ARSENIC, NITRATE, AND CHLORIDE IN GROUNDWATER, PONTIAC TOWNSHIP,

OAKLAND COUNTY, MICHIGAN

Protection Agency. The maps were based on historical data

from records compiled by the Michigan Department of

Environmental Quality (MDEQ). The USGS collected and

analyzed samples to test the water quality in a number of these

wells to confirm the overall validity of the historical records.

The maps showed that each of the chemical constituents is

widely distributed. High concentrations of arsenic are most

INTRODUCTION

The U.S. Geological Survey (USGS) and the Center for Applied

Environmental Research at the University of Michigan-Flint (CAER)

mapped distributions of arsenic, nitrate, and chloride in the

groundwater of Oakland County. Emphasis was placed on sites that

exceeded Maximum Contaminant Levels (MCL) and Secondary

Maximum Contaminant Levels (SMCL) set by the U.S. Environmental

HOW TO USE THE TOWNSHIP MAP

Carefully review the map to find the approximate location of your home. If you find that your home is in one of the areas

highlighted on the map, the Oakland County Health Division (OCHD) recommends that you obtain a water sample from your well

to test for the contaminants indicated for that area.

Homeowners with a well are, in effect, running their own small water utility. The best way to assure a

safe drinking-water supply anywhere in Oakland County is to have water samples analyzed regularly by a certified public or

private laboratory. The OCHD can analyze samples for nitrate and chloride levels and

also provide a list of certified private laboratories in the area who can test your water.

Contact the OCHD for information on obtaining sample bottles and procedures

for collecting a sample.

Arsenic tests are conducted by the MDEQ.

C AE R enter for pplied nvironmental esearch

University of Michigan-Flint

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 150-98

December 1998

6

5

8 7

18

17

3 4

9

10

16

15

22

21 20

30

31 32 33 34

27

28 29

19

25

26

35

13

14

24 23

12 11

2

1

36

AUBURN AVE.

ORCHARD LAKE AVE.

JOSLYN A VE.

UNIVERSITY DR.

WALTON BLVD.

TAYLOR RD.

COLLIER RD.

ANGELUS RD.

BROWN RD. GIDDINGS RD.

GREY RD.

OPDYKE RD.

DORIS RD.

UNIVERSITY

PONTIAC RD.

SHIMMONS RD.

SQU RI REL R D.

BALD M OUNTA NI R D.

FEATHERSTONE RD.

DR.

SOUTH BLVD.

BARNETT RD.

PONTIAC/AUBURN HILLS

Area with public water

available

Public Water Availability in

Pontiac/Auburn Hills

WATER QUALIT WATER QUALITY

City, village,

township boundaries

Section lines

Lake Angelus

Arsenic, nitrate, 

and chloride above MCL

Arsenic and nitrate

above MCL

Arsenic above MCL

Arsenic and chloride

above MCL

No observations

(see table)

Nitrate above MCL

Chloride above SMCL

Nitrate and chloride

above MCL

Shaded sections are within one quarter mile 

of an observation greater than the EPA 

Maximum Contaminant Level (MCL) 

for either arsenic, nitrate, or chloride

Arsenic (Primary MCL=0.05 mg/l), 

Nitrate (Primary MCL=10 mg-N/l), and 

Chloride (Secondary MCL=250 mg/l)

are the contaminants included.

PONTIAC

LAKE

ANGELUS

AUBURN HILLS

1559

,.-75

/(244

SOURCES: Michigan Department of Environmental Quality 1983-1997 (excluding 1991-92)

 Michigan Department of Natural Resources, Michigan Resource Information System (MIRIS), 1978

 Oakland County GIS Utility, 1997

1524

0 1 KILOMETER

0

N

1 MILE

Sections with: Arsenic Nitrate Chloride

No observations 3,4,7,8,11-24,

27-32,34-36

4,13,15,16,22-

24,27,29,33

4,13,15,22-24,

27,29,33

Observations, but

no detectable

contaminant

25,33 2,5,9,11,12,19,

20,25

2,11,12

Observations

below MCL

1,2,5,6,9,10,25,

26

1-3,5-12,14,17,

18,20,21,25,26,

28,30-32,34-36

1-3,5-12,14,16-

21,25,26,28,

30-32,34-36
common in the northern and northwestern parts of the county. Nitrate

has been detected in groundwater in most townships but samples with

concentrations above the MCL tend to cluster around high-density

lakeshore communities. Chlorides are the most widely distributed and

samples with concentrations above the SMCL also cluster in highdensity lakeshore communities.

To provide homeowners with more detailed information on the

distribution of these water-quality indicators, a series of township maps

have been prepared. These maps highlight square-mile sections that

contain, or are close to, wells in which concentrations of arsenic,

nitrate, or chloride greater than the (S)MCL have been detected.

The MDEQ maintains a database of results from water-quality tests

conducted for homeowners and businesses. In this study, maps were

prepared from records of tests in Oakland County where arsenic, nitrate

and chloride measurements were made. The data spanned the years

from 1988 through 1997 (excluding 1991-92).

Addresses for each of the records were matched to an Oakland County

road file through an address-matching procedure in a Geographic

Information System. All sites with arsenic concentrations greater than

the MCL were mapped. For nitrate and chloride, the success rates were

94 percent and 81 percent, respectively. Data coverage for all the

chemical constituents was extensive, although the distribution of test

results for arsenic was least concentrated in the southeastern part of the

county, where public water supply is most available.

HOW WERE THE MAPS PREPARED?

The township maps were prepared using the address-matched

database and a detailed base map which included residential

roads. Square mile sections were highlighted if they contained

a well with a measurement higher than the (S)MCL for each

constituent or were within a 1⁄4-mile of one of these wells.

These sections were shaded to indicate the multiple

combinations of (S)MCL exceedances that were possible.

The USGS collected water samples across Oakland County at

selected sites with previous analyses for arsenic, nitrate or

chloride. Each new sample was collected using clean

sampling techniques to minimize the risk of contamination.

Duplicate samples were sent to both the MDEQ laboratory and

the USGS National Water Quality Laboratory (NWQL) in

Denver, Colorado. Results from the USGS NWQL were

compared against the results from MDEQ and against results

from the previous samples. The results from the MDEQ

laboratory agreed very closely with the results from the USGS

NWQL. This sample testing confirmed the validity of using

the MDEQ database in maps prepared for the study.

HOW WERE THE SAMPLE DATA COLLECTED

AND EVALUATED?

by Steve Aichele (USGS), Richard Hill-Rowley (CAER), and

Matt Malone (CAER)

Oakland County Health Division

1200 N. Telegraph Road

Pontiac, MI 48341-0432

(248) 858-1312

http://www.co.oakland.mi.us

U.S. Geological Survey,

Water Resources Division

6520 Mercantile Way, Ste. 5

Lansing, MI 48911

(517) 887 - 8903

http://wwwdmilns.er.usgs.gov

Center for Applied Environmental Research

University of Michigan - Flint

Room 529 Murchie Science Bldg.

Flint, MI 48502-2186

(810) 766-6608

http://www.umf-outreach.edu

C AE R enter for pplied nvironmental esearch

University of Michigan-Flint

For more information, contact:

WHAT CAN I DO IF I HAVE ARSENIC, NITRATE, OR CHLORIDE IN MY WATER?

You may wish to have an additional sample collected to confirm the results of the first test. If your drinking water contains

concentrations of arsenic or nitrate above the MCL, MDEQ and the OCHD recommend that you stop using the contaminated

water for drinking and preparing food. Bottled water is a possible temporary solution. Neither arsenic nor nitrate pose a health

risk through skin exposure, so the contaminated water can still be used for washing, laundry, and other household uses. Chloride

is not generally considered to be a health concern.

Long-term solutions for high arsenic or nitrate concentrations include connecting to a public water supply, modifying the

existing well or installing a new well, installing a treatment device such as a Reverse Osmosis (RO) filter, or using bottled water

indefinitely. Chloride concentrations are a less serious concern than those associated with arsenic and nitrate and connecting to a

public water supply or installing a treatment device such as a RO filter are the primary solutions.

Because treatment devices require regular maintenance to remain effective, MDEQ and Oakland County both recommend

obtaining a new source of drinking water, either by connecting to a public water supply or, where high arsenic or nitrate

concentrations are a concern, by drilling a new well.

The OCHD can provide additional information and advice on a solution to fit your needs.