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Indiana Department of Environmental Management

Nonpoint Source Water Pollution

Nonpoint Source > Watershed Assessment > Water Quality Assessments and Reporting > Section 303(d) List of Impaired Waters > Impairments (and other constituents) Considered in Assessing Indiana Waters Impairments (and other constituents) Considered in Assessing Indiana Waters

Impairments shown on the 303(d) represent an impairment to one of three designated uses identified in Indiana’s Water Quality Standards (WQS).

Aquatic Life Use Impairments include both direct and indirect evidence of impairment to the aquatic ecosystem. Direct measures include impairment of one or more aquatic communities including fish and/or macroinvertebrates. Indirect measures are those indicating impairment resulting from chemical and/or other conditions that have the potential to negatively impact the ability of a waterbody to support a healthy aquatic community.

Recreational use impairments indicate that a waterbody is not fully supporting recreational uses such as swimming, fishing and boating – uses that involve bodily contact with the water.

Fish consumption impairments indicate waters where fish tissue samples indicate high concentrations of certain chemicals that when ingested over long periods of time may cause human health problems.

Recreational Use Impairments

Bacteria/E. coli

E. coli is a bacteria present in the feces of warm-blooded animals. E. coli in surface waters indicates the presences of pathogens that can cause illness in humans. An E. coli listing on Indiana’s 303(d) list means IDEM’s monitoring data shows the concentration of E. coli is higher than allowed in the state’s WQS.

Total Phosphorus

IDEM evaluates total phosphorus data in two different ways. Total phosphorus data collected from rivers and streams are evaluated in combination with other parameters to determine the extent to which nutrients may be impacting aquatic life use (See Nutrients). Total phosphorus data collected from Indiana’s lakes and reservoirs are evaluated in combination with other parameters to determine the degree to which nutrient enrichment may be impacting recreational uses. Nutrient enrichment can cause thick algae and other conditions that can deter people from swimming, wading, or enjoying other water-related activities on lakes and reservoirs. A 303(d) listing for total phosphorus identifies a lake or reservoir where such conditions have been identified based on the data collected there.

Aquatic Life Use Impairments

Impaired Biotic Communities (IBC)

Biological communities – the fish and aquatic invertebrates, such as insects, in stream – are indicators of the cumulative effects of activities that affect water quality conditions over time. An IBC listing on Indiana’s 303(d) list, means IDEM’s monitoring data shows one or both of the aquatic communities are not as healthy as they should be. Although an IBC is a direct measure of aquatic life use impairment, often these sources of these impairments are unknown.

Dissolved Oxygen (DO)

The amount of DO in surface waters is important. Aquatic organisms depend on DO in the water to breathe. A DO listing on Indiana’s 303(d) list means IDEM’s monitoring data shows the concentrations of DO is lower than needed to support the aquatic communities. IDEM evaluates DO data in two ways for the purpose of making water quality assessments. Low DO concentrations are evaluated against the state’s WQS for DO to determine whether the waterbody in question is capable of supporting aquatic life. DO results are also evaluated in combination with other parameters to determine the degree to which nutrient enrichment may be impacting the waterbody (See Nutrients).

pH

The pH level is a measure of the acidity in the water. pH levels that are too low or too high can have harmful effects on aquatic organisms. Most aquatic life needs pH levels in the range of 6-9 to survive. IDEM evaluates pH data in two ways for the purpose of making water quality assessments. A pH listing on Indiana’s 303(d) list means IDEM’s monitoring data shows the concentrations of pH outside this range, which is specified in the state’s WQS. IDEM also evaluates pH results in combination with other parameters to determine the degree to which nutrient enrichment may be impacting the waterbody (See Nutrients).

Nutrients

Nutrients such as phosphorus and nitrogen are a concern for surface waters because excessive amounts can result in large “blooms” of algae. This can cause negative effects on aquatic communities. A nutrient listing on Indiana’s 303(d) list means IDEM’s monitoring data shows evidence of nutrient problems and the concentrations of nutrients in a river or stream are high enough to adversely affect the aquatic ecosystem and affect the aquatic communities. When making nutrient assessments, IDEM evaluates nitrogen and phosphorus data in combination with other data including DO concentrations, pH and excessive algae that may indicate a nutrient problem.

Nitrogen

Nitrogen promotes plant growth. Excessive nitrogen can cause an excess of algae blooms which can affect the amount of oxygen in the water and decrease light penetration. IDEM does not evaluate nitrogen data independently for the purpose of making aquatic life use assessments or developing its 303(d) list. Rather, IDEM evaluates nitrogen data for the purpose of developing TMDLs for waters where impaired biotic communities have been found in order to determine the extent to which nitrogen may be contributing to the impairment.

Phosphorus

Phosphorus promotes plant growth. Excessive phosphorus can cause and excess of algae blooms which affecting the amount of oxygen in water and decrease light penetration. IDEM does not evaluate phosphorus independently for the purpose of making aquatic life use assessments. Rather, IDEM evaluates phosphorus data for the purpose of developing TMDLs for waters where impaired biotic communities have been found in order to determine the extent to which phosphorus may be contributing to the impairment.

Sulfate

Sulfate in surface water is a concern because in excess, it can react with dissolved metals in the water to form other, more toxic chemicals and can change the pH of the water making it more acidic. A sulfate listing on Indiana’s 303(d) list means IDEM’s monitoring data shows concentrations of sulfate higher than allowed in Indiana’s WQS.

Chloride

Chloride is a measure of the salinity of water. High chloride concentrations can interfere with the growth of aquatic vegetation which can in turn affect the aquatic ecosystem. A chloride listing on Indiana’s 303(d) list means IDEM’s monitoring data shows the concentrations of chlorides is higher than the state’s WQS allow.

Ammonia

Ammonia is extremely toxic and even relatively low levels pose a threat to aquatic organisms. An ammonia listing on Indiana’s 303(d) list means IDEM’s monitoring data shows the concentrations of ammonia is higher than allowed by the state’s WQS.

Free Cyanide

Fish and aquatic invertebrates are particularly sensitive to cyanide exposure. High concentrations of cyanide reduce swimming performance, inhibit reproduction and causes death. A cyanide listing on Indiana’s 303(d) list means IDEM’s monitoring data for free cyanide, which is the portion most toxic to aquatic organisms shows the concentrations of cyanide is higher than Indiana’s WQS allow.

Total Mercury (Water)

Total mercury is made up almost entirely of methylmercury, which can have a number of negative impacts on fish when present in high concentrations in surface waters. These impacts can include death, reduced fertility, and slower growth and development. A “Total Mercury (Water)” listing on Indiana’s 303(d) list means IDEM has water quality monitoring data indicating concentrations of total mercury in water exceeding the concentration allowed by the state’s WQS.

Dissolved Metals

Heavy metals, such as zinc, nickel, copper and lead when dissolved in surface waters can have harmful effects on aquatic life. When dissolved, metals can interfere with the bodily functions of fish and aquatic insects. A metals listing on Indiana’s 303(d) list means IDEM’s monitoring data shows the concentrations of dissolved metals exceed the applicable criteria in Indiana’s WQS.

Polychlorinated biphenyls (PCBs) (Water)

The levels of PCBs in surface water are of concern due to the potential they have for contamination of fish. PCB-contaminated fish can pose a risk to human health when consumed over long periods of time or by sensitive populations such as young children or women of child-bearing age. A “PCBs (Water)” listing on Indiana’s 303(d) list means IDEM has water quality monitoring data indicating concentrations of PCBs in water exceeding the concentration allowed by the state’s WQS.

Pesticides

Repeated exposure to certain pesticides can result in negative physical effects on fish and invertebrates. Pesticides can also reduce the availability of plants and insects, which are important food sources for fish and other aquatic life. A pesticide listing on Indiana’s 303(d) list means IDEM’s monitoring data shows the concentrations of pesticides is higher than Indiana’s WQS allow.

Total Suspended Solids (TSS)

High concentrations of suspended solids reduce light passing through the water slowing photosynthesis. Reduced photosynthesis can lower DO concentrations in the water potentially impacting fish communities. Suspended sediment can also clog the gills of fish, inhibit their growth, decrease their resistance to disease, and prevent proper egg and larval development. Although IDEM does not evaluate TSS for the purpose of making aquatic life use assessments, TSS data are evaluated when developing TMDLs for waters where impaired biotic communities have been found.

Oil & Grease

Impairments for “Oil & Grease” on Indiana’s 303(d) list are historical impairments based on data that are no longer collected and water quality assessment methods that are no longer used. IDEM reevaluated these impairments in 2008 and found evidence that the waters currently listed for oil and grease are still impaired. These impairments will remain on the 303(d) list until IDEM has water quality data indicating they no longer exist.

Drinking Water Use Impairments

Algae, Taste & Odor

Algae are a normal component of a healthy aquatic ecosystem. However, excessive algae can become a nuisance and can require public water supply facilities to go above and beyond conventional treatment to ensure high quality drinking water. Excessive algae can lead to taste and odor issues related to treated drinking water.

Impairments for algae, taste and odor on the 303(d) list are historical impairments related specifically to lakes serving as public water supplies. Such impairments are historical only in the sense that the methods used to make the original assessment are no longer in use. These impairments will remain on the 303(d) list until IDEM has more current data to show that they no longer exist.

Fish Consumption Use Impairments

Total Mercury (Fish Tissue)

Total mercury is made up almost entirely of methylmercury, which can become concentrated in fish tissue up through the food chain as smaller fish are successively consumed by bigger fish. IDEM evaluates total mercury concentrations in fish tissue to identify waters in which average concentrations might pose a human health risk if fish from that waterbody are consumed over long periods of time or by sensitive populations such as children or women of child-bearing age. A listing for “Total Mercury (Fish Tissue)” on Indiana’s 303(d) list means IDEM has showing the average concentration of mercury in fish tissue exceeds the level recommended by U.S. EPA for human consumption.

Polychlorinated biphenyls (PCBs) (Fish Tissue)

PCBs, which are now banned in the United States, can accumulate in fish tissue from both the water in which fish live and the food they consume if either or both have been contaminated in the past. IDEM evaluates the concentration of PCBs in fish tissue to identify waters with levels high enough to pose a human health risk if fish from that waterbody were consumed over long periods of time or by sensitive populations such as children or women of child-bearing age. A listing for “PCBs (Fish Tissue)” on Indiana’s 303(d) list means IDEM has showing the average concentration of PCBs in fish tissue exceeds the level determined by IDEM to be safe for human consumption.

Dioxins

Most dioxins in the environment come from human activities as a by-product of burning of household or industrial wastes and other industrial activities. They can also occur naturally during forest fires or volcanic activity. Dioxins do not easily dissolve in water and tend to sink to the bottom of the waterbody where they can be absorbed by aquatic organisms. Dioxin concentrations can increase up the food chain as these organisms are consumed by fish, and those fish are consumed by yet larger fish. Listings for “Dioxin (Water)” on Indiana’s 303(d) list means IDEM has data indicating concentrations of dioxin in water that exceeds the concentration allowed by Indiana’s WQS.