Water Quality of the Boca Raton Canal System

and Effects of the Hillsboro Canal Inflow,

Southeastern Florida, 1990-91

By DONALD J. McKENZIE

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 94-4128

Prepared in cooperation with the

City of Boca Raton

Tallahassee, Florida

1995
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

Any 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.

For additional information Copies of this report can be 

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Earth Science Information Center

Suite 3015 Open-File Reports Section

227 N. Bronough Street Box 25286, MS 517

Tallahassee, FL 32301 Denver Federal Center

Denver, CO 80225
Contents III

CONTENTS

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

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

Purpose and Scope .......................................................................................................................................................3

Water Supply and Canal System ..................................................................................................................................3

Surficial Aquifer System ..............................................................................................................................................5

Sampling Procedures and Analytical Methods ............................................................................................................5

Water Quality of the Boca Raton Canal System and Effects of Hillsboro Canal Inflow ...................................................5

Historical Water-Quality Data .....................................................................................................................................6

Major Inorganic Ions and Related Characteristics .......................................................................................................6

Nutrients .....................................................................................................................................................................10

Trace Elements ...........................................................................................................................................................11

Pesticides ....................................................................................................................................................................11

Summary and Conclusions ................................................................................................................................................12

Selected References ...........................................................................................................................................................13

FIGURES

1. Map showing location of the Boca Raton study area in Palm Beach County, southeastern Florida ..............................2

2. Map showing location of sampling sites, the general area of potable water-supply wells, and the average 

major-ion composition of water samples from the sampling sites in the Boca Raton canal system ..............................4

3. Graph showing annual average concentrations of dissolved solids at two sites in the Boca Raton canal system ..........7

4. Graph showing monthly average rainfall and month when canal water-quality sampling occurred, 1990-91 ...............8

5. Graph showing dissolved-solids concentrations for each water-quality sampling site, July 17, 1990, and

December 11, 1990 .......................................................................................................................................................10

TABLES

1. Summary of concentrations of total recoverable trace elements for four sampling sites in the Boca Raton

canal system, 1982-84 ....................................................................................................................................................7

2. Summary of concentrations of major inorganic ions and related characteristics, nutrients, and total

recoverable trace elements for all sampling sites in the Boca Raton canal system, July 1990 to

July 1991 .........................................................................................................................................................................9
IV Contents

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

Multiply By To obtain

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

square mile (mi2) 2.590 square kilometer

foot squared per day (ft2

/d) 0.09290 meter squared per day

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—

a geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, 

formerly called Sea Level Datum of 1929.

The standard unit for aquifer transmissivity is cubic foot per day per square foot times foot of aquifer thickness. 

This mathematical expression reduces to foot squared per day and is used in this report.

In this report, chemical concentration in water is expressed in milligrams per liter or micrograms per liter. 

Milligrams per liter is a unit expressing the concentration of chemical constituents in solution as weight 

(milligrams) of solute per unit volume (liter) of water; 1,000 micrograms per liter is equivalent to 1 milligram 

per liter.

Additional Abbreviations

BOD = biochemical oxygen demand

FDEP = Florida Department of Environmental

 Protection

GC/FID = gas chromatograph/flame ionization detection

GC/MS = gas chromatograph/mass spectrometer

MCL = maximum contaminant level

μg/L = micrograms per liter

mg/L = milligrams per liter

SMCL = secondary maximum contaminant level

USGS = U.S. Geological Survey

WATSTORE = National Water Data Storage and Retrieval

 System
Introduction 1

Water Quality of the Boca Raton Canal System and 

Effects of the Hillsboro Canal Inflow, Southeastern 

Florida, 1990-91

By Donald J. McKenzie

Abstract

The City of Boca Raton in southeastern Palm 

Beach County, Florida, is an urban residential area 

that has sustained a constant population growth 

with subsequent increase in water use. The Boca 

Raton network of canals is controlled to provide 

for drainage of excess water, to maintain proper 

coastal ground-water levels to prevent saltwater 

intrusion, and to recharge the surficial aquifer 

system from which the city withdraws potable 

water.

Most of the water supplied to the Boca Raton 

canal system and the surficial aquifer system, 

other than rainfall and runoff, is pumped from the 

Hillsboro Canal. The Biscayne aquifer, principal 

hydrogeologic unit of the surficial aquifer system, 

is highly permeable and there is a close relation 

between water levels in the canals and the aquifer. 

The amount of water supplied by seepage from the 

conservation areas is unknown. Because the 

Hillsboro Canal flows from Lake Okeechobee and 

Water Conservation Areas 1 and 2, which are 

places of more highly mineralized ground water 

and surface water, the canal is a possible source of 

contamination.

Water samples were collected at 10 canal sites 

during wet and dry seasons and analyzed for major 

inorganic ions and related characteristics, nutrients, and trace elements. All concentrations were 

generally within or less than the drinking-water 

standards established by the Florida Department 

of Environmental Protection. The high concentrations of sodium and chloride that were detected in 

samples from the Boca Raton canal system are 

probably from the more mineralized water of the 

Hillsboro Canal.

Other water-quality data, gathered from various 

sources from 1982 through 1991, are limited and 

do not indicate any significant changes nor trends. 

The data include pesticide and metal analyses of 

water samples and bottom sediments collected at 

four canal sites in the Boca Raton study area by the 

U.S. Geological Survey during 1982-84.

The effects of the Hillsboro Canal on the water 

quality of the Boca Raton canal system are indicated by increased concentrations of sodium, chloride, dissolved solids, and total organic carbon. 

Concentrations of the constituents in the canal 

water generally decrease with distance from the 

Hillsboro Canal pumping station and are the result 

of dilution by receiving canal waters.

INTRODUCTION

The city of Boca Raton is located in the southeastern 

corner of Palm Beach County (fig. 1) in southeastern 

Florida. The study area, about 48 mi2

, extends from 

Florida’s Turnpike east to the Intracoastal Waterway 

and is bounded on the north by the C-15 Canal (Lateral 

39) and on the south by the Hillsboro Canal (fig. 1). 

This mostly suburban area is characterized by spacious 

lawns and many golf courses. The dense residential, 

commercial, and light industrial development is generally limited to the coastal ridge area. Agriculture has 

been displaced as residential construction has spread 

westward to Florida’s Turnpike and beyond.
2 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

Figure 1. Location of the Boca Raton study area in Palm Beach County, southeastern 

Florida.
Introduction 3

The population of Boca Raton in 1990 was about

83,000, an increase of almost 16 percent from 1985. 

The population is expected to grow almost another 10 

percent in the next 5 years. The population of Palm

Beach County is also increasing rapidly. In 1990, there

were almost 1,000,000 people; the population is projected to reach 1,216,600 by 1995. The increased 

demand for potable water required greater pumpage

from the Hillsboro Canal, which is the major source of 

recharge for Boca Raton’s canal and well-field system 

within the Lake Worth Drainage District network.

Boca Raton officials became concerned that the

water quality of the canals that recharge the city’s well

fields could be degraded by water from the Hillsboro

Canal, which originates at Lake Okeechobee and flows

through an area of organic soils, intensive agriculture, 

and highly mineralized ground water. There have been 

sporadic water-quality analyses of the Boca Raton 

canals in recent years, but because of varying sampling 

sites and infrequent sampling, appraisal of waterquality conditions and trends has not been feasible. 

As a result, the U.S. Geological Survey (USGS), in

cooperation with the City of Boca Raton, conducted a 

water-quality study of the canals from October 1989 

to September 1992.

Purpose and Scope

The purpose of this report is to characterize the water 

quality of the Boca Raton canal system. Specifically,

the report provides baseline water-quality data for 

1990-91 from which future trends can be delineated, 

and it describes some of the effects of the Hillsboro

Canal on the water quality of the Boca Raton canal 

waters, the principal source of surficial aquifer system

recharge.

Canal sampling sites were selected according to 

the movement of water, volume, direction, and distance from the Hillsboro Canal. Water samples were

collected and analyzed for major inorganic ions and

related characteristics, nutrients, and trace elements. 

Additionally, gas chromatograph/flame ionization 

detection (GC/FID) reconnaissance sampling was

conducted to qualitatively detect organic compounds. 

Data were evaluated and analyzed using summary

statistics for selected constituents. Special consideration was given to constituent trends and the seasonal 

effects of rainfall with subsequent flow from the 

Hillsboro Canal.

Water-quality data from the Boca Raton canal 

system were collected by several agencies prior to this 

study. Agencies that furnished data for the review

include the USGS, Florida Department of Environmental Protection (FDEP), South Florida Water

Management District, Lake Worth Drainage District, 

and the City of Boca Raton.

Water Supply and Canal System

The water that flows from the Hillsboro Canal into 

the Boca Raton area is the principal recharge, other

than rainfall and runoff, for the Boca Raton canal

system and the surficial aquifer system, which is the 

source of the potable water supply. There is a close

relation between water levels in the canals and in the

surficial aquifer system (Swayze and Miller, 1984,

p. 2).

Average annual rainfall in southeastern Florida 

ranges from 58 to 64 in. (Klein and Hull, 1978, p. 15). 

About 75 percent of the total annual rainfall generally 

occurs during the wet season, from June to October

(Klein and others, 1975, p. 22). The amount of total

rainfall that recharges the surficial aquifersystem, after

evapotranspiration and runoff, annually averages 37 or

38 in. (Schroeder and others, 1958, p. 37; Fish, 1988, 

p. 66).

Rapidly increasing water demands in the Boca 

Raton area have required that larger amounts of water

be pumped from the Hillsboro Canal into the Boca

Raton canal system to recharge the surficial aquifer

system. The water supply for Boca Raton consists principally of 26 wells that closely parallel the E-3 Canal,

about 12 wells that are 0.5 mi east of the E-4 canal, and

about 11 wells that closely parallel the E-4 Canal (fig. 2).

New wells are planned for northwestern Boca Raton.

The Boca Raton canal system lies south of the C-15 

Canal and north of the Hillsboro Canal in the southern 

part of the Lake Worth Drainage District (fig. 1). This 

canal system is part of a larger network of canals 

operated and controlled by the Lake Worth Drainage 

District. Water is distributed by large equalizer canals 

that allow water to flow north and south and by small 

lateral canals spaced about 0.5 mi apart that allow flow 

east and west (fig. 2). Water levels are regulated by 

pumps and control structures. Generally, the control 

structures allow water to drain in stages from 15.5 ft 

above sea level in the western area near Florida’s Turnpike to 8.5 ft above sea level in the E-4 Canal system 

near the coast, which is a barrier to saltwater intrusion.
4 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

Figure 2. Location of sampling sites, the general area of potable water-supply wells, and the average major-ion composition of water samples from the sampling sites in the Boca Raton canal system.
Water Quality of the Boca Raton Canal System and Effects of Hillsboro Canal Inflow 5

During seasonal rainfall, the canal network channels 

water to storage areas, such as Lake Okeechobee and 

Water Conservation Area 1 (fig. 1), and to the sea to 

avoid flooding. During rainfall shortages, the water is 

conveyed from the storage areas back to coastal areas 

for aquifer recharge and prevention of saltwater intrusion. The sole pumping structure used to withdraw 

water from the Hillsboro Canal is located at the 

juncture with the E-2 canal (fig. 2).

Surficial Aquifer System

The surficial aquifer system is the primary source 

of freshwater for Boca Raton and all of coastal Palm 

Beach County. Most well fields are located in a discontinuous zone of high permeability in the surficial 

aquifer system that extends from the Juno Beach area 

south to Broward County (fig. 1). This is the northernmost extension of the Biscayne aquifer (Swayze and 

Miller, 1984, p. 1).

The unconfined Biscayne aquifer is the principal 

hydrogeologic unit of the surficial aquifer system and is 

composed of highly porous interbedded sandstone and 

limestone. The high permeability is caused largely by 

extensive carbonate dissolution. The Biscayne aquifer is 

wedge shaped and ranges in thickness from about 20 ft 

on the western edge of Palm Beach County to more than 

300 ft in areas along the eastern coast. The aquifer 

becomes more sandy and somewhat less permeable in 

southeastern Palm Beach County (Klein and Hull, 1978, 

p. 3; Klein and Causaras, 1982; and Fish, 1988, p. 61). 

However, transmissivities are high, ranging from 1,000 

ft2

/d along the flanks to 100,000 ft2/d along the axis. The 

high transmissivity promotes a quick response between 

surface-water and ground-water levels.

Sampling Procedures and Analytical Methods

The sampling sites used for this study (which were 

also used prior to this study) were selected for representative areal coverage of the Boca Raton canal system, 

year-round flow conditions, and the presence of a bridge 

to provide proper access for sampling (fig. 2). Standard 

USGS procedures were applied during sample collection. Water samples representing the overall composition of the canals were obtained by compositing several 

depth integrated samples of equal volume taken from the 

bridges at places of estimated equal flow. A stainless 

steel basket sampler was raised and lowered from the 

bridge at 5- to 6-ft intervals and the individual depthintegrated samples combined in a churn-splitter.

The composited water samples for major inorganic 

ions, total nutrient concentrations, total trace-element 

concentrations, and physical constituents were placed 

in polyethylene bottles for analysis by the USGS 

Quality of Water Service Unit in Ocala, Fla. Analytical 

methods used are described by Fishman and Friedman 

(1989).

Quality assurance practices included field split 

samples for each sampling event and standard reference samples for inorganic analyses. Data were stored 

in the National Water Data Storage and Retrieval 

System (WATSTORE).

Whole-water samples for analyses of synthetic 

organic compounds were placed in glass containers 

(supplied by the Quality of Water Service Unit in 

Ocala) and preserved with mercuric chloride as a bactericide, then packed in ice and shipped for overnight 

delivery to the USGS Laboratory in Ocala. Samples 

were analyzed by the GC/FID method for reconnaissance and the gas chromatograph/mass spectrometer 

(GC/MS) method for specific compound identification 

by laboratories of the USGS. The GC/FID analysis, or 

FID scan, is a screening technique for the determination of synthetic organic compounds in water. The FID 

scan analysis provides semiquantitative data without 

identification of specific compounds. When the FID 

scan analysis indicates a significant amount of a certain 

synthetic organic compounds is present, the GC/MS 

analytical method is used to confirm the presence of the 

particular constituent. The analytical methods for 

determination of organic substances are described by 

Wershaw and others (1983). Analyses by mass 

spectrometer were made by the USGS National Water 

Quality Laboratory in Denver, Colo.

WATER QUALITY OF THE BOCA RATON 

CANAL SYSTEM AND EFFECTS OF 

HILLSBORO CANAL INFLOW

Various physical characteristics and chemical 

constituents, naturally occurring and those introduced 

by man’s activities, were monitored in the Boca Raton 

canal system to assess its present water quality and 

determine the effects of the Hillsboro Canal inflow. 

Assessment of present constituent concentrations is 

important for management of water resources as a 

measure of baseline conditions and as a reference to 

determine any future changes. For example, some of 

the constituents, such as nitrogen and phosphorus in 

different chemical forms, are used as indicators of 
6 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

agricultural or urban runoff. These constituents have 

been extensively sampled in southern Florida, and 

comparison of concentrations from developed and 

undeveloped areas can be made. Additionally, 

increases in concentrations of selected constituents, 

such as trace elements and synthetic organic compounds, might cause the water in the Boca Raton canal 

system to be less desirable for public use and cause 

degradation of the conservation storage areas when 

backpumping occurs.

Historical Water-Quality Data

The surficial aquifer system in Palm Beach County 

has been the subject of many geologic, hydrologic, and 

water-quality studies, some with direct application to 

the Boca Raton study area. The earliest and most 

comprehensive report about the hydrology, geology, 

and water quality was provided by Parker and others 

(1955). Countywide studies by Land (1972), Klein and 

Hull (1978), Fischer (1980), and Causaras (1982) offer 

comprehensive overviews of ground-water and surface-water quality, aquifer hydraulics, and geology. 

Studies more specific to the Boca Raton area include 

McCoy and Hardee (1970), Land and others (1973), 

and Miller and Lietz (1976).

The Lake Worth Drainage District conducted a 

sampling program at two canal sites in the Boca Raton 

canal system. Sampling on the E-3 Canal at site 2 and 

on the El Rio Canal at site 6 was conducted monthly 

from 1983 through 1991 (fig. 2). The characteristics 

determined included biochemical oxygen demand 

(BOD), specific conductance, dissolved calcium, 

dissolved magnesium, dissolved oxygen, sodium, and 

dissolved solids.

Concentrations of BOD indicate the amounts of 

oxygen-consuming material in the water. BOD concentrations greater than 3.0 mg/L (milligrams per liter) 

indicate a level of oxygen-demanding materials that 

commonly result from sewage effluent or contaminantladen runoff. The average BOD concentrations in water 

samples at sites 2 and 6 were 2.1 and 2.6 mg/L, respectively, indicating that the sites did not receive excessive 

oxygen-demanding materials. The average dissolvedoxygen concentration for the 9-year period was 7.1 mg/L 

at site 2 and 6.3 mg/L at site 6.

Analysis of dissolved solids measures the amount 

of dissolved material in a water sample and is used to 

evaluate the overall inorganic chemical composition. 

The annual average dissolved-solids concentrations for 

sites 2 and 6 from 1983 through 1991 are shown in 

figure 3. The data from 1983 through 1989 are from the 

Lake Worth Drainage District sampling program, and 

the 1990-91 data are from the USGS study. The same 

sites were used in both sampling programs. The dissolved-solids concentrations ranged from 209 to 316 

mg/L at site 2 and from 169 to 230 mg/L at site 6. The 

low range of concentrations and the slight decrease that 

occurred during the period of record (1983-91) might 

be due to increased dilution by rainfall or distance from 

the Hillsboro Canal.

The USGS analyzed whole-water samples for trace 

elements on five occasions from May 1982 to April 

1984 at canal sites 2, 3, 4, and 9. The sampling sites, 

protocols, and analytical methods were the same as 

those used for this study. Results of the water sample 

analyses are given in table 1, which includes the maximum contaminant levels (MCL’s) and secondary maximum contaminant levels (SMCL’s) established by the 

Florida Department of Environmental Protection 

(1993) for drinking-water requirements. None of the 

constituents, except for iron, exceeded the levels.

Water samples and bottom sediments were also 

collected from 1982 through 1984 for the analyses of 

chlorophenoxy acid herbicides and organochlorine 

insecticides at sites 2, 3, 4, and 9 (fig. 2). Water samples 

were also analyzed for organophosphorus insecticides. 

No concentrations exceeded the MCL’s for primary 

drinking-water standards of the Florida Department of 

Environmental Protection (1993).

Major Inorganic Ions and Related 

Characteristics

From July 1990 to July 1991, canal water samples 

were collected at least 5 times during wet and dry seasons (fig. 4) at 10 sites (fig. 2) in the Boca Raton study 

area and analyzed for major ions, color, pH, hardness, 

dissolved solids, specific conductance, and alkalinity. 

Major-ion chemistry and related data were used as a 

general indicator of water quality and to: (1) identify 

some of the physical-chemical processes that affect the 

composition of natural waters, and (2) assess differences in the Boca Raton canal system water quality and 

changes in quality with time.

The areal distribution of major ions in the canal 

water was evaluated using polygonal Stiff diagrams 

(Stiff, 1951) as shown in figure 2. The average concentrations of major cations and anions for each site were 

converted to milliequivalents per liter and are plotted on 

their respective axis. The respective points are connected 

to form an irregular polygonal shape that provides visual 
Water Quality of the Boca Raton Canal System and Effects of Hillsboro Canal Inflow 7

Figure 3. Annual average concentrations of dissolved solids at two sites in the Boca Raton canal system. (1983-

89, Lake Worth Drainage District data; 1990-91, U.S. Geological Survey data. Site locations shown in figure 2.)

Table 1. Summary of concentrations of total recoverable trace elements 

for four sampling sites in the Boca Raton canal system, 1982-84

[Total concentrations in micrograms per liter; FDEP standard, Florida Department of 

Environmental Protection (1993) drinking water regulations standard; <, less than 

the value]

 1Maximum contaminant level (MCL): The maximum permissible level of a 

contaminant in water, which is delivered to any user of a public-water system.

 2Secondary maximum contaminant level (SMCL): Contaminants that affect 

the esthetic quality of drinking water. At high concentrations or values, health 

implications as well as esthetic degradation can also exist.

Trace

element

No. of

samples Minimum Maximum Mean FDEP

standard

Arsenic 26 1 9 2 150

Barium 26 <100 <100 <100 12,000

Cadmium 26 <1 1 <1 150

Chromium 26 <10 20 10 1

100

Copper 26 4 84 10 21,000

Iron 21 110 590 338 2300

Lead 17 1 7 3 1

15

Manganese 21 <10 50 16 250

Mercury 21 < .1 1.7 <1.0 12

Selenium 21 <1 <1.0 <1 150

Silver 21 <1 <1.0 <1 2100

Zinc 21 10 150 32 25,000
8 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

on their respective axis. The respective points are connected to form an irregular polygonal shape that provides visual representation of the water’s composition. 

The diagram widens as milliequivalent concentrations 

increase for individual constituents. Differences or similarities in water quality with respect to major ions can be 

recognized by comparing the polygonal diagrams.

A summary of the concentrations of selected major 

inorganic ions and related characteristics indicates that 

the dominant ions are calcium and bicarbonate, which 

are products of limestone dissolution (table 2). Concentrations of sodium and chloride are also relatively high. 

Concentrations reported as less than minimum determination levels for analytical results were treated as 0.0 

concentrations for the summary statistics in table 2.

The concentrations of major ions (calcium, 

sodium, bicarbonate, and chloride) were greater in and 

near the Hillsboro Canal (fig. 2, sites 1-5). Water in this 

part of the Boca Raton canal system is affected by the 

Hillsboro Canal water channeled from conservation 

and agricultural areas to the west. Water from these 

lands typically is high in sodium and chloride concentrations derived from ground water used for irrigation 

and from connate seawater (Parker and others, 1955; 

Waller and Earle, 1975). During low-flow conditions, 

highly mineralized ground water (greater than 500 mg/L 

of dissolved-solids concentration) is discharged into 

the Hillsboro Canal with only slight dilution by surface 

water. This results in average concentrations of major 

ions which are above the overall average of other 

canals that discharge from the conservation area 

(Waller and Miller, 1982, p. 13). Water in the eastern 

and northern parts of the Boca Raton canal system is 

less affected by water from the Hillsboro Canal, thus, 

sodium and chloride concentrations are smaller.

The effects of Hillsboro Canal on the water quality 

of the Boca Raton canal system is demonstrated by the 

dissolved-solids concentrations. Canal water at sites 

nearest to the Hillsboro Canal (within a 3.5-mi radius) 

had the highest dissolved-solids concentrations, from 

an average of 424 mg/L at site 1 on the Hillsboro Canal 

to an average of 325 mg/L at site 4 (3.5 mi from the 

pumping station). At other sampling sites, located 5.5 

to 7.0 mi from the Hillsboro Canal, canal water had 

dissolved-solids concentrations ranging from 229 to 

282 mg/L. The dissolved-solids concentrations 

Figure 4. Monthly average rainfall and month when canal water-quality sampling occurred, 1990-91.
Water Quality of the Boca Raton Canal System and Effects of Hillsboro Canal Inflow 9

Table 2. Summary of concentrations of major inorganic ions and related characteristics, nutrients, and total recoverable 

trace elements for all sampling sites in the Boca Raton canal system, July 1990 to July 1991

[FDEP standard, Florida Department of Environmental Protection (1993) drinking water regulations standard; --, no standard; mg/L, 

milligrams per liter; Pt-Co, platinum-cobalt units; μS/cm, microsiemens per centimeter; <, less than the value]

________________________________________________________________________________

 No. of FDEP

 Variable samples Minimum Maximum Mean standard

________________________________________________________________________________

Major dissolved inorganic ions and related characteristics

Color, in Pt-Co units 51 40 100 74 215

pH, in standard units 51 7.2 8.5 7.8 26.5–8.5

Hardness, in mg/L 51 97 280 189 --

Dissolved solids, residue at 60 180 486 308 2

500

 180 degrees Celsius

Specific conductance, in μS/cm 51 295 786 504 --

Bicarbonate, in mg/L 51 79 286 190 --

Alkalinity, as CaCO3 51 65 235 156 --

Calcium, in mg/L 51 29 100 65 --

Magnesium, in mg/L 51 2.6 8.4 5.9 --

Sodium, in mg/L 51 11 65 28 1

160

Potassium, in mg/L 51 2.3 14 7.1 --

Chloride, in mg/L 51 23 100 46 2

250

Sulfate, in mg/L 51 11 44 27 2

250

Fluoride, in mg/L 51 .1 .4 .2 22

Silica, in mg/L 51 1.5 11 5.5 --

Nutrients (in milligrams per liter)

Organic nitrogen, total 92 0.70 2.5 1.08 --

Ammonia nitrogen, total 92 .01 .34 .11 --

Nitrite nitrogen, total 92 < .01 .04 .02 1

1

Nitrate nitrogen, total 92 < .01 .50 .15 110

Phosphorus, total 92 .03 .54 .13 --

Orthophosphorus, total 92 .01 .29 .08 --

Organic carbon, total 59 9.8 23 14 --

Trace elements (in micrograms per liter)

Arsenic 23 <1 4 2 150

Barium 31 <100 160 <100 12,000

Boron 21 40 120 80 --

Cadmium 51 <1 1 <1 150

Chromium 51 <1 4 1 1

100

Copper 51 2 38 7 21,000

Iron 51 40 920 204 2

300

Lead 51 <1 3 <1 1

15

Manganese 31 10 <10 18 250

Mercury 31 <1 1 <1 12

Selenium 21 <1 <1 <1 150

Silver 31 <1 1 <1 2100

Zinc 51 <10 20 <10 25,000

________________________________________________________________________________

1

Maximum contaminant level (MCL): The maximum permissible level of a contaminant in water, which is delivered to any user of a 

public-water system. 2

Secondary maximum contaminant level (SMCL): Contaminants that affect the esthetic quality of drinking water. At high 

concentrations or values, health implications as well as esthetic degradation can also exist.
10 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

analyzed during this study are similar to those concentrations analyzed in previous studies at canal sites 2 and 

6 shown in figure 3.

The Boca Raton canal system receives the more 

highly mineralized water from the Hillsboro Canal 

during the dry season. Dissolved-solids concentrations 

were highest in December 1990 when low precipitation 

occurred (fig. 4). Conversely, concentrations generally 

were lowest in July 1990 when precipitation was 

greater. This relation is illustrated by comparison of 

dissolved-solids concentrations at each canal sampling 

site during these months (fig. 5). Sites 2 to 5, closest to 

Hillsboro Canal (fig. 2), also show the greatest concentrations of dissolved solids, which indicate a direct 

relation with proximity to Hillsboro Canal.

The color of water samples is generally the product 

of the leaching of decaying vegetation in the surface 

environment. The color values of the Boca Raton canal 

water system exceeded the secondary drinking-water 

standard established by the Florida Department of 

Environmental Protection (1993) for all the samples 

during this study (table 2). This is attributed to the organic 

soils through which the Hillsboro Canal flows from 

Lake Okeechobee and the Everglades to Boca Raton.

Nutrients

The nutrients analyzed from the Boca Raton canal 

system were nitrogen and phosphorus compounds and 

organic carbon compounds. The source of the nutrients 

in the Boca Raton canals is mostly plant detritus, living 

plants, and nutrient-laden runoff (fertilizers applied to 

golf courses and lawns). Additionally, water in contact 

with the peat and muck soils of the conservation area 

characteristically has high concentrations of organic 

carbon and organic nitrogen (Waller and Earle, 1975). 

Waller and Miller (1982, p. 24) indicated that 6-year 

average concentrations of total organic carbon were 25 

mg/L in the conservation area water and 22 mg/L in the 

Hillsboro Canal.

Figure 5. Dissolved-solids concentrations for each water-quality sampling site, July 17, 1990, and December 11, 1990.
Water Quality of the Boca Raton Canal System and Effects of Hillsboro Canal Inflow 11

Organic nitrogen was the dominant form of total 

nitrogen in the canal waters. The mean concentration at 

site 1 on the Hillsboro Canal was 1.21 mg/L, which was 

slightly greater than the 1.08 mg/L mean total concentration at all of the sites (table 2). Nitrate nitrogen concentrations ranged from less than 0.01 mg/L to 0.50 

mg/L, well below the MCL drinking-water standard

established by the Florida Department of Environmental Protection (1993). The mean nitrate nitrogen concentration at site 1 was 0.23 mg/L, which was greater

than the 0.15 mg/L nitrate nitrogen mean total concentrations at all of the sites (table 2).

Total orthophosphorus concentrations varied 

slightly with time or sampling location, ranging from 

0.01 to 0.29 mg/L; the mean concentration of 92 

samples was 0.08 mg/L. The FDEP has not established 

MCL or SMCL standards for total orthophosphorus 

concentration in drinking water.

Total organic carbon concentrations ranged from 

9.8 to 23 mg/L in the Boca Raton canal system. There 

was little variation spatially and temporally, except for 

the sampling event of December 1990, a period of low 

precipitation (fig. 4). Sites 1 to 5 had a mean total 

organic carbon concentration of 20 mg/L for December 

1990. The other sites, farther from the Hillsboro Canal,

had a mean concentration of about 14 mg/L for the 

December sampling. The higher total organic carbon 

concentrations for the sampling indicate a greater flow 

of water to the Hillsboro Canal from the conservation 

area during the time of low rainfall.

Trace Elements

Samples for trace-element analysis were collected 

at allstudy sites on the Hillsboro Canal and in the Boca 

Raton canal system. The mean concentrations for most

of the trace elements were lower than established 

MCL’s or SMCL’s (table 2); no MCL or SMCL has 

been established for boron. The individual concentrations of lead, mercury, selenium, and silver were generally less than or very close to analytical detection 

limits. Only total iron in some analyses exceeded the 

SMCL of 300 μg/L. The concentrations of total iron 

vary widely in southern Florida waters and are commonly high because of ferriferous lithology (Parker

and others, 1955, p. 371). There were no significant 

differences in trace-element concentrations at the sampling sites, and there was no apparent influence from 

the Hillsboro Canal.

Comparison of the previous data from May 1982 

through April 1984 (table 1) and the data for this study 

(table 2) indicates a similar water chemistry of trace 

elementsfor the two periods. Totalrecoverable chromium

is reported at a different level of analytical detection in

the two sets of analyses (10 μg/L for the historical data

and 1 μg/L for this study), but the data did not indicate

notable changes between the two periods.

Pesticides

Pesticides (herbicides and insecticides) can be 

introduced to the canals in runoff and by direct spraying 

of: (1) insecticides for control of insects, and (2) herbicides for control of terrestrial and aquatic weeds. Water 

samples were collected on two different occasions at all 

of the canal sampling sites for a GC/FID scan analysis. 

Results of GC/FID scans from the first sampling on 

August 8, 1990, indicated that only one site contained 

a detectable but very low level of organic compounds. 

The second series of samples taken on October 3, 1990, 

indicated measurable, but very low, concentrations of 

organic compounds at 7 of 10 sites.

To confirm the absence of significant pesticide 

concentration in canal water, four of the water-quality 

sites used in this study were selected for GC/MS analysis. The four sites correspond to sites sampled for pesticide analysis by the USGS in 1982-84. The pesticide 

analyses made for the two sampling periods (1982-84 

and 1990) were the same and included chlorophenoxy 

acid herbicide and organochlorine insecticide analyses 

of water and bottom sediments and organophosphorus 

insecticide analyses of the water samples. The same 

collection methods and analytical laboratory as 

described in the “Methods” section were used for the 

two sampling periods (1982-84 and 1990).

Organochlorine insecticides include the DDT family (DDT, DDE, and DDD), dieldrin, endrin, chlordane, 

and toxaphene; organophosphates include parathion, 

malathion, and diazinon; and chlorophenoxy acid 

herbicides include silvex and 2,4-D. Many of the pesticides are relatively insoluble in water and are more 

common in bottom sediments. The effects of such 

accumulation are not well defined and recommended 

limits have not been established.

The analytical results of this study are similar to the 

data previously collected by the USGS in 1982-84. No 

water samples contained pesticide concentrations that 

exceeded potable water standards established by the 

Florida Department of Environmental Protection 
12 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

(1993). Most of the compounds were absent or less 

than analytical detection limits. Results for bottom 

sediments were similar. DDT and its metabolites were 

detected at the four sites, but in low concentrations.

SUMMARY AND CONCLUSIONS

The Boca Raton network of canals is a highly 

controlled water-management system that provides for 

drainage of excess water, maintains proper coastal 

ground-water levels to prevent saltwater intrusion, and 

recharges the surficial aquifer system from which the 

city of Boca Raton withdraws potable water. Control 

structures allow water to drain in stages from 15.5 ft 

above sea level in the western area near Florida’s Turnpike to 8.5 ft above sea level in the E-4 Canal system 

near the coast (a barrier to saltwater intrusion). Most of 

the water supplied to the Boca Raton canal system and 

the surficial aquifer system, other than rainfall and runoff, is pumped from the Hillsboro Canal.

The Biscayne aquifer, principal hydrogeologic unit 

of the surficial aquifer system, is highly permeable, and 

there is a close relation between water levels in the 

canals and the aquifer. The city of Boca Raton has 

become concerned that the water quality of the canals 

that recharge the city’s well fields could be degraded by 

water from the Hillsboro Canal, which originates at 

Lake Okeechobee and flows through an area of organic 

soils, intensive agriculture, and highly mineralized 

ground water.

The Lake Worth Drainage District conducted a 

sampling program at two canal sites in the Boca Raton 

canal system from 1983 through 1991. Concentrations 

of BOD and dissolved solids were determined at site 2 

on the E-3 Canal and site 6 on the El Rio Canal. BOD 

concentrations greater than 3.0 mg/L indicate a level of 

oxygen-demanding materials that commonly result 

from sewage effluent or contaminant-laden runoff. The 

monthly average BOD concentrations at sites 2 and 6 

were 2.1 and 2.6 mg/L, respectively, indicating that the 

sites did not receive excessive oxygen-demanding 

materials. The annual average dissolved-solids concentrations ranged from 209 to 316 mg/L at site 2 and from 

169 to 230 mg/L at site 6. The low range of concentrations and the slight decrease that occurred during the 

period of record (1983-91) might be due to increased 

dilution by rainfall or distance from the Hillsboro 

Canal.

From July 1990 through July 1991, the USGS 

collected water samples from 10 canal sites during wet 

and dry seasons to determine concentrations of major 

inorganic ions and related characteristics, nutrients, 

and trace elements. Standard USGS procedures were 

used during sample collection. Collected composited 

water samples were placed in polyethylene bottles for 

analysis by the USGS Quality of Service Unit in Ocala, 

Fla. Quality assurance practices included field split 

samples for each sampling event and standard reference samples for inorganic analyses. Additionally 

water samples for analyses of synthetic organic compounds were collected from the 10 canal sites on two 

occasions (August 8, 1990 and October 3, 1990). 

Whole-water samples for these analyses were placed in 

glass containers preserved with mercuric chloride, 

packed in ice, and shipped overnight to the USGS 

Laboratory in Ocala. Samples were analyzed by the 

GS/FID method for reconnaissance and the GC/MS 

method for specific compound identification by USGS 

laboratories.

Results indicate that the dominant ions are calcium 

and bicarbonate, which are products of limestone dissolution. Concentrations of sodium and chloride are 

also relatively high. The concentrations of calcium, 

bicarbonate, sodium, and chloride were greater at sites 

in and near the Hillsboro Canal than at sites farther 

from Hillsboro Canal. The quality of water in the 

southern part of the Boca Raton canal system is 

affected by the Hillsboro Canal water channeled from 

conservation and agricultural areas to the west. Water 

from these lands is typically high in sodium and chloride concentrations. Water in the eastern and northern 

parts of the Boca Raton canal system is less affected by 

water from the Hillsboro Canal, thus, sodium and chloride concentrations are smaller. Canal water at sites 

nearest to the Hillsboro Canal also had the highest dissolved-solids concentrations, and color values 

exceeded the drinking-water standard established by 

the FDEP for all the water samples. The high color 

values are attributed to the organic soils through which 

the Hillsboro Canal flows from Lake Okeechobee and 

the Everglades to Boca Raton.

The nutrients analyzed from the Boca Raton canal 

system were nitrogen and phosphorus compounds and 

organic compounds. Nutrients were generally uniform, 

spatially and temporally, among the canal sites. Total 

organic nitrogen was the dominant form of total nitrogen in the canal waters with concentrations ranging 

from 0.70 to 2.5 mg/L. No nutrient concentrations 

exceeded the MCL drinking-water standard established 

by the FDEP.
Selected References 13

None of the trace elements analyzed in the Boca 

Raton canal system, except for iron, had concentrations 

that exceeded the drinking-water standards established 

by the FDEP. The individual concentrations of lead, 

mercury, selenium, and silver were generally less than 

or very close to analytical detection limits. In some 

individual analyses, iron concentrations exceeded the 

SMCL of 300 μg/L. This is not uncommon in southern 

Florida waters where iron concentrations are high and 

vary widely because of ferriferous lithology. There was 

no significant differences in trace-element concentrations at the sampling sites, and there was no apparent 

influence from the Hillsboro Canal. Comparison of 

previous data collected from 1982 through 1984 indicates a similar water chemistry of trace elements.

Chlorophenoxy acid herbicide and organochlorine 

insecticide analyses of water and bottom sediments and 

organophosphorus insecticide analyses of the water 

samples were made to detect pesticides at four canals 

sites in 1982-84 and 1990. No water samples contained 

pesticide concentrations that exceeded the drinkingwater standards established by the FDEP. Most of the 

compounds were absent or less than analytical detection limits. Results for bottom sediments were similar. 

DDT and its metabolites were detected at the four sites, 

but in low concentrations.

The chemistry of the water in the Boca Raton canal 

system was affected by discharge from the Hillsboro 

Canal, even though concentrations of constituents were 

generally within drinking-water standards established 

by the FDEP. During the dry season, more highly mineralized water from the conservation areas was transported by the Hillsboro Canal and added to the Boca 

Raton canal system. This resulted in higher concentrations of sodium, chloride, dissolved solids, and total 

organic carbon at sampling sites nearest to the Hillsboro Canal pumping station. Concentrations of these 

constituents generally decrease with distance from the 

Hillsboro Canal. Comparison of previous water-quality 

data (1982-84) and data collected for this study 

(1990-91) did not indicate any notable changes nor 

trends for the Boca Raton canal system.

SELECTED REFERENCES

Adair and Brady, Inc., 1975, Aquifer and ground-water 

resource evaluation for the three seasons project, 

Jupiter, Florida: West Palm Beach, 73 p.

Causaras, C.R., 1982, Annotated bibliography of the 

geology and hydrology of the surficial aquifers in 

Dade, Broward, and Palm Beach Counties, Florida: 

U.S. Geological Survey Open-File Report 82-154, 59 p.

———1985, Geology of the surficial aquifer system, 

Broward County, Florida: U.S. Geological Survey 

Water-Resources Investigations Report 84-4068, 

167 p., 2 sheets.

Fischer, J.N., 1980, Evaluation of the cavity riddled zone of 

the shallow aquifer near Riviera Beach, Palm Beach 

County, Florida: U.S. Geological Survey WaterResources Investigations Report 80-60, 39 p.

Fish, J.E., 1988, Hydrogeology, aquifer characteristics, and 

ground-water flow of the surficial aquifer system, 

Broward County, Florida: U.S. Geological Survey 

Water-Resources Investigations Report 87-4034, 92 p.

Fishman, J.J., and Friedman, L.C., eds., 1989, Methods for 

the determination of inorganic substances in water and 

fluvial sediments: U.S. Geological Survey Techniques 

of Water-Resources Investigations, book 5, chap. A1, 

709 p.

Florida Department of Environmental Protection, 1993, 

Drinking water standards, monitoring and reporting: 

Chapter 17-550, Florida Administrative Code, 38 p.

Klein, Howard, Armbruster, J.T., McPherson, B.F., and 

Freiberger, H.J., 1975, Water and the south Florida 

environment: U.S. Geological Survey Water-Resources 

Investigations Report 24-75, 165 p.

Klein, Howard, and Causaras, C.R., 1982, Biscayne aquifer, 

southeast Florida, and continuous surficial aquifer to 

the north, in Principal aquifers in Florida: Franks, B.J., 

ed., U.S. Geological Survey Open-File Report 82-255, 

sheet 3.

Klein, Howard, and Hull, J.E., 1978, Biscayne aquifer, 

southeast Florida: U.S. Geological Survey WaterResources Investigations Report 78-107, 52 p.

Land, L.F., 1972, Progress report on water-resources investigations in Palm Beach County, Florida: U.S. Geological Survey Open-File Report FL 72014, 40 p.

Land, L.F., Rodis, H.G., and Schneider, J.J., 1973, 

Appraisal of the water resources of eastern Palm Beach 

County, Florida: Florida Geological Survey Report of 

Investigations 67, 64 p.

McCoy, H.G., and Hardee, Jack, 1970, Ground-water 

resources of the lower Hillsboro Canal area, southeastern Florida: Florida Geological Survey Report of Investigations 55, 44 p.

Miller, W.L., 1988, Description and evaluation of the effects 

of urban and agricultural development on the surficial 

aquifer system, Palm Beach County, Florida: U.S. Geological Survey Water-Resources Investigations Report 

88-4056.
14 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

Miller, W.L., and Lietz, A.C., 1976, Quality of water data, 

Palm Beach County, Florida, 1970-75: U.S. Geological 

Survey Open-File Report 76-784, 100 p.

Parker, G.G., Ferguson, G.E., Love, S.K., and others, 1955, 

Water resources of southeastern Florida with special 

reference to the geology and ground water in the Miami 

area: U.S. Geological Survey Water-Supply Paper 

1255, 965 p.

Radell, Mary Jo, and Katz, B.G., 1991, Major-ion and 

selected trace metal chemistry of the Biscayne aquifer, 

southeast Florida: U.S. Geological Survey WaterResources Investigations Report 91-4009, 18 p.

Rodis, H.G., and Land, L.F., 1976, The shallow aquifer—

a prime freshwater resources in eastern Palm Beach 

County, Florida: U.S. Geological Survey WaterResources Investigations Report 76-21, 12 p.

Schroeder, M.C., Klein, Howard, and Hoy, H.D., 1958, 

Biscayne aquifer of Dade and Broward Counties, 

Florida: Florida Geological Survey Report of Investigations 17, 56 p.

Stiff, H.A., Jr., 1951, The intepretation of chemical water 

analyses by means of patterns: Journal of Petroleum 

Technology, v. 3, no. 10, p. 15-17.

Swayze, L.J., and Miller, W.L., 1984, Hydrogeology of a 

zone of secondary permeability in the surficial aquifer 

of eastern Palm Beach County, Florida: U.S. Geological Survey Water-Resources Investigations Report 

83-4249, 38 p.

U.S. Environmental Protection Agency, 1977, Quality 

criteria for water: Washington, D.C., U.S. Government Printing Office, 256 p.

———1988a, Maximum contaminant level (subpart B or 

141, National interim primary drinking-water regulations): U.S. Code of Federal Regulations, Title 40, Parts 

100-149, revised July 1, 1988, p. 585-586.

———1988b, Secondary maximum contaminant levels 

(section 143.3 or part 143, National secondary drinking 

water regulations): U.S. Code of Federal Regulations, 

Title 40, Parts 100-149, revised July 1, 1988, p. 608.

———1989, Proposed rule, National primary and secondary drinking water regulations (sections 141.50, 

141.51, 141.61, and 141.62 of part 141 and 143.3 of 

part 143): U.S. Federal Register, v. 54, no. 97, May 22, 

1989, p. 22, 062-22, 160.

———1991, Final rule, National primary and secondary 

drinking water regulations—synthetic organic chemicals and inorganic chemicals (sections 141.11, 141.12, 

141.32, 141.50, 141.51, 141.61, and 141.62 of part 141 

and 143.3 of part 143): U.S. Federal Register, v. 56, 

no. 20, January 30, 1991, p. 3526-3597.

Waller, B.G., and Earle, J.E., 1975, Chemical and biological 

quality in part of The Everglades: southeastern Florida: 

U.S. Geological Survey Water-Resources Investigations Report 59-75, 156 p.

Waller, B.G, and Miller, W.L., 1982, Assessment of water 

quality in canals of eastern Broward County, 1969-74: 

U.S. Geological Survey Water-Resources Investigations Report 82-3, 70 p.

Wershaw, R.L., Fishman, M.J., Grabbe, R.R., and Lowe, 

L.E., 1983, Methods for the determination of organic 

substances in water and fluvial sediments: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 5, chap A3, 173 p.
14 Water Quality of the Boca Raton Canal System and Effects of the Hillsboro Canal Inflow, Southeastern Florida, 1990-91

Miller, W.L., and Lietz, A.C., 1976, Quality of water data, 

Palm Beach County, Florida, 1970-75: U.S. Geological 

Survey Open-File Report 76-784, 100 p.

Parker, G.G., Ferguson, G.E., Love, S.K., and others, 1955, 

Water resources of southeastern Florida with special 

reference to the geology and ground water in the Miami 

area: U.S. Geological Survey Water-Supply Paper 

1255, 965 p.

Radell, Mary Jo, and Katz, B.G., 1991, Major-ion and 

selected trace metal chemistry of the Biscayne aquifer, 

southeast Florida: U.S. Geological Survey WaterResources Investigations Report 91-4009, 18 p.

Rodis, H.G., and Land, L.F., 1976, The shallow aquifer—

a prime freshwater resources in eastern Palm Beach 

County, Florida: U.S. Geological Survey WaterResources Investigations Report 76-21, 12 p.

Schroeder, M.C., Klein, Howard, and Hoy, H.D., 1958, 

Biscayne aquifer of Dade and Broward Counties, 

Florida: Florida Geological Survey Report of Investigations 17, 56 p.

Stiff, H.A., Jr., 1951, The intepretation of chemical water 

analyses by means of patterns: Journal of Petroleum 

Technology, v. 3, no. 10, p. 15-17.

Swayze, L.J., and Miller, W.L., 1984, Hydrogeology of a 

zone of secondary permeability in the surficial aquifer 

of eastern Palm Beach County, Florida: U.S. Geological Survey Water-Resources Investigations Report 

83-4249, 38 p.

U.S. Environmental Protection Agency, 1977, Quality 

criteria for water: Washington, D.C., U.S. Government Printing Office, 256 p.

———1988a, Maximum contaminant level (subpart B or 

141, National interim primary drinking-water regulations): U.S. Code of Federal Regulations, Title 40, Parts 

100-149, revised July 1, 1988, p. 585-586.

———1988b, Secondary maximum contaminant levels 

(section 143.3 or part 143, National secondary drinking 

water regulations): U.S. Code of Federal Regulations, 

Title 40, Parts 100-149, revised July 1, 1988, p. 608.

———1989, Proposed rule, National primary and secondary drinking water regulations (sections 141.50, 

141.51, 141.61, and 141.62 of part 141 and 143.3 of 

part 143): U.S. Federal Register, v. 54, no. 97, May 22, 

1989, p. 22, 062-22, 160.

———1991, Final rule, National primary and secondary 

drinking water regulations—synthetic organic chemicals and inorganic chemicals (sections 141.11, 141.12, 

141.32, 141.50, 141.51, 141.61, and 141.62 of part 141 

and 143.3 of part 143): U.S. Federal Register, v. 56, 

no. 20, January 30, 1991, p. 3526-3597.

Waller, B.G., and Earle, J.E., 1975, Chemical and biological 

quality in part of The Everglades: southeastern Florida: 

U.S. Geological Survey Water-Resources Investigations Report 59-75, 156 p.

Waller, B.G, and Miller, W.L., 1982, Assessment of water 

quality in canals of eastern Broward County, 1969-74: 

U.S. Geological Survey Water-Resources Investigations Report 82-3, 70 p.

Wershaw, R.L., Fishman, M.J., Grabbe, R.R., and Lowe, 

L.E., 1983, Methods for the determination of organic 

substances in water and fluvial sediments: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 5, chap A3, 173 p.