Hillsborough County Municipal Service Benefit Unit
Sweetwater Creek
Phase II Feasibility Report
Prepared for
Hillsborough County
Public Works Department
Prepared by
The Abaco Group, LLC.
Tetra Tech, Inc.
Fishkind & Associates, Inc.
1040 W. Industrial Ave., Bay 1
1901 S. Congress Ave., Ste. 200
12051 Corporate Blvd.
Boynton Beach, FL 33426
Boynton Beach, FL 33426
Orlando, FL 32817
October 22, 2014
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
ES-2
EXECUTIVE SUMMARY
In January 2009 the Hillsborough County Board of County Commissioners enacted County
Ordinance 09-01, the Canal Dredging Municipal Service Benefit Unit and Assessment Procedure Ordinance.
This ordinance creates a financing mechanism in which local communities in Hillsborough County
can request that County to create discrete Canal Dredging Municipal Service Benefit Units (MSBUs)
to finance canal dredging in order to resolve navigational issues in the residential, saltwater canals
within their community.
The Hillsborough County Canal Dredging Program Manual (2009) outlines the intent and purpose of
the County’s Canal Dredging Program and anticipated timelines for MSBUs. In December 2009,
Tetra Tech was contracted by Hillsborough County to provide Professional Engineering Services for
the implementation of the County’s Canal Dredging Program. The Canal Dredging Program
outlined in the Hillsborough County Canal Dredging Program Manual (2009) has been designed to
operate in three phases: Phase I: Project Definition and Letter of Intent, Phase II: Feasibility Phase
and Phase III: Design, Permitting and Construction.
This feasibility report was prepared in support of Phase II for the Sweetwater Creek Canal Dredging
Improvement Unit (CDIU). Included in this report is a review of the bathymetric survey, marine
resource investigations, preliminary characterization of dredge sediments and water quality,
preliminary engineering design, disposal options, environmental regulatory review, construction and
bond financing cost estimation associated with the Sweetwater Creek CDIU.
In accordance with Ordinance 09-01 (§2.04(B)(1)), the boundary of the CDIU is presented in Figure
ES-1. Included in the CDIU are two areas depicting all benefiting parcels: 1) the 27 properties
included in the Letter of Intent (LOI), and 2) five additional properties to the south that were
identified during the Feasibility Phase. These additional properties are downstream of the properties
in the LOI where a shoal area was identified from the bathymetric survey conducted by Post,
Buckley, Schuh and Jernigan, Inc. (PBS&J, 2006). The bathymetry indicates that the shoal supports
water depths of three to five feet and extends across the width of the creek. As such, this shoal
feature was added to the CDIU since the shoal has the potential to either impede navigational access
upstream or increase in size in the near future, thereby reducing the benefit of the proposed
dredging.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
ES-2
Figure ES-1. Sweetwater Creek canal Dredging Improvement Unit
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page i
ABBREVIATIONS AND ACRONYMS
BOCC
Hillsborough County Board of County Commissioners
CCDPM
Comprehensive Canal Dredging and Preventative Measures Study
CDIU
Canal Dredging Improvement Unit
CDPM
Canal Dredging Program Manual
cy
cubic yards
DMMA
dredge material management area
ECDU
equivalent canal dredging unit
EPC
Hillsborough County Environmental Protection Commission
F.A.C
Florida Administrative Code
FDEP
Florida Department of Environmental Protection
LOI
Letter of Intent
m
meter
MLW
mean low water
MSBU
Municipal Service Benefit Unit
PAH
polyaromatic hydrocarbons
PEL
SQAG probable effects level for aquatic organisms
SCTLs
FDEP soil cleanup target levels
SQAGs
FDEP sediment quality assessment guidelines
TEL
SQAG threshold effects level for aquatic organisms
TPA
Tampa Port Authority
USACE
US Army Corps of Engineers – Jacksonville District
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page ii
Table of Contents
1.
Introduction ...............................................................................................................................................1
2.
Project Purpose & Intent .........................................................................................................................3
3.
Project Area Description..........................................................................................................................3
4.
Site Investigations......................................................................................................................................5
4.1
Bathymetric Survey ...........................................................................................................................5
4.2
Benthic Community Assessment ....................................................................................................5
4.3
Sediment Sampling and Analysis ....................................................................................................5
4.1
Water and Elutriate Sampling........................................................................................................10
5.
Project Design..........................................................................................................................................13
5.1
Dredge Footprint and Volume .....................................................................................................13
4.1
Construction Techniques ...............................................................................................................13
4.2
Site Conditions ................................................................................................................................15
4.3
Dredge Material Disposal Options...............................................................................................15
4.3.1
Dredge Material Reuse Options................................................................................................16
4.3.2
Landfill Disposal .........................................................................................................................16
4.4
Dredging Capital Cost ....................................................................................................................16
4.4.1
Estimate Basis..............................................................................................................................16
4.4.2
Assumptions ................................................................................................................................16
6.
Regulatory Coordination ........................................................................................................................20
5.1
Agency Authorizations and Permit Requirements .....................................................................20
5.2
Natural Resource Considerations .................................................................................................23
5.2.1
Wetland Impacts .........................................................................................................................23
7.
Assessments..............................................................................................................................................23
6.1
Benefits Analysis..............................................................................................................................23
6.2
Total Project Cost Estimate...........................................................................................................23
6.3
Specific Assessment Estimate .......................................................................................................24
8.
References.................................................................................................................................................25
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page iii
Figures
Figure 1. Project location map.........................................................................................................................4
Figure 2. Sweetwater Creek CDIU 2006 and 2011 sediment and water sampling locations..................6
Figure 3. Plan and section veiws of the Sweetwater Creek CDIU dredge area ......................................14
Figure 4. 1938 Aerial photograph of the Sweetwater Creek CDIU project area and 2006 shoreline .21
Tables
Table 1. Lists the criteria and the composite scoring for the Sweetwater Creek LOI application ........2
Table 2. Summary of 2011 sediment samples collected from proposed CDIU.......................................7
Table 3. Values of pollutant metals from 2006 and 2011 sediment cores.................................................8
Table 4. Values of Polyaromatic Hydrocarbons (PAHs) from 2006 and 2011 sediment cores.............9
Table 5. Values of Carcinogenic PAHs from 2006 and 2011 sediment cores ........................................10
Table 6. Values of metals from 2011 surface water samples, 2006 and 2011 elutriate samples...........11
Table 7. Values of Polyaromatic Hydrocarbons (PAHs) - 2006 elutriate 2011 water samples ............12
Table 8. Values of Carcinogenic PAHs - 2006 elutriate and 2011 water samples..................................12
Table 9. Engineer’s opinion of probable cost of design/construction....................................................17
Table 10a. Principal assumptions of cost estimate......................................................................................18
Table 10b. Cost category assumptions .........................................................................................................18
Table 11. ECDU Calculations and Subsequent Debt Allocation .............................................................24
Appendices
Appendix I
Homeowner Property Approval Signatures
Appendix II
2006 Bathymetric Survey Results
Appendix III
2010 Benthic Community Assessment
Appendix IV
2011 Laboratory Results of Sediment and Water Quality Analyses
Appendix V
Sweetwater Creek Hydrodynamic Evaluation
Appendix VI
Sweetwater Creek Assessment Methodology Report
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 1
1.
Introduction
In March 2007, after two years of study, which included six town hall meetings and over 20 monthly
meetings, the Hillsborough County Board of County Commissioners (BOCC) accepted the finding
of the Canal Advisory Committee and their Comprehensive Canal Dredging and Preventative
Measures Study (CCDPM). The CCDPM examined eight coastal residential canal communities
within the unincorporated portions of Hillsborough County (referred herein as “County”) in order
to determine the location and extent of sedimentation; as well as the approximate cost for
implementing each project area. One of the primary recommendations from this study was to enact
a canal dredging ordinance in which communities could independently choose to pay for the
necessary improvements. Refer to the County website for the complete set of the CCDPM studies
.
The BOCC enacted County Dredging Ordinance (No. 09-1), Canal Dredging Municipal Service
Benefit Unit (MSBU), and Assessment Procedure Ordinance in January 2009. The County Public
Works Department, with the assistance of other County organizations, was tasked with
implementing the County Ordinance. The resulting Canal Dredging Program Manual (CDPM)
outlines the County’s Canal Dredging Program and process, its purpose, intent, and anticipated
timelines for the eight navigation projects. It also outlines internal policies within the program so
that applicants are aware of their rights and responsibilities; as well as the County’s rights and
responsibilities. A key feature of the dredging program is that the total dredging cost of each
community project is to be borne by the residents whose properties directly benefit from the
project.
Consistent with the County Dredging Ordinance, the Canal Dredging Program is limited to the
cleaning, deepening and widening of navigable salt or brackish water canal waterways that are
adjacent to properties located in the unincorporated areas of the County. The intent of the dredging
program is to provide recreational boaters in the canals with navigational access along the centerline
of the canals to Tampa Bay. Freshwater canals, lakes, historic drainage ditches or other storm water
conveyance structures, whose original intent was solely to convey stormwater are excluded from
participating in this program.
The Canal Dredging Program outlined in the CDPM has been designed to operate in three phases:
Phase I: Project Definition and Letter of Intent, Phase II: Feasibility Phase and Phase III: Design,
Permitting and Construction.
Phase I
Under Phase I, communities located within one of the eight coastal regions identified in the
CCDPM (Bayport, Baycrest, Dana Shores, Alafia, Apollo North, Apollo South, Essex Downs and
Ruskin) can establish a Canal Dredging Improvement Unit (CDIU). The properties within the
community that will receive “special and peculiar” benefits from the dredging project(s) comprise
the CDIU.
Each community must select a spokesperson and define the CDIU project area, which includes the
properties that will benefit from the navigational improvements. A Letter of Intent (LOI) is then
prepared by the community stating their request for the County to investigate their CDIU. The LOI
is submitted to the Director of the Hillsborough County Public Works Department for
consideration.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 2
In January 2010, a total of five LOI applications were submitted to the County, which included LOI
applications from the Bayport, Sweetwater Creek, Flamingo Canal, Masters Canal, and Shell Point
Road communities. These LOI applications and associated information were evaluated, scored and
ranked by ten scoring criteria that were developed during the LOI Phase I. On September 14, 2010,
a final scoring criteria and completion of a Decision Matrix was performed by a committee of
Hillsborough County staff members in accordance with the procedures outlined in the Canal
Dredging Manual. It was determined that the Sweetwater Creek LOI was the top ranked application
and would advance to Phase II – Feasibility Phase, of the Program. Refer to Table 1 for a summary
of the Sweetwater Creek LOI evaluation.
Table 1. Lists the criteria and the composite scoring for the Sweetwater Creek LOI application
The range of scores for the applications was from 16.42 to 21.12. The Sweetwater Creek LOI
application complied with all of the requirements of the Canal Dredging Program Manual and
scored 21.12. A total of 15 participating homeowners/residents signed the Sweetwater Creek LOI
application. All 15 signatures were confirmed as willing participants in the County Dredging
Program, which totaled 55.56 % support within the proposed CDIU. In accordance with County
Ordinance No. 09-1, at least 51% of different property owners located within the CDIU is required
(Appendix I).
Phase II
Phase II includes the implementation of the feasibility phase of the Sweetwater Creek CDIU. The
feasibility phase involves the review of: 2006 bathymetric survey; 2010 and 2011 marine resource
investigations; preliminary characterization of dredge sediments and water quality; preliminary
engineering design; potential disposal options; and agency meetings and regulatory coordination.
A summary of the 2006, 2010 and 2011 field investigations are described in Section 4 of this report.
The preliminary dredge design and potential dredge material disposal options are discussed in
Section 5. Results of the 2010 and 2011 meetings and guidance received from the regulatory and
commenting agencies are provided in Section 6.
The Phase II efforts also include a summary of the comprehensive assessment methodology,
individual property owner benefits from the implementation of the Sweetwater Creek CDIU, and an
estimate of the capital cost to implement the CDIU. The assessment methodology and associated
costs are provided in Section 7.
Montalvo
Mueller
Deese
1
13%
0.26
0.26
0.26
2 Project Complexity
13%
1.17
1.17
1.17
3 Submerged Land Ownership
12%
1.20
1.20
1.20
4 Marine Resource Impacts
12%
0.96
0.84
0.84
5 Financial Stability
12%
0.28
0.28
0.28
6 Accessibility to Open Water
11%
0.55
0.55
0.55
7
10%
1.00
1.00
1.00
8
8%
0.80
0.80
0.56
9
6%
0.90
0.48
0.66
#
3%
0.30
0.30
0.30
7.42
6.88
6.82
Evaluation Criteria
Property Owner Support
Relative
Weight
Evaluators
21.12
Property Owner Diversity
Water Quality Improvement
Sediment Quality
Submittal Date
Individual Totals
Composite Score
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 3
Phase III
Upon finalization of the feasibility report, it will be presented to the Sweetwater Creek CDIU
spokesperson for dissemination to the community. A petition package of the project will be
prepared and validated by the community. Upon BOCC approval of the petition package, the
project will enter into Phase III (design, permitting and construction).
2. Project Purpose & Intent
Prior to the 1980’s, several residential saltwater “finger” canals were created throughout
Hillsborough County. The intent of the finger canals was to maximize the waterfront surface area.
The finger canal design created a low flushing/low energy environment, preventing silt, sediment
and detrital material from moving through the system. This has resulted in settling and infilling of
sediment and material in the canals, limiting ingress/egress by adjacent property owners.
Per County Ordinance 09-01, this project supports Hillsborough County’s program initiative to
clean, deepen and widen saltwater canals adjacent to properties located in the unincorporated area of
Hillsborough County. The purpose of this project is to allow the residential canal community of
Sweetwater Creek navigational access to Tampa Bay. Navigational access of -5 ft mean low water
(MLW) will be established in Sweetwater Creek from south of Memorial Highway Bridge to a point
in the waterway where existing depths are -5 ft MLW or greater.
3. Project Area Description
The project is located approximately 5,000 ft from open water of Tampa Bay and is located within
the Dana Shores region of Hillsborough County. The proposed dredge limit extends from the
Memorial Highway Bridge to a point approximately 2,300 ft south along the centerline of
Sweetwater Creek (Figure 1).
The Sweetwater Creek CDIU includes all canal-front, single family residential properties along the
east side Saltwater Boulevard directly adjacent to the dredge area. It also includes the three large
canal-front parcels on the east side of the canal (Scottish Rite Temple Association, Sweetwater Cove
Apartments, Egypt Temple), also directly adjacent to the dredge area. Sweetwater Cove Apartments
is a multifamily complex located along Ginger Cove Drive, which is owned by a single management
company and does not appear to have a homeowner’s or condominium association. In total, there
are 27 parcels within the current CDIU project area.
With the exception of small boats (ex. canoes and kayaks), the low fixed Bridge at Memorial
Highway limits upstream access under the Bridge to vessels that can likely navigate to the project
area. There are no notable navigational obstructions downstream of the project or other significant
constraints that would affect recreational vessel or construction barge access to and from the site.
The project is likely to require temporary stockpiling of dredge material for dewatering purposes,
temporary containment, and/or sampling prior to final disposal. There are very limited potential
spoil containment area options within close proximity of the project area.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 4
Figure 1. Project location map
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 5
4. Site Investigations
Baseline investigations of the Sweetwater Creek CDIU used to support the feasibility study include:
1) a bathymetric survey and sediment core collected by Post, Buckley, Schuh and Jernigan, Inc., in
2006 (PBS&J, 2006), 2) marine resource investigations and sediment cores collected in 2010 (Tetra
Tech, 2011) and 3) sediment, water quality and elutriate sampling and analysis conducted in 2011.
4.1
Bathymetric Survey
PBS&J completed a bathymetric survey of the CDIU project area in February and March 2006 as
part of the CCDPM study (PBS&J, 2006). Appendix II includes the raw data plot and color contour
map of the 2006 bathymetric survey. The 2006 survey shows the shallowest areas (-0.75 to -3.00 ft
MLW) at the northern end of Sweetwater Creek, south of Memorial Highway Bridge. The channel
deepens to -3.00 to -5.00 ft MLW to the south with pockets of -5.00 to -15.00 ft MLW, where the
channel is at its widest.
This feasibility study utilizes the raw data from the 2006 survey as the basis for the planning and
dredged material volume estimation for the proposed project.
4.2
Benthic Community Assessment
On September 23 and 24, 2010 Tetra Tech performed a qualitative benthic resource investigation of
approximately 7.43 acres of submerged lands and natural resources within and adjacent to the
Sweetwater Creek CDIU (Appendix III). Additionally, five sediment cores were collected and
analyzed for grain size (Section 4.3).
Results from the 2010 investigations confirmed the presence of mangroves southeast of the
Memorial Highway Bridge, and five solitary oysters (three along the west bank south of the Bridge
and two along the east bank at the channel widening) (Appendix III - Figure 2). These resources
were excluded from the dredge limits.
4.3
Sediment Sampling and Analysis
One sediment core was collected in the Sweetwater CDIU (DCS1) in support of the Dredging
Feasibility Report for Dana Shores (PBS&J, 2006) (Figure 2). The 2.5 ft sediment core was collected on
the shoal at the north end of the proposed dredge footprint. The sediment sample yielded 96.1%
sand (3.9% passing the 200 sieve), with a total organic content of 7.9%. The median grain size is
0.18 mm, classifying the sediment as fine sand.
Pollutant metals in the 2006 core were reported as being below residential and commercial Florida
Department of Environmental Protection (FDEP) Soil Cleanup Target Levels (SCTLs) (Chapter 52-
777, Florida Administrative Code [F.A.C.]). However, elevated levels of polyaromatic hydrocarbons
(PAHs) (e.g., Benzo(a)pyrene, Benzo(b)fluoranthene, Benzo(g,h,i)perylene, Benzo(k)fluoranthene,
bis(2-ethylhexyl) phthalate, Chrysene, Fuoranthene, and Pyrene) were detected in the sediment
sampling following the EPA 8270C method.
Sediment cores collected in the CDIU in September 2010 were evaluated using a visual assessment
technique that follows the Unified Soils Classification System (Appendix III). No chemical analyses
were conducted on the 2010 samples. Cores located in the middle and southern reaches of the
project site consisted of a very fine, well sorted organic muck. The core located at the most northern
reach of the CDIU, just south of Memorial Highway Bridge, consisted of a well sorted, fine to
medium grained sand. A shoal has formed south of the Bridge where coarser grained material has
aggregated.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 6
Figure 2. Sweetwater Creek CDIU 2006 and 2011 sediment and water sampling locations
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 7
In May 2011, Tetra Tech collected five sediment cores throughout the CDIU for visual assessment,
chemical and physical analysis (Figure 2). Sediments were extracted using a hand corer which
penetrated to refusal. The cores were visually assessed for average grain size, organic content, color,
and odor. Organic muck was observed throughout the mid and central portions of the proposed
dredge area (SED 02 to SED 04). The core sample collected towards the north end of the dredge
area (SED 01) was predominantly comprised of fine sand. The grain size results are similar to those
reported by PBS&J (2006) for DSC1. Water depths within the CDIU ranged from 2.53 to 6.46 ft. A
summary of the 2011 findings are provided in Table 2.
Table 2. Summary of 2011 sediment samples collected from proposed CDIU
Note: All sampled collected on May 27, 2011. Tide corrected to Old Port Tampa, FL NOAA Station Id:
8726607. Sample SED 05 collected outside of CDIU, south of project area.
Sediment samples were homogenized, transferred to glass jars, and placed on ice prior to transport
to Millennium Laboratories Inc. for chemical analysis (Appendix IV). A summary of the 2006
sample (DSC1) and 2011 lab results cores are provided in Tables 3 through 5. It is important to note
that SED 05 was collected outside of the proposed dredge footprint, south of the project limits.
Tables 3 through 5 include the numerical sediment quality assessment guidelines (SQAGs) for the
threshold effects level (TEL) and probable effects level (PEL). The TEL represents the upper limit
of the range of sediment contamination that has no measurable effect on aquatic organisms. The
PEL is the estimated lower limit of the contaminant concentration associated with adverse biological
effects. The SCTLs are the amount of contaminant in a soil that, when leached into surface waters
will be equal to groundwater cleanup target levels (GCTLs). The SCTLs reference effects on humans
rather than organisms, therefore these values are typically higher than TELs and PELs.
The laboratory results shown in Table 3 from samples collected in the mid and southern ends of the
CDIU (SED 02 to SED 04) indicate TEL exceedences for metals and residential SCTL exceedences
particularly for arsenic. Table 4 also shows PAH exceedences in the mid and southern ends of the
CDIU. Carcinogenic PAHs listed in Table 5 indicate exceedences of both residential and
commercial SCTLs in all samples. SQAG TELs and PEL exceedences occur in all sample locations,
except at SED 01, south of the shoal formation.
Sample ID
Location
Sample
Time
(hrs)
Total
Water
Depth (ft)
Tide
Corrected
Depth (ft)
Depth of
Penetration
(ft)
Description
N 27o58’47.6”
W082o33’43.3”
N 27o58’43.7”
W082o33’42.9”
N 27o58’40.5”
W082o33’39.2
N 27o58’35.0”
W082o33’38.3
N 27o58’29.2”
W082o33’49.8
Fine sand with muck, slight organic
odor
SED 02
1450
4.69
6.20
1.31
Organic muck, with some sand.
Dark grey, strong organic odor
SED 01
1415
2.53
4.23
0.88, 0.62
Organic muck with fine sand. Dark
brown, strong organic odor
SED 04
1546
5.31
6.46
1.87
Organic muck with fine sand. Dark
grey/dark brwn. Detritus and strong
organic odor
SED 03
1525
4.95
6.29
1.64
Medium dark and light grey sand
SED 05
1610
6.04
6.20
~0.98
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 8
Table 3. Values of pollutant metals from 2006 and 2011 sediment cores
Note: Blue shade = Above SQAG TELs; Bold = Above Residential SCTLs; * = Containment is not a health
concern for this exposure scenario; N/A = necessary data not available; U = undetected
EPA 7471A
EPA
6010B ICP
EPA
365.2
EPA
1664
To
ta
lP
ho
sp
ho
ro
us
(m
g/
kg
)
N
on
-P
ol
ar
M
at
er
ia
ls
(m
g/
kg
)
7.24
0.676
52.3
18.7
30.2
124
0.13
N/A
N/A N/A
N/A
41.6
4.21
160
108
112
271
0.696
N/A
N/A N/A
N/A
2.1
82
210
150
400
26000
3
80000
N/A N/A
N/A
12
1700
470
89000
1400 630000
17
*
N/A N/A
N/A
0.251
U
0.551
0.589
6.98
6.95
U
195
N/A N/A
N/A
0.4
0.16
1.1
1.5
1.9
5.1
0.01
310
N/A N/A
N/A
3.1
0.70
20.0
27.0
2.7
120.0
0.12
7800
N/A N/A
N/A
6.0
1.30
34.0
40.0
65.0
190.0
0.13
9600
N/A N/A
N/A
7.5
1.70
59.0
49.0
100.0
230.0
0.20
20000
N/A N/A
N/A
0.4
0.19
1.3
2.6
2.4
4.3
0.01
310
N/A N/A
N/A
SQAG Threshold Effects Level
DSC1
Se
di
m
en
tS
am
pl
e
ID
SQAG Probable Effects Level
EPA 6010B ICP
To
ta
lN
itr
og
en
(m
g/
kg
)
SCTL Commercial
SCTL Residential
Metals
Le
ad
(m
g/
kg
)
Zi
nc
(m
g/
kg
)
Al
um
in
um
(m
g/
kg
)
M
er
cu
ry
(m
g/
kg
)
Co
pp
er
(m
g/
kg
)
Ar
se
ni
c
(m
g/
kg
)
Ca
dm
iu
m
(m
g/
kg
)
Ch
ro
m
iu
m
(m
g/
kg
)
SED 01
SED 02
SED 03
SED 04
SED 05
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 9
Table 4. Values of Polyaromatic Hydrocarbons (PAHs) from 2006 and 2011 sediment cores
Note: Blue shade = Above SQAG TELs; Green shade = Above SQAG TELs and PELs; U = undetected
Py
re
ne
(m
g/
kg
)
0.0067 0.0059 0.0469 N/A N/A 0.0202 0.0212
0.113
0.0346 0.0867
0.153
0.0889
0.128
0.245
N/A N/A
0.201
0.144
1.494
0.391
0.544
1.398
2400
1800
21000
2500
200
210
2600
3200
55
2200
2400
20000 20000 300000 52000
1800
2100
33000 59000
300
36000
45000
U
U
U
0.105 N/A
U
U
0.140
U
U
0.137
0.0009 0.0017 0.0006 0.0630 0.0065 0.0046 0.0011 0.1000 0.0005 0.0330 0.1000
0.0089 0.0150 0.0440 1.1000 0.0150 0.0110 0.0190 1.7000 0.0022 0.3800 2.4000
0.0078 0.0110 0.0290 0.9100 0.0120 0.0084 0.0120 1.3000 0.0015 0.3000 2.1000
0.0040 0.0130 0.0160 0.7600 0.0190 0.0130 0.0140 1.1000 0.0014 0.2200 1.7000
0.0009 0.0016 0.0006 0.0045 0.0064 0.0045 0.0010 0.0034 0.0005 0.0096 0.0053
SQAG Threshold Effects Level
SQAG Probable Effects Level
DSC1
Se
di
m
en
tS
am
pl
e
ID
EPA 8270
Poly Aromatic Hydrocarbons
(PAHs)
SCTL Residential
SCTL Commercial
SED 01
SED 02
SED 03
SED 04
SED 05
An
th
ra
ce
ne
(m
g/
kg
)
Fl
uo
ra
nt
he
ne
(m
g/
kg
)
Ac
en
ap
ht
hy
le
ne
(m
g/
kg
)
Ac
en
ap
ht
he
ne
(m
g/
kg
)
Fl
uo
re
ne
(m
g/
kg
)
Ph
en
an
th
re
ne
(m
g/
kg
)
Be
nz
o(
g,
h,
i)p
er
yl
en
e
(m
g/
kg
)
1-
M
et
hy
ln
ap
ht
ha
le
ne
(m
g/
kg
)
N
ap
ht
ha
le
ne
(m
g/
kg
)
2-
M
et
hy
ln
ap
ht
ha
le
ne
(m
g/
kg
)
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 10
Table 5. Values of Carcinogenic PAHs from 2006 and 2011 sediment cores
Note: Blue shade = Above SQAG TELs; Green shade = Above SQAG TELs and PELs; Bold = Above
Residential SCTLs; Bold and italicized = Above Residential and Commercial SCTLs; N/A = necessary data
not available; U = undetected
Additional sediment sampling to the planned dredge depth (-5 ft MLW) plus 1 ft for potential over-
dredge allowance is needed for complete chemical and physical analysis of the dredge profile.
4.1
Water and Elutriate Sampling
In May 2011, water samples were collected from the middle of the water column prior to collecting
sediment samples at SED 01 to SED 05. Water samples were poured into glass jars, placed on ice
and transported to Millennium Laboratories Inc. for chemical testing for surface water and
elutriates. Tables 6 through 8 below provide a summary of the laboratory results from the 2006
elutriate test at DSC1 and water quality and elutriate testing at all sites from the 2011 event.
The results were compared to FDEPs Surface Water Cleanup Target Levels (SWCTL) criteria for
marine surface waters (Chapter 52-777, F.A.C.). It is important to note that samples WS 05 and ES
05 were collected outside of the CDIU, south of the proposed dredge footprint.
Be
nz
o(
a)
py
re
ne
(m
g/
kg
)
Be
nz
(a
)a
nt
hr
ac
en
e
(m
g/
kg
)
Be
nz
o(
b)
flu
or
an
th
en
e
(m
g/
kg
)
Be
nz
o(
k)
flu
or
an
th
en
e
(m
g/
kg
)
Ch
ry
se
ne
(m
g/
kg
)
D
ib
en
zo
(a
,h
)A
nt
hr
ac
en
e
(m
g/
kg
)
Id
en
o(
1,2
,3
,-c
d)
py
re
ne
(m
g/
kg
)
0.0888 0.0748 N/A N/A
0.108
0.00622 N/A
0.763
0.639 N/A N/A
0.846
0.135
N/A
0.1
0.01
0.01
0.001
0.0001
0.1
0.01
0.7
0.07
0.07
0.007
0.0007
0.7
0.07
0.092
U
0.155
0.097
0.103
U
U
0.0620 0.0510 0.1100 0.0310 0.0680
0.0047
0.0570
1.0000 0.8500 2.3000 0.7900 1.6000
0.2500
1.1000
1.0000 0.8400 1.9000 0.6700 1.3000
0.2000 0.9200
0.8300 0.6600 1.7000 0.5700
1.1000
0.0140
0.7800
0.0015 0.0014 0.0025 0.0024 0.0012
0.0046
0.0030
SQAG Threshold Effects Level
SQAG Probable Effects Level
DSC1
Se
di
m
en
tS
am
pl
e
ID
SCTL Residential
EPA 8270
Poly Aromatic Hydrocarbons
(PAHs)
SCTL Commercial
SED 01
SED 02
SED 03
SED 04
SED 05
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 11
Table 6. Values of metals from 2011 surface water samples, 2006 and 2011 elutriate samples
Note: Bold = Above SWCTL; N/A = necessary data not available; U = Undetected
Water quality samples showed SWCTL exceedences for copper and mercury throughout the project
area (Table 6). Contributing sources are likely from both anthropogenic and natural factors.
An elutriate test is designed to simulate release of contaminants from a sediment during a
disturbance. Results of elutriate testing of sample DS-C1, and ES 01 through ES 04 located within
the project area showed that concentrations of chromium, copper, lead, mercury and aluminum
during a disturbance exceeded SWCTLs (Table 6). Removing the material would be expected to
result in lower concentrations of copper and lead in solution following a disturbance.
Table
7
shows
SWCTL exceedences
of
three
PAH compounds
(Acenaphthylene,
Benzo(g,h,i)perylene, Phenanthrene) throughout the water column. Table 8 shows SWCTL
exceedences of all carcinogenic PAHs at all sample stations. There are several sources of PAHs, one
primary source is from creosote treated pilings.
EPA 7471A
EPA
6010B ICP
EPA
365.2
EPA
1664
To
ta
lP
ho
sp
ho
ro
us
(m
g/
L)
N
on
-P
ol
ar
M
at
er
ia
ls
(m
g/
L)
0.05
0.009
0.05
0.0037
0.0085
0.086
0.000025
1.5
**
**
5
0.004 0.001
0.002
0.0044
0.004
0.009
0.0001
0.20
0.150
0.680
3.2
0.004 0.001
0.002
0.0043
0.004
0.0079
0.0001
0.23
0.100
0.780
3.2
0.004 0.001
0.004
0.0063
0.004
0.0095
0.0001
0.20
0.078
0.530
3.2
0.004 0.001
0.004
0.0038
0.004
0.0068
0.0001
0.27
0.062
0.800
3.1
0.004 0.001 0.0033
0.0066
0.004
0.010
0.0001
0.20
0.094
0.930
3.6
0.001
U
U
0.009
0.014
0.044
U
0.48
N/A N/A
N/A
0.008 0.002
0.005
0.004
0.008
0.008
0.0001
0.4
N/A N/A
N/A
0.012 0.003 0.0075
0.006
0.012
0.012
0.0001
0.6
N/A N/A
N/A
0.008 0.002
0.005
0.004
0.008
0.008
0.0001
0.4
N/A N/A
N/A
0.008 0.002
0.005
0.004
0.008
0.008
0.0001
0.4
N/A N/A
N/A
0.008 0.002
0.005
0.004
0.008
0.008
0.0001
0.4
N/A N/A
N/A
DSC1
E
lu
tri
at
e
Sa
m
pl
e
ID
To
ta
lN
itr
og
en
(m
g/
L)
Ar
se
ni
c
(m
g/
L)
Ca
dm
iu
m
(m
g/
L)
Ch
ro
m
iu
m
(m
g/
L)
Co
pp
er
(m
g/
L)
Le
ad
(m
g/
L)
Zi
nc
(m
g/
L)
M
er
cu
ry
(m
g/
L)
Al
um
in
um
(m
g/
L)
SWCTL Marine Surface Water
Su
rf
ac
e
W
at
er
Sa
m
pl
e
ID
WS01
WS02
WS03
WS04
WS05
Metals
EPA 6010B ICP
ES 01
ES 02
ES 03
ES 04
ES 05
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 12
Table 7. Values of Polyaromatic Hydrocarbons (PAHs) - 2006 elutriate 2011 water samples
Note: U = undetected
Table 8. Values of Carcinogenic PAHs - 2006 elutriate and 2011 water samples
Note: U = undetected
Py
re
ne
(m
g/
L)
2700
0.031
110000
0.031
95
30
30
0.3
26
0.031
0.3
0.1600 0.1500 0.1100 0.0500 0.1700 0.1900 0.1900 0.1100 0.1600 0.1400 0.1900
0.1600 0.1500 0.1100 0.0500 0.1700 0.1900 0.1900 0.1100 0.1600 0.1400 0.1900
0.1600 0.1500 0.1100 0.0500 0.1700 0.1900 0.1900 0.1100 0.1600 0.1400 0.1900
0.1600 0.1500 0.1100 0.0500 0.1700 0.1900 0.1900 0.1100 0.1600 0.1400 0.1900
0.1600 0.1500 0.1100 0.0500 0.1700 0.1900 0.1900 0.1100 0.1600 0.1400 0.1900
U
U
U
U
U
U
U
U
U
U
U
Elutirate Sample DSC1
Ph
en
an
th
re
ne
(m
g/
L)
1-
M
et
hy
ln
ap
ht
ha
le
ne
(m
g/
L)
2-
M
et
hy
ln
ap
ht
ha
le
ne
(m
g/
L)
Fl
uo
re
ne
(m
g/
L)
Fl
uo
ra
nt
he
ne
(m
g/
L)
N
ap
ht
ha
le
ne
(m
g/
L)
EPA 8270
Poly Aromatic Hydrocarbons
(PAHs)
Ac
en
ap
ht
he
ne
(m
g/
L)
Ac
en
ap
ht
hy
le
ne
(m
g/
L)
An
th
ra
ce
ne
(m
g/
L)
Be
nz
o(
g,
h,
i)p
er
yl
en
e
(m
g/
L)
Su
rf
ac
e
W
at
er
Sa
m
pl
e
ID
SWCTL Marine Surface Water
WS01
WS02
WS03
WS04
WS05
Be
nz
o(
a)
py
re
ne
(m
g/
L)
Be
nz
(a
)a
nt
hr
ac
en
e
(m
g/
L)
Be
nz
o(
b)
flu
or
an
th
en
e
(m
g/
L)
Be
nz
o(
k)
flu
or
an
th
en
e
(m
g/
L)
Ch
ry
se
ne
(m
g/
L)
D
ib
en
zo
(a
,h
)A
nt
hr
ac
en
e
(m
g/
L)
Id
en
o(
1,2
,3
,-c
d)
py
re
ne
(m
g/
L)
0.031
0.031
0.031
0.031
0.031
0.031
0.031
0.1000 0.1000 0.1800 0.1800 0.1000
0.1500
0.0600
0.1000 0.1000 0.1800 0.1800 0.1000
0.1500
0.0600
0.1000 0.1000 0.1800 0.1800 0.1000
0.1500
0.0600
0.1000 0.1000 0.1800 0.1800 0.1000
0.1500
0.0600
0.1000 0.1000 0.1800 0.1800 0.1000
0.1500
0.0600
U
U
U
U
U
U
U
Elutirate Sample DSC1
EPA 8270
Poly Aromatic Hydrocarbons
(PAHs)
SWCTL Marine Surface Water
Su
rf
ac
e
W
at
er
Sa
m
pl
e
ID
WS01
WS02
WS03
WS04
WS05
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 13
5. Project Design
The 2006 raw bathymetric data conducted by PBS&J was reviewed to determine the spatial and
vertical extents of the planned dredge limits in Sweetwater Creek. This review focused on portions
of the canal located 15 ft from structural boundaries and private property limits, and depths less
than the planned dredge depth of -5.0 ft below mean low water (MLW) (-6.12 ft North American
Vertical Datum [NAVD], Florida State Plane West 1988).
5.1
Dredge Footprint and Volume
The factors that determine the limits of the dredging footprint are:
1. Shoal areas shallower than -5 ft MLW
2. 15 ft. setbacks from shorelines, private docks and shoreline structures, and private
property lines
3. Upstream limit of the requesting community or upstream small craft navigation limit.
The Memorial Highway Bridge represents the community and navigation limit for this
CDIU project. The bathymetric survey of the site (PBS&J, 2006) shows shallow water areas
extending south from the Memorial Bridge for a distance of about 2,100 ft.
Figure 3 shows the plan and section views of the proposed dredging area. The dredging footprint
covers an approximate area of 3.96 acres. The estimated dredging volume is 9,875 cy.
5.2
Construction Techniques
The two general techniques of dredging include hydraulic and mechanical dredging. Hydraulic
dredging utilizes a pumping system that draws in water and sediment through a suction head that
sweeps the bottom much like a vacuum cleaner. The fine grain size sediments that occur in the
project area are amenable to hydraulic dredging techniques. In typical hydraulic dredging operations,
the dredged material slurry mixture of water and sediment is pumped at a level of about 15% solids.
This means that the volume of dredged material is roughly 5 to 6 times as large as the volume of the
sediments that are in place in the channel bottom.
Hydraulic dredging can transport the dredged material significant distances away from the dredging
site since the slurry is in a fluid state. Usually a small to moderate size dredge can pump the dredge
slurry up to a mile. The addition of booster pumps along the length of the discharge pipeline can
increase the total transport distance. In most cases with very little grade change between the water
body and the dredged material handling area (DMMA), pumping distances of up to 5 miles are still
economically possible.
The DMMA is diked area that receives the dredged material slurry and is designed to allow the solids
to settle and the excess water to drain off. The dewatered dredged material may be left in place.
However, it is more frequently excavated and transported with conventional construction equipment
to a different area for beneficial reuse such as fill material or to be otherwise disposed of.
A DMMA typically consists of a diked or construction barrier contained area where the dredged
material can be placed and the drainage water can be managed. Geotextile tube systems may also be
used in place of a dike system. The dredged material is pumped into the filter fabric tubes that
contain the dredged material while letting the water drain out. Geotextile tube systems are effective
where space is limited. However, the extra costs associated with careful filling, the geotextile tube
material costs and possible polymer additives for the retention of fine grain materials can add
significant costs to the project.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 14
Figure 3. Plan and section veiws of the Sweetwater Creek CDIU dredge area
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 15
Mechanical dredging uses conventional excavation equipment such as clamshell and dragline buckets
operated by barge mounted cranes to remove sediments. Where turbidity and contaminant re-
suspension are concerns, environmental buckets can be used. Environmental buckets are variations
of clamshell buckets that fully seal to minimize the loss of sediment/water when the bucket is raised.
The dredged material is typically placed into a second barge that can shuttle back and forth between
the dredging site and the DMMA where the barge can be unloaded and the dredged material can be
dewatered and subsequently transferred to trucks for transport to its ultimate beneficial reuse or
disposal site.
Mechanical dredging removes the sediment at its in place water content. This results in a dredged
material with a significantly thicker consistency then that which results with hydraulic dredging.
Depending in the actual sediment characteristics, mechanically-dredged material may be suitable for
direct placement into trucks or transport containers without the extra dewatering step. The thicker
consistency, the lower dredged material volume and possible reduced processing/handling may
provide some advantages over hydraulic dredging.
Mechanical dredging systems require that transfer facilities be relatively close to the dredge site to
minimize the time and expense of transferring the dredged material from the dredging site to the
handling/truck loading site.
5.3
Site Conditions
The upland
area
along
the banks of
Sweetwater Creek is generally fully developed
with single and multi-family homes.
The
Scottish Rite Temple Association Inc. owns an
8.34 acre parcel on the east bank of the creek
that adjoins Memorial Highway. The southern
half of the site is an open grassed area. This
area could support dredging operations as a
DMMA site
if
suitable
temporary
use
arrangements can be worked out with the
Scottish Rite Temple. The roughly 2.8 acre
open area could provide space unloading of
the dredged material from the shuttle barges,
dewatering of
the dredged material
and
transferring of the dried dredged material to
trucks for transport to a landfill for disposal.
Site preparation, dredging operations and site
restoration may extend over a period of about
one year.
5.4
Dredge Material Disposal Options
Options for dredge material disposal is directly related to the laboratory results of sediment samples
collected throughout the dredge footprint and profile. Preliminary results indicate that there are both
SCTL and SQAG TEL and PEL exceedences, primarily in the central and southern portions of the
dredge footprint.
Photo 1. Scottish Rite Temple Site (Source:
Google Earth 2011)
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 16
5.4.1 Dredge Material Reuse Options
Preliminary laboratory results of sediment samples described in Section 4 suggest that some of the
dredge material at the north end of the proposed dredge footprint may be available for reuse.
Additional sampling conducted prior to dredging activities could isolate potential clean dredge
material on both a vertical and horizontal scale. The identification of the limits of a pocket of clean
material could potentially contribute to a reduction of construction costs. Other possible options for
the identification of clean material involve batch sampling of the temporarily stockpiled material to
determine if it can be reused or requires landfill disposal.
If the BOCC supports sediment sampling efforts to isolate clean dredge material, then there may be
opportunities for reuse at a restoration site. Discussions with the Tampa Bay Estuary Program were
initiated in 2011 to identify wetland restoration projects in the vicinity of the CDIU. At that time,
there were no restoration projects within proximity of the CDIU scheduled that were in need of
dredge material.
5.4.2 Landfill Disposal
Based on the results of the preliminary sediment cores, the dredging capital cost described in Section
5.5 assumes that all of the dredge material exceeds residential and commercial SCTLs for
carcinogenic PAHs; and therefore requires landfill disposal. This alternative assumed that the dredge
material will be transported to a FDEP approved landfill in self-contained/lined trucks. Additional,
the costs include the fee for disposal of dredge material at a Class I facility in Bartow, FL.
5.5
Dredging Capital Cost
This section develops the capital cost estimate for the proposed Sweetwater Creek residential canal
dredging project. It includes all of the preliminary investigations, the design, regulatory permitting
and construction costs. It does not, however, include the cost of financing of the project. Bond
financing will be required to afford the property owners the ability to pay their assessed portion of
the total project costs over an extended period of time rather than in a lump sum payment at the
beginning of the project.
5.5.1 Estimate Basis
This estimate was developed during the feasibility stage of the project. As such, there are
uncertainties in the costs due to portions of the project being evaluated in the preliminary review
stage of the project for regulatory and design issues. The estimate is based upon this preliminary
understanding of the project issues and supported by the preliminary site investigations described in
Section 4.0 of the main text. The project is at the 30% stage of the design development. Estimates at
this early stage of design development routinely include contingency allowances to account for the
costs associated with the project uncertainties and inflation. This estimate includes a 20%
contingency allowance. Table 9 provides the full details of the estimate.
5.5.2 Assumptions
This section outlines the assumptions that were required to develop the cost estimate. The principal
assumptions that influence several aspects of the project are discussed in first in Table 10a. The
assumptions of the estimate, that are associated with the individual cost categories, are discussed
second in Table 10b.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 17
Table 9. Engineer’s opinion of probable cost of design/construction
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 18
Table 10a. Principal assumptions of cost estimate
ASSUMPTION
DISCUSSION
Dredging footprint
and volume
3.86 acre dredging area and 9,875 cubic yards of sediment in place based
upon 2006 PBS&J bathymetric survey, a maximum depth of -5 ft. MLW and
setbacks from structures and property limits. A new bathymetric survey will
be required by the regulatory agencies in Phase II.
Sediment Quality
PAH exceedences of SCTL’s for commercial/industrial use requires landfill
disposal. Additional testing in Phase II may help to localize the contamination
and reduce the volume of material that has to be landfilled.
Transport
Dredged material to be transported to an FDEP approved landfill in lined
trucks.
Landfill Costs
Disposal fee based upon quote from a private Class I facility in Bartow, FL.
Dredging Type
Mechanical dredging with handling and dewatering on open area of the
Scottish Rite Temple Association site. Mechanical dredging assumed because
of limitations of space and need to maintain the dredged material as dry as
practical for handling and disposal.
Contingency
20% allowance as is typical for a 30% stage of design development cost
estimate.
Table 10b. Cost category assumptions
ASSUMPTION
DISCUSSION
Field Data Collection
Surveys
Recent surveys will be required to support design and permit applications.
The sediment and water quality sampling programs include six sampling
locations in an effort to spatially define the limits of PAH contamination.
The additional effort may help to reduce the overall project cost by isolating
materials containing arsenic and PAH contamination, thereby reducing the
amount of dredged material planned for landfill disposal. Laboratory
evaluation parameters are based upon FDEP regulations for sediment
(Chapter 62-777, F.A.C.) and water quality (62-302, F.A.C.).
Regulatory Permits
Applications
Completing and submitting joint applications with FDEP/USACE and
Hillsborough Co Environmental Protection Commission and Tampa Port
Authority. This includes pre-application conference, application preparation,
two rounds of responses to requests for additional information, and public
noticing.
Engineering Design
Feasibility study
The current feasibility study that is the subject of this report. Under the
provisions of the Canal Dredging Program Manual/MSBU ordinance, Phase
I study costs are included in the overall project cost if the community accepts
the project.
Final Design
Development of the construction documents (plans and specifications for the
project) based upon the accepted 30% design.
Construction
Support
Limited support for the contract bidding process, assistance with bid
selection, construction observations and final certification to regulatory
agencies.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 19
Construction
Project
Organization and
Control
Contractor costs including required surveys and implementation of best
management practices to control spills and stormwater drainage on the site.
Handling and
Transfer Area
Site preparation – development of a dredge material management area
(DMMA) (construction barrier type dike) to receive the dredged material, and
control drainage.
Area use fee – proposed conceptual temporary rental of the 2.8 acres of open
area on the Scottish Rite Temple Association property.
Site restoration – site cleanup, light grading and re-vegetation of spoil
handling area.
Site security – temporary fencing to limit access to construction area.
Dredging and
Dewatering
Dredging - dredging by barge mounted mechanical dredge with additional
barge(s) to receive and shuttle to shore for transfer of the dredged material to
the DMMA.
Debris removal – contingency allowance to provide for the removal of large
debris that cannot be normally handled by the mechanical dredge.
Dewatering – reworking of dredged material to promote drainage and drying.
Landfill disposal – cost of disposal of the dredged material to a Class I landfill
as required by PAH levels that exceed SCTL’s for commercial/industrial
usage. If additional sediment testing (field data collection) from Phase II can
show that the PAH contaminated sediments are localized, then some of the
dredged material will be considered for beneficial re-use, which could result
in lower unit costs.
Severance fees – The state of Florida applies a fee for use of sediment
removed from sovereign submerged lands. The fee is waived if the material is
applied to a public use project or if it is considered to be contaminated.
Transportation – truck transport from the DMMA to the FDEP approved
landfill.
Dredged Material Testing
Dredged Material testing – FDEP will likely
require testing of individual
batches (estimated 500 cy) of dewatered dredged material before being
transported from the DMMA to the final disposal site.
Elutriate Testing – FDEP indicated during the pre-application discussions
that testing of the drainage water from the DMMA will not be required
before its release into Sweetwater Creek. This item is a contingency allowance
in the event that testing is required.
Sediment/water quality report – a synthesis report of the dredged material
and water testing program will be required for submission to the regulatory
agencies.
Environmental Monitoring
Periodic sampling of water to verify that the dredging operations are not
exceeding permitted turbidity levels, as well as the staffing of the project with
manatee observers will be required as conditions to the regulatory permits.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 20
6. Regulatory Coordination
6.1
Agency Authorizations and Permit Requirements
A synopsis of agency permit requirements and project thresholds associated with the Sweetwater
Creek CDIU are described below. Permits will be obtained for the Sweetwater Creek CDIU from
the appropriate regulatory agencies as determined by specific project variables (e.g., maintenance
dredging, volume of dredge material.
Tampa Port Authority
Prior to 1995, the FDEP had state jurisdiction over submerged lands within Hillsborough County.
In 1995 the Florida Legislature drafted requirements and granted delegation of the management and
regulation of all submerged lands within the Hillsborough County Port District to the Tampa Port
Authority (TPA). The TPA and its jurisdiction was officially created pursuant to Special Act Chapter
95-488, Laws of Florida (House Bill No. 1291), called the “TPA Special Act” and became the
governing body and regulatory authority of public and private activities on Sovereignty Lands in
Hillsborough County. Through this Act, the TPA gained permitting authority over the filling,
dredging, development and construction of submerged lands located within the jurisdictional waters
of Hillsborough County.
The TPA Submerged Lands Management Rules (SLMR) provides for authorization as Consent By
Rule under Section II (A) 1 (j), for "maintenance dredging of existing channels…which were either
previously permitted by the Authority, Federal government, or State government, or constructed
prior to July 1, 1967, provided that the dredging does not exceed original permitted depth and
width”. In order to qualify as a maintenance dredging project, there must be clear evidence of
previous dredging, which may be achieved by obtaining copies of past permit authorizations for
dredging projects or by reviewing historic aerials. Review of a 1938 aerial of the Sweetwater Creek
CDIU (Dana Shores) shows that the historic shoreline has been substantially modified compared to
the 2006 shoreline (Figure 4). The change in shoreline width and channel location confirms that
Sweetwater Creek has been historically dredged and justifies the CDIU as a maintenance dredging
project.
Pursuant to Section II (A) 5(c), Management Agreement, if a delegation of authority exists from
TPA to any local, state, or federal governmental agency, for the administration and enforcement of
the Consent provisions then authority falls to this delegation rule. An Amended and Restated
Interlocal Agreement (Interlocal Agreement) between TPA and the Environmental Protection
Commission (EPC) was executed on June 23, 2009 to provide delegation of permitting and
regulatory authority for certain Minor Work Permits to the Hillsborough County EPC. The EPC is a
local government environmental agency created by Special Act Chapter 84-446, Laws of Florida
(Hillsborough County Environmental Protection Act), which authorizes the implementation of
various environmental rules and regulations.
A Standard (Major) Work Permit is required from TPA for all projects that are requesting to dredge
and fill more than 10,000 cubic yards, do not qualify as maintenance dredging, or are expected to
have significant environmental or hydrologic impacts. Pursuant to TPA SLMR Section V(A)3(g)2,
“New dredging to achieve navigable water depths or provide access to or flushing of waterbodies
dredged from private uplands shall not be approved unless: (a) There will be no significant and
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 21
Figure 4. 1938 Aerial photograph of the Sweetwater Creek CDIU project area and 2006 shoreline
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 22
unmitigated adverse impact to submerged or shoreline resources as a direct or indirect result of the
dredging; and (b) The overall project would result in less impact to Sovereignty Lands than would
be caused by other allowable uses of the submerged lands within the applicant's riparian area.”
Hillsborough County Environmental Protection Commission
Based upon the authority of EPC’s Wetlands Management Division and the Interlocal Agreement, a
Minor Work Permit is required for 1) “dredging or filling projects involving the removal from or
replacement on submerged lands of less than 1,000 cubic yards” or 2) “maintenance dredging of less
than 10,000 cubic yards of material from existing canals, channels, turning basins, or berths where
dredging is to be removed and deposited on self-contained upland sites”. As indicated above, if the
proposed dredge volume exceeds 10,000 cubic yards then the permit authority reverts back to TPA
as a Standard Permit, with EPC serving as a commenting agency. The Tampa Bay Estuary Program
is a commenting agency and will receive a copy of either the Minor or Standard Work Permit
applications.
Florida Department of Environmental Protection
As a maintenance dredging activity, the FDEP will review the project through a request for
exemption submitted in accordance with Chapter 40E-4.051(2)(a), F.A.C.
Since the FDEP
delegated authority of sovereign submerged lands to TPA, proprietary authorization is not required
to be issued by FDEP. Coordination with the Florida Fish and Wildlife Conservation Commission
will be conducted by the FDEP for guidance on avoidance and minimization measures relating to
the West Indian manatee (Trichechus manatus).
United States Army Corps of Engineers:
The US Army Corps of Engineers (USACE) authorization would be issued through delegation of
authority to the FDEP under the State Programmatic General Permit (SPGP). Therefore, FDEPs
issuance of an exemption letter will include the USACEs authorization. Consultation with the US
Fish and Wildlife Service (FWS) and/or the National Oceanic and Atmospheric Administration
(NOAA) may be required under Section 7 of the Endangered Species Act for project effect
determinations threatened and endangered species (e.g., T. manatus).
Formal permitting applications will need to be submitted to the TPA and/or the EPA depending on
the final dredge volume. In order for the regulatory agencies to complete their review of the permit
application and to render a final permit decision, it is likely that information such as, but not limited
to, the following will likely be required:
 Bathymetric survey
 Water quality and sediment data
 Submerged aquatic resource survey
 Emergent vegetation survey
 Threatened and endangered species survey
 Engineered drawings of plans and specifications
 Appropriate set backs
 Hydrodynamic evaluation or flushing study
 Spoil containment and disposal site
 Permit application fees
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 23
6.2 Natural Resource Considerations
6.2.1 Wetland Impacts
During an August 2010 meeting with the regulatory agencies, the concern for potential impact on
upstream marsh areas in Sweetwater Creek was identified. The question is whether the dredging will
change the slope of the water surface along the length of the creek to the extent that it could lead to
excessive drainage of the upland marsh areas. An analysis of the dredging effects on the stream slope
was conducted and is described in detail in Appendix V.
The analysis shows that the water surface elevation at the upper end of the dredging area (Memorial
Highway Bridge) will drop slightly (0.75 in) after dredging compared to pre-dredging conditions.
Within a short distance upstream of the Bridge, the change in the water surface elevation becomes
vanishingly small. As a result, no changes in water levels due to dredging are anticipated to occur in
the upstream marsh areas.
7. Assessments
7.1
Benefits Analysis
As part of the Hillsborough County Canal Dredging MSBU Program, Fishkind & Associates
developed a Master Assessment Methodology as a means to determine the benefits of a canal
dredging project and to equitably proportion its costs among the individual properties that receive
these benefits. The Master Assessment Methodology was accepted by the BOCC on April 20, 2011.
Appendix VI outlines the features of the assessment methodology and its application to the
Sweetwater Creek CDIU.
In allocating the amount of special assessments to benefiting property, Florida governments have
used a variety of methods including, but not limited to: property footage, parcel area, trip rates (e.g.,
roadway projects), equivalent residential units, dwelling units, acreage, and property value. Those
methods directly relating to a dredging project were identified, and include:

access to the dredged area
 potential use and navigation of the dredged area

rear lot length

existing permitted and unpermitted boat docks
 boat ramps
All of the benefits from the County’s dredging project are equitably allocated to benefiting
properties based on an equivalent canal dredging unit (ECDU). The Ordinance defines an ECDU as
the apportionment unit or criteria utilized to determine the Assessment for each parcel of property,
as set forth in the Initial Assessment Resolution. Appendix VI provides full details of the
development of the ECDUs and their assignment to individual properties.
7.2
Total Project Cost Estimate
The total project cost estimate consists of the capital costs of construction of the project and the
costs of financing the project. Section 5 of this report outlines the design considerations of the
proposed dredging project and estimates the cost of implementing the project at $1,037,199 (Table
9). The financing requirement costs are outlined in Section 2.2 of Appendix VI, and total $381,023.
The total project cost estimate is therefore $1,418,222.
Hillsborough County MSBU – Sweetwater Creek
Phase II Feasibility Report
Page 24
7.3
Specific Assessment Estimate
The Sweetwater Creek CDIU consists of 27 properties, including three commercial properties
directly affected by the Canal Dredging Program. Once the parcel ECDUs were determined and
totaled for each parcel, then a total number of ECDUs was calculated for the Sweetwater Creek
CDIU. From there, each parcel’s ECDU total was divided by the total number of ECDUs in the
CDIU to obtain the parcel’s percentage of the total ECDUs. The total debt allocation for the
Sweetwater Creek CDIU is $1,418,222, and each parcel’s percentage of the total ECDUs is
multiplied against that total to determine each parcel’s allocation of total debt. Refer to Appendix
VI, Section 4.0). Table 11 below shows the ECDU calculations for all of the parcels located within
the Sweetwater Creek CDIU.
Table 11. ECDU Calculations and Subsequent Debt Allocation
SITE_ADDR
Dredge
Area
Rear Lot
Length
Boat
Dock
Boat
Ramp
Total
ECDUs
Percent of
Total ECDUs
Total Debt
Allocation
Annual over
10 Years
4050 DANA SHORES DR
2
5
4
0
11
4.825%
$68,422.99
$6,842.30
4153 SALTWATER BV
2
5
4
0
11
4.825%
$68,422.99
$6,842.30
4155 SALTWATER BV
2
3
4
0
9
3.947%
$55,982.45
$5,598.24
4157 SALTWATER BV
2
3
4
0
9
3.947%
$55,982.45
$5,598.24
4159 SALTWATER BV
2
5
5
0
12
5.263%
$74,643.26
$7,464.33
4161 SALTWATER BV
2
4
3
0
9
3.947%
$55,982.45
$5,598.24
4163 SALTWATER BV
2
3
3
0
8
3.509%
$49,762.18
$4,976.22
4165 SALTWATER BV
2
3
3
0
8
3.509%
$49,762.18
$4,976.22
4167 SALTWATER BV
2
3
3
0
8
3.509%
$49,762.18
$4,976.22
4169 SALTWATER BV
2
3
5
0
10
4.386%
$62,202.72
$6,220.27
4171 SALTWATER BV
2
2
0
0
4
1.754%
$24,881.09
$2,488.11
4173 SALTWATER BV
2
2
3
0
7
3.070%
$43,541.90
$4,354.19
4201 SALTWATER BV
2
2
4
0
8
3.509%
$49,762.18
$4,976.22
4203 SALTWATER BV
2
3
3
0
8
3.509%
$49,762.18
$4,976.22
4205 SALTWATER BV
2
3
2
0
7
3.070%
$43,541.90
$4,354.19
4207 SALTWATER BV
2
3
3
0
8
3.509%
$49,762.18
$4,976.22
4209 SALTWATER BV
2
3
4
0
9
3.947%
$55,982.45
$5,598.24
4211 SALTWATER BV
2
3
3
0
8
3.509%
$49,762.18
$4,976.22
4213 SALTWATER BV
2
4
3
0
9
3.947%
$55,982.45
$5,598.24
4215 SALTWATER BV
2
4
3
0
9
3.947%
$55,982.45
$5,598.24
4217 SALTWATER BV
2
5
3
0
10
4.386%
$62,202.72
$6,220.27
4219 SALTWATER BV
2
1
0
0
3
1.316%
$18,660.82
$1,866.08
4307 SALTWATER BV