Mecklenburg County, North Carolina
State of the Environment Report, 1997

Contents | Agency Acronyms | Acknowledgements | Introduction | Executive Summary | State of the Air | State of the Water | State of the Land | Issues and Recommendations | Appendix A | Appendix B | Appendix C | Appendix D | Report Cover Page | About MCDEP | MCDEP Home Page

STATE OF THE WATER

(Water Indicators)

Surface and ground water resources are essential in maintaining the quality of life enjoyed in Mecklenburg County. The pollution of these waters results in their loss as an important resource and possible negative human health impacts. This chapter will present information concerning the state of Mecklenburg County's surface and ground water resources as reflected through 1996 and 1997 water quality data as well as identify, where possible, important trends related to surface and ground water quality. A reference table provides a quick summary of important environmental indicators related to Mecklenburg County's water.

Overall Quality

The quality of the water in lakes and creeks is determined by several chemical, physical and biological parameters. Surface water quality standards have been established for many chemical and physical parameters and are listed in the North Carolina Administra-tive Code. For parameters without state standards, action levels are established by MCDEP based on calculations of normal background levels and indicators of pollution problems. An exceedance of a surface water quality action level and/or a surface water quality standard suggest a possible pollution problem and degradation of water quality to a point where its primary use is threatened. Creeks in Mecklenburg County are classified by the State of North Carolina for use as aquatic life habitat and secondary recreation including wading, boating, and other uses where human body contact with water is infrequent, unorganized or incidental. The three lakes on the western border of the County are classified for use as drinking water supplies, aquatic habitats, and primary recreation such as swimming and other activities involving frequent human body contact. Follow-up activities to restore water quality are required when these uses are threatened as indicated by exceedances of state standards or action levels.

Alkalinity and conductivity are two parameters that serve as indicators for certain types of industrial and agricultural pollution. Biological oxygen demand (BOD) measures the amount of oxygen required for the breakdown of organic materials and the oxidation of inorganic materials such as ferrous iron and sulfides. The higher the BOD level, the greater the presence of pollution. Dissolved Oxygen (DO) is a measure of the amount of oxygen available to aquatic organisms such as fish. DO levels below 5.0 parts per million (ppm) are stressful or deadly to most aquatic organisms. Ammonia, nitrogen, nitrate, nitrite, Total Kjeldahl Nitrogen (TKN), orthophosphorus and total phosphorus are measures of nutrient enrichment and serve as indicators of problems such as leaking septic fields and sewer lines, discharges from wastewater treatment plants and polluted storm water runoff. Chlorophyll-a measures the phytoplankton (algae) community in a stream or lake. Higher chlorophyll-a levels correspond to greater algal populations, indicating possible nutrient enrichment. pH is a chemical measure of water quality and is related to the geological character, acidity of the soil, and pollutant discharge. Changes in pH are useful in tracing a pollutant to its source. Secchi disk depth (lakes), suspended solids, total solids and turbidity measure the clarity of the water. Changes in these parameters can indicate nutrient enrichment or erosion and sedimentation problems. Temperature measurements can reveal thermal discharges, while fecal coliform bacteria levels are used to indicate the possible presence of human and/or animal fecal contamination.

Indices are valuable summaries and reference tools often used to report the quality of a surface water body. For physical and chemical water quality parameters, Mecklenburg County has adopted a modification of the Water Quality Index (WQI) developed by NSF International, Inc. for creeks and the Fusilier adaptation of the NSF Water Quality Index for lakes. The WQI is based on monthly sampling measurements of Mecklenburg County creeks and lakes. The parameters measured for the stream index include pH, total phosphorus, nitrate, turbidity, total solids, BOD, fecal coliform, DO (% saturation), and change in temperature from upstream to downstream. Parameters measured for the lake index include: pH, total phosphorus, nitrate, alkalinity, chlorophyll-a, DO (% saturation), temperature, conductivity, and secchi disk depth. Lakes are measured monthly from May through September and every other month for the remainder of the year. The WQI is on a scale from 0-100 with higher values representing better water quality conditions.

Because chemical and physical measurements of water quality as summarized in the WQI are limited in their ability to fully assess water quality, biological parameters are also useful in determining the quality of a particular surface water. The purpose of biological monitoring is to assess the aquatic life present in surface waters, particularly the benthic (bottom-dwelling) community. Changes in the composition of benthic macroinvertebrate species can reflect changes in water quality caused by pollution problems. Benthic macroinvertebrates are ideal water quality indicators because they are sensitive to changes in water quality, found in all types of aquatic habitats, less mobile than other aquatic groups such as fish and large enough to be easily collected. Chemical and physical monitoring may miss intermittent pollutant discharges, while macroinvertebrates are exposed to everything that enters the surface water body, thus providing a broader measure of water quality. Data from this sampling is summarized in the Biotic Index that is measured on a scale of 0-100 similar to the WQI.

The most accurate summary of water quality conditions in Mecklenburg County is available through an overall Water Quality Rating System that incorporates chemical, physical and biological parameters. The rating number is obtained by calculating a yearly WQI average for each monitoring site and averaging this number with the site's Biotic Index. Figure W-1 illustrates the overall water quality in Mecklenburg County in 1997 using a Water Quality Rating (WQR) System. This system is measured on the same scale as the WQI and Biotic Index. Table W-2 illustrates acceptable water uses for the nine Overall Water Quality Rating values.

Figure W-2 illustrates surface water quality trends in Mecklen-burg County as based on WQI measurements. Index values have held steady in the fair to good range since measurements began in 1989. Increased growth in the southern basins of the County, however, has led to increased water quality degradation and their failure to fully support their classified use as previously discussed. A similar situation is developing in the County's outlying basins, including the west and north basins that discharge into Mecklenburg County's primary drinking water supply, Mountain Island Lake.

For purposes of this report, Mecklenburg County's basins have been combined into eight geographic drainage basins as indicated in Figure W-1. These basins are listed below in order from the worst to best based on overall water quality ratings:

South Basin
Southwest Basin
Southeast Basin
Northwest Basin
East Basin
West Basin
Lake Wylie Basin
Lake Norman and Mountain Island Lake Basin

The following pages contain a discussion of each of these basins. This discussion is supplemented by individual basin maps and a basin profile that summarizes and highlights important facts about surface water quality in each basin.

South Basin

Creeks: Briar, Little Sugar, Little Hope, Edwards Branch
Drainage Area: 50.96 Square Miles
Estimated Population: 155,800
Estimated Population Density: 3057 Persons/Square Mile
Predominant Land Use: 58% Residential, 12% Open Space, 7% Commercial, 6% Industrial
Primary Water Usage: Fish and Wildlife Propagation, Secondary Recreation
Water Quality Monitoring Sites: 6
Exceedances Of Standards: 4
Exceedances Of Action Levels: 87
Average Biotic Index: Fair (21)
Average Water Quality Index: Fair/Good (64)
Overall Water Quality Rating: Poor/Fair (43)
Primary Pollutants: Fecal Coliform, Nitrate
Primary Pollution Sources: Sugar Creek Wastewater Treatment Plant, Sewer Line Overflows, Industrial Discharges, and Storm Water Runoff

Surface water quality in the South Basin (Figure W-3) was the poorest of all basins in Mecklenburg County in 1997. The average Biotic and Water Quality Indices and the Overall Water Quality Rating were the lowest measured in Mecklenburg County. Lower Little Sugar Creek was rated as Poor/Fair (39) while Upper Little Sugar and Briar Creeks were also rated Poor/Fair (44), yet had slightly better water quality overall. These measurements of water quality were based on data obtained from six (6) sites monitored for chemical, physical and biological parameters. The South Basin also had the highest number of exceedances of water quality action levels, 109, an indication of significant water quality degradation. The Sugar Creek Wastewater Treatment Plant, located immediately downstream of the confluence of Little Sugar and Briar Creeks, is the major source of nitrate. Nitrate is the primary pollutant within the basin with a total of sixteen (16) action level exceedances. According to the Charlotte Mecklenburg Utility Department (CMUD), approximately 70 overflows of municipal sanitary sewer lines occurred in Little Sugar and Briar Creeks in 1997, the highest in Mecklenburg County. This was the highest number reported among all basins in the county, resulting in the highest average fecal coliform bacteria measurements in the County with a total of thirty-four (34) action level exceedances. Other sources of pollution within the basin include industrial discharges and storm water runoff. Since the South Basin has a high percentage of residential development, discharges of lawn fertilizers during storm events also contribute to elevated nutrient levels.

The South Basin is the most populated area of Mecklenburg County with the highest population density and the least amount of open space. This basin has the highest percentage of multifamily, industrial and commercial development in the County, which contributes to water quality degradation from discharges of fecal coliform bacteria, heavy metals, organics and nutrients. Municipal parks, such as Freedom Park and an adjoining Greenway, are found along the banks of creeks within the basin. The proximity of recreational areas to polluted surface waters may negatively impact human health as these are areas where direct body contact sometimes occurs. Surface waters within the basin support an average diversity of aquatic life which is threatened particularly in the Lower Little Sugar Creek Basin.

Southwest Basin

Creeks: Sugar, Taggart, Coffey, Irwin, Stewart, Steele, Walker Branch, Kings Branch
Drainage Area: 81.84 Square Miles
Estimated Population: 95,500
Estimated Population Density: 1,167 Persons/Square Mile
Predominant Land Use: 41% Residential, 34% Open Space, 12% Light Commercial/Industrial Primary Water Usage: Fish and Wildlife Propagation, Secondary Recreation
Water Quality Monitoring Sites: 10
Exceedances Of Standards: 6
Exceedances of Action Levels: 81
Average Biotic Index: Fair (25)
Average Water Quality Index: Good (71)
Overall Water Quality Rating: Fair (48)
Primary Pollutants: Fecal Coliform Bacteria, Nitrate
Primary Pollution Sources: Irwin Creek Wastewater Treatment Plant, Sewer Line Overflows, Storm Water Runoff

The Southwest Basin (Figure W-4) had the second poorest surface water quality in ranking in the County in 1997, better than the South Basin by only five (5) overall rating points. The average Biotic and Water Quality Indices also suggest the second poorest water quality in the County. The Southwest Basin occupies 37% more land area than the South Basin and has a total of ten (10) sites monitoring various chemical, physical and biological parameters. The number of exceedances of water quality action levels is also second worst. The Irwin Creek Wastewater Treatment Plant located below the confluence with Stewart Creek is the major source of nitrate in Sugar Creek, one of the primary pollutants within the basin with a total of fifteen (15) exceedances of action levels. Fifty-one (51) overflows from municipal sanitary sewer lines were reported by CMUD in 1997, contributing to thirty-nine (39) exceedances of the fecal coliform bacteria action level.

The Southwest Basin is less densely populated than the South Basin with the Steele Creek area of the basin being among the lowest populated areas of the County. Storm water pollution from asphalt surfaces and other impervious areas, particularly in the Sugar Creek area, contributes to elevated levels of fecal coliform bacteria, heavy metals, organics and nutrients. Municipal parks line the banks of some creeks in the Southwest Basin resulting in possible human body contact with polluted surface waters during recreational usage. Surface waters in the basin support an average diversity of aquatic life which is threatened in the Sugar Creek Basin.

Southeast Basin

Creeks: McMullen, McAlpine, Campbell, Irvins, Four Mile, Six Mile, Goose, Stevens, Flat Branch
Drainage Area: 113.42 Square Miles
Estimated Population: 163,300
Estimated Population Density: 1,440 Persons/Square Mile
Predominant Land Use: 57% Residential, 36% Open Space Residential
Primary Water Usage: Fish and Wildlife Propagation, Secondary Recreation
Water Quality Monitoring Sites: 14
Exceedances Of Standards: 5
Exceedances of Action Levels: 58
Average Biotic Index: Fair (26)
Average Water Quality Index: Good (71)
Overall Water Quality Rating: Fair (49)
Primary Pollutants: Fecal Coliform, Phosphorus
Primary Pollution Sources: McAlpine, Forest Ridge and Farmwood 20 & 21 Wastewater Treatment Plants, Sewer Line Overflows

Surface water quality in the Southeast Basin (Figure W-5) was third lowest among all basins in the County in 1997. Measurements of water quality were obtained from thirteen (13) monitoring sites. The Southeast Basin also had the third highest number of total exceedances of water quality action levels, exceeded only by the South and Southwest Basins. The McAlpine Creek Wastewater Treatment Plant located on the southern end of the basin is a major source of nitrate and phosphorus. A total of thirty-one (31) exceedances of action levels for these pollutants were measured. Treated effluent discharges from two (2) wastewater treatment plants along Irvins Creek are also contributing to elevated nitrate and phosphorus levels. These wastewater treatment plants, although regulated, are not required to remove nitrogen or phosphorus prior to discharge to the receiving stream. According to CMUD, 43 overflows from municipal sanitary sewer lines occurred within the Southeast Basin in 1997, contributing to twenty-three (23) exceedances of the fecal coliform action level which is among the highest in the County.

Overall Water Quality Ratings in the Southeast Basin fluctuated from fair/good (in Goose and Stevens Creeks) to poor/fair (along Lower McAlpine Creek). The abundance of undeveloped, open space near the eastern County line is the primary reason for improved water quality in Goose and Stevens Creeks. Storm water pollutants including discharges of sediment from construction sites have contributed to elevated turbidity levels resulting in five (5) violations of surface water quality standards, among the highest in the County. Several parks, including McAlpine Greenway, are in this basin exposing citizens to possible contact with polluted surface waters during recreational usage. Surface waters in the basin support an average diversity of aquatic life including substantial fish populations.

Northwest Basin

Creeks: McDowell, Torrence
Drainage Area: 32.48 Square Miles
Estimated Population: 7,600
Estimated Population Density: 233 Persons/Square Mile
Predominant Land Use: 44% Residential, 44% Open Space
Primary Water Usage: Upstream of Charlotte's (CMUD) Drinking Water Supply in Mountain Island Lake, Fish and Wildlife Propagation, Secondary Recreation
Water Quality Monitoring Sites: 4
Exceedances of Standards: 5
Exceedances of Action Levels: 25
Average Biotic Index: Fair (37)
Average Water Quality Index: Good (72)
Overall Water Quality Rating: Fair/Good (55)
Primary Pollutants: Nitrate, Sediment
Primary Pollution Sources: McDowell Creek Wastewater Treatment Plant, Land Clearing for Development

The Northwest Basin (Figure W-6) rated fourth out of the eight (8) basins in overall surface water quality. This measurement is based on data obtained from four (4) monitoring sites. Water quality in this basin is important partially because one of its creek basins (McDowell) discharges directly into Mountain Island Lake at McDowell Cove, approximately 2.5 miles upstream of the County's primary drinking water intake location. An average of 86 million gallons of water is pumped daily from this water intake. WQI values for McDowell Cove indicate that water quality is among the most polluted in the County. The McDowell Creek Wastewater Treatment Plant combined with discharges of nutrients and sediments from upstream land development activities are the major sources of phosphorus, nitrate and fecal coliform bacteria. These three (3) pollutants are the basin's primary pollutants accounting for twenty (20) exceedances of water quality action levels during 1997. Lawn fertilizing in this basin, which is 44% single-family residential, is also contributing to the elevated nutrient levels.

The Northwest Basin has one of the lowest population densities of the eight (8) basins. The basin also has a 44% open space, a high percentage for Mecklenburg County. As this open space is converted to residential and commercial developments, however, water quality will degrade as it has in the more urbanized southern basins. Surface waters in the basin support an average diversity of aquatic life including substantial fish populations.

East Basin

Creeks: Clear, McKee, Reedy, Back, Mallard, Stoney, Clarke, Doby, Toby, Cane, Ramah, Rocky River
Drainage Area: 116.81 Square Miles
Estimated Population: 47,700
Estimated Population Density: 408 Persons/Square Mile
Predominant Land Use: 53% Open Space, 41% Residential
Primary Water Usage: Fish and Wildlife Propagation, Secondary Recreation
Water Quality Monitoring Sites: 8
Exceedances Of Standards: 4
Exceedances of Action Levels: 28
Average Biotic Index: Fair/Good (41)
Average Water Quality Index: Good (72)
Overall Water Quality Rating: Fair/Good (57)
Primary Pollutant: Nitrate
Primary Pollution Source: Mallard Creek Wastewater Treatment Plant

Surface water quality in the East Basin (Figure W-7) was better than average compared to other basins in the County, rating as third best of the six creek basins, although the Biotic Index is slightly lower than would be expected for a basin with such a high WQI value. These measurements were obtained from a total of eight (8) sites monitored for chemical, physical and biological parameters. Although exceedances of water quality action levels are below normal for Mecklenburg County, they do include four (4) exceedances of surface water quality standards, all of which were for turbidity. The Mallard Creek Wastewater Treatment Plant, located near the county line along Mallard Creek, is the most significant source of pollution in the basin contributing to elevated nitrate and total phosphorus levels in downstream receiving waters. Mallard Creek has the poorest water quality in the basin due primarily to recent significant land development which has elevated turbidity and fecal coliform levels. The large percentage of single-family residential development in the basin results in an increased discharge of lawn fertilizers in storm water runoff contributing to elevated nutrient levels.

The East Basin is the largest of the eight water quality basins with a relatively low population density and 53% open space. This basin is also the location of several recreational facilities such as Reedy Creek Park which are impacted by the quality of surface waters. Surface waters in the basin support an average diversity of aquatic life including substantial fish populations.

West Basin

Creeks: Gar, Long, McIntyre, Paw, Gum Branch, Gutter Branch
Drainage Area: 74.34 Square Miles
Estimated Population: 28,500
Estimated Population Density: 383 Persons/Square Mile
Predominant Land Use: 50% Open Space, 33% Residential
Primary Water Usage: Gar Creek is upstream of Charlotte's (CMUD) drinking water source, Fish and Wildlife Propagation, Secondary Recreation
Water Quality Monitoring Sites: 5
Exceedances Of Standards: 0
Exceedances of Action Levels: 0
Average Biotic Index: Fair/Good (45)
Average Water Quality Index: Good/Excellent (77)
Overall Water Quality Rating: Fair/Good (61)
Primary Pollutant: Occasional High Fecal Coliform Bacteria Levels
Primary Pollution Source: Land Clearing For Development

In 1997, the cleanest creeks in Mecklenburg County were found in the West Basin (Figure W-8). The West Basin had among the highest Biotic and WQI values and overall water quality rating in the County. These measurements are based on data obtained from five (5) sites monitored for chemical, physical and biological parameters. The West Basin also had no exceedances of water quality action levels. The poorest water quality in the basin is located in Paw Creek which would be considered average when compared with the rest of the County. The discharge of sediment from land clearing activities in the area is the primary pollution source along with impervious surface coverage in Paw Creek which results in an occasional high fecal coliform bacteria and turbidity level. The runoff of lawn fertilizers from the increasing single family residential development in the basin may result in an occasional high phosphorus measurement.

The West Basin has a relatively low population density and the highest percentage of open space in the County. The basin is significant in that Gar Creek discharges to Mountain Island Lake immediately upstream of Charlotte's drinking water intake. Gar Creek contains some of the cleanest surface waters in Mecklenburg County. The basin faces future degradation of its surface waters due to ever-increasing land development activities. Surface waters in the basin support a wide diversity of aquatic life including substantial fish populations. Water in Gar and its tributaries is suitable for infrequent human body contact such as wading.

Lake Wylie Basin

Drainage Area: 28.89 Square Miles
Estimated Population: 3,900
Estimated Population Density: 134 Persons/Square Mile
Predominant Land Use: 63% Open Space, 34% Residential
Primary Water Usage: Belmont And Rock Hill Drinking Water Supplies, Fish And Wildlife Propagation, Primary Recreation
Water Quality Monitoring Sites: 6
Exceedances Of Standards: 6
Exceedances Of Action Levels: 10
Average Biotic Index: No Biological Data Available
Average Water Quality Index: Good (71)
Overall Water Quality Rating: N/A
Primary Pollutant: Chlorophyl-a, Total Phosphorus, Turbidity
Primary Pollution Sources: Wastewater Treatment Plants, Algal Blooms, Land Clearing For Development

Lake Wylie had the poorest surface water quality of the three (3) Catawba lakes that comprise the County's western border; however, it had an average WQI value close to the cleanest county creeks (Figure W-9). This measurement is based on data obtained from six (6) sites monitored for chemical and physical parameters. Biological data is not available for Lake Wylie; therefore, neither a Biotic Index nor an overall water quality rating could be generated. A total of ten (10) exceedances of water quality action levels were detected in the Lake Wylie Basin in 1997. Among these were six (6) exceedances of surface water quality standards. Wastewater treatment plants are a source of pollution along the lake contributing to elevated levels of total phosphorus and other nutrients resulting in algal blooms during the warmer months. A total of eleven (11) wastewater treatment plants are located within the Wylie Basin in Mecklenburg County discharging an estimated 1.2 million gallons per day. More than 100 wastewater treatment plants exist on tributaries to Lake Wylie in Gaston and Lincoln counties.

The population density within the Lake Wylie basin is low when compared to the rest of Mecklenburg County and there is a high percentage of open space within the basin. Lake Wylie serves as a major drinking water supply for Gaston County and areas of South Carolina and also serves as an important recreational resource for the region. Surface waters in the basin support a wide variety of aquatic life including large fish populations and are suitable for swimming.

Lake Norman / Mountain Island Lake Basin

Drainage Area: 29.40 Square Miles
Estimated Population: 5,600
Estimated Population Density: 89 Persons/Square Mile
Predominant Land Use: 46% Residential, 38% Open Space
Primary Water Usage: Charlotte (CMUD) And Mt. Holly Drinking Water Supplies, Fish And Wildlife Propagation, Primary Recreation.
Water Quality Monitoring Sites: 11
Exceedances Of Standards: 7
Exceedances Of Action Levels: 16
Average Biotic Index: No Biological Data Available
Average Water Quality Index: Good/Excellent (75)
Overall Water Quality Rating: N/A
Primary Pollutants: Chlorophyl-a, Nitrate, Total Phosphorus, Turbidity
Primary Pollution Sources: Algae Blooms, McDowell Creek Wastewater Treatment Plant, Land Clearing For Development

Surface water quality in the Lake Norman/ Mountain Island Lake Basin (Figure W-10),based on average WQI values, is among the best in the Mecklenburg County. Biological data was not available for the basin; therefore, neither a Biotic Index nor an overall Water Quality Rating could be generated. Minimal pollution problems were detected through chemical and physical testing at the eleven (11) monitoring sites located within the basin. Lake Norman experienced exceedances of water quality action levels on two (2) occasions for chlorophyll-a. Mountain Island Lake, however, experienced significantly more pollution problems mainly due to discharges into McDowell Cove from land development activities and the McDowell Creek Wastewater Treatment Plant. In McDowell Island Lake, a total of sixteen (16) exceedances of water quality action levels were detected during 1997 including three (3) for nitrate, one (1) for chlorophyl-a, four (4) for total phosphorus, two (2) for secchi disk depth, one (1) for turbidity, and three (3) for fecal coliform. There were 5 exceedances of surface water quality standards in Mountain Island Lake measured during 1997, all within McDowell Cove, including one (1) for chlorophyl-a, one (1) for turbidity, and three (3) for fecal coliform.

The Lake Norman and Mountain Island Lake Basin has a low population density with over 38% open space which is a significant contributing factor towards its good water quality. The basin serves as an important source of drinking water for Mecklenburg County supplying an average of eighty (86) million gallons of water per day. Both Lake Norman and Mountain Island Lake also serve as an important recreational resource for the community. Surface waters within the basin support a wide variety of aquatic life including large fish populations and are suitable for swimming.

Fish community structure and health indicate the ecological integrity of a stream watershed. Two fish surveys, one conducted in 1976 by Cloutman and Olmstead (The Fishes of Mecklenburg County, North Carolina, 1979) and the other by the Mecklenburg County Department of Environmental Protection between 1995 and 1997, reveal changes in stream health in Mecklenburg County over the past two decades (Figure W-11).

In the 1995 - 97 survey, a total of 47 species of fish were collected while 42 species were reported in 1976. The most common fish in Mecklenburg County streams was the Redbreast Sunfish (Lepomis auritus), found at 83 of 84 sites sampled. Other common species were the Bluehead Chub (Nocomis leptocephalus), Bluegill (Lepomis macrochirus), Largemouth Bass (Micropterus salmoides), and Tesselated Darter (Etheostoma olmstedi). One noteworthy find was the Carolina Darter (Etheostoma collis), found in Steele Creek in the Catawba River Basin and Clarke Creek in the Yadkin River Basin. This fish is listed as a Special Concern species on the North Carolina Wildlife Resources Commission List of Endangered Species. These are closely monitored species that have a level of threat to their existence that is legally recognized as being significant under provisions of North Carolina's Non-game Endangered Wildlife Law of 1987. This was the first time the Carolina Darter has been collected from Steele Creek in North Carolina.

Multiple projects are underway to improve stream water quality and habitat which should enhance fish community structure in terms of abundance and total number of species. These projects include the Surface Water Improvement and Management Program (see page 23), sanitary sewer line rehabilitation by the Charlotte-Mecklenburg Utility Department, streamside greenway development by Mecklenburg County Parks and Recreation, and bioengineering projects by Charlotte-Mecklenburg Stormwater Services. Fish sampling will continue to be conducted in order to assess the effectiveness of these combined efforts and to monitor trends in water quality and stream habitat.

Groundwater - Overall Quality

Groundwater is a natural resource economically important to the citizens, industry and agriculture of Mecklenburg County. It is calculated that 30% of Mecklenburg County citizens rely on groundwater as their sole source of potable water. The majority of these wells are located in rural areas, yet there is a number of private and community well systems that are located within areas that are served by the municipal water supply. In order to characterize the quality of the groundwater in Mecklenburg County the information focuses on the baseline values for groundwater quality and on the sites within the county that have the potential to impact, or have impacted the groundwater in their vicinity.

Ambient

An ambient groundwater sampling network for Mecklenburg county was established in 1993 and has been used to determine baseline values for groundwater quality. Twenty-nine (29) monitoring sites were chosen with at least one (1) well located in each of the five (5) major rock types and four (4) DRASTIC Index ranges (Figure W-12). DRASTIC is a standardized system for evaluating groundwater pollution potential using hydrogeologic settings. This method was applied to Mecklenburg County in 1989. DRASTIC stands for: D=Depth to water; R=Net recharge; A=Aquifer media; S=Soil Media; T=Topography; I=Impact of vadose zone; C= Hydraulic conductivity.

All of the wells within the ambient groundwater network are potable (drinkable) wells. The wells meet basic construction standards such as having a concrete slab, having a sanitary seal, grouted, and protected by a well house. Where possible, wells having a depth between 100 and 300 feet and no sources of contamination within 50 feet were selected. These criteria were used to ensure samples reflected background readings. In 1996-1997, groundwater analyses were completed for mineral metals, toxic metals, inorganic parameters such as pH, alkalinity, chloride and nitrates, as well as physical parameters such as hardness and dissolved solids. Volatile organic compounds were also sampled to document that the analyses were not altered by the contamination of man-made compounds.

Table W-3 shows the average groundwater values for nine (9) parameters and compares them to the average values for creeks and city drinking water. All averaged groundwater values are within the suggested USEPA drinking water levels except manganese (Figure W-13) and iron. Manganese averages 0.07 ppm. Eleven (11) of the twenty-nine (29) sampling sites in Mecklenburg County showed elevated levels of manganese at least once during six (6) sampling events. Manganese does not appear to have toxicological significance in drinking water. The USEPA recommended limit of 0.05 ppm is based largely on aesthetic and taste considerations. Manganese in concentrations in excess of 0.2 ppm tends to precipitate and form noxious deposits on foods during cooking and black stains on plumbing fixtures and laundry. Concentrations greater than 0.5 ppm may impart a metallic taste to both foods and water. The presence of manganese as low as 0.1 ppm can stimulate the growth of certain bacteria in reservoirs, filters and distribution lines.

There were nine (9) sampling locations with elevated levels of iron at least once during 1996-1997. The average for 1996-1997 was 0.36 ppm (Figure W-14). The USEPA recommended limit is not based on physiological reactions but on aesthetic and taste considerations, namely the stain that occurs at concentrations greater than 0.3 ppm and the metallic taste that can occur as low as 0.1 ppm depending on the iron compound present. If iron concentrations exceed 0.5 ppm, wells and well screens are likely to become encrusted. If iron concentrations exceed 1.0 ppm, coffee becomes unpalatable.

In 1996, the sodium parameters (Figure W-15) had an annual average below the USEPA suggested level of 20 ppm; however, three (3) sites had at least one (1) sampling event with levels above the suggested drinking water level. The average value for sodium in Mecklenburg County for 1996-1997 was 10.46 ppm. All natural waters contain some sodium with concentrations ranging from less than 0.5 ppm in rain to more than 1000 ppm in brines. In areas composed of igneous and metamorphic rocks (such as Mecklenburg County), groundwater will generally contain sodium concentrations in ranges between 1 ppm and 20 ppm. Sodium in drinking water is of greatest concern to people with abnormal sodium metabolism.

The hardness of the water in Mecklenburg county appears to correlate with rock type. Hard and soft water are relative terms. What is considered hard in Mecklenburg County may be considered soft in New Hanover County on the North Carolina coast. A typical scale for hardness is provided in (Table W-4). Hardness is usually associated with the reaction to soap when it is used. Soap does not clean efficiently in hard water. Hard water leaves insoluble residues in bathtubs, sinks, and clothing. In addition, it causes scales to encrust water heaters, boilers and pipes thereby reducing their capacity and heat transfer properties. This in turn becomes both a technical and economical problem. The higher the concentration of calcium and magnesium, the harder the water. Figure W-16 shows the five (5) major rock types in the county and the average hardness concentration in groundwater for each rock type. These rock types occur throughout the County but are prominent in specific areas (Figure W-17). The highest hardness concentrations in groundwater are in the northeast and southwest where gabbro and diorite rocks are dominant. The lowest hardness concentrations are located in the southeast where greenstone and slate rocks are dominant. Moderate hardness concentrations in groundwater are in the central portion of the county where granite is dominant.

With thirteen (13) sampling events we are beginning to see trends but it is not possible at this time to make conclusions regarding the controlling factors in groundwater quality. With this in mind, some trends that were noted may change as more sampling occurs. For some parameters, the quality of the groundwater appears to be directly related to the geology. Continued sampling will help identify the overall impact of pollution sources on ambient groundwater quality in Mecklenburg County.

Mecklenburg Priority List

In 1997, there were more than seven hundred (700) sites of known and potential sources of groundwater contamination in Mecklenburg County (Appendix B). The Mecklenburg Priority List (MPL) is a compilation of the federal National Priority List (NPL or "Superfund"), the State Priority List, the State Priority Pending List, the NCDENR Incident List and the Non-Discharge permits for Mecklenburg County. All of the sites identified on the MPL have a potential to impact, or already have impacted, the groundwater in their vicinity, thus endangering drinking water supplies. As of December 1997, more than 35% (255) of sites had been evaluated. One hundred nine (109) are in an area where groundwater is not accessed as a potable source. These sites are labeled inactive (Appendix B-b) and will be noted on a separate list as a groundwater contamination site but will not be reviewed yearly under the MPL program. One hundred and forty-six (146) sites were identified in an area where groundwater is accessed as a potable source (Appendix B-a). In 1997 there were two contaminated wells identified. To date the program has identified 177 impacted wells at 40 sites. (Figure W-18) When a responsible party is identified as causing contamination above the drinking water standard, the NCDENR requires the responsible party to provide drinking water to the resident.  When the responsible party is not identified and the contaminant is above the drinking water standard, MCDEP coordinates with other local, state and federal agencies to provide safe drinking water. If city water is available many homeowners abandon the impacted well and connect to city water.

Figure W-19 shows the distribution of MPL sites per zip code. The western portion of the county has a higher number of MPL sites than any other region of the county. The southern portion of the county has the least number of MPL sites. The highest concentration of sites is located in uptown Charlotte (zip code 28202). Groundwater is not used as a drinking water source in uptown Charlotte, but contaminated soils and groundwater can impact surface water. Directly west of uptown Charlotte, zip code area 28208 has 91 MPL sites. This area has the highest number of MPL sites per a given zip code and is of great concern because many areas within this zip code still use groundwater as a drinking water source.