17-Attachment C - Project Background Report.pdf

Town N’ Country Regional

Drainage Improvement Project

Project Background Report

Hillsborough County

September 2024

Project Description The Town N’ Country community experiences significant and frequent flooding when rainfall events cause the Henry Street Canal to overtop its banks providing roadway and structure flooding.

To alleviate existing flooding within Town N’ Country, drainage and water quality improvements for the area north and south of Hillsborough Ave between Hoover Blvd and Hanley Road, in Hillsborough County are proposed. Project design will include large-scale stormwater conveyance improvements, attenuation improvements, habitat restoration, and inclusion of Green Infrastructure. The project area and contributing watersheds are shown in Figure 1 (adapted from Figure 1-1, Atkins 2023). The resulting project will reduce flood elevations and flooding duration throughout the project area, will improve water quality, will provide habitat restoration utilizing an environmentally sensitive design, which is supported by the community and key project stakeholders. The previously completed Project Development and Environment Study was performed by Atkins in 2023, this study documents information necessary for the County to reach a decision on the feasibility, location and conceptual design that will meet the goals of the project. The preferred conceptual design solution identified in the Atkins 2023 PD&E has subsequently been modified based on additional available data. Atkins staff is currently working on a conceptual permitting effort to support obtaining a Southwest Florida Water Management District (SWFWMD) conceptual Environmental Resource

Permit (ERP). This narrative presents the latest conceptual project information that may be utilized to aid in procurement of design services.

Figure 1 Project Area and Contributing Watersheds

Source: Atkins 2023

Project Objectives The purpose of the project is to provide flood reductions for roadways and structures in the Town N’ Country area (north and south of Hillsborough Ave. between Hoover Blvd. and Hanley Rd.) which falls within the

Sweetwater Creek (SWC) /Lower Sweetwater Creek (LSWC) Watershed. During storm events the Henry

Street Canal exceeds its banks and floods adjacent properties and roads, including Clifton Street, Hillsborough Avenue, Golden Drive, and George Road. In addition to providing flood protection the final design solution should incorporate Green Infrastructure, Habitat Improvement, Water Quality improvements and Resiliency to provide a holistic Regional improvement project which benefits the community and stakeholders. Opportunities to provide Green Infrastructure, Habitat Improvement, Water Quality improvements and Resiliency shall be considered for each of the subprojects (phases) that comprise the project. Identification of potential grant funding opportunities for design and construction activities should considered as part of this effort.

The LSWC watershed stormwater system covers an area of approximately ten square miles and consists of a network of interconnected modified natural creeks, ponds, depressional areas, urban wetlands/parks, artificial channels/canals, ditches/swales, and structures (pipes/culverts). The urban stormwater system has been engineered over the past decades to accommodate rapid development and subsequent flooding.

Although modifications to alleviate flooding have been made to the natural creeks the Town N’ Country area still experiences significant flooding during storm events. A PD& E was performed to evaluate large-scale stormwater conveyance and/or attenuation improvements, including drainage pipe/conduit and box culvert installations, channel improvements/expansions, and dredging. Based on the preliminary concepts developed in the PD&E, Alternative 14 (which is shown in Figure 2) was selected as the County’s preferred alternative. The modified Alternative 14 conceptual design is shown in Figure 3. The Consultant will be responsible for evaluating, optimizing and developing an engineering design based on conceptual Alternative

14 from the aforementioned PD&E study (Note: The preferred conceptual design solution identified in the

Atkins 2023 PD&E has subsequently been modified based on additional available data, the subsequent sections will provide additional subproject details inclusive of deviations from the PD&E Alternative 14 conceptual design).

Figure 2 Alternative 14 Schematic

Figure 3 Modified Alternative 14 Schematic

Conceptual Alternative 14 from the PD&E study consists of 4 subprojects and an FDOT subproject.

Development and optimization for the design of the 4 subprojects (not the FDOT subproject) shall be included in this work effort. Section 3.3 of the Atkins 2023 PD&E Study provides the following details for

Alternative 14: Key Features, Design Constraints, Supplemental Geotech Work, Benefits, Structural

Inundation & Roadway Level of Service Improvements, Cost Estimate and Expected Annual Damage &

Benefit Cost Analysis. The subsequent sections detail the requisite subprojects that comprise Alternative 14.

Subproject Phasing Professional engineering services are requested to complete the engineering design/ permitting for the phases or subprojects identified within conceptual Alternative 14 from the Town N’ Country / Hillsborough

Avenue Regional Drainage Improvements (PD&E) Report completed in 2023 by Atkins. Subproject phasing for design and construction is necessary to prevent adverse impacts throughout the Town & Country

Community. Design and construction will commence from the downstream extent of the project, working upstream. The Alternative 14 component project subprojects (phases) are shown in Figure 4A. The modified

Alternative 14 subprojects are shown in 4B.

Figure 4A Design and Construction Subprojects for Alternative 14

Figure 4B Design and Construction Subprojects for Modified Alternative 14

To meet the timeline for both the County and FDOT, permitting for the construction of all 5 phases should precede or coincide with the 60% design of the box culverts provided by FDOT. At a minimum, the County should obtain a permit for the dredging identified in Subproject 1 as early as possible in the process. Atkins is currently pursuing a conceptual design permit for the project.

Subproject 1- Proposed Dredging of Sweetwater Creek & Excavation of Sweetwater

Park Pond

Description

Subproject 1 of the design will focus on the required dredging in the LSWC main channel, extending approximately 1,275 feet south and 2,725 feet north of the channels crossing with Memorial Highway.

Additionally, this subproject includes excavation of a 2.5 acre pond within Sweetwater Park. The conceptual design schematic for subproject 1 dredging is shown in Figure 5A. The proposed dredging extents as well as the potential sediment dewatering locations are provided in Figure 5A. Removal of invasive species and creation of fish habitat should be provided where applicable throughout the proposed dredging extent.

Figure 5A Conceptual Design Schematic for Subproject 1

The proposed dredging activities are required to reduce tailwater conditions within the system which will mitigate the potential for upstream adverse flooding impacts. Design, permitting, and construction of this subproject should be the among the first aspects of the project to be initiated. All dredging work proposed in this subproject is anticipated to be contained within the existing limits of the channel, as such land acquisition should not be a factor for this subproject. Dredging activities shall be offset a sufficient distance from the mangrove dripline and seawalls to not impact the root zones of mangroves nor compromise the structural integrity of seawalls. Design shall include optimization of dredging extents based on additional hydraulic and hydrologic analysis. Specifically, to determine the sensitivity of the relative narrow point in the canal which occurs approximately 0.30 miles downstream of transect 9401020. To support the conceptual permitting effort Atkins performed a conceptual analysis of the proposed dredging extents which included bathymetric cross section data collection and review of the existing main channel creek profile. The LSWC transect locations developed by Atkins are shown in Figure 6B. Figure 6B provides a description of the source information for the transect data.

Figure 6B Atkins Developed LSWC Locations with Data Source

Source: Atkins 7/12/2023

The cross section locations, estimated mangrove dripline and seawall locations are shown in Figure 5C.

Figure 5C Cross Section, Dripline and Seawall Locations

Source: Atkins 7/26/2023

The proposed vs existing LSWC main channel profile is shown in 6.

Figure 6 Profile Comparison for LSWC Main Channel

Source: Atkins 7/12/2023

The existing vs proposed cross sections are shown in 7 through 2, the updated existing conditions were derived based on bathymetric survey provided by Atkins in 2023. The transect locations for these cross sections are shown in Figure 6B.

Figure 7 X-Section 9401285

Figure 8 X-Section 9401190

Figure 9 X-Section 9401160

Figure 10 X-Section 9401150

Figure 11 X-Section 9401075

Figure 12 X-Section 9401020

The proposed 2.5 acre pond within Sweetwater Park was not a part of the original Atkins PD&E study. Atkins determined through additional H&H modeling that the original Alternative 14 concept design provided local flooding adverse impacts. The aforementioned adverse impacts necessitated action to mitigate local increases in proposed flood stage. Excavation of the 2.5 acre pond and addition of corresponding conveyance to Sweetwater Creek helped to mitigate the adverse impacts. A conceptual design schematic of the proposed Sweetwater Park pond and additional Sweetwater Park improvements is shown in Figure 13A.

The proposed 2.5 acre pond will be excavated to provide flood attenuation. The pond shall be developed as an “amenity” for the Park with stabilized banks and walking paths (concrete or boardwalk) for pedestrians. A vehicle maintenance path shall be constructed to facilitate pond maintenance. Native littoral plantings within the pond should be implemented to promote habitat restoration and water quality improvement.

Connectivity will be provided from the Air Cargo Ditch to the proposed pond through culverts or a pedestrian bridge, additionally the proposed pond will be connected to Sweetwater Creek through culverts or a pedestrian bridge. The aforementioned connectivity is provided to provide flood attenuation.

Educational signage will be provided adjacent to the proposed pond to present the merits of habitat restoration and project flood protection. There are 2 potential locations for the proposed kayak/canoe launch, each of the potential locations is shown in Figure 13A. In order to move forward with the eastern kayak/canoe launch (near the Park entrance) widening of the existing east/west ditch would be required.

Utilization of the western kayak/canoe launch location would require construction of an improved access road (gravel or dirt) to provide ingress/egress to the proposed launch. This path would only be utilized for kayak/canoe pickup and drop off. Parking for either kayak/canoe launch location would remain unchanged from the current parking configuration. Implementation of either alternative will require restoration of an continuous deflective separation (CDS) unit that is not currently functional. Additional opportunities for utilization of technologies provided within the Hillsborough County Green Infrastructure Manual should be utilized within this subproject.

Figure 13A Conceptual Design for Sweetwater Park Improvements

Atkins created a schematic of the proposed pond which is shown in Figure 13B. The proposed pond is connected to Sweetwater Creek via culverts or pedestrian bridges. The proposed pond may provide water quality benefit through nutrient reduction.

Figure 13B Proposed 2.5 acre Pond within Sweetwater Park

Atkins 2024

Maintenance, Access, Permitting Considerations

Historically, dredging activities within the proposed subproject area were performed from a small boat in which the dredged material was pumped through hoses to trucks for disposal. Hillsborough County does not own contiguous Creek adjacent land throughout the entire proposed dredging extent, which precludes dredging from shore. Hillsborough County Parks and Recreations owns Sweetwater Park off Bray Road, a portion of the park land may be utilized to stage/ facilitate dewatering of sediment (this alternative has not yet been discussed with Parks and Recreation Staff). The Shriners property (vacant property) southeast of

Memorial Bridge may be a suitable location for dewatering activities. A sediment dredging boat may be utilized to accomplish the proposed dredging activities, however the proposed boat must have access to the

Creek and must be able to fit under Memorial Bridge. If the dredging boat is unable to clear Memorial Bridge alternative access must be planned and provided. The sediment must be tested to prevent hazardous waste characterization. Historical sediment analysis within Lower Sweetwater Creek did not identify hazardous sediment. The Port Authority has jurisdiction over the waters in the Creek, therefore procurement of the requisite permits is required to facilitate dredging activities.

Excavation of the 2.5 acre pond within the Sweetwater Park will require continued coordination with

Hillsborough County Parks and Recreation Staff. Parks and Recreation Staff have generally accepted the proposed 2.5 acre pond alternative within the Sweetwater Creek Park with the stipulation that a memorandum of understating (MOU) is accepted by both parties on an agreeable standard of maintenance for the proposed pond and that some additional programming be included to ensure the pond becomes an asset to the park.

Water Quality and Habitat Restoration

According to the 2004 Report titled “Nutrient TMDL for Lower Sweetwater Creek (WBID 1570A)” (FDEP 2004) the tidal reach was verified as impaired for dissolved oxygen (DO) and nutrients (total nitrogen).

Opportunities for water quality improvement and habitat restoration should be included within the subproject design. Bank stabilization through implementation of living shoreline and removal of invasive species (Brazilian Pepper Tree) should be considered for habitat restoration for Sweetwater County Park

Property and/or additional agreeable stakeholders. Scope should include provision for nutrient sediment analysis which shall aid in estimation of pollutant load reduction associated with removal of dredged material. Previous dredging activities did not accomplish sediment nutrient analysis. Potential mangrove planting or wetland planting activities for wetland credits on the western Sweetwater Park boundary shall be considered where wetland marsh area may be constructed. Potential grant funding opportunities for creation of fish habitat through NOAA should be explored.

Constructability Constraints and Challenges

The following list summarizes potential questions and challenges related to construction activities. These must be resolved in subproject 1 design.

Dredging activities may require landowners to be a co-permittee with the County.

Docks from adjacent property owners, impacts to cross sectional area, must stay 10 feet away from docks and seawalls, may restrict scope of dredging activities.

Public outreach to dredging adjacent dock owners.

Recommendations for future maintenance.

Scope Items

Subproject Design o Restoration of Conveyance Capacity and elimination of hydraulic restriction o Include opportunities within design for water quality improvement (sediment removal), resiliency, green infrastructure and habitat restoration (invasive species removal) o Small craft access (Access to facilitate maintenance) /Canoe ramp (Recreation) o Coordination of the requisite permitting efforts, obtain requisite permits o Identify applicable grants o Solid Waste Characterization (assess for toxicity & nutrients) for dredged and excavated material o Identification of sediment disposal location o Provide support for public outreach

Subproject 2- Proposed Channel Improvements

Description

Subproject 2 (shown in Figure 4A) of the design will focus on the design and permitting of the proposed channel improvements to both the LSWC main channel north of Berkley Prep and the improvements to the

TIA Air Cargo Ditch leading up to Bray Road through Sweetwater Park. Channel improvements shall entail removal of sediment, excessive vegetation, brush and invasive vegetation. Additional improvements include construction of a proposed maintenance berm, bank stabilization and erosion control. Creek adjacent land acquisition may be required to implement construction of the proposed maintenance berm. Land acquisition of the area currently occupied by the tennis court (Figure 14A) may facilitate restoration of the historical

Creek flow path and may provide water quality improvement opportunities. The proposed channel cross sections are shown in Figure 14B and the channel cross section locations are shown in Figure 14C.

Figure 14A Conceptual Design for Subproject 2

Figure 14B Proposed Cross Sections for Subproject 2

Figure 14C Proposed Cross Section Transects for Subproject 2

Bank stabilization strategies such as utilization of filtrex socks (for bank support), earth banks and gabions may be considered for bank stabilization. Consideration should be given to acquire additional creek adjacent land to provide storage and/or habitat restoration. Easements along the TIA Air Cargo Ditch from Berkley prep

(Figure 7) and the LSWC main channel (Figure 8) would need to be obtained during the design of this subproject.

Comparison of historic 1938 (Figure 9) and 2020 (Figure 18) aerial imagery shows the historical Sweetwater

Creek path flows through the location of an existing tennis court. Land acquisition may afford the opportunity to restore historical Sweetwater Creek flow path.

Figure 7 Proposed Project Land Acquisition near Bray Road

Figure 8 Proposed Project Land Acquisition near W Hillsborough Ave

Figure 9 1938 Aerial Imagery of Sweetwater Creek

Figure 10 2020 Aerial Imagery of Sweetwater Creek

Previous dredging and or channel improvements and maintenance activities have not been provided within the proposed subproject extent, mainly because the County lacks an existing drainage easement over this portion of Sweetwater Creek.

Procurement of a drainage easement or land acquisition would be required to support sustainable operation and maintenance. The County does not provide (under non-emergency conditions) maintenance for private property areas without an easement. County staff met with representatives from the Korean Presbyterian

Church of Tampa and Berkeley Preparatory School in 2023 to discuss the feasibility of obtaining drainage easements within the proposed Subproject 2 footprint. Conversation with the aforementioned stakeholders was generally positive with acceptance of the proposed preliminary design concept. Berkeley Preparatory

School did mention the need to coordinate proposed construction activities around times of diminished campus activities (less students in the summer).

Depending on the interpretation of wetland impacts, permitting agencies may require wetland mitigation.

Proposed channel improvements should not reduce the flow capacity of the channel or provide upgradient or downgradient adverse impacts. Scope item should be added for sediment toxicity characterization, to test excavated sediment to confirm non-toxic sediment. The proposed design should provide an aesthetic improvement to restore natural channel characteristics. Identification of annual and periodic maintenance activities should be included in this effort.

Water Quality and Habitat Restoration

Bank stabilization through implementation of living shoreline and removal of invasive species (Brazilian

Pepper Tree) should be considered for habitat restoration for Sweetwater Creek. Scope should include provision for bank stabilization strategies. Potential grant funding opportunities for creation of fish habitat through NOAA should be explored.

Constructability Constraints and Challenges

The following list summarizes potential questions and challenges related to construction activities. These must be resolved in subproject 2 design.

Sediment removal activities may require easement and or land acquisition.

Provision of an optimal Creek side slope may be difficult given potential wetland impacts, land availability.

Recommendations for future maintenance.

Scope Items

Design o Include opportunities within design for water quality improvement, resiliency, green infrastructure and habitat restoration (removal of invasive species & bank stabilization) o Sediment removal o Coordination of the requisite permits efforts, obtain requisite permits o Identify applicable grants o Solid Waste Characterization for dredged and excavated material o Identification of sediment disposal location

Subproject 3- Proposed Channel Improvements, Culvert Replacements and New

Channel

Description

A conceptual design schematic of Subproject 3 is shown in Figure 19A. Subproject 3 consists of designing the bypass channel from George Road to the TIA Air Cargo Ditch and includes improvements to existing channels, crossings and construction of an additional concrete box culvert that will provide conveyance from the North/South bypass channel to the TIA Air Cargo Ditch. Additional details for the proposed

“Channel Improvements” shown in Figure 19A are illustrated in Figure 19B and Figure 19C. The channel stations and corresponding proposed channel improvement cross sections are shown in Figure 19B and

Figure 19C.

Figure 11A Conceptual Design Schematic for Subproject 3

Figure 12B Conceptual Channel Improvements for Subproject 3- Channel Stationing

Figure 13C Conceptual Channel Improvements for Subproject 3- Cross Sections

The North/South bypass channel provided in Figure 19A differs from the North/South bypass alternative provided in the PD&E. The PD&E suggested utilization of land underlying or adjacent to El Capitan Drive, this was not possible because of proposed development by affordable housing. Instead, the proposed route shown in Figure 11A will provide the requisite north/south conveyance. The following discussion regarding the north/ south conveyance between Bonita Vista Drive and Alvarado Drive was not included in the PD&E study.

Atkins met with County staff in a series of meetings to review several potential cost-effective conveyance configurations for the North/ South route between Bonita Vista Drive and Alvarado Drive. Initial consideration was given to the conveyance configurations in Figure 14, Figure 15 and Figure 16. The conveyance shown in

Figure 14 was initially evaluated as an alternative to the channel along El Capitan Drive (PD&E). Utilization of the Figure 14 infrastructure showed comparable model results to Alternative 14 of the PD&E study and provided a maximum flow rate near 620 cubic feet per second (cfs) for the 100yr-24hr storm event.

Figure 14 Option 1 from 8/09/2023 Atkins Meeting, North/ South route between Bonita Vista Drive and Alvarado Drive

Atkins 2023- 8/09/2023

The configuration shown in Figure 15 consists of a single (1) 4’x12’ box culvert, dual (2) 72” pipes and an overlying swale. A 10-foot-wide access berm is provided on one (1) side with the swale having a side-slope of

3:1. The intent of this option was to utilize cheaper round pipes within the swale banks in lieu of the more costly box culverts. The maximum flow rate for this conveyance configuration is not sufficient to convey the requisite volume of stormwater runoff, therefore precluding concept feasibility. Modeled peak stage reductions for Option 2 were less than the Option 1. Based on the relatively low flood reduction further evaluation of Option 2 would not be pursued.

Figure 15 Option 2 from 8/09/2023 Atkins Meeting, North/ South route between Bonita Vista Drive and Alvarado Drive

Option 3 shown in Figure 16 consisted of dual (2) 6’x10’ box culverts, situated close to the right-of-way (R/W) line, with a deeper channel running in between. This option would accommodate a 10-foot-wide maintenance berm on either side of the channel and would provide more conveyance area compared to the second option. However, a 2:1 side-slope would have to be implemented to maximize the flow-area. The modeled maximum flow-rate would not be sufficient to get comparable results to that of Option 1.

Figure 16 Option 3 from 8/09/2023 Atkins Meeting, North/ South route between Bonita Vista Drive and Alvarado Drive

The fourth configuration presented in the 8/09/2023 meeting is shown in Figure 17, which was not yet modeled. This option consists of dual (2) 6’x10’ box culverts that would be situated approximately 16 to 18 feet apart from one another. The intent would be to utilize the space between the culverts as a rectangular channel with the box culvert sides acting as vertical walls. The bottom of the rectangular channel would be comprised of natural ground. Rip-rap would be installed at the bottom edges of the culverts to mitigate potential undermining. In addition, a 15- to 16-foot-wide maintenance berm would be provided on either side of the channel to facilitate maintenance needs. Subsequent meetings would provide continued analysis of this configuration. Based on the 8/09/2023 meeting options 2 & 3 are not preferable. Further evaluation of

Option 1, Other Option and an additional option utilizing gabion baskets was requested.

Figure 17 Additional Option from 8/09/2023 Atkins Meeting, North/ South route between Bonita Vista Drive and Alvarado Drive

The configurations shown in Figure 18, Figure 19 and Figure 20 were discussed during the 08/23/2023 meeting involving Hillsborough County Stormwater Staff and Atkins Staff. The conveyance shown in Figure 18 was initially evaluated as an alternative to the channel along El Capitan Drive (PD&E). Utilization of the Figure

18 infrastructure showed comparable model results to Alternative 14 of the PD&E study and provided a maximum flow rate near 600 cubic feet per second (cfs) for the 100yr-24hr storm event.

Figure 18 Option 1 from 8/23/2023 Atkins Meeting, North/ South route between Bonita Vista Drive and Alvarado Drive

Atkins 2023- 8/23/2023

Option 2 shown in Figure 19 was revised to include dual (2) 10’x6’ box culverts with a 16-foot-wide rectangular channel in between. Rip-rap would be installed at the bottom edges of the culverts to mitigate potential undermining. Additionally, 16-foot-wide maintenance/access berms are provided on either side of the channel with side slopes of 8:1. The updated section provides favorable model results and exceeds the conveyance capacity of Option 1.

Figure 19 Option 2 from 8/23/2023 Atkins Meeting, North/ South route between Bonita Vista Drive and Alvarado Drive

Updated Option 3 shown in Figure 20, now consists of gabion baskets that are slightly staggered towards the

R/W line. This creates a 23-foot-wide open channel with a 15-foot-wide maintenance/access berm on one (1) side. The other side consists of a smaller 8-foot-wide section to allow tie-down to the existing grade along the

R/W. Maximum flow rate for option 3 is less than Options 1 & 2. Further refinement of Option 3 to provide increased capacity would be discussed at the following meeting.

Figure 20 Option 3 from 8/23/2023 Atkins Meeting, North/ South route between Bonita Vista Drive and Alvarado Drive

The 9/06/2023 meeting with Hillsborough County and Atkins Staff incorporated model refinements and updated conveyance cross sections for consideration. The model refinements necessitated modification of historical Option 1 (Figure 18). The triple (3) box culverts had to be increased in size from 10’ x 6’ to 12’ x 6’ to obtain comparable results. The updated Option 1 configuration is shown in Figure 21. No additional changes were made to Option 2 shown in Figure 19.

Figure 21 Updated Option 1 Conveyance Configuration

Atkins 2023- 9/6/2023

Option 3 which previously included gabion baskets and an open channel was expanded per the prior discussion to obtain comparable results to Options 1 and 2. The updated Option 3 cross section is shown in

Figure 22. An additional single (1) 42” culvert is required under the maintenance/access berm to provide increased conveyance. The modified Option 3 does not provide results comparable with Options 1 & 2.

Installation of the proposed 42” pipe adjacent to the gabion baskets and R/W may not be feasible from a construction standpoint.

Figure 22 Updated Option 1 Conveyance Configuration

Atkins 2023- 9/6/2023

Atkins generated preliminary planning level costs for each option: Option 1- $15M, Option 2- $12M and

Option 3- $6M. Maintenance for Option 2 will be more complicated, but the capital cost for Option 2 is less expensive than Option 1 while providing comparable results. Option 3 is the most inexpensive but does not have the requisite conveyance performance. The County’s preferred section for the new alignment is Option

2.

Maintenance, Access, Permitting Considerations

The entry point for maintenance vehicles (i.e., Menzi excavator) would need to be provided to access a rectangular channel. The steepest allowable side-slope for maintenance access berm is 8:1.

Implementation of gabion baskets may provide maintenance difficulties through their service life making utilization less desirable. An easement from the Korean Presbyterian Church of Tampa will need to be obtained prior to this phase to complete the connection between the bypass channel and the TIA Air Cargo

Ditch.

Water Quality and Habitat Restoration

Potential habitat restoration and water quality improvement maybe realized through inclusion of pretreatment (trash racks & screens), utilization of vegetated filter strips, wet detention/ bioretention/ constructed wetland/ permeable pavement and tree preservation. Examples of potential BMPs for subproject 3 are shown in Figure 23 and Figure 24. Design should provide for water quality and habitat improvement opportunities.

Figure 23 Potential Water Quality and Habitat Improvement BMPs North

*Note Weirs maybe added to the proposed channels for Water Quality Improvement

Figure 24 Potential Water Quality and Habitat Improvement BMPs South

*Note Weirs maybe added to the proposed channels for Water Quality Improvement

Constructability Constraints and Challenges

Regarding Option 3 utilization of sheet pile to provide a vertical wall solution may provide additional cross sectional flow area, however sheet pile installation may provide excessive vibration which may adversely impact adjacent residential structures.

Scope Items

Conveyance Improvement o Include opportunities within design for water quality improvement, resiliency, green infrastructure and habitat restoration o Coordination of the requisite permits efforts, obtain requisite permits o Maintenance plan for habitat restoration o Identify applicable grants o Utilities- SUE o Provide support for public outreach

Subproject 4- Proposed Box Culvert (B/w Henry Street Canal & Bypass Canal)

Description

Subproject 4 (Figure 31) would include the final design of the box culverts extending approximately 2,575 linear feet between the Henry Street Canal to the connection point with the bypass canal designed under

Subproject 3. The alignment of the culvert will need to be finalized in coordination with the design of the culverts discussed in the FDOT phase of the project. As proposed, corner clips along George Road at the connection point to the Henry Street Canal (Figure 3-42 -PD&E) and at the George Road/Hillsborough

Avenue (Figure 3-43 -PD&E) may be required but that will be dependent on the final alignment determined during this subproject. Alternatively, these easements could be obtained during Subproject 2 of the design.

Figure 31 Conceptual Design Schematic for Subproject 4

Requisite maintenance activities would be a challenge given the length, size and slope of the proposed culvert. Additionally, the proposed culverts proximity to the Gulf of Mexico and potentially low flow invert elevation may provide a sump condition which may hinder maintenance activities.

Water Quality and Habitat Restoration

Potential for implementation of trash racks at the culvert entrance may reduce downgradient trash.

Constructability Constraints and Challenges

This portion of the Town N’ Country community contains a significant amount of utilities which may require relocation.

Scope Items

Conveyance Improvement- George Road o Include opportunities within design for water quality improvement o Coordination of the requisite permits efforts, obtain requisite permits o Identify applicable grants o Utilities- SUE o Coordinate Design with FDOT

FDOT Subproject

Description

The FDOT subproject (Figure 31) includes the design and construction of two crossings within FDOT’s ROW.

The first crossing extends west from Golden Drive before crossing beneath Hillsborough Avenue to connect the existing inlet west of Daniels Road with the existing channel on the south side of Hillsborough Avenue, just west of Archstone Drive. The second crossing is located within the intersection of Hillsborough Avenue and George Road. FDOT has since initiated the design of these two crossings under FPID 445674 - Daniels

Road and FPID 445677 - George Road, with respective letting dates of August and December 2024 as of the completion of the Atkins PD&E. Extensive coordination will need to occur between the EOR of these projects and the design consultant for the County’s overall project, especially when considering the design of the culverts in Subproject 4. Both improvements, if completed before the design and construction of the downstream improvements are completed, will need to ensure that they will not result in any adverse impacts independent of the remaining project. This may require the use of temporary restrictor plates before they can be put into operation.

Request for Qualifications

The following is illustrative, but not all inclusive of, the types of engineering activities contemplated under this contract:

Design

Prepare plans, technical specifications, and cost estimates

Provide support for public outreach

Create/Review and respond to review comments at 60%, 90%, 100%, and final design

Permitting

Florida Department of Environmental Regulation

Wastewater Relocation - 62-604.300(8)(a), 62-604.300(8)(b)

Notification / Application for Constructing a Domestic Wastewater Collection / Transmission System

Notification of Completion of Construction for a Domestic Wastewater Collection / Transmission

System

Water Relocation - 62-555.900(1), 62-555.900(9)

Application for a Specific Permit to Construct PWS Components

Certification of Construction Completion and Request for Clearance to Place Permitting PWS

Components into Operation

Southwest Florida Water Management District

Environmental Resource Permit - 62-330.054

Individual and Conceptual Approval Environmental Resource Permit

United States Army Corps of Engineers

Dredging - 33 CFR Part 330

Nationwide Permit #3

Florida Department of Transportation

Drainage Connection Permit - RULE 14-86.004, F.A.C.

Connection to FDOT facilities

Port Tampa Bay

Dredging - Minor Work Permit if <10,000 CY or Standard Work Permit if >10,000 CY

Standard Work Permit

Hillsborough County Environmental Protection Commission

Dredging - Minor Work Permit if <10,000 CY or Standard Work Permit if >10,000 CY

EPC Minor Work

Hillsborough Development Services Department

The Consultant shall identify utility facilities and secure agreements, utility work schedules, and plans from the Utility Agency Owners (UAO) ensuring all conflicts that exist between utility facilities and the County’s construction project are addressed. The Consultant shall certify all utility negotiations have been completed and that arrangements have been made for utility work to be undertaken.

Summary of Key Design Considerations

Safety Components o Hillsborough County’s Policy Adoption of Vision Zero

Utility coordination and design, including impacts to existing utilities, need to relocate, and new proposed facilities o City of Tampa and Hillsborough County Sewer and Wastewater infrastructure o Verizon Communications Vault along Hillsborough Ave o Identify Potential Key Utility Conflicts

Public outreach and stakeholder coordination o Inter-local agreement with FDOT

Design shall utilize Green Infrastructure, provide Habitat Restoration/ Improvements, provide water quality improvements, promote Resiliency

Challenges and Opportunities o Major Stakeholders coordination o Environmental impact o Coordination with FDOT for construction of 5’x12’ box culverts in FDOT right-of-way on

Hillsborough Avenue and at intersection of George Road and Hillsborough Avenue o Conveyance improvements limited by the dimensions of the existing Canal C right-of-way.

Design Exception may be required for design slopes not meeting current County specifications o Coordination with County Parks Department for Pond at Sweetwater Park o Dredging of the spoil material will need to be completed prior to or concurrent with the first subproject of construction, extensive permitting may be required and should be initiated as early as possible in the design phase

Land Acquisition o Corner Clips at intersection of George Road and Hillsborough Avenue o Easements along LSWC between Hillsborough and Berkley Prep o Berkley Prep o Korean Presbyterian Church of Tampa Bay o Bridgeview Apartments

Potential consultants should have prior similar project experience.

References

Atkins, October 3, 2023, Town N’ Country/ Hillsborough Avenue Regional Drainage Improvements- Design and Evaluation Technical Report Final.

Atkins, August 9, 2023, Town N’ Country Progress Meeting Presentation

Atkins, August 23, 2023, Town N’ Country Progress Meeting Presentation

Atkins, September 6, 2023, Town N’ Country Progress Meeting Presentation

Atkins, July 26, 2023, Town N’ Country Progress Meeting Presentation

Atkins, July 12, 2023, Town N’ Country Progress Meeting Presentation

FDEP, September 15, 2004, Nutrient TMDL for Lower Sweetwater Creek (WBID 1570A) 1 Introduction

(usf.edu)