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<p>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 <www.hillsborough.wateratlas.org>. 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 </p>
