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Sunshine Lake/Sunrise Waterway Water Quality Management Plan Final Report Submitted to: Prepared by:

January 2015

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Sunshine Lake/Sunrise Waterway WQMP

Atkins Final Report January 2015 i

Table of contents

Chapter Pages 1. Background .......................................................................................................................................... 1 2. Data collection and analysis ............................................................................................................... 3

2.1. Surface water .................................................................................................................................. 4 2.2. Stormwater runoff ........................................................................................................................... 4 2.3. Groundwater seepage .................................................................................................................... 6 2.4. Surficial aquifer ............................................................................................................................... 7

3. Nutrient dataset comparison .............................................................................................................. 8 3.1. Surface water .................................................................................................................................. 8 3.2. Stormwater runoff ........................................................................................................................... 8 3.3. Groundwater seepage .................................................................................................................... 9 3.4. Surficial aquifer ............................................................................................................................. 10

4. Fecal coliform bacteria dataset comparison .................................................................................. 12 4.1. Surface water ................................................................................................................................ 12 4.2. Stormwater runoff ......................................................................................................................... 12

5. Data results and interpretation ......................................................................................................... 14 5.1. Surficial aquifer and lake water elevation ..................................................................................... 14 5.2. Water budget ................................................................................................................................ 18 5.3. Nutrient budget ............................................................................................................................. 20 5.4. Fecal coliform bacteria.................................................................................................................. 32

6. Restoration projects to protect and restore water quality ............................................................ 36 6.1. Monitoring program....................................................................................................................... 36 6.2. Floating Treatment Wetlands (FTWs) .......................................................................................... 37 6.3. Artificial circulation ........................................................................................................................ 39 6.4. Lake level augmentation ............................................................................................................... 41 6.5. Salinity modification ...................................................................................................................... 41 6.6. Stormwater alum injection ............................................................................................................ 43 6.7. Evaluation of the sanitary sewer ................................................................................................... 44 6.8. Programs to address stormwater as a source of bacteria ............................................................ 46 6.9. Available funding sources ............................................................................................................. 47

7. Conclusions and Recommendations ............................................................................................... 48 8. Literature Cited .................................................................................................................................. 50

Tables Table 1. Monthly sampling event dates. ................................................................................................ 4 Table 2. Stormwater sampling events at the three sampling sites. Shaded cells indicate sample was

collected. .................................................................................................................................. 5 Table 3. Groundwater Seepage completed sampling trips .................................................................... 6 Table 4. Surface water criteria as defined by FDEP for Sunshine Lake/Sunrise Waterway. ................ 8 Table 5. Comparable stormwater runoff TN and TP concentrations by land-use category................... 9 Table 6. Comparable groundwater seepage TN and TP concentrations by land-use category. ......... 10 Table 7. Comparable surficial aquifer TN and TP concentrations by land-use category. ................... 11 Table 8. Comparable surface water fecal coliform bacteria concentrations by land-use category. .... 12 Table 9. Comparable stormwater runoff fecal coliform bacteria concentrations by land-use category. .. ............................................................................................................................................... 13 Table 10. Changes in Groundwater Elevation vs. Total Weekly Rainfall .............................................. 16 Table 11. Changes in Lake Water Elevation vs. Total Rainfall ............................................................. 16 Table 12. Changes in Lake Water Elevation vs. Groundwater Elevation Total Rainfall ....................... 18


Atkins Final Report January 2015 ii

Table 13. Groundwater seepage summary statistics (L/m2d

-1 ) ............................................................ 19

Table 14. Input components of the Sunshine Lake/Sunrise Waterway water. ...................................... 20 Table 15. Laboratory analyzed surface water quality summary statistics. ............................................ 21 Table 16. Field measured surface water summary statistics. ............................................................... 22 Table 17. Stormwater runoff water quality summary statistics. ............................................................. 24 Table 18. Groundwater seepage water quality summary statistics. ...................................................... 27 Table 19. Surficial aquifer water quality summary statistics. ................................................................. 29 Table 20. Input components of the Sunshine Lake/Sunrise Waterway nutrient supply over the period

of May 2014 to October 2014. ............................................................................................... 31 Table 21. Fecal coliform bacteria summary statistics for surface water (data have been log10

transformed). ......................................................................................................................... 33 Table 22. Fecal coliform bacteria summary statistics for stormwater runoff water (data have been log10

transformed). ......................................................................................................................... 34 Table 23. Gravity sewer lines in close proximity to Sunshine Lake/Sunrise Waterway system which

have recently been lined. ...................................................................................................... 45 Table 24. Sanitary sewer line segments that were not reviewed by Atkins. ......................................... 45 Table 25. Sewer gravity lines with the most significant issues to be considered for future lining. ........ 46

Figures Figure 1. Sunshine Lake/Sunrise Waterway and its approximate watershed ........................................ 1 Figure 2. Monitoring effort sampling locations. ....................................................................................... 4 Figure 3. Total daily rainfall and stormwater runoff sampling events at the three sampling sites. ......... 5 Figure 4. Groundwater and Lake Water Levels vs. Total Daily Rainfall during the Monitoring Period 15 Figure 5. Change in Groundwater Level vs. Total Weekly Rainfall in the Monitoring Wells ................ 15 Figure 6. Change in Lake Water Level vs. Total Rainfall ..................................................................... 16 Figure 7. Change in Lake Water Elevation vs. Change in Groundwater Elevation in MW-1 ............... 17 Figure 8. Change in Lake Water Elevation vs. Change in Groundwater Elevation in MW-2 ............... 18 Figure 9. Change in Lake Water Elevation vs. Change in Groundwater Elevation in MW-2. .............. 18 Figure 10. Schematic boxplot ................................................................................................................. 20 Figure 11. Surface water TN concentrations within Sunshine Lake/ Sunrise Waterway. ...................... 23 Figure 12. Surface water total phosphorus concentrations within Sunshine Lake/ Sunrise Waterway. 23 Figure 13. Stormwater runoff TN concentrations within Sunshine Lake/ Sunrise Waterway. ................ 25 Figure 14. Stormwater runoff total phosphorus concentrations within Sunshine Lake/ Sunrise

Waterway. .............................................................................................................................. 25 Figure 15. Surface geology in vicinity of Sunshine Lake / Sunrise Waterway (TQsu = Shelly sediments

of Plio-Pleistocene, Thp = Peace River Formation). Figure derived from Scott et al. (2001) ............................................................................................................................................... 26

Figure 16. Seepage TN concentrations within Sunshine Lake/ Sunrise Waterway. .............................. 28 Figure 17. Seepage total phosphorus concentrations within Sunshine Lake/ Sunrise Waterway. ........ 28 Figure 18. Surficial Aquifer TN concentrations within Sunshine Lake/ Sunrise Waterway. ................... 30 Figure 19. Surficial Aquifer total phosphorus concentrations within Sunshine Lake/ Sunrise Waterway. . ............................................................................................................................................... 30 Figure 20. Surface water fecal coliform bacteria concentrations (cfu / 100 ml) within Sunshine Lake/

Sunrise Waterway (data have been log10 transformed). ....................................................... 33 Figure 21. Stormwater runoff fecal coliform bacteria concentrations (cfu / 100 ml) within Sunshine

Lake/ Sunrise Waterway (data have been log10 transformed). ............................................. 34 Figure 22. Plan view of three design approaches for FTW in a stormwater detention basin (cross-

hatching represents FTWs) (after Headley and Tanner 2006). ............................................ 38 Figure 23. Cross-section of a typical FTW and pond showing main structural elements (from Headley

and Tanner 2006). ................................................................................................................. 38 Figure 24. Potential plant species for shoreline vegetation planting project Top: soft stem bulrush.

Middle: pickerel weed. Bottom: water lily and spikerush. ...................................................... 39


Atkins Final Report January 2015 iii

Figure 25. Schematic of proposed artificial circulation system using SolarBee system. ....................... 40 Figure 26. Gravity sewer lines recently lined by Charlotte County. ........................................................ 44


Atkins Draft Report November 2014 1

1. Background

The Sunshine Lake/Sunrise Waterway system, in Charlotte County, has recently experienced extensive and persistent algal blooms (Figure 1). The lake itself is approximately 8 ½ acres in size, with a watershed (the area of land draining to it) of approximately 297 acres. The open water area of the Sunrise Waterway, operationally defined here as the open waters south of Gertrude Avenue and north of US 41, is approximately 3.7 acres in size, with a contributing watershed that is not definitely known. Based on aerial photography the algal bloom is apparent as far back as 2008 as a feature both in the area adjacent to the County Park along Elkcam Boulevard, and also in the northeast corner of the lake. According to long-term residents, the Sunshine Lake/Sunrise Waterway went from being a relatively healthy system with good water clarity and a mostly sandy bottom to an algae-clogged lake, with noxious odors and a deep mat of algal-covered sediments. This relatively rapid degradation suggests that the lake’s problems might reflect relatively recent, and potentially ongoing, sources of degradation. In particular, a number of stressors might have presented themselves in and around the later part of the last decade, rather than the gradual and slow degradation that is often seen in other highly eutrophic lakes.

Figure 1. Sunshine Lake/Sunrise Waterway and its approximate watershed


Atkins Final Report January 2015 2

The spatial extent of the algal mat (approximately 50% of the lake’s volume) was determined through a detailed mapping and bathymetry effort (Atkins 2012). That report (Atkins 2012) developed a GIS-based delineation of the lake’s watershed, gathered data on the spatial distribution of stormwater conveyances, structures, sewer lines, etc. in the Sunshine Lake/Sunrise Waterway watershed, as well as local regional use of both sewer and in-ground septic systems. Also, Atkins collected and analyzed lake sediment samples for the water column and the algal mat itself for the following parameters: percent organic content, total nitrogen (TN), total Kjeldahl nitrogen (TKN), nitrate+nitrite (NOx), total phosphorus (TP), ortho-phosphorus (PO4).

Based on these findings, the quantity of nitrogen and phosphorus required to account for the algal biomass was derived, and the quantity compared to a variety of potential sources. Estimates of potential nutrient sources were preliminary and speculative, but the grassy swales and lack of curb and gutter stormwater conveyance in the lake’s immediate watershed suggested that the algal bloom might not have been caused by stormwater runoff alone. However, it must be clearly stated that the actual nutrient source(s) required for an algal bloom of this intensity had not been identified with any certainty prior to the publication of that report.

A list of proposed restoration projects was included in Atkins (2012), including dredging the lake, removing the cattail fringe, and installing a well to decrease residence times. As of fall of 2014, the removal of the algal biomass from the lake appears to be complete. However, determining the sources of nutrients that might have allowed this bloom to occur in the first place remains important, so that sources can be acted upon (if still present) to reduce the probability of a re-occurrence of blooms in the future. In their preliminary diagnostic study, Atkins (2012) pointed out the need for additional technical assessments, most importantly a more detailed assessment of the source(s) of the excessive nutrient loads that seem to have allowed the algal bloom to develop. A more detailed assessment of the potential influence of both surface inflows and groundwater seepage is the first step that needs to be conducted in the production of a detailed management plan for Sunshine Lake and the Sunrise Waterway.

In response to Charlotte County’s Request for Proposals (RFP No. 2013000416) titled “Sunshine Lake / Sunrise Waterway Management Plan” Atkins proposed an approach based on a number of tasks, including both those efforts specific to nutrient characterization alone, as well as an outline of tasks and costs with which the techniques, results and interpretation of collected data were conveyed to the general public and various policy makers. In greater detail, these tasks included the following:

1. A monitoring phase that involved the collection of data on stormwater runoff and groundwater inflows into the Sunshine Lake/Sunrise Waterway. Prior to initiating these data collection efforts, public outreach and interaction with local stakeholders was encouraged to through a public meeting held April 22, 2014 to ensure that local stakeholders were aware of the need and value of such efforts.

2. After a 6-month data collection phase, results were analyzed and interpreted so that appropriate actions can be undertaken to minimize the return of the noxious algal blooms that existed in the lake prior to their removal.

3. With results interpreted in terms of their implications, a design phase will be initiated wherein different potential projects will be considered and cost estimates prepared for the construction, operation and/or maintenance of required projects.

4. The results from the monitoring and design phases would be combined into a Watershed and Waterways Management Plan for Sunshine Lake and the Sunrise Waterway.

This report presents the results of the water budget (Section 5.2), nutrient budget (Section 5.3), nutrient and bacteria source identification efforts (Section 5.4.2) based on the water quality data collected over the six month monitoring period. The data compiled, analyzed and interpreted were used to determine the most likely stressors that could have caused the algal bloom in Sunshine Lake and the Sunrise Waterway. This information was used to develop a conceptual management plan, including the types of projects, the sequencing of installation of such projects, and the cost estimates to design, permit, construct and maintain all required projects and programs. The proposed management actions were in



turn informed by the results of this study, which identified the source(s) of the nutrient loads that were likely responsible for the initial algal bloom in Sunshine Lake and the Sunrise Waterway.

2. Data collection and analysis

A 6-month water quality monitoring effort was performed over the period of May 2014 through October 2014. The monitoring effort was designed to provide a quantitative measurement of the potential pollutant loads to the Sunshine Lake/Sunrise Waterway system. The following sources of pollutant loads were monitored: 1) the open waters of the lake and waterway, 2) stormwater inflows into the lake, 3) groundwater seepage into the lake, and 4) the surficial aquifer. Sampling locations are indicated in Figure 2. The water quality results were analyzed to determine if there is evidence of elevated levels of nutrients and/or bacteria in samples collected from the sampling locations. The procedures related to the collection and analysis of groundwater elevations, groundwater seepage, stormwater runoff, and surface water are provided within Section 2.



Figure 2. Monitoring effort sampling locations.

2.1. Surface water Grab samples were collected at surface water sites located adjacent to groundwater seepage monitoring locations (Figure 2). Water quality samples were collected and immediately iced in a cooler and analyzed once each calendar month for a period of six months (6 total events) using standard techniques related to collection, transport and analysis (Table 1). Surface water samples were assessed by Benchmark EnviroAnalytical for nutrients (TN, TKN, ammonia as N (NH4-N), NOx, TN, PO4) and bacteria levels (fecal coliform bacteria). A YSI

© 6250 was used for each monthly water quality trip to measure in

situ water temperature, dissolved oxygen, salinity and conductivity of the lake water. The YSI was calibrated and post-checked each sampling day.

Table 1. Monthly sampling event dates.

Month Sampling Event Date

May 5/29/2014

June 6/19/2014

July 7/29/2014*

August 8/13/2014

September 9/11/2014

October 10/21/2014

*The July 2014 sampling event for SEEP-2 was completed on 8/4 due to equipment damage and subsequent replacement

2.2. Stormwater runoff Monitoring equipment was installed at three locations adjacent to the lake where surface water inflows were likely to occur (Figure 2). Teledyne ISCO Avalanche portable refrigerated samplers were used to collect composite stormwater samples. Teledyne ISCO Flow Modules, which attach to the samplers, were used to continuously measure water flow rates. An ISCO 674 tipping bucket rain gauge was installed at the inflow monitoring sites. The rain gauge continuously measured and recorded rainfall amounts and sent rainfall quantity information to the sampling equipment. Stormwater samples were collected after at least 0.2 inches/hour of rainfall had been recorded (Figure 3; Table 2). While rainfall distribution did not differ substantially between the stormwater sampling locations, the timing of sampling events varied. This was likely due to the relative difference in the contributing drainage areas upstream of each sampling location. Standing water was present at STWR-1; therefore, the sampling trigger was based on a combination of rainfall and flow. In contrast, STWR-2 and STWR-3 experienced intermittent flow, and the sampling trigger was thus based on a combination of rainfall and water level within the discharge pipe. Sampling events at STWR-2 and STWR-3 were contingent upon a sufficient rise in the surficial aquifer water levels to result in discharge from the stormwater outfalls.

All monitoring equipment was prepared, installed and maintained in accordance with standard techniques, as described in the Sampling Plan report produced for this project. Stormwater samples were assessed by Benchmark EnviroAnalytical for nutrients (TN, TKN, NH4-N, NOx, TN, ortho-phosphorus) and bacteria levels (fecal coliform bacteria).



Figure 3. Total daily rainfall and stormwater runoff sampling events at the three sampling sites.

Table 2. Stormwater sampling events at the three sampling sites. Shaded cells indicate sample was collected.

DATE STWR-1 STWR-2 STWR-3

28-May-14 0.62 0.68 0.62

14-Jun-14 0.77 0.84 0.59

16-Jun-14 0.55 0.37 0.37

26-Jun-14 0.48 0.46 0.27

7-Jul-14 1.56 1.21 1.51

9-Jul-14 0.99 0.85 0.85

14-Jul-14 0.78 1.01 1.1

16-Jul-14 0.43 0.47 0.5

26-Jul-14 0.31 0.18 0.28

29-Jul-14 0.44 0.45 0.45

3-Aug-14 1.6 1.49 1.58



DATE STWR-1 STWR-2 STWR-3

7-Aug-14 0.52 0.91 0.69

14-Aug-14 0.56 0.52 0.53

15-Aug-14 0.4 0.39 0.38

9-Sep-14 1.09 1.02 0.92

17-Sep-14 - 0.81 0.87

20-Sep-14 1.86 2.13 2.09

21-Sep-14 0.41 0.47 0.47

27-Sep-14 1.33 1.28 1.28

15-Oct-14 0.39 0.41 0.44

2.3. Groundwater seepage

After installation of a seepage meter at the station locations shown in Figure 2, a sample bag was deployed and the volume of seepage was measured approximately every two to four weeks over the study period of six months starting in May 2014 (Table 3). The July 2014 sampling event at SEEP-2 was completed on August 4, 2014 due to equipment damage and subsequent replacement. During each sampling trip, the volume collection bag was removed and then replaced with a new sampling bag. Monthly water quality samples were collected directly from the sampling bag, immediately iced in a cooler, and analyzed. The condition of the bag (holes/no holes) and water collected (color, smell, particles) was recorded for each groundwater seepage meter site. Groundwater seepage samples were assessed by Benchmark EnviroAnalytical for nutrients (TN, TKN, NH4-N, NOx, TN, and PO4) and bacteria levels (fecal coliform bacteria). The quantity of water in the sample collection bag was measured using a graduated cylinder. The area-normalized seepage rate (L/m

2d

1) for each sampling site was calculated as

follows:

Seepage rate (liters m-2

d-1

) = V/(A x T)

Where,

V = volume (liters), A=area (m2) and T= time (d)

Table 3. Groundwater Seepage completed sampling trips

Date Analysis Completed

5/12/2014 Seepage Meters Installed

5/29/2014 Water Quantity and Quality



8/4/2014 SEEP-2 Water Quantity and Quality

8/13/2014 Water Quantity




Date Analysis Completed






10/21/2014 Seepage Meters Removed

2.4. Surficial aquifer The three monitoring wells (Figure 2) were constructed using hollow stem auger (HSA) techniques with a high torque truck-mounted HSA drill. This drilling method uses a series of continuous flight augers (CFA) approximately five feet long. The CFA method is a non-displacement system, i.e., the volume of material excavated is designed to equal to the volume of the augers inserted into the ground. This results in no net displacement of the soil surrounding the well. The three wells were installed flush to the ground to minimize their visibility and to reduce interference with landscape maintenance. The wells were then capped with a Solinst cap to accommodate the Leveloggers.

The Solinst Leveloggers for each of the three surficial aquifer wells automatically recorded water levels on an hourly basis. Groundwater samples were collected monthly using standard techniques related to purging of sample volumes, collection, transport, and analysis, as outlined in the Sampling Plan produced for this project (Table 1). Water samples from the surficial aquifer were assessed by Benchmark EnviroAnalytical for nutrients (TN, TKN, NH4-N, NOx, TN, and PO4) and bacteria levels (fecal coliform bacteria).



3. Nutrient dataset comparison

The nutrient data collected as part of the monitoring effort were compared to literature derived limits to determine if they were within acceptable ranges for the region. When regulatory limits were not available, a comprehensive review of available data was performed to develop comparable limits.

3.1. Surface water For the surface waters of Sunshine Lake and the Sunrise Waterway, nutrient concentrations were compared to criteria established by the State of Florida, as contained in the Florida Department of Environmental Protection’s (FDEP) Surface Water Quality Standards (FAC 62-302). Within 62-302, there are guidance criteria for TN, TP, and also for the plant pigment chlorophyll-a, an indicator of the amount of algae within the water. Water quality data contained with the preliminary report conducted on Sunshine Lake and the Sunrise Waterway (Atkins 2012) and corroborated by the in situ data collected as part of the current monitoring effort indicate that the lake would be classified by FDEP as a low-color (platinum-cobalt units < 40) and high alkalinity (specific conductance > 100 µS / cm) waterbody. The impairment threshold for a low color, alkaline lake is 20 µg Chl-a / liter provided by FDEP in their Numeric Nutrient Concentration (NNC) criteria (FAC 62-302).

Based on the characteristics listed above, nutrient impairment of the open waters of Sunshine Lake and Sunrise Waterway would be designated if the annual geometric mean TN concentration exceeds 1.91 mg / liter, and if the annual geometric mean TP concentration exceeds 0.09 mg / liter (Table 4). Those TN and TP values are indicated for lakes where algal concentrations are deemed non-impaired, which is quantified as chlorophyll-a concentrations less than 20 µg Chl-a / liter. However, the algal bloom in Sunshine Lake and Sunrise Waterway appears to be associated with an algal mat growing up from the bottom, rather than phytoplankton floating in the water column. As an indicator of problematic algal blooms, it appears that the criteria of 20 µg Chl-a / liter fails to capture this local water quality problem. If, however, the local algal bloom is viewed as being functionally equivalent to a phytoplankton bloom, the TN and TP guidance criteria would be 1.05 and 0.03 mg / liter for TN and TP, respectively.

Table 4. Surface water criteria as defined by FDEP for Sunshine Lake/Sunrise Waterway.

Surface Water Not Problematic Problematic

TN (mg / liter) 1.05 to 1.91 > 1.91

TP (mg / liter) 0.03 to 0.09 > 0.09

3.2. Stormwater runoff Harper and Baker (2007) summarize water quality data collected throughout the state of Florida over a period from the 1977 to 2007. Of particular reference to Sunshine Lake are results from undeveloped landscapes as well as data from single family residential land uses, the dominant land use in the watershed of Sunshine Lake and Sunrise Waterway.

In the category of undeveloped / rangeland / forested land cover, overall mean TN and TP values for stormwater runoff were 1.15 and 0.055 mg / liter for TN and TP, respectively (Harper and Baker 2007). The range of TN values for runoff in undeveloped / rangeland / forested land cover was between 0.70 and 1.52 mg TN / liter. For TP, the range of values recorded was 0.02 to 0.10 mg TP / liter. In the category of single family residential land cover , overall mean TN and TP values for stormwater runoff were 2.07 and 0.327 mg / liter for TN and TP, respectively (Harper and Baker 2007). The range of TN values for runoff in single family residential land cover was between 1.02 and 3.99 mg TN / liter (one study had a slightly higher TN concentration in runoff, but data from that site were flagged as having problematic values for



TP). For TP, the range of values recorded was 0.102 to 0.510 mg TP / liter (one study had a much higher TP concentration in runoff, but results were flagged as being problematic). The category of “normal undeveloped” contains the range of values displayed in Harper and Baker (2007) for the categories of undeveloped / rangeland and forested landscapes. However, and as is discussed later in this report, the local geology may be naturally enriched in phosphorus, complicating the initial interpretation of our results based on data from other parts of Florida.

The category of “lower range developed” contains the range of values between the lowest mean value and the overall mean value for studies summarized in Harper and Baker (2007) for the category of single-family residential landscapes. The category “elevated developed” contains the range of values between the overall mean value and the highest mean value for studies summarized in Harper and Baker (2007) for the category of single-family residential landscapes. The category “excessive developed” refers to concentrations higher than the highest mean value for studies summarized in Harper and Baker (2007) for the category of single-family residential landscapes. Table 5 provides the TN and TP stormwater runoff concentrations ranges for various land-use categories for comparison with Sunshine Lake/Sunrise Waterway stormwater runoff concentrations.

Table 5. Comparable stormwater runoff TN and TP concentrations by land-use category.

Stormwater runoff Normal

undeveloped Lower range developed

Elevated developed

Excessive developed

TN (mg / liter) 0.070 to 1.52 1.02 to 2.07 2.07 to 3.99 > 3.99

TP (mg / liter) 0.002 to 0.100 0.102 to 0.327 0.327 to 0.510 > 0.510

3.3. Groundwater seepage For groundwater seepage, results were compared to results shown in PBS&J (2009). Concentrations of TN and TP were collected from groundwater seepage meters placed into both shallow and deep areas of Lakes Conine, Haines, Rochelle and Shipp, located in Polk County. As mentioned in Section 3.2, the local geology may be naturally enriched in phosphorus, complicating the initial interpretation of our results based on data from other parts of Florida.

In contrast to surface water samples and stormwater runoff, groundwater seepage has received much less attention, in terms of determining the range of values expected from undisturbed and urbanized landscapes. Also, groundwater seepage meters have been deployed in some locations without sufficient attention to the phenomenon of settling, which can give rise to inaccurate measurements (PBS&J 2009).

In a report conducted for FDEP, four lakes in Central Florida were studied to determine the quantity and quality of groundwater seepage coming into the lakes (PBS&J 2009). There were 3 to 6 samples taken over a 6 month period from each of four sites per lake; this represents a fairly robust data set.

The average TN concentration in groundwater seepage collected from the four lakes was 2.5 mg TN / liter, with a range of 0.4 to 14.3 mg TN / liter. The average TP concentration in groundwater seepage collected from the four lakes was 0.055 mg TP / liter, with a range from 0.002 to 0.373 mg TP / liter.

As opposed to stormwater runoff, there is a much more limited data set for nutrient concentrations in groundwater seepage from undeveloped landscapes. As such, the category of “normal undeveloped” displays the range of values below the lowest concentrations recorded from the developed watersheds that were sampled in the report by PBS&J (2009). The category of “lower range developed” contains the range of values from the lowest concentrations recorded up to the overall mean in the report by PBS&J (2009). The category “elevated developed” represents the range of values from the overall mean to the



highest concentration recorded in the report by PBS&J (2009). The category “excessive developed” refers to the highest concentrations recorded for groundwater seepage in the report by PBS&J (2009). Table 6 provides the TN and TP groundwater seepage concentrations ranges for various land-use categories for comparison with Sunshine Lake/Sunrise Waterway groundwater seepage concentrations.

Table 6. Comparable groundwater seepage TN and TP concentrations by land-use category.

Groundwater seepage

Normal undeveloped

Lower range developed

Elevated developed

Excessive developed

TN (mg / liter) < 0.40 0.40 to 2.50 2.50 to 14.3 > 14.3

TP (mg / liter) < 0.002 0.002 to 0.055 0.055 to 0.373 > 0.373

3.4. Surficial aquifer Similar to groundwater seepage, there is not as much data available to characterize the effects of undeveloped vs. urbanized landscapes on water quality in the surficial aquifer. Sonntag (1987) included some information that can be used to characterize TP concentrations in the Biscayne Aquifer, which is the surficial aquifer in Miami-Dade County. And data can be constructed to derive mean and maximum values for TN as well, by adding the individual nitrogen species that combined equate to TN. The results shown in Adamski and Knowles (2001) can be similarly combined to derive groundwater values for TN, but “phosphorus” data are only shown for dissolved phosphate (aka orthophosphate), not TP. In the Biscayne aquifer, there can be fairly significant differences between TP and orthophosphate concentrations (even when both expressed in units of mg / liter as P). Therefore, while TN guidance can be developed from both studies, only the results from Sonntage (1987) are used for screening for TP in the surficial aquifer. As mentioned in Section 3.2, the local geology may be naturally enriched in phosphorus, complicating the initial interpretation of our results based on data from other parts of Florida.

The average TN concentration in the Biscayne aquifer is calculated at approximately 0.53 mg TN / liter. The maximum concentration of ammonia nitrogen (as N) was 1.9 mg / liter, and the maximum concentration of nitrate plus nitrate (as N) recorded in the Biscayne aquifer was 3.4 mg / liter. The mean TP concentration in the Biscayne aquifer was 0.02 mg TP / liter, with a range from 0.01 to 0.07 mg TP / liter. In the study by Adamski and Knowles (2001) the median concentrations of TN from the surficial aquifer were 0.34 and 0.35 mg TN / liter, respectively, from the Ocala National Forest and developed areas within Lake County, respectively. Although median TN values did not vary much between developed and undeveloped landscapes in this study, there was separation between maximum values; the highest TN concentration in the surficial aquifers were 2.48 and 5.20 mg TN / liter, respectively, for sites in the Ocala National Forest and locations in Lake County, respectively.

Somewhat similar to the situation with groundwater seepage, there is a much more limited data set for nutrient concentrations in the surficial aquifer from undeveloped landscapes. As such, the category of “normal undeveloped” displays the range of values below the lowest concentrations recorded from the developed watersheds in the reports by Sonntag (1987) and Adamski and Knowles (2001). The category of “lower range developed” contains the range of values from the lowest concentrations recorded up to the overall mean in the reports by Sonntag (1987) and Adamski and Knowles (2001). The category “elevated developed” represents the range of values from the overall mean to the highest concentration recorded in the reports by Sonntag (1987) and Adamski and Knowles (2001). The category “excessive developed” refers to the highest concentrations recorded for groundwater seepage in the reports by Sonntag (1987) and Adamski and Knowles (2001). Table 7 provides the TN and TP surficial aquifer concentrations ranges for various land-use categories for comparison with Sunshine Lake/Sunrise Waterway groundwater seepage concentrations.



For phosphorus, proposed criteria may be problematic. The data set from Adamski and Knowles (2001) only included data on “phosphate” (as P) not “total phosphorus”. Data shown in Sonntag (1987) indicates that phosphate as P can underestimate the total amount of phosphorus in the surficial aquifer. However, the data from Sonntag (1987) is from the carbonate-rich Biscayne aquifer, which raises the potential problem that phosphorus would be absorbed onto the carbonate sediments of the aquifer matrix, rather than be distributed in the porewater itself.

Table 7. Comparable surficial aquifer TN and TP concentrations by land-use category.

Surficial aquifer Normal

undeveloped Lower range developed

Elevated developed

Excessive developed

TN (mg / liter) < 0.23 0.23 to 0.35 0.35 to 5.2 < 5.2

TP (mg / liter) < 0.01 0.01 to 0.02 0.02 to 0.07 > 0.07



4. Fecal coliform bacteria dataset comparison

The fecal coliform bacteria data collected as part of the monitoring effort were compared to literature derived limits to determine if they were within acceptable ranges for the region. When regulatory limits were not available, a comprehensive review of available data was performed to develop comparable limits.

4.1. Surface water Sunshine Lake and the Sunrise Waterway are classified as Class III freshwater waterbodies. This classification is often referred to as “fishable / swimmable” waters. As such, the relevant guidance for fecal coliform bacteria is that the number of colony forming units (cfu) per 100 ml of water shall not exceed a monthly average of 200, based on 10 sampling efforts per month. As very few entities sample that frequently, FDEP typically bases impairment status based on the standard that no more than 10 percent of samples shall exceed 400 cfu / 100 ml. If a single sample is collected on a waterbody, and its bacterial abundance exceeds 400 cfu / 100 ml, then it is also true that “more than 10 percent” of samples have exceeded 400 cfu / 100 ml. Additionally, a single value in excess of 800 cfu / 100 ml is sufficient to characterize a waterbody as “impaired” for fecal coliform bacteria.

In a 2003 report, researchers from the University of Florida suggested that lakes with fecal coliform bacteria concentrations between 0 and 200 cfu / 100 ml could be classified as “good”, while lakes with values between 200 and 800 could be considered “moderate”. Lakes with fecal coliform bacteria in excess of 800 cfu / 100 ml were characterized as “poor” (University of Florida 2003). Table 8 provides the surface water fecal coliform bacteria concentrations ranges for various land-use categories for comparison with Sunshine Lake/Sunrise Waterway bacteria concentrations.

Table 8. Comparable surface water fecal coliform bacteria concentrations by land-use category.

Surface water Good Moderately-

Good Moderately-

Poor Poor

Fecal Coliform Bacteria (cfu / 100 ml)

0 to 200 200 to 400 400 to 800 > 800

4.2. Stormwater runoff Typical fecal coliform bacteria concentrations for untreated stormwater runoff range from 10,000 to 100,000 MPN/100mL (Metcalf & Eddy 2003). Pitt (1983) compiled a comprehensive dataset of fecal coliform levels from urban stormwater collected as part of Early Urban stormwater studies. Those study results classified as having been collected from a “residential” land use were extracted from the database.

The minimum (50 cfu/100mL), average (13,000 cfu/100mL) and maximum (80,000 cfu/100mL) range of fecal coliform bacteria concentrations were determined to develop categories representative of typical urban stormwater values. The category of “Low” contains the range of values between the lowest value recorded and the mean minus 6,500. The category of “medium” contains the range of values of the mean ± 6,500. The category “High” contains the range of values between the mean plus 6,500 and the maximum. The category “Extreme” refers to concentrations higher than maximum value recorded. Table



8 provides the stormwater runoff fecal coliform bacteria concentration ranges for each category for comparison with Sunshine Lake/Sunrise Waterway bacteria concentrations.

Table 9. Comparable stormwater runoff fecal coliform bacteria concentrations by land-use category.

Stormwater runoff Low Medium High Extreme

Fecal Coliform Bacteria (cfu / 100 ml)

50-6,500 >6,500 to 19,500 >19,500 to

80,000 > 80,000



5. Data results and interpretation

The results of the monitoring effort performed at Sunshine Lake/Sunrise Waterway are presented in the section below. The results were analyzed and interpreted to determine the most likely source of nutrients, so that appropriate actions can be undertaken to minimize the likelihood of a return of the noxious algal blooms that existed in the lake prior to their removal.

5.1. Surficial aquifer and lake water elevation Water levels in the lake and the surrounding area were monitored via two staff gages and three monitoring wells (Figure 2). Lake levels were measured during every visit to the lake, at a minimum weekly. Groundwater levels were measured with a Solinst Levelogger (Solinst Canada, Ltd. Ontario, Canada), that records water levels at one-hour intervals and the data were downloaded at least monthly. Air pressure influence is compensated for by referencing the data recorded by the Solinst Barologger at the MW-3 site. A second compensation adjusts the elevation reading at the time of download to reflect the actual elevation of the groundwater measured by a water level meter. Note that hourly data for MW-3 are missing from June 4 (in part) through June 19 (in part) due to data logger failure. The loggers were removed on October 31.

Rainfall data were collected from the rain gages associated with each stormwater collection devices (Figure 3). Groundwater and lake level elevations are graphed against total daily rainfall (the average of the totals collected at the three collection sites) in Figure 4. The highest groundwater elevations occurred in late September through early October. The highest lake water levels occurred in early August. Based on the triangulation of the water elevations from the three monitoring wells, the direction flow of the surficial aquifer is west-southwest.



Figure 4. Groundwater and Lake Water Levels vs. Total Daily Rainfall during the Monitoring Period

The relationships between rainfall and water levels in the monitoring wells and lake were evaluated using regression analysis to examine changes in water levels against the total rainfall during specific time periods. Because groundwater elevations were recorded hourly, weekly time periods were used for their analysis. The changes in lake water levels were analyzed using the time duration between each staff gage observation, which ranged from one to ten days. The water level changes in the monitoring wells were calculated by subtracting the average of the hourly readings for the final day of the time period from the average of the hourly readings of the final day of the previous time period. The lake level elevations were calculated from the staff gage measurements. The total rainfall was the average of the three totals measured at the three rainfall collection stations.

The changes in groundwater level and total rainfall for each seven-day period are graphed in Figure 5, and the changes in lake level and total rainfall during each interval between lake level measurements are graphed in Figure 6. All slopes were positive, indicating increased water levels with greater rainfall. For example the slope of 0.40 seen for MW-1 indicates that the groundwater level rose 0.40 feet (4.8 inches) for every inch of rainfall and the slope of 0.08 seen for the two lake level locations indicates that the lake level rose 0.08 feet (1 inch) for every inch of rainfall. The R

2 values were high, especially in the

groundwater analysis, indicating that the total rainfall is largely responsible for the change in water elevation. All relationships were significant (p values < 0.05). This strong correlation between changes in water levels and the total rainfall indicate that rainfall is the primary factor affecting groundwater and lake levels and those water levels are not likely affected by another influence, such as groundwater pumping.

Figure 5. Change in Groundwater Level vs. Total Weekly Rainfall in the Monitoring Wells



Figure 6. Change in Lake Water Level vs. Total Rainfall

The results of the regression analyses are presented in Tables 10 and 11.

Table 10. Changes in Groundwater Elevation vs. Total Weekly Rainfall

Monitoring Well Slope R2

MW-1 0.40* 0.77

MW-2 0.43* 0.70

MW-3 0.40* 0.75

* Indicates significant relationship (p<0.05)

Table 11. Changes in Lake Water Elevation vs. Total Rainfall

Monitoring Well Slope R2

County Park 0.08* 0.39

Gertrude 0.08* 0.40


Another regression analysis was used to examine the possible correlation between groundwater levels and lake water levels. In these analyses the change in groundwater level was calculated by subtracting the daily average of the hourly readings on the day the staff gage was read from the daily average of the hourly readings of the day the gage was previously read.

The changes in lake water levels vs. changes in groundwater levels results are graphed in Figures 7 to 9. The results of the regression analysis are presented in Table 12. All slopes are positive indicating that lake levels rise with rising groundwater levels. The R

2 values are high for MW-2 and MW-3 but lower at



MW-1 meaning that the changes in lake water levels are more strongly correlated with changes in groundwater levels at MW-2 and MW-3 but less so for site MW-1. All relationships were significant (p-values < 0.05). It is possible that difference is explained by the fact that MW-1 is downstream of the lake and the lake could have a siphoning effect on the adjacent groundwater (MW-1 is 200 feet from the lake).

Figure 7. Change in Lake Water Elevation vs. Change in Groundwater Elevation in MW-1



Figure 8. Change in Lake Water Elevation vs. Change in Groundwater Elevation in MW-2

Figure 9. Change in Lake Water Elevation vs. Change in Groundwater Elevation in MW-2.

Table 12. Changes in Lake Water Elevation vs. Groundwater Elevation Total Rainfall

Monitoring Well

Staff Gage Location

Slope R2

MW-1 County Park 0.12* 0.14

Gertrude 0.13* 0.18


Gertrude 0.19* 0.55


Gertrude 0.19* 0.57


5.2. Water budget The water budget for the Sunshine Lake/Sunrise Waterway system was calculated based on the direct precipitation, estimated stormwater runoff, and groundwater seepage. The water budget was restricted to the period of May 2014 to October 2014 to correspond with the 6-month monitoring effort performed. Groundwater seepage was measured during the wet season and interpolation over the dry season would potentially result in an increase of the relative annual importance of seepage to the overall water budget, as surface water runoff would be expected to decline with reduced rainfall-induced stormwater runoff.



5.2.1. Direct precipitation The total precipitation was calculated using the hourly precipitation measurements collected at the stormwater sampling sites over the period of May 1, 2014 to October 31, 2014. The collection of data at the stormwater sampling site within the County Park (STWR-1) was discontinued on October 21, 2014 because sufficient samples had been collected. However, the observed rainfall at the other two locations (STWR-2 and STWR-3) over the period of October 21- October 31 was negligible (0.04 and 0.05 in, respectively). The average total precipitation for sites STWR-2 and STWR-3 was 28.82 inches (0.732 m) over the period of May 1 to October 31, 2014...

5.2.2. Stormwater runoff Stormwater runoff to the lake was calculated using the EPA National Stormwater Calculator (NSC; USEPA 2014). The calculator allows the user to input local soil conditions, land cover and rainfall data. There are three soils types identified within the watershed: Malatcha Urban Land Complex, Malatcha gravelly fine sand and Boca Fine Sand (Henderson 1984). The runoff potential for all three soil types is “moderately low” with a hydrologic group of B or C. Additionally, the soil drainage potential is slow draining at approximately 0.336 in/hr. For the purpose of the NSC, the rain gauge and evaporation rates at Punta Gorda were used. It was then estimated that half the watershed is undeveloped or was comprised of lawns and half with impervious material. Additionally, it was assumed that thirty percent of the impervious area would be treated within an infiltration basin. Based upon the above assumptions, it is estimated that 43 percent of the direct precipitation to the watershed will result in stormwater runoff (0.32m), 51 percent would be lost to infiltration (0.37 m), and 6 percent would be lost to evaporation (0.05m). These estimates match up within 10 percent of the runoff coefficients used to calculate stormwater runoff rates for residential land uses in the Sarasota Bay watershed (Heyl 1992).

5.2.3. Groundwater seepage A table of groundwater seepage summary statistics are provided in Table 13. Overall, site SEEP-3, located within the Sunrise Waterway, had the greatest median groundwater seepage rates (32.0 L/m

2d

1)

when compared to the seepage rates at the SEEP-1 and SEEP-2 locations (11.9 and 23.8 L/m2d,

respectively). Due to the non-normal distribution of the collected groundwater seepage data, non-parametric statistical analysis was completed for all groundwater seepage data. There was not a significant difference in median seepage rate between sites (Kruskal-Wallis, p>0.05). Using the overall median daily seepage rate (13.4 L/m

2d

1), the seepage rate over the period of May 16 to October 31 was

calculated (169 days) to be 2,265 L/m2 or 2.25 m.

Table 13. Groundwater seepage summary statistics (L/m2d

-1 )

Station Sample size Min Max Average Median St. Dev

SEEP-1 9 2.6 57.5 18.6 11.9 18.9

SEEP-2 9 4.3 45.1 21.6 13.4 17.0

SEEP-3 9 0.7 88.5 32.0 23.8 33.8

Sites Combined 27 0.7 88.5 24.1 13.4 24.2

5.2.4. Water budget results The water budget for Sunshine Lake/Sunrise Waterway was developed using both measured (direct precipitation and groundwater seepage) and estimated stormwater runoff data. Overall, groundwater seepage was identified as the prominent source of water to the system (68 percent; Table 14). The influence of groundwater on the lake level is further corroborated by the correlation between rainfall, groundwater levels and the lakes level as presented in Section 5.1. Direct precipitation accounted for 22 percent and stormwater runoff was estimated to contribute 10 percent of the water to the system (Table 14).



Table 14. Input components of the Sunshine Lake/Sunrise Waterway water.

Source

Water budget

(m) (Percent)

Stormwater runoff 0.32 10

Direct precipitation 0.73 22

Groundwater seepage from surficial aquifer 2.25 68

5.3. Nutrient budget The data from the Sunshine Lake/Sunrise Waterway monitoring effort are presented below in comparison with the available regional data. A boxplot was generated to graphical display the data for each station. Boxplots are complex, and a variety of schematic options are available when the boxplots are being designed. Figure 10 provides a descriptive schematic boxplot. In this report, the whiskers are drawn to 1.5 times the interquartile range (IQR), rather than the maximum and minimum values, which could be quite a bit higher if “outliers” were encountered. The term outlier refers to an unusually high or low value, but not an error, per se.

Figure 10. Schematic boxplot

Concentrations in exceedance of “typical” values found in similar landscapes were made by evaluating the median concentration for each station in comparison to the various categories identified in Sections 3 and 4. Geometric means were not calculated, as there was insufficient evidence to suggest the need for such a calculation (geometric means are often used if data continue to be non-normally distributed even after log transformation).

If nutrient concentrations in stormwater runoff, groundwater seepage and/or the surficial aquifer are substantially higher than values seen in other developed landscapes, then it could be that there are unique sources of nutrient loads in the watershed, above and beyond those typically encountered in an urbanized landscape. If nutrient concentrations in stormwater runoff, groundwater seepage and/or the



surficial aquifer are mostly in-line with expectations from an urbanized watershed, then perhaps there is something unique about Sunshine Lake and the Sunrise Waterway that makes it more susceptible to nutrient loads than the typical lake in an urban setting.

It is anticipated that nutrient concentrations from stormwater runoff and other sources would include values higher than those typically recorded from undeveloped landscapes in Florida, since the watershed is in fact completely developed. This Technical Report addresses the more relevant question - “Are nutrient concentrations in stormwater runoff substantially higher than values typically seen in urbanized watersheds?” Similarly, nutrient concentrations in both groundwater seepage and the surficial aquifer would be expected to be higher than samples from an undeveloped landscape; this Technical Report addresses the more relevant question of “Are they higher than concentrations typically seen in areas with similar levels of development?” As mentioned first in Section 3.2, the local geology in the watershed could result in phosphorus concentrations that are not expected based on a state-wide data base, but might be “normal” for this local watershed.

5.3.1. Surface water A table of summary statistics are provided in Tables 15 and 16 for the field and laboratory surface water samples collected (Figure 2). The TN and TP concentrations for each site (respectively) were compared to the FDEP NNC state standards and are within the range of values that would not cause concern (Figures 11 and 12). However, the algal bloom in Sunshine Lake and the Sunrise Waterway was not a phytoplankton bloom, it was an algal mat that was associated with the lake bottom and which was then removed from the lake by dredging. The surface water guidance developed here may not be useful for characterizing the nutrient status of the lake and waterway if the nutrients loaded to these waterbodies are taken up by a similar algal mat as what originally occurred. Subsequently, results from the water column itself could be low because of low rates of loading, or they could be low because of an alternative nutrient sink (e.g., a re-forming algal mat). Or it could be that low levels of nutrients in the water column indicate that the assimilative capacity of the lake is such that algal growth might not be problematic within the water column itself (although a problem within the algal mat). The results from surface water sampling should thus be interpreted with caution.

Table 15. Laboratory analyzed surface water quality summary statistics.

Parameter (mg/L) Station Sample size

Minimum Maximum Average Median Standard deviation

Ammonia as N SURF-1 6 0.008 0.188 0.057 0.014 0.076

Ammonia as N SURF-2 6 0.008 0.015 0.010 0.008 0.003

Ammonia as N SURF-3 6 0.008 0.024 0.012 0.009 0.007

Chlorophyll-a-Corrected* SURF-1 6 5.82 15.80 9.52 8.43 4.03



Nitrate+Nitrite (as N) SURF-1 6 0.004 0.170 0.033 0.005 0.067



Orthophosphate as P SURF-1 6 0.002 0.020 0.009 0.006 0.008





Total Kjeldahl Nitrogen SURF-1 6 0.5 1.1 0.8 0.7 0.2



Total Nitrogen SURF-1 6 0.5 1.1 0.8 0.7 0.3



Total Phosphorus SURF-1 6 0.01 0.06 0.03 0.03 0.02



*units in µg/L

Table 16. Field measured surface water summary statistics.

Site Parameter Units Minimum Maximum Average

SURF-1

Temperature C 26 32 30

Conductivity ms/cm 462 552 510

Salinity

0.2 0.3 0.2

Dissolved Oxygen mg/L 5.2 9.1 7.3

DO Saturation % 43 114 91

SURF-2



Salinity

0.2 0.2 0.2

Dissolve Oxygen mg/L 7.0 9.1 7.9


SURF-3



Salinity

0.2 0.3 0.3

Dissolved Oxygen mg/L 6.4 10.4 8.0




Figure 11. Surface water TN concentrations within Sunshine Lake/ Sunrise Waterway.

Figure 12. Surface water total phosphorus concentrations within Sunshine Lake/ Sunrise Waterway.

5.3.2. Stormwater runoff The major land use within the Sunshine Lake watershed is residential, which has been found capable of producing significant nutrient loads to receiving water bodies in prior studies (e.g., Heyl 1992). However,

SURF-1 SURF-2 SURF-3

Station

0.0

0.5

1.0

1.5

2.0

To

tal N

itroge

n (m

g/l)

Surface water Total Nitrogen concentration (Sunshine Lake/Sunrise Waterway)


Station

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

Tota

l Pho

spho

rus

(mg/

l)

Surface water Total Phosphorus concentration (Sunshine Lake/Sunrise Waterway)

Total Phosphorus Maximum

Total Nitrogen Maximum



most of the stormwater conveyance system throughout the watershed appears to be via grassy swales, which have been shown to reduce the quantity of stormwater runoff, and also to reduce the concentrations of nutrients and suspended materials (e.g., PBS&J 2010). Regional inflows of stormwater runoff into Sunshine Lake occur mostly via inflows from grassy swales, which act as a type of Best Management Practice (BMP) for stormwater treatment in developed landscapes. Even in locations where stormwater is routed through pipes prior to discharge into the lake, such as the stormwater pipe that collects runoff at the northwest corner of Indiana Avenue and Elkcam Boulevard (south of the tennis courts), the runoff that enters into the pipe was first “treated” through the BMP of grassy swales. Stormwater runoff into Sunshine Lake is most likely lower in nutrients and suspended materials than would be the case if most runoff was routed to the lake via curbs and gutters and direct discharge via pipes. A table of summary statistics are provided in Table 17 for the stormwater runoff samples collected (Figure 2). Figure 13 shows that the levels of TN in stormwater runoff are only moderately enriched at STWR-3, compared to concentrations expected from an urbanized watershed. Median TN concentrations at STWR-1 and STWR-3 are both within the “normal undeveloped” categories. In contrast, the TP median concentrations are well within the range of “excessive developed” at all three stormwater sampling sites (Figure 14). The term “excessive developed” refers to values that are not only elevated above the normal values found for urban watersheds, but values that are elevated above the highest values contained within the cited data sets (Figure 14). These findings suggest that TP values, much more so than TN, are far in excess of those that would be expected to occur in stormwater runoff from the typical urbanized watershed.

Table 17. Stormwater runoff water quality summary statistics.

Parameter (mg/L) Station Sample size Minimum Maximum Average Median

Standard deviation

Ammonia as N STWR-1 12 0.008 0.347 0.090 0.050 0.108

Ammonia as N STWR-2 12 0.008 0.360 0.061 0.033 0.100

Ammonia as N STWR-3 11 0.032 5.040 1.003 0.334 1.502

Nitrate+Nitrite (as N) STWR-1 12 0.004 0.752 0.232 0.212 0.200



Orthophosphate as P STWR-1 12 0.23 1.18 0.41 0.31 0.28



Total Kjeldahl Nitrogen STWR-1 12 0.7 3.6 1.3 0.9 0.8



Total Nitrogen STWR-1 12 0.8 4.4 1.5 1.1 1.0



Total Phosphorus STWR-1 12 0.32 1.75 0.68 0.58 0.38





Figure 13. Stormwater runoff TN concentrations within Sunshine Lake/ Sunrise Waterway.

Figure 14. Stormwater runoff total phosphorus concentrations within Sunshine Lake/ Sunrise Waterway.

Two factors, considered together, suggest that the elevated levels of TP are not necessarily due to human-related pollution. First, the levels of TN are not similarly as elevated as TP. If elevated levels of TP were due to influences such as fertilizer application and/or sewage or pet wastes, similarly consistent

STWR-1 STWR-2 STWR-3

Station

0

2

4

6

8

10

Tota

l Nitr

oge

n (m

g/L

)

Storm water runoff Total Nitrogen concentration (Sunshine Lake/Sunrise Waterway)


Station

0.0

0.5

1.0

1.5

2.0

Tota

l Pho

spho

rus

(mg/

L)

Storm water runoff Total Phosphorus concentration (Sunshine Lake/Sunrise Waterway)

Normal Undeveloped

Lower Range Developed

Elevated Developed

Excessive Developed

Normal Undeveloped


Elevated Developed

Excessive Developed



elevated levels of TN would also be expected. Second, Charlotte County has surface geology that includes the phosphorus-rich soils of the Peace River Formation (Figure 15).

Figure 15. Surface geology in vicinity of Sunshine Lake / Sunrise Waterway (TQsu = Shelly sediments of Plio-Pleistocene, Thp = Peace River Formation). Figure derived from Scott et al. (2001)

Soils of the Peace River Formation are enriched enough to warrant mining interest in locations where land uses and the cost of land allow for such. Although the Peace River Formation is shown as ending just east of Port Charlotte, Scott et al. (2001) note that the boundaries shown in their maps are approximate, and that soils grade into each other at their boundaries. The report “Soil Survey of Charlotte County” by Henderson (1984) shows the soils directly adjacent to Sunshine Lake and the Sunrise Waterway as being in the Matlacha Urban Land Complex. In Charlotte County, that soil complex was described as having a “VERY HIGH potential for P movement from the site and for an adverse impact on surface waters” (Table 13 in Hurt et al. 2013). The basis for the high potential for adverse impacts on surface waters is not specifically addressed by Hurt et al. (2013).

The combination of close proximity of the Peace River Formation, which is extremely enriched in phosphorus, and the noted “very high” potential for adverse impacts to water quality from soils directly adjacent to Sunshine Lake and the Sunrise Waterway could be associated with an increased susceptibility of the lake and waterway, especially if nitrogen-fixing cyanobacteria became established in these same waters, or if some other factor might be involved in adding a pulse of nitrogen into the lake. It is thus possible that elevated levels of TP in stormwater runoff represent a condition related to “natural” sources of phosphorus based on local geology, rather than being related to human pollutant sources.

With an ability to access the unlimited pool of atmospheric di-nitrogen gas, cyanobacteria in these waters would in essence not be limited by either phosphorus or nitrogen. Or, it could be that a past event (e.g., Hurricane Charley in 2004) might have loaded sufficient nitrogen to the lake to have primed the lake with both nutrients, allowing the algal bloom to initiate and grow.

5.3.3. Groundwater seepage Summary statistics for the monthly groundwater seepage samples collected are provided in Table 18. The median TN and TP concentrations are within the “lower range developed” category (Figures 16 and



17, respectively). The nutrient groundwater seepage concentrations are within the range of values that would not cause concern.

Table 18. Groundwater seepage water quality summary statistics.



Ammonia as N SEEP-1 6 0.015 0.259 0.104 0.067 0.101

Ammonia as N SEEP-2 6 0.008 0.303 0.107 0.050 0.127

Ammonia as N SEEP-3 6 0.021 0.730 0.292 0.301 0.261

Nitrate+Nitrite (as N) SEEP-1 6 0.006 0.042 0.023 0.020 0.014



Orthophosphate as P SEEP-1 6 0.002 0.019 0.013 0.015 0.007



Total Kjeldahl Nitrogen SEEP-1 6 0.3 1.4 0.7 0.6 0.4



Total Nitrogen SEEP-1 6 0.3 1.4 0.7 0.6 0.4



Total Phosphorus SEEP-1 6 0.01 0.08 0.03 0.02 0.03





Figure 16. Seepage TN concentrations within Sunshine Lake/ Sunrise Waterway.

Figure 17. Seepage total phosphorus concentrations within Sunshine Lake/ Sunrise Waterway.

5.3.4. Surficial aquifer Summary statistics for the monthly surficial aquifer samples collected are provided in Table 19. The median TN concentrations are within the “elevated developed” category for all three surficial aquifer sites (Figures 18). No values for TN within the range of “excessive developed” values. In contrast, the median

SEEP-1 SEEP-2 SEEP-3

Station

0

3

6

9

12

15

Tota

l Nitr

oge

n (m

g/L

)

Seepage Total Nitrogen concentration (Sunshine Lake/Sunrise Waterway)

SEEP-1 SEEP-2 SEEP-3

Station

0.0

0.1

0.2

0.3

0.4

0.5

Tota

l Pho

spho

rus

(mg/

L)

Seepage Total Phosphorus concentration (Sunshine Lake/Sunrise Waterway)

Normal Undeveloped


Elevated Developed

Excessive Developed

Normal Undeveloped


Elevated Developed

Excessive Developed



TP concentrations are within the range of “excessive developed” (Figure 19), which could reflect the natural abundance of P-rich sediments discussed in the previous section on stormwater runoff.

Table 19. Surficial aquifer water quality summary statistics.



Ammonia as N MW-1 6 0.098 0.166 0.121 0.113 0.027

Ammonia as N MW-2 6 0.008 0.032 0.012 0.008 0.010

Ammonia as N MW-3 6 0.008 0.057 0.034 0.030 0.019

Nitrate+Nitrite (as N) MW-1 6 0.004 0.159 0.097 0.108 0.059



Orthophosphate as P MW-1 6 0.002 0.031 0.015 0.013 0.010



Total Kjeldahl Nitrogen MW-1 6 0.3 0.5 0.4 0.4 0.1



Total Nitrogen MW-1 6 0.4 0.6 0.5 0.5 0.1



Total Phosphorus MW-1 6 0.05 0.39 0.13 0.08 0.13





Figure 18. Surficial Aquifer TN concentrations within Sunshine Lake/ Sunrise Waterway.

Figure 19. Surficial Aquifer total phosphorus concentrations within Sunshine Lake/ Sunrise Waterway.

5.3.5. Nutrient budget results The contribution of each component to the nutrient budget for Sunshine Lake/Sunrise Waterway was calculated by multiplying the overall median nutrient concentration (mg/L) by the relative hydrologic

MW-1 MW-2 MW-3

Station

0

1

2

3

4

5

6

To

tal N

itro

gen

(mg/

L)

Surficial Aquifer Total Nitrogen concentration (Sunshine Lake/Sunrise Waterway)

MW-1 MW-2 MW-3

Station

0.0

0.2

0.4

0.6

0.8

1.0

Tota

l Pho

spho

rus

(mg/

L)

Surficial Aquifer Total Phosphorus concentration (Sunshine Lake/Sunrise Waterway)

Normal Undeveloped Lower Range Developed

Elevated Developed

Excessive Developed

Excessive Developed

Elevated Developed Lower Range Developed

Normal Developed



contribution (m). This value was then multiplied by the area of the waterbody (12.2 acre or 49,372 m2).

The result was converted to kilograms for ease of comparison. In regards to the stormwater runoff, the TN and TP load to the lake were 22 and 12 kg, respectively. For groundwater inputs, the TN and TP component were calculated using the median groundwater seepage concentrations which accounted for 64 and 3 kg, respectively. The TN and TP atmospheric deposition was estimated at 5.5 (0.55 mg/L) and 1.01 kg/ha (0.101 mg/L; Dixon et al., 1998; Frog Creek, Manatee County). The resulting TN and TP load related to direct precipitation was 11 and 0.4 kg, respectively.

Overall, groundwater inputs were identified as the prominent source of nitrogen to the system (60 percent; Table 20). Direct precipitation explained 19 percent and stormwater runoff was estimated to contribute 21 percent of the nitrogen to the system (Table 20). Stormwater runoff contributed 78 percent and groundwater inputs accounted for 20 percent of phosphorus. Direct precipitation explained less than 1 percent of the overall phosphorus contribution to the lake and waterway. It is important to note that these results are calculated for the period of May to October 2014 which corresponds with a period of greater on average precipitation. As such, it is probable that the relative contribution of stormwater runoff and precipitation would decrease over an annual time period.

Table 20. Input components of the Sunshine Lake/Sunrise Waterway nutrient supply over the period of May 2014 to October 2014.

Source

TN TP

(kg) (Percent) (kg) (Percent)

Stormwater runoff 22 21 12 78

Direct precipitation 20 19 0.4 1

Groundwater inputs* 64 60 3 20

*values were calculated using the surficial aquifer nutrient concentrations

5.3.6. Possible scenario for nutrient source for algal bloom Based on data collected here, it appears that the amount of phosphorus coming into Sunshine Lake and the Sunrise Waterway is substantially elevated, compared to expectations from state-wide data sets from urbanized landscapes. However, as concentrations of nitrogen tended not to be as elevated as phosphorus concentrations, it does not seem that human activities are the source of the elevated phosphorus. If sewage spills or over-application of fertilizer was an issue, we would expect to see a pattern of consistently high levels of phosphorus and nitrogen in, for example, stormwater runoff. Based on information included in a report by Hurt et al. (2013) the high concentrations of phosphorus documented in stormwater runoff could be due to the region’s natural phosphorus-enriched surface geology.

Elevated levels of phosphorus loads to the lake and waterway are problematic for two reasons: 1) they appear to be sufficient to account for the mass of phosphorus that is embedded within the algal mat that characterized the lake, and 2) they would tend to make the lake susceptible to either an ongoing or an episodic load of nitrogen from some source. Potential sources of the nitrogen within the algal mat include the following: 1) nitrogen fixation by various species of cyanobacteria, 2) impacts associated with the passage of Hurricane Charley in 2004, or 3) some other episodic or ongoing nitrogen load, including the possibility of internal loading. Internal loading was not specifically investigated, because the organic materials that give rise to internal loading (as opposed to groundwater seepage, which was measured) were removed with the implementation of the County’s dredging project for the lake and waterway.

In some of the most hypereutrophic lakes in Florida, there have been direct measurements of nitrogen-fixation by cyanobacteria (e.g., Tomasko et al. 2009 and references therein). In such a situation, nitrogen is never “limiting” because cyanobacteria can access atmospheric di-nitrogen gas, a nutrient pool not



available to other algal groups. However, nitrogen fixation has not been directly measured in this circumstance, nor can it be measured now, since the algal mass has been removed via the successful lake dredging operation.

Another possible nitrogen source could be associated with the passage of Hurricane Charley, in 2004. In a study of changes in water quality in the Peace River and Charlotte Harbor, it was determined that areas located within 20 km (approximately 12 miles) of the eye wall were characterized by extremely poor water quality in the weeks after the passage of the hurricane, due to the input of massive amounts of organic matter from nutrient-rich leaves and other material that was stripped from vegetation, blown onto the ground, and washed into nearby surface waters by the accompanying and subsequent rainfall (Tomasko et al. 2006).

Finally, it is possible that the lake and waterway are so “primed” with phosphorus that ongoing nitrogen loads, even if they are not out of the ordinary, are able to stimulate algal growth. However, ongoing nitrogen loads do not seem to be sufficiently elevated to account for the massive amount of nitrogen contained within the algal mass that was removed by the County’s recently completed dredging project.

5.4. Fecal coliform bacteria The fecal coliform bacteria data from the Sunshine Lake/Sunrise Waterway monitoring effort are presented below in comparison with the available regional data. As with the nutrient results, a boxplot was generated to graphical display the data for each station.

5.4.1. Surface water Results shown in Figure 20 show that the median fecal coliform bacteria concentrations are within the “good” range for all surface water sites. However, there were individual sampling events which exceeded the 800 cfu/100mL (log10(800)=2.9) criteria. Therefore, the waterbody could be designated as “impaired” for fecal coliform bacteria. The summary statistics by sampling site are provided in Table 21 for fecal coliform bacteria.

(rest of page left blank on purpose)



Figure 20. Surface water fecal coliform bacteria concentrations (cfu / 100 ml) within Sunshine Lake/ Sunrise Waterway (data have been log10 transformed).

Table 21. Fecal coliform bacteria summary statistics for surface water (data have been log10 transformed).

Station Sample Size


SURF-1 6 1.3 2.7 2.0 2.0 0.5

SURF-2 6 1.0 2.1 1.5 1.5 0.4

SURF-3 6 1.0 2.8 1.9 2.0 0.6

5.4.2. Stormwater runoff As opposed to surface water, the median fecal coliform bacteria concentrations in stormwater runoff were within the “extreme” levels at STWR-2 (Figure 21). The median concentrations at STWR-1 and STWR-3 were in the “high” and “medium” categories, respectively. However, some of the individual values recorded were elevated above that with which has typically been measured within urban stormwater runoff (80,000 cfu / 100 ml). The summary statistics by sampling site are provided in Table 22 for fecal coliform bacteria.


Station

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Log1

0 (

Fec

al C

olif

orm

(cf

u/100m

L))

Surface water Fecal Coliform concentration (Sunshine Lake/Sunrise Waterway)

Good

Moderately-good

Moderately-poor

Poor



Figure 21. Stormwater runoff fecal coliform bacteria concentrations (cfu / 100 ml) within Sunshine Lake/ Sunrise Waterway (data have been log10 transformed).

Table 22. Fecal coliform bacteria summary statistics for stormwater runoff water (data have been log10 transformed).

Station Sample Size


STWR-1 12 3.3 5.2 4.3 4.3 0.6

STWR-2 12 3.8 5.9 4.9 4.9 0.6

STWR-3 11 3.3 5.3 4.2 3.9 0.7

In an effort to determine the source of the very high levels of fecal coliform bacteria found in some of the storm samples, additional analyses were conducted. It is important to note that regulatory criteria for fecal coliform bacteria are intended for application for (in the case of Sunshine Lake) “fishable and swimmable” waters; they are not intended to be applied to stormwater conveyances, which is the focus of this portion of the study. While fecal coliform bacteria have been used for decades as an indicator of risks to public health, many types of bacteria that are not pathogenic (i.e., disease-causing) also test positive as “fecal” coliform bacteria. In some locations, alternative tests for bacteria such as E. coli or Enterococci have been conducted. While these organisms are an improvement over the use of fecal coliform bacteria, these organisms are termed “facultative anaerobes” which means that they can grow and reproduce in soils and sediments, and thus are limited as an indicator of recent contamination. Consequently, tests were run with the use of the indicator bacteria within the genus Bacteroidetes, which are considered a better indicator of humans as a source than alternative indicator organisms such as E. coli and Enterococci. As bacteria in the genus Bacteroidetes are strict anaerobes, their presence is an indicator of recent contamination from fecal material. These bacteria are also more abundant in feces of warm-blooded animals than E. coli and Enterococci.


Station

0

1

2

3

4

5

6

Lo

g 1

0 (

Fec

al C

olif

orm

(cf

u/1

00

mL

))

Storm water runoff Fecal Coliform concentration (Sunshine Lake/Sunrise Waterway)

Medium

Extreme

High

Low



Water samples were collected and sent to a private laboratory in Miami which used a molecular biological technique, Polymerase Chain Reaction (PCR) to determine the presence of these indicator organisms by detecting the presence of DNA sequences from these organisms. In this way, an entire water sample can be tested for the indicator of human contamination. Based on preliminary results, the very high levels of fecal coliform bacteria found in stormwater do NOT, as of yet, appear to be due to humans as a primary source. The first round of results found no evidence of humans in any of the three stormwater samples. A second round did find evidence of human-derived bacteria, but the total quantity of bacteria that could be traced to humans as a source was well under 1 percent of the total amount of “fecal coliform” bacteria quantified. A similar test for dogs found evidence of bacteria from dogs in stormwater runoff, but also at levels of less than 1 percent of total “fecal coliform” bacteria.



6. Restoration projects to protect and restore water quality

Prior studies in Florida have focused on the development of lake management plans for hypereutrophic (severely nutrient-enriched) lakes. For the City of Winter Haven, PBS&J (2010 b) determined that the types of projects that have had the greatest success, in terms of restoration of water quality, have been those that focused on removing point sources of nutrient pollution, as well as activities that sought to reduce the impacts of past nutrient loading events. Past nutrient loading impacts can often continue to harm the ecology of lakes, even if those loads have been successfully acted upon. For the City of Winter Haven’s Chain of Lakes system, it was recommended that activities that removed or sequestered sediment nutrient pools were necessary to recover lost ecosystem functions, while large-scale stormwater retrofits had very little evidence of being a successful lake restoration technique (PBS&J 2010 b). A third technique, that of artificially increasing whole-lake circulation, was also encouraged for some of the smaller lakes in the Winter Haven Chain of Lakes (PBS&J 2010 b).

In Lake Hancock, widely considered to be the most polluted large-lake in Florida, the only two activities that had a reasonable chance of improving water quality were removing or sequestering the nutrient content of bottom sediments, and increasing the lake’s water level via modification of the outfall structure (Tomasko et al. 2009).

A summary of the recommended projects, listed below, which may improve water quality within the Lake Sunshine/Sunrise Waterway system are provided in this section:

Monitoring program

Floating treatment wetland

Artificial circulation (aeration)

Lake level augmentation

Salinity modification

Maintenance of stormwater conveyance systems

Programs to address potential illicit connections (PIC)

6.1. Monitoring program In the past year, a substantial dredging project was performed within Sunshine Lake/Sunrise Waterway to remove the algal material from the waterbody. This project is unlike the typical dredge project, in that the substance removed was biological. Therefore, it is feasible that the algal material could return to the lake. As such, an annual monitoring program for Sunshine Lake and the Sunrise Waterway focused on the identifying any potential re-occurrence of the algal mat so that corrective measures can be implemented. Since the algal bloom was not characterized by typical phytoplankton species, a traditional sampling program that focuses on the water column would not be, in and of itself, adequate.

It is recommended that a water quality program with quarterly sampling be undertaken, to meet data acquisition requirements of the State of Florida’s newly adopted Numeric Nutrient Concentration (NNC) criteria. The water quality monitoring program should include the following components:

Quarterly quantification of nutrients (both nitrogen and phosphorus) as well as chlorophyll-a within the surface water.

Taxonomic analyses of phytoplankton species, to identify potentially problematic species



Annual evaluation of the presence or absence of an algal bloom associated with the bottom of Sunshine Lake and Sunrise Waterway

The monitoring program would include the collection of surface water and benthic material. Quarterly monitoring of 12 surface water sites (9 in the lake and 3 within the waterway) would be collected and analyzed for total and dissolved nutrients (nitrogen and phosphorus), chlorophyll-a, phytoplankton speciation and fecal coliform bacteria. Additionally, quarterly benthic samples would be collected from 12 randomly selected sites within the lake and waterway and algal species identification performed. An annual assessment of the presence or absence of an algal bloom associated with the lake bottom will be performed at 50 randomly selected sites (30 within the lake and 20 within the waterway). The nitrogen and phosphorus concentration of the benthic material will be analyzed if the algal bloom is identified as present.

The combined water column and benthic monitoring effort should include quantitative criteria that, if exceeded, would trigger various levels of management attention up to and including various actions identified in the Waterway Management Plan. The annual cost estimate to implement this monitoring program is $50,000.

6.2. Floating Treatment Wetlands (FTWs) FTWs can provide an alternate means of reducing nutrients in the water column and improving water quality in the Sunshine Lake/Sunrise Waterway system. Water quality improvements in water that flows through wetlands have been documented extensively (Kadlec and Wallace 2009, DeBusk et al. 2005, Kadlec and Knight 1996) and the South Florida Water Management District has constructed over 40,000 acres of stormwater treatment wetlands to treat surface water runoff in the Everglades. Water leaving a wetland has lower dissolved and organic nutrient loads (via multiple pathways, e.g. plant assimilation, denitrification, immobilization, physical settling) when compared with the water flowing into the wetland. Even though FTWs are not specific to stormwater treatment or flow-through systems, they are anticipated to provide this same function.

A FTW is composed of emergent wetland vegetation suspended on the water surface by a buoyant raft. In contrast to wetland systems, research on FTWs is limited and they rely primarily on plant assimilation of nutrients (Figure 22, Hubbard 2010, Hubbard et al. 2004), and therefore must be harvested or nutrients will be returned to the water column following plant senescence. The nutrient removal efficiency is related to the amount of biomass produced by the selected vegetation (Hubbard 2010) and can therefore be maintenance intensive. Biomass harvesting can also be required of naturally floating vegetation (water hyacinths and duckweed). It is anticipated that the aesthetic vegetation islands also provide food and habitat for wildlife, including waterfowl, songbirds, frogs, and turtles (Floating Island International 2010). FTWs would only be used in situations where other options are not available and can be located so as not to impede navigation or shade submerged aquatic vegetation (SAV).

The raft systems and plant species are the most important considerations for a FTW (Headley and Tanner 2006). Design criteria to establish the size and distribution of FTWs required to treat a waterbody are presently unavailable (Headley and Tanner 2006). Three scenarios for FTW deployment in a stormwater pond are illustrated in Figure 23. Reduced dissolved oxygen levels in the water column below FTWs have been reported (Headley and Tanner 2006) and FTWs should not, therefore, extend across an entire lake. Several small FTWs throughout a lake are recommended for water quality restoration. Annual maintenance including plant harvesting is required. Plant biomass is a short term sink and annual harvesting of the plant biomass is required to permanently sequester the nutrient uptake and should occur in late fall/ early winter before the plants senesce and decay. Both cattails (Typha latifolia) and maidencane (Panicum hemitomon) were successfully documented to perform well in a FTW constructed in Georgia (Figure 24; Hubbard et al. 2004).



It must be stressed that the efficiency of FTWs is directly related to their maintenance. A series of FTWs placed in a waterway and adequately maintained can be an aesthetically pleasing water treatment system. A series of FTWs that are not adequately maintained can be a community eyesore with little benefit to the waterway.

Cost estimate: Representative from Beemats has been contacted to provide a cost estimate

Figure 22. Plan view of three design approaches for FTW in a stormwater detention basin (cross-hatching represents FTWs) (after Headley and Tanner 2006).

Figure 23. Cross-section of a typical FTW and pond showing main structural elements (from Headley and Tanner 2006).



Figure 24. Potential plant species for shoreline vegetation planting project Top: soft stem bulrush. Middle: pickerel weed. Bottom: spatterdock and spikerush.

6.3. Artificial circulation

Whole lake aeration via circulation may be used as a water quality improvement project to treat eutrophication in Sunshine Lake (Figure 25; Atkins 2012). This process is designed to use electric powered pumps to pull deeper water to the lake surface where it becomes aerated (Pastorak et al. 1981, 1982) while reducing phytoplankton productivity by transporting phytoplankton biomass to the deeper and thus darker portions of the water column (Cooke et al. 1993). If iron is the factor controlling sediment phosphorus release, total phosphorus concentrations in the water column may be reduced through the aeration of the sediment-water interface and subsequent adsorption of phosphorus to the ferric complexes (Stumm and Leckie 1971). Improvements in water quality following aeration in Florida lakes have included reductions in ammonia and chlorophyll, TN, and TP (Kolasa and Kang 2005, Cowell et al. 1987).



The water intake system associated with the artificial circulation pump can be positioned in the water column based upon the lake’s unique depth and sediment quality characteristics (Atkins 2012). Solar powered pumps (e.g., SolarBee®) can be used to reduce operation costs. The required number and size of the pumps is dependent on the lake’s water quality, depth, size, and non-point source inputs. Artificial circulation is recommended only for small lakes (<75 acres) with poor water quality; Sunshine Lake might be a good candidate for including this technique. In August 2010, SolarBee® provided a design and cost estimate for Lake Blue, a 54-acre lake in Florida’s Winter Haven Chain of Lakes. Given that each circulation pump is assumed to effectively circulate 16 to 20 acres, Lake Blue would require the purchase and installation of three SB10000 v 18 machines, totalling $160,000. In 2011, SolarBee® estimated that Huntsman Lake (approximately 29 acres in size) in Virginia would require the installation of one SB10000 v 18 unit, costing approximately $57,200. Based on these estimates, a single SB10000 v 18 unit would likely be sufficient for effective circulation in Sunshine Lake. A single unit would likely cost between $50,000 and $60,000. Operation and maintenance costs are difficult to estimate, but would be an additional cost to the purchase itself.

Figure 25. Schematic of proposed artificial circulation system using SolarBee system.


6.4. Lake level augmentation As reported in the Atkins 2012 document, it is not known, at present, whether lake levels within Sunshine Lake are lower year-round, or only during the wet-season, or only during the dry-season, or if they are lower at any times of the year. While there is some evidence of lowered lake levels there is no long-term gage data that provides proof. However, it is known that lowered lake levels appear to make lakes more susceptible to the impacts of nutrient enrichment (Tomasko et al. 2009, PBS&J 2010 b) and that if there is evidence of an alteration to the lake level that could be explained by a particular activity (e.g., clearing drainage ditches, etc.) then the possibility of having inadvertently lowered the lake level should be addressed. It is suggested that a weir structure that would function to raise the invert level of the large culvert at the Tamiami Trail frontage road could retain added water during normal dry-season draw downs.

Concurrent with an increase in water levels in the Sunshine Lake/Sunrise Waterway system through the installation of one or more weirs, the addition of a non-potable well to maintain lake levels in the dry-season is warranted. A well less than 6” in diameter, with a flow rate of less than 100,000 gallons per day (gpd) would not need a Water Use Permit from the Southwest Florida Water Management District, although it would need a Well Construction Permit. It is important to note that due to the high phosphorus concentrations identified within the surficial aquifer, the well should extend down to a water source that does not exhibit elevated nutrient concentrations.

Based on GIS-based assessments of the size and depth of the lake, it appears that Sunshine Lake is capable of holding approximately 10 million gallons of water. The addition of a 100,000 gpd water source could replace the lake’s entire volume over the course of approximately 100 days. That amount of time (100 days) is far in excess of the amount of time it would take to get a massive algal bloom in the lake; therefore it is unlikely that a permitted supplemental water supply could change the residence time enough to reduce algal biomass through any type of flushing action. However, such a well could benefit the lake as a way to offset decreases in lake levels during the months of April and May, the time of year when hypereutrophic lakes often have their worst water quality (e.g., Tomasko et al. 2009, PBS&J 2010 b). During those two months, lake evaporation rates are likely to be around 6 inches per month, or one foot of combined water loss during these two months combined.

A one-foot loss of water from a lake that is approximately 8 acres in size is 8 acre-feet, or 2.6 million gallons of water. In comparison, a water source of 100,000 gpd over 60 days (e.g., April and May) is an amount of 6 million gallons, a volume in excess of the amount of water likely lost via evaporation alone. Therefore, it is possible that a supplemental water well could more than offset water losses via evaporation during the driest times of the year, which could benefit the lake by maintaining a higher lake level during times of the year when hypereutrophic lakes are particularly susceptible.

The implementation of this project is currently in the planning stage with the Charlotte County Public Works department. The cost estimate for the design, permitting, and construction of this project is $300,000, including the installation of the recharge wells.

6.5. Salinity modification During discussions of potential mitigation measure that might be effective in controlling the potential reoccurrence of future algae blooms in the Sunshine Lake/Sunrise Waterway system, a suggested alternative was to investigate the possibility of pumping high saline water up into the system from west of U.S. 41 during the spring dry-season. In order to test the potential efficacy of this alternative an initial simple “bench top” qualitative test was run to assess the potential response of the systems algal mat to increased salinity.

6.5.1. Methods The following describes the initial procedures utilized to assess the potential benefits of seasonally increasing the conductivity of the lake/waterway system to control the reoccurrence of the previous extensive algal mat.

1. A series of near bottom samples (including algal mat) were collected during the morning from the

northeast corner of Sunshine Lake, and placed in a cooler.



2. A carboy of high conductivity coastal saltwater was collected along the coast near Placida later that

morning. Refractometer measurements indicated this coastal water had a salinity of 35 psu, which is

toward the high end of the usual >30 psu reading common in Alligator Bay at the downstream tidal end

of Sunrise Waterway.

3. That afternoon, all the near bottom lake samples were combined in a larger container, stirred and a 60

ml subsample was withdrawn. At calculated amount of the 35 psu coastal water was added to reach a

desired final salinity concentration, and a 50 ml subsample of the mixed waters was then placed in a

glass centrifuge tube. This procedure was repeated until triplicate samples had been prepared for each

of the final resulting salinity concentrations:

a. 0 psu (control using only lake water)

b. 4 psu

c. 8 psu

d. 12 psu

e. 18 psu

4. An exact duplicated set of an additional fifteen of samples prepared, differing in that two drops of liquid

plant fertilizer were added to each of the second set of tubes.

5. Samples were placed outside exposed to filtered sunlight in a caged pool area during the day and then

brought inside at night (to prevent large changes in temperature).

6. In practice, the highest salinity concentration tested (18 psu) would entail effectively adding/mixing

approximately half the volume of the Sunshine Lake/Sunrise Waterway system with downstream water

during the spring dry-season.

6.5.2. Initial Qualitative Results At weekly intervals over the three weeks of the study, the relative health of the algal mats at the bottom (and growing on the sides) of the centrifuge tubes, among the tested salinity levels, were compared using three differing qualitative measures.



Production of oxygen bubbles during light exposure – When exposed to filtered sunlight the algal mats produced sufficient O2 bubbles to float the developing algal mats to the surface of the centrifuge tubes. The mats then typically settled back to the bottom of the tubes during night. During the 1

st and

2nd

week there were no apparent differences in the amount of O2 bubbles produced by the algal mats among the five salinity treatment levels (0, 4, 8, 12 and 16 psu). By the end of the 3

rd week, there was a

relatively small apparent decline in the O2 production of the algal mats in the 12 and 16 psu tubes. In all instances, those tubes to which additional nutrients had been added uniformly developed more O2 bubbles.

Visual color of algal mat – Again, there was little apparent differences in the color (green/brown) of the algal mats among the tested five salinity treatments during the first two weeks. By the end of the third week, the mats in the tubes exposed to the highest salinity (18 psu) exhibited a very slight decline in color. As expected, those tubes to which nutrients were added were greener than those to which additional nutrients were not added.

Microscopic assessment of cell conditions – Over period of the study, some small changes were observed in the algal species composition among the treatments. A number of the freshwater green algae taxa initially present declined over time under higher salinity levels. However, the predominant blue green algae (Aphanothece sp.) remained unchanged.

It is possible that more distinctive differences might become more apparent over a greater period of time among the tested salinity levels. However, many species of blue green algae are known to be highly resistant to changes in salinity (Werner et al., 2008, Liu 2006, Dube et al. 2010, Mur et al. 1999, Tonk et al. 2007). It is recommended that if introducing higher salinity water is viewed as a potential management option for the Sunshine Lake/Sunrise Waterway system, then at some future point a similar bench test should be run over a much longer interval in order to test the efficacy of such an option.

6.6. Stormwater alum injection Given the virtual lack of available vacant lands for wet detention pond construction and/or expansion, and the potentially very high cost of purchasing and converting existing land uses for this purpose, the use of enhanced treatment systems such as alum injection represents a far more cost-effective approach per unit land area. Alum treatment systems are capable of achieving substantially greater treatment efficiencies than wet detention ponds, on the order of 40% removal for TN and 90% removal for TP and TSS (ERD, 1994). Alum injection with off-line floc settling basins is the approach most commonly applied. This approach is typically preferred by regulatory agencies in that the floc build-up is confined to isolated ponds or basins which can be periodically maintenance dredged to restore the settling volume capacity. In addition, the potentially toxic effects of alum floc build-up can be isolated to these smaller man-made ponds. Although the alum injection infrastructure requires very little land area (i.e., typically less than 0.25 acres), additional land area on the order of a few acres is typically required for floc settling ponds.

A less land-intensive, and thus more cost effective, alternative to this approach is alum injection with in-lake floc settling. While this alternative eliminates the need for additional land area for floc settling ponds, floc build-up in the lake and subsequent resuspension may contribute to future water quality problems. In addition, the potential toxicity of alum floc to benthic invertebrates has also been raised as a concern (WAR, 1999). However, these problems could at least be partially mitigated by the dredging of deeper floc settling basins in the lake bottom at the outfall point for each alum injection facility. The creation of in-lake settling basins would at least partially isolate the floc build-up into a smaller bottom area, and would allow removal of floc material via periodic maintenance dredging. An EPA review of alum injection as a BMP indicates that the estimated cost for the construction for an alum treatment system is $135,000 to $400,000 (EPA, 2014). Additional annual operation and maintenance costs of $6,500 to $25,000 would be required.



6.7. Evaluation of the sanitary sewer Charlotte County Utilities provided the Atkins team with videos of the gravity sewer lines adjacent to the Sunshine Lake/Sunrise Waterway system (Figure 26). Included with the videos were reports of TV sewer line segments and reports for the lift station located at the intersection of Indiana Avenue and Elkcam Blvd.

Atkins reviewed video covering over 11,000 feet of gravity sewer lines in the vicinity of Sunshine Lake/Sunrise Waterway system. The sewer lines located within the immediate vicinity, within 400 feet, of the Sunshine Lake/Sunrise Waterway system showed no major faults. The observed conditions are typical for gravity sewer mains evaluated throughout the west coast of Florida. Several lines had minor issues (debris, grease, cracks, mineral deposits, etc.), but did not exhibit traits of major defects commonly seen in gravity sewer lines (holes, large joint offsets, pipe collapse, etc.).

Charlotte County has already lined over 3,700 feet of pipe adjacent to Sunshine Lake/Sunrise Waterway system which most likely repaired the more serious issues in the sewer mains. The pipe lining has a life span of 50 years, and pipe lining eliminates infiltration and exfiltration within the sewer mains. The following table shows the gravity sewer lines that have recently been lined and are in close proximity to Sunshine Lake/Sunrise Waterway system (Figure 26; Table 23).

Figure 26. Gravity sewer lines recently lined by Charlotte County.



Table 23. Gravity sewer lines in close proximity to Sunshine Lake/Sunrise Waterway system which have recently been lined.

Starting

Manhole

Ending Manhole Street

2 143 Elkcam Blvd

4 3 Elkcam Blvd

60 61 Gladis Ave

61 62 Gladis Ave

82 4 Between Ionia and McGuire Ave

109 110 Gertrude Ave

145 144 Between Indiana and Gertrude Ave

166 167 Between Elkcam Blvd and Warne St




Not all pipes adjacent to Sunshine Lake/Sunrise Waterway system were inspected. The Atkins team did not receive videos or data for the line segments denoted in Table 24.

Table 24. Sanitary sewer line segments that were not reviewed by Atkins.

Starting

Manhole

Ending Manhole

Street

104 99 Aaron St

99 96 Aaron St

96 84 Aaron St

84 78 Aaron St

95 94 Coulton Ave

94 93 Coulton Ave

82 83 Between Ionia and McGuire Ave

The gravity sewer mains surrounding Sunshine Lake have minimal defects, and are in good condition. Clay piping generally has a 50 to 60 year life span before it starts deteriorating. Even though these pipes are thought to have been implemented in the late 50’s or early 60’s, they are showing very little issues for their age, especially when comparing them to similar systems that are close in age. The defects that were observed are common for clay piping that was implemented more than 60 years ago, but no defects that were observed were considered serious.

If Charlotte County Utilities decides to continue lining gravity sewer lines around Sunshine Lake/Sunrise Waterway, it is estimated that pipe lining costs will be approximately $25 to $35 per linear foot. A list of the lines with the most significant issues, and are in close proximity to Sunshine Lake/Sunrise Waterway that could be considered for lining are presented in Table 25.



Table 25. Sewer gravity lines with the most significant issues to be considered for future lining.

Starting Manhole Ending Manhole Street

78 69 Aaron St

68 79 Gifford St

79 83 Gifford St

98 97 McGuire Ave

69 70 Hepner Ave

67 68 Between Bersell Ave and Gephart Ave

2 3 Elkcam Blvd

In addition to reviewing the videos of the gravity sewer lines, Atkins reviewed the May 4th, 2012 smoke test

conducted by USSI of the gravity sewer lines in the community surrounding Sunshine Lake. A total of 64 incidents were reported, 35 on private property and 29 on public utility easements.

Out of the 35 incidents that occurred on private property, six were from cracked laterals, 17 were from cracked or missing cleanout lids, and 12 were reports of smoking entering houses. Cracked cleanout lids and smoke entering houses is not an indication of exfiltration, but rather home owners neglect of sanitary systems. Cracked laterals may cause some exfiltration, and should be replaced.

All 29 incidents that occurred in public easements were from smoke seeping out of manhole lids. Half of the incidents were caused from cracked manholes lids and the other half were cause from open pick holes. These issues can cause storm water to infiltrate the sanitary sewer system, but does not indicate that sewage is escaping the system. If there is a surcharge of sewage, it can escape through these cracks or open pick holes, but Atkins did not receive any reports of this happening.

Atkins also reviewed Preventive Maintenance and Corrective Maintenance reports provided by Charlotte County Utilities for Lift Station #11 located at the intersection of Indiana Avenue and Elkcam Boulevard. The reports covered the last 5 years. The Preventive Maintenance Reports indicates the lift station received quarterly inspections (every 3 months) to check the pump operations, valves, wet well conditions, etc. No significant issues were noted in the reports for the lift station.

The Corrective Maintenance Reports identified issues reported by local residents or by alarm notifications from the SCADA system. The reported issues were typical for lift station operations and varied from noise and odor complaints to pump malfunctions or electrical shorts that required pump replacements. Some items required cleaning pump impellers that became tangled within the impellers and clogged the pumps. There are no mentions in the reports of any sewage overflows due to pump outages. Over the 5 year period there were approximately 10 incidences where pump operations could have been impacted. If high level alarms were received and quick responses made to the issues, sewage overflows would have been avoided.

6.8. Programs to address stormwater as a source of bacteria Typical fecal coliform bacteria concentrations for untreated stormwater runoff range from 10,000 to 100,000 MPN/100mL (Metcalf & Eddy 2003). Thus, it is important to consider stormwater as a potential and highly probable conveyance system for a variety of more specific sources of bacterial contamination. Although the first priority should always focus on the elimination of the sources contributing pollution to stormwater conveyance systems, stormwater must also be considered as a source unto itself in order to manage it more effectively.

Management actions to provide additional stormwater treatment reduce the sediment, oil and grease, and nutrient and bacteria loadings discharged into an affected waterbody. When focusing efforts on stormwater treatment, it is important to realize that the reduction of sediment loads to surface waters is critical because such



particles frequently adsorb bacterial colonies, thus facilitating their survival, growth, and transportation from one area to another (Gerba & McLeod 1976, LaLiberte & Grimes 1982, Marino & Gannon 1991, Davies et al. 1995).

Stormwater-related management actions that should be considered include:

Additional redevelopment and stormwater retrofit (e.g., disconnection of directly connected impervious areas);

Use of UV light disinfection or ozone treatment for small systems;

Use of individual product-line developments such as anti-microbial filters for stormwater conveyance systems;

Increased sediment control;

Implementation of pet waste control practices; and

Application of non-structural BMPs to the affected areas.

6.9. Available funding sources

Southwest Florida Water Management District’s Cooperative Funding Initiative The District’s Cooperative Funding Initiative (CFI) covers up to one half of the cost of projects (usually developed in association with local governments) that address the need for sustainable water resources, enhance water quality, provide flood protection, and promote conservation and the restoration of natural systems. http://www.swfwmd.state.fl.us/business/coopfunding/

Florida Department of Environmental Protection’s Nonpoint Source Management Section The Nonpoint Source Management Section grants money it receives from the EPA through the Federal Clean Water Act to fund projects that will help to reduce nonpoint sources of pollution within the state’s SWIM watersheds and national Estuary Program waters. All projects should include a non-federal match of at least 40 percent. Projects include demonstration and evaluation of Best Management Practices (BMPs), nonpoint pollution reduction in priority watersheds, groundwater protection from nonpoint sources, public education programs on nonpoint source management, etc. http://www.dep.state.fl.us/water/nonpoint/319h.htm

http://www.swfwmd.state.fl.us/business/coopfunding/

http://www.dep.state.fl.us/water/nonpoint/319h.htm



7. Conclusions and Recommendations

Early work by Atkins in their preliminary diagnostic study, pointed out the need for additional technical assessments, most importantly a more detailed assessment of the source(s) of the excessive nutrient loads that seem to have allowed the algal bloom to develop. A more detailed assessment of the potential influence of both surface inflows and groundwater seepage was the first step for the production of a detailed management plan for Sunshine Lake and the Sunrise Waterway. A six-month monitoring period was performed to collect data on stormwater runoff and groundwater inflows into the Sunshine Lake/Sunrise Waterway. The results of this effort were analyzed and interpreted so that appropriate actions can be undertaken to minimize the return of the noxious algal blooms that existed in the lake prior to their removal. A summary of the data interpretation is present below:

Nutrient concentrations within Sunshine Lake and the Sunrise Waterway are lower than nutrient concentrations in stormwater runoff and groundwater seepage.

o These results could suggest that the lake’s assimilative capacity for nutrient loading is not currently overwhelmed

o Conversely, these results could indicated that nutrient loads into the lake and waterway are taken up by “nutrient sinks” that are not in the water column (i.e. the algae biomass)

Nutrient concentrations in groundwater inflows and the surficial aquifer are higher than those expected from an undeveloped watershed, they are mostly in-line with expected values from urbanized watersheds

o The exception is that levels of phosphorous in the surficial aquifer are mostly highly elevated

Concentrations of nitrogen in stormwater runoff are higher than those expected from an undeveloped watershed, but they are not substantially higher than expected values from urbanized watersheds

In contrast to nitrogen, concentrations of phosphorus in stormwater runoff are substantially higher than expected values from urbanized watersheds in other parts of Florida

Elevated levels of phosphorus in the surficial aquifer and in stormwater runoff may reflect the previously documented phosphorus-rich surface geology in the surrounding watershed

The highest concentrations of phosphorus are in stormwater runoff, however, groundwater inputs are the most important loading source to the lake and waterway for nitrogen

Based on the nutrient budget, the system appears to be nitrogen-limited, likely in part, to the phosphorus-rich geology.

Concentrations of fecal coliform bacteria have been recorded at very high concentrations in stormwater runoff. However, additional tests do not indicate that humans are the primary source of the very high levels of fecal coliform bacteria in stormwater runoff

The results summarized above indicate that the nutrient loads required to account for the massive algal bloom in Sunshine Lake and Sunrise Waterway may be linked to an influx of both phosphorus and nitrogen. The algal mat that was recently removed by dredging was comprised of various species of cyanobacteria, some of which have been shown to be able to “fix” nitrogen from the atmosphere. However, there is no direct evidence that the dominant cyanobacteria within the lake actually fixing atmospheric nitrogen.

With a lake that is “primed” by high natural inputs of phosphorus, the high concentrations of nitrogen in the groundwater input could be the key to stimulating the growth of the algae bloom in Sunshine Lake and the Sunrise Waterway. However, the lack of similarly and consistently elevated levels of nitrogen in stormwater runoff (compared to phosphorus) suggests that sewage and/or fertilizer are not likely the source(s) of high levels of nutrients. Instead, it is likely that the high levels of phosphorus in stormwater runoff are associated with the geologic formation referred to as the Peace River Formation of the Hawthorn Group. This geological formation, which extends into Charlotte County just east of Port Charlotte (Figure 9), is characterized by its elevated phosphorus content. Of particular note, the report titled “UF/IFAS Nutrient Management Series: Computational Tools for Field Implementation of the Florida Phosphorus Index - Charlotte County Florida” stated that the



phosphorus-rich soils immediately adjacent to Sunshine Lake and the Sunrise Waterway have a “VERY HIGH potential…for an adverse impact on surface waters.”

The high levels of fecal coliform bacteria found in stormwater runoff could be due to a number of sources, such as: 1) human sewage, 2) wildlife, 3) pet wastes, 4) soils, and 5) rotting vegetation. While it is tempting to conclude that high levels of fecal coliform bacteria are indicative of humans as a source, prior studies in the City of Miami, Collier County and in Hawaii have shown that soils and waterbodies in humid subtropical environments contain naturally-occurring bacteria that test positive as “fecal coliform” bacteria. While a more detailed assessment of sources (described above) did not find evidence of sewage as a primary source of the bacteria, the caveat that “an absence of evidence does not constitute evidence of absence” should be kept in mind. The fact that the samples analyzed did not produce evidence of humans as a significant proportion of the bacteria recorded does not mean that contamination by sewage is never a major problem.

Based on the monitoring effort, it appears that the algal bloom in Sunshine Lake and the Sunrise Waterway may have been caused by two phenomena. First, the waterways experience excessive loads of phosphorus from stormwater runoff, mostly. However, these high levels of phosphorus do not appear to be due to human impacts from either sewage or fertilizer, as levels of nitrogen are not similarly elevated (for the most part) and there is no evidence that high bacteria levels are related to sewage. Instead, high levels of phosphorus appear likely – at this time – to be due to runoff from soils with high natural phosphorus contents. The high nitrogen content of the previously dredged algal mat could be brought about through in-situ nitrogen fixation by cyanobacteria, a process that has been previously documented in other hypereutrophic lakes, or nitrogen loads could be due to a one-time event, such as the passage of Hurricane Charley, or nitrogen from groundwater could be a significant source of nutrient loading.

There are several lake management approaches and techniques that can be used to address water quality issues and concerns in the Sunshine Lake/Sunrise Waterway. Even if external loads to lakes are reduced or eliminated, internal nutrient loads should be managed. Generally, the types of projects that have had the greatest success, in terms of restoration of water quality, have been those that focused on removing point sources of nutrient pollution, combined with actions to reduce the impacts of past nutrient loading events. Simply treating the symptoms (killing the algae) has generally proven to be both difficult and ineffective without continued high levels of ongoing treatment. The water quality management plan recommends implementing the following series of projects in sequence.

Monitoring program

Floating treatment wetlands

Artificial circulation

Lake level augmentation

If after the implementation of the above mentioned projects is not successful in reducing/eliminating the re-occurrence of the algal mat, in-line alum injection of stormwater should be considered.



8. Literature Cited

Adamski, J. and L. Knowles. 2001. Ground-Water Quality of the Surficial Aquifer System and the Upper Floridan Aquifer, Ocala National Forest and Lake County, Florida, 1990-99. USGS Water Resources Investigation Report, 01-4008. 56 pp.

Atkins. 2012. Sunshine Lake / Sunrise Waterway Study. Final Report to Charlotte County. 33 pp.

Cooke, G.D., E.B. Welch, S.A. Peterson, and P.R. Newroth. 1993. Chapter 16: Artificial Circulation In: Restoration and Management of Lakes and Reservoirs: Second Editions. Lewis Publishers: Boca Raton.

Davies, C.M., Long, J.A., Donald, M., Ashbolt, N.J. 1995. Survival of fecal microorganisms in marine and freshwater sediments. Applied and Environmental Microbiology 61:1888-1896

DeBusk, T.A., R.Baird, D. Haselow, and T. Goffner. 2005. Evaluation of a floating wetland for improving water quality in an urban lake. Proceedings of the Eighth Biennial Stormwater Research and Watershed Management Conference April 27-28. Pages 175-184.

Dixon, L.K., Heyl, M.G., and Murray, S.. 1998. Interpretation of bulk atmospheric deposition and stormwater quality data in the Tampa Bay Region. Tampa Bay Regional Planning Council. Tampa Bay Estuary Program Report no 04-98. Mote Marine Laboratory Technical Report no 602. 70 p. and appendices. Available from: Mote Marine Laboratory Library.

Dube, A., G. Jayaraman, and R. Rani. 2010. Modelling the effects of variable salinity on the temporal distribution

of plankton in shallow coastal lagoons. Journal of Hydro-environmental Research 4:199-209.

ERD. 2010. Winter Haven Chain of Lakes Sediment Removal Feasibility Study. Final Report to the Southwest

Florida Water Management District and the City of Winter Haven. EPA. 2014a. http://water.epa.gov/polwaste/npdes/swbmp/Alum-Injection.cfm EPA. 2014. National Stormwater Calculator User’s Guide. Version 1.1. USEPA Office of Research and

Development, Cincinnati, OH Gerba, C.P., McLeod, J.S.1976. Effect of sediments of the survival of Escherichia coli in marine waters. Applied

and Environmental Microbiology 32:114-120

Harper, H. and D. Baker. 2007. Evaluation of Current Stormwater Design Criteria within the State of Florida. Final Report to FDEP. 327 pp.

Headley, T.R. and C.C. Tanner. 2006. Application of floating wetlands for enhanced stormwater treatment: A review. Prepared for Auckland Regional Council. NIWA Client Report: HAM2006-123.

Henderson, W. 1984. Soil Survey of Charlotte County, Florida. USDA/NRCS in cooperation with University of Florida Institute of Food and Agricultural Sciences, Agricultural Experiment Stations, Soil and Water Science Department and the Florida Department of Agriculture and Consumer Services.

Heyl, M.G. 1992. Point and non-point source pollutant loading assessment. Pp. 12.1-12.9. In: P. Roat, C. Ciccolella, H. Smith, and D. Tomasko (eds.). Sarasota Bay Framework for Action. Sarasota Bay National Estuary Program, Sarasota, FL.

http://water.epa.gov/polwaste/npdes/swbmp/Alum-Injection.cfm



Hubbard, R.K. 2010. Chapter 9: Floating vegetated mats for improving surface water quality. In Emerging Environmental Technologies (editors) V. Shah. Pp. 211-244

Hubbard, R.K., G.J. Gascho, and G.L. Newton, G.L. 2004. Use of floating vegetation to remove nutrients from swine lagoon wastewater. Trans. ASAE 47(6): 1963–1972.

Hurt, G., Mylavarapu, R., and S. Boetger. 2013. UF/IFAS Nutrient Management Series: Computational

Kadlec, R.H. and R.L. Knight. 1996. Treatment Wetlands. Lewis Publishers. Boca Raton.

Kadlec, R.H. and S.D. Wallace. 2009. Treatment Wetlands. CRC Press. Boca Raton.

Kolasa, K. and W. Kang. 2005. Aeration of subtropical hypertrophic lake- a band-aid approach that’s working. 69th Annual Meeting of the Florida Academy of Sciences. University of South Florida, Tampa, Fl. March 2005.

LaLiberte, P. and Grimes, D.J. 1982. Survival of Escherichia coli in lake bottom sediment. Applied and Environmental Microbiology 43:623-628

Liu, Y. 2006. Effects of Salinity on the Growth and Toxin Production of a Harmful Algal Species, Microcystis aeruginos. J. U. S. SJMP 1:91-111.

Marino, R., and Gannon, J. 1991. Survival of fecal coliforms and fecal streptococci in storm drain sediment. Water Research 25:1089-1098

Metcalf & Eddy, I. 2003. Wastewater Engineering, Treatment and Reuse, Vol. The McGraw-Hill Companies, Inc., New York, NY. Tools for Field Implementation of the Florida Phosphorus Index - Charlotte County Florida. Circular 1263 - Soil and Water Science Department, UF/IFAS Extension. 24 pp.

Mur, L., O. Skulberg, and H. Utkilen. 1999. Toxic Cyanobacteria in Water: A guide to their health consequences, monitoring and management. Ed. I. Chorus and J. Bartram. Chapter 2.

Pastorak, R.A., M.W. Lorenzen, and T.C.Ginn. 1982. Environmental aspects of artificial aeration and oxygenation of reservoirs: a review of theory, techniques, and experiences., Technical Report. No. E-82-3. U.S. Army Corps of Engineers.

Pastorak, R.A., T.C. Gunn, and M.W. Lorenzen. 1981. Evaluation of Aeration/Circulation as a Lake Restoration Technique. 600/3-81-014 U.S.EPA.

Pitt, R. Urban Bacteria Sources and Control in the Lower Rideau River Watershed, Ottawa, Ontario, Ontario Ministry of the Environment, ISBN 0-7743-8487-5. 165 pgs. 1983.

PBS&J. 2009. Winter Haven Chain of Lakes TMDL Analysis Task Assignment 1- Evaluation of Groundwater Seepage and Lake Bottom Sediments. Final Report to FDEP. 84 pp.

PBS&J . 2010a. Winter Haven Chain of Lakes Water Quality Management Plan. Final Report to the City of Winter Haven, Tampa, FL.

Scott, T., Campbell, K., Rupert, F., Arthur, J., Green, R., Means, G., Missimer, T., Lloyd, J., Yon, J., and J. Duncan. 2001. Geological Map of the State of Florida.

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Stumm, M., and J.O. Leckie. 1971. Phosphate exchange with sediments: its role in the productivity of surface waters. Proceedings of the 5th International Conference on Water Polution. Res. III-26/1-16. London.

Tomasko, D.A., Anastasiou, C., and C. Kovach. 2006. Dissolved oxygen dynamics in Charlotte Harbor and its contributing watershed, in response to Hurricanes Charley, Frances, and Jeanne – Impacts and Recovery. Estuaries and Coasts. 29(6A):932-938.

Tomasko, D.A., Hyfield-Keenan, E.C., DeBrabandere, L.C., Montoya, J.P., and T.K. Frazer. 2009. Experimental studies on the effects of nutrient loading and sediment removal on water quality in Lake Hancock. Florida Scientist. 4: 346-366.

Tonk, L. 2007. Impact of environmental factors on toxic and bioactive peptide production by harmful cyanobacteria. Gildeprint B.V., Enschede, The Netherlands.

University of Florida. 2003. A Beginner’s Guide to Water Management — Bacteria. Information Circular 106. 48 pp.

Werner, V. C. Sant’Anna, and M. Azevedo. 2008. Cyanoaggregation brasiliense gen. Et sp. Nov.. a new chroococcal Cyanobacteria from Southern Brazil. Revista Brasil. Bot. 31(3):491-497.

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