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Chemical Monitoring

This is a photo of the field test kit.

Is it safe to go in the water?

Jaws may not be lurking in a deep pool in our backyard stream, but what is in there? Long gone are the days when you could just fling off your cowboy hat and help yourself to a drink from the nearby stream on a hot summer day. But thanks to the Clean Water Act, gone too are the days when rivers were so polluted that they posed a fire hazard. Results of EPS's monitoring are published annually in its National Pollutant Discharge Elimination System NPDES report.

Baltimore County Department of Environmental Protection and Sustainability (EPS) monitors 40 sites monthly for chemical conditions. A sudden rain shower might flush nutrients and bacteria from nearby agriculture into the stream. Our roads act like conduits for pollution in shopping areas and urban neighborhoods.  Wildlife, pets, and a failing septic tank will contribute pollutants intermittently so that what’s in the water is constantly changing. This is why monitoring the water on a regular basis is important.

Water samples are collected from selected stream sites using small sterile containers. Just as your doctor doesn’t test you for every known disease, EPS conducts nineteen tests for pollutants that are prevalent in streams or are listed by the United States Environmental Protection Agency. Nineteen items are a lot to think about so we often divide them into categories.


The tests for nutrients include nitrogen and phosphorus. Nutrients are chemicals that are vital to growth in plants. Too many nutrients results in the growth of large quantities of algae. Algae can cause algal blooms in the bay and create problems with oxygen levels, water clarity, and contribute to dead zones. Several different forms of nitrogen and phosphorus are tested for in order to get a complete understanding of how much of the chemicals are in the system. Sources of nutrients include fertilizers, sewage, wildlife, agriculture, and atmospheric pollutants.


The problems of water clarity and oxygen levels that nutrients in the stream can cause are also measured in other ways. Total Suspended Solids and Total Solids are measured to provide a measure of the clarity of the water. Biological Oxygen Demand (BOD) indicates the amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water. Chemical Oxygen Demand (COD) indicates the amount of oxygen that is needed to oxidize reactive chemicals in water.

Heavy Metals

Heavy metals are also a concern. Cadmium, Copper, Zinc and Lead are the metals tested for in the collected water samples. Heavy metals are generally toxic to both wildlife and humans and can cause a variety of problems. The metals often sink into the sediments in the bottom of streams and lakes and are particular problems for aquatic life that lives there. These metals can accumulate in some species of fish that people like to eat. The metals can impact human health.

How We Use the Data

Baltimore County combines the data from chemical monitoring with information gathered from observing the physical conditions of the stream and from biological surveys to help provide a more complete picture regarding the condition of our waterways. All the data together can help identify the streams that are at risk and contribute to creating an informed plan to reduce pollutants and improve water quality.

To help further understand the condition of the stream, measurements of temperature, pH and the volume of water flowing are taken.

All of these tests are also examined with biological monitoring conducted and studies made of the physical conditions of the streams. By combining each of these, we have a clearer understanding of the health of the waterways.

Pollution Misconceptions

Foam can occur naturally in streams when dissolved organic compounds act as surfactants. They reduce the surface tension of the surface film of water. This allows fine bubbles and froth to form, accumulate on the surface, and be moved into calm areas by wind and water currents. A good way to tell if it’s natural or man-made is the smell. Natural foam usually has an earthy or fishy smell, where as the man-made detergent foam has more of a perfume smell. Don't hesitate to send an email if there is something suspicious.

Iron bacteria, also called iron flocculent, can be found in slow moving or stagnant areas of a stream. It can appear as a rusty, orange slime and may create and oil like sheen on the water surface. This is a naturally occurring bacteria. You can tell the difference between an iron bacteria oily sheen and real oil by poking the surface of the water with a stick. If the globules move back together again, this is a true oil sheen.

If you have concerns about your stream or see something suspicious please report it on the EPS Report Pollution page. We will investigate any problems that may negatively affect the environment such as trash dumping or wash water discharging to a stream.

Contact Information
Watershed Management and Monitoring
Phone: 410-887-5683

Revised December 13, 2012

Revised April 6, 2016         


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