Agenda 12/07/2017 PELICAN BAY SERVICES DIVISION
Municipal Service Taxing and Benefit Unit
NOTICE OF PUBLIC MEETING DECEMBER 7, 2017
THE CLAM BAY COMMITTEE OF THE PELICAN BAY SERVICES DIVISION WILL
MEET AT 1:30 PM ON THURSDAY, DECEMBER 7 AT THE PELICAN BAY
SERVICES DIVISION, 3RD FLOOR OF THE SUNTRUST BUILDING, SUITE 302,
LOCATED AT 801 LAUREL OAK DRIVE, NAPLES, FLORIDA 34108.
AGENDA
1. Roll call
2. Agenda approval
3. Approval of 10/03/17 meeting minutes
4. Audience comments
5. Clam Bay
a. Monitoring Irma recovery
b. Removing debris from hand-dug channels and waterways
C. Other debris removal
d. Die-off area assessment
e. Other
6. Clam Pass
a. Update on current conditions
b. November tidal ratio report
7. Water Quality
a. Copper results
b. Third quarter report on TP and TN
C. WIN data entry
d. Water sample collection
e. Discharge from Mystique construction project
8. Annual reports — due December 15, 2017
a. Clam Bay monitoring
b. Water Quality — due 30 days after October WQ results reported
C. Bathymetric and tidal monitoring
9. Next meeting: January 4
10. Adjournment
ANY PERSON WISHING TO SPEAK ON AN AGENDA ITEM WILL RECEIVE UP TO THREE (3) MINUTES PER ITEM TO
ADDRESS THE BOARD. THE BOARD WILL SOLICIT PUBLIC COMMENTS ON SUBJECTS NOT ON THIS AGENDA AND
ANY PERSON WISHING TO SPEAK WILL RECEIVE UP TO THREE (3) MINUTES. THE BOARD ENCOURAGES YOU TO
SUBMIT YOUR COMMENTS IN WRITING IN ADVANCE OF THE MEETING. ANY PERSON WHO DECIDES TO APPEAL A
DECISION OF THIS BOARD WILL NEED A RECORD OF THE PROCEEDING PERTAINING THERETO,AND THEREFORE
MAY NEED TO ENSURE THAT A VERBATIM RECORD IS MADE, WHICH INCLUDES THE TESTIMONY AND EVIDENCE
UPON WHICH THE APPEAL IS TO BE BASED. IF YOU ARE A PERSON WITH A DISABILITY WHO NEEDS AN
ACCOMMODATION IN ORDER TO PARTICIPATE IN THIS MEETING YOU ARE ENTITLED TO THE PROVISION OF
CERTAIN ASSISTANCE. PLEASE CONTACT THE PELICAN BAY SERVICES DIVISION AT (239) 597-1749. VISIT US AT
HTTP://PELICANBAYSERVICESDIVISION.NET.
11/30/2017 3:43 PM
PELICAN BAY SERVICES DIVISION
CLAM BAY COMMITTEE MEETING
OCTOBER 3,2017
The Clam Bay Committee of the Pelican Bay Services Division met on Tuesday, October 3 at
10:00 a.m. at the SunTrust Bank Building, 801 Laurel Oak Drive, Suite 302, Naples, Florida
34108. In attendance were:
Clam Bay Committee Bohdan Hirniak (absent)
Susan O'Brien, Chairman Gary Ventress
Pelican Bay Services Division Staff Mary McCaughtry, Operations Analyst
Neil Dorrill, Administrator Lisa Jacob, Associate Project Manager
Marion Bolick, Operations Manager (absent) Barbara Shea, Recording Secretary
Also Present
Jennifer Bobka, Earth Tech Mike Shepherd, PBSD Board
Mohamed Dabees, Humiston& Moore Jeremy Sterk, Earth Tech
Tim Hall, Turrell, Hall & Associates Dave Trecker, PBSD Board
APPROVED AGENDA(AS AMENDED)
1. Roll call
2. Agenda approval
3. Approval of 06/08/17 meeting minutes
4. Audience comments
5. Clam Bay
a. Condition of mangroves
b. Water level logger data
c. Hand-dug channel maintenance
d. Other updates
6. Clam Pass
a. Update on current conditions
b. September tidal ratio report
c. Bathymetric surveys and findings
d. Dredging Clam Pass
7. Water Quality
a. Sediment report
b. Copper results
c. 2nd quarter report on TP and TN
d. Adding water clarity to WQ parameters
e. WIN data entry
f. Water quality sampling August& September (add-on)
8. Annual reports—due December 15, 2017
a. Clam Bay monitoring
1
Pelican Bay Services Division Clam Bay Committee Meeting
October 3,2017
b. Water Quality—due 30 days after October WQ results reported
c. Bathymetric and tidal monitoring
8A. Clam Pass Park update (add-on)
9. Next meeting: January 4
10. Adjournment
ROLL CALL
Mr. Hirniak was absent and a quorum was established
AGENDA APPROVAL
Mr. Ventress motioned, Ms. O'Brien seconded to approve the agenda as amended,
with the addition of items #7f and 8A. The motion carried unanimously.
APPROVAL OF 06/08/17 MEETING MINUTES
Mr. Ventress motioned, Ms. O'Brien seconded to approve the 06/08/17 meeting
minutes as amended. The motion carried unanimously.
AUDIENCE COMMENTS
None
CLAM BAY
CONDITION OF MANGROVES
The committee reviewed before (August 22) and after (September 19)photos of the Clam
Bay mangroves, provided by Humiston and Moore, to assess the damage from Hurricane Irma.
October 2 aerial photos, taken by Earth Tech, were also reviewed. Mr. Hall commented that
"replacing mangroves" is FEMA reimbursable.
WATER LEVEL LOGGER DATA
Mr. Sterk provided water level logger data through the prior week, and commented that
the Clam Bay system has easily handled various summer rain events, and drainage has improved
in comparison to last summer. He reported that logger #3 is "down" as a result of the hurricane
and will be reinstalled. Ms. Jacob reported that canoe marker #12 has been uprooted and needs
to be reinstalled.
HAND-DUG CHANNEL MAINTENANCE
Mr. Sterk commented on comparison photos (March & June) of Clam Bay hand-dug
channels; the next inspection will be in early November. He commented that additional funds
may be necessary for additional channel clean-up resulting from Hurricane Irma. Near-term
attention is needed to clean out debris and fallen trees from these channels. Mr. Hall commented
that only mangrove debris in the channels should be removed. Mr. Dorrill commented that staff
will follow up on the suggested near-term clean-up work. Ms. Bobka commented that although
the mangroves show leaf loss and stress, she has observed minimal mangrove mortality.
After committee discussion of the lack of"plots" in the Irma-impacted area, Mr. Sterk
agreed to come back to the committee with new proposed plots for monitoring the Irma-impacted
areas.
2
Pelican Bay Services Division Clam Bay Committee Meeting
October 3, 2017
OTHER UPDATES
Mr. Sterk reported on his pre-hurricane observations of considerably reduced acreage of
seagrass in the southern end of Clam Bay, most likely a result of poor pre-dredge conditions.
CLAM PASS
Dr. Dabees provided a post-hurricane update on the conditions in Clam Pass. He noted
increased sand deposits in Sections B & C resulting from the storm surge. He suggested a survey
of Sections B & C to document the storm's impact. He reported that 9000 yards of sand was
removed from the inlet during the summer dredging project; 2944 yards of sand was deposited
on the Pelican Bay beach.
Ms. O'Brien commented that we are due to obtain a bathymetric survey to fulfill the
Clam Bay Management Plan's requirement of an annual survey. Mr. Dorrill commented that the
cost of the survey, including analysis, is approximately $6,500.
Ms. Jacob suggested that the PBSD Board considers including the cost of annual
maintenance dredging in future PBSD budgets. Dr. Dabees suggested that the PBSD budget
include "dredging reserve funds" to address any future dredging emergencies. Dr. Trecker
commented that per the Clam Bay Management Plan, certain conditions must exist in order to
start the planning process of a Clam Pass dredging event. He suggested that the PBSD Board
consider internal funding for"maintenance dredging."
WATER QUALITY
SEDIMENT REPORT
Mr. Hall commented on his April 2017 Clam Bay Sediment & Surface Water Copper
Analysis Report included in the agenda packet, highlighting high copper levels in the sediment in
the north end of Clam Bay. Dr. Trecker provided a document (which was added to the record)
entitled, "Sediment measurements in Clam Bay" which provided his conclusions on the THA
report including (1) there is an enormous amount of copper in the sediment, (2) the ratios of
water/sediment copper are very similar in the three bays, and (3) the copper in both the sediment
and water column is highest in Upper Clam Bay and lowest in Outer Clam Bay. He commented
that one cannot assume that improved "flushing" in the Clam Bay system would improve Clam
Bay copper levels.
Dr. Trecker also provided documents (which were added to the record) on phosphorus
data in Clam Bay and Pelican Bay lakes during 2016 & 2017. He suggested that the high levels
of phosphorus in the Vizcaya lake and Laurel Oaks lake may be contributing to the high
phosphorus levels in Upper Clam Bay.
COPPER RESULTS
Ms. O'Brien commented that copper levels in Clam Bay remain "about the same" as
reported in the nine site copper table, updated through July.
SECOND QUARTER REPORT ON TP AND TN
Mr. Hall reviewed the 2nd quarter Tomasko report on TP and TN (included in the agenda
packet), highlighting the problematic phosphorus levels in Clam Bay. The 3rd quarter report
should be available shortly.
ADDING WATER CLARITY TO WQ PARAMETERS
3
Pelican Bay Services Division Clam Bay Committee Meeting
October 3,2017
Mr. Hall recommended adding water clarity to WQ parameters; water clarity data may
show that Clam Bay nutrient levels are sourced from the sediment. He suggested using a Secchi
disk to obtain water clarity data. Staff will follow up on the status of Secchi disk training by
selected PBSD personnel.
WIN DATA ENTRY
Mr. Hall reported that the County is in the process of changing their lab management
system, and currently is not producing "adapt reports"which are used for input into WIN.
WATER QUALITY SAMPLING AUGUST & SEPTEMBER(ADD-ON)
Mr. Hall reported that (1) August samples were not adequately preserved at the County
Lab as a result of a reported loss of refrigeration in the lab; Mr. Hall recommended discarding
these samples, (2) August copper results will be provided by the County Lab, (3) as a result of
Hurricane Irma, no samples were extracted in September. Mr. Dorrill and Mr. Hall agreed that
THA would obtain October samples for water quality testing.
ANNUAL REPORTS
Committee members, consultants, and staff reviewed due dates of annual reports
including, (1) the Clam Bay monitoring report and the bathymetric and tidal monitoring report
are due on Dec. 15, and (2) the water quality report is due 30 days after the October WQ results
are reported.
CLAM PASS PARK UPDATE (ADD-ON)
Ms. Jacob reported that the Clam Pass Park boardwalk was damaged by Hurricane Irma
and is closed indefinitely (to trams and pedestrians). The County has hired an engineer to
evaluate the boardwalk for safety purposes.
NEXT MEETING:
By consensus, the committee agreed that the next meeting of the committee would be
held on December 7 at 1:30 p.m.
ADJOURNMENT
The meeting was adjourned at 11:55 a.m.
Susan O'Brien, Chairman
Minutes approved [ ] as presented OR [ 1 as amended ON [ ] date
4
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Agenda Item#6b-1
Page 1 of 1
Clam Pass tide Data NM.'2011 I NAW
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Agenda Item#7a
Page 1 of 1
Clam Bay Copper ug/L
Collection Date CBI. CB2 CB3 CB4 CB5 CB6 CB7 CB8 CB9 Report Date
6/22/2016 0.862 0.700 0.700 0.700 1.640 2.100 0.700 3.520 1.510 9/8/2016
7/20/2016 0.924 5.330 5.110 5.660 2.470 3.960 4.950 5.710 10.500 9/12/2016
7/20/2016 0.924 6.160 4.700 1.690 2.470 1.830 1.980 1.870 8.360 9/21/2016
8/25/2016 2.000 1.850 1.680 1.470 1.240 1.520 2.250 1.280 8.060 10/4/2016
9/20/2016 1.690 2.280 1.280 1.760 0.751 0.700 0.700 1.030 0.700 11/22/2016
10/12/2016 2.760 2.200 2.130 1.190 2.900 1.860 1.060 0.954 1.310 12/7/2016
11/9/2016 2.340 3.390 2.300 2.250 1.630 1.500 1.180 2.030 1.300 1/16/2017
12/6/2016 2.330 2.930 5.100 2.450 2.390 1.780 1.270 1.880 1.720 3/14/2017
1/19/2017 2.570 3.560 2.110 1.990 0.818 0.800 0.961 1.110 2.020 4/4/2017
2/23/2017 2.510 3.350 1.600 1.120 0.851 0.848 1.500 2.570 2.600 4/24/2017
3/21/2017 7.970 4.080 1.710 1.120 0.894 0.846 1.080 1.090 0.957 6/1/2017
4/18/2017 6.480 8.160 1.620 1.240 0.800 0.956 1.280 1.010 1.100 6/14/2017
5/24/2017 2.840 4.060 4.990 0.800 0.800 0.959 0.800 0.920 0.946 7/6/2017
6/21/2017 3.840 4.240 3.850 0.906 1.200 1.140 1.260 1.110 0.760 8/8/2017
7/13/2017 4.700 2.950 3.800 4.080 2.500 2.440 2.370 2.380 2.210 8/29/2017
8/14/2017 4.290 3.810 3.220 2.650 1.400 1.220 1.470 1.020 0.700 10/10/2017
Agenda Item#7b
4350 West Cypress Street Page d e�
E L 1? Suite 950 1.vf#
Tampa,FL 33607
813.207.7200 p cr
813.207.7201`,2x
memorandum
date October 17, 2017
to Tim Hall, Turrell, Hall and Associates, Inc.
from David Tomasko, Ph.D.
Emily Keenan, M.S.
subject Quarter 3: Clam Bay NNC SSAC evaluation
Background
The United States Environmental Protection Agency (EPA) and Florida Department of
Environmental Protection Agency (FDEP) adopted site specific alternative nutrient criteria
(SSAC) for Clam Bay, as listed in Florida Administrative Code (FAC) 62-302.531. The SSAC
were derived based upon a nutrient: salinity relationship from the Estero Bay Wetlands, a
reference waterbody for water quality, as established by FDEP in prior TMDLs. The SSAC for
Clam Bay is considered in the context of salinity due to the variability in nutrient concentrations
that can be due to changes in freshwater inflow, rather than changes in nutrient concentrations
alone. Therefore, the appropriate management response associated with any impairment
determination is based upon the magnitude and duration of any exceedances.
Based on prior work that showed that phytoplankton growth in Clam Bay was likely stimulated
by both Total Nitrogen (TN) and Total Phosphorous (TP), both TN and TP are used to
determine the degree of nutrient enrichment of Clam Bay's waters. As outlined in FAC 62-
302.531, water quality status is determined on an annual basis, preferably within a calendar
year. Within a calendar year, each individual TN and TP value collected within the waterbody
is compared to the nutrient: conductivity 90th percentile prediction limit (Figure 1), and an
annual percent exceedance is calculated to determine the magnitude of exceedances per
year. To be consistent with the method currently implemented by FDEP to identify impaired
water bodies, if 13 percent or more of the TN or TP values in a calendar year exceed the 90th
percentile prediction limit (after being normalized for conductivity) the duration of exceedance
would then be determined. Based on the duration of exceedance (one year or greater than one
year), the outcome designation is assigned. If fewer than 13 percent of the values exceed the
90th percent prediction limit, then the outcome is "0". If the magnitude (i.e., 13 percent) and
duration (i.e., less than 1 year) of the exceedances are deemed small, the outcome is "1". If
the magnitude or duration of the exceedances is large, then the outcome is "2". If both the
magnitude and duration of the exceedances are large, then the outcome is "3". The
Agenda Item#7b
Page2of7
management response for Clam Bay would be determined based on the outcomes assigned to
both the TN and TP evaluations for the magnitude and duration of exceedance (Figure 2).
The water quality status of Clam Bay would be assigned a green, yellow, or red designation
annually based on the magnitude and duration of exceedances of the 90th percent prediction
limit. The color designation is then used to determine what level(s) of management actions are
appropriate.
Annual management response actions are based on the response to nutrient concentrations of
phytoplankton and dissolved oxygen (DO) as well as impacts on water clarity (Figure 3). If the
outcome of the TN and TP evaluation is green, then no management actions are required.
However, if the outcomes are yellow or red then further evaluation of the effect of elevated
nutrient concentrations on both phytoplankton biomass and DO concentrations need to be
reviewed. If there is no relationship between nutrients and chlorophyll-a or DO, then no
management actions are required. If there is a signification relationship, then the impact of
chlorophyll-a on the water clarity (Secchi disk depth) would be evaluated. If there is no
relationship between chlorophyll-a and water clarity, then no management actions are
required. If there is a significant relationship between chlorophyll-a concentrations and water
clarity, an outcome designation of"yellow" (indicative of small magnitude or duration of
exceedances) identifies that management actions should be taken to identify the potential
causes and responses for the elevated nutrient levels. It the outcome designation is "red"
(indicative of a large magnitude or duration of exceedances), management actions should be
taken to implement recommended response tactics to reduce nutrient concentrations. In this
manner, the "health" of Clam Bay is to be assessed annually.
Figure 1. Clam Bay water quality flow chart.
D >13%of all TN&forTP
values from a calendar year
exceed the 90%prediction limit
No j from the reference WB 10?
Outcome 4 Yes
?13;0Magnitude of >_15°0
exceedance
Duration of Duration of
exceedance -
I exceedance
1 year >1 year 1 year i >1 year
Outcomes OutcomeI Outcome 2 Outcome3
2
Agenda Item#7b
Page 3 of 7
Figure 2. Management response matrix using outcomes from both TN and TP
evaluation.
Total Phosphorus
Total Nitrogen Outcome 0 Outcome 1 Outcome 2 Outcome 3
Outcome 0
Outcome 1
Outcome 2
Outcome 3
Figure 3. Management response actions in response to various outcomes.
Green Yellow or Red
Response
III evaluation
Evaluate phytoplankton f significant
dissolved oxygen (p<o.OS)
Not significant response to nutrient
(ro.osi concentrations
Evaluate water clarity
ta:r arit _..__. response to chlorophyll-a
{p-4.o5)
Significant ip<4,05)
Small difference or
short duration
Identify potential causes
and implement Identify potential
recommended response Large difference or causes and
long dui ation responses
3
Agenda Item#7b
Page 4 of 7
Data Analysis
The analysis conducted below was used to assess the water quality status of Clam Bay during
the months of May 2017 to July 2017. Since the SSAC developed for Clam Bay is to be
evaluated on an annual time step, this analysis provides insight into current water quality
conditions within the Bay, but it does not substitute for the more comprehensive annual
assessment required. Clam Bay surface water quality data were provided by Turrell, Hall and
Associates, Inc. for comparison with the FDEP adopted SSAC established for Clam Bay and
found within FAC. 62-302-532 -1-j. The NNC SSAC states the following;
"No more than 10 percent of the individual Total Phosphorus
(TP) or Total Nitrogen (TN) measurements shall exceed the
respective TP Upper Limit or TN Upper Limit."
The TP and TN upper limits are calculated using equations 1 and 2:
Equation 1: TP Upper Limit (mg/L)= e(-1.06256-0.0000328465'Conductivity(Ns))
Equation 2: TN Upper Limit (mg/L)= 2.3601 — 0.0000268325*Conductivity(PS)
The dataset was supplemented with in situ water quality data (e.g., temperature, dissolved
oxygen, pH, conductivity, and salinity) retrieved from the chain of custody forms for each
sampling event. The corresponding TN or TP Upper Limit was calculated for each Clam Bay
estuarine water quality station and sampling date in which conductivity was available using
Equations 1 and 2. TN and TP concentrations were compared to the derived upper limit
thresholds to ascertain if elevated concentrations were identified (Appendix A).
Results
Over the period analyzed in this memo (May 2017 to July 2017), there were no TN
measurement from the open waters of Clam Bay (from the 9 ambient water quality stations
sampled three times each) which exceeded the respective Upper Limits. In the prior quarter
(February, March and April of 2017) only one site exceeded TN criteria, Station 1 in Upper
Clam Bay. In contrast, 11 of the 27 TP measurements (41 percent) exceeded their respective
Upper Limits during the months of May 2017 to July 2017. In the prior quarterly report, 13 of
27 samples exceeded NNC criteria for TP.
It should be noted that laboratory detection limits can sometimes come into play when
comparing values against criteria, as detection limits sometimes are such that values have to
be "rounded up" based on minimum detection limits. Based on the results from this time
period, and if the frequency of exceedance seen here was to be maintained over the course of
a calendar year, Clam Bay would likely be determined to be impaired for TP.
The 11 TP exceedances are illustrated in Table 1. Exceedances of the TP criteria were
observed in Outer, Inner and Upper Clam Bays in May and June, but no exceedances were
found in July. In May of 2017, elevated TP concentrations were observed at all but station 9,
which is located in the canal system south of Seagate Drive. In June of 2017, the three TP
4
Agenda Item#7b
Page 5 of 7
exceedances occurred within Inner and Outer Clam Bay (stations 3 and 8, respectively) and
also at station 9, which had been the only site not to have been impaired in May 2017. There
were no exceedances of the TP criteria in July of 2017.
Table 1. Observed TP Exceedances (marked with an "X") at the ambient Clam Bay
surface water sample sites over the period of November 2016 to July 2017.
Sampling event
Station Nov Dec Jan Feb Mar Apr May Jun Jul
1 X X X X
2 X X X X X
3 X X X
4 X X
5 X X X
6 X X X
7 X X
8 X X
9 X X
May of 2017 had the greatest number of TP exceedances of the nine monthly sampling
events, with all stations but 9 (south of Seagate Drive) being out of compliance with NNC
criteria. Interestingly, the only two months with no exceedances of TP criteria are January of
2017 and July of 2017, which represent conditions of water temperature and rainfall patterns
that are quite different from each other.
In addition, water quality data from the seven Clam Bay Outfall monitoring stations were
compared to the proposed downstream protective values (DPV) for Clam Bay (PBS&J 2011).
Outfall TN and TP concentrations were compared to the median and 90th percentile DPV
values to determine if elevated concentrations were identified (Appendix B).
The median and 90th percentile DPVs for TN are 1.31 and 1.80 mg/L, respectively (PBS&J
2011). The median and 90th percentile DPVs for TP are 0.10 and 0.25 mg/L, respectively. For
TN, 47 and 21 percent of the values exceeded the median and 90th percentile DPV criteria,
respectively, during the months of April to June of 2017 (Table 2). It should be noted that a
"median" value represents a value where 50 percent of samples would be expected to be in
exceedance. Similarly, it would be expected by chance alone that 10 percent of values would
exceed the 90th percentile DPV, vs. the 21 percent of TN values that exceeded the 90th
percentile value. For TP, 89 percent of values exceeded the median DPV criterion, while 32
percent of values exceeded the 90th percentile DPV criterion.
5
Agenda Item#7b
Page 6 of 7
Table 2. Percentage of TN or TP concentrations from outfall stations which exceeded
the median or 90th percentile DPV values.
DPV Total Nitrogen Total Phosphorus
Median 90th Percentile Median 90th Percentile
Percent of values below 53 79 11 68
Percent of values above 47 21 89 32
Discussion
It should be noted that because this data analysis is not based on a full year of water quality
data, and thus while it is indicative of potential findings for a calendar year, it is not necessarily
predictive of what would be found with a calendar years' worth of data. The FDEP-adopted
SSAC for Clam Bay requires data analysis on a calendar year basis (FAC 62-302.531).
However, quarterly status reports can be useful as an early warning system if water quality
appears to be significantly different from expected ranges.
As in past reports, the findings displayed here suggest phosphorus concentrations in the open
waters of Clam Bay are likely problematic, as 41 percent of TP values exceed a threshold
criterion value meant to "hold the line" on nutrient concentrations in the bays. In addition,
elevated nutrient concentrations at outfall sampling locations are indicated by the finding that
32 percent of TP and 21 percent of TN values from sampled outfall locations exceed a criterion
that is expected to be exceeded only 10 percent of the time. These findings suggest that
elevated TP concentrations in Clam Bay could be due to activities occurring on the watershed,
although elevated TP values could also be due to natural sources within the bay, such as
nutrient loads from seabirds (guano is rich with phosphorus). Such findings suggest that
sampling of the watershed, such as occurs at the outfall locations, should continue.
At the outfall locations, concentrations of nitrogen do not appear to be overly problematic, as
exceedance rates for the median DPV concentration are mostly in-line with expectations.
However, the highest TN values were more common than expected, as more than 20 percent
of samples exceeded a criterion that was only expected to be exceeded 10 percent of the time.
For phosphorus, 89 percent of samples exceeded a threshold criterion that was only expected
to be exceeded 50 percent of the time. In addition, 32 percent of TP values during May to July
exceeded a threshold value that was only expected to be exceeded 10 percent of the time.
Taken as a whole, the water quality data collected between the months of May and July of
2017 suggest that the open waters of Clam Bay have more phosphorus than would be
expected, as 41 percent of samples exceeded the criteria spelled out for Clam Bay in the State
of Florida's Impaired Waters Rule (FAC 62-302.531). For nitrogen, no such concern currently
exists. These results come from sampling events during Southwest Florida's typical transition
from dry to wet season weather patterns, and the water quality in the bay represents a mixture
of freshwater runoff and tidal influences from the Gulf of Mexico that occurs during these
months.
6
Agenda Item#7b
Page 7 of 7
Maintenance of the flushing influence of Clam Pass is important to the water quality of Clam
Bay. If Clam Pass was to close, the elevated nutrient concentrations from watershed runoff
would likely result not only in the expression of eutrophication through mechanisms such as
phytoplankton and/or macroalgae blooms, but the reduced tidal mixing and lowered salinities
would likely result in Clam Bay exceeding its FDEP-adopted water quality standards.
7
Agenda Item#7b-1
Page 1 of 1
Total Phosphorus Exceedances in Clam Bay
SS 1 SS 2 SS 3 SS 4 SS 5 SS 6 SS 7 SS 8 SS 9
3/25/15 X X
4/29/15 X X X X
5/26/15 X X _
6/30/15 X X
7/16/15 X
8/26/15
9/16/15 X
10/21/15 X X X
11/17/15
12/09/15
1/13/16 X
2/25/16
3/23/16 X X X
4/27/16 X
5/25/16 X X X X
6/22/16 X X X
7/20/16 X X
8/25/16 X X
9/20/16 X X X
10/12/16
11/09/16 X
12/06/16 X
1/19/17
2/23/17 X X X X
3/21/17 X X X X X
4/18/17 X X X X
5/24/17 X X X X X X X X
6/21/17 X X X
7/13/17
Total 17 14 5 3 7 4 5 2 3
#7b-2
Agenda Item .4.rItv
- -,.`1 -,
„,„,....,A;.44-4`.-
Quality
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Water
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Observations and Recommendations
Based upon a review of the August 2017 monitoring results,the following observations were made
regarding the water quality trends within the six Pelican Bay stormwater lakes.
Nutrients have shown little response over the past year.The lakes continue to experience nutrient
concentrations at hypereutrophic levels.While some lakes have experienced slightly lower levels since the
last quarter,the improvements are not statistically significant.Basin 6 showed a significant increase in TP
levels in February 2017 which cannot be explained and may be related to physical perturbations of the
settled sediment within the lakes in this basin.TP levels have since declined and returned to levels
previously recorded in this basin.
Total recoverable copper concentrations remain significantly lower than those measured prior to August
2013 when copper sulfate use for algae control ceased.All lakes experienced a decrease in average total`
copper concentration in August 2017 compared to the preceding quarter,well below elevated historical
concentrations.This trend shows continuing improvement in cooper levels in the stormwater lakes.
Seasonal patterns in copper concentrations appear driven but rainfall.August is the peak of the normal wet
season when stormwater flows dominate the water balance,thereby diluting concentrations of conservative
ions.February is during the driest period,when groundwater inputs dominate with greater inorganic ion
concentrations.However,copper concentrations appear to have reached an equilibrium with sediment
cycling but a declining trend is notable.
While an overall decline in copper concentrations has been observed in the lakes,copper concentrations
continue to be significantly above the Florida Class Ill water body standard.While state water quality criteria
are not directly applicable to the stormwater lakes,the FDEP has expressed concern that stormwater
discharges to Clam Bay may be having an effect on estuarine water quality for copper.
Long-term data indicate that both phosphorus and copper are cycling from lake sediments and have reached
equilibrium.Controlling phosphorus cycling could reduce the potential for algal blooms. Planting littoral
vegetation would promote additional treatment and reduce the overall nitrogen load to the bay.
14