2019-2020 Lake Monitoring Report Charlotte-Mecklenburg Storm Water Services Program SWIM Phase 1 Part 2-CO

Prepared by: Dave Ferguson

Final Report for FY2019-2020

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PURPOSE AND BACKGROUND

The Water Quality Program (WQP) of Charlotte-Mecklenburg Storm Water Services (CMSWS) has an ongoing program to monitor the water quality in the three Lakes bordering the county: , and . Samples are also routinely collected at the two water bodies in the northern end of Mecklenburg County separated from Lake Norman proper by interstate I-77: Lake Cornelius and Lake Davidson. Data collected from all lake sites are used to screen for environmental problems using CMSWS Action and Watch levels for various pollutants and to rate the overall water quality at sampling locations in the lakes using a water quality index. Additional objectives are to describe seasonal trends and address spatial variability in the data. This report presents the lake monitoring data for the sampling period of July 2019 through May 2020. ACTIVITIES AND METHODS Routine lake sampling was conducted every other month beginning in July (July, September, November, January, and May). Lake sampling did not occur in March 2020 due to the coronavirus pandemic temporarily interrupting CMSWS monitoring operations. Five locations were sampled in Lake Norman, one location each on Lake Cornelius and Lake Davidson, ten locations in Mountain Island Lake, and eleven sampling locations in Lake Wylie (Appendices A, B, and C.) These routine locations were also sampled in August 2019 and June 2020 for fecal coliform and E. coli bacteria. Additional monitoring sites (referred to as summer bacteria sites) were sampled for fecal coliform and E. coli bacteria during the summer months (May through September) for all lakes. All sampling efforts were conducted in accordance with approved SOPs. During all routine lake runs, field measurements were collected using a calibrated YSI EXO 2 multiprobe at a depth of 0.2 meters at each site. Field measurements included: temperature, dissolved oxygen, pH, conductivity, and turbidity. Water transparency was measured in the field utilizing a visual Secchi disk with depth reported in meters. Water samples were collected using a Labline composite sampler to a depth of twice the Secchi depth and were placed on ice and transported to the Charlotte Water Laboratory where they were analyzed by standard methods. Water chemistry samples collected at all regular monitoring sites were analyzed for the following parameters: nutrients (total phosphorus, TKN, NH3, and NO2- NO3), chlorophyll a, turbidity, fecal coliform bacteria, and E. coli bacteria. Metals samples were collected at all routine sites during the January and July sampling runs. Lake bottom samples were collected during the July sampling run and were analyzed for metals. At monitoring site AL1 located in upper Lake Wylie at Allen Steam Station ash basin discharge , metals were sampled during every routine lake run including June and August fecal runs. Twelve metals parameters were analyzed: mineral metals (copper, iron, manganese, and zinc) and toxic metals (arsenic, barium, cadmium, chromium, lead, nickel, mercury and selenium). CMSWS staff also conducted monthly grab sampling from three sampling sites on Lake Norman (LN-UP, MA1, and MA2) and four sampling sites on Mountain Island Lake (MI9, MI3D, RB1,

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and RB-UP). These sites are located near Marshall and Riverbend Steam Stations, and this monitoring effort was conducted in a partnership with Charlotte Water. “Coal ash” sites were sampled for the following parameters: metals, mercury, sulfate, bromide, and total dissolved solids. Coal ash sampling results were reported quarterly and annually to Charlotte Water, or with more frequency when high alert sample results were received. All lab data were extracted from Charlotte Water Laboratory Services LABWORKS database and reviewed by the designated Environmental Analyst for QA/QC purposes before being entered in the Water Quality Data Repository. The Trophic State Index (NCTSI) which includes total phosphorus, Secchi depth, and organic nitrogen was calculated by using a formula developed as part of North Carolina’s original Clean Lakes Classification Survey (NCDEM 1982). The NCTSI score for each lake was calculated by averaging the scores from all sites for each lake during the growing season (May through September). The Lake Use Support Index (LUSI) was calculated for all regular sampling sites using EXCEL. Maps were generated using WORD, published to the CMSWS website and presented to their respective lake marine commissions. Since May is the last routine sampling event of the fiscal year and includes the data for the entire fiscal year starting in July, May LUSI maps are presented in this report. RESULTS AND DISCUSSION North Carolina Trophic State Index The North Carolina Trophic State Index (NCTSI) is calculated by using chemical and physical parameters to determine the productivity of a lake. The NCTSI formula for this calculation is shown below in Table 1.

Table 1. NCTSI Formula

North Carolina Trophic State Index (NCTSI) Formula

NCTSI = TONScore + TPScore + SDScore + CHLScore

TON - Total Organic Nitrogen (mg/l) TP - Total Phosphorus (mg/l) SD - Secchi Depth (inches) CHL - Chlorophyll a (ug/l)

The North Carolina Trophic State Index (NCTSI) was calculated for each lake by averaging all sites during the growing season (May through September) and comparing this with the results from past years to assess the degree of eutrophication for each reservoir. Eutrophication is the process of increased nutrient input and concentration in a body of water, either due to natural

3 causes or human influences. (New Hampshire Department of Environmental Services, 2010). Each lake is given a designation based on their NCTSI score of one of the following possible descriptors: oligotrophic, mesotrophic, eutrophic, or hypereutrophic. The classification index scale is shown below in Table 2.

Table 2. NCTSI Index Scale

NCTSI Index Scale

Score Trophic State < -2.0 Oligotrophic -2.0 - 0.0 Mesotrophic 0.0 - 5.0 Eutrophic >5.0 Hypereutrophic

The amount of rainfall that occurs during an assessment period can affect the chemical and physical parameters used in the NCTSI calculations. Table 3 shows the total rainfall amounts for each lake during the summer assessment period for 2017 - 2019. To note, the 2019 rainfall amounts were much lower than the rainfall amounts recorded during 2017 and 2018. Even with the reduction in rainfall amounts, lake classifications remained the same from 2018 to 2019 with very little change in average lake-wide NCTSI scores for summer monitoring events (Table 4). .

Table 3. Rainfall amounts by lake during summer months 2017 vs 2019 (CMSWS FINS network rain gauges)

May 2017 – Sept 2017 May 2018 – Sept 2018 May 2019 – Sept 2019 Lake total rainfall total rainfall total rainfall Norman 23.76 in 22.63 in 14.3 in Mountain Island 25.15 in 19.68 in 15.4 in Wylie 22.89 in 22.32 in 17.59 in Davidson / Cornelius 23 in 22.4 in 13.7 in

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Table 4. Mean summer NCTSI values by lake from 2016 - 2019

2016 2017 2018 2019 NCTSI Trophic Lake NCTSI Trophic NCTSI Trophic NCTSI Trophic Score Classification Score Classification Score Classification Score Classification

Norman -3.9404 Oligotrophic -4.2792 Oligotrophic -3.96238 Oligotrophic -3.9767 Oligotrophic

Mt. Island -2.5586 Oligotrophic -2.977 Oligotrophic -2.40889 Oligotrophic -3.281 Oligotrophic

Wylie -1.0988 Mesotrophic -1.357 Mesotrophic -0.53158 Mesotrophic -1.8716 Mesotrophic

Cornelius -0.5477 Mesotrophic -1.1112 Mesotrophic -1.1263 Mesotrophic -1.7687 Mesotrophic

Davidson -1.8944 Mesotrophic -2.7777 Oligotrophic -2.6772 Oligotrophic -3.7553 Oligotrophic

Lake Use Support Index (LUSI) Background and Overview Charlotte-Mecklenburg Storm Water Services (CMSWS) uses an index to rate lake water quality called LUSI or the Lake Use Support Index. Developed in 2009 by the Water Quality Program, LUSI is based on whether the water quality in the monitored lake is meeting North Carolina water quality standards and is set on a 100 point scale. If these standards are met, surface water quality is supportive of its designated use, hence the name Lake Use Support Index. LUSI is based on five categories of parameters called sub-indices that County staff has determined to be most important for assessing the quality and usability of Mecklenburg County’s lakes. The five (5) sub-indices for LUSI are: • Human Health - fecal coliform bacteria • Sediment – turbidity • Field Data - temperature, dissolved oxygen and pH • Eutrophication - North Carolina Trophic State Index • Metals - 12 mineral and toxic metals

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Table 5 LUSI Rating Scale

LUSI Rating Score

> 95 Supporting +

90 - 95 Supporting

70 – 90 Partially Supporting

50 – 70 Impaired

< 50 Degraded

Calculation of LUSI Scores LUSI scores are based on data collected from six sampling events during the prior 12 months (every other month starting in July) except for metals which are only sampled twice a year. If the water quality standard is met for a subindex, then that sampling event is assigned the maximum score of 16.67 (100 ÷ 6 = 16.67). All LUSI subindex scores are calculated by totaling the scores from the six sampling events and applying the rating scale described in the table above. If the water quality standard is met for all six sampling events the maximum LUSI subindex score of 100 is achieved. Where appropriate, several subindicies, including fecal coliform bacteria, also have intermediate scores corresponding to Watch levels. The Eutrophication (algal growth) subindex is based on the North Carolina Trophic State Index (NCTSI). The NCTSI measures the productivity of the lake using nutrients (total organic nitrogen and total phosphorus), chlorophyll a and water transparency (Secchi depth) to rate lakes as oligotrophic, mesotrophic or eutrophic ranging from very low to very high nutrient content, respectively. For each sampling period, the NCTSI rating is assigned a score from 16.67 for oligotrophic to 0 for hypereutrophic. For all subindicies, if the standard or intermediate scores are not met, a score of 0 is assigned. The five subindex scores are weighted equally and combined to arrive at the overall LUSI score. Data Reporting Lake specific LUSI maps are created for routine lake monitoring sites after each routine sampling month. On the maps, each sampling site contains a color-coded box. The LUSI score is presented at the top of the color-coded box. The fecal coliform subindex indicates if the sampling site is “Swimmable” and is illustrated in the middle of the color-coded box with a swimming figure. The “ecological health” of a site uses the NCTSI score and is represented by an algae figure in the bottom of the color-coded box.

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Historical Values Lakewide averages of LUSI scores for the past 11 years show differences between the major lakes (Figure 1). The monthly average for Lake Norman sites rates the highest with scores near 100 followed by the monthly average for Mountain Island Lake and Lake Wylie. Lake Wylie is the most susceptible reservoir to sediment pollution due to inputs from multiple major tributaries, a shallow main channel, and an overall riverine shape. The figure below depicts all LUSI scores by month historically from July 2009 through May 2020 for Lake Norman, Mountain Island Lake, and Lake Wylie.

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Figure 1 Historical LUSI scores - July 2009 -- May 2020

Lake Use Support Index (LUSI) July 2009 - May 2020 102

100

98

96

94

92 Supporting (Good/Excellent) 90

LUSI Scores LUSI 88 Partially Supporting (Fair)

86

84

82

80 JULY JULY JULY JULY JULY JULY JULY JULY NOV JULY NOV JULY NOV JULY NOV NOV NOV NOV NOV NOV NOV NOV MAR MAR MAR MAR MAR MAR MAR MAR MAR MAR MAR 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Norman Mtn Island Wylie

*No routine lake monitoring efforts were conducted in March 2020 due to the coronavirus temporarily interrupting CMSWS operations

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LUSI Maps The following section presents Lake Use Support Index (LUSI) results from May 2020. Since LUSI is scored using an annual trailing average, the May maps should represent the six sampling results from the fiscal year 2019-2020, however March 2020 was omitted due to the coronavirus pandemic temporarily interrupting monitoring efforts; therefore, only five sampling events were evaluated instead (July 2019, September 2019, November 2019, January 2020, and May 2020.) Lake specific fish consumption advisories are shown on each map.

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Figure 2: Lake Norman (with Lake Cornelius and Lake Davidson)

LUSI scores and fecal coliform levels for July 2019-May of 2020 at all Lower Lake Norman monitoring sites as well as Lake Cornelius and Lake Davidson were in the Supporting+ range. NC Trophic State Index scores from 2019-2020 for Lower Lake Norman and Lake Davidson sites were all Supporting+, while Lake Cornelius rated as Supporting for the year. 10

Figure 3: Mountain Island Lake

LUSI scores for all sites on Mountain Island Lake except for MI3 were in the Supporting+ range. Site MI3 recorded a LUSI score of Supporting. For NC Trophic State Index, sites MI3 and MI6A scored Partially Supporting. These results display common themes in Mountain Island Lake showing that most sediment and nutrient issues are due to the McDowell Creek and/or Gar Creek watersheds.

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Figure 4: Lake Wylie

LUSI scores for Lake Wylie sites varied in comparison from sampling years 2018-2019 to 2019-2020. Sites LW11, LW12, LW4, LW225, and LW3C declined in LUSI scores, while sites BC2, LW1, and LW10C improved. Site LW6A remained at a LUSI score of 100 for yet another monitoring year. The decline in LUSI scores for these sites is attributed to increases in rainfall in the Dutchman’s and watersheds for the sampling period when compared to the previous year’s sampling period. 12

Table 6 – Exceedances of Selected NC Water Quality Standards and CMSWS Action Levels – 2019 - 2020

CMSWS ACTION LEVELS pH Total Fecal col. Chl a Temp. D.O. < <6.0 TOTAL # Metals P NOX >200 >40 Turbid. >32 5.0 or NC Stand. Exceed . >0.04 >0.65 col/100 Lake Norman ug/l >25 ntu Deg. C ppm >9.0 Exceed. ppm ppm ml LN1 Near Cowan's Ford Dam 0 0 1 0 0 1 0 0 0 0 LN2 Ramsey Creek Arm 0 0 2 0 0 2 0 0 0 0 LN4 Main Channel 0 0 0 0 0 0 0 0 0 0 LN5 CMU Water Intake 0 0 2 0 0 2 0 0 0 0 LN9 Davidson Creek/Reeds Creek 0 0 0 0 0 0 0 0 0 0

Lake Cornelius and Davidson LC2 Center of Lake Cornelius 0 0 0 0 0 0 0 0 0 0 LD5 Off Lakeview St. 0 0 0 0 0 0 0 0 0 0

Mountain Island Lake MI1 Near Dam 0 0 0 0 0 0 0 0 0 0 MI2 Gar Creek Cove 0 0 0 0 0 0 0 0 0 0 MI3 McDowell Creek Cove 1 0 0 0 0 0 0 0 0 0 MI3B McDowell Creek Cove 0 0 0 0 0 0 0 0 0 0 MI3D Uplake of McDowell Creek 0 0 0 0 0 0 0 0 0 0 MI4 Headwaters, Hwy 73 0 0 0 0 0 0 0 0 0 0 MI5 Shuffletown Boat Landing 0 0 0 0 0 0 0 0 0 1 MI6A Upper Gar Creek Cove 0 0 0 0 0 0 0 0 0 0 MI8 Downlake McDowell Creek 0 0 0 0 0 0 0 0 0 0 MI9 Charlotte Water Intake 0 0 0 0 0 0 0 0 0 0

Lake Wylie LW1 Near Dam 0 0 0 0 0 0 0 0 0 0 LW10C Wither's Cove 0 0 0 0 0 0 0 0 0 0 LW11 Uplake Paw Creek Cove 0 1 0 0 0 1 0 1 0 1 LW12 Uplake Browns Cove 0 0 0 0 0 0 0 0 0 0 LW225 0 0 0 0 0 0 0 0 0 1 LW3C South Fork Catawba 0 2 1 0 0 3 1 2 1 3 LW4 Paw Creek Cove 0 0 0 0 0 0 0 1 0 1 LW6A Headwaters above Hwy 27 0 0 0 0 0 0 0 0 0 0 BC2 Brown's Cove, middle 0 0 0 0 0 0 0 0 0 1

0 Total Lake Norman 0 0 5 0 0 5 0 0 0 Total Lake Cornelius and 0 Davidson 0 0 0 0 0 0 0 0 0 0 Total Mountain Island Lake 1 0 0 0 0 0 0 0 1 1 Total Lake Wylie 0 3 1 0 0 4 4 1 7

Total # of Exceedances 1 3 6 0 0 9 1 4 1 8

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No exceedances of the state standard for pH or dissolved oxygen were observed during the 2019 – 2020 sampling period at any of the routine lake monitoring sites. There was only one (1) occurrence for the sampling period of an exceedance of chlorophyll A concentration (40 ug/l) at site MI3, McDowell Creek Cove. The exceedance occurred on July 29, 2019. This is not uncommon considering the amount of rainfall in the area at that time as well as elevated water temperatures combined with a very shallow, very nutrient-rich body of water such as McDowell Creek cove. No actions were taken as a result of this exceedance. There were three (3) occurrences for the sampling period of an exceedance of turbidity (25 ntu). Two of these occurrences were at site LW3C in the South Fork Catawba River, which is not uncommon. The South Fork is, by far, the most turbid area of Lake Wylie that CMSWS routinely monitors , and during any rainfall event, it is often extremely turbid. The third occurrence was at LW11, a main-channel monitoring site just upstream of the confluence of Paw Creek and the Catawba River channel. Each of these occurrences were due to rainfall in the area in the immediate days before monitoring occurred. No actions were taken due to these exceedances. There were four (4) occurrences where total phosphorus levels were higher than the state standard at the time of sampling, all on Lake Wylie. Two (2) occurred at site LW3C, one (1) at site LW11, and one (1) at site LW4. These occurrences were also caused by rain events near time of sampling, causing heavier turbidity in the water column, and such, higher nutrient content in the sampled area as well. No actions were taken due to these exceedances. There was only one (1) exceedance of metals during the sampling period. At site LW3C, the iron analytical result returned a value of 1700 ug/l. This observation, as previously discussed in this report, was caused by the amount of sediment suspended in the water column from rainfall at the time of sampling. No actions were taken due to this exceedance. There was only one (1) exceedance where nitrate/nitrite levels were higher than the state standard at the time of sampling, site LW3C on Lake Wylie. Again, this observation was directly caused by the amount of sediment suspended in the water column at time of sampling. No actions were taken due to this exceedance. Exceedances of Fecal Coliform Action Levels Eight (8) occurrences of the CMSWS Action Level for fecal coliform bacteria were observed during the sampling period: seven (7) from Lake Wylie and one (1) from Mountain Island Lake. All occurrences were observed after localized heavy rainfall events. The table below depicts fecal coliform sample results alongside the actual turbidity values for each site when an exceedance occurred. The link between turbidity and bacteria appears to be directly proportional, especially in Mountain Island Lake and Lake Wylie, where the observance of slightly turbid water is much more frequent than Lake Norman, Lake Cornelius, and Lake Davidson. Also, results indicate that in the warmer months, increased water temperature can increase the number of bacteria present in cove areas regardless of higher turbidity values.

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Table 7 Fecal coliform exceedances for the sampling period 2019-2020 with lab NTU results

Sampling Site Lake Fecal Lab Date Col. NTU BC2 Wylie 7/24/19 220 6.5 LW3C Wylie 7/24/19 260 5.4 MI5 Mt Island 8/15/19 220 3.75* LW3C Wylie 9/25/19 440 9.4 LW225 Wylie 1/29/20 210 16 LW3C Wylie 1/29/20 490 36 LW4 Wylie 5/28/20 600 18 LW11 Wylie 5/28/20 600 100 * NTU results taken from YSI Exo Multiparameter sonde, no lab data Metals Sampling near the Allen Steam Station Discharge Metals samples were collected at the ash basin discharge of Allen Steam Station on Lake Wylie during routine and summer fecal sampling runs (Table 4). No exceedances of the state standard occurred during this assessment period.

Table 8 Allen Steam Station Discharge Sampling – Site Al1 (results in ug/l)

NC Analyte 7/24/19 8/20/19 9/25/19 11/18/19 1/29/20 5/26/20 Stand. Arsenic 10 <5 <5 <5 <5 <5 <5 Barium 1000 <100 <100 <100 <100 <100 <100 Cadmium 2 <1 <1 <1 <1 <1 <1 Chromium 50 <5 <5 <5 <5 <5 <5 Copper 7 <2 <2 <2 <2 2.7 <2 Iron 1000 120 220 390 210 210 436 Lead 25 <3 <3 <3 <5 <3 <3 Manganese 200 26 42 97 26 20 29 Mercury 0.012 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 Nickel 25 <2 4.9 <2 <2 <2 <2 Selenium 5 <2 <2 <2 <2 <2 <2 Zinc 50 <10 <10 <10 <10 <10 <10

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SUMMARY AND CONCLUSIONS 1. All five lakes remained in the same NCTSI trophic classification from monitoring year 2018-2019 to 2019-2020. Historically, there has been very little change from year-to- year in the NCTSI when the majority of monitoring events are conducted more than 48 hours after precipitation (lower turbidity levels). This holds true when comparing 2018- 2019 to 2019-2020 data.

2. During the 2019-2020 sampling effort, the Catawba River chain of lakes did not experience a major drought in summer or fall, however in mid-February of 2020 and late May of 2020, major rain events caused Mountain Island Lake’s levels to approach and exceed their full capacity. Norman and Wylie also rose to high levels but never breached the “full” capacity level. Figure 5 below graphically displays the lake levels for the FY19-20 sampling time period.

3. No state standards were exceeded during the 2019-2020 monitoring effort for the Allen Steam Station coal ash basin discharge site (AL1) on Lake Wylie.

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Figure 5 Duke Lake Levels for Lake Norman, Mountain Island Lake, Lake Wylie FY19-20

Lake Levels July 2019 - June 2020 102 2/13/2020, 101.7 5/29/2020, 101.2

101

100

99

98

97

96

95

94 7/1/2019 8/1/2019 9/1/2019 10/1/2019 11/1/2019 12/1/2019 1/1/2020 2/1/2020 3/1/2020 4/1/2020 5/1/2020 6/1/2020

Norman Mtn Island Wylie Full Pond

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CHANGES TO SAMPLING LOCATIONS No site changes occurred to the routine monitoring site regiment during the 2019-2020 sampling effort.

REFERENCES New Hampshire Department of Environmental Resources. 2010. Environmental Fact Sheet. NHDES, Concord, New Hampshire. NCDEM(North Carolina Divison of Environmental Management). 1982. North Carolina Clean Lakes Classification Survey 1982. NCDEM Report No. 83-03. North Carolina Division of Environmental Management. Raleigh, NC.

CMSWS (Charlotte Mecklenburg Storm Water Services). 2015. Lake Monitoring Data Summary for 2014. CMSWS, Charlotte, NC. Lake Program Review and LUSI Document. CMSWS, Charlotte, NC.

CMSWS (Charlotte Mecklenburg Storm Water Services). 2016. Lake Monitoring Data Summary for 2015. CMSWS, Charlotte, NC. Lake Program Review and LUSI Document. CMSWS, Charlotte, NC.

Dave Ferguson-Senior Environmental Specialist July 29, 2020

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Appendix A - Lakes Norman / Davidson / Cornelius Monitoring Locations

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Appendix B – Mountain Island Lake Monitoring Locations

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Appendix C - Lake Wylie Monitoring Locations

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