study basin characteristics, Jacksonville, Florida, 2000 .................................................... 9

3. Residential water use, Duval County, Florida, 2002............................................................................................... 10
IV Contents

4. Measured streamflow summary for data collection sites, Jacksonville, Florida ............................................ 11

5. Rainfall summary for selected sites in Jacksonville, Florida..................................................................... 13

6. Summary of major ion constituents from surface-water samples for Fishing Creek and South Branch 

Big Fishweir Creek, Duval County, Florida, 2000-02; the surficial aquifer system in Duval County, 

1970-89; and selected surficial aquifer wells in areas serviced by septic tanks, Dade County, Florida,

1970-73................................................................................................................................................................... 14

7. Summary of nitrogen and phosphorus concentrations for surface-water samples, Jacksonville, Florida .............. 17

8. Concentrations of organic wastewater compounds above the minimum laboratory-reporting level, 

Jacksonville, Florida........................................................................................................................ 19

9. Fecal coliform bacteria summary for surface-water samples, Jacksonville, Florida.............................................. 20

10. Summary of discriminant analysis of antibiotic resistance patterns used to classify fecal coliform 

bacteria from known sources into source categories for surface-water samples, Jacksonville, Florida............... 21

CONVERSION FACTORS AND VERTICAL DATUM

Temperature in degrees Fahrenheit (° F) may be converted to degrees Celsius (°C) as follows: °C=(° F-32)/1.8.

Horizontal coordinate information (latitude-longitude) is referenced to the North American Datum of 1983 (NAD83).

Acronyms and abbreviations:

JEA Jacksonville Electric Authority

μg/L micrograms per liter

mg/L milligrams per liter

mpn/100mL most probable number per 100 milliliters

NPDES National Pollutant Discharge Elimination System

NURP Nationwide Urban Runoff Project

USGS U.S. Geological Survey

Multiply By To obtain

Length

inch (in.) 2.54 centimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

acres (ac) 0.4047 hectare

square mile (mi2) 2.590 square kilometer 

Flow Rate

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

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

inch per year (in/yr) 25.4 millimeter per year
Abstract 1

Evaluation of Water Quality for Two St. Johns River 

Tributaries Receiving Septic Tank Effluent, Duval 

County, Florida

By Shaun M. Wicklein

ABSTRACT

Tributary streamflow to the St. Johns River 

in Duval County is thought to be affected by septic tank leachate from residential areas adjacent to 

these tributaries. Water managers and the city of 

Jacksonville have committed to infrastructure 

improvements as part of a management plan to 

address the impairment of tributary water quality. 

In order to provide data to evaluate the effects of 

future remedial activities in selected tributaries, 

major ion and nutrient concentrations, fecal 

coliform concentrations, detection of wastewater 

compounds, and tracking of bacterial sources 

were used to document septic tank influences on 

the water quality of selected tributaries.

The tributaries Fishing Creek and South 

Big Fishweir Creek were selected because they 

drain subdivisions identified as high priority locations for septic tank phase-out projects: the Pernecia and Murray Hill B subdivisions, respectively. 

Population, housing (number of residences), and 

septic tank densities for the Murray Hill B subdivision are greater than those for the Pernecia subdivision.

Water-quality samples collected in the 

study basins indicate influences from ground 

water and septic tanks. Estimated concentrations 

of total nitrogen ranged from 0.33 to 2.86 milligrams per liter (mg/L), and ranged from less than 

laboratory reporting limit (0.02 mg/L) to 0.64 mg/L 

for total phosphorus. Major ion concentrations 

met the State of Florida Class III surface-water 

standards; total nitrogen and total phosphorus 

concentrations exceeded the U.S. Environmental 

Protection Agency Ecoregion XII nutrient criteria 

for rivers and streams 49 and 96 percent of the 

time, respectively. Organic wastewater compounds 

detected at study sites were categorized as detergents, antioxidants and flame retardants, manufactured polycarbonate resins, industrial solvents, and 

mosquito repellent. The most commonly detected 

compound was para-nonylphenol, a breakdown 

product of detergent. Results of wastewater sampling give evidence that stream water in the study 

basins is affected by septic tank effluent.

Fecal coliform bacteria concentrations were 

measured on a monthly basis; of 115 samples, 

63 percent exceeded the State of Florida fecal 

coliform bacteria standard for Class III surface 

waters of 800 colonies per 100 milliliters of water 

on any 1 day. Fecal coliform bacteria concentrations ranged from less than 20 colonies per 

100 milliliters of sample to greater than or equal 

to 160,000 colonies per 100 milliliters of sample. 

Antibiotic resistance patterns of fecal coliform 

bacteria were used to identify the sources of fecal 

coliform bacteria. Significant sources of fecal 

coliform bacteria included wild animals, dogs, 

and humans. A majority of the fecal coliform bacteria were classified to be from human sources. 

Because the primary source of fecal coliform bacteria is from human sources, and most likely septic tank effluent, management of human sources 

may substantially improve microbiological water 

quality in both the Fishing Creek and South 

Branch Big Fishweir Creek basins.
2 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

INTRODUCTION

Water managers in the lower St. Johns River 

basin and the city of Jacksonville are committed to 

improve the quality of waterways that contribute flow 

to the St. Johns River, an American Heritage River. 

The quality of tributary streamflow to the St. Johns 

River in Jacksonville is thought to be affected by septic tank leachate from residential areas adjacent to the 

tributaries (Dana Morton, city of Jacksonville, Division of Air and Water Quality, oral commun., 1999). 

Shallow ground water in these areas likely is the vehicle that transports fecal coliforms and nutrients from 

septic tank leachate to the surface water. The installation of sanitary sewer systems in the city of Jacksonville for areas presently on septic tank systems is one 

step being taken to cleanup waterways (City of Jacksonville, 2000).

Although research has been done on the efficiency of septic tank systems to treat wastes, and the 

deterioration of these systems over time has been studied, the effect of the removal of septic tank systems on 

the receiving ground and surface waters has not been 

widely studied. Documentation of water-quality conditions prior to and after replacement of septic tank 

systems by a centralized system is needed to evaluate 

the effects of remedial activities. The associated 

hydrologic conditions under which the water quality is 

evaluated should be documented to isolate the impact 

of the septic tank removal from other factors that can 

affect water quality. The study of environmental 

effects of septic tank removal will help to further the 

understanding of human impacts on water quality in 

river systems.

The U.S. Geological Survey (USGS), in cooperation with the city of Jacksonville Air and Water-Quality 

Division, began a 4-1/2-year study to evaluate the 

effects of septic tank removal on two tributaries to the 

St. Johns River in April 1999. The tributaries Fishing 

Creek and Big Fishweir Creek were selected because 

they drain neighborhoods identified by Jacksonville 

Electric Authority (JEA) as priority locations for septic tank phase-out projects (fig. 1). The neighborhoods 

are the Pernecia and Murray Hill B subdivisions, 

which coincide with Fishing Creek and Big Fishweir, 

respectively.

Major ion and nutrient concentrations, detections of organic wastewater compounds, and fecal 

coliform concentrations were documented in order to 

evaluate the effects of septic tank removal projects on 

stream water quality. Bacterial source tracking, as 

described by Harwood and others (2000), was 

included in sampling efforts to further define septic 

tank influence on the water quality of the tributaries.

Purpose and Scope

The objective of this study was to evaluate 

the effects on water quality in two tributaries to the 

St. Johns River resulting from the replacement of 

residential septic tank systems by a centralized sewer 

system. The study, as planned, was divided into two 

phases. The first phase was to document baseline 

water-quality conditions prior to connection of targeted areas (fig. 1) to a centralized sewer system. 

The second phase was to document changes in waterquality constituent concentrations that may result from 

installation of sanitary sewer systems and removal of 

septic tank systems in targeted areas. Unforeseen 

delays, however, in the installation of sanitary sewer 

systems affected evaluation of hydrologic and waterquality conditions following planned sanitary sewer 

system installation.

This report, therefore, documents baseline 

hydrologic and water-quality conditions occurring in 

2000-2002 prior to removal of septic tanks and installation of a sanitary sewer system. Basin characteristics 

are documented to facilitate transferability of results 

to other locations. The results of sampling for major 

ions (semi-annually), nutrients (quarterly), organic 

wastewater compounds (annually) and fecal coliform 

bacteria (monthly) at two sites in each basin are 

summarized along with streamflow measurements 

(quarterly). Bacterial source tracking, used to determine the source of fecal coliform bacteria, is 

described.

Description of Study Area

The geologic deposits important to this 

study include the sediments from land surface to 

a depth of about 100 feet (ft). The sediments consist 

mostly of unconsolidated fine to medium grained 

quartz sand with some clay, shell, and limestone. 

These unconsolidated sediments form the surficial 

aquifer system. Throughout most of Duval County, 

the water table in the surficial aquifer system is 

within 5 ft of land surface (Causey, 1975). Locally, 

the depth to water is about 10-12 ft. The surficial 

aquifer system is recharged primarily by rainfall.
Introduction 3

MAYPORT

FORT GEORGE

ISLAND

MANDARIN

ATLANTIC

BEACH

JACKSONVILLE

BEACH

JACKSONVILLE

NEPTUNE

BEACH

St. r John e s v Ri

St h . Jo ns R

vi er

Or R tega iv r e

AT L A N T I C O C E A N

N a s s a u R i v e r

Intra-coastal

waterway

Cedar River

DUVAL COUNTY

CLAY COUNTY

BAKER COUNTY

ST. JOHNS COUNTY

NASSAU COUNTY

95

10

17

202

295

90

295

90

228

95

1

10

301

024 1

2 4

5 MILES

0

1 3

1 3 5 KILOMETERS

30°15′

30°30′

82°00′ 45′ 81°30′

Base modified from U.S. Geological Survey digital data, 1:100,000, 1985

Albers Equal-Area Conic projection

DUVAL

COUNTY

STUDY AREA

FISHING CREEK

BASIN

SOUTH BRANCH

BIG FISHWEIR CREEK

BASIN

¤

¤

1

2

p3

¤2

EXPLANATION

RAINFALL

MONITORING SITE

AND NUMBER

p3 DISCHARGE

MONITORING SITE

AND NUMBER

Figure 1. Location of study areas and selected monitoring sites in Jacksonville, Duval County, Florida (site numbers refer 

to table 1).
4 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

Discharge from the surficial aquifer system occurs 

by evaporation, transpiration by plants, seepage into 

surface-water bodies, leakage into the underlying 

rocks, and from discharging wells. Underlying the 

surficial aquifer system are about 400 ft of mostly 

fine-grained, clay sediments that also include some 

shell, sand, or limestone. These sediments make up the 

intermediate confining unit. Underlying the intermediate confining unit is a thick sequence (greater than 

1,600 ft) of carbonate rocks that form the artesian 

aquifer system (Phelps, 1994).

The topography of Duval County is controlled 

by a series of ancient marine terraces (Cooke, 1945) 

that were formed due to glacial activity during the 

Pleistocene Epoch when the sea was relatively stationary at various levels higher than present-day sea level. 

Six marine terraces are recognized in Duval County: 

the Coharie, Sunderland, and Wicomico terraces that 

range in altitude from 215 to 70 ft in the western part 

of the county; the Penholoway and Talbot terraces that 

form a coastal ridge at altitudes from 70 to 25 ft; and 

the Pamlico terrace at altitudes below 25 ft, which 

forms the low coastal plain throughout most of the 

eastern and central parts of the County (Anderson, 

1972). The study areas occur at elevations associated 

with the Talbot and Pamlico terraces. Much of the 

study areas likely were barrier islands during deposition of the Talbot Formation (Cooke, 1945).

Soils in the study areas generally are somewhat 

to very poorly drained. Sandy and loamy sediments are 

present on rises, knolls, and flats. Creek bottoms are 

made up of very poorly and poorly drained Surrency 

soil types that are present in nearly level depressions 

and on flood plains (U.S. Department of Agriculture, 

1998). The upland soil types generally are fine sands of 

Pelham, Mascotte, and Sapelo, which are poorly 

drained and present on nearly level flats and flatwoods.

About 75 square miles (mi2) of surface water 

covers parts of Duval County (the County has a total 

area of about 840 mi2

). Two major rivers and their 

tributaries drain the County: the St. Johns River and 

the Nassau River. Numerous smaller streams drain to 

the Intra-coastal waterway or the Atlantic Ocean. 

Because parts of the County are relatively flat, some 

drainage divides in low areas are indistinct. During 

high-flow conditions, water can discharge into another 

drainage basin. The average runoff for streams in the 

County is about 50 percent greater than that of the 

State for Florida, as a whole (Anderson, 1972). This 

likely is a result of impermeability of sediments underlying the surficial aquifer system in Duval County.

The climate of Duval County is humid subtropical 

and is characterized by long, warm, humid summers 

and mild winters. Freezing temperatures may occur 

during the winter months, but are rare because Duval 

County borders the Atlantic Ocean and is close to the 

Gulf Stream, which produces moderate winter temperatures. In an average year, about 65 percent of the total 

annual precipitation occurs from June to October, with 

the remaining precipitation more or less evenly distributed throughout the remainder of the year. Typical 

weather patterns for Duval County include frontal 

activity during the winter months, causing widespread 

rainfall and short periods of cooler temperature, and 

scattered thunderstorm activity during the summer 

months. The 100-year, 1868-1967, average rainfall 

recorded at Jacksonville was 51.52 inches (Anderson, 

1972).

Rainfall represents the largest input of water to 

the study areas, and is the main climatic factor affecting the variation in surface-water flows for Duval 

County. Water supplied by rainfall is depleted by 

runoff, evapotranspiration, and seepage to the aquifers. 

In most parts of Duval County, 10-16 inches of rainfall 

enters the surficial aquifer system in a year (Anderson, 

1972). The amount of water that passes through the 

surficial aquifer to the Floridan aquifer probably is 

insignificant because artesian flow conditions exist in 

the eastern two-thirds of the County, and because 

numerous swampy areas indicate poor subsurface 

drainage. Thus, in most parts of the County, the majority of the water that enters the surficial aquifer system 

leaves the aquifer as seepage to streams, and by 

evapotranspiration. Therefore, the amount of runoff 

generally is the difference between rainfall and 

evapotranspiration.

Data Collection and Analysis

Two basins were selected for this study: Fishing 

Creek (fig. 2) and South Branch Big Fishweir Creek 

(fig. 3). Surface-water-quality sampling sites were 

selected at two locations in each of the study basins: 

one upstream and one downstream from the area in 

which a sanitary sewer system will be installed and 

septic tanks will be removed (table 1). Water-quality 

data were collected monthly to document conditions 

prior to the installation of a sanitary sewer system 

(and subsequent discontinuation of septic tank use). 

Streamflow measurements were made at the time of 

sampling events (quarterly).
Introduction 5

Table 1. Data collection and compilation sites, Jacksonville, Florida

[NOAA, National Oceanic and Atmospheric Administration; NLMOF, Naval Atlantic Meteorology and Oceanography Facility Jacksonville, 

Florida; USGS, U.S. Geological Survey. Data type: R, rainfall; D, discharge; P, periodic water-quality; --, not available; NA, not applicable. 

Map number shown in figures 1, 2, and 3]

Map

number

Site name 

and

identification number

Latitude Longitude

Drainage 

areaa

(square 

miles)

a

Drainage area from U.S.Geological Survey, 2003, Water resources data, Florida, water year 2002, volume 1A.

Data 

type

Source of 

data

1 Jacksonville International Airport

(084358)

30° 30' --" 81° 42' --" NA R NOAA

2 Naval Air Station Jacksonville

(722065)

30° 14' --" 81° 40' --" NA R NLMOF

3 Ortega River at Jacksonville

(02246300)

30° 14' 50" 81° 47' 49" 30.9 D USGS

4 Fishing Creek at Wesconnet Boulevard

(02246435)

30° 14' 10" 81° 44' 22" .76 D, P USGS

5 Fishing Creek at 110th Street

(0226437)

30° 14' 27" 81° 43' 57" 1.27 D, P USGS

6 South Branch Big Fishweir Creek at Casssat Avenue 

(02246465)

30° 17' 35" 81° 43' 51" .43 D, P USGS

7 South Branch Big Fishweir Creek at Blanding Boulevard 

 (02246467)

30° 17' 35" 81° 43' 27" .67 D, P USGS

BASIN

BOUNDARY

295

Astrid Dr.

Penny La.

Coffey La. Jonnie Cir. W. Jonnie Cir. E.

Elemgrove Ave..

Viola La.

Seaboard Ave..

111th St.

Goodman Rd.

Anderson Rd.

Nancy Dr.

Joy Dr. S.

Joy Dr. W.

Pernecia St.

Hilda St.

Karen St.

Judy Dr.

Oaklane Dr.

Nora Rd.

Aline Rd.

Blanding Blvd.

Gaskins Rd.

Kohn St .

118th St.

Turnett Rd.

Jammes Rd.

Erma St.

Flowers Ave.

120th St.

118th St.

Ortega Park Blvd.

Vista Verde St.

Morse Ave.

Ovella Rd.

Hurdia Rd.

105th St.

110th St.

Wesconnet Blvd.

Fishing Creek

SAND PIT

p

p

4

5







0 .25 .5 MILE

0 .25 .5 KILOMETER





Base modified from U.S. Geological Survey

digital data, 1:100,000, 1985

Albers Equal-Area Conic projection

STUDY AREA

DRAINAGE

BASIN

DUVAL

COUNTY

PERNECIA

SUBDIVISION

EXPLANATION

HYDROLOGY

WETLANDS

p4 DISCHARGE AND WATER-QUALITY

MONITORING SITE AND NUMBER

STREAMFLOW DIRECTION

Figure 2. Streamflow and water-quality data collection sites for Fishing Creek basin, Jacksonville, Florida (site 

numbers refer to table 1).
6 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

BASIN

BOUNDARY

C

de

a r Ri ver

Sou t

g

h

h

Bra n c

Bi

Fi s hweir Cr e ek

No r t

i

h

n h

g

Bra

c

Bi

F shwe ir Cre

ek

ditch



	

 

0 .25 .5 MILE

0 .25 .5 KILOMETER

Base modified from U.S. Geological Survey

digital data, 1:100,000, 1985

Albers Equal-Area Conic projection Mikael Ave. Garth Ave.

Astral St. Normandy Blvd.

Attleboro St.

Truman Ave.

Lois Ave.

Pangola Dr.

Comanche St.

Mohawk St.

Denaud St.

Alta Vista St.

Labelle St.

Seba St.

Velma St.

Redrac St.

Orton St.

Bagnal Rd.

Carder St.

Hollycrest Dr.

Baycrest Rd.

Woodcrest Rd.

Poppy Dr.

Royce Ave.

Quan Dr.

Clarendon Rd.

Coronet Dr.

Glenwood Ave.

Pangola Dr

Mull St.

.

Orton St.

Neva St.

Ellis Rd. S.

Weeks Rd.

Lasota Ave.

Radio Ln.

Waterside Dr.

Park St.

Wyn St.

Camille Ave.

Janice Cr. S.

Marelene Ave.

Golfview St. Indberg Dr. Iniblick Dr.

Hyde Grove

Ave.

Vista Ave.

Hyde Park Cr.

Lexington Ave.

Shirley Ave.

Irvington Ave.

Beverly Cr.

Apap

Apap

Cardinal Blvd.

Sefa Cr. N.

Shelby Ave.

Merrimac Ave.

St. Johns Ave.

Roosevelt Blvd.

Fair St.

Blanding Blvd.

Wheeler Ave.

Fishweir Ave.

Stimson St.

Dakar St.

Yerkes St.

Amherst St.

Tunis St.

Jersey St.

Ellis Rd. S.

Post St.

Polaris St.

French St.

Kerle St.

Lawnview St.

Sappho Ave.

Ingleside Ave.

Whole St.

Dancy St. Antisdale St.

Lark St.

Scotten Rd.

Woodruff Ave.

Randolph St.

Kingsbury St.

Hercules Ave.

Alpha Ave.

Delta Ave.

Woolman Ave.

Plymouth St.

Woycoff Ave.

Atherine Te.

Lizabeth Te.

Louisa Te.

Eadley Te.

Prunty Ave.

Hamilton St.

Lamboll Ave.

Cassat Ave.

Weeks Rd.

Plymouth Pl.

Lake Shore Blvd.

DRAINAGE

BASIN

DUVAL

COUNTY

STUDY AREA

p p

6

7

EXPLANATION

HYDROLOGY

p6 DISCHARGE AND WATER-QUALITY

MONITORING SITE AND NUMBER

STREAMFLOW DIRECTION

MURRAY HILL B

SUBDIVISION

Figure 3. Streamflow and water-quality data collection sites for South Branch Big Fishweir Creek basin, 

Jacksonville, Florida (site numbers refer to table 1).
Introduction 7

In order to describe basin characteristics, information on the size of drainage areas, soil characteristics (soil type and drainage characteristics), land use, 

septic tank and housing density, and water use in the 

area (from utility records) were compiled. These basin 

characteristics aided in the interpretation of waterquality data, and also will help with the transferability 

of the results to other areas where sanitary sewer 

systems are to replace septic tanks.

Water samples were collected at four sites 

(figs. 2 and 3) during 2000-2002. Samples for major 

ions were collected semi-annually during wet (JuneOctober) and dry (November-May) seasons. Nutrient 

samples were collected quarterly at times when two of 

the quarterly sampling events corresponded to the 

semi-annual sampling events. Large nutrient loads can 

be transported during storm events, and it is possible 

that nutrients from septic tank drain fields might be 

flushed out of the ground-water system at these times. 

For this reason, major ion and nutrient samples also 

were collected for three storm events during the study 

period.

Four water samples were collected at each site 

and analyzed for organic compounds commonly found 

in wastewater. Three of the four samples were collected during low-flow and one during a storm event. 

Fecal coliform bacteria samples were collected 

monthly. Water samples also were collected four times 

during the study and analyzed for antibiotic resistance 

patterns used to classify fecal coliform bacteria 

sources. All samples were collected according to 

methods presented in the USGS National Field 

Manual for the Collection of Water-Quality Data 

(Wilde and others, 1998).

Streamflow was measured at each site when 

collecting quarterly water-quality samples and during 

storm events. Measurements were made using conventional current meter methods described by Rantz and 

others (1982). Field properties, consisting of water 

temperature, specific conductance, dissolved oxygen 

concentration, and pH, were measured using a multiparameter water-quality meter calibrated according to 

the meter’s operational manual and methods described 

by Wilde and others (1998). Field measurements were 

made whenever water samples were collected.

Water samples collected during the study were 

sent to several laboratories for analysis. Major ions 

and nutrients were analyzed at the USGS Ocala Water 

Quality and Research Laboratory in Ocala, Florida, 

according to methods presented in Fishman and Friedman (1989) and the U.S. Environmental Protection 

Agency (2003). Constituents analyzed as part of the 

major ion and nutrient sampling are listed in 

appendix 1. Samples for analyses of organic wastewater compounds were processed at the USGS National 

Water-Quality Laboratory in Denver, Colorado, 

according to methods presented in Zaugg and others 

(2002). Compounds analyzed included alkylphenol 

ethoxylate nonionic surfactants and their degradates, 

food additives, fragrances, antioxidants, flame retardants, plasticizers, industrial solvents, disinfectants, 

fecal sterols, polycyclicaromatic hydrocarbons, and 

high-use pesticides (app. 2). Samples collected for 

fecal coliform bacteria analyses, using the most-probable-number method, were analyzed at the Florida 

Department of Health laboratory in Jacksonville, 

Florida, according to methods presented in Clesceri 

and others (1998, p. 9-48).

Antibiotic resistance patterns of fecal coliform 

bacteria from water samples were analyzed by the 

Department of Biology, University of South Florida, 

Tampa, Florida, using materials, methods, and statistical analysis described by Harwood and others (2000). 

Water samples were collected at sites, chilled to 

4 degrees Celsius, and shipped to the University of 

South Florida. Fecal coliform bacteria were isolated 

from water samples within 8 hours of sample collection by membrane filtration using mFC agar. A 

known-source library of fecal coliform bacteria isolates was used for classification of fecal coliform 

bacteria isolated from water samples (Harwood and 

others, 2000). The library was developed in the 

Jacksonville area from approximately 1998-2000 and 

contains 1,777 human-origin fecal coliform bacteria 

isolates and 4,367 animal-origin fecal coliform bacteria isolates. Wiggins and others (2003) concluded that 

a multi-watershed library of at least 2,300 samples is 

needed for reliable classification of fecal coliform bacteria within the region of collection. The library used 

for this study contains 6,144 fecal coliform bacteria 

isolates, which were collected in the Jacksonville area. 

The library is not representative of all wildlife, but 

contains 337 fecal coliform bacteria isolates from a 

limited number of species: rabbits, racoons, ducks, 

wood storks, night heron, and egrets. This library was 

considered acceptable to use for this study.

The antibiotic resistance patterns of fecal 

coliforms isolated from stream-water samples were 

determined using eight antibiotics: amoxicillin, 

gentamicin, cephalothin, ofloxacin, erythromycin, 
8 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

tetracycline, moxalactam, and chlortetracycline 

(Dr. Valerie Harwood, Department of Biology, 

University of South Florida, written commun., 2002). 

Discriminant analysis was used to classify individual 

sample isolates into groups on the basis of the values 

of several classification variables (Harwood and others, 2000). Fecal coliform bacteria isolates were categorized into one of five potential sources: chicken, 

cow, dog, human, and wild animal. Results from the 

analysis of antibiotic resistance patterns of fecal 

coliform bacteria are assessed for accuracy of fecal 

coliform bacteria isolates classification by comparing 

to known sources. The rate of correct classification of 

fecal coliform bacteria isolates from known sources 

gives an indication of how accurately sample results 

represent the actual source of fecal coliform bacteria. 

Isolates of fecal coliform bacteria were correctly classified from known sources for a two-way split at a rate 

of 69 percent for human sources and an average correct classification rate of 78 percent for combined 

animal sources and for a six-way split at a rate of 

54 percent for human, 57 percent for chicken, 

54 percent for cow, 95 percent for dog, 72 percent 

for swine, and 51 percent for wild animal sources 

(Harwood and others, 2000). Water samples for this 

study were split into five classification catagories 

(chicken, cow, dog, human, and wild animal) that 

likely would produce a correct classification rate less 

than that of a two-way split and similar to a six-way 

split. Given the type of bacteria isolated (fecal 

coliform) and the database used for discriminant 

analysis of fecal coliform bacteria isolates, the 

probability of fecal coliform bacteria isolates being 

assigned to any one of the classification categories by 

chance alone is 20 percent. The probability of chance 

classification (20 percent) of fecal coliform bacteria 

isolates was considered the lower limit for considering 

any one source category to be a significant contributor 

of fecal coliform bacteria to the water.

Quality-assurance procedures were followed for 

collection and processing of water-quality samples. 

These procedures included checking and calibrating 

equipment daily as well as collecting additional samples for quality control. Analysis of quality-assurance 

samples provided information on the potential for 

sample contamination during collection, processing, 

and laboratory analysis.

Quality-assurance samples consisted of one 

field blank and three duplicate samples for major ions, 

one field blank and six duplicate samples for nutrients 

(nitrogen and phosphorus species), one field blank and 

two duplicate samples for analyses of organic wastewater compounds, and six field blanks for bacteria. 

Water samples for quality control were collected on 

randomly selected days at randomly selected sites 

during the study period.

Field blanks provide information on possible 

contamination introduced to the sample during collection and processing (handling) of the sample in the 

field. Field blank samples were prepared by pouring 

water certified to be free of the analytes of interest 

through all sampling equipment as if an environmental 

sample was being processed. Constituent concentrations for field blank samples were less than the 

method-reporting limits for all samples. Duplicate 

quality-assurance samples were collected simultaneously with scheduled water samples, and were 

processed using the same equipment for both samples. 

Collection of duplicate samples provided information 

on the uniformity of sample handling in the field and 

sample processing by the laboratory. The small nature 

of the duplicate data set, six or less sample sets per 

constituent family, did not allow for an acceptable 

statistical comparison of quality-assurance and 

environmental water samples. Constituent concentrations for duplicate quality-assurance samples and 

environmental water samples were compared. The 

comparison indicated no contamination due to 

collection, handling, or processing.

Data were graphically compared and statistically tested to evaluate whether any differences in 

constituent concentrations were observed between 

sites and basins. Data were analyzed for similarities 

and differences between upstream and downstream 

sites. Basin characteristics were evaluated along 

with the water-quality data to determine possible 

relations between observed water-quality constituent 

concentrations.

Summary statistics are presented and a nonparametric rank sum test (Helsel and Hirsch, 1992) 

was used to determine whether differences between 

sites in the study areas were statistically significant. 

The rank sum test makes no assumption about the data 

distribution and was used because the data were not 

normally distributed. The rank sum test uses a statistic 

called a p-value. When the p-value is less than the 

chosen confidence level (in this study, 0.05), sample 

populations are considered statistically different. The 

lower the p-value, the more significant the difference.
Basin Characteristics 9

BASIN CHARACTERISTICS

Duval County originally was comprised of 

many small towns and unincorporated areas, each with 

its own public services and infrastructure. In the 

1970’s the small towns and unincorporated areas in 

Duval County were combined into the unified city of 

Jacksonville. As a result, the city of Jacksonville 

contained many areas that had little or no centralized 

public water or sanitary sewer systems. The two neighborhoods of interest to this study, the Pernecia and 

Murray Hill B subdivisions, consist of residences 

serviced by individual septic tank systems. As part of 

infrastructure improvements addressed by the Better 

Jacksonville Plan (City of Jacksonville, 2000), these 

subdivisions were scheduled for installation of sanitary sewer systems and removal of septic tank systems.

The Pernecia and Murray Hill B subdivisions 

are suburban residential neighborhoods that are intersected by the study basins, Fishing Creek and South 

Branch Big Fishweir Creek, respectively (figs. 2 and 

3). Both subdivisions contain single-family homes, 

duplexes, and some small-business development along 

the major four-lane roadways. Greater than 90 percent 

of the land use in each basin is single- or multi-family 

residences located along two-lane streets with swale 

drainage ditches (Amy McGrath, Jacksonville Electric 

Authority, written commun., 2002). The Pernecia 

subdivision covers an area of about 193 acres, of 

which 156 acres drain to Fishing Creek. The Murray 

Hill B subdivision is about 465 acres, of which 

154 acres drain to South Branch Big Fishweir Creek. 

The population and number of residences and septic 

tanks in the Pernecia and Murray Hill B subdivisions 

are provided in table 2.

Exact totals for residential water and sewer 

usage for the Pernecia and Murray Hill B subdivisions 

are difficult to obtain because residences are serviced 

by individual water supply wells and septic tank 

systems. Study area reconnaissance indicated that no 

National Pollutant Discharge Elimination System 

(NPDES) permitted discharges exist within or 

upstream from the study basins and no point-source 

discharges were observed in the study basins 

(Dana Morton, city of Jacksonville, Division of 

Air and Water Quality, oral commun., 2002). Records 

of the JEA (2002) indicate that the average annual 

water and sewer usage per residence was about 

10,700 and 8,860 cubic feet, respectively, between 

October 1, 2001, and September 30, 2002 (table 3). 

These numbers are based on the Duval County average 

and likely represent the average usage for any one 

residence during the year sampled. Given the diversity 

of residences accounted for in the JEA (2002) report, 

it is likely that the average water and sewer usages 

presented in table 3 are representative of the Pernecia 

and Murray Hill B subdivisions.

Fishing Creek

The Fishing Creek basin (figs. 1 and 2) is 

located west of the St. Johns River and joins the 

Ortega River south (upstream) of its confluence with 

the Cedar River. Land areas in the basin generally are 

low lying with little topographic relief. The downstream end of the study area is located approximately 

2 miles upstream from the confluence with the Ortega 

River. The Fishing Creek study basin has a drainage 

area of 812.8 acres and contains 156 acres of the 

Pernecia subdivision.

Table 2. Subdivision and study basin characteristics, Jacksonville, Florida, 2000

[Source of data: Amy McGrath, Jacksonville Electric Authority, written commun., 2002]

Subdivision

Associated 

study 

basin

Study basin 

drainage area

(acres)

Subdivision

Intersecting 

areaa

Area (acres)

(acres)

Population

(count)

Residences

(count)

Septic tanks

(count)

Pernecia Fishing Creek 812.8 193.2 522 246 251 156

Murray Hill B South Branch Big

Fishweir Creek

428.8 464.8 2,766 1,077 1,245 154

a

Area within the subdivision that drains to the study basin.
10 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

Upland areas in the Fishing Creek basin that 

drain to the stream channel tend to be relatively low 

and flat. The creek generally is narrow, 25 ft or less in 

width, with definitive banks that are 3-6 ft high, especially in the lower reaches of the basin. During highflow conditions, the stream has overflowed its banks 

and spread into the adjacent neighborhood; conversely, 

during extended droughts, the stream has become 

intermittent for extended periods. Two distinct areas 

can be characterized in the Fishing Creek study basin: 

the western part of the basin upstream from Blanding 

Boulevard, and the northeastern part of the basin 

downstream from Blanding Boulevard. In the 

upstream part of the basin, west of Blanding Boulevard, the stream channel flows through densely 

wooded areas and becomes poorly defined, expanding 

into low-lying swampy areas. The upstream part of the 

basin is less populated, especially in the far western 

part. East of Blanding Boulevard, the channel is welldefined and meanders through a wooded riparian zone 

in a moderately populated suburban residential area 

(the Pernecia subdivision). Based on 2000 data 

(table 2), population, housing (number of residences), 

and septic tank densities for the Pernecia subdivision 

were 2.7 people per acre, 1.3 houses per acre, and 

1.3 septic tanks per acre, respectively. Due to the nonuniformity of housing distribution in the basin, densities likely are larger for areas in the northeastern part 

of the basin where the Pernecia subdivision is located.

Big Fishweir Creek

The Big Fishweir Creek basin (figs. 1 and 3) is 

located west of the St. Johns River and joins the 

Ortega River at its confluence with the St. Johns River. 

The North and South Branches of Big Fishweir Creek 

come together approximately 0.75 miles (mi) 

upstream from the mouth. The study basin is located 

on the South Branch of Big Fishweir Creek less than 

0.25 mi upstream from the confluence of the North 

Table 3. Residential water use, Duval County, Florida, 

2002

Usage 

type

Average usage for individual accountsa

a

Based on Jacksonville Electric Authority 2002 Annual Report.

Annual

(cubic feet)

Daily

(cubic feet)

Daily

(gallons)

Water 10,700 29.3 219

Sewer 8,860 24.3 182

and South Branches. Land areas within the basin generally are low-lying with moderate topographic relief. 

The South Branch Big Fishweir Creek study basin has 

a drainage area of 428.8 acres and contains 154 acres 

of the Murray Hill B subdivision.

The South Branch Big Fishweir Creek is 

narrow, 20 ft or less, with banks approximately 3-5 ft 

high. The stream channel is modified throughout the 

basin and has sections of man-made channel armoring 

in the upper and middle reaches between Lakeshore 

Boulevard and Park Street. The channel in the upper 

reaches of the basin has been straightened and is 

deeply incised for drainage purposes. The basin divide 

in the upper basin is poorly defined because in this 

area the creek is connected to the Cedar River basin to 

the west. The riparian zone of the creek generally is 

lightly wooded and characterized by grassy areas 

common in suburban backyards. The South Branch 

Big Fishweir Creek is not known to be intermittent; a 

small amount of base flow generally is present even 

during extended dry periods. High flows usually are 

contained within the banks except during extreme 

events. Upland areas draining to the stream channel in 

the South Branch Big Fishweir Creek basin have 

greater slope than those in the Fishing Creek basin, 

especially in the lower parts of the basin. Based on 

2000 data (table 2), population, housing (number of 

residences), and septic tank densities for the Murray 

Hill B subdivision were 6.0 people per acre, 

2.3 houses per acre, and 2.7 septic tanks per acre, 

respectively.

STREAMFLOW

Measurements of streamflow were made 

approximately quarterly when water-quality samples 

were collected and during storm events. The measured 

flows ranged from 107 cubic feet per second (ft3

/s) at 

Fishing Creek at 110th Street to 0.02 ft3/s at the South 

Branch Big Fishweir Creek at Cassat Avenue (table 4). 

Three of the four measurement sites had two or more 

observations of no flow. The only site where no-flow 

conditions were not observed was the South Branch 

Big Fishweir at Cassat Avenue site. The downstream 

site on the South Branch of Big Fishweir Creek 

(at Blanding Boulevard) had two observations of no 

flow, but these observations were noted as being 

caused by backwater from debris. It is likely that a 

small amount of flow occurred at the observation 

times at the South Branch of Big Fishweir Creek at 

Blanding Boulevard site.
Streamflow 11

Measured streamflows for Fishing Creek generally were greater than those for South Branch Big 

Fishweir Creek, and in both basins streamflow 

increases from upstream to downstream (fig. 4). Based 

on calculations from periodic streamflow measurements, the runoff per unit area is greater in the Fishing 

Creek basin. However, the South Branch of Big Fishweir basin has a higher housing density, which generally would result in increased runoff per unit area, so it 

is possible that soil types and inflow from the surficial 

aquifer are the causes of increased runoff per unit area 

in the Fishing Creek basin.

Streamflow measurements were somewhat 

evenly distributed throughout the range of flows 

measured (fig. 4). The relatively small (14 or less per 

site) number of streamflow measurements made during the study period can easily be skewed from the 

normal distribution of measurements by outliers. Skew 

in the measured streamflows is indicated at the Fishing 

Creek at Wesconnet Boulevard site where 11 measurements were made, 2 of which were during storm 

events. This tended to bias percentiles of the sample 

set above the median streamflow, although a majority 

of flows were measured at less than 0.50 ft3

/s.

Streamflow was not measured continuously at 

sites, and it was unknown whether periodically 

measured streamflows were representative of the range 

of hydrologic conditions that may occur at study sites. 

Comparisons were made at a continuous-monitoring 

streamflow site at the Ortega River at 103rd Street 

near Jacksonville (map number 3, fig. 1) to determine 

whether periodically measured streamflows were 

representative of the range of hydrologic conditions 

during the study. Both of the study basins lie east of 

the drainage area included at the Ortega River at 103rd 

Street site, but the site is close enough to the study 

basins that the observed hydrologic conditions are 

considered representative of those at the study sites. 

A comparison of daily mean streamflows provides an 

indication of the range of hydrologic conditions 

observed at study sites (fig. 5).

Daily streamflows observed during the study 

period (January 1, 2000, to September 30, 2002) tend 

to be less then those observed over the period of record 

(January 1, 1965, to September 30, 2002) at the Ortega 

River at 103rd Street site. This is consistent with the 

below-average rainfall observed during the study 

period (table 5). The median for days when samples 

were taken at Fishing Creek and South Branch Big 

Fishweir Creek closely represents the study period and 

long-term medians. The range of conditions for sampled days is slightly less than that for the study period 

and long-term period of record. Given the small 

number of streamflow observations at sampling sites, 

the observed hydrologic conditions represent the longterm hydrologic conditions fairly well.

Table 4. Measured streamflow summary for data collection sites, Jacksonville, Florida

[USGS, U.S. Geological Survey; discharge values are in cubic feet per second; e, estimated. Map number shown in figures 1, 2, and 3]

Map 

number

Site name 

and

USGS identification number

Number 

of 

measurements

Maximum 

measured 

discharge

Date

Minimum 

measured 

discharge

Date

Observations 

of 

no-flow

4 Fishing Creek at Wesconnet Boulevard

(02246435)

11 75.4 9/15/2001 .07 9/5/2000 7

5 Fishing Creek at 110th Street

(0226437)

13 107 9/15/2001 .07 7/11/2000 4

6 South Branch Big Fishweir Creek

at Casssat Avenue 

(02246465)

14 9.87 9/15/2001 .02 7/11/2000 0

7 South Branch Big Fishweir Creek

at Blanding Boulevard 

 (02246467)

13 15.9 9/15/2001 .10e 6/12/2000

7/11/2000

2a

a

No observable or measurable flow due to backwater from downstream debris causing ponded conditions.
12 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

SITES

Wesconnet Blvd. 110th St. Cassat Ave. Blanding Blvd.

1,000

100

10

1.0

.10

0.01

MEASURED STREAMFLOW,

IN CUBIC FEET PER SECOND

11 13

14

13 x

x

o

x

x

o

x

x

FISHING CREEK SOUTH BRANCH

BIG FISHWEIR CREEK

11 number of values

EXPLANATION

SCHEMATIC BOXPLOT

x

x

x

x

x

x

o

o

o

ooo

75th percentile

median

25th percentile

lower outside

lower detached

upper detached

upper outside

Note: Boxes with same

colors are not significantly

different.

Figure 4. Measured streamflow at data collection sites, Jacksonville, Florida, 2000-2002 (site numbers refer to 

table 1).

13 number of values

EXPLANATION

SCHEMATIC BOXPLOT

x

x

x

x

x

x

o

o

o

ooo

75th percentile

median

25th percentile

lower outside

lower detached

upper detached

upper outside

SUBSET OF STREAMFLOW VALUES

13,580 x

x 1,004 13 13 xx

xxxxxxxxxxxxxxxx

xx

xxxxxxxxx

xxx

x

xxxxxxxxxxxxxxxxxx

o

ooo

xxxxxxxxxxxxxxxxxxxxxxx

x

o

o

x

o

x

x

ORTEGA

RIVER

1965 - 2002

(PERIOD OF

RECORD)

ORTEGA

RIVER

2000 - 2002

(STUDY

PERIOD)

ORTEGA

RIVER

(1)

ORTEGA

RIVER

(2)

10,000

1,000

100

10

1

0.01

0.1

DAILY MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

(1) DAYS WHEN

FISHING CREEK

WAS MEASURED

(2) DAYS WHEN

SOUTH BRANCH

FISHWEIR CREEK

WAS MEASURED

Figure 5. Comparison of daily mean streamflow for Ortega River near Jacksonville for the period of record, 

January 1, 1965, to September 30, 2002; January 1, 2000, to September 30, 2002; and daily mean 

streamflows for days on which measurements were made at Fishing Creek at 110th Street and South Branch 

Big Fishweir Creek at Blanding Boulevard.
Evaluation of Water Quality and Potential Effects of Septic Tank Effluent 13

EVALUATION OF WATER QUALITY AND 

POTENTIAL EFFECTS OF SEPTIC TANK 

EFFLUENT

The State of Florida developed a surface-water 

quality standards system, which includes classification, criteria, anti-degradation policy, and special protection of certain waters (Florida Department of 

Environmental Protection, 2002). According to the 

State of Florida, the streams in this study are classified 

as Class III surface waters: used for recreation and 

propagation and maintenance of a healthy, well-balanced population of fish and wildlife.

Although the water-quality data generally represent the full range of hydrologic conditions previously 

described, a majority of the samples were taken at sites 

during periods of low flow, less than 2.5 ft3

/s. Samples 

collected during low-flow periods represent surface 

water-quality conditions resulting from ground-water 

seepage (primarily septic effluent and upward movement of ground water from the surficial aquifer system). Samples collected during storm events represent 

water-quality conditions associated with surface runoff 

and shallow sub-surface flow of water to the stream. 

The surface runoff component of streamflow introduces variability in water-quality constituent concentrations observed and may dilute constituent 

concentrations due to the volume of water discharging 

to the stream. Constituent concentrations contributed 

to the stream water during storm events may overwhelm 

contributions from septic tanks, even though shallow 

sub-surface flow could “wash” constituents associated 

with septic tank effluent from the soil matrix.

The Nationwide Urban Runoff Project (NURP) 

investigated variability in constituent concentrations 

for urbanized basins (Novotny and Olem, 1994, 

p. 491-493). The investigation involved collecting 

intensive storm-runoff water-quality samples from 

28 cities across the United States. Analysis of the data 

from that study indicated that land-use effects are 

eclipsed by the storm-to-storm variability, and therefore, land use is of little use to predict urban runoff 

quality or to explain site-to-site differences. Because 

the sample sets collected for this study are relatively 

small and contain samples collected during storm-runoff events, it is reasonable to assume that differences 

in water quality between basins will be difficult to 

detect given the results of the NURP. If more samples 

had been collected and analyzed for low-flow events 

only, then the results likely could determine differences in water quality of stream water between study 

basins based on land-use type (suburban high density 

versus suburban low density). There were not enough 

samples collected for this study, however, to perform 

individual comparisons and analysis for sample sets 

representing the ground-water and storm-flow 

components of the streamflow.

The water-quality standards system for Class III 

surface waters state that nutrients (total nitrogen and 

total phosphorus) shall be limited as needed to prevent 

violations of other standards, that man-induced nutrient 

enrichment shall be considered degradation, and that 

nutrient concentrations of a water body shall not be 

altered so as to cause an imbalance in the natural populations of aquatic flora and fauna (Florida Department of 

Environmental Protection, 2002). The U.S. Environmental Protection Agency (2000) lists nutrient criteria for 

rivers and streams in Ecoregion XII, which encompasses 

the study areas, as 0.90 milligrams per liter (mg/L) for 

total nitrogen and 0.04 mg/L for total phosphorus.

Waste from warm blooded animals contributes 

a variety of intestinal bacteria that can be pathogenic 

to humans; body contact with water that contains 

pathogens can result in several types of diseases in 

humans. The State of Florida fecal coliform bacteria 

standard for Class III surface waters is 800 colonies 

Table 5. Rainfall summary for selected sites in Jacksonville, Florida

[Map number shown in figure 1]

Map

number

Site name and

identification number

Annual rainfall total, 

inches

Average 

annual rainfall, 

inches

2000 2001 2002 (period of record)

1 Jacksonville International Airport

(084358)

39.77 49.14 54.74 52.9

 (1931-2000)

2 Naval Air Station Jacksonville

(722065)

40.64 51.57 46.96 47.5

 (1945-1998)
14 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

per 100 milliliters of water on any 1 day (Florida 

Department of Environmental Protection, 2002). 

Sources of bacteria can be from municipal wastewater 

discharges, leachate from domestic septic tank 

systems, runoff or ground-water seepage from livestock producing areas (pasture and feedlots), areas 

where manure is applied as fertilizer, or from wildlife 

populations. Septic tanks are designed to reduce or 

eliminate most human health or environmental threats 

posed by pollutants in wastewater. Properly functioning septic tank systems result in retention and die-off 

of most pathogenic bacteria (U.S. Environmental 

Protection Agency, 2002b). Therefore, the presence of 

these organisms in surface water indicates fecal contamination and may also indicate the presence of 

pathogenic organisms.

The most widely used indicator bacteria are 

total coliform, fecal coliform, enterococci and fecal 

streptococci groups, and Escherichia coli (U.S. Environmental Protection Agency, 2002a). The city of 

Jacksonville maintains a monitoring network throughout Duval County, and collects samples that are analyzed for fecal coliform bacteria (Deuerling and 

Cooner, 1995). To maintain uniformity in data collection practices throughout the County and to evaluate 

the water-quality conditions of the stream water, fecal 

coliform bacteria were sampled and analyzed as part 

of this study.

Antibiotic use by animals and humans results in 

patterns of antibiotic resistance in fecal coliform 

bacteria that reflect to some extent the exposure of 

fecal coliform bacteria to antibiotics (Harwood and 

others, 2000). The analysis used for this study is based 

on the assumption that fecal coliform bacteria from 

human sources will have a different resistance to 

selected antibiotics than those from different animal 

sources (Simpson and others, 2002). The antibiotic 

resistance patterns of fecal coliform bacteria were used 

to identify the sources of fecal coliform bacteria. 

Determination of the source of fecal material would 

indicate whether human waste (septic tank effluent) is 

impacting the quality of the stream water.

Major Ions

Major ion concentrations can be used to compare surface-water and shallow ground-water characteristics and some can also be used as indicators of the 

effects of septic tank effluent. Pitt and others (1975) 

classified certain constituents as naturally occurring in 

ground water or associated with septic tank effluent, 

and summarized the chemical characteristics of shallow ground water in areas influenced by septic tanks in 

Dade County, Florida. Phelps (1994) summarized 

chemical characteristics of water from the surficial 

aquifer system in Duval County. A comparison of data 

from this study and those summarized by Pitt and 

others (1975) and Phelps (1994) is given in table 6.

Table 6. Summary of major ion constituents from surface-water samples for Fishing Creek and South Branch Big Fishweir 

Creek, Duval County, Florida, 2000-02; the surficial aquifer system in Duval County,1970-89; and selected surficial aquifer 

wells in areas serviced by septic tanks, Dade County, Florida, 1970-73

[All concentrations are dissolved and given in milligrams per liter, except where noted. μS/cm, microsiemens per centimeter at 25 degrees Celsius; 

μg/L, micrograms per liter]

Constituent

Study basinsa, 

2000-02

a

Samples collected for this study.

Duval Countyb, 

1970-89

b

Phelps, 1994, table 3.

Septic tank influencedc, 

1970-73

c

Pitt, 1975, tables 5 and 6.

Mean Range of values Mean Range of values Mean Range of values

calcium 54 16.- 84 120 51.- 180 89 30.- 120

chloride 28 5.4 - 72 16 3.- 100 28 2.0 - 50

iron, μg/L 231 24.- 811 1,510 10.- 12,000 1,910 .7 - 36,000

magnesium 7.3 2.1 - 12 4.2 1.6 - 13 3.2 .9 - 8.0

pH, standard units 7.1 6.2 - 7.7 5.8 3.8 - 8.1 7.7d 6.8 - 8.5

potassium 3.3 1.7 - 5.1 .8 .4 - 1.0 3.1 .2 - 5.7

sodium 19 4.2 - 50 9.5 6.4 - 14 19 2.6 - 35

specific conductance, μS/cm 409 63.- 902 218 31.- 960 541 182.- 694

sulfate 40 3.9 - 83 12 .2 - 87 26 0.0 - 42

dMedian pH value.
Evaluation of Water Quality and Potential Effects of Septic Tank Effluent 15

The specific conductance of water is a simple, 

useful measure of the presence of dissolved ions. 

Specific conductance values observed at study sites 

generally are comparable to specific conductance 

values observed in shallow ground water throughout 

Duval County (table 6). Dissolved calcium and magnesium, dissolution products of native rock, also indicate the influence of shallow ground water on the 

water chemistry of stream water. Sodium, potassium, 

chloride, and sulfate are naturally present in water, but 

also can be useful indicators of septic tank effluent 

(Pitt and others, 1975). The maximum dissolved potassium and sodium concentrations exceed background 

data for Duval County and are similar to those 

observed in Dade County at sites influenced by septic 

tank effluent.

Sodium is a conservative constituent that tends 

to remain in solution, and is introduced to septic tanks 

from grey and black water sources. Given the conservative nature of sodium, effluent from septic tanks 

likely will discharge elevated levels of sodium. Water 

samples for the Fishing Creek basin indicated sodium 

concentrations increased from upstream to downstream, and concentrations of sodium were greater in 

South Branch Big Fishweir Creek than in Fishing 

Creek (fig. 6). Increases in sodium concentrations 

from upstream to downstream in the Fishing Creek 

basin likely are due to the accumulation of septic tank 

effluent containing sodium as stream water moves 

downstream. The greater concentration of sodium in 

the South Branch Big Fishweir Creek basin likely is 

the result of higher septic tank densities and leaky 

infrastructure or improperly functioning septic tank 

systems upstream from the study area. The fact that 

sodium concentrations did not increase from upstream 

to downstream in the South Branch Big Fishweir Creek 

basin indicate that the stream may be at carrying capacity for constituents upstream from the South Branch 

Big Fishweir Creek at Cassat Avenue. Therefore, further addition of constituents within the study area will 

not affect constituent concentrations. Based on analysis 

of major ion samples, water-quality characteristics of 

the stream water in the study basins indicate influence 

from ground-water sources and septic tank activity.

Trace constituent data generally were not useful 

in evaluating effects of septic tank effluent. Water 

samples analyzed for boron and manganese had concentrations ranging from 20 to 99 micrograms per liter 

(μg/L) and 2.1 to 12 μg/L, respectively. Fifteen water 

samples from the Upper Floridan aquifer (Phelps, 

2001) had boron concentrations ranging from 19 to 

49 μg/L and manganese concentrations ranging from 

0.3 to 10 μg/L. The higher range of boron concentrations observed in the present study might be indicative 

of the influence of septic tanks in the study basins, 

because boron is a constituent in household products.

x

x

5787

FISHING CREEK SOUTH BRANCH

BIG FISHWEIR CREEK

Note: Boxes with same

colors are not significantly

different.

30 number of values

EXPLANATION

SCHEMATIC BOXPLOT

x

x

x

x

x

x

o

o

o

ooo

75th percentile

median

25th percentile

lower outside

lower detached

upper detached

upper outside

DISSOLVED SODIUM CONCENTRATION,

IN MILLIGRAMS PER LITER

60

50

40

30

20

10

0 Wesconnet Blvd. 110th St. Cassat Ave. Blanding Blvd.

Figure 6. Concentrations of dissolved sodium at data collection sites, Jacksonville, Florida (site numbers 

refer to table 1).
16 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

Nutrients

The basic forms of nitrogen in water are nitrite, 

nitrate, ammonia, and organic nitrogen. Greater than 

50 percent of samples analyzed for nitrite nitrogen 

had concentrations less than the laboratory reporting 

limit (0.01 mg/L); values ranged from less than the 

laboratory reporting limit to 0.07 mg/L. Concentrations for nitrate nitrogen and ammonia nitrogen ranged 

from less than laboratory reporting limit (0.02 and 

0.01 mg/L, respectively) to 1.1 and 1.7 mg/L, respectively. Organic nitrogen concentrations were calculated by subtracting ammonia nitrogen concentrations 

from the ammonia-plus-organic nitrogen concentrations. Stream-water samples generally contained 

greater amounts of organic nitrogen than other nitrogen species (fig. 7). Organic nitrogen concentrations 

ranged from 0.07 to 1.56 mg/L at study sites.

Dissolved nitrite-plus-nitrate nitrogen were 

combined with total ammonia-plus-organic nitrogen to 

obtain an estimate of the total nitrogen concentration 

observed at study sites; total phosphorus was reported 

by the laboratory (table 7). Total nitrogen concentrations given in this report are considered an underestimate of total nitrogen because inorganic nitrogen 

sorbed to suspended sediment is not accounted for in 

the analysis of dissolved nitrite-plus-nitrate nitrogen. 

Water samples collected had estimated total nitrogen 

concentrations ranging from 0.33 to 2.86 mg/L and 

total phosphorus concentrations ranging from less than 

laboratory reporting limit (0.02 mg/L) to 0.64 mg/L. 

Concentrations of total nitrogen and total phosphorus 

in water sampled at study sites (Ecoregion XII) 

exceeded the U.S. Environmental Protection Agency 

(2000) nutrient criteria for rivers and streams 49 and 

96 percent of the time, respectively.

The number of samples collected at sites was 

relatively small (less than 15), which makes statistical 

comparisons between sites of relatively limited use. 

Plots of total nitrogen (fig. 8) and total phosphorus 

(fig. 9) indicate that samples were not normally 

distributed at sites and had varied distributions. Visual 

comparison of the sample populations shows a difference from upstream to downstream and between 

Fishing Creek and South Branch Big Fishweir Creek 

basins. A comparison test was performed to determine 

whether sample sets of total nitrogen and total 

phosphorus have the same mean value. The statistical 

comparison indicated an upstream to downstream 

difference for total nitrogen in the South Branch Big 

Fishweir Creek basin (fig. 8) and a difference in mean 

concentration between the Fishing Creek and South 

Branch Big Fishweir Creek basins for total 

phosphorus (fig. 9).

NITRITE NITRATE AMMONIA ORGANIC

NITROGEN

CONCENTRATION, IN MILLIGRAMS PER LITER

51

51

51

x

o

o

x

x

x

x

o

o

51

x

o

2

1.5

1

0.5

0

13 number of values

EXPLANATION

SCHEMATIC BOXPLOT

x

x

x

x

x

x

o

o

o

ooo

75th percentile

median

25th percentile

lower outside

lower detached

upper detached

upper outside

Figure 7. Concentrations of nitrogen species at data collection sites, Jacksonville, Florida.
Evaluation of Water Quality and Potential Effects of Septic Tank Effluent 17

Table 7. Summary of nitrogen and phosphorus concentrations for surface-water samples, Jacksonville, Florida

[USGS, U.S. Geological Survey; constituent concentration values are in milligrams per liter; <, less than. Map numbers shown in figures 2 

and 3]

Map 

number

Site name 

and

USGS identification number

Number 

of 

samples

Total nitrogen Total phosphorus

Mean Median

Range 

of

values

Mean Median

Range 

of

values

4 Fishing Creek at Wesconnet 

Boulevard

(02246435)

11 1.00 .82 .55 - 1.64 .08 .07 .04 - .19

5 Fishing Creek at 110th Street 

(0226437)

13 1.00 1.05 .53 - 1.73 .07 .06 <.02 - .18

6 South Branch Big Fishweir 

Creek at Casssat Avenue 

(02246465)

14 .86 .69 .33 - 2.86 .11 .08 .07 - .64

7 South Branch Big Fishweir 

Creek at Blanding Boulevard 

 (02246467)

13 1.26 1.30 .45 - 2.00 .13 .12 .08 - .53

11

13

14

o

13

FISHING CREEK SOUTH BRANCH

BIG FISHWEIR CREEK

TOTAL NITROGEN CONCENTRATION,

IN MILLIGRAMS PER LITER

3.5

3.0

2.0

1.5

0.5

0.0

1.0

2.5

SITES

Wesconnet Blvd. 110th St. Cassat Ave. Blanding Blvd.

11 number of values

EXPLANATION

SCHEMATIC BOXPLOT

x

x

x

x

x

x

o

o

o

ooo

75th percentile

median

25th percentile

lower outside

lower detached

upper detached

upper outside

Note: Boxes with same

colors are not significantly

different.

Figure 8. Concentrations of total nitrogen at data collection sites, Jacksonville, Florida (site names refer to 

table 1).
18 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

The potential effects of septic tanks on streamwater quality can be evaluated by comparing constituent contributions to septic tanks, removal efficiencies, 

and constituent concentrations observed in streamwater samples. Wastewater discharges to septic tanks 

were studied by the U.S. Environmental Protection 

Agency (U.S. Environmental Protection Agency, 

2002b) and the State of Florida (Florida Executive 

Office of the Governor, 1999). These studies reported 

characterizations of septic tank effluent, and gave the 

average daily constituent concentrations contributed 

directly to septic tanks for total nitrogen and total 

phosphorus as ranging from 26 to 75 and 6 to 12 mg/L, 

respectively (U.S. Environmental Protection Agency, 

2002b). Sikora and Corey (1976) list the potential 

removal efficiency of septic tank systems for total 

nitrogen and total phosphorus as 10 to 40 percent and 

85 to 95 percent, respectively. These removal efficiencies are based on observations of ground water exiting 

the septic tank drain field.

Based on constituent contributions to septic 

tanks, removal efficiencies, and constituent concentrations observed in stream-water samples, removal efficiency for both total nitrogen and total phosphorus are 

greater than 90 percent. Water samples collected for 

x

x

x

o

11

13

14

13

11 number of values

EXPLANATION

SCHEMATIC BOXPLOT

x

x

x

x

x

x

o

o

o

ooo

75th percentile

median

25th percentile

lower outside

lower detached

upper detached

upper outside

Note: Boxes with same

colors are not significantly

different.

TOTAL PHOSPHORUS CONCENTRATION,

IN MILLIGRAMS PER LITER

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

FISHING CREEK SOUTH BRANCH

BIG FISHWEIR CREEK

SITES

Wesconnet Blvd. 110th St. Cassat Ave. Blanding Blvd.

Figure 9. Concentrations of total phosphorus at data collection sites, Jacksonville, Florida (site names refer to 

table 1).

this study were taken at a great distance (hundreds of 

feet) from individual septic tanks. These samples 

reflect potential input from other sources, such as 

fertilizer application, and changes in nitrogen and 

phosphorus as a result of adsorption and microbially 

mediated transformation. Based on calculations of 

removal efficiency, septic tank systems in the study 

basins were functioning properly at times and for 

hydrologic conditions when samples were collected. 

However, the hydrology of the study areas (shallow 

surficial aquifer system, fine-grained upland soils, and 

little topographic relief) and construction methods of 

individual septic systems affect the operation and 

efficiency of septic tank systems in the study areas, 

and therefore, affect stream-water quality.

Wastewater Constituents

Chemical analysis of stream-water samples 

for compounds commonly found in wastewater was 

used to evaluate the impact of sanitary sewer or septic 

tank outflow on the water quality of study streams. 

Organic wastewater compounds detected above the 

minimum laboratory-reporting level are listed in table 8.
Evaluation of Water Quality and Potential Effects of Septic Tank Effluent 19

Compounds detected were detergents, antioxidants 

and flame retardants, manufactured polycarbonate resins, industrial solvents, and mosquito repellent. The 

most commonly detected compound was para-nonylphenol, which is a detergent metabolite; it was 

detected in both the Fishing Creek and South Branch 

Big Fishweir Creek basins. The likely source of paranonylphenol is wastewater from washing machines 

and dishwashing detergents discharged to septic tanks. 

Another compound detected in both basins was N,Ndiethyl-meta-toluamide (Deet). The source of this 

compound likely is wastewater produced by residents 

bathing or washing clothing after using personal insecticides containing Deet or runoff of overspray. Another 

compound detected in the Fishing Creek basin was 

bisphenol-A; this compound is used primarily to make 

polycarbonate plastic and epoxy resins. Samples for 

the South Branch Big Fishweir Creek basin had a 

greater number of compounds (table 8) detected than 

did samples from the Fishing Creek basin. The South 

Branch Big Fishweir Creek basin contains some small 

business development, which likely contributed to 

detections of compounds such as isophorone, an 

industrial solvent. Most of the compounds detected are 

commonly associated with grey water discharges to 

septic tanks in the study areas; therefore, their 

presence indicates that the Fishing Creek and South 

Branch Big Fishweir Creek basins are influenced by 

wastewater from septic tanks.

Bacteria

Fecal coliform bacteria concentrations were 

measured on a monthly basis; of 115 samples, 

63 percent exceeded the State of Florida fecal coliform 

bacteria standard for Class III surface waters of 

800 colonies per 100 milliliters of water on any 1 day. 

The results of individual water samples collected 

for fecal coliform bacteria analysis are given in 

appendix 3. Fecal coliform bacteria in water samples 

were reported as most probable number per 100 milliliters (mpn/100mL) of sample and ranged from less 

than 20 mpn/100mL at Fishing Creek at Wesconnet 

Boulevard to equal to or greater than 160,000 mpn/

100mL at South Branch Big Fishweir Creek at Blanding Boulevard (table 9). The median and geometric 

mean indicate that colony concentrations increase 

from upstream to downstream for the Fishing Creek 

basin, and that the South Branch Big Fishweir Creek 

basin has higher colony concentrations than those for 

the Fishing Creek basin.

Table 8. Concentrations of organic wastewater compounds above the minimum laboratory-reporting level, Jacksonville, 

Florida

[d, nonionic detergent metabolite; a, manufactured polycarbonate resins, antioxidant, flame retardant; i, insecticide, urban uses, mosquito repellent; 

p, plasticizer, flame retardant; c, beverages, diuretic; s, solvent for lacquer, plastic, oil, silicon, resin; m, cigarettes, cough drops, liniment, mouthwash; 

e, compound was detected but concentrations with low recovery, high variable recovery, unstable instrument response, or from technical mixture are 

not quantified; μg/L, micrograms per liter. Map numbers shown in figures 2 and 3]

Map 

number Site name Sample 

date Constituent name

Possible 

compound 

uses or 

sourcesa

Concentration 

(μg/L)

4 Fishing Creek at Wesconnett Boulevard 8/21/2001 para-Nonylphenol (total) d e

4 Fishing Creek at Wesconnett Boulevard 2/26/2002 Bisphenol A a 1.1

4 Fishing Creek at Wesconnett Boulevard 2/26/2002 para-Nonylphenol (total) d e

5 Fishing Creek at 110th Street 7/11/2000 N,N-diethyl-meta-toluamide (Deet) i 1.32

5 Fishing Creek at 110th Street 2/26/2002 Bisphenol A a 2.7

6 South Branch Big Fishweir Creek at Cassat Avenue 7/11/2000 tri(2-chloroethyl)phosphate p .88

6 South Branch Big Fishweir Creek at Cassat Avenue 8/21/2001 Caffeine c 2

6 South Branch Big Fishweir Creek at Cassat Avenue 8/21/2001 Isophorone s 12

6 South Branch Big Fishweir Creek at Cassat Avenue 8/21/2001 Menthol m .85

6 South Branch Big Fishweir Creek at Cassat Avenue 8/21/2001 N,N-diethyl-meta-toluamide (Deet) i .81

6 South Branch Big Fishweir Creek at Cassat Avenue 8/21/2001 para-Nonylphenol (total) d e

7 South Branch Big Fishweir Creek at Blanding Boulevard 8/22/2001 Isophorone s 3.1

7 South Branch Big Fishweir Creek at Blanding Boulevard 8/22/2001 para-Nonylphenol (total) d e

7 South Branch Big Fishweir Creek at Blanding Boulevard 2/26/2002 para-Nonylphenol (total) d e

a

Zaugg, 2002, table 1.
20 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

Fecal coliform bacteria concentrations were 

significantly higher in the South Branch Big Fishweir 

Creek basin than in the Fishing Creek basin (fig. 10). 

This likely is the result of the higher density of septic 

tanks per acre in the South Branch Big Fishweir Creek 

basin. Fecal coliform bacteria concentrations also 

were significantly greater at the downstream site on 

Fishing Creek compared to the upstream site. 

Increases in bacteria concentrations from upstream to 

downstream in the Fishing Creek basin likely are due 

to the accumulation of septic tank effluent as stream 

water moves downstream. There was no significant 

difference in the fecal coliform bacteria concentrations 

between the two South Branch Big Fishweir Creek 

sites. This likely is due to the varaiation in housing and 

septic tank density in the Fishing Creek basin and 

higher colony concentrations observed in the South 

Branch Big Fishweir Creek basin, which make it more 

difficult to observe significant differences in the 

sample population mean given a similar increase in 

colony concentrations from upstream to downstream. 

The lack of significant difference between upstream 

and downstream bacteria concentrations may also be 

an indication that the South Branch Big Fishweir 

Creek basin is at carrying capacity and addition of 

septic tank effluent to the stream will not affect bacteria populations. Overall, fecal coliform bacteria 

concentrations exceeded the State of Florida Class III 

surface-water standards and reflect the impact of 

septic tank effluent on the quality of stream water.

Water samples analyzed for antibiotic resistance 

patterns of fecal coliform bacteria were used to evaluate the potential impact of human activity on the 

quality of stream water. A total of 16 samples was 

collected, and fecal coliform bacteria isolates were 

classified into five source catagories for each sample; 

chicken, cow, dog, human, and wildlife. Fecal 

coliform bacteria were detected and classified at 

significant levels (greater than 20 percent) for 23 of 

the 80 potential classifications (1 chicken, 3 dog, 

14 human, and 5 wildlife). Individual sample results 

(app. 4) were combined for each of the study sites to 

obtain an average likelihood of potential sources for 

the entire study period (table 10). Significant sources 

of fecal coliform bacteria isolates over the study 

period as determined by the antibiotic resistance 

analysis were wild animals and humans. A majority of 

the fecal coliform bacteria were classified to be from 

human sources; these were detected at a significant 

level for all study sites in both the Fishing Creek and 

South Branch Big Fishweir Creek basins. Fecal 

coliform bacteria classified as from wild animals were 

detected at significant levels at Fishing Creek at 110th

Street. Detections of fecal coliform bacteria isolates 

from wild animal sources for Fishing Creek at 110th

Street occurred during and following installation of 

the sanitary sewer system infrastructure in the basin. 

Samples collected at this site indicated a change in 

known source classification from human to a mix 

of human and wild animal and later dog and wild 

animal over the study period (app. 4). The change 

in classification of known sources likely occurred 

due to drainage changes made in the stream and other 

parts of the basin during construction and connection 

of residences to the sanitary sewer system following 

its completion in November 2002 (Dana Morton, city 

of Jacksonville, Division of Air and Water Quality, 

oral commun., 2003). Results of the fecal coliform 

bacteria antibiotic resistance analysis indicate that 

movement of septic tank effluent through the soil 

matrix and discharged to the stream contributes to 

fecal coliform bacteria populations observed in the 

stream water. Because the primary source of fecal 

coliform bacteria is from human sources, most likely 

septic tank effluent, management of human sources 

may substationally improve microbiological water 

quality in both the Fishing Creek and South Branch 

Big Fishweir Creek basins.

Table 9. Fecal coliform bacteria summary for surface-water samples, Jacksonville, Florida

[USGS, U.S. Geological Survey; <, less than; fecal coliform bacteria values are reported as most probable number per 100 milliliters. Map numbers 

shown in figures 2 and 3]

Map 

number

Site name and

USGS identification number

Number 

of 

samples

Maximum Minimum Median Geometric 

mean

4 Fishing Creek at Wesconnet Boulevard 

(02246435)

25 50,000 <20 70 138

5 Fishing Creek at 110th Street

(0226437)

28 50,000 20 900 926

6 South Branch Big Fishweir Creek at Casssat Avenue 

(02246465)

31 160,000 40 5,000 3,720

7 South Branch Big Fishweir Creek at Blanding Boulevard 

 (02246467)

31 ≥160,000 800 6,000 7,040
Evaluation of Water Quality and Potential Effects of Septic Tank Effluent 21

24 27

30 30

x x

x

FECAL COLIFORM BACTERIA,

MOST PROBABLE NUMBER

PER 100 MILLILITERS

1,000,000

100,000

10,000

1,000

100

10

FISHING CREEK SOUTH BRANCH

BIG FISHWEIR CREEK

SITES

Wesconnet Blvd. 110th St. Cassat Ave. Blanding Blvd.

Note: Boxes with same

colors are not significantly

different.

30 number of values

EXPLANATION

SCHEMATIC BOXPLOT

x

x

x

x

x

x

o

o

o

ooo

75th percentile

median

25th percentile

lower outside

lower detached

upper detached

upper outside

Figure 10. Concentrations of fecal coliform bacteria at data collection sites, Jacksonville, Florida (site names 

refer to table 1).

Table 10. Summary of discriminant analysis of antibiotic resistance patterns used to classify fecal coliform bacteria 

from known sources into source categories for surface-water samples, Jacksonville, Florida

[USGS, U.S. Geological Survey; map numbers shown in figures 2 and 3. Percentages may not equal 100 percent due to rounding]

Map 

number

Site name and

USGS identification number

Classifications of fecal coliform bacteria isolates

Total

count 

(percent)

Chicken

count 

(percent)

Cow

count 

(percent)

Dog

count 

(percent)

Human

count 

(percent)

Wild

count 

(percent)

4 Fishing Creek at Wesconnet 

Boulevard

(02246435)

6 (3.2) 1 (.5) 17 (9.1) 126 (67.4) 37 (19.8) 187 (100)

5 Fishing Creek at 110th Street

(0226437)

3 (2.3) 4 (3.1) 18 (13.7) 62 (47.3) 44 (33.6) 131 (100)

6 South Branch Big Fishweir Creek

at Casssat Avenue 

(02246465)

12 (6.7) 1 (.6) 10 (5.6) 145 (80.6) 12 (6.7) 180 (100)

7 South Branch Big Fishweir Creek

at Blanding Boulevard 

 (02246467)

11 (5.7) 0 (.0) 34 (17.6) 131 (67.9) 17 (8.8) 193 (100)
22 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

SUMMARY

Tributary streamflow to the St. Johns River in 

Duval County is thought to be affected by septic tank 

leachate from residential areas adjacent to these tributaries. Water managers and the city of Jacksonville 

have committed to infrastructure improvements as part 

of a management plan to address the impairment of 

tributary water quality. Major ion, nutrient, and fecal 

coliform concentrations, detection of wastewater compounds, and tracking of bacterial sources were used to 

document septic tank influences on the water quality 

of selected tributaries in order to provide data to evaluate the effects of future remedial activities in selected 

tributaries.

The tributaries of Fishing Creek and South Big 

Fishweir Creek were selected because they coincide 

with subdivisions identified as high-priority locations 

for septic tank phase-out projects: the Pernecia and 

Murray Hill B subdivisions, respectively. The data collection networks consisted of two sites in each study 

basin located at points upstream and downstream from 

areas where septic tanks are to be replaced by a sanitary sewer system. These sites provided information 

on the hydrologic and water-quality characteristics of 

the study basins over the study period, April 1999 to 

September 2002.

The Fishing Creek basin is west of the St. Johns 

River and joins the Ortega River south (upstream) of 

its confluence with the Cedar River. The Big Fishweir 

Creek basin is west of the St. Johns River and joins the 

Ortega River at its confluence with the St. Johns River. 

Both creeks are relatively narrow, 25 feet or less in 

width, with definitive banks that are 3-6 feet high, 

especially in the lower reaches of the basin. The 

Pernecia subdivision covers an area of about 

193 acres, of which 156 acres drain to Fishing Creek; 

the Murray Hill B subdivision is about 465 acres, of 

which 154 acres drain to South Branch Big Fishweir 

Creek. Population, housing (number of residences), 

and septic tank densities for the Fishing Creek and 

South Branch Big Fishweir Creek basins are 2.7 and 

6.0 people per acre, 1.3 and 2.3 houses per acre, and 

1.3 and 2.7 septic tanks per acre, respectively.

Measured streamflows ranged from 107 cubic 

feet per second (ft3

/s) at Fishing Creek at 110th Street 

to 0.02 ft3

/s at the South Branch Big Fishweir Creek at 

Cassat Avenue. Streamflows for Fishing Creek tend to 

be greater than those for South Branch Big Fishweir 

Creek, and streamflow increases from upstream to 

downstream in both basins. Based on calculations 

from periodic measurements of streamflow, the runoff 

per unit area is greater in the Fishing Creek basin than 

in the South Branch Big Fishweir Creek basin.

Water samples analyzed for major ions and 

nutrients were collected in conjunction with discharge 

measurements. A majority of the samples collected 

were during periods of low flow, less than 2.5 ft3/s, 

and generally represent base-flow conditions. Analysis 

of major ion samples indicates influence from groundwater sources and septic tank activity. The maximum 

levels for dissolved potassium and sodium exceed 

those elsewhere in Duval County and are similar to 

those in Dade County at sites influenced by septic tank 

effluent.

Stream-water samples generally contained 

greater amounts of organic nitrogen than other nitrogen species, and concentrations ranged from 0.07 to 

1.56 milligrams per liter (mg/l). Concentrations of 

total nitrogen ranged from 0.33 to 2.86 mg/L, and concentrations for total phosphorus ranged from less than 

laboratory reporting limit (0.02 mg/l) to 0.64 mg/l. 

Concentrations of total nitrogen and total phosphorus 

sampled at study sites exceeded the U.S. Environmental Protection Agency Ecoregion XII nutrient criteria 

for rivers and streams 49 and 96 percent of the time, 

respectively.

Wastewater compounds detected at study sites 

were categorized as detergents, antioxidants and flame 

retardants, manufactured polycarbonate resins, industrial solvents, and mosquito repellent. The South 

Branch Big Fishweir Creek basin had a greater number of compounds detected than the Fishing Creek 

basin. The most common compound detected was 

para-nonylphenol, which is a breakdown product of 

detergent. It was detected in both the Fishing Creek 

and South Branch Big Fishweir Creek study basins. 

Results of wastewater sampling indicate the presence 

of septic tank leachate in stream water.

Fecal coliform bacteria concentrations were 

measured on a monthly basis; of 115 samples, 

63 percent exceeded the State of Florida fecal coliform 

bacteria standard for Class III surface waters of 

800 colonies per 100 milliliters of water on any 1 day. 

Fecal coliform bacteria concentrations ranged from 

less than than 20 most probable number per 100 milliliters (mpn/100mL) of sample at Fishing Creek at 

Wesconnet Boulevard to equal to or greater than 
References 23

160,000 mpn/100mL at South Branch Big Fishweir 

Creek at Blanding Boulevard. Fecal coliform bacteria 

concentrations were significantly higher in the South 

Branch Big Fishweir Creek basin than in the Fishing 

Creek basin during the study. Antibiotic resistance 

patterns of fecal coliform bacteria were used to 

identify the sources of fecal coliform bacteria. 

Significant sources of fecal coliform bacteria included 

wild animals, dogs, and humans. A majority of the 

fecal coliform bacteria were classified to be from 

human sources. Because the primary source of fecal 

coliform bacteria is from human sources, most likely 

septic tank effluent, management of human sources 

may substationally improve microbiological water 

quality in both the Fishing Creek and South Branch 

Big Fishweir Creek basins.

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———2001, Geochemistry and origins of mineralized 

waters in the Floridan aquifer system, northeastern 

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Investigations Report 01-4112, 64 p.

Pitt, W.A.J., Jr., Mattraw, H.C., Jr., and Klein, Howard, 

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discharge, U.S. Geological Survey Water-Supply Paper 

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Sikora, L.J., and Corey, R.B., 1976, Fate of nitrogen and 

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36, no. 24, p. 5279-5288.

U.S. Department of Agriculture, Natural Resource 

Conservation Service, 1998, Soil survey of City of 

Jacksonville, Duval County, Florida, 218 p.
24 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

U.S. Environmental Protection Agency, 2000, Office of 

Water, ambient water quality criteria 

recommendations, information supporting the 

development of state and tribal nutrient criteria: Rivers 

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Environmental Protection Agency EPA 822-B-00-021 

December 2000 [cited October 18, 2002] http://

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ecoregions/rivers/rivers_12.pdf.

———2002a, Office of Water, Implementation guidance 

for ambient water quality criteria for bacteria: U.S. 

Environmental Protection Agency EPA-823-B-02-003 

June 2002 [cited September 2, 2003] http://

www.epa.gov/ost/standards/bacteria/bacteria.pdf.

———2002b, Office of Water, Office of Research and 

Development, Onsite wastewater treatment systems 

manual: U.S. Environmental Protection Agency EPA/

625/R-00/008 February 2002 [cited February 2, 2003] 

http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/

625R00008.htm.

———2003, Inductively coupled plasma—Atomic emission spectrometric method for trace element analysis 

of water and waste method 200.7: U.S. Code of Federal Regulations, Title 40, Part 136, Appendix C [cited 

April 25, 2003] http://www.access.gpo.gov/nara/cfr/

cfrhtml_00/Title_40/40cfr136_00.html.

U.S. Geological Survey, 2003, Water resources data, 

Florida, water year 2002, v. 1A, northeast Florida 

surface water: U.S. Geological Survey Water-Data 

Report, FL-02-1A, 401 p.

Wiggins, Bruce A., Andrews, R.W., Conway, R.A., Corr, 

C.L., Dobratz, E.J., Dougherty, D.P., Eppard, J.R., 

Knupp, S.R., Limjoco, M.C., Mettenburg, J.M., 

Rinehardt, J.M., Sonsino, J., Torrijos, R.L., and 

Zimmerman, M.E., 2003, Use of antibiotic resistance 

analysis for representativeness testing of 

multiwatershed libraries: Applied and Environmental 

Microbiology, v. 69, no. 6, p. 3399-3405.

Wilde, F.D., and others, eds., 1998, National field manual 

for the collection of water-quality data: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9 [variously paged].

Zaugg, S.D., Smith, S.G., Schoeder, M.P., Barber, L.B., and 

Burkhardt, M.R., 2002, Methods of analysis by the 

U.S. Geological Survey National Water Quality 

Laboratory—Determination of wastewater compounds 

by polystyrene-divinylbenzene solid-phase extraction 

and capillary-column gas chromatography/mass 

spectrometry: U.S. Geological Survey WaterResources Investigations Report 01-4186, 37 p.
Appendix 1 25

Appendix 1. Constituents analyzed as part of major 

ion and nutrient sampling

[mg/L; milligrams per liter]

Constituent name

Method 

reporting limit 

(mg/L)

acid neutralizing capacity 1

boron .002

calcium .02

chloride .1

fluoride .1

iron .002

magnesium .03

manganese .001

nitrogen, ammonia, dissolved .01

nitrogen, ammonia plus organic nitrogen, 

total

.2

nitrogen, nitrite, dissolved .01

nitrogen, nitrite plus nitrate, dissolved .02

pH .1a

a

standard units

phosphorus, dissolved .02

phosphorus, total .02

phosphorus, phosphate, ortho, dissolved .018

potassium .1

silica .01

sodium .1

specific conductance 1.b

bmicroSiemens per centimeter at 25 degrees Celsius

sulfate .2
26 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

Appendix 2. Constituents analyzed as part of the U.S. Geological Survey National Water-Quality Laboratory organic 

wastewater sample series

[mg/L, micrograms per liter]

Constituent name

Method 

reporting limit 

(μg/L)

Constituent name

Method 

reporting limit 

(μg/L)

1-Methylnaphthalene .5 Fluoranthene .5

1,4-Dichlorobenzene .5 Hexadydrohexamethylcyclopentabenzopyran (HHCB).5

2,6-Dimethylnaphthalene .5 Indole .5

2-Methylnaphthalene .5 Isoborneol .5

3-beta-Coprostanol 2 Isophorone .5

3-Methyl-1(H)-indole (Skatole) 1 Isopropylbenzene .5

3-tert-Butyl-4-hydroxy anisole 

(BHA)

5 Isoquinoline .5

4-Cumylphenol 1 Menthol .5

4-n-Octylphenol 1 Metalaxyl .5

4-tert-Octylphenol 1 Methyl salicylate .5

5-Methyl-1H-benzotriazole 2 Metolachlor .5

Acetophenone .5 N,N-diethyl-meta-toluamide 

(DEET)

.5

Acetyl hexamethyl tetrahydronaphthalene (AHTN).5 Naphthalene .5

Anthracene .5 Nonylphenol, diethoxy- (total) 5

Anthraquinone .5 Octylphenol, diethoxy- 1

Benzo[a]pyrene .5 Octylphenol, monoethoxy- 1

Benzophenone .5 p-Cresol 1

beta-Sitosterol 2 para-Nonylphenol (total) 5

beta-Stigmastanol 2 Pentachlorophenol 2

Bisphenol A 1 Phenanthrene .5

Bromacil .5 Phenol .5

Bromoform .5 Prometon .5

Caffeine .5 Pyrene .5

Camphor .5 Tetrachloroethylene .5

Carbaryl 1 Tri(2-chloroethyl)phosphate .5

Carbazole .5 Tris(dichlorisopropyl)phosphate .5

Cholesterol 2 Tributyl phosphate .5

Chlorpyrifos .5 Triclosan 1

Cotinine 1 Triethyl citrate (ethyl citrate) .5

d-Limonene .5 Triphenyl phosphate .5

Diazinon .5 Tri(2-butoxyethyl)phosphate .5

Dichlorvos 1
Appendix 3 27

Appendix 3. Fecal coliform bacteria counts for surface-water samples

[Fecal coliform bacteria values are reported as most probable number per 100 milliliters; <, less than; >, greater than or equal]

Fishing Creek at 

Wesconnet Boulevard 

(02246435)

Fishing Creek at 

110th Street 

(02246437)

South Branch Big 

Fishweir Creek at 

Cassat Avenue 

(02246465)

South Branch Big 

Fishweir Creek at 

Blanding Boulevard 

(02246467)

Date Bacteria 

estimate Date Bacteria 

estimate Date Bacteria 

estimate Date Bacteria 

estimate

2/7/2000 270 2/7/2000 1,700 2/8/2000 3,000 2/8/2000 17,000

3/8/2000 70 3/8/2000 800 3/8/2000 1,700 3/8/2000 7,000

4/18/2000 20 4/18/2000 110 4/18/2000 5,000 4/18/2000 5,000

5/23/2000 <20 5/23/2000 3,000 5/23/2000 5,000 5/23/2000 1,700

8/8/2000 20 7/11/2000 800 6/12/2000 160,000 6/12/2000 160,000

9/5/2000 70 8/8/2000 20 7/11/2000 11,000 7/11/2000 30,000

9/18/2000 700 9/5/2000 1,400 8/8/2000 11,000 8/8/2000 16,000

10/10/2000 20 9/18/2000 140 9/6/2000 50,000 9/6/2000 90,000

11/28/2000 500 10/10/2000 330 10/10/2000 5,000 10/10/2000 50,000

12/12/2000 40 11/28/2000 270 11/28/2000 5,000 11/28/2000 >16,000

1/16/2001 500 12/12/2000 170 12/13/2000 9,000 12/13/2000 9,000

2/6/2001 300 1/16/2001 1,300 1/16/2001 5,000 1/16/2001 3,000

3/13/2001 500 2/6/2001 330 2/7/2001 3,000 2/7/2001 1,700

4/10/2001 40 3/13/2001 3,000 3/13/2001 1,100 3/13/2001 2,800

7/9/2001 500 4/10/2001 300 4/10/2001 1,300 4/10/2001 800

9/10/2001 110 6/6/2001 1,100 5/15/2001 40 5/15/2001 800

10/15/2001 220 7/9/2001 700 6/6/2001 1,300 6/6/2001 1,700

11/6/2001 40 9/10/2001 1,300 7/9/2001 3,500 7/9/2001 >16,000

12/10/2001 50,000 10/15/2001 2,200 9/10/2001 2,200 8/22/2001 2,400

1/15/2002 9,000 11/6/2001 5,000 10/15/2001 700 9/10/2001 9,000

2/26/2002 40 12/10/2001 50,000 11/7/2001 1,100 10/15/2001 2,200

3/26/2002 20 1/15/2002 17,000 12/10/2001 30,000 11/7/2001 1,700

4/9/2002 40 2/26/2002 1,700 1/15/2002 17,000 12/10/2001 90,000

7/9/2002 40 3/26/2002 700 2/26/2002 800 1/15/2002 22,000

9/25/2002 1,400 4/9/2002 3,000 3/26/2002 7,000 2/26/2002 800

7/9/2002 900 4/9/2002 500 3/26/2002 2,200

8/12/2002 500 5/7/2002 5,000 4/9/2002 2,400

9/25/2002 2,800 6/18/2002 16,000 5/7/2002 2,200

7/9/2002 1,300 6/18/2002 9,000

8/12/2002 5,000 7/9/2002 >160,000

9/25/2002 2,200 9/25/2002 50,000
28 Evaluation of Water Quality for Two St. Johns River Tributaries Receiving Septic Tank Effluent, Duval County, Florida

Appendix 4. Discriminant analysis of antibiotic resistance patterns used to classify fecal coliform bacteria from known 

sources into source categories for surface-water samples

[USGS, U.S. Geological Survey]

Site name and

USGS identification number

Categories Total

count

(percent)

Chicken count 

(percent)

Cow count 

(percent)

Dog count 

(percent)

Human count 

(percent)

Wild count 

(percent)

September 2001 sampling

Fishing Creek at Wesconnet Boulevard

(02246435)

3 (6) 1 (2) 5 (10) 40 (80) 1 (2) 50 (100)

Fishing Creek at 110th Street

(0226437)

1 (16.7) 0 (0) 0 (0) 5 (83.3) 0 (0) 6 (100)

South Branch Big Fishweir Creek

at Casssat Avenue 

(02246465)

0 (0) 1 (2.7) 1 (2.7) 35 (94.6) 0 (0) 37 (100)

South Branch Big Fishweir Creek

at Blanding Boulevard 

 (02246467)

0 (0) 0 (0) 0 (0) 51 (100) 0 (0) 51 (100)

Total 7 (3.7) 2 (1) 14 (7.3) 167 (87) 2 (1.04) 192 (100)

December 2001 sampling

Fishing Creek at Wesconnet Boulevard

(02246435)

1 (2.1) 0 (0) 1 (2.1) 46 (95.8) 0 (0) 48 (100)

Fishing Creek at 110th Street

(0226437)

2 (4.2) 4 (8.3) 2 (4.2) 40 (83.3) 0 (0) 48 (100)

South Branch Big Fishweir Creek

at Casssat Avenue 

(02246465)

4 (8.3) 0 (0) 6 (12.5) 38 (79.2) 0 (0) 48 (100)

South Branch Big Fishweir Creek

at Blanding Boulevard 

 (02246467)

1 (2.1) 0 (0) 6 (12.5) 41 (85.4) 0 (0) 48 (100)

Total 8 (4.2) 4 (2.1) 15 (7.8) 165 (85.9) 0 (0) 192 (100)

September 2002 sampling

Fishing Creek at Wesconnet Boulevard

(02246435)

1 (2.1) 0 (0) 0 (0) 37 (78.7) 9 (19.2) 47 (100)

Fishing Creek at 110th Street

(0226437)

0 (0) 0 (0) 2 (6.7) 15 (50) 13 (43.3) 30 (100)

South Branch Big Fishweir Creek

at Casssat Avenue 

(02246465)

8 (17) 0 (0) 0 (0) 38 (80.8) 1 (2.1) 47 (100)

South Branch Big Fishweir Creek

at Blanding Boulevard 

 (02246467)

10 (21.3) 0 (0) 21 (44.7) 12 (25.5) 4 (8.5) 47 (100)

Total 19 (11.1) 0 (0) 23 (13.4) 102 (59.6) 27 (15.8) 171 (100)

February 2003 sampling

Fishing Creek at Wesconnet Boulevard

(02246435)

1 (2.4) 0 (0) 11 (26.2) 3 (7.1) 27 (64.3) 42 (100)

Fishing Creek at 110th Street

(0226437)

0 (0) 0 (0) 14 (29.8) 2 (4.3) 31 (66) 47 (100)

South Branch Big Fishweir Creek

at Casssat Avenue 

(02246465)

0 (0) 0 (0) 3 (6.2) 34 (70.8) 11 (22.9) 48 (100)

South Branch Big Fishweir Creek

at Blanding Boulevard 

 (02246467)

0 (0) 0 (0) 7 (14.9) 27 (57.4) 13 (27.7) 47 (100)

Total 1 (0.5) 0 (0) 35 (19) 66 (35.9) 82 (44.6) 184 (100)