IS YOUR STREAM POLLUTED BY AMD?
When investigating a stream for AMD problems, you must look at certain “clues”. These clues are very important for deciding how badly the stream is polluted. They are also important in deciding what type of treatment is needed to clean up the stream.
Chemical Clues
pH – A measurement of the acidity of water, or the amount of positively-charged hydrogen ion (H+) activity. The more hydrogen ions present in the water, the more acidic and the lower the pH and vice versa. The pH is measured on a scale from 0-14 with 7 being neutral. The most important thing to remember is that stream water should be from 6.0-9.0. Fish and aquatic bugs will begin to die below or above this range.
Alkalinity –A measurement of the water’s ability to buffer, or reduce the effect of acids (hydrogen ions) without a major change to pH. The most important idea to remember about this clue is the amount of alkalinity should be higher than acidity in a healthy stream. This will not be the case in streams affected by abandoned mine drainage or acid rain.
Acidity - A measurement of the water’s ability to neutralize a base. It is also a condition where the amount of positively-charged hydrogen ions is high (H+), and the pH is less than 7.0. The most important idea to remember about this clue is that the amount of acidity should be less than alkalinity in a healthy stream. If acidity is higher than alkalinity there is a problem in the stream either from AMD or acid rain.
Conductivity – A measurement of the ability of water to carry an electrical current. The presence of dissolved metals such as iron and aluminum increase conductivity. Treated water can also have high amounts of dissolved solids which would increase the conductivity. The most important idea to remember about this clue is that the higher the number, the more dissolved stuff is in the water which can hurt the fish and bugs that live there.
Sulfates – A substance that is present in the water when it comes in contact with pyrite. High readings of sulfates are good evidence that mining has occurred. This is what causes a rotten egg smell around water polluted from AMD. The most important idea to remember about this clue is that a typical measurement of sulfates in a stream is approximately 50 mg/L. A reading of an 80mg/L or more indicates that there may be AMD in the stream. Sulfates must be less than 250 mg/L in drinking water.
Iron – A metal associated with mine drainage. When separating out as a solid, iron leaves a red-orange to yellow color on the streambed. This is sometimes referred to as “yellow boy”. To form a solid, water with dissolved iron needs oxygen and a pH of at least 3.5. The most important idea to remember about this clue is that if dissolved iron has a concentration of more than 1.5 mg/L then fish and bugs will start to die.
Aluminum - A metal that is associated with mine drainage. When separating out as a solid, aluminum leaves a white color on the streambed. To form a solid the pH needs to be above a 5.0. Oxygen is not needed in order for aluminum to become a solid. The most important idea to remember about this clue is that if dissolved aluminum has a concentration of more than 0.75 mg/L in the water then fish and bugs will start to die.
Manganese – A metal that is associated with mine drainage. When separating out as a solid, manganese leaves a black color on the streambed. The best condition for manganese to form as a solid is at a pH above 9.0. Manganese does not affect aquatic life in a stream, but it is a concern in drinking water. State standards state that the concentration must be less than 1.0 mg/L. The most important idea to remember about this clue is that its presence occurs in water polluted by AMD.
Total Suspended Solids (TSS) – Basically, these are compounds that are present as a solid in the water sample. This would make the water appear cloudy. The most important idea to remember about this clue is that less than 25 mg/L is clear water.
Total Dissolved Solids (TDS) – These are the compounds such as the iron, aluminum, and manganese that are dissolved in the water sample. The most important idea to remember about this clue is that more than 400 mg/L in a sample is considered polluted.
Acidity - A measurement of the water’s ability to neutralize a base. It is also a condition where the amount of positively-charged hydrogen ions is high (H+), and the pH is less than 7.0. The most important idea to remember about this clue is that the amount of acidity should be less than alkalinity in a healthy stream. If acidity is higher than alkalinity there is a problem in the stream either from AMD or acid rain.
Conductivity – A measurement of the ability of water to carry an electrical current. The presence of dissolved metals such as iron and aluminum increase conductivity. Treated water can also have high amounts of dissolved solids which would increase the conductivity. The most important idea to remember about this clue is that the higher the number, the more dissolved stuff is in the water which can hurt the fish and bugs that live there.
Sulfates – A substance that is present in the water when it comes in contact with pyrite. High readings of sulfates are good evidence that mining has occurred. This is what causes a rotten egg smell around water polluted from AMD. The most important idea to remember about this clue is that a typical measurement of sulfates in a stream is approximately 50 mg/L. A reading of an 80mg/L or more indicates that there may be AMD in the stream. Sulfates must be less than 250 mg/L in drinking water.
Iron – A metal associated with mine drainage. When separating out as a solid, iron leaves a red-orange to yellow color on the streambed. This is sometimes referred to as “yellow boy”. To form a solid, water with dissolved iron needs oxygen and a pH of at least 3.5. The most important idea to remember about this clue is that if dissolved iron has a concentration of more than 1.5 mg/L then fish and bugs will start to die.
Aluminum - A metal that is associated with mine drainage. When separating out as a solid, aluminum leaves a white color on the streambed. To form a solid the pH needs to be above a 5.0. Oxygen is not needed in order for aluminum to become a solid. The most important idea to remember about this clue is that if dissolved aluminum has a concentration of more than 0.75 mg/L in the water then fish and bugs will start to die.
Manganese – A metal that is associated with mine drainage. When separating out as a solid, manganese leaves a black color on the streambed. The best condition for manganese to form as a solid is at a pH above 9.0. Manganese does not affect aquatic life in a stream, but it is a concern in drinking water. State standards state that the concentration must be less than 1.0 mg/L. The most important idea to remember about this clue is that its presence occurs in water polluted by AMD.
Total Suspended Solids (TSS) – Basically, these are compounds that are present as a solid in the water sample. This would make the water appear cloudy. The most important idea to remember about this clue is that less than 25 mg/L is clear water.
Total Dissolved Solids (TDS) – These are the compounds such as the iron, aluminum, and manganese that are dissolved in the water sample. The most important idea to remember about this clue is that more than 400 mg/L in a sample is considered polluted.
Physical Clues
Siltation - This clue is hard to measure. Silt is the material that settles on the bottom of the stream and causes the water to be muddy in a rainstorm. A clue that a stream is polluted by AMD is the red or white coating on the rocks. Silt from old spoil piles can be washed into the stream. The silt will smother aquatic bugs living on the rocks and can bury places where fish lay their eggs.
Temperature – This can be taken using a simple thermometer and is always taken in the field. This clue is for discharges only. Temperature provides clues on whether a discharge is coming from a deep mine or the surface. Water from a deep mine discharge will have the same temperature in summer and winter. Water that is flowing through a spoil pile will have a temperature that changes with the season.
Flow – This is not a clue for deciding if it is AMD or not but it is important for deciding on the treatment for the discharge. A variety of methods can be used to determine flow (See Flow Measuring Techniques ). It is usually expressed in gallons per minute (gpm). Flow is used to calculate the loadings (amounts) of pollutants in a stream.
Loadings – This is a calculation that is used to understand how many excess metals or acidity a discharge or stream is actually transporting. This formula looks at both flow and concentration.
Loading (lbs/day) = flow rate (gpm) X Concentration (mg/L) X 0.012
For example two discharges can have the following readings:
Discharge 1 → Iron 5 mg/L and flow 25 gpm
Discharge 2 → Iron 5 mg/L and flow 50 gpm
When looking at the discharges it would first appear that the discharges are the same since they both have 5 mg/L of iron. Using the formula above the actual loadings are calculated.
Discharge 1 → Loading of iron 1.5 lbs/day
Discharge 2 → Loading of iron 3.0 lbs/day
This shows that the discharge with the higher flow is producing more iron to pollute the stream.
Temperature, flow, pH and conductivity are the clues that are taken in the field when sampling. Then the rest of the clues are found by sending a water sample to a lab to test for pH, alkalinity, acidity, conductivity, sulfates, iron, aluminum, manganese, suspended solids and total dissolved solids. Typically, the pH measurement taken in the field is more accurate than the reading in the lab.
Temperature – This can be taken using a simple thermometer and is always taken in the field. This clue is for discharges only. Temperature provides clues on whether a discharge is coming from a deep mine or the surface. Water from a deep mine discharge will have the same temperature in summer and winter. Water that is flowing through a spoil pile will have a temperature that changes with the season.
Flow – This is not a clue for deciding if it is AMD or not but it is important for deciding on the treatment for the discharge. A variety of methods can be used to determine flow (See Flow Measuring Techniques ). It is usually expressed in gallons per minute (gpm). Flow is used to calculate the loadings (amounts) of pollutants in a stream.
Loadings – This is a calculation that is used to understand how many excess metals or acidity a discharge or stream is actually transporting. This formula looks at both flow and concentration.
Loading (lbs/day) = flow rate (gpm) X Concentration (mg/L) X 0.012
For example two discharges can have the following readings:
Discharge 1 → Iron 5 mg/L and flow 25 gpm
Discharge 2 → Iron 5 mg/L and flow 50 gpm
When looking at the discharges it would first appear that the discharges are the same since they both have 5 mg/L of iron. Using the formula above the actual loadings are calculated.
Discharge 1 → Loading of iron 1.5 lbs/day
Discharge 2 → Loading of iron 3.0 lbs/day
This shows that the discharge with the higher flow is producing more iron to pollute the stream.
Temperature, flow, pH and conductivity are the clues that are taken in the field when sampling. Then the rest of the clues are found by sending a water sample to a lab to test for pH, alkalinity, acidity, conductivity, sulfates, iron, aluminum, manganese, suspended solids and total dissolved solids. Typically, the pH measurement taken in the field is more accurate than the reading in the lab.
Are you ready to test your skills at reading the clues? Try out these three scenarios!
Scenario #1 Scenario #2 Scenario #3
Scenario #1 Scenario #2 Scenario #3