Prepared in cooperation with the

Delaware Department of Natural Resources and Environmental Control

and the

Delaware Geological Survey

Occurrence and Distribution of Organic Chemicals 

and Nutrients and Comparison of Water-Quality 

Data from Public Drinking-Water Supplies in 

the Columbia Aquifer in Delaware, 2000–08

Scientific Investigations Report 2010–5206

U.S. Department of the Interior

U.S. Geological Survey

Occurrence and Distribution of Organic 

Chemicals and Nutrients and Comparison 

of Water-Quality Data from Public 

Drinking-Water Supplies in the Columbia 

Aquifer in Delaware, 2000–08

By Betzaida Reyes

Prepared in cooperation with the 

Delaware Department of Natural Resources and Environmental Control 

and the 

Delaware Geological Survey 

Scientific Investigations Report 2010–5206

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Reyes, B., 2010, Occurrence and distribution of organic chemicals and nutrients and comparison of water-quality data 

from public drinking-water supplies in the Columbia aquifer in Delaware, 2000–08: U.S. Geological Survey Scientific 

Investigations Report 2010–5206, 64 p.

ISBN 978-1-4113-3011-5
iii

Contents

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

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

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

Description of Study Area ............................................................................................................................3

Methods of Study...........................................................................................................................................3

Sampling Network ................................................................................................................................3

Sample Collection and Analysis.........................................................................................................3

Data Analysis.........................................................................................................................................5

Quality-Control Sampling ....................................................................................................................5

Age Dating..............................................................................................................................................5

Pesticides and Pesticide Degradates ...............................................................................................8

Volatile Organic Compounds ............................................................................................................14

Field Parameters, Nutrients and Major Ions, and Trace Elements.............................................24

Radium and Radon..............................................................................................................................30

Groundwater Age Results .................................................................................................................31

Summary........................................................................................................................................................33

Acknowledgments.......................................................................................................................................34

References Cited..........................................................................................................................................34

Appendix A. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Field parameters ........................................................................................................................40

Appendix B. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Nutrients......................................................................................................................................41

Appendix C. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Major ions and trace elements................................................................................................42

Appendix D. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Pesticides....................................................................................................................................43

Appendix E. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Pesticide degradates.................................................................................................................44

Appendix F. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Volatile organic compounds.....................................................................................................45

Appendix Ga. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Age dating: sulfur hexafluoride data.....................................................................................49

Appendix Gb. Groundwater-quality data for sampled public water-supply wells 

in the Columbia aquifer in Delaware, August through November, 2008

—Age dating: dissolved gas data...............................................................................................51

Appendix Ha. Quality-control data for sampled public water-supply wells in 

the Columbia aquifer in Delaware, August through November, 2008

—Nutrients......................................................................................................................................53
iv

Appendix Hb. Quality-control data for sampled public water-supply wells in 

the Columbia aquifer in Delaware, August through November, 2008

—Major ions and trace elements................................................................................................53

Appendix Hc. Quality-control data for sampled public water-supply wells in 

the Columbia aquifer in Delaware, August through November, 2008

—Pesticides....................................................................................................................................54

Appendix Hd. Quality-control data for sampled public water-supply wells in 

the Columbia aquifer in Delaware, August through November, 2008

—Pesticide degradates.................................................................................................................57

Appendix He. Quality-control data for sampled public water-supply wells in 

the Columbia aquifer in Delaware, August through November, 2008

—Volatile organic compounds.....................................................................................................59

Appendix Hf. Quality-control data for sampled public water-supply wells in 

the Columbia aquifer in Delaware, August through November, 2008

—Radiochemical activities...........................................................................................................64

Figures

1a–1b. Maps showing—

1a. Land use in the Atlantic Coastal Plain study area of Delaware ..................................4

1b. Locations of public water-supply wells sampled in 2008 in the 

Columbia aquifer in Delaware and comparison of pesticide 

and degradate detection frequencies in groundwater, 

2000 and 2008........................................................................................................................4

2. Graph showing pesticides and pesticide degradates in groundwater 

samples from public water-supply wells screened in the Columbia 

aquifer in Delaware, 2000 and 2008 .........................................................................................13

3. Map showing locations of public water-supply wells sampled in 2008 

in the Columbia aquifer in Delaware and comparison of volatile 

organic compound (VOC) detection frequencies in groundwater, 

2000 and 2008...............................................................................................................................15

4. Graph showing volatile organic compounds (VOCs) detected in 

groundwater samples from public water-supply wells screened in 

the Columbia aquifer in Delaware, 2000 and 2008.................................................................17

5. Map showing locations of public water-supply wells sampled in 

2008 in the Columbia aquifer in Delaware with exceedances of 

criteria and guidelines for nutrients and major ions detected in 

groundwater................................................................................................................................24

6. Boxplot showing distribution of nutrients (nitrate as nitrogen and 

total phosphorus), major ions (magnesium), and trace elements (iron) 

concentrations in different oxidation-reduction (redox) environments 

in the Columbia aquifer among the 30 public water-supply wells 

sampled in 2008...........................................................................................................................28

7. Graph showing relation of nitrate concentrations to dissolved-oxygen 

concentrations in the Columbia aquifer in Delaware, 2008.................................................29
v

8. Map showing locations of public water-supply wells sampled in 

2008 in the Columbia aquifer in Delaware for radiochemical activities ............................31

9–10. Graphs showing—

9. Relation of average modeled groundwater sample to (A) well depth, 

and (B) dissolved-oxygen concentrations in the Columbia aquifer 

in Delaware, 2008...............................................................................................................32

10. (A) comparison and (B) distribution of average modeled 

groundwater sample age over the 8-year study period from the 

22 sampled wells in the Columbia aquifer in Delaware, 2000 to 2008.......................33

Tables

1. Well-construction data for sampled public water-supply wells screened 

in the Columbia aquifer in Delaware during 2000 and 2008, and modeled 

ages of groundwater sampled in 2008 ......................................................................................6

2. Pesticides and pesticide degradates for which groundwater samples 

from public water-supply wells were analyzed in the Columbia aquifer 

in Delaware, 2000 and 2008.........................................................................................................8

3. Summary statistics for pesticides and pesticide degradates detected 

in groundwater samples from public water-supply wells screened in the 

Columbia aquifer in Delaware, and comparisons to U.S. Environmental 

Protection Agency Maximum Contaminant Levels and Health-Based 

Sceening Levels in 2000 and 2008..............................................................................................9

4. Volatile organic compounds for which groundwater samples from public 

water-supply wells were analyzed in the Columbia aquifer in Delaware, 

2000 and 2008...............................................................................................................................16

5. Summary statistics for volatile organic compounds in groundwater 

samples from public water-supply wells screened in the Columbia aquifer 

in Delaware, and comparisons to U.S. Environmental Protection Agency 

Maximum Contaminant Levels and Health-Based Sceening Levels in 

2000 and 2008...............................................................................................................................19

6. Summary statistics for selected field parameters, nutrients, major ions, 

and trace elements in groundwater samples from public water-supply 

wells screened in the Columbia aquifer in Delaware, and comparisons 

to U.S. Environmental Protection Agency Primary and Secondary Maximum 

Contaminant Levels and Health Advisory Limits, 2000 and 2008.........................................25

7. Radiochemical activities for groundwater samples from public watersupply wells screened in the Columbia aquifer in Delaware, and 

comparisons to U.S. Environmental Protection Agency Maximum 

Contaminant Levels in 2000 and 2008 ......................................................................................30
vi

Conversion Factors and Datum

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 0.3861 square mile (mi2)

Volume

liter (L) 0.2642 gallon (gal)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

Pressure

atmosphere, standard (atm) 101.3 kilopascal (kPa)

atmosphere, standard (atm) 760 millimeters of mercury (mmHg)

Radioactivity

picocurie per liter (pCi/L) 0.037 becquerel per liter (Bq/L)

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

 °F = (1.8 x °C) + 32

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

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

or micrograms per liter (μg/L).
vii

Glossary

Health-Based Screening Level (HBSL)

Benchmark concentrations of contaminants in water that may be of potential concern for 

human health, if exceeded. HBSLs are non-enforceable benchmarks that were developed by the 

U.S. Geological Survey (USGS) in collaboration with the U.S. Environmental Protection Agency 

(USEPA) and others using USEPA methodologies for establishing drinking-water guidelines and 

the most current, USEPA peer-reviewed, publicly available human-health toxicity information.

Health Advisory Limit (HAL)

A non-regulatory health-based reference level of chemical traces (usually in parts per million) 

in drinking water at which there are no adverse health risks when ingested over certain periods 

of time. Levels are established for 1 day, 10 days, long-term, and lifetime exposure periods. They 

contain a wide margin of safety, and are set forth by the Delaware Division of Public Health.

Maximum Contaminant Level (MCL) or Primary Maximum Contaminant Level (PMCL)

As used in this report, a USEPA drinking-water standard that is legally enforceable, and that 

sets the maximum permissible level of a contaminant in water that is delivered to any user of a 

public water system, at which no known or anticipated adverse effect on the health of persons 

occurs, and which allows an adequate margin of safety.

Secondary Maximum Contaminant Level (SMCL)

As used in this report, a USEPA secondary drinking-water standard, and non-enforceable 

guidelines regulating contaminants that may cause cosmetic or aesthetic effects (such as taste, 

odor, or color) in drinking water. USEPA recommends secondary standards for water systems 

but does not require compliance. However, states may choose to adopt them as enforceable 

standards.

Source Water

Source water is the raw (ambient) water collected at the supply well prior to water treatment. 

Following water treatment, source water is finished or drinking water.

Occurrence and Distribution of Organic Chemicals and 

Nutrients and Comparison of Water-Quality Data from 

Public Drinking-Water Supplies in the Columbia Aquifer 

in Delaware, 2000–08

By Betzaida Reyes

Abstract

The U.S. Geological Survey, in cooperation with 

the Delaware Department of Natural Resources and 

Environmental Control and the Delaware Geological Survey, 

conducted a groundwater-quality investigation to (a) describe 

the occurrence and distribution of selected contaminants, 

and (b) document any changes in groundwater quality in the 

Columbia aquifer public water-supply wells in the Coastal 

Plain in Delaware between 2000 and 2008. Thirty public 

water-supply wells located throughout the Columbia aquifer 

of the Delaware Coastal Plain were sampled from August 

through November of 2008. Twenty-two of the wells in the 

sampling network for this project were previously sampled in 

2000. Eight new wells were selected to replace wells no longer 

in use. Groundwater collected from the wells was analyzed for 

the occurrence and distribution of selected pesticides, pesticide 

degradates, volatile organic compounds, nutrients, and major 

inorganic ions. Nine of the wells were analyzed for radioactive 

elements (radium-226, radium-228, and radon). Groundwaterquality data were compared for sites sampled in both 2000 and 

2008 to document any changes in water quality. 

One or more pesticides were detected in samples from 29 

of the 30 wells. There were no significant differences in pesticide and pesticide degradate concentrations and similar compounds were detected when comparing sampling results from 

2000 and 2008. Pesticide and pesticide degradate concentrations were generally less than 1 microgram per liter. Twentyfour compounds, 14 pesticides, and 10 pesticide degradates 

were detected in at least one sample; the pesticide degradates, 

metolachlor ethanesulfonic acid, deethylatrazine, and alachlor ethanesulfonic acid were the most frequently detected 

compounds, each found in more than 50 percent of samples. 

Almost 80 percent of the detected pesticides were agricultural 

herbicides, which reflects the prevalence and wide distribution 

of agriculture in sampled areas, as well the dominance of agricultural pesticides among the target analytes for this study. No 

concentration of a pesticide or pesticide degradate exceeded 

any regulatory standard. Dieldrin, an insecticide that has been 

banned for several decades, was detected at a concentration 

that exceeded a non-regulatory health-based screening level of 

0.002 micrograms per liter at nine sites. 

 Volatile organic compounds (VOCs) were generally 

detected at concentrations of less than 1 microgram per liter, 

although 7 of the 31 detected VOCs had concentrations greater 

than 1 microgram per liter. There were no significant differences in VOC concentrations from 2000 to 2008; however, 

among the resampled wells, the mean number of VOCs 

detected per well was significantly different over the 8-year 

period. The number of VOCs detected per well decreased 

in 73 percent of the resampled wells; the decrease ranged 

from one to eight fewer detections in 2008 than in 2000. 

Chloroform and methyl tert-butyl ether were the most frequently detected VOCs, at 90 percent and 63 percent, respectively, among the 30 wells. Solvents were the most frequently 

detected class of VOCs. All measured concentrations of VOCs 

in groundwater were below established standards for drinking 

water and below other health-based guidelines. 

There were no significant differences in nutrient or 

major-ion concentrations between 2000 and 2008, however, 

the medians of two field measurements, pH and dissolved 

oxygen, were significantly higher in 2008 than in 2000 in the 

resampled wells. Although pH and dissolved oxygen were 

higher, water was still acidic and predominantly oxic. Nitrate 

was the predominant nutrient species in the Columbia aquifer, 

with a 90-percent detection frequency. The median nitrate concentration in groundwater was 4.88 milligrams per liter, which 

was slightly lower than, but not significantly different from, 

the median of 5.23 milligrams per liter for the 2000 samples. 

Concentrations of nitrate exceeded the U.S. Environmental 

Protection Agency’s Maximum Contaminant Level or Federal 

drinking-water standard of 10 milligrams per liter as nitrogen 

in samples from two wells. Eight of the 30 wells sampled 

had iron or manganese concentrations that exceeded the U.S. 

Environmental Protection Agency’s Secondary Maximum 

Contaminant Level; nine samples exceeded the Health 
2 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Advisory Limit set by the Delaware Division of Public Health 

of 20 milligrams per liter for sodium in drinking water.

Two radiochemical isotopes, radium-226 and radon-222, 

were detected in all nine groundwater samples analyzed; five 

samples had detectable levels of radium-228 activity. None 

of the samples exceeded the U.S Environmental Protection 

Agency’s Maximum Contaminant Level for radium or radon 

in drinking water. Although radioactive elements were more 

frequently detected in 2008 than in 2000, this increased detection frequency is more likely due to lower detection levels in 

2008 than 2000.

The average age of groundwater entering the screens 

of the production wells sampled in 2008 ranged from 6 

to 35 years, with a median groundwater age of 22 years. 

Groundwater age was positively correlated with well depth 

and negatively correlated with dissolved oxygen. Data from 

the 22 resampled wells indicate a significant positive difference in the average modeled groundwater-sample-age results. 

The average groundwater age from samples collected in 2008 

was generally 7 years older than the average groundwater age 

from samples collected in 2000.

Introduction

The Columbia aquifer is an important drinking-water 

resource in the Coastal Plain of Delaware (Ferrari, 2002). 

A significant number of public drinking-water supply wells 

are screened in the Columbia aquifer. The Columbia aquifer 

consists primarily of sands and gravels of fluvial and marginal 

marine origin. Since it is largely unconfined, it is susceptible 

to contamination from applications or spills of chemicals on or 

near the land surface. The primary land uses surrounding these 

relatively shallow public-supply wells in the Coastal Plain of 

Delaware include agriculture, and low-density urban and suburban areas associated with small towns and communities.

A previous study of the Columbia aquifer in 2000 found 

that low concentrations of pesticides and volatile organic 

compounds (VOCs) were present in the source water for 30 

randomly selected drinking-water wells throughout Delaware 

(Ferrari, 2002). Although concentrations of organic compounds were generally low (less than 1 μg/L/microgram 

per liter), at least one compound was detected in all water 

samples, and most samples had multiple detections. None 

of the organic compound concentrations were above the 

U.S. Environmental Protection Agency (USEPA) Federal 

drinking-water standards for Primary or Secondary Maximum 

Contaminant Levels (MCLs) or Health Advisory Levels 

(HALs). In addition, the median concentration of nitrate in 

water samples was about half (5.20 mg/L/milligrams per liter) 

of the Federal drinking-water standard for nitrate as nitrogen 

(10 mg/L). This concentration is significantly greater than 

the background concentration of nitrate in groundwater in the 

Delmarva Peninsula, which was estimated to be less than 0.4 

mg/L (Hamilton and others, 1993). These results show that 

human effects on land use have impacted the quality of this 

important drinking-water resource. 

State regulatory officials and water-resource managers 

are concerned with the overall quality of the drinking-water 

resource, and are interested in determining if there have been 

any broad changes in the characteristics of source waters 

since the initial sampling in 2000. This project was undertaken to allow for a direct comparison of chemical-quality 

results between samples collected in 2000 and 2008. These 

results will further supplement the public-well database for 

the State of Delaware, and provide information on the changes 

in concentration and distribution of chemical compounds that 

will assist officials responsible for implementing practices for 

protecting drinking-water resources in Delaware. 

Purpose and Scope

The primary objectives of this report are to describe the 

occurrence and distribution of selected contaminants and to 

document any changes in groundwater quality in the Columbia 

aquifer public-supply wells in the Coastal Plain in Delaware 

between 2000 and 2008. Samples were collected from August 

through November of 2008. The same well network sampled 

in 2000 by Ferrari (2002) was resampled for this study to the 

extent possible. Of the original 30 wells, 22 were available 

for resampling and the remaining 8 wells were replaced with 

similar nearby wells.

All wells were sampled for the same suite of constituents 

that were sampled in 2000. As such, groundwater samples 

were collected and analyzed for pesticides, pesticide degradation products, VOCs, nutrients, major ions, and trace elements. 

Groundwater age was determined for each sample. A subset 

of nine wells was analyzed for radon and radium. Constituent 

concentrations were compared to the USEPA MCLs 

(U.S. Environmental Protection Agency, 2009), the Health 

Advisory Limits (HALs) set by the Delaware Division 

of Public Health (State of Delaware, 2002) and the U.S. 

Geological Survey (USGS) Health-Based Screening Levels 

(HBSLs) (Toccalino and others, 2004; Toccalino and others, 

2008), where available. These comparisons were made for 

informational purposes and not for evidence of compliance or 

non-compliance with Federal regulations because these standards and guidelines are for public drinking water as supplied 

to customers and are not applied to raw water. Complete tables 

of analytical results for 2008 are included as appendixes B to 

G at the end of the report.

This study is part of the Source Water Assessment and 

Protection Program (SWAPP), which was created by Congress 

as part of the Safe Drinking-Water Act Amendments of 1996. 

The goal of the SWAPP is to better protect public-drinking 

water resources by providing local and State governments and 

the public with more information about these resources. The 

susceptibility of sources of public drinking water to various 

types of contamination was also determined and described.
Methods of Study 3

Description of Study Area

The study area lies entirely within the Atlantic Coastal 

Plain Physiographic Province in Delaware (fig. 1a). This area 

is underlain by a seaward-dipping wedge of unconsolidated 

gravels, sands, silts, and clays that form a series of confined 

aquifers and confining beds overlain by a regional unconfined 

aquifer system that is referred to as the Columbia aquifer 

in Delaware (Benson and others, 1986). This study focuses 

on the Columbia aquifer, which is generally unconfined and 

consists of near-surface water-yielding sediments (Bachman, 

1984; Bachman and Wilson, 1984; Andres, 1991, 1994; Talley, 

1988). The aquifer, which ranges from 20 ft (feet) to over 

100 ft in thickness, consists primarily of sands that occur as 

channel-fill deposits in the northern part of the study area 

and spread into sheet sands in Kent and Sussex Counties 

(Johnston, 1973). The aquifer’s hydrologic characteristics and 

presence at the land surface render it particularly susceptible 

to contamination. 

Land use is predominantly agricultural throughout 

Delaware, and the major crops are corn, soybeans, and small 

grains (U.S. Department of Agriculture, 1997; Denver, Ator, 

and Brayton, 2004). In 1997, approximately, 45 percent of 

Delaware’s total available land area was used for farming 

(Blaier and Baxter, 2000). Most agricultural activity 

takes place in Kent and Sussex Counties and south of the 

Chesapeake and Delaware (C&D) Canal in New Castle 

County. 

The Columbia aquifer is the primary source of water for 

domestic and agricultural use in Delaware, and an important 

source of public water supply (Denver and others, 2004). The 

aquifer is a source of recharge to underlying confined aquifers 

and the predominant source of base flow to streams (Debrewer 

and others, 2007).

Methods of Study

This study was designed to identify and quantify spatial 

and temporal changes in the groundwater quality in the 

Columbia aquifer in Delaware used for public drinking-water 

supply between 2000 and 2008. Groundwater was sampled for 

the same set of compounds in 22 original and 8 replacement 

wells. 

Sampling Network

USGS personnel visited each site to determine if the 

original 30 wells were still suitable for sampling (See Ferrari, 

2002 for additional information on the original well-network 

design). During this process, it was discovered that eight wells 

were no longer in use for a variety of reasons. The selection 

of replacement wells to complete the 30-well network was 

made by Delaware Department of Natural Resources and 

Environmental Control (DNREC) personnel on the basis of the 

following established criteria: located close to the original well 

(generally within 1 mile) with similar well construction, used 

as a public drinking-water supply, and screened in the unconfined aquifer (fig. 1b). A summary of the well-construction 

data, and modeled groundwater ages of groundwater samples 

is listed in table 1.

Samples from nine wells were analyzed for radium-226, 

radium-228, and radon-222. After reconnaissance, six of the 

original wells were determined to be suitable for resampling, 

and four wells needed to be replaced. One of the replacement 

wells could not be sampled due to scheduling problems.

Sample Collection and Analysis

All wells were sampled and analyzed for the same suite 

of organic contaminants and nutrients as in 2000. Water 

temperature, specific conductance, pH, dissolved oxygen, and 

alkalinity were determined in the field following the protocols 

outlined in Wilde and others (2005). All groundwater samples 

were collected from the raw-sample tap prior to any filtering 

or treatment, and are therefore representative of the available 

groundwater resource rather than drinking water. Wells were 

purged to remove standing water in the casing (generally three 

well volumes) before samples were collected. Purging continued until dissolved oxygen (±0.3 mg/L), pH (±0.1 units), 

specific conductance (±3 percent), water temperature (±0.2°C/

degrees Celsius), and turbidity (±10 percent) stabilized. Waterquality samples were collected through Teflon tubing inside a 

sampling chamber. A subset of samples intended for dissolved 

analyses was passed through a 0.45-μm (micrometer) capsule 

filter (for inorganic constituents) or a 0.7-μm baked-glass fiber 

filter (for pesticides and pesticide degradates); selected trace 

elements and major-ion samples were preserved with nitric 

acid to a pH below 2. Bottles were chilled to maintain a temperature of 4°C during shipment to the laboratory.

 Samples were analyzed for 48 pesticides and 35 pesticide degradates, 86 VOCs, nutrients (nitrogen and phosphorus), major ions, trace elements, dissolved organic carbon, age 

dating, and selected radioactive elements (radium-226 and 

radium-228, radon-222).

 The majority of the analytical work (concentrations of 

inorganic ions, trace elements, selected pesticides and pesticide degradates, nutrients, and radon-222) for this study was 

performed at the USGS National Water Quality Laboratory 

(NWQL) in Denver, Colorado, using established procedures 

(Fishman, 1993; Zaugg and others, 1995; Connor and others, 

1998). Additional analyses for pesticide degradates were 

performed at the USGS Organic Geochemistry Research 

Laboratory in Lawrence, Kansas (Zimmerman, and others, 

2000; Lee and others, 2001). To determine groundwater 

age, concentrations of gaseous sulfur hexafluoride (SF6) 

were determined at the USGS National Research Program 

Chlorofluorocarbon/Dissolved Gas Laboratory in Reston, 

Virginia (Plummer and Busenberg, 1999; Plummer and 
4 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Figure 1a. Land use in the Atlantic Coastal Plain study area 

of Delaware.

Figure 1b. Locations of public water-supply wells sampled 

in 2008 in the Columbia aquifer in Delaware and comparison 

of pesticide and degradate detection frequencies in 

groundwater, 2000 and 2008.
Methods of Study 5

Friedman, 1999; Plummer and Busenberg, 2000; Busenberg 

and others, 2001). Radiochemical activities (radium-226 

and -228) for the groundwater samples were performed 

at the Eberline Analytical Corporation Laboratory in 

Richmond, California following USEPA method 903.1 (U.S. 

Environmental Protection Agency, 1980a) and USEPA modified method 904.0 (U.S. Environmental Protection Agency, 

1980b), respectively. 

Data Analysis

Explanatory and nonparametric statistical tests were used 

to characterize water chemistry differences between sampling 

events in 2000 and 2008, to identify changes in groundwater 

quality from individual wells, and to identify patterns in 

groundwater chemistry during the 8-year study period in the 

Columbia aquifer. Correlation among continuous variables 

was evaluated through the use of scatter plots and correlation 

(Spearman’s rho) matrices (Helsel and Hirsch, 1992; Conover, 

1999). Plots of cumulative distribution frequency (CDF) of 

selected chemicals were used to view differences in the distribution of data between the two sampling periods. Wilcoxon 

Signed-Rank-Sum tests were used to determine if median 

concentrations were significantly different between time 

periods, and x-y plots of specific chemicals and factors such 

as groundwater age or well depth were prepared (Helsel and 

Hirsch, 1992). Twenty-two of the original wells were available 

for resampling and used for comparison between the 2000 and 

2008 samples. Where laboratory reporting levels had changed 

since the initial samples were collected, data were censored to 

a common detection level for each compound (several compounds had multiple laboratory reporting levels) and censored 

data (less than the reporting limit) were set to zero before any 

analyses or ranks. All statistical tests were evaluated at the 

95-percent confidence level (α=0.05). Statistical analyses were 

performed using Statistical Analysis Software (SAS), version 

9.1.2 (SAS Institute Inc., SAS 9.1.2, 2004).

Quality-Control Sampling 

Field blanks, sequential replicate samples, and spikes 

were collected following the protocols described in Koterba 

and others (1995) to determine uncertainty and variability. The 

number of samples collected for quality control was based 

on results and criteria reported in the previous study (Ferrari, 

2002). Nineteen quality-control samples were collected: 10 

replicates, 7 field blanks, and 2 laboratory spikes. Not all 

chemical constituents were analyzed in each quality-control 

sample, but as in 2000, particular suites of chemicals were 

targeted. The quality-control data are presented in Appendixes 

Ha through Hf. 

Field blanks were collected to estimate the accuracy 

of concentrations and to ensure that sample collection and 

processing did not result in contamination. No nutrients, 

major ions, pesticides, or pesticide degradate compounds were 

detected in field blanks at concentrations exceeding laboratory 

reporting levels. Results of concentrations from VOC blanks 

were higher than their respective environmental sample results 

for a small group of compounds. All of these samples had 

concentrations estimated to be lower than their reporting limits 

or below detection limits, however. Field blanks indicated that 

reported concentrations of VOCs may contain minimal bias 

due to contamination during sample collection, processing, or 

shipment.

Replicate field samples measure the combined precision 

of sampling and laboratory analysis procedures. Most of the 

replicate samples had results similar to or consistent with their 

respective environmental samples. Six constituent replicates 

were the exception: metolachlor, alachlor ethanesulfonic acid 

second amide (alachlor ESA SA), total ammonia plus organic 

nitrogen, magnesium, iron, and radium-226. For each of these 

constituents, one of the samples had a reported concentration 

estimated to be lower than the reporting limit, whereas the 

associated environmental or replicate sample did not have a 

detectable concentration. These replicates are considered to 

be consistent because the reported concentrations were lower 

than the non-detection reporting levels.

Spikes were analyzed to determine the extent of degradation of the analyte concentration during sample processing and 

analysis, recovery bias, and variability (Koterba and others, 

1995). In this study, samples were spiked in the laboratory 

with a known quantity of pesticides. Spike data are available 

upon request from the USGS Maryland-Delaware-D.C. Water 

Science Center in Baltimore, Maryland. 

Age Dating

Average age dates for groundwater samples were 

estimated on the basis of measured concentrations of SF6

(Busenberg and Plummer, 2000; Plummer and Friedman, 

1999) (table 1, Appendix Ga). SF6 is a colorless, odorless

stable gas primarily of anthropogenic origin with a small concentration from natural sources. The SF6 method can be used 

to date groundwater that is in equilibrium with atmospheric 

SF6 during recharge and is not subsequently exposed to significant SF6 from other sources. Dissolved-gas analyses also were 

performed on samples of each well as part of the age-dating 

analysis to determine the average recharge temperature of the 

water in the aquifer (Appendix Gb). Wells were screened over 

several feet of aquifer sediment; therefore, the recharge date 

represents the average age of water withdrawn from the well. 

The reported age was calculated by averaging the SF6 ages 

estimated from each of two samples collected from each well. 

Water-quality data described in this report were collected 

from 30 public-supply wells sampled during August through 

November 2008. These data were compared to data from previous sampling conducted in 2000 (Ferrari, 2002) to analyze 

differences in samples from the 22 wells sampled during both 

periods. Results were grouped according to the type of chemicals and include: pesticides and degradate compounds, VOCs, 

nutrients, major ions and trace elements, radium and radon, 

and age-dating data. Complete data tables for the current study 

are provided in Appendixes A through F. 
6 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08 Table 1. Well-construction data for sampled public water-supply wells screened in the Columbia aquifer in Delaware during 2000 and 2008, and modeled ages of groundwater sampled in 2008.—Continued [USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; DNREC, Delaware Department of Natural Resources and Environmental Control; Resampled, 22 public water-supply wells sampled in 2000 and 2008; --, replaced by, public water-supply wells sampled only in 2000, not active in 2008; Replacement, 8 public water-supply wells sampled only in 2008] Site number USGS site identification number DGS local well number Well network DNREC permit number County Year well constructed Casing material Depth of well (feet) Diameter of well (inches) Depth to top of screen (feet) Depth to bottom of screen (feet) Average age in 2008 (years)

1 382805075330301 Rd22-01 Resampled 66041 Sussex 1986 Plastic 60 2 52 60 25.52 382830075073601 Ri23-04 Resampled 106344 Sussex 1995 Plastic 82 6 70 80 23.73 383000075326001 Qd52-09 Resampled 78054 Sussex 1989 Plastic 70 4 60 70 20.54 383101075141101 Frankford4 Resampled 10342 Sussex 1934 Unknown 85 8 69 81 29.25 383311075344401 Qd21-12 Resampled 35239 Sussex 1975 Steel 100 12 70 100 22.7

-- 383649075090801 Pot Nets #1 Replaced by Pi32-15 10651 Sussex 1972 Unknown Unknown 6 Unknown 85 24.5-- 383705075192801 Forest Hills Replaced by Pg31-12 10700 Sussex 1975 Unknown 110 4 Unknown 110 Unknown

6 383713075085501 Pi32-15 Replacement 10653 Sussex 1972 Unknown 90 6 75 85 21.87 383729075101601 Ph35-25 Replacement 63104 Sussex 1986 Unknown 58 8 58 73 21.38 383732075191301 Pg31-12 Replacement 35113 Sussex 1975 Plastic 73 12 53 73 16.1

-- 383736075092801 Pi31-02(pn5) Replaced by Ph35-25 49713 Sussex 1986 Steel 70 8 55 70 15.5-- 383801075375701 Pc33-44 Replaced by Pc22-06 10369 Sussex 1988 Unknown Unknown 12 82 97 12.5

9 383815075271001 Pe23-185 Resampled 72060 Sussex 1987 Plastic 120 4 100 110 34.6

10 383823075382101 Pc22-06 Replacement 74465 Sussex 1988 Steel 103 16 63 103 19.5

11 383914075080501 Pi12-11 Replacement 75500 Sussex 1988 Plastic 68 4 58 68 18.1

-- 383947075083401 Pi12-08 Replaced by Pi12-11 32247 Sussex 1974 Plastic 55 4 45 55 12.0

12 384139075230101 Of42-01 Resampled 10325 Sussex 1948 Unknown 120 6 Unknown 120 26.713 384322075051101 Oi25-18 Resampled 93955 Sussex 1993 Plastic 38 4 23 38 8.014 384326075050801 Oi25-19 Resampled 93496 Sussex 1992 Unknown 37 4 27 37 14.715 384428075135501 Oh12-07 Replacement 181528 Sussex 2001 Plastic 118 4 108 118 22.416 384428075355701 Oc15-11 Resampled 10319 Sussex 1955 Unknown 119 12 100 119 25.017 384526075091601 Ni51-32 Resampled 55833 Sussex 1984 Plastic 139 16 85 135 27.1

-- 384530075121101 Nh53-01 Replaced by Oh12-07 30657 Sussex 2001 Steel 110 4 100 110 17.0

18 384818075354101 Nc25-37 Resampled 72714 Sussex 1988 Steel 63 12 40 63 18.119 384819075190101 Ng21-03 Resampled 71704 Sussex 1987 Plastic 111 4 91 111 25.220 384856075151101 Ng25-04 Resampled 97993 Sussex 1994 Plastic 139 8 99 139 33.721 385448075341801 Md11-04 Resampled 65911 Kent 1986 Unknown 70 10 50 70 21.722 385522075251802 Le55-09 Resampled 31756 Kent 1974 Steel 91 10 71 91 23.9
Methods of Study 

7

Table 1. Well-construction data for sampled public water-supply wells screened in the Columbia aquifer in Delaware during 2000 and 2008, and modeled ages of groundwater sampled in 2008.—Continued[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; DNREC, Delaware Department of Natural Resources and Environmental Control; Resampled, 22 public water-supply wells sampled in 2000 and 2008; --, replaced by, public water-supply wells sampled only in 2000, not active in 2008; Replacement, 8 public water-supply wells sampled only in 2008]

Site 

number

USGS site 

identification 

number

DGS local 

well

number

Well 

network

DNREC 

permit 

number

County

Year 

well 

constructed

Casing 

material

Depth of 

well

(feet)

Diameter 

of well 

(inches)

Depth 

to top of 

screen 

(feet)

Depth to 

bottom 

of screen 

(feet)

Average 

age in 

2008 

(years)

23 390617075261901 Je55-01 Replacement 85416 Kent 1991 Plastic 65 4 55 65 Unknown

-- 390619075290901 Je41-08 Replaced by Je55-01 10735 Kent 1955 Unknown 40 4 Unknown 40 9.5

24 390652075370701 Jc43-05 Resampled 82964 Kent 1990 Plastic 70 4 60 70 18.425 391060075282801 Ie42-03 Resampled 85022 Kent 1991 Steel 70 16 49 64 16.426 391747075364202 Hc34-03 Resampled 10068 Kent 1948 Steel 100 16 80 95 18.027 393739075394202 Dc31-15 Resampled 10434 New Castle 1960 Unknown 76 17 50 70 7.628 393916075440802 Db11-28 Resampled 10003 New Castle 1956 Unknown 62 10 31 62 5.829 393928075440202 Db11-27 Resampled 10004 New Castle 1956 Steel 66 10 41 62 7.3

-- 394060075334601 Cd52-15 Replaced by Cd42-18 10045 New Castle 1960 Steel 74 17 50 73 6.0

30 394102075334301 Cd42-18 Replacement 10046 New Castle 1958 Unknown 104 17 56 104 Unknown
8 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Pesticides and Pesticide Degradates

A variety of pesticides and pesticide degradates were 

detected in groundwater samples from the Columbia aquifer in 

the Coastal Plain in Delaware, although concentrations were 

typically less than 1 μg/L. Of the more than 80 pesticides and 

degradate compounds (48 and 35, respectively) for which 

samples were analyzed, 24 (14 pesticides and 10 degradates) 

were detected at least once (table 2, fig. 1b). No samples 

contained concentrations above the Federal drinking-water 

standards or MCLs, however, standards currently exist for 

only 5 of the 14 pesticide compounds detected (table 3) (U.S. 

Environmental Protection Agency, 2009). None of the degradate compounds have established criteria or guidelines (U.S. 

Environmental Protection Agency, 2009; Toccalino and others, 

2004). Several additional pesticides and pesticide degradates 

were analyzed in the 2008 samples that were not included in 

the 2000 analyses (table 2). 

The pesticides that were most frequently detected above 

the reporting limits in groundwater were herbicides typically used for local agricultural applications and their degradates (fig. 2). Atrazine and metolachlor, the most commonly 

detected parent compounds, were detected in more than 40 

percent of the samples. The pesticide degradates metolachlor 

ESA, deethylatrazine, and alachlor ESA were detected in more 

than half of the samples. The ESA and oxanilic acid (OA) degradates of metolachlor and alachlor are more soluble than their 

respective parent compounds and move readily in groundwater 

with little additional degradation (Phillips and others, 1999). 

Debrewer and others (2007) found that in groundwater from 

the Delmarva Peninsula, pesticide degradates were detected 

more frequently and generally at higher concentrations (at 

least one order of magnitude higher) than their parent compounds, metolachlor, atrazine, and alachlor, respectively (table 

3). Herbicides commonly used for non-agricultural purposes 

and insecticides were detected much less frequently than 

Table 2. Pesticides and pesticide degradates for which groundwater samples from public water-supply wells were analyzed in the 

Columbia aquifer in Delaware, 2000 and 2008.

[Compounds detected in 2008 are in bold; pesticide degradates are listed in italics; **, compounds not measured in 2000; ESA, ethanesulfonic acid; 

OA, oxanilic acid; SA, second amide]

2,6-Diethylaniline Chlorpyrifos Fipronil sulfone**1 Parathion

2-[(2-Ethyl-6-methylphenyl)amino]-2-oxoESA**1 Cyanazine Flufenacet Parathion methyl

Acetochlor DCPA (Clorthal-dimethyl) Flufenacet ESA Pebulate2

Acetochlor ESA Dechloroacetochlor Flufenacet OA Pendimethalin

Acetochlor OA Dechloroalachlor Fonofos cis-Permethrin

Acetochlor SA Dechlorodimethenyl amide Glufosinate Phorate

Acetochlor SAA Dechlorometolachlor Glyphosate Prometon2

Alachlor2 Deethylatrazine (CIAT)2 Hydroxyacetochlor Propachlor ESA

Alachlor ESA2 Desulfinylfipronil amide Hydroxyalachlor Propachlor OA

Alachlor ESA SA**1 Desulfinylfipronil Hydroxydimethenamid Propachlor 

Alachlor OA2 Diazinon Hydroxymetolachlor Propanil

Alachlor SA Dieldrin2 Lindane2 Propargite

Alachlor SAA Dimethenamid Linuron Propyzamide

alpha-HCH1 Dimethenamid ESA Malathion Simazine2

Aminomethylphosphonic acid**1 Dimethenamid OA Metolachlor2 Tebuthiuron2

Atrazine2 Disulfoton Metolachlor ESA2 Terbacil

Azinphos-methyl EPTC (Eptam)2 Metolachlor OA2 Terbufos

Benfluralin Ethalfluralin Metribuzin Thiobencarb

Butylate2 Ethoprop Molinate Triallate

Carbaryl3 Fipronil**1 Napropamide Trifluralin

Carbofuran2 Fipronil sulfide**1 p,p’-DDE3

1

 Detected only in 2008.

2

 Detected in 2008 and 2000.

3

 Detected only in 2000.
Methods of Study 9

Table 3. Summary statistics for pesticides and pesticide degradates detected in groundwater samples from public watersupply wells screened in the Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum 

Contaminant Levels and Health-Based Sceening Levels in 2000 and 2008.—Continued

[**, compounds not measured in 2000; pesticide degradates are in italics; LTMDL, long-term method detection limit; MRL, method reporting level; E, value 

is greater than the LTMDL but less than MRL and is coded as estimated because of lower precision in this value; <, less than; ≥, greater than or equal to; nd, 

no data; ESA, ethanesulfonic acid; OA, oxanilic acid; SA, second amide; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 public 

water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; --, no standard or 

guideline established; μg/L, micrograms per liter; number of detections in bold are detections above the MCL or (HBSL), where established]

Compound Network Number of 

detections

Minumum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

Number of 

detections 

≥0.1 μg/L

MCL1

or

(HBSL2,3)

Agricultural herbicides

Metolachlor Total (2000) 19 E0.001 0.009 0.185 3 (700)

Total (2008) 13 E0.003 <0.012 0.087 0 (700)

Resampled (2000) 14 E0.001 0.008 0.185 3 (700)

Resampled (2008) 12 E0.003 <0.01 0.087 0 (700)

Metolachlor ESA Total (2000) 20 <0.05 0.23 2.92 18 --

Total (2008) 24 <0.02 0.195 3.95 18 --

Resampled (2000) 16 <0.05 0.23 2.92 14 --

Resampled (2008) 18 <0.02 0.22 3.21 16 --

Metolachlor OA Total (2000) 9 <0.05 <0.05 0.7 5 --

Total (2008) 14 <0.02 <0.02 0.98 9 --

Resampled (2000) 9 <0.05 <0.05 0.7 5 --

Resampled (2008) 11 <0.02 <0.02 0.98 7 --

Atrazine Total (2000) 15 <0.001 <0.007 0.862 4 3

Total (2008) 14 E0.005 <0.007 0.488 2 3

Resampled (2000) 11 <0.001 <0.001 0.862 4 3

Resampled (2008) 11 E0.005 <0.007 0.488 2 3

Deethylatrazine (CIAT) Total (2000) 21 <0.002 E0.013 E0.455 4 --

Total (2008) 23 E0.002 <0.014 E0.195 3 --

Resampled (2000) 15 <0.002 E0.014 E0.455 4 --

Resampled (2008) 17 E0.002 <0.014 E0.195 3 --

Alachlor Total (2000) 7 E0.006 <0.006 0.055 0 2

Total (2008) 6 <0.002 <0.002 0.054 0 2

Resampled (2000) 4 <0.002 <0.002 0.054 0 2

Resampled (2008) 5 E0.006 <0.006 0.055 0 2

Alachlor ESA Total (2000) 20 <0.05 0.11 1.6 17 --

Total (2008) 21 <0.02 0.14 2.11 17 --

Resampled (2000) 15 <0.05 0.17 1.6 13 --

Resampled (2008) 17 <0.02 0.17 2.09 14 --

Alachlor OA Total (2000) 2 <0.05 <0.05 0.28 2 --

Total (2008) 11 <0.02 <0.02 0.2 3 --

Resampled (2000) 2 <0.05 <0.05 0.28 2 --

Resampled (2008) 9 <0.02 <0.02 0.2 3 --
10 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Table 3. Summary statistics for pesticides and pesticide degradates detected in groundwater samples from public watersupply wells screened in the Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum 

Contaminant Levels and Health-Based Sceening Levels in 2000 and 2008.—Continued

[**, compounds not measured in 2000; pesticide degradates are in italics; LTMDL, long-term method detection limit; MRL, method reporting level; E, value 

is greater than the LTMDL but less than MRL and is coded as estimated because of lower precision in this value; <, less than; ≥, greater than or equal to; nd, 

no data; ESA, ethanesulfonic acid; OA, oxanilic acid; SA, second amide; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 public 

water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; --, no standard or 

guideline established; μg/L, micrograms per liter; number of detections in bold are detections above the MCL or (HBSL), where established]

Compound Network Number of 

detections

Minumum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

Number of 

detections 

≥0.1 μg/L

MCL1

or

(HBSL2,3)

Alachlor ESA SA** Total (2000) nd nd nd nd nd --

Total (2008) 4 0.02 <0.02 0.04 0 --

Resampled (2000) nd nd nd nd nd --

Resampled (2008) 3 0.02 <0.02 0.04 0 --

2-[(2-Ethyl-6-methylphenyl)

amino]-2-oxoESA**

Total (2000) nd nd nd nd nd --

Total (2008) 8 0.02 <0.02 0.39 1 --

Resampled (2000) nd nd nd nd nd --

Resampled (2008) 8 0.02 <0.02 0.39 1 --

Fipronil** Total (2000) nd nd nd nd nd --

Total (2008) 7 E0.003 <0.02 <0.04 0 --

Resampled (2000) nd nd nd nd nd --

Resampled (2008) 6 E0.003 <0.02 <0.04 0 --

Fipronil sulfide** Total (2000) nd nd nd nd nd --

Total (2008) 1 E0.003 <0.013 <0.013 0 --

Resampled (2000) nd nd nd nd nd --

Resampled (2008) 1 E0.003 <0.013 <0.013 0 --

Fipronil sulfone** Total (2000) nd nd nd nd nd --

Total (2008) 4 E0.002 <0.024 <0.024 0 --

Resampled (2000) nd nd nd nd nd --

Resampled (2008) 3 E0.002 <0.024 <0.024 0 --

Aminomethylphosphonic acid** Total (2000) nd nd- nd nd nd --

Total (2008) 4 <0.02 <0.02 0.28 1 --

Resampled (2000) nd nd nd nd nd --

Resampled (2008) 2 <0.02 <0.02 0.28 1 --

Lindane Total (2000) 3 E0.002 <0.004 0.009 0 0.2

Total (2008) 1 E0.006 <0.006 <0.014 0 0.2

Resampled (2000) 3 E0.002 <0.004 0.009 0 0.2

Resampled (2008) 1 E0.006 <0.006 <0.014 0 0.2

Butylate Total (2000) 1 <0.002 <0.002 0.01 0 (400)

Total (2008) 1 <0.002 <0.002 0.002 0 (400)

Resampled (2000) 1 <0.002 <0.002 0.01 0 (400)

Resampled (2008) 1 <0.002 <0.002 0.002 0 (400)
Methods of Study 11

Table 3. Summary statistics for pesticides and pesticide degradates detected in groundwater samples from public watersupply wells screened in the Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum 

Contaminant Levels and Health-Based Sceening Levels in 2000 and 2008.—Continued

[**, compounds not measured in 2000; pesticide degradates are in italics; LTMDL, long-term method detection limit; MRL, method reporting level; E, value 

is greater than the LTMDL but less than MRL and is coded as estimated because of lower precision in this value; <, less than; ≥, greater than or equal to; nd, 

no data; ESA, ethanesulfonic acid; OA, oxanilic acid; SA, second amide; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 public 

water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; --, no standard or 

guideline established; μg/L, micrograms per liter; number of detections in bold are detections above the MCL or (HBSL), where established]

Compound Network Number of 

detections

Minumum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

Number of 

detections 

≥0.1 μg/L

MCL1

or

(HBSL2,3)

Alpha HCH** Total (2000) nd nd nd nd nd (0.006-0.6)

Total (2008) 1 <0.002 <0.002 <0.008 0 (0.006-0.6)

Resampled (2000) nd nd nd nd nd (0.006-0.6)

Resampled (2008) 1 <0.002 <0.002 <0.008 0 (0.006-0.6)

EPTC (Eptam) Total (2000) 1 <0.002 <0.002 0.018 0 (200)

Total (2008) 1 <0.002 <0.002 0.009 0 (200)

Resampled (2000) 1 <0.002 <0.002 0.018 0 (200)

Resampled (2008) 1 <0.002 <0.002 0.009 0 (200)

Pebulate Total (2000) 1 <0.002 <0.004 0.004 0 (50)

Total (2008) 1 <0.004 <0.004 <0.016 0 (50)

Resampled (2000) 1 <0.002 <0.004 0.004 0 (50)

Resampled (2008) 1 <0.004 <0.004 <0.016 0 (50)

Urban herbicides

Simazine Total (2000) 9 E0.004 <0.005 0.019 0 4

Total (2008) 8 E0.004 <0.006 0.032 0 4

Resampled (2000) 7 E0.004 <0.005 0.019 0 4

Resampled (2008) 6 E0.004 <0.006 0.032 0 4

Prometon Total (2000) 10 E0.003 <0.018 0.149 1 (400)

Total (2008) 7 E0.005 0.009 0.049 1 (400)

Resampled (2000) 9 E0.003 <0.018 0.149 1 (400)

Resampled (2008) 6 E0.005 <0.008 0.049 1 (400)

Tebuthiuron Total (2000) 6 E0.007 <0.01 0.039 0 (1,000)

Total (2008) 4 <0.016 <0.016 0.047 0 (1,000)

Resampled (2000) 4 E0.007 <0.01 0.039 0 (1,000)

Resampled (2008) 4 <0.016 <0.016 0.047 0 (1,000)

Insecticides

Dieldrin Total (2000) 9 <0.001 <0.003 0.106 2 (0.002-0.2)

Total (2008) 9 <0.009 <0.009 0.084 0 (0.002-0.2)

Resampled (2000) 7 <0.001 <0.001 0.088 2 (0.002-0.2)

Resampled (2008) 8 <0.009 <0.009 0.084 0 (0.002-0.2)

Carbofuran Total (2000) 6 <0.003 <0.003 E0.17 4 40

Total (2008) 3 E0.017 <0.02 <0.06 0 40

Resampled (2000) 4 <0.003 <0.003 E0.17 3 40

Resampled (2008) 3 E0.017 <0.02 <0.06 0 40
12 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Table 3. Summary statistics for pesticides and pesticide degradates detected in groundwater samples from public watersupply wells screened in the Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum 

Contaminant Levels and Health-Based Sceening Levels in 2000 and 2008.—Continued

[**, compounds not measured in 2000; pesticide degradates are in italics; LTMDL, long-term method detection limit; MRL, method reporting level; E, value 

is greater than the LTMDL but less than MRL and is coded as estimated because of lower precision in this value; <, less than; ≥, greater than or equal to; nd, 

no data; ESA, ethanesulfonic acid; OA, oxanilic acid; SA, second amide; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 public 

water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; --, no standard or 

guideline established; μg/L, micrograms per liter; number of detections in bold are detections above the MCL or (HBSL), where established]

Compound Network Number of 

detections

Minumum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

Number of 

detections 

≥0.1 μg/L

MCL1

or 

(HBSL2,3)

Carbaryl Total (2000)

Total (2008)

Resampled (2000) 

Resampled (2008) 

1

0

1

0

<0.003

<0.06

<0.003

<0.06

<0.003

<0.06

<0.003

<0.06

<0.041

<0.2

<0.041

<0.2

0

0

0

0

(40-4,000)

(40-4,000)

(40-4,000)

(40-4,000)

p,p′-DDE Total (2000)

Total (2008)

1

0

E0.001

<0.003

<0.006

<0.003

<0.006

<0.003

0

0

(0.1-10)

(0.1-10)

1

 U.S. Environmental Protection Agency, 2009.

2

 Toccalino and others, 2004.

3

 Toccalino and others, 2008.

agricultural herbicides. Only the urban herbicides prometon 

and simazine and the insecticide dieldrin were detected in 

more than 15 percent of these samples (fig. 2).

Of the 10 detected compounds for which non-regulatory 

health-based guidelines exist (Toccalino and others, 2004), 1 

pesticide, dieldrin, exceeded the HBSL of 0.002 μg/L in all 9 

samples from urbanized areas. Dieldrin is an insecticide that 

was primarily used for termite control, and its use was banned 

in most of the world, including Delaware, in 1978 

(U.S. Environmental Protection Agency, 2003). It was originally developed in the 1940s as an alternative to DDT, and 

proved to be highly effective; it was very widely used from 

the 1950s to the early 1970s. It is resistant to degradation and 

tends to biomagnify in food webs (U.S. Department of Health 

and Human Services, 2002). Long-term exposure has proven 

toxic to humans and a very wide range of animals. 

The occurrence and distribution of pesticide and pesticide 

degradate compounds and the number of detections in the 

Columbia aquifer in Delaware did not change significantly 

from 2000 to 2008 (figs. 1b and 2). A similar distribution was 

found between numbers of compounds detected in the three 

pesticide groups between 2000 and 2008 (fig. 2). Almost 80 

percent of the detected compounds were agricultural herbicides, such as metolachlor and atrazine, or their respective 

degradates. These chemicals have been used for over 25 years 

in the study area (Debrewer and others, 2007; Denver and 

others, 2004). The predominance of the agricultural herbicides 

among the pesticides detected in groundwater reflects the 

prevalence and wide distribution of agriculture in sampled 

areas (fig. 1b), as well as the dominance of agricultural herbicides among the target analytes (table 2) (Denver and Ator, 

2006). Ferrari (2002) noted the same pattern, where 63 percent 

(12 of 19) of the detected compounds were agricultural herbicides. Debrewer and others (2007) noted that atrazine and 

metolachlor concentrations in groundwater in the Delmarva 

Peninsula increased with an increasing proportion of agriculture near sampled wells. 

Pesticides commonly used in urban areas, such as dieldrin, prometon, simazine, and tebuthiuron, were detected in 

nine wells from mainly urban areas, particularly in the northern part of the study area (fig. 1b). Rapid urban expansion in 

the areas directly north and south of the C&D Canal resulted 

in conversion of much of the remaining agricultural land to 

residential and commercial uses (Blaier and Baxter, 2000) 

(fig. 1b). 

When present, pesticides commonly occur in mixtures in 

groundwater (Denver and Ator, 2006; Ator and Reyes, 2008). 

Mixtures of pesticides and pesticide degradates were found 

in 90 percent of the 30 wells sampled (from 2 to 20 pesticide 

compounds detected per well); two wells had one detection, 

and only one well (Pi12-11), a replacement well, had no 

detections (Appendixes D and E). The prevalence of pesticide 

mixtures in groundwater reflects similar patterns in usage; 

multiple compounds are often applied to the same area, often 

in mixed formulations, for greater pest control. In addition, 

many pesticides have similar chemical properties that control 

their fate and movement in the environment (Denver and 

Ator, 2006). The wells with one or no detectable pesticides 

are located either in predominantly forested areas, areas with 

poorly drained soils, or areas with highly organic soils that can 

limit (tend to adsorb) pesticide movement to groundwater.
Methods of Study 13

Figure 2. Pesticides and pesticide degradates in groundwater samples from public water-supply 

wells screened in the Columbia aquifer in Delaware, 2000 and 2008.
14 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

The widespread detection and distribution of pesticide 

compounds during 2000 and 2008 reflects their abundant use 

in Delaware, and is indicative of their chemical properties 

such as moderate to high water solubility and persistence. 

Aquifer characteristics, such as good soil drainage and sandy 

aquifer sediments, promote the movement of pesticides 

into groundwater (Debrewer and others, 2007). The relative 

magnitude of concentrations of selected degradates and parent compounds in Columbia aquifer groundwater reflects the 

fact that most pesticide degradation occurs in the soil zone, 

before infiltration reaches the water table (Barbash and Resek, 

1996). Excluding metolachlor and lindane, the number of 

pesticides or degradate compounds detected per well increased 

or remained the same over the study period in more than 75 

percent of the samples from the 22 resampled wells. A slight 

decrease in the number of pesticide or degradate detections 

occurred in four wells, and one well had the same number of 

detections as in 2000 (fig. 1b). 

Groundwater responds more slowly than streams to 

changes in pesticide use—taking years and even decades for 

changes in quality to occur (Gilliom and others, 2006). A 

persistent pesticide or degradate can remain in groundwater 

long after its use has been discontinued or replaced because 

of the slow rates of groundwater flow and the resulting long 

residence time of water and contaminants in groundwater flow 

systems. This is evident from a number of studies in different 

parts of the U.S. (Gilliom and others, 2006; Denver and Ator, 

2006). The effect of groundwater residence time on the occurrence of pesticides is further demonstrated by the detection of 

legacy compounds such as dieldrin and alachlor in groundwater (table 3, fig. 2). These pesticides either had their registration cancelled or they were replaced by other compounds 

many years ago, but they are still present nationwide in soils, 

streams, and groundwater (Gilliom and others, 2006). 

Volatile Organic Compounds 

In 2008, 29 of 30 wells had 1 or more VOCs detected; 

3 wells had 10 VOCs detected (fig. 3). Out of the 85 VOCs 

analyzed in this study, 31 different VOCs were detected in 

at least one well (table 4). VOCs were divided into seven 

groups on the basis of common usage (Zogorski and others, 

2006): Trihalomethanes (THMs; common by-products of 

water chlorination), solvents, gasoline oxygenates, gasoline 

hydrocarbons, refrigerants, fumigants, and organic synthesis 

compounds (compounds used in the formation of other organic 

compounds) (fig. 4). Chloroform, one of the THMs, was the 

most frequently detected VOC compound (90 percent of 

samples) and its source is attributed, in part, to the recycling 

of chlorinated waters to aquifers (Zogorski and others, 2006). 

The gasoline oxygenate methyl tert-butyl ether (MTBE) was 

the second most frequently detected VOC, in more than 60 

percent of the samples. The solvents tetrachloroethene (or perchloroethene/PCE) and trichloroethylene (TCE) were the third 

and fourth most frequently detected VOCs, and were found 

in more than 35 and 25 percent of the samples, respectively. 

Zogorski and others (2006) also detected the same VOCs most 

frequently during their study of the Nation’s groundwater and 

drinking water. 

None of the VOC detections were above Federal 

drinking-water standards, although only 16 out of the 85 

VOCs have established MCLs (table 5) (U.S. Environmental 

Protection Agency, 2009). Concentrations of eight detected 

VOC compounds that have non-regulatory health-based guidelines were all below levels of concern (Toccalino and others, 

2004). 

Overall, the concentrations of each VOC and the total 

concentration of all VOCs in a group were less than 1 μg/L. 

Solvents and THMs were the most common groups of compounds detected. Detection frequency of VOCs in groundwater is an important indicator of water quality in occurrence 

assessments (Zogorski and others, 2006). In order to compare 

detection frequencies for individual VOCs, groups of VOCs, 

or VOC data from different agencies with different reporting 

levels, Zogorski and others (2006) applied an assessment level 

of 0.2 μg/L, which was used in a similar manner in this report. 

An assessment level is a fixed concentration used as the basis 

for computing detection frequencies. Out of the 30 samples, 

23 contained one or more VOCs at 0.2 μg/L or greater concentrations. Less than half, about 45 percent, of all VOCs 

detected (117 = total number of detections, see table 5) had 

concentrations above 0.2 μg/L. At the same assessment level 

and within each VOC group, MTBE and chloroform were the 

most frequently detected compounds above 0.2 μg/L. From 

the gasoline oxygenate detections (25), MTBE accounted for 

56 percent, and from the THM detections (33), chloroform 

accounted for 36 percent (table 5). 

The detections of specific compounds and the frequency 

of their detection in 2008 were similar to detections in 2000 

(fig. 4; Ferrari, 2002). Solvents were the most frequently 

detected class of compounds, and chloroform, PCE, and 

MTBE, which were detected in 50 percent or more of samples 

in 2000, were the most frequently detected in 2008 as well 

(fig. 4). There were some differences in the compounds 

detected between the two sampling periods (table 5, fig. 4) but 

these differences were only evident in samples from one well.

Although there were no significant differences in VOC 

concentrations between the study periods, the difference in the 

mean number of VOCs detected per well decreased significantly (p<0.002) (fig. 3, inset). The number of VOC detections 

in 2008 decreased in 73 percent of the 22 resampled wells—

from one to eight fewer detections than in 2000. 

VOC contamination in aquifers is complex. VOC occurrence is determined not only by sources but also by natural 

factors or a mix of natural and anthropogenic factors that 

affect the fate and transport of VOCs in aquifers (Zogorski 

and others, 2006). VOCs are groundwater contaminants of 

concern because of very large environmental releases, human 

toxicity, and the tendency for some compounds to persist and 

migrate to drinking-water supply wells (Zogorski and others, 

2006). The finding that one or more VOCs were detected in 
Methods of Study 15

Figure 3. Locations of public water-supply wells sampled in 2008 in the Columbia aquifer in Delaware and 

comparison of volatile organic compound (VOC) detection frequencies in groundwater, 2000 and 2008.
16 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Table 4. Volatile organic compounds for which groundwater samples from public water-supply wells were analyzed in the Columbia 

aquifer in Delaware, 2000 and 2008.

[Compounds detected in 2008 are in bold]

1,1,1-Trichloroethane2 Bromobenzene Isodurene 

1,1,2,2-Tetrachloroethane Bromochloromethane Isopropylbenzene3

1,1,2-Trichloroethane Bromodichloromethane2 m and p-Xylene 

1,1,2-Trichlorotrifluoromethane (CFC-113)3 Bromoethene Methacrylonitrile 

1,1-Dichloroethane2 Bromoform (Tribromomethane)2 Methyl acrylate 

1,1-Dichloroethene2 Bromomethane Methyl ethyl ketone1

1,2,4-Trichlorobenzene1 Butylmethylketone Methyl methacrylate 

1,2-Dibromoethane Carbon disulfide2 Methyl tert-pentyl ether2

1,2-Dichlorobenzene2 Carbon tetrachloride2 Methyl tert-butyl ether (MTBE)2

1,2-Dichloroethane3 Chlorobenzene2 Naphthalene 

1,2-Dichloropropane2 Chloroethane n-butylbenzene 

1,3-Dichlorobenzene1 Chloroform (Trichloromethane)2 n-propylbenzene 

1,4-Dichlorobenzene2 Chloromethane2 o-Xylene 

1,1,1,2-Tetrachloroethane cis-1,3-Dichloropropene p-Isopropyltoluene3

1,1-Dichloropropene cis-1,2-Dichloroethene2 Prehnitene (1,2,3,4-tetramethylbenzene) 

1,2,3-Trichlorobenzene Dibromochloromethane2 sec-butylbenzene2

1,2,3-Trichloropropane Dibromochloropropane Styrene1

1,2,3-Trimethylbenzene Dibromomethane tert-Butylbenzene3

1,2,4-Trimethylbenzene Dichlorodifluoromethane (CFC-12)2 Tetrachloroethene (PCE)2

1,3,5-Trimethylbenzene Dichloromethane2 Tetrahydrofuran2

1,3-Dichloropropane Diethyl ether Trichlorofluoromethane (CFC-11)2

2,2-Dichloropropane Diisopropyl ether2 Toluene2

2-Chlorotoluene Ethyl benzene trans-1,4-Dichloro-2-butene 

2-Ethyltoluene Ethyl methacrylate trans-1,2-Dichloroethene 

3-Chloropropene Ethyl tert-butyl ether3 trans-1,3-Dichloropropene 

4-Chlorotoluene Hexachlorobutadiene Trichloroethene (TCE)2

Acetone3 Hexachloroethane Vinyl chloride 

Acrylonitrile Iodomethane 

Benzene2 Isobutylmethylketone 

1

 Detected only in 2008.

2

 Detected in 2008 and 2000.

3

 Detected only in 2000.
Methods of Study 17

Figure 4. Volatile organic compounds (VOCs) detected in groundwater samples from 

public water-supply wells screened in the Columbia aquifer in Delaware, 2000 and 2008.
18 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Figure 4. Volatile organic compounds (VOCs) detected in groundwater samples from public 

water-supply wells screened in the Columbia aquifer in Delaware, 2000 and 2008.—Continued
Methods of Study 19

Table 5. Summary statistics for volatile organic compounds in groundwater samples from public water-supply wells screened in the 

Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum Contaminant Levels and HealthBased Sceening Levels in 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; ≥, greater than or equal to; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 

public water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; *, MCL set forth by the Delaware Division of Public 

Health; HBSL, Health-Based Screening Level; μg/L, micrograms per liter; --, no standard or guideline established, none detected above the MCL or (HBSL), 

where established]

Compound groups6 Network

Number 

of 

detections

Minimum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

MCL1

or 

(HBSL2,3)

Assessment Level

<0.2 μg/L ≥0.2 μg/L 

Trihalomethanes (THMs)

Chloroform (Trichloromethane) Total (2000) 28 E0.885 0.123 3.846 804

Total (2008) 27 E0.02 0.118 1.126 804 15 12

Resampled (2000) 20 E0.885 E0.073 0.621 804

Resampled (2008) 19 <0.02 E0.091 0.63 804

Bromodichloromethane Total (2000) 2 <0.048 <0.048 0.233 804

Total (2008) 2 <0.04 <0.04 0.371 804 0 2

Resampled (2000) 1 <0.048 <0.048 0.134 804

Resampled (2008) 1 <0.04 <0.04 0.371 804

Dibromochloromethane Total (2000) 2 E0.104 <0.18 <0.18 804

Total (2008) 2 <0.12 <0.12 0.769 804 0 2

Resampled (2000) 1 E0.104 <0.18 <0.18 804

Resampled (2008) 1 <0.12 <0.12 0.769 804

Bromoform (Tribromomethane) Total (2000) 1 E0.051 <0.06 <0.06 804

Total (2008) 2 <0.08 <0.08 0.632 804 0 2

Resampled (2000) 1 E0.051 <0.06 <0.06 804

Resampled (2008) 1 <0.08 <0.08 0.632 804

Group detections (n=30, 2008) 33 15 18

Solvents

Tetrachloroethene (PCE) Total (2000) 20 E0.42 <0.1 1.911 5

Total (2008) 11 E0.026 <0.04 1.616 5 4 7

Resampled (2000) 13 E0.468 <0.1 1.911 5

Resampled (2008) 9 E0.026 <0.04 1.616 5

Trichloroethene (TCE) Total (2000) 12 E0.012 <0.038 0.81 5

Total (2008) 8 E0.015 <0.02 0.581 5 5 3

Resampled (2000) 9 E0.012 <0.038 0.81 5

Resampled (2008) 7 E0.015 <0.02 0.581 5

Chloromethane Total (2000) 10 E0.028 <0.25 <0.5 --

Total (2008) 1 E0.042 <0.1 <0.14 -- 1 0

Resampled (2000) 8 E0.028 <0.5 <0.5 --

Resampled (2008) 0 <0.1 <0.1 <0.14 --

1,1,1-Trichloroethane Total (2000) 10 E0.79 <0.032 2.437 200

Total (2008) 4 <0.02 <0.02 1.102 200 3 1

Resampled (2000) 6 E0.79 <0.032 2.437 200

Resampled (2008) 2 <0.02 <0.02 1.102 200
20 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Table 5. Summary statistics for volatile organic compounds in groundwater samples from public water-supply wells screened in the 

Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum Contaminant Levels and HealthBased Sceening Levels in 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; ≥, greater than or equal to; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 

public water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; *, MCL set forth by the Delaware Division of Public 

Health; HBSL, Health-Based Screening Level; μg/L, micrograms per liter; --, no standard or guideline established, none detected above the MCL or (HBSL), 

where established]

Compound groups6 Network

Number 

of 

detections

Minimum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

MCL1

or 

(HBSL2,3)

Assessment Level

<0.2 μg/L ≥0.2 μg/L 

Solvents—Continued

1,1-Dichloroethane Total (2000) 6 E0.015 <0.066 0.149 --

Total (2008) 4 <0.04 <0.04 0.135 -- 4 0

Resampled (2000) 5 E0.015 <0.066 0.149 --

Resampled (2008) 3 <0.04 <0.04 0.135 --

cis1,2-Dichloroethene Total (2000) 4 E0.017 <0.038 E0.082 70

Total (2008) 2 <0.02 <0.02 1.268 70 1 1

Resampled (2000) 3 E0.017 <0.038 E0.082 70

Resampled (2008) 2 <0.02 <0.02 1.268 70

Carbon disulfide Total (2000) 4 E0.018 <0.07 <0.07 (700)

Total (2008) 2 <0.04 <0.06 E0.065 (700) 2 0

Resampled (2000) 3 E0.026 <0.07 <0.07 (700)

Resampled (2008) 1 <0.04 <0.06 <0.06 (700)

Chlorobenzene Total (2000) 2 <0.028 <0.028 0.488 1

Total (2008) 3 <0.02 <0.02 0.14 1 3 0

Resampled (2000) 2 <0.028 <0.028 0.488 1

Resampled (2008) 2 <0.02 <0.02 0.14 1

1,2-Dichlorobenzene Total (2000) 3 <0.031 <0.048 1.466 6

Total (2008) 3 <0.02 <0.02 0.357 6 2 1

Resampled (2000) 2 <0.031 <0.048 1.466 6

Resampled (2008) 2 <0.02 <0.02 0.357 6

Tetrahydrofuran Total (2000) 1 <2.2 <2.2 9.787 --

Total (2008) 2 E0.303 <1.4 2.113 -- 0 2

Resampled (2000) 1 <2.2 <2.2 9.787 --

Resampled (2008) 1 <1.4 <1.4 2.113 --

Dichloromethane Total (2000) 1 E0.018 <0.38 <0.38 5

Total (2008) 1 E0.016 <0.04 <0.04 5 1 0

Resampled (2000) 1 E0.018 <0.38 <0.38 5

Resampled (2008) 0 E0.022 <0.04 <0.04 5

Carbon tetrachloride Total (2000) 1 E0.026 <0.06 <0.06 5

Total (2008) 1 E0.02 <0.08 <0.08 5 1 0

Resampled (2000) 1 E0.026 <0.06 <0.06 5

Resampled (2008) 0 <0.06 <0.08 <0.08 5

1,2-Dichloroethane Total (2000) 1 <0.13 <0.13 0.133 5

Total (2008) 0 <0.06 <0.06 <0.06 5 0 0

Resampled (2000) 1 <0.13 <0.13 0.133 5

Resampled (2008) 0 <0.06 <0.06 <0.06 5
Methods of Study 21

Table 5. Summary statistics for volatile organic compounds in groundwater samples from public water-supply wells screened in the 

Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum Contaminant Levels and HealthBased Sceening Levels in 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; ≥, greater than or equal to; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 

public water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; *, MCL set forth by the Delaware Division of Public 

Health; HBSL, Health-Based Screening Level; μg/L, micrograms per liter; --, no standard or guideline established, none detected above the MCL or (HBSL), 

where established]

Compound groups6 Network

Number 

of 

detections

Minimum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

MCL1

or 

(HBSL2,3)

Assessment Level

<0.2 μg/L ≥0.2 μg/L 

Solvents—Continued

Acetone Total (2000) 1 E5.829 <7 <7 (6,000)

Total (2008) 0 <4 <4 <4 (6,000) 0 0

Resampled (2000) 1 E5.829 <7 <7 (6,000)

Resampled (2008) 0 <4 <4 <4 (6,000)

Methyl ethyl ketone Total (2000) 0 <1.6 <1.6 <1.6 (4,000)

Total (2008) 1 E0.441 <1.6 <1.6 (4,000) 0 1

Resampled (2000) 0 <1.6 <1.6 <1.6 (4,000)

Resampled (2008) 0 <1.6 <1.6 <1.6 (4,000)

1,2,4-Trichlorobenzene Total (2000) 0 <0.19 <0.19 <0.19 70

Total (2008) 1 E0.037 <0.08 <0.08 70 1 0

Resampled (2000) 0 <0.19 <0.19 <0.19 70

Resampled (2008) 0 <0.04 <0.08 <0.08 70

1,3-Dichlorobenzene Total (2000) 0 <0.03 <0.054 <0.054 (600)

Total (2008) 1 <0.02 <0.04 0.166 (600) 1 0

Resampled (2000) 0 <0.03 <0.054 <0.054 (600)

Resampled (2008) 0 <0.02 <0.04 <0.04 (600)

Group detections (n=30, 2008) 45 29 16

Gasoline oxygenates

Methyl tert-butyl ether (MTBE) Total (2000) 17 E0.048 0.204 12.03 10*5

Total (2008) 19 E0.028 0.117 2.554 10*5 5 14

Resampled (2000) 13 E0.048 0.313 8.6 10*5

Resampled (2008) 13 E0.096 0.17 2.554 10*5

Methyl tert-pentyl ether Total (2000) 9 E0.036 <0.11 0.437 --

Total (2008) 4 E0.031 <0.06 E0.086 -- 4 0

Resampled (2000) 6 E0.044 <0.11 0.251 --

Resampled (2008) 2 <0.06 <0.06 E0.086 --

Diisopropylether Total (2000) 2 E0.053 <0.1 0.467 --

Total (2008) 2 E0.034 <0.06 E0.091 -- 2 0

Resampled (2000) 2 E0.053 <0.1 0.467 --

Resampled (2008) 1 <0.06 <0.06 E0.091 --

Ethyl tert-butyl ether Total (2000) 1 <0.054 <0.054 0.364 --

Total (2008) 0 <0.04 <0.04 <0.04 -- 0 0

Resampled (2000) 0 <0.054 <0.054 <0.054 --

Resampled (2008) 0 <0.04 <0.04 <0.04 --

Group detections (n=30, 2008) 25 11 14
22 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Table 5. Summary statistics for volatile organic compounds in groundwater samples from public water-supply wells screened in the 

Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum Contaminant Levels and HealthBased Sceening Levels in 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; ≥, greater than or equal to; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 

public water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; *, MCL set forth by the Delaware Division of Public 

Health; HBSL, Health-Based Screening Level; μg/L, micrograms per liter; --, no standard or guideline established, none detected above the MCL or (HBSL), 

where established]

Compound groups6 Network

Number 

of 

detections

Minimum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

MCL1

or 

(HBSL2,3)

Assessment Level

<0.2 μg/L ≥0.2 μg/L 

Gasoline hydrocarbons

Toluene Total (2000) 9 E0.698 <0.05 <0.05 1,000

Total (2008) 1 <0.018 <0.02 E0.036 1,000 1 0

Resampled (2000) 6 E0.698 <0.05 <0.05 1,000

Resampled (2008) 1 <0.018 <0.02 E0.036 1,000

Benzene Total (2000) 4 E0.011 <0.035 0.293 5

Total (2008) 1 <0.016 <0.02 0.14 5 1 0

Resampled (2000) 4 E0.011 <0.035 0.293 5

Resampled (2008) 1 <0.016 <0.02 0.14 5

sec-Butylbenzene Total (2000) 2 E0.875 <0.032 0.235 --

Total (2008) 2 E0.014 <0.04 E0.099 -- 2 0

Resampled (2000) 2 E0.875 <0.032 0.235 --

Resampled (2008) 1 <0.02 <0.04 E0.099 --

Isopropylbenzene Total (2000) 1 E0.871 <0.032 <0.032 (700)

Total (2008) 0 <0.04 <0.04 <0.04 (700) 0 0

Resampled (2000) 1 E0.871 <0.032 <0.032 (700)

Resampled (2008) 0 <0.04 <0.04 <0.04 (700)

tert-butylbenzene Total (2000) 1 E0.045 <0.06 <0.06 --

Total (2008) 0 <0.06 <0.06 <0.06 -- 0 0

Resampled (2000) 1 E0.045 <0.06 <0.06 --

Resampled (2008) 0 <0.06 <0.06 <0.06 --

p-Isopropyltoluene Total (2000) 1 E0.583 <0.07 <0.07 --

Total (2008) 0 <0.06 <0.08 <0.08 -- 0 0

Resampled (2000) 1 E0.583 <0.07 <0.07 --

Resampled (2008) 0 <0.06 <0.08 <0.08 --

Styrene Total (2000) 0 <0.042 <0.042 <0.042 100

Total (2008) 1 <0.04 <0.04 0.257 100 0 1

Resampled (2000) 0 <0.042 <0.042 <0.042 100

Resampled (2008) 1 <0.04 <0.04 0.257 100

Group detections (n=30, 2008) 5 4 1

Refrigerants

1,1,2-Trichlorotrifluoromethane 

(CFC-113)

Total (2000) 11 E0.016 <0.06 0.233 (200,000)

Total (2008) 0 <0.04 <0.04 <0.042 (200,000) 0 0

Resampled (2000) 5 E0.022 <0.06 0.233 (200,000)

Resampled (2008) 0 <0.04 <0.04 <0.042 (200,000)
Methods of Study 23

Table 5. Summary statistics for volatile organic compounds in groundwater samples from public water-supply wells screened in the 

Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency Maximum Contaminant Levels and HealthBased Sceening Levels in 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; ≥, greater than or equal to; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 

public water-supply wells sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; *, MCL set forth by the Delaware Division of Public 

Health; HBSL, Health-Based Screening Level; μg/L, micrograms per liter; --, no standard or guideline established, none detected above the MCL or (HBSL), 

where established]

Compound groups6 Network

Number 

of 

detections

Minimum 

(μg/L)

Median 

(μg/L)

Maximum 

(μg/L)

MCL1

or 

(HBSL2,3)

Assessment Level

<0.2 μg/L ≥0.2 μg/L 

Refrigerants—Continued

Trichlorofluoromethane (CFC-11) Total (2000) 2 E0.015 <0.09 0.155 (2,000)

Total (2008) 1 E0.02 <0.08 <0.08 (2,000) 1 0

Resampled (2000) 1 <0.09 <0.09 0.155 (2,000)

Resampled (2008) 1 E0.02 <0.08 <0.08 (2,000)

Dichlorodifluoromethane 

(CFC-12)

Total (2000) 1 <0.27 <0.27 E1.618 (1,000)

Total (2008) 1 <0.1 <0.14 E1.327 (1,000) 0 1

Resampled (2000) 1 <0.27 <0.27 E1.618 (1,000)

Resampled (2008) 1 <0.1 <0.14 E1.327 (1,000)

Group detections (n=30, 2008) 2 1 1

Fumigants

1,4-Dichlorobenzene Total (2000) 2 E0.018 <0.05 0.511 75

Total (2008) 3 <0.02 <0.02 0.237 75 2 1

Resampled (2000) 2 E0.018 <0.05 0.511 75

Resampled (2008) 2 <0.02 <0.02 0.187 75

1,2-Dichloropropane Total (2000) 1 <0.029 <0.068 E0.073 5

Total (2008) 1 <0.02 <0.02 E0.071 5 1 0

Resampled (2000) 1 <0.029 <0.068 E0.073 5

Resampled (2008) 1 <0.02 <0.02 E0.071 5

Group detections (n=30, 2008) 4 3 1

Organic synthesis compounds

1,1-Dichloroethene Total (2000) 6 E0.942 <0.04 0.498 7

Total (2008) 3 <0.02 <0.02 0.236 7 2 1

Resampled (2000) 2 E0.036 <0.04 0.498 7

Resampled (2008) 2 <0.02 <0.02 0.236 7

Group detections (n=30, 2008) 3 2 1

Total VOC detections, among 30 

wells

117 65 52

1

 U.S. Environmental Protection Agency, 2009.

2

 Toccalino and others, 2004.

3

 Toccalino and others, 2008.

4

 MCL is for total THMs.

5

 MCL set in the State of Delaware 2002 Watershed Assessment Report 

305(b).

6

 Zogorski and others, 2006.
24 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

more than 95 percent of the samples analyzed using a lowlevel detection method (lower than 0.2 μg/L) demonstrated the 

vulnerability of the Columbia aquifer in Delaware to low-level 

VOC contamination (Zogorski and others, 2006). 

Field Parameters, Nutrients and Major Ions, and 

Trace Elements

Summary statistics for selected field parameters, nutrients, major ions, and trace elements in groundwater samples 

from public-supply wells are shown in table 6. Only three 

constituents have established MCLs: two nutrients (nitrate 

and nitrite) and one major ion (fluoride). Two wells out of the 

30 wells sampled had nitrate (NO3

-

) concentrations above the 

Federal drinking-water standard of 10 mg/L as nitrogen; both 

wells were in Sussex County (fig. 5). Concentrations of nitrite 

and fluoride did not exceed their MCLs. 

Non-enforceable guidelines (SMCLs or HALs) exist 

for eight of the sampled inorganic constituents (table 6). No 

sample fell within the range of the SMCL for pH, which is 

between 6.5 and 8.5; 29 of 30 samples were more acidic and 

the remaining sample was more basic (table 6). Both iron and 

manganese exceeded their SMCLs in four and six samples, 

respectively. Iron and manganese concentrations above their 

SMCLs were most frequently detected in Sussex and Kent 

Counties (fig. 5). Only one constituent, sodium, has a HAL 

(20 mg/L) for drinking water set by the Delaware Division 

of Public Health (table 6) (State of Delaware, 2002). Thirty 

percent of the 30 samples exceeded the HAL for sodium 

(table 6, fig. 5). 

More than 85 percent of the 30 wells sampled had dissolved oxygen levels greater than or equal to 1 mg/L (fig. 6), 

which was considered a threshold for oxic conditions in this 

study, following Denver and others (2004). Four samples had 

dissolved oxygen levels below 1 mg/L, and all were in Sussex 

County in predominantly poorly drained areas (fig. 5). The 

presence or absence of dissolved oxygen in groundwater is 

important as some chemicals of concern are stable and persistent under oxic conditions, most notably nitrate, and some are 

more prominent under reducing conditions, such as iron and 

manganese.

Nitrate was the predominant nutrient species detected 

in the Columbia aquifer, with 90 percent detection (table 6). 

Under natural conditions, nitrate concentrations rarely 

exceed 0.4 mg/L in groundwater on the Delmarva Peninsula 

(Hamilton and others, 1993); concentrations greater than the 

natural background level are likely impacted by anthropogenic activities. The major anthropogenic sources of nitrogen 

and phosphorus on the Peninsula are inorganic fertilizers and 

manure applications (Debrewer and others, 2007; Denver and 

others, 2004). Inputs from nitrogen fertilizer applications have 

increased since the 1940s, whereas data show that nutrient 

inputs from manure have recently decreased. Manure application still contributes significantly to total nutrient inputs, however (Debrewer and others, 2007; Denver and others, 2004). 

Figure 5. Locations of public water-supply wells sampled in 

2008 in the Columbia aquifer in Delaware with exceedances of 

criteria and guidelines for nutrients and major ions detected in 

groundwater. [USEPA, U.S. Environmental Protection Agency; 

MCLs, Maximum Contaminant Levels; PMCL, Primary MCL; 

SMCL, Secondary MCL; HAL, Health Advisory Limit set by the 

Delaware Department of Public Health.]
Methods of Study 25

Table 6. Summary statistics for selected field parameters, nutrients, major ions, and trace elements in groundwater samples from 

public water-supply wells screened in the Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency 

Primary and Secondary Maximum Contaminant Levels and Health Advisory Limits, 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 public water-supply wells 

sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; SMCL, Secondary Maximum Contaminant Level; HAL, Health Advisory Limit 

set forth by the Delaware Division of Public Health; °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 °C; mg/L, milligrams per liter; μg/L, 

micrograms per liter; --, no standard or guideline established; †, pH detections below SMCL; *, 29 pH detections below SMCL and 1 pH detection above 

SMCL in 2008]

Constituent Network

Number 

of 

detections

Minimum Median Maximum MCL1

Detections 

above 

MCL

SMCL1

or

(HAL2)

Detections 

above 

SMCL1

or 

(HAL2)

Field parameters

Water temperature (°C) Total (2000) 30 14 15.3 23.5 -- -- -- --

Total (2008) 30 13.5 15.8 24 -- -- -- --

Resampled (2000) 22 14 15.5 23.5 -- -- -- --

Resampled (2008) 22 13.5 15.8 24 -- -- -- --

Specific conductance 

(μS/cm)

Total (2000) 30 63 149 389 -- -- -- --

Total (2008) 30 62 176 343 -- -- -- --

Resampled (2000) 22 63 173 389 -- -- -- --

Resampled (2008) 22 62 178 331 -- -- -- --

Dissolved oxygen 

(mg/L)

Total (2000) 30 0.1 4.6 10 -- -- -- --

Total (2008) 30 0.11 4.6 10.1 -- -- -- --

Resampled (2000) 22 0.1 4.3 10 -- -- -- --

Resampled (2008) 22 0.11 4.2 10.1 -- -- -- --

pH (pH units) Total (2000) 30 4.5 5.4 6.9 -- -- 6.5-8.5 29†

Total (2008) 30 4.5 5.5 8.7 -- -- 6.5-8.5 30*

Resampled (2000) 22 5 5.5 6.9 -- -- 6.5-8.5 22†

Resampled (2008) 22 5.2 5.5 6.4 -- -- 6.5-8.5 22†

Alkalinity (as mg/L of 

CaCO3)

Total (2000) 29 3 13 41 -- -- -- --

Total (2008) 30 0.5 11.5 44 -- -- -- --

Resampled (2000) 22 5 15 41 -- -- -- --

Resampled (2008) 22 3 14 44 -- -- -- --

Nutrients

Nitrate (mg/L) Total (2000) 26 <0.05 5.204 11.314 10 1 -- --

Total (2008) 27 <0.04 4.884 12.114 10 2 -- --

Resampled (2000) 19 <0.05 5.204 11.314 10 1 -- --

Resampled (2008) 19 <0.04 4.884 12.114 10 2 -- --

Nitrite (mg/L) Total (2000) 1 <0.006 <0.01 0.024 1 -- -- --

Total (2008) 6 E0.001 <0.002 <0.006 1 -- -- --

Resampled (2000) 1 <0.006 <0.01 0.024 1 -- -- --

Resampled (2008) 5 E0.001 <0.002 <0.006 1 -- -- --
26 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Table 6. Summary statistics for selected field parameters, nutrients, major ions, and trace elements in groundwater samples from 

public water-supply wells screened in the Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency 

Primary and Secondary Maximum Contaminant Levels and Health Advisory Limits, 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 public water-supply wells 

sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; SMCL, Secondary Maximum Contaminant Level; HAL, Health Advisory Limit 

set forth by the Delaware Division of Public Health; °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 °C; mg/L, milligrams per liter; μg/L, 

micrograms per liter; --, no standard or guideline established; †, pH detections below SMCL; *, 29 pH detections below SMCL and 1 pH detection above 

SMCL in 2008]

Constituent Network

Number 

of 

detections

Minimum Median Maximum MCL1

Detections 

above 

MCL

SMCL1

or

(HAL2)

Detections 

above 

SMCL1

or 

(HAL2)

Nutrients—Continued

Ammonia (mg/L) Total (2000) 5 <0.02 <0.02 0.167 -- -- -- --

Total (2008) 9 E0.011 <0.02 0.798 -- -- -- --

Resampled (2000) 5 <0.02 <0.02 0.167 -- -- -- --

Resampled (2008) 7 E0.011 <0.02 0.263 -- -- -- --

Total phosphorus 

(mg/L)

Total (2000) 12 E0.002 <0.008 2.098 -- -- -- --

Total (2008) 13 E0.004 <0.012 0.127 -- -- -- --

Resampled (2000) 11 E0.004 <0.008 2.098 -- -- -- --

Resampled (2008) 12 E0.004 0.01 0.127 -- -- -- --

Major ions

Calcium (mg/L) Total (2000) 30 1.99 8.05 19.22 -- -- -- --

Total (2008) 30 0.05 10.50 21.29 -- -- -- --

Resampled (2000) 22 2.80 9.57 19.22 -- -- -- --

Resampled (2008) 22 0.05 11.08 21.29 -- -- -- --

Magnesium (mg/L) Total (2000) 30 0.73 3.91 12.40 -- -- -- --

Total (2008) 30 E0.01 4.44 13.59 -- -- -- --

Resampled (2000) 22 0.73 4.24 12.40 -- -- -- --

Resampled (2008) 22 E0.01 4.51 13.59 -- -- -- --

Sodium (mg/L) Total (2000) 30 5.3 11.7 25.9 -- -- (20) (1)

Total (2008) 30 5.2 14.2 34.5 -- -- (20) (9)

Resampled (2000) 22 5.3 11.7 25.9 -- -- (20) (1)

Resampled (2008) 22 5.2 14.2 34.5 -- -- (20) (6)

Potassium (mg/L) Total (2000) 30 1.05 2.23 16.45 -- -- -- --

Total (2008) 30 E0.02 2.54 11.68 -- -- -- --

Resampled (2000) 22 1.05 2.27 16.45 -- -- -- --

Resampled (2008) 22 E0.02 2.54 11.68 -- -- -- --

Chloride (mg/L) Total (2000) 30 4.62 18.28 60.75 -- -- 250 --

Total (2008) 30 4.50 18.62 56.86 -- -- 250 --

Resampled (2000) 22 4.62 18.91 60.75 -- -- 250 --

Resampled (2008) 22 4.50 20.91 56.86 -- -- 250 --
Methods of Study 27

Table 6. Summary statistics for selected field parameters, nutrients, major ions, and trace elements in groundwater samples from 

public water-supply wells screened in the Columbia aquifer in Delaware, and comparisons to U.S. Environmental Protection Agency 

Primary and Secondary Maximum Contaminant Levels and Health Advisory Limits, 2000 and 2008.—Continued

[LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less than MRL and is coded as estimated 

because of lower precision in this value; <, less than; Total, 30 public water-supply wells sampled in 2000 or 2008; Resampled, 22 public water-supply wells 

sampled in 2000 and 2008, active wells; MCL, Maximum Contaminant Level; SMCL, Secondary Maximum Contaminant Level; HAL, Health Advisory Limit 

set forth by the Delaware Division of Public Health; °C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 °C; mg/L, milligrams per liter; μg/L, 

micrograms per liter; --, no standard or guideline established; †, pH detections below SMCL; *, 29 pH detections below SMCL and 1 pH detection above 

SMCL in 2008]

Constituent Network

Number 

of 

detections

Minimum Median Maximum MCL1

Detections 

above 

MCL

SMCL1

or

(HAL2)

Detections 

above 

SMCL1

or 

(HAL2)

Major ions—Continued

Sulfate (mg/L) Total (2000) 29 E0.18 13.83 44.36 -- -- 250 --

Total (2008) 30 E0.11 18.53 35.33 -- -- 250 --

Resampled (2000) 21 <0.31 17.59 44.36 -- -- 250 --

Resampled (2008) 22 E0.11 20.56 33.22 -- -- 250 --

Fluoride (mg/L) Total (2000) 1 E0.09 <0.1 <0.2 4 -- 2 --

Total (2008) 1 <0.08 <0.12 0.59 4 -- 2 --

Resampled (2000) 0 <0.1 <0.1 <0.2 4 -- 2 --

Resampled (2008) 1 <0.08 <0.12 0.59 4 -- 2 --

Silica (mg/L) Total (2000) 30 9.41 17.65 39.23 -- -- -- --

Total (2008) 30 10.85 18.34 35.53 -- -- -- --

Resampled (2000) 22 9.41 18.78 39.23 -- -- -- --

Resampled (2008) 22 10.85 19.71 35.53 -- -- -- --

Total dissolved solids 

(mg/L)

Total (2000) 27 55.50 116.00 221.00 -- -- 500 --

Total (2008) 30 E46.16 E115.94 200.97 -- -- 500 --

Resampled (2000) 21 55.50 122.00 221.00 -- -- 500 --

Resampled (2008) 22 E46.16 122.61 E192.82 -- -- 500 --

Bromide (mg/L) Total (2000) 29 <0.01 0.053 0.115 -- -- -- --

Total (2008) 28 E0.017 0.047 0.194 -- -- -- --

Resampled (2000) 21 <0.01 0.053 0.115 -- -- -- --

Resampled (2008) 21 E0.017 0.046 0.194 -- -- -- --

Trace elements

Iron (μg/L) Total (2000) 20 E5.3 11.3 10,053 -- -- 300 5

Total (2008) 21 E3.6 <8 14,110 -- -- 300 4

Resampled (2000) 16 E6.0 12.8 10,053 -- -- 300 5

Resampled (2008) 16 <4 <8 14,110 -- -- 300 3

Manganese (μg/L) Total (2000) 27 E1.85 11.62 326.92 -- -- 50 6

Total (2008) 30 1.76 15.66 275.90 -- -- 50 6

Resampled (2000) 20 E2.10 13.60 326.92 -- -- 50 6

Resampled (2008) 22 1.76 20.25 275.90 -- -- 50 5

1

 U.S. Environmental Protection Agency, 2009.

2

 State of Delaware 2002 Watershed Assessment Report 305(b).
28 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Figure 6. Distribution of nutrients (nitrate as nitrogen and total phosphorus), major ions 

(magnesium), and trace elements (iron) concentrations in different oxidation-reduction (redox) 

environments in the Columbia aquifer among the 30 public water-supply wells sampled in 2008.
Methods of Study 29

Current 2008 data show that nitrate occurred at concentrations exceeding background concentrations in 83 percent 

of the 30 wells (Appendix B), with a median concentration of 

4.88 mg/L as nitrogen (table 6). Although the median concentration of nitrate was slightly lower in 2008 than the median 

concentration in 2000 (5.20 mg/L; Ferrari, 2002), these differences are not statistically significant (table 6). Debrewer and 

others (2007) also found that overall nitrate concentrations 

tended to be higher in oxic environments, such as upland 

regions, where soils are generally well-drained (figs. 5 and 6). 

Ator and Reyes (2008) found that nitrate concentrations 

greater than 3 mg/L in groundwater were most likely in areas 

with agricultural land use. Much of the nitrate in groundwater 

in the Delaware Coastal Plain is attributed to agricultural 

sources, as that is the predominant land use (Debrewer and 

others, 2007). 

Nitrate concentrations were positively correlated with 

dissolved oxygen in the Columbia aquifer (R2

=0.6998, 

p<0.0001) (fig. 7). In addition, median concentrations of 

nitrate and magnesium were significantly higher in oxic 

environments than in low-oxygen environments (p=0.0050 

and p=0.0283, respectively) (fig. 6). Debrewer and others 

(2007) and Denver and others (2004) found similar results on 

the Delmarva Peninsula. 

Concentrations of other nutrient species were generally 

lower than concentrations of nitrate in the Columbia aquifer 

in Delaware. Data from Denver and others (2004) and current 

2008 data indicated that concentrations of dissolved phosphorus in groundwater rarely exceeded 0.1 mg/L (see Appendix 

B) in spite of relatively large applications of phosphorus in 

inorganic fertilizers and manure (Denver and others, 2004). 

This finding is in large part explained by the chemical properties and mobility of phosphorus. Specifically, phosphorus 

readily attaches to soil particles under oxidizing conditions; it 

does not dissolve and move readily to the groundwater system. 

Under reducing conditions (where dissolved oxygen is absent), 

however, phosphorus is mobilized more readily in shallow 

groundwater and can be detected at concentrations greater than 

0.1μg/L (Denver and others, 2004). Current 2008 data from 

the Columbia aquifer follow this pattern; median phosphorus 

Figure 7. Relation of nitrate concentrations to dissolved-oxygen concentrations in the Columbia aquifer 

in Delaware, 2008.
30 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

concentrations were significantly higher in low-oxygen environments than in oxic environments (p=0.0033) (fig. 6). 

Dissolved iron is often a major component of natural 

groundwaters associated with reducing conditions (Shedlock 

and others, 1999). Median iron concentrations were significantly higher in low-oxygen environments than oxic environments (p=0.0036) (fig. 6). The median concentration of iron in 

water with low dissolved oxygen levels exceeded the SMCL 

of 300 μg/L for iron in drinking water. 

No differences in nutrients or major ions were found 

between samples collected in 2000 and 2008. Two field 

parameters, pH and dissolved oxygen, however, were both 

significantly higher in 2008 than in 2000. Although pH and 

dissolved oxygen were significantly higher in 2008, the average pH was still moderately acidic (median of 5.5) (table 6) 

and most groundwater samples were oxic. 

Radium and Radon

Radon and radium-226 had a 100-percent detection rate 

in nine samples collected; five samples also had detectable 

levels of radium-228 (table 7). Radium isotopes and radon 

sampling distribution are shown in figure 8; most of the wells 

are in New Castle and Sussex Counties. Wells were selected 

for sampling in New Castle County (Bachman and Ferrari, 

1995) in areas with aquifer characteristics similar to those 

in areas of Maryland (Bolton, 2000) and New Jersey (Szabo 

and DePaul, 1998), where radium was detected in groundwater (fig. 8). The remainder of the wells sampled were mainly 

in agricultural areas. Szabo and DePaul (1998) previously 

found an apparent relation between radium concentration and 

agricultural land use in New Jersey, and Bolton (2000) found a 

relation between sodium chloride and radiochemical activities 

Table 7. Radiochemical activities for groundwater samples from public water-supply wells screened in the Columbia aquifer in 

Delaware, and comparisons to U.S. Environmental Protection Agency Maximum Contaminant Levels in 2000 and 2008.

[DGS, Delaware Geological Survey; LTMDL, long-term method detection limit; MRL, method reporting level; E, value is greater than the LTMDL but less 

than MRL and is coded as estimated because of lower precision in this value; <, less than; --, no data; Resampled, 22 public water-supply wells sampled in 

2000 and 2008, active wells; Replaced by, public water-supply well sampled only in 2000, not active in 2008; Replacement, public water-supply well sampled 

only in 2008; MCL, Maximum Contaminant Level; all units in picocuries per liter; bold, public water-supply well sampled in 2000 with detection above the 

MCL.]

DGS local well 

number Type of well

Radium-226 Radium-228 Radon-222

2000 2008 2000 2008 2000 2008

Cd42-18 Replacement -- 0.16 -- 0.43 -- 175

Cd52-15 Replaced by Cd42-18 <1.00 -- <1.00 -- 192 --

Db11-27 Resampled <1.00 0.08 <1.00 <-0.04 246 237

Db11-28 Resampled <1.00 0.16 <1.00 0.28 222 200

Dc31-15 Resampled <1.00 0.08 <1.00 0.28 260 286

Forest Hills1 Replaced by Pg31-12 <1.00 -- <1.00 -- 220 --

Pg31-12 Replacement -- 0.13 -- 0.30 -- 204

Hc34-03 Resampled <1.00 0.39 1.13 0.85 167 132

Ng25-043 Resampled -- 0.09 -- <0.20 -- 71

Pc33-44 Replaced by Ng25-04 1.29 -- -- 155 --

Pe23-185 Resampled <1.00 0.02 <1.00 <0.07 79 73

PN1 Replaced by Pi32-15 <1.00 -- <1.00 -- 343 --

Qd52-09 Resampled <1.00 0.04 <1.00 <0.12 221 182

Number of radiochemical activities among 

all 9 wells 1 9 1 5 1 9

Number of radiochemical activities among 

resampled wells (6) 0 7 1 3 6 7

MCL1 52 52 300

1

 U.S. Environmental Protection Agency, 2009.

2

 MCL for combined radium-226 and radium-228.

3

 Well not sampled for radiochemical activities in 2000.
Methods of Study 31

Figure 8. Locations of public water-supply wells sampled in 

2008 in the Columbia aquifer in Delaware for radiochemical 

activities.

including radium-226, radium-228, gross-alpha-particle activity and gross-beta-particle activity. Radium occurs naturally 

in groundwater and is a daughter product from the decay of 

uranium and thorium, but can be mobilized by processes similar to those that mobilize other alkaline earth metals. Although 

some radionuclides were detected, none were found at concentrations above applicable drinking-water standards in 2008 

(table 7). 

Temporal differences in radioactive elements were difficult to determine with the available data. Even though recent 

data indicate a higher number of detections, the frequency 

of detection was affected by the change in detection limits 

between 2008 and 2000. The activities for radium isotopes still 

remain below 1 picocurie per liter. 

Groundwater Age Results

Average groundwater age ranged from 6 to 35 years, with 

a median of 21.5 years among the 30 wells sampled in 2008. 

Groundwater ages are positively correlated with well depth 

(fig. 9a) and negatively correlated with dissolved-oxygen concentrations (fig. 9b) in the Columbia aquifer.

Comparison of the data (fig. 10a) from resampled wells 

indicates that the average groundwater age was significantly 

different; samples collected in 2008 were on average 7 years 

older than samples collected in 2000 (p<0.0001) (fig. 10b). 

In 2000, the median age of groundwater was 15 years, and 

ranged from 7 to 23 years; in 2008, the median age of groundwater in the resampled wells was 22 years, and ranged from 6 

to 34.6 years. Groundwater age represents a mixture of older 

and younger groundwater because well screens in public-supply wells are relatively long and pumping enhances the mixing 

of waters of disparate groundwater ages (Dunkle and others, 

1993). The reason for the difference in groundwater age in the 

samples from 2000 and 2008 is unknown. Gholam and others 

(2006) indicated that this age difference could reflect a higher 

proportion of water drawn from slow-moving storage, possibly 

due to pumping for longer periods of time, or an increase in 

pumpage that caused more water from older, deeper, or more 

distant sources to be drawn into the well. 
32 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Figure 9. Relation of average modeled groundwater sample to (A) well depth, and (B) dissolved-oxygen 

concentrations in the Columbia aquifer in Delaware, 2008.
Summary 33

Figure 10. (A) comparison and (B) distribution of average modeled groundwater sample age over the 8-year study period from the 

22 sampled wells in the Columbia aquifer in Delaware, 2000 to 2008.

Summary

The U.S. Geological Survey collected water-quality 

sampling data from 30 public-supply wells screened in the 

Columbia aquifer in Delaware from August through November 

of 2008. The data indicate that human influences are apparent 

in groundwater. Dissolved contaminants appear to be derived 

mainly from agricultural practices, and influenced by natural 

and anthropogenic factors. A comparison of average modeled 

groundwater age indicates that the actual groundwater age in 

2008 samples was significantly older than the groundwater age 

in samples from 2000. The average groundwater age difference between the study periods among the resampled wells 

was 7 years.

There were no significant differences in water-quality 

data during the 8-year period for either pesticides or pesticide 

degradates; similar patterns existed for the number of compounds detected per well in both sampling rounds. A variety of 

pesticides and degradate compounds were detected in groundwater of the Columbia aquifer at low levels. Metolachlor, 

atrazine, and alachlor, and their degradates, were the most 

commonly detected pesticide compounds; degradation products were detected more frequently and at higher concentrations than their parent compounds. Almost 80 percent of the 

24 pesticide and pesticide degradate compounds detected were 

agricultural herbicides. Mixtures of pesticides were prevalent 

in 90 percent of the groundwater samples, which reflects 

similar usage patterns; multiple compounds are often applied 

to the same area (often in mixed formulations) for greater 

pest control. None of the pesticides or pesticide degradates 

exceeded U.S. Environmental Protection Agency Maximum 

Contaminant Levels (MCLs). Dieldrin exceeded the nonregulatory Health-Based Screening Level (HBSL) (0.002 

μg/L/micrograms per liter) in all nine samples with detected 

concentrations.

Even though there were no significant differences in volatile organic compound (VOC) concentrations, the mean number of VOCs detected per well decreased significantly in 73 

percent of the resampled wells. Of the 85 VOCs analyzed in 

this study, 31 were detected at concentrations that were generally less than 1 μg/L; only one well had no detectable concentration of any VOC. VOCs were classified in seven groups, trihalomethanes (THMs), solvents, gasoline oxygenates, gasoline 

hydrocarbons, refrigerants, fumigants, and organic synthesis 

compounds; the greatest number of detections occurred in the 

solvents group. Chloroform—a THM—and Methyl-tert butyl 

ether (MTBE)—a gasoline oxygenate—were present in more 

than 50 percent of the samples. None of the VOCs exceeded 

USEPA MCLs or non-regulatory HBSLs.

Median values for pH and dissolved oxygen, respectively, from 2000 and 2008 differed. Almost all of the samples 

(29 of 30) were moderately acidic and fell below the lower 
34 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Secondary Maximum Contaminant Level (SMCL) for pH 

(6.5); the only sample that was not acidic exceeded the upper 

limit of the SMCL (8.5). More than 85 percent of the 30 wells 

sampled showed oxidizing aquifer conditions with dissolvedoxygen concentrations above 1 mg/L (milligram per liter); 

four samples had dissolved-oxygen concentrations below 1 

mg/L—these wells were in poorly drained areas of Sussex 

County.

Nitrate, the predominant nutrient species detected in 

samples from the Columbia aquifer in Delaware, had a median 

concentration of 4.88 mg/L, which was not significantly different from the median nitrate concentration in 2000 (5.20 mg/L). 

Samples from two wells exceeded the MCL for nitrate (10 

mg/L). Differences in nitrate concentrations over the 8-year 

study period in the same well were small and increased in 

some wells or decreased in others. Overall, nitrate concentrations were positively correlated with dissolved oxygen in the 

Columbia aquifer and higher in upland regions where soils are 

generally well-drained and agriculture is more prevalent than 

in poorly drained regions of Delaware.

Median concentrations of phosphorus and iron were 

significantly higher in low-oxygen environments than oxic 

environments; the median concentration of iron from wells in 

low-oxygen environments exceeded the SMCL (300 mg/L). 

Several samples had detections of major ions above the 

USEPA SMCL for iron or manganese (50 mg/L) or the Health 

Advisory Level (HAL) for sodium (20 mg/L) in drinking 

water set by the Delaware Division of Public Health.

Radon and radium-226 had a 100-percent detection 

rate in the nine samples collected at the six resampled wells. 

Radium-228 had a 50-percent detection rate in the nine samples collected at the six resampled wells. In 2008, none of the 

radiochemical activities were above any established drinkingwater standards or MCLs. 

Acknowledgments

This project was funded under a cooperative agreement 

between the Delaware Geological Survey (DGS) and the 

U.S. Geological Survey (USGS), in support of the Delaware 

Department of Natural Resources and Environmental Control 

(DNREC). 

The author would like to thank DNREC employees 

Anne Mundel, Douglas Rambo, and John Barndt for their 

help, cooperation, and support in providing the database of 

public water-supply wells and assisting in the selection of the 

replacement wells. Scott Andres from DGS is thanked for his 

assistance in providing the well identification numbers. USGS 

employees Deborah A. Bringman and Michael S. Brownley 

provided office and field technical support for this project, and 

are also thanked. In addition, the authors thank well owners 

and water managers who allowed access to their property to 

sample the wells for this study.

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Appendixes A–H 39

Appendixes A–H
40 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix A. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Field parameters.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; mm Hg, millimeters of mercury; mg/L, milligrams per liter; °C, degrees Celsius; 

μS/cm, microsiemens per centimeter at 25°C; --, no data]

USGS site 

identification 

number

DGS 

local well 

number

Sample 

date

Sample 

time

Field parameters

Water 

temperature 

(°C)

Air 

pressure 

(mm Hg)

Dissolved 

oxygen 

(mg/L)

pH 

(field 

units)

Alkalinity 

(mg/L as 

CaCO3)

Specific 

conductance, 

field 

(μS/cm)

Air 

temperature 

(°C)

382805075330301 Rd22-01 9/10/2008 1430 17 762 0.8 5.5 21 91 --

382830075073601 Ri23-04 9/10/2008 1030 15.5 762 0.9 5.9 28 166 --

383000075326001 Qd52-09 9/9/2008 0930 16.5 759 3.4 5.6 13 83 23

383101075141101 Frankford4 8/27/2008 1100 16 762 0.3 6 30 236 22

383311075344401 Qd21-12 9/23/2008 1130 16 769 4.1 5.5 8 137 19.5

383713075085501 Pi32-15 10/21/2008 1030 15 762 7.2 5.5 9 120 12

383713075085501 Pi32-15 10/21/2008 1100 -- -- -- -- -- -- --

383729075101601 Ph35-25 10/21/2008 1430 16 762 4.1 5.6 8 92 14

383732075191301 Pg31-12 10/14/2008 1100 16 765 9.6 8.7 7 199 16.5

383815075271001 Pe23-185 8/7/2008 1200 24 757 0.11 6.4 44 102 31

383815075271001 Pe23-185 8/7/2008 1215 -- -- -- -- -- -- --

383823075382101 Pc22-06 9/8/2008 1330 17 6.4 4.5 0.5 165 29

383914075080501 Pi12-11 10/20/2008 1130 14 765 4.7 5.5 7 141 11

384139075230101 Of42-01 9/9/2008 1430 16 759 1.8 5.3 21 268 21

384322075051101 Oi25-18 9/25/2008 1330 15.5 767 4.9 5.6 20 197 18.5

384326075050801 Oi25-19 9/25/2008 1030 15 767 3.4 5.5 16 250 18

384428075135501 Oh12-07 11/13/2008 1030 14.5 766 7.1 5.5 6 117 13

384428075135501 Oh12-07 11/13/2008 1100 -- -- -- -- -- -- --

384428075355701 Oc15-11 8/26/2008 1100 16 763 7.6 5.3 3 175 23

384526075091601 Ni51-32 10/8/2008 1100 15 762 4.7 5.5 9 162 18.5

384818075354101 Nc25-37 8/21/2008 1100 18 767 4.1 6.4 39 269 27

384819075190101 Ng21-03 9/16/2008 1200 15 764 10.1 5.2 3 164 23.5

384856075151101 Ng25-04 9/17/2008 1100 15.5 763 3.1 5.5 7 62 19

385448075341801 Md11-04 8/28/2008 1100 16.5 763 4.8 5.6 13 255 24

385522075251802 Le55-09 11/12/2008 1100 15 771 4.2 5.8 11 182 11

390617075261901 Je55-01 11/6/2008 1030 16 757 3.6 5.2 12 240 16.5

390652075370701 Jc43-05 8/5/2008 1100 16 761 5.4 5.3 8 177 29.5

390652075370701 Jc43-05 8/5/2008 1115 -- -- -- -- -- -- --

391060075282801 Ie42-03 8/19/2008 1100 15.5 762 3.5 5.4 6 178 29.5

391747075364202 Hc34-03 9/2/2008 1100 15.5 764 5.7 5.4 11 174 26.5

393739075394202 Dc31-15 10/7/2008 1030 13.5 769 9.1 5.6 16 311 13

393916075440802 Db11-28 10/2/2008 1400 17 752 4.5 5.5 15 328 11.5

393928075440202 Db11-27 10/2/2008 1100 15 752 6.8 5.5 16 331 13

394102075334301 Cd42-18 10/7/2008 1400 15 769 8.2 5.6 22 343 16
Appendixes A–H 41

Appendix B. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Nutrients.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in milligrams per liter; E, estimated; --, not detected; 

N, nitrogen]

USGS site 

identification 

number

DGS 

local well 

number

Nutrients

Ammonia 

as N

Dissolved 

ammonia 

plus organic 

nitrogen as N

Total 

ammonia 

plus organic 

nitrogen as N

Nitrite as N Nitrite plus 

nitrate as N

Dissolved 

phosphorus 

Total 

phosphorus 

382805075330301 Rd22-01 -- -- -- -- 0.718 E0.005 E0.004

382830075073601 Ri23-04 0.032 -- E0.07 0.002 0.322 0.020 0.025

383000075326001 Qd52-09 -- -- -- E0.001 2.322 0.007 E0.008

383101075141101 Frankford4 0.263 0.385 3.30 0.003 -- 0.121 0.127

383311075344401 Qd21-12 E0.013 E0.074 -- -- 7.260 E0.004 E0.006

383713075085501 Pi32-15 -- -- -- -- 3.305 E0.004 --

383729075101601 Ph35-25 -- -- -- -- 2.585 E0.005 --

383732075191301 Pg31-12 -- -- -- -- 7.263 -- --

383815075271001 Pe23-185 -- -- -- -- 0.000 0.034 0.034

383823075382101 Pc22-06 E0.011 -- -- -- 7.261 -- --

383914075080501 Pi12-11 -- -- -- -- 0.299 -- --

384139075230101 Of42-01 0.034 E0.134 E0.11 E0.001 4.485 0.017 0.017

384322075051101 Oi25-18 0.024 E0.087 E0.08 -- 2.298 -- --

384326075050801 Oi25-19 -- -- -- -- 1.058 E0.004 --

384428075135501 Oh12-07 -- E0.062 -- -- 6.696 -- --

384428075355701 Oc15-11 -- -- -- -- 12.114 -- --

384526075091601 Ni51-32 -- E0.072 E0.05 E0.001 5.282 E0.005 --

384818075354101 Nc25-37 -- E0.087 -- -- 9.224 -- --

384819075190101 Ng21-03 -- -- -- -- 10.695 -- --

384856075151101 Ng25-04 -- -- -- -- 0.955 -- E0.005

385448075341801 Md11-04 -- E0.105 E0.08 -- 8.276 0.006 0.001

385522075251802 Le55-09 0.107 0.150 0.13 -- 0.000 0.049 0.055

390617075261901 Je55-01 0.798 0.968 0.92 E0.001 3.839 -- E0.007

390652075370701 Jc43-05 -- -- E0.08 -- 5.486 -- --

391060075282801 Ie42-03 -- -- E0.10 -- 3.302 0.032 0.031

391747075364202 Hc34-03 -- -- -- -- 5.887 0.015 0.017

393739075394202 Dc31-15 -- -- -- -- 6.006 -- --

393916075440802 Db11-28 E0.011 E0.061 E0.06 -- 5.304 -- --

393928075440202 Db11-27 -- -- E0.06 -- 9.584 E0.003 --

394102075334301 Cd42-18 -- -- -- -- 5.904 -- --
42 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08 Appendix C. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through November, 2008—Major ions and trace elements. [USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; mg/L, milligrams per liter; μg/L, micrograms per liter; E, estimated; --, not detected] USGS site identification number DGS local well number Major ions and trace elements Bicar- bonate (mg/L) Bro- mide (mg/L as Br) Calcium (mg/L as Ca) Chlo- ride (mg/L as Cl) Fluo- ride (mg/L as F) Mag- nesium (mg/L as Mg) Man- ganese (μg/L as Mn) Potas- sium (mg/L as K) Silica (mg/L as SiO2

)

Sodium 

(mg/L 

as Na)

Sulfate 

(mg/L 

as SO4

)

Dissolved 

noncarbonate hardness (mg/L 

as CaCO3

)

 Total 

hardness 

(mg/L as 

CaCO3

)

Total 

Iron 

(μg/L as 

Fe)

382805075330301 Rd22-01 26 0.044 3.86 9.64 -- 0.94 45.47 1.31 35.5 12.3 3.65 -- 13.49 --382830075073601 Ri23-04 34 0.044 8.60 17.42 -- 2.83 36.31 1.41 32.3 15.6 20.75 5.24 33.14 3,528.0383000075326001 Qd52-09 16 0.030 3.72 8.01 -- 1.02 4.28 1.41 25.3 10.3 3.76 0.34 13.47 --383101075141101 Frankford4 37 0.047 11.17 33.28 -- 1.84 74.86 1.58 26.4 19.7 15.01 5.10 35.46 14,110.0383311075344401 Qd21-12 10 0.079 10.26 12.43 -- 4.54 17.11 2.82 19.8 9.6 17.31 36.09 44.30 18.8383713075085501 Pi32-15 11 0.071 4.75 17.08 -- 2.83 7.01 2.00 19.7 11.0 4.66 14.49 23.53 --383729075101601 Ph35-25 10 0.059 3.17 12.70 -- 1.22 14.82 1.45 19.4 11.2 2.42 4.75 12.96 --383732075191301 Pg31-12 9 -- 6.81 15.29 -- 3.92 6.44 3.07 15.8 27.6 1.91 25.75 33.15 --383815075271001 Pe23-185 53 E0.018 0.05 4.50 -- E0.01 30.16 E 0.02 29.2 25.6 0.40 -- E 0.17 --383823075382101 Pc22-06 0.6 0.030 9.01 13.51 -- 4.54 46.37 3.49 13.3 5.6 19.75 40.71 41.21 353.0383914075080501 Pi12-11 9 0.114 3.49 29.53 -- 2.80 6.44 1.88 15.2 17.2 7.38 12.84 20.23 60.1384139075230101 Of42-01 25 0.194 14.63 29.49 -- 5.79 82.75 11.68 21.6 20.2 31.49 39.87 60.39 80.4384322075051101 Oi25-18 24 0.077 11.21 26.22 -- 6.64 5.50 2.12 10.9 14.6 22.17 35.63 55.32 E 6.8384326075050801 Oi25-19 19 0.124 9.03 40.82 -- 9.71 3.18 2.66 14.1 21.5 30.48 46.95 62.54 26.3384428075135501 Oh12-07 7 0.047 6.76 11.53 -- 1.58 2.86 1.60 22.3 9.9 3.89 17.64 23.39 E 3.6384428075355701 Oc15-11 4 0.040 12.61 18.66 -- 3.30 5.36 3.48 21.4 11.2 E 0.11 41.80 45.09 E 5.1384526075091601 Ni51-32 11 0.070 8.10 18.57 -- 3.65 8.61 2.23 17.3 13.7 13.68 26.24 35.27 --384818075354101 Nc25-37 48 -- 11.16 24.17 0.59 5.62 32.41 3.29 19.6 34.5 4.90 11.61 50.99 E 4.2384819075190101 Ng21-03 3 0.044 10.73 14.95 -- 4.40 9.54 5.73 12.6 5.2 3.20 42.44 44.91 E 5.3384856075151101 Ng25-04 8 0.043 1.60 10.86 -- 0.55 1.76 1.28 14.5 8.3 0.87 -- 6.24 77.5385448075341801 Md11-04 16 0.047 19.73 27.10 -- 5.64 16.49 1.86 25.5 16.6 26.75 59.36 72.49 62.7385522075251802 Le55-09 13 0.056 11.03 23.15 -- 3.39 193.20 2.42 21.0 12.0 33.22 30.84 41.52 5,804.0390617075261901 Je55-01 15 0.057 5.40 27.08 -- 4.58 176.80 3.28 12.7 32.9 35.33 20.03 32.34 59.3390652075370701 Jc43-05 10 0.036 13.05 14.74 -- 4.47 24.74 1.98 26.3 9.9 25.55 42.80 51.01 244.2391060075282801 Ie42-03 7 0.078 11.13 16.47 -- 6.11 23.39 3.96 15.6 9.6 32.85 47.22 52.97 16.9391747075364202 Hc34-03 14 0.042 10.96 23.16 -- 6.17 62.55 4.11 15.3 11.3 20.38 41.27 52.77 --393739075394202 Dc31-15 19 0.043 15.83 49.28 -- 8.84 3.92 3.67 13.8 24.8 24.39 60.33 75.93 --393916075440802 Db11-28 19 0.063 17.40 56.86 -- 9.68 275.90 3.28 14.0 24.7 21.15 67.70 83.30 38.1393928075440202 Db11-27 20 0.050 21.29 44.06 -- 13.59 2.91 2.76 13.7 15.0 30.07 92.71 109.13 4.4394102075334301 Cd42-18 27 0.078 19.72 53.04 -- 11.62 4.52 2.80 14.8 25.8 33.63 74.94 97.10 4.0
Appendixes A–H 43

Appendix D. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through November, 2008—Pesticides.[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations are in micrograms per liter; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Pesticides

Atrazine Ala- chlor alpha- HCH Butyl- ate Carbofu- ran Dieldrin EPTC (Eptam) Fipronil Lindane Metola- chlor Pebulate Prometon Simazine Tebuthi- uron

383311075344401 Qd21-12 E0.005 -- -- -- -- 0.017 -- -- -- 0.087 -- -- E0.004 --383713075085501 Pi32-15 0.007 -- -- -- -- -- -- -- -- -- -- -- -- --383815075271001 Pe23-185 -- -- -- -- -- -- -- E0.003 -- -- -- -- -- --383823075382101 Pc22-06 0.049 0.049 -- -- -- -- -- -- -- 0.034 -- 0.009 E0.006 --384139075230101 Of42-01 -- -- -- -- -- 0.011 -- -- -- -- -- -- -- --384322075051101 Oi25-18 -- -- -- -- -- 0.084 -- E0.004 -- -- -- 0.034 -- --384326075050801 Oi25-19 -- -- -- -- -- 0.026 -- -- -- -- -- E0.005 -- --384428075135501 Oh12-07 -- 0.030 -- -- -- -- -- -- -- -- -- -- -- --384428075355701 Oc15-11 -- 0.055 -- -- E0.056 -- -- -- -- 0.024 -- -- -- --384526075091601 Ni51-32 0.021 -- -- -- -- -- -- -- E0.007 -- -- -- --384818075354101 Nc25-37 0.022 0.011 -- -- E0.017 -- -- -- -- 0.053 -- E0.005 -- --384819075190101 Ng21-03 0.488 0.000 -- -- E0.017 -- -- -- -- E0.003 -- -- -- --385448075341801 Md11-04 0.044 E0.006 -- -- -- -- -- -- -- 0.083 -- -- -- --390652075370701 Jc43-05 0.009 -- -- -- -- -- -- -- -- E0.003 -- -- -- --391060075282801 Ie42-03 0.052 -- -- -- -- -- -- -- -- E0.008 -- -- E0.005 --391747075364202 Hc34-03 0.028 0.010 -- -- -- 0.053 -- E0.004 -- 0.028 -- 0.010 0.011 0.029393739075394202 Dc31-15 0.067 -- -- -- -- 0.036 -- E0.009 -- E0.007 -- -- 0.018 0.047393916075440802 Db11-28 0.096 -- -- -- -- 0.037 -- E0.011 -- E0.005 -- 0.049 0.013 E0.018393928075440202 Db11-27 0.203 E0.006 E0.002 0.002 -- 0.074 0.009 E0.018 E0.006 0.055 E0.005 0.013 0.032 0.026394102075334301 Cd42-18 0.027 -- -- -- -- 0.083 -- E0.009 -- -- -- -- 0.022 --
44 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08 Appendix E. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through November, 2008—Pesticide degradates. [USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations are in micrograms per liter; ESA, ethanesulfonic acid; OA, oxanilic acid; SA, second amide; E, estimated; --, not detected] USGS site identification number DGS local well number Pesticide degradates Alachlor ESA Alachlor ESA SA Alachlor OA Aminomethyl phosphonic acid Deethylatrazine (CIAT) Fipronil sulfide Fipronil sulfone Metolachlor ESA Metolachlor OA 2-[(2-Ethyl-6- methylphe- nyl)amino]-2- oxoESA 382805075330301 Rd22-01 0.06 -- -- -- -- -- -- 0.03 -- -- 382830075073601 Ri23-04 0.45 0.02 -- -- -- -- -- 0.22 -- -- 383000075326001 Qd52-09 -- -- -- -- E0.005 -- -- 0.15 -- -- 383101075141101 Frankford4 0.18 -- 0.03 -- -- -- -- 0.19 -- -- 383311075344401 Qd21-12 0.2 -- 0.02 -- E0.013 -- -- 1.23 0.61 0.05 383713075085501 Pi32-15 0.08 -- -- -- E0.032 -- -- 0.09 -- -- 383729075101601 Ph35-25 -- -- -- -- E0.005 -- -- 0.05 0.04 -- 383732075191301 Pg31-12 2.11 -- -- 0.03 E0.051 -- -- 3.95 0.13 -- 383823075382101 Pc22-06 0.41 -- 0.05 -- E0.091 -- -- 1.72 0.33 -- 384139075230101 Of42-01 0.02 -- -- -- E0.005 -- -- -- -- -- 384322075051101 Oi25-18 -- -- -- -- E0.002 -- -- 0.05 -- -- 384326075050801 Oi25-19 -- -- -- -- E0.002 -- -- 0.1 -- -- 384428075135501 Oh12-07 0.31 -- 0.03 0.16 E0.028 -- -- 0.07 -- -- 384428075355701 Oc15-11 0.27 -- 0.1 -- E0.195 -- -- 2.77 0.09 0.02 384526075091601 Ni51-32 0.03 -- -- E0.039 -- -- 0.22 -- -- 384818075354101 Nc25-37 0.51 0.02 0.13 -- E0.076 -- -- 3.21 0.26 0.03 384819075190101 Ng21-03 2.09 -- 0.02 -- E0.112 -- -- 1.25 0.15 384856075151101 Ng25-04 -- -- -- -- E0.003 -- -- -- -- -- 385448075341801 Md11-04 0.48 -- 0.07 0.03 E0.059 -- -- 0.58 0.19 0.02 385522075251802 Le55-09 0.21 -- 0.2 0.28 -- -- -- 0.2 0.03 390617075261901 Je55-01 -- 0.03 -- -- -- -- -- 0.03 -- -- 390652075370701 Jc43-05 0.16 -- -- -- E0.009 -- -- -- -- -- 391060075282801 Ie42-03 0.37 -- 0.02 -- E0.082 -- -- 2.28 0.3 0.02 391747075364202 Hc34-03 0.3 -- 0.02 -- E0.013 -- E0.002 0.3 0.08 393739075394202 Dc31-15 0.1 -- -- -- E0.068 -- -- 0.55 0.08 0.03 393916075440802 Db11-28 0.12 -- -- -- E0.038 E0.003 E0.006 0.91 0.18 0.03 393928075440202 Db11-27 0.21 0.04 -- -- E0.171 -- E0.004 3.15 0.98 0.39 394102075334301 Cd42-18 -- -- -- -- E0.011 -- 0.003 -- -- --
Appendixes A–H 45

Appendix F. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations are in micrograms per liter; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Volatile organic compounds

Benzene

Bromodichloromethane

sec-ButylbenzeneCarbon 

disulfide

ChlorobenzeneChloromethane

Dibromochloromethane

1,2-Dichlorobenzene

382805075330301 Rd22-01 -- -- -- -- 0.14 -- -- 0.357

383000075326001 Qd52-09 -- -- -- -- -- -- -- --

383101075141101 Frankford4 -- -- -- -- -- -- -- --

383311075344401 Qd21-12 -- -- -- -- -- -- -- --

383713075085501 Pi32-15 -- -- -- -- -- -- --

383729075101601 Ph35-25 -- -- -- -- -- -- -- --

383732075191301 Pg31-12 -- 0.255 -- E0.065 -- E0.042 0.453 --

383815075271001 Pe23-185 -- -- -- E0.057 -- -- -- --

383823075382101 Pc22-06 -- -- -- -- -- -- -- --

383914075080501 Pi12-11 -- -- -- -- -- -- -- --

384139075230101 Of42-01 -- -- E 0.099 -- E0.062 -- -- E0.042

384322075051101 Oi25-18 -- -- -- -- -- -- -- --

384326075050801 Oi25-19 -- -- -- -- -- -- -- --

384428075135501 Oh12-07 -- -- -- -- -- -- -- --

384428075355701 Oc15-11 -- -- -- -- -- -- -- --

384526075091601 Ni51-32 -- -- -- -- -- -- -- --

384818075354101 Nc25-37 -- 0.371 -- -- -- -- 0.769 --

384819075190101 Ng21-03 -- -- -- -- -- -- -- --

384856075151101 Ng25-04 -- -- -- -- -- -- -- --

385448075341801 Md11-04 -- -- -- -- -- -- -- --

385522075251802 Le55-09 0.140 -- -- -- -- -- --

390617075261901 Je55-01 -- E0.014 -- 0.044 -- -- 0.149

390652075370701 Jc43-05 -- -- -- -- -- -- -- --

391060075282801 Ie42-03 -- -- -- -- -- -- -- --

391747075364202 Hc34-03 -- -- -- -- -- -- -- --

393739075394202 Dc31-15 -- -- -- -- -- -- -- --

393916075440802 Db11-28 -- -- -- -- -- -- -- --

393928075440202 Db11-27 -- -- -- -- -- -- -- --

394102075334301 Cd42-18 -- -- -- -- -- -- -- --
46 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix F. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations are in micrograms per liter; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Volatile organic compounds

1,3-Dichlorobenzene

1,1-Dichloroethane

1,1-Dichloroethenecis-1,2-

Dichloroethene

Dichlorofluoromethane

Dichloromethane

1,4-Dichlorobenzene

1,2-Dichloropropane

382805075330301 Rd22-01 -- 0.135 E0.028 -- -- -- 0.187 --

383000075326001 Qd52-09 -- -- -- -- -- -- E0.035 --

383101075141101 Frankford4 -- -- -- -- -- -- -- --

383311075344401 Qd21-12 -- -- -- -- -- -- -- --

383713075085501 Pi32-15 -- -- -- -- -- -- -- --

383729075101601 Ph35-25 -- E 0.053 -- -- -- -- -- --

383732075191301 Pg31-12 -- -- -- -- -- E 0.016 --

383815075271001 Pe23-185 -- -- -- -- -- -- -- E0.071

383823075382101 Pc22-06 -- -- -- -- -- -- -- --

383914075080501 Pi12-11 -- -- -- -- -- -- -- --

384139075230101 Of42-01 -- E0.088 -- -- E1.327 -- --

384322075051101 Oi25-18 -- -- -- -- -- -- -- --

384326075050801 Oi25-19 -- -- -- -- -- -- -- --

384428075135501 Oh12-07 -- -- -- -- -- -- -- --

384428075355701 Oc15-11 -- -- -- -- -- -- -- --

384526075091601 Ni51-32 -- -- -- -- -- -- -- --

384818075354101 Nc25-37 -- -- -- -- -- -- -- --

384819075190101 Ng21-03 -- -- -- -- -- -- -- --

384856075151101 Ng25-04 -- -- -- -- -- -- -- --

385448075341801 Md11-04 -- -- -- -- -- -- -- --

385522075251802 Le55-09 -- -- -- -- -- -- -- --

390617075261901 Je55-01 0.166 -- -- -- -- -- 0.237 --

390652075370701 Jc43-05 -- -- -- 1.268 -- -- -- --

391060075282801 Ie42-03 -- -- -- -- -- -- -- --

391747075364202 Hc34-03 -- E0.066 0.236 -- -- -- -- --

393739075394202 Dc31-15 -- -- -- -- -- -- -- --

393916075440802 Db11-28 -- -- -- -- -- -- -- --

393928075440202 Db11-27 -- -- -- E0.053 -- -- -- --

394102075334301 Cd42-18 -- -- E0.031 -- -- -- -- --
Appendixes A–H 47

Appendix F. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations are in micrograms per liter; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Volatile organic compounds

Diisopropylether Methyl ethyl 

ketone 

Methyl 

tert-butyl 

ether

Methyl 

tert-pentyl 

ether

Styrene Tetrachloroethene

Tetrachloromethane

Tetrahydrofuran

382805075330301 Rd22-01 -- -- E0.096 -- -- E0.040 -- --

383000075326001 Qd52-09 -- -- -- -- -- -- -- --

383101075141101 Frankford4 E0.091 -- -- -- -- -- -- --

383311075344401 Qd21-12 -- -- -- -- -- -- -- --

383713075085501 Pi32-15 -- -- E0.069 -- -- -- -- --

383729075101601 Ph35-25 -- -- E0.028 -- -- -- -- --

383732075191301 Pg31-12 -- E0.441 -- -- -- E0.0196 E0.303

383815075271001 Pe23-185 -- -- -- -- 0.257 -- -- 2.113

383823075382101 Pc22-06 -- -- 0.835 -- -- -- -- --

383914075080501 Pi12-11 -- -- E0.082 -- -- -- -- --

384139075230101 Of42-01 -- -- -- -- -- 0.974 -- --

384322075051101 Oi25-18 -- -- 0.733 -- -- -- -- --

384326075050801 Oi25-19 -- -- 0.303 -- -- -- -- --

384428075135501 Oh12-07 -- -- -- -- -- -- -- --

384428075355701 Oc15-11 -- -- 0.205 -- -- -- -- --

384526075091601 Ni51-32 -- -- 0.134 -- -- E0.026 -- --

384818075354101 Nc25-37 -- -- 0.626 -- -- 1.616 -- --

384819075190101 Ng21-03 -- -- -- -- -- -- -- --

384856075151101 Ng25-04 -- -- -- -- -- -- -- --

385448075341801 Md11-04 -- -- 0.717 -- -- -- -- --

385522075251802 Le55-09 -- -- 0.751 -- -- 0.544 -- --

390617075261901 Je55-01 -- -- 0.913 E0.073 -- E0.090 -- --

390652075370701 Jc43-05 -- -- 1.845 E0.086 -- -- -- --

391060075282801 Ie42-03 -- -- -- -- -- -- -- --

391747075364202 Hc34-03 -- -- 2.554 E0.086 -- 0.855 -- --

393739075394202 Dc31-15 -- -- 0.267 -- -- E0.038 -- --

393916075440802 Db11-28 -- -- 0.966 -- -- 0.208 -- --

393928075440202 Db11-27 -- -- 0.298 -- -- 1.013 -- --

394102075334301 Cd42-18 E 0.034 -- 1.470 E0.031 -- 0.391 -- --
48 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix F. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations are in micrograms per liter; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Volatile organic compounds

Toluene Tribromomethane

1,2,4-Trichlorobenzene1,1,1-TrichloroethaneTrichloroethene

Trichlorofluoromethane

Trichloromethane

382805075330301 Rd22-01 -- -- -- -- E0.031 -- 0.106

383000075326001 Qd52-09 -- -- -- -- -- -- 0.184

383101075141101 Frankford4 -- -- -- -- -- -- --

383311075344401 Qd21-12 -- -- -- -- -- -- 0.103

383713075085501 Pi32-15 -- -- -- E0.021 -- -- 1.126

383729075101601 Ph35-25 -- -- -- -- -- -- 0.411

383732075191301 Pg31-12 -- 0.352 -- -- -- -- 0.325

383815075271001 Pe23-185 -- -- -- -- -- E0.026

383823075382101 Pc22-06 -- -- -- -- -- -- E0.020

383914075080501 Pi12-11 -- -- -- -- -- -- 0.242

384139075230101 Of42-01 E0.036 -- -- E0.030 E0.071 -- E0.074

384322075051101 Oi25-18 -- -- -- -- -- -- E0.076

384326075050801 Oi25-19 -- -- -- -- -- -- E0.607

384428075135501 Oh12-07 -- -- -- -- -- -- 0.499

384428075355701 Oc15-11 -- -- -- -- -- -- E0.091

384526075091601 Ni51-32 -- -- -- -- E0.015 -- E0.080

384818075354101 Nc25-37 -- 0.632 -- -- -- -- 0.136

384819075190101 Ng21-03 -- -- -- -- -- -- E0.043

384856075151101 Ng25-04 -- -- -- -- -- -- 0.630

385448075341801 Md11-04 -- -- -- -- -- -- E0.067

385522075251802 Le55-09 -- -- -- -- 0.229 -- --

390617075261901 Je55-01 -- -- E0.037 -- -- E0.029

390652075370701 Jc43-05 -- -- -- -- 0.581 -- 0.228

391060075282801 Ie42-03 -- -- -- -- -- E0.044

391747075364202 Hc34-03 -- -- -- 1.102 0.519 -- 0.131

393739075394202 Dc31-15 -- -- -- -- -- E0.020 0.380

393916075440802 Db11-28 -- -- -- -- -- -- 0.443

393928075440202 Db11-27 -- -- -- -- E0.090 -- 0.321

394102075334301 Cd42-18 -- -- -- E0.062 0.152 -- 0.325
Appendixes A–H 49

Appendix Ga. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Age dating: sulfur hexafluoride data.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; NOAA, National Oceanic and Atmospheric Administration; mL, milliliters; fmol/L, 

fentomoles per liter; °C, degrees Celsius; --, no data]

USGS site 

identification 

number

Sample 

number

DGS 

local well 

number

Sampling 

date

Sulfur hexafluoride (SF6) data

NOAA 

Scale 

(fmol/L)

Excess air 

(mL)

Recharge 

temperature 

(°C)

Recharge 

elevation 

(feet)

Estimated 

date of 

recharge1

Estimated 

age of 

groundwater1

(year)

382805075330301 1 Rd22-01 9/10/2008 0.58957 2.3 10.6 34 1983.0 25.7

382805075330301 2 Rd22-01 9/10/2008 0.60782 2.3 10.6 34 1983.5 25.2

382830075073601 1 Ri23-04 9/10/2008 0.99633 6 12.4 0 1985.5 23.2

382830075073601 2 Ri23-04 9/10/2008 0.88429 6 12.4 0 1984.5 24.2

383000075326001 1 Qd52-09 9/9/2008 0.88420 3.2 9.5 25 1986.0 22.7

383000075326001 2 Qd52-09 9/9/2008 1.33546 3.2 9.5 25 1990.5 18.2

383101075141101 1 Frankford 4 8/27/2008 0.40367 3.8 14.5 20 1979.5 29.2

383101075141101 2 Frankford 4 8/27/2008 0.41111 3.8 14.5 20 1979.5 29.2

383311075344401 1 Qd21-12 9/23/2008 0.87228 3.9 16.3 13 1987.0 21.7

383311075344401 2 Qd21-12 9/23/2008 0.73475 3.9 16.3 13 1985.0 23.7

383713075085501 1 Pi32-15 10/21/2008 0.76403 1.9 13.2 0 1986.5 22.3

383713075085501 2 Pi32-15 10/21/2008 0.81491 1.9 13.2 0 1987.5 21.3

383729075101601 1 Ph35-25 10/21/2008 0.87477 2.2 12.7 0 1987.5 21.3

383732075191301 1 Pg31-12 10/14/2008 1.39857 1.6 11.4 15 1993.5 15.3

383732075191301 2 Pg31-12 10/14/2008 1.26434 1.6 11.4 15 1992.0 16.8

383815075271001 1 Pe23-185 8/7/2008 0.19091 1.9 8.8 32 1974.0 34.6

383815075271001 2 Pe23-185 8/7/2008 0.18601 1.9 8.8 32 1974.0 34.6

383823075382101 1 Pc22-06 9/8/2008 1.54345 4.6 16.2 9 1993.0 15.7

383823075382101 2 Pc22-06 9/8/2008 0.79793 4.6 16.2 9 1985.5 23.2

383914075080501 1 Pi12-11 10/20/2008 1.10721 2.4 13.6 6 1990.5 18.3

383914075080501 2 Pi12-11 10/20/2008 1.16846 2.4 13.6 6 1991.0 17.8

384139075230101 1 Of42-01 9/9/2008 1.15175 2.7 14.2 34 1991.0 17.7

384139075230101 2 Of42-01 9/9/2008 0.48750 2.7 14.2 34 1982.0 26.7

384322075051101 1 Oi25-18 9/25/2008 2.07005 1.8 13.4 1 2001.0 7.7

384322075051101 2 Oi25-18 9/25/2008 1.98991 1.8 13.4 1 2000.5 8.2

384326075050801 1 Oi25-19 9/25/2008 1.63052 3 12.9 1 1994.5 14.2

384326075050801 2 Oi25-19 9/25/2008 1.52406 3 12.9 1 1993.5 15.2

384428075135501 1 Oh12-07 11/13/2008 1.22347 3.8 10.4 25 1989.0 19.9

384428075135501 2 Oh12-07 11/13/2008 0.75440 3.8 10.4 25 1984.0 24.9

384428075355701 1 Oc15-11 8/26/2008 0.54585 1.6 12.2 26 1983.5 25.2

384428075355701 2 Oc15-11 8/26/2008 0.57407 1.6 12.2 26 1984.0 24.7

384526075091601 1 Ni51-32 10/8/2008 0.44781 2.2 12.8 0 1981.5 27.3

384526075091601 2 Ni51-32 10/8/2008 0.48956 2.2 12.8 0 1982.0 26.8

384818075354101 1 Nc25-37 8/21/2008 0.96967 3 13 32 1988.0 20.6

384818075354101 2 Nc25-37 8/21/2008 1.47106 3 13 32 1993.0 15.6

384819075190101 1 Ng21-03 9/16/2008 0.53207 1.3 12.4 4 1983.5 25.2
50 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix Ga. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Age dating: sulfur hexafluoride data.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; NOAA, National Oceanic and Atmospheric Administration; mL, milliliters; fmol/L, 

fentomoles per liter; °C, degrees Celsius; --, no data]

USGS site 

identification 

number

Sample 

number

DGS 

local well 

number

Sampling 

date

Sulfur hexafluoride (SF6) data

NOAA 

Scale 

(fmol/L)

Excess air 

(mL)

Recharge 

temperature 

(°C)

Recharge 

elevation 

(feet)

Estimated 

date of 

recharge1

Estimated 

age of 

groundwater1

(year)

384819075190101 2 Ng21-03 9/16/2008 0.54356 1.3 12.4 4 1983.5 25.2

384856075151101 1 Ng25-04 9/17/2008 0.23269 2.8 8.5 0 1975.0 33.7

384856075151101 2 Ng25-04 9/17/2008 0.23337 2.8 8.5 0 1975.0 33.7

385448075341801 1 Md11-04 8/28/2008 1.19391 2.5 10.6 41 1990.0 18.7

385448075341801 2 Md11-04 8/28/2008 0.67789 2.5 10.6 41 1984.0 24.7

385522075251802 1 Le55-09 11/12/2008 1.05971 2.9 12.1 10 1989.0 19.9

385522075251802 2 Le55-09 11/12/2008 0.47403 2.9 12.1 10 1981.0 27.9

390617075261901 1 Je55-01 11/6/2008 3.25897 4 10.3 25 - - - -

390617075261901 2 Je55-01 11/6/2008 2.91202 4 10.3 25 - - - -

390652075370701 1 Jc43-05 8/5/2008 1.27289 3.9 14.3 45 1990.5 18.1

390652075370701 2 Jc43-05 8/5/2008 1.21453 3.9 14.3 45 1990.0 18.6

391060075282801 1 Ie42-03 8/19/2008 1.46191 3.5 13.5 3 1992.5 16.1

391060075282801 2 Ie42-03 8/19/2008 1.37572 3.5 13.5 3 1992.0 16.6

391747075364202 1 Hc34-03 9/2/2008 1.13423 2.5 15.2 32 1991.0 17.7

391747075364202 2 Hc34-03 9/2/2008 1.08487 2.5 15.2 32 1990.5 18.2

393739075394202 1 Dc31-15 10/7/2008 2.04715 2.3 13.5 5 2000.0 8.8

393739075394202 2 Dc31-15 10/7/2008 2.31614 2.3 13.5 5 2002.5 6.3

393916075440802 1 Db11-28 10/2/2008 2.35528 2.1 12.4 55 2003.0 5.8

393916075440802 2 Db11-28 10/2/2008 2.35932 2.1 12.4 55 2003.0 5.8

393928075440202 1 Db11-27 10/2/2008 1.93110 1.3 13.9 65 2001.5 7.3

393928075440202 2 Db11-27 10/2/2008 1.94034 1.3 13.9 65 2001.5 7.3

394102075334301 1 Cd42-18 10/7/2008 3.04283 3.5 14.7 20 - - - -

394102075334301 2 Cd42-18 10/7/2008 3.38003 3.5 14.7 20 - - - -

1

 Model ages corrected for excess air.
Appendix Gb. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through November, 2008—Age dating: 

dissolved gas data.[DGS, Delaware Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; --, no data; CH4, methane; CO2, carbon dioxide; N2, nitrogen; O2, oxygen; Ar, argon]

DGS 

local well 

number

Sampling 

date

Field 

temperature 

(°C)

Recharge 

elevation 

(feet)

Dissolved gas data

Comments Concentration (mg/L) Partial pressures at field temperatures (atmospheres)

CH4 CO2 N2 O2 Ar CH4 CO2 N2 O2 Ar

Rd22-01 9/10/2008 17.00 34.0 0.0087 100.2128 20.0875 1.0910 0.7148 0.000329 0.053231 0.9786 0.0232 0.01110Rd22-01 9/10/2008 17.00 34.0 0.0084 99.8936 20.0095 1.3580 0.7138 0.000320 0.053062 0.9748 0.0289 0.01109

Ri23-04 9/10/2008 15.50 -0.2 0.0109 64.5619 24.0141 0.2863 0.7506 0.000398 0.032735 1.1384 0.0059 0.01132Ri23-04 9/10/2008 15.50 -0.2 0.0102 63.9917 24.1814 0.2694 0.7511 0.000373 0.032445 1.1463 0.0056 0.01133

Qd52-09 9/9/2008 16.50 25.0 0.0013 62.5480 21.3505 2.3737 0.7479 0.000049 0.032717 1.0308 0.0501 0.01150Qd52-09 9/9/2008 16.50 25.0 0.0018 62.8038 21.4075 2.2745 0.7471 0.000067 0.032851 1.0336 0.0480 0.01149

Frankford 4 8/27/2008 15.50 20.0 0.9368 73.2647 22.5811 0.2411 0.6815 0.034350 0.037147 1.0704 0.0050 0.01028Frankford 4 8/27/2008 15.50 20.0 0.9399 73.8947 22.6952 0.2123 0.6838 0.034462 0.037467 1.0759 0.0044 0.01031

Qd21-12 9/23/2008 15.50 13.0 0.0000 44.3896 19.8792 1.9075 0.6640 0.000000 0.022507 0.9424 0.0394 0.01001Qd21-12 9/23/2008 15.50 13.0 0.0000 45.6913 19.7219 2.3957 0.6641 0.000000 0.023167 0.9349 0.0495 0.01001

Pi32-15 10/21/2008 14.50 -6.0 0.0000 51.6142 18.8927 0.4972 0.6724 0.000000 0.025355 0.8790 0.0101 0.00993Pi32-15 10/21/2008 14.50 -6.0 0.0000 48.7292 18.7874 4.1131 0.6720 0.000000 0.023938 0.8741 0.0833 0.00993

Ph35-25 10/21/2008 15.50 -3.0 0.0000 53.8325 19.2608 2.7115 0.6839 0.000000 0.027294 0.9131 0.0561 0.01031Ph35-25 10/21/2008 15.50 -3.0 0.0000 53.7814 19.1999 2.6350 0.6807 0.000000 0.027269 0.9102 0.0545 0.01026Pg31-12 10/14/2008 15.50 15.0 0.0000 38.4966 19.1450 3.9647 0.6922 0.000000 0.019519 0.9076 0.0820 0.01044Pg31-12 10/14/2008 15.50 15.0 0.0000 37.6421 19.0691 4.7004 0.6902 0.000000 0.019086 0.9040 0.0972 0.01041

Pe23-185 8/7/2008 24.00 32.0 0.6319 37.9154 20.4065 0.2714 0.7356 0.027519 0.024682 1.1157 0.0066 0.01298Pe23-185 8/7/2008 24.00 32.0 0.6459 38.2216 20.4172 0.2599 0.7395 0.028127 0.024881 1.1163 0.0063 0.01305

Pc22-06 9/8/2008 16.50 9.0 0.0000 45.8845 20.4104 1.9371 0.6749 0.000000 0.024001 0.9854 0.0409 0.01038Pc22-06 9/8/2008 16.50 9.0 0.0000 46.6216 20.4040 0.2544 0.6741 0.000000 0.024386 0.9851 0.0054 0.01037

Pi12-11 10/20/2008 14.00 6.0 0.0000 44.0289 19.2668 0.2391 0.6765 0.000000 0.021285 0.8879 0.0048 0.00989Pi12-11 10/20/2008 14.00 6.0 0.0000 40.6238 18.9027 3.1034 0.6692 0.000000 0.019639 0.8711 0.0622 0.00978

Of42-01 9/9/2008 16.50 34.0 0.0101 154.3689 20.7353 0.2405 0.6770 0.000377 0.080745 1.0011 0.0051 0.01041Of42-01 9/9/2008 16.50 34.0 0.0100 154.1243 19.6640 0.2413 0.6609 0.000376 0.080618 0.9494 0.0051 0.01017

Oi25-18 9/25/2008 15.50 1.0 0.0000 91.4324 18.6765 2.9556 0.6676 0.000000 0.046359 0.8854 0.0611 0.01007Oi25-18 9/25/2008 15.50 1.0 0.0000 88.1889 18.4988 2.7086 0.6640 0.000000 0.044714 0.8769 0.0560 0.01001Oi25-19 9/25/2008 15.00 1.0 0.0000 96.3512 20.1073 0.2417 0.6931 0.000000 0.048089 0.9444 0.0049 0.01035Oi25-19 9/25/2008 15.00 1.0 0.0000 99.3025 19.8207 0.2685 0.6925 0.000000 0.049562 0.9309 0.0055 0.01034

Oh12-07 11/13/2008 14.50 25.0 0.0000 30.0754 21.7041 5.4840 0.7451 0.000000 0.014774 1.0098 0.1111 0.01101Oh12-07 11/13/2008 14.50 25.0 0.0000 30.3703 21.6117 4.7638 0.7434 0.000000 0.014919 1.0055 0.0965 0.01098

Appendixes A–H 51
52 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08 Appendix Gb. Groundwater-quality data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through November, 2008—Age dating: dissolved gas data.—Continued [DGS, Delaware Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; --, no data; CH4, methane; CO2, carbon dioxide; N2, nitrogen; O2, oxygen; Ar, argon] DGS local well number Sampling date Field tempera- ture (°C) Recharge elevation (feet) Dissolved gas data Comments Concentration (mg/L) Partial pressures at field temperatures (atmospheres) CH4 CO2 N2 O2 Ar CH4 CO2 N2 O2 Ar Oc15-11 8/26/2008 16.00 26.0 0.0000 43.5592 18.7055 4.2949 0.6795 0.000000 0.022434 0.8949 0.0897 0.01035 Oc15-11 8/26/2008 16.00 26.0 0.0000 47.4307 18.9626 0.2457 0.6802 0.000000 0.024428 0.9072 0.0051 0.01036 Ni51-32 10/8/2008 15.00 -3.0 0.0000 45.7027 20.0689 0.2537 0.6774 0.000000 0.022810 0.9425 0.0052 0.01011 Ni51-32 10/8/2008 15.00 -3.0 0.0000 46.9392 20.3014 2.6958 0.6841 0.000000 0.023427 0.9535 0.0552 0.01021 Nc25-37 8/21/2008 18.00 32.0 0.0000 40.4983 20.7306 1.9072 0.7034 0.000000 0.022177 1.0279 0.0414 0.01114 Nc25-37 8/21/2008 18.00 32.0 0.0000 41.5356 18.9584 0.2124 0.6761 0.000000 0.022745 0.9401 0.0046 0.01071 Ng21-03 9/16/2008 15.00 4.0 0.0000 31.2095 18.4494 5.2418 0.6719 0.000000 0.015577 0.8665 0.1073 0.01003 Ng21-03 9/16/2008 15.00 4.0 0.0000 32.8372 18.3829 3.5046 0.6701 0.000000 0.016389 0.8634 0.0717 0.01000 Ng25-04 9/17/2008 15.50 -0.6 0.0000 37.7009 21.6460 3.0128 0.7630 0.000000 0.019115 1.0261 0.0623 0.01150 Ng25-04 9/17/2008 15.50 -0.6 0.0000 36.7198 21.3868 2.8705 0.7568 0.000000 0.018618 1.0138 0.0593 0.01141 Md11-04 8/28/2008 16.50 41.0 0.0000 71.9824 20.1331 4.1502 0.7139 0.000000 0.037652 0.9720 0.0875 0.01098 Md11-04 8/28/2008 16.50 41.0 0.0000 72.9209 20.3540 3.7288 0.7216 0.000000 0.038143 0.9827 0.0787 0.01110 Le55-09 11/12/2008 15.00 10.0 0.0000 50.1526 24.2301 0.3732 0.7040 0.000000 0.025031 1.1380 0.0076 0.01051 Le55-09 11/12/2008 15.00 10.0 0.0000 48.1338 24.0938 0.4144 0.7034 0.000000 0.024024 1.1316 0.0085 0.01050 Je55-01 11/6/2008 15.86 25.0 0.0000 139.7348 23.7339 0.6823 0.7450 0.000000 0.071652 1.1326 0.0142 0.01131 Je55-01 11/6/2008 15.86 25.0 0.0000 138.8549 24.1470 0.9299 0.7535 0.000000 0.071201 1.1523 0.0194 0.01144 Jc43-05 8/5/2008 16.00 45.0 0.0000 90.2122 20.6527 5.0703 0.6939 0.000000 0.046461 0.9881 0.1059 0.01057 Jc43-05 8/5/2008 16.00 45.0 0.0000 88.9382 19.9153 4.3215 0.6789 0.000000 0.045805 0.9528 0.0902 0.01034 Ie42-03 8/19/2008 15.50 3.0 0.0000 61.4376 23.1291 0.2584 0.6924 0.000000 0.031150 1.0964 0.0053 0.01044 Ie42-03 8/19/2008 15.50 3.0 0.0000 60.5011 23.3337 0.2679 0.6935 0.000000 0.030676 1.1061 0.0055 0.01046 Hc34-03 9/2/2008 15.50 32.0 0.0000 72.7466 20.2010 0.2424 0.6539 0.000000 0.036884 0.9576 0.0050 0.00986 Hc34-03 9/2/2008 15.50 32.0 0.0000 70.3832 20.1238 2.7503 0.6515 0.000000 0.035686 0.9540 0.0569 0.00982 Dc31-15 10/7/2008 13.50 5.0 0.0000 79.3186 19.1076 2.0357 0.6737 0.000000 0.037732 0.8721 0.0404 0.00975 Dc31-15 10/7/2008 13.50 5.0 -- -- -- -- -- -- -- -- -- -- Sample lost Db11-28 10/2/2008 17.00 55.0 0.0000 137.1960 19.2160 3.5000 0.6844 0.000000 0.072876 0.9361 0.0746 0.01063 No duplicate submitted Db11-27 10/2/2008 15.00 65.0 0.0000 105.6206 18.0066 0.2308 0.6519 0.000000 0.052715 0.8457 0.0047 0.00973 Db11-27 10/2/2008 15.00 65.0 0.0000 101.4155 17.9318 0.2379 0.6488 0.000000 0.050616 0.8422 0.0049 0.00968 Cd42-18 10/7/2008 15.00 20.0 0.0000 97.7822 19.7802 5.6107 0.6744 0.000000 0.048803 0.9290 0.1148 0.01007 Cd42-18 10/7/2008 15.00 20.0 0.0000 97.9240 19.8032 6.6744 0.6765 0.000000 0.048874 0.9301 0.1366 0.01010
Appendixes A–H 53

Appendix Ha. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Nutrients.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in milligrams per liter; E, estimated; <, less than; N, nitrogen]

USGS site 

identification 

number

DGS 

local 

well 

number

Sample 

type

Nutrients

Ammonia 

as N

Dissolved 

ammonia 

plus organic 

nitrogen 

as N

Total ammonia plus 

organic 

nitrogen 

as N

Nitrite plus 

nitrate 

as N

Nitrite 

as N

Dissolved 

phosphorus

Total 

phosphorus

382830075073601 Ri23-04 Blank <0.02 <0.14 <0.14 <0.04 <0.002 <0.006 <0.008

383713075085501 Pi32-15 Replicate <0.02 <0.1 <0.1 3.3 <0.002 E0.003 <0.012

384428075135501 Oh12-07 Blank <0.02 <0.1 <0.1 <0.04 <0.002 <0.006 <0.012

385448075341801 Md11-04 Replicate <0.02 E0.08 E0.08 8.19 <0.002 0.007 0.009

390652075370701 Jc43-05 Replicate <0.02 <0.14 <0.14 5.48 <0.002 <0.006 <0.008

Appendix Hb. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Major ions and trace elements.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; E, estimated; 

--, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Major ions and trace elements

Bromide 

(mg/L as Br)

Calcium 

(mg/L as 

Ca)

Chloride 

(mg/L as 

Cl)

Fluoride 

(mg/L as F)

Magnesium 

(mg/L as Mg)

Manganese 

(μg/L as Mn)

383713075085501 Pi32-15 Replicate 0.08 4.64 17.20 <0.08 2.77 6.94

383815075271001 Pe23-185 Replicate E0.019 E0.03 4.50 <0.12 <0.02 29.61

384428075135501 Oh12-07 Blank <0.02 <0.02 <0.12 <0.08 <0.012 <0.2

390652075370701 Jc43-05 Replicate 0.03 12.90 14.72 <0.12 4.46 25.16

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Major ions and trace elements

Potassium 

(mg/L as K)

Silica 

(mg/L as 

SiO2)

Sodium 

(mg/L)

Sulfate 

(mg/L as 

SO4)

Total 

Hardness (mg/L 

as CaCO3)

Total Iron 

(μg/L as Fe)

383713075085501 Pi32-15 Replicate 1.96 19.60 10.73 4.66 23.01 <4

383815075271001 Pe23-185 Replicate 0.04 29.35 25.92 0.40 -- E4.2

384428075135501 Oh12-07 Blank <0.06 <0.02 <0.12 <0.18 -- <4

390652075370701 Jc43-05 Replicate 1.96 26.31 9.88 25.56 50.57 252.5
54 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix Hc. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Pesticides.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter (μg/L); E, estimated; <, less than; 

--, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Acetochlor Alachlor Atrazine Benfluralin Butylate

383311075344401 Qd21-12 Replicate <0.006 <0.006 E0.005 <0.004 <0.002

384326075050801 Oi25-19 Blank <0.006 <0.006 <0.007 <0.004 <0.002

384818075354101 Nc25-37 Replicate <0.006 0.012 0.023 <0.004 <0.002

384856075151101 Ng25-04 Blank <0.006 <0.006 <0.007 <0.004 <0.002

391060075282801 Ie42-03 Replicate <0.02 < 0.02 -- -- --

393928075440202 Db11-27 Replicate <0.01 E0.0059 0.204 <0.004 0.002

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Carbaryl Carbofuran Chlorpyrifos Cyanazine Diazinon

383311075344401 Qd21-12 Replicate <0.06 <0.02 <0.005 <0.02 <0.005

384326075050801 Oi25-19 Blank <0.06 <0.02 <0.005 <0.02 <0.005

384818075354101 Nc25-37 Replicate <0.06 E0.019 <0.005 <0.02 <0.005

384856075151101 Ng25-04 Blank <0.06 <0.02 <0.005 <0.02 <0.005

391060075282801 Ie42-03 Replicate -- -- -- -- --

393928075440202 Db11-27 Replicate <0.2 <0.06 <0.01 <0.04 <0.005

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Dieldrin Dimethenamid Disulfoton Eptam

(Eptam) Ethalfluralin

383311075344401 Qd21-12 Replicate 0.017 <0.02 0.04 <0.002 <0.009

384326075050801 Oi25-19 Blank <0.009 <0.02 0.04 <0.002 <0.009

384818075354101 Nc25-37 Replicate <0.009 <0.02 0.04 <0.002 <0.009

384856075151101 Ng25-04 Blank <0.009 <0.02 0.04 <0.002 <0.009

391060075282801 Ie42-03 Replicate -- <0.02 -- -- --

393928075440202 Db11-27 Replicate 0.075 -- 0.04 0.009 <0.009
Appendixes A–H 55

Appendix Hc. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Pesticides.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; E, estimated; <, less than; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Ethoprop Fipronil Flufenacet Fonofos Glufosinate

383311075344401 Qd21-12 Replicate <0.012 0.02 <0.02 <0.01 <0.02

384326075050801 Oi25-19 Blank <0.012 <0.02 <0.02 <0.01 <0.02

384818075354101 Nc25-37 Replicate <0.012 <0.02 <0.02 <0.01 <0.02

384856075151101 Ng25-04 Blank <0.012 <0.02 <0.02 <0.01 <0.02

391060075282801 Ie42-03 Replicate -- -- <0.02 -- <0.02

393928075440202 Db11-27 Replicate <0.016 E0.018 -- <0.01 --

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Glyphosate alpha-HCH Lindane Linuron Malathion

383311075344401 Qd21-12 Replicate <0.02 <0.002 <0.006 <0.06 <0.016

384326075050801 Oi25-19 Blank <0.02 <0.002 <0.006 <0.06 <0.016

384818075354101 Nc25-37 Replicate <0.02 <0.002 <0.006 <0.06 <0.016

384856075151101 Ng25-04 Blank <0.02 <0.002 <0.006 <0.06 <0.016

391060075282801 Ie42-03 Replicate <0.02 -- -- -- --

393928075440202 Db11-27 Replicate -- E0.002 E0.006 <0.06 <0.02

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Metolachlor Metribuzin Molinate Napropamide Parathion

383311075344401 Qd21-12 Replicate 0.092 <0.012 <0.002 <0.018 <0.01

384326075050801 Oi25-19 Blank <0.01 <0.012 <0.002 <0.018 <0.01

384818075354101 Nc25-37 Replicate 0.056 <0.012 <0.002 <0.018 <0.01

384856075151101 Ng25-04 Blank <0.01 <0.012 <0.002 <0.018 <0.01

391060075282801 Ie42-03 Replicate <0.02 -- -- -- --

393928075440202 Db11-27 Replicate 0.055 <0.016 <0.002 <0.018 <0.02
56 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix Hc. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Pesticides.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; E, estimated; <, less than; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Parathion 

methyl Pebulate cisPermethrin Phorate Prometon Propachlor

383311075344401 Qd21-12 Replicate <0.008 <0.004 <0.01 <0.04 <0.008 <0.006

384326075050801 Oi25-19 Blank <0.008 <0.004 <0.01 <0.04 <0.008 <0.006

384818075354101 Nc25-37 Replicate <0.008 <0.004 <0.01 <0.04 E0.0055 <0.006

384856075151101 Ng25-04 Blank <0.008 <0.004 <0.01 <0.04 <0.008 <0.006

391060075282801 Ie42-03 Replicate -- -- -- -- -- <0.02

393928075440202 Db11-27 Replicate <0.008 E0.005 <0.014 <0.02 0.0124 <0.012

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Propanil Propargite Propyzamide Simazine Tebuthiuron

383311075344401 Qd21-12 Replicate <0.006 <0.04 <0.004 E0.004 <0.016

384326075050801 Oi25-19 Blank <0.006 <0.04 <0.004 <0.006 <0.016

384818075354101 Nc25-37 Replicate <0.006 <0.04 <0.004 <0.006 <0.016

384856075151101 Ng25-04 Blank <0.006 <0.04 <0.004 <0.006 <0.016

391060075282801 Ie42-03 Replicate -- -- -- -- --

393928075440202 Db11-27 Replicate <0.014 <0.02 <0.004 0.031 0.025

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticides

Terbacil Terbufos Thiobencarb Triallate Trifluralin

383311075344401 Qd21-12 Replicate <0.018 <0.018 <0.01 <0.006 <0.006

384326075050801 Oi25-19 Blank <0.018 <0.018 <0.01 <0.006 <0.006

384818075354101 Nc25-37 Replicate <0.018 <0.018 <0.01 <0.006 <0.006

384856075151101 Ng25-04 Blank <0.018 <0.018 <0.01 <0.006 <0.006

391060075282801 Ie42-03 Replicate -- -- -- -- --

393928075440202 Db11-27 Replicate <0.04 0.018 <0.016 <0.006 <0.012
Appendixes A–H 57

Appendix Hd. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Pesticide degradates. 

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; ESA, ethanesulfonic acid; OA, oxanilic acid; 

SA, second amide; SAA, sulfinyl acetic acid; E, estimated; <, less than; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticide degradates

Acetochlor 

SA

Acetochlor 

ESA

Acetochlor 

OA

Acetochlor 

SAA Alachlor SA Alachlor ESA SA

383311075344401 Qd21-12 Replicate <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

384326075050801 Oi25-19 Blank <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

384818075354101 Nc25-37 Replicate <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

384856075151101 Ng25-04 Blank <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

391060075282801 Ie42-03 Replicate <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

393928075440202 Db11-27 Replicate -- -- -- -- -- --

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticide degradates

Alachlor 

ESA

Alachlor 

OA

Alachlor 

SA

Aminomethylphosphonic 

acid

DCPA 

(Clorthaldimethyl)Deethyltrazine 

383311075344401 Qd21-12 Replicate 0.2 0.02 <0.02 <0.02 <0.003 E0.013

384326075050801 Oi25-19 Blank <0.02 <0.02 <0.02 <0.02 <0.003 <0.014

384818075354101 Nc25-37 Replicate 0.59 0.16 <0.02 <0.02 <0.003 E0.079

384856075151101 Ng25-04 Blank <0.02 <0.02 <0.02 <0.02 <0.003 <0.014

391060075282801 Ie42-03 Replicate 0.35 0.02 <0.02 <0.02 -- --

393928075440202 Db11-27 Replicate -- -- -- -- <0.006 E0.166

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticide degradates

DechlorodimethenamideDesulfinylfipronilamide

DechloroacetochlorDechloroalachlorDechlorometolachlorDesulfinylfipronil

383311075344401 Qd21-12 Replicate <0.02 <0.029 <0.02 <0.02 <0.02 <0.012

384326075050801 Oi25-19 Blank <0.02 <0.029 <0.02 <0.02 <0.02 <0.012

384818075354101 Nc25-37 Replicate <0.02 <0.029 <0.02 <0.02 <0.02 <0.012

384856075151101 Ng25-04 Blank <0.02 <0.029 <0.02 <0.02 <0.02 <0.012

391060075282801 Ie42-03 Replicate <0.02 -- <0.02 <0.02 <0.02 --

393928075440202 Db11-27 Replicate -- <0.029 -- -- -- <0.012
58 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix Hd. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Pesticide degradates.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; ESA, ethanesulfonic acid; OA, oxanilic acid; 

SA, second amide; SAA, sulfinyl acetic acid; E, estimated; <, less than; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticide degradates

2,6-DiethylanilineDimethenamid ESADimethenamid OA

2-[(2-Ethyl-6-

methylphenyl)

amino]-2-

oxoESA

Fipronil 

sulfide Fipronil sulfone

383311075344401 Qd21-12 Replicate <0.002 <0.02 <0.02 0.04 <0.013 <0.024

384326075050801 Oi25-19 Blank <0.002 <0.02 <0.02 <0.02 <0.013 <0.024

384818075354101 Nc25-37 Replicate <0.002 <0.02 <0.02 0.02 <0.013 <0.024

384856075151101 Ng25-04 Blank <0.002 <0.02 <0.02 <0.02 <0.013 <0.024

391060075282801 Ie42-03 Replicate - - <0.02 <0.02 0.03 - - - -

393928075440202 Db11-27 Replicate <0.006 - - - - - - E0.001 E0.004

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticide degradates

Flufenacet 

ESA

Flufenacet 

OA

HydroxyacetochlorHydroxyalachlor

Hydroxydimethenamid

Hydroxymetolachlor

383311075344401 Qd21-12 Replicate <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

384326075050801 Oi25-19 Blank <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

384818075354101 Nc25-37 Replicate <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

384856075151101 Ng25-04 Blank <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

391060075282801 Ie42-03 Replicate <0.02 <0.02 <0.02 <0.02 <0.02 <0.02

393928075440202 Db11-27 Replicate - - - - - - - - - - - -

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Pesticide degradates

Metolachlor ESAMetolachlor OAPendimethalin p,p’-DDE Propachlor 

ESA Propachlor OA

383311075344401 Qd21-12 Replicate 1.24 0.61 <0.012 <0.003 <0.05 <0.02

384326075050801 Oi25-19 Blank <0.02 <0.02 <0.012 <0.003 <0.05 <0.02

384818075354101 Nc25-37 Replicate 3.43 0.31 <0.012 <0.003 <0.05 <0.02

384856075151101 Ng25-04 Blank <0.02 <0.02 <0.012 <0.003 <0.05 <0.02

391060075282801 Ie42-03 Replicate 2.25 0.28 - - - - <0.05 <0.02

393928075440202 Db11-27 Replicate - - - - <0.012 <0.003 - - - -
Appendixes A–H 59

Appendix He. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; <, less than; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

Acetone Acrylonitrile Benzene Bromobenzene Bromochloromethane

382805075330301 Rd22-01 Replicate <4 <0.4 <0.016 <0.02 <0.06

384326075050801 Oi25-19 Blank <4 <0.4 <0.045 <0.02 <0.06

384818075354101 Nc25-37 Replicate <4 <0.4 <0.02 <0.02 <0.06

385522075251802 Le55-09 Blank 6.9 <0.4 <0.057 <0.02 <0.06

390617075261901 Je55-01 Blank <4 <0.4 <0.016 <0.02 <0.06

391747075364202 Hc34-03 Replicate <4 <0.4 <0.02 <0.02 <0.06

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

Bromodichloromethane Bromoethene Bromomethane n-Butylbenzene sec-Butylbenzene

382805075330301 Rd22-01 Replicate <0.04 <0.12 <0.4 <0.14 <0.04

384326075050801 Oi25-19 Blank <0.04 <0.12 <0.4 <0.14 <0.04

384818075354101 Nc25-37 Replicate 0.373 <0.12 <0.4 <0.14 <0.04

385522075251802 Le55-09 Blank <0.052 <0.12 <0.4 <0.08 <0.02

390617075261901 Je55-01 Blank E0.045 <0.12 <0.4 <0.08 <0.02

391747075364202 Hc34-03 Replicate <0.04 <0.12 <0.4 <0.14 <0.04

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

trans-ButylbenzeneEthyl-tertButyl etherButyl methyl 

ketone Carbon disulfide Chlorobenzene

382805075330301 Rd22-01 Replicate <0.06 <0.04 <0.6 <0.06 0.156

384326075050801 Oi25-19 Blank <0.06 <0.04 <0.6 <0.06 <0.02

384818075354101 Nc25-37 Replicate <0.06 <0.04 <0.6 <0.06 <0.02

385522075251802 Le55-09 Blank <0.06 <0.04 <0.6 <0.04 <0.02

390617075261901 Je55-01 Blank <0.06 <0.04 <0.6 <0.04 <0.02

391747075364202 Hc34-03 Replicate <0.06 <0.04 <0.6 <0.06 <0.02
60 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix He. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; <, less than; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

Chloroethane Chloromethane

3-Chloropropene

2-Chlorotoluene 4-Chlorotoluene

382805075330301 Rd22-01 Replicate <0.1 <0.1 <0.08 <0.04 <0.04

384326075050801 Oi25-19 Blank <0.1 <0.1 <0.08 <0.04 <0.04

384818075354101 Nc25-37 Replicate <0.1 <0.1 <0.08 <0.04 <0.04

385522075251802 Le55-09 Blank <0.1 <0.14 <0.08 <0.02 <0.02

390617075261901 Je55-01 Blank <0.1 <0.14 <0.08 <0.02 <0.02

391747075364202 Hc34-03 Replicate <0.1 <0.1 <0.08 <0.04 <0.04

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

DibromochloromethaneDibromochloropropane1,2-DibromoethaneDibromomethanetrans-1,3-Dichloropropene

382805075330301 Rd22-01 Replicate <0.12 <0.5 <0.04 <0.04 <0.1

384326075050801 Oi25-19 Blank <0.12 <0.5 <0.04 <0.04 <0.1

384818075354101 Nc25-37 Replicate 0.82 <0.5 <0.04 <0.04 <0.1

385522075251802 Le55-09 Blank <0.12 <1 <0.04 <0.04 <0.1

390617075261901 Je55-01 Blank <0.12 <1 <0.04 <0.04 <0.1

391747075364202 Hc34-03 Replicate <0.12 <0.5 <0.04 <0.04 <0.1

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

trans-1,4-

Dichloro-2-

butene

1,2-Dichlorobenzene1,3-Dichlorobenzene1,4-Dichlorobenzene1,1-Dichloroethane

382805075330301 Rd22-01 Replicate <0.6 0.391 <0.04 0.2056 0.12

384326075050801 Oi25-19 Blank <0.6 <0.02 <0.04 <0.02 <0.04

384818075354101 Nc25-37 Replicate <0.6 <0.02 <0.04 <0.02 <0.04

385522075251802 Le55-09 Blank <0.4 <0.02 <0.02 <0.02 <0.04

390617075261901 Je55-01 Blank <0.4 <0.02 <0.02 <0.02 <0.04

391747075364202 Hc34-03 Replicate <0.6 <0.02 <0.04 <0.02 E0.06
Appendixes A–H 61

Appendix He. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; <, less than; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

1,2-Dichloroethane1,1-Dichloroethenecis-1,2-Dichloroethenetrans-1,2-DichloroetheneDichlorofluoromethane

382805075330301 Rd22-01 Replicate <0.06 E0.03 <0.02 <0.02 <0.14

384326075050801 Oi25-19 Blank <0.07 <0.02 <0.02 <0.02 <0.14

384818075354101 Nc25-37 Replicate <0.06 <0.02 <0.02 <0.02 <0.14

385522075251802 Le55-09 Blank 0.28 <0.02 <0.02 <0.018 <0.1

390617075261901 Je55-01 Blank <0.06 <0.02 <0.02 <0.018 <0.1

391747075364202 Hc34-03 Replicate <0.06 0.22 <0.02 <0.02 <0.14

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

Dichloromethane1,2-Dichloropropane1,3-Dichloropropane2,2-Dichloropropane1,1-Dichloropropene

382805075330301 Rd22-01 Replicate <0.04 <0.02 <0.06 <0.06 <0.04

384326075050801 Oi25-19 Blank <0.04 <0.02 <0.06 <0.06 <0.04

384818075354101 Nc25-37 Replicate <0.04 <0.02 <0.06 <0.06 <0.04

385522075251802 Le55-09 Blank E0.097 <0.02 <0.06 <0.06 <0.04

390617075261901 Je55-01 Blank <0.04 <0.02 <0.06 <0.06 <0.04

391747075364202 Hc34-03 Replicate <0.04 <0.02 <0.06 <0.06 <0.04

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

cis-1,3-

DichloropropeneDiethylether Diisopropylether Ethylbenzene Ethylmethylacrylate

382805075330301 Rd22-01 Replicate <0.1 <0.12 <0.06 <0.04 <0.14

384326075050801 Oi25-19 Blank <0.1 <0.12 <0.06 <0.04 <0.14

384818075354101 Nc25-37 Replicate <0.1 <0.12 <0.06 <0.04 <0.14

385522075251802 Le55-09 Blank <0.1 <0.13 <0.06 <0.04 <0.14

390617075261901 Je55-01 Blank <0.1 <0.12 <0.06 <0.04 <0.14

391747075364202 Hc34-03 Replicate <0.1 <0.12 <0.06 <0.04 <0.14
62 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix He. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; <, less than; E, estimated; --, not detected]

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

Ethyl-methylketone2-Ethyltoluene Iodomethane Isobutyl-methyl 

ketone Isodurene

382805075330301 Rd22-01 Replicate <1.6 <0.04 <0.4 <0.4 <0.12

384326075050801 Oi25-19 Blank 4.51 <0.04 <0.4 <0.4 <0.12

384818075354101 Nc25-37 Replicate <1.6 <0.04 <0.4 <0.4 <0.12

385522075251802 Le55-09 Blank 31.61 <0.02 <0.8 <0.4 <0.08

390617075261901 Je55-01 Blank <1.6 <0.02 <0.8 <0.4 <0.08

391747075364202 Hc34-03 Replicate <1.6 <0.04 <0.4 <0.4 <0.12

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

Isopropylbenzene4-IsopropyltolueneHexachlorobutadieneHexachloroethane Methacrylonitrile

382805075330301 Rd22-01 Replicate <0.04 <0.08 <0.06 <0.14 <0.2

384326075050801 Oi25-19 Blank <0.04 <0.08 <0.06 <0.14 <0.2

384818075354101 Nc25-37 Replicate <0.04 <0.08 <0.06 <0.14 <0.2

385522075251802 Le55-09 Blank <0.04 <0.06 <0.06 <0.14 <0.2

390617075261901 Je55-01 Blank <0.04 <0.06 <0.06 <0.14 <0.2

391747075364202 Hc34-03 Replicate <0.04 <0.08 <0.06 <0.14 <0.2

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

MethylacrylateMethyl methacrylateMethyl-tertpentyl etherMethyl-tertbutyl ether n-Propylbenzene

382805075330301 Rd22-01 Replicate <0.6 <0.2 <0.06 E0.096 <0.04

384326075050801 Oi25-19 Blank <0.6 <0.2 <0.06 0.173 <0.04

384818075354101 Nc25-37 Replicate <0.6 <0.2 <0.06 0.628 <0.04

385522075251802 Le55-09 Blank <0.6 <0.2 <0.06 0.778 <0.04

390617075261901 Je55-01 Blank <0.6 <0.2 <0.06 <0.1 <0.04

391747075364202 Hc34-03 Replicate <0.6 <0.2 E0.07 2.470 <0.04
Appendixes A–H 63

Appendix He. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; <, less than; E, estimated; --, not detected]

USGS site 

identification 

number

DGS

 local well 

number

Sample type

Volatile organic compounds

Naphthalene

Prehnitene 

(1,2,3,4-tetramethylbenzene)Styrene Tetrachloroethene

Tetrachloromethane

382805075330301 Rd22-01 Replicate <0.2 <0.14 <0.04 E0.04146 <0.08

384326075050801 Oi25-19 Blank <0.2 <0.14 <0.04 <0.04 <0.08

384818075354101 Nc25-37 Replicate <0.2 <0.14 <0.04 1.611 <0.08

385522075251802 Le55-09 Blank <0.2 <0.08 <0.04 <0.04 <0.06

390617075261901 Je55-01 Blank <0.2 <0.08 <0.04 <0.04 <0.06

391747075364202 Hc34-03 Replicate <0.2 <0.14 <0.04 0.852 <0.08

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

Tetrahydrofuran Toluene 1,1,1,2-Tetrachloroethane1,1,2,2-TetrachloroethaneTribromomethane

382805075330301 Rd22-01 Replicate <1.4 <0.02 <0.04 <0.1 <0.08

384326075050801 Oi25-19 Blank <1.4 <0.02 <0.04 <0.1 <0.08

384818075354101 Nc25-37 Replicate <1.4 <0.02 <0.04 <0.1 0.6

385522075251802 Le55-09 Blank E0.772 E0.026 <0.04 <0.1 <0.1

390617075261901 Je55-01 Blank <1.4 <0.018 <0.04 <0.1 <0.1

391747075364202 Hc34-03 Replicate <1.4 <0.02 <0.04 <0.1 <0.08

USGS site 

identification 

number

DGS 

local well 

number

Volatile organic compounds

Sample type 1,2,3-Trichlorobenzene

1,2,4-Trichlorobenzene1,1,1-Trichloroethane1,1,2-TrichloroethaneTrichloroethene

382805075330301 Rd22-01 Replicate <0.08 <0.08 <0.02 <0.06 E0.027

384326075050801 Oi25-19 Blank <0.08 <0.08 <0.02 <0.06 <0.02

384818075354101 Nc25-37 Replicate <0.08 <0.08 <0.02 <0.06 <0.02

385522075251802 Le55-09 Blank <0.06 <0.04 <0.02 <0.06 <0.02

390617075261901 Je55-01 Blank <0.06 <0.04 <0.02 <0.06 <0.02

391747075364202 Hc34-03 Replicate <0.08 <0.08 1.04 <0.06 0.52
64 Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer, DE, 2000–08

Appendix He. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Volatile organic compounds.—Continued

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all concentrations in micrograms per liter; <, less than; E, estimated; --, not detected]

USGS site

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

TrichlorofluoromethaneTrichloromethane1,2,3-Trichloropropane1,1,2-Trichlorotrifluoromethane1,2,3-Trimethylbenzene

382805075330301 Rd22-01 Replicate <0.08 E0.0990 <0.12 <0.04 <0.08

384326075050801 Oi25-19 Blank <0.08 0.1375 <0.12 <0.04 <0.08

384818075354101 Nc25-37 Replicate <0.08 0.1416 <0.12 <0.04 <0.08

385522075251802 Le55-09 Blank <0.08 0.3504 <0.12 <0.04 <0.08

390617075261901 Je55-01 Blank <0.08 0.1251 <0.12 <0.04 <0.08

391747075364202 Hc34-03 Replicate <0.08 0.1228 <0.12 <0.04 <0.08

USGS site 

identification 

number

DGS 

local well 

number

Sample type

Volatile organic compounds

1,2,4-Trimethylbenzene1,3,5-Trimethylbenzene Vinyl chloride m-p-Xylene o-Xylene

382805075330301 Rd22-01 Replicate <0.04 <0.04 <0.08 <0.08 <0.04

384326075050801 Oi25-19 Blank <0.04 <0.04 <0.08 <0.08 <0.04

384818075354101 Nc25-37 Replicate <0.04 <0.04 <0.08 <0.08 <0.04

385522075251802 Le55-09 Blank <0.04 <0.04 <0.08 <0.08 <0.04

390617075261901 Je55-01 Blank <0.04 <0.04 <0.08 <0.08 <0.04

391747075364202 Hc34-03 Replicate <0.04 <0.04 <0.08 <0.08 <0.04

Appendix Hf. Quality-control data for sampled public water-supply wells in the Columbia aquifer in Delaware, August through 

November, 2008—Radiochemical activities.

[USGS, U.S. Geological Survey; DGS, Delaware Geological Survey; all activities are in picocuries per liter; <, less than; --, not detected]

USGS site 

identification number

DGS 

local well number Sample type

Radiochemical activities

Radium-226 Radium-228 Radon-222

383815075271001 Pe23-185 Replicate <0.01 <-0.03 58.5

391747075364202 Hc34-03 Blank -- -- <3.2

391747075364202 Hc34-03 Replicate 0.47 0.8 --
Prepared by USGS West Trenton Publishing Service Center.

Edited by Valerie M. Gaine.

Graphics and layout by Timothy W. Auer.

For additional information, contact:

Director, MD-DE-DC Water Science Center

U.S. Geological Survey

5522 Research Park Drive

Baltimore, MD 21228

or visit our Web site at:

http://md.water.usgs.gov
Reyes, B.—Organic Chemicals, Nutrients, and Water-Quality Data from Public Drinking-Water Supplies in the Columbia Aquifer in Delaware, 2000–08—Scientific Investigations Report 2010–5206

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