BLACKBURN POINT BRIDGE PROJECT

Project Overview

The purpose of the project is to study possible replacement alternatives for the Blackburn Point Bridge on Blackburn Point Road over the Gulf Intracoastal Waterway in Osprey, Sarasota County, Florida. The project consists of two phases. Phase One involves a Project Development & Environment Study (PD&E), which includes environmental and engineering evaluations of alternatives. This phase will be conducted in coordination with the County, incorporating public feedback and establishing design criteria. Phase Two focuses on preparing design documents for the construction of the chosen alternative.

Historical Significance of the Bridge

The Blackburn Point Bridge, constructed between 1925 and 1926, is a notable structure located in Sarasota County, Florida. The construction of the Blackburn Point Bridge marked an important development in the infrastructure of Sarasota County during the early 20th century. This bridge has been recognized for its historical significance and is listed on both the National Register of Historic Places and the Sarasota County Register of Historic Places. As a swing bridge, it was designed to allow maritime traffic to pass through while also accommodating vehicular traffic. The bridge’s design and construction reflect the engineering practices of its time, showcasing both aesthetic and functional elements that were prevalent in early 20th-century bridge design. Sarasota County’s Parks, Recreation and Natural Resources as well as the Libraries and Historical Resources Departments will be assisting with honoring the bridge’s historical significance.

PROJECT ALTERNATIVES

The Blackburn Point Bridge project presents several alternatives for addressing the current infrastructure needs and ensuring safe passage. The options can be categorized into two primary approaches: a No-Build Option and various replacement strategies.

No-Build Option

The No-Build Option involves retaining the existing single-lane bridge while performing necessary repairs to maintain its operational status and structural integrity. The No-Build Option is a critical component of the National Environmental Policy Act (NEPA) process. The No-Build Option serves as a benchmark to compare the environmental impacts of proposed actions with a scenario where no action is taken. The No-Build Option is not just a placeholder but a required element that helps in evaluating the effects of a proposed project. By including a No-Build Alternative in the environmental assessment, agencies can better understand the potential environmental consequences of not proceeding with the project, which in turn, aids in making a more informed decision.

Replacement Options

Replacing the existing bridge opens up opportunities to improve functionality, safety and mobility. Replacement options will consider two types of movable spans:

Swing Span Bridge – A swing span rotates horizontally about a vertical axis centered at a pivot point. Rotation swings one arm of the swing span clear of the navigational channel to allow vessels to pass. This type of bridge is advantageous in areas where vertical clearance is limited and the waterway is sufficiently wide to accommodate the swing mechanism and supporting pier. The existing bridge is an example of a swing span.

Bascule Span Bridge – A bascule span rotates about a horizontal axis, raising the forward section(s) and rotating the span(s) clear of the navigational channel to allow vessels to pass. This design is effective were space constraints exist such as urban environments and locations with narrow waterways. Bascule bridges are the most common type of movable bridge along Florida’s waterways. The bridges over the Intracoastal Waterway at Stickney Point and Albee Road are local examples of bascule bridges.

Swing Span Bridge

Bascule Span (Single-leaf)

Bascule Span (Double-leaf)

Currently, the bridge offers horizontal and vertical clearances of 51 feet and 9.3 feet, respectively. These measurements fall short of the United States Coast Guard’s (USCG) recommended standards for the Gulf Intracoastal Waterway, which specify a minimum horizontal clearance of 90 feet and a vertical clearance of 21 feet. This discrepancy poses an unreasonable obstruction to navigation, potentially hindering maritime traffic and increasing risks for vessels operating in this area.

Horizontal Alignment Considerations

For both replacement options, there are considerations regarding horizontal alignment. One proposal includes shifting the alignment of the new bridge to the north. This shift could help minimize disruption during construction and improve traffic flow by aligning better with existing roadways. Another alternative involves maintaining the existing alignment while constructing a temporary bridge to the north during construction activities, thus ensuring continuous access for vehicles.

Vertical Clearance Requirements

Maintaining adequate vertical clearance is crucial for ensuring access to adjacent driveways and properties near the bridge site. Both replacement designs must account for this requirement to avoid disrupting local traffic patterns and accessibility.

CURRENT CONDITIONS AND FEATURES

Despite its historical value, the Blackburn Point Bridge has several substandard features that have led to its classification as functionally obsolete. One significant issue is its insufficient width, which does not meet modern traffic demands. This limitation poses safety concerns for vehicles navigating across the bridge.

Additionally, the bridge’s railings do not conform to current safety standards, further contributing to its classification as functionally obsolete. These railings are crucial for ensuring pedestrian safety and preventing accidents.

Another critical aspect of the Blackburn Point Bridge is its swing span superstructure and machinery, which are located within what is known as the splash zone. This area is prone to water exposure from waves and weather conditions, potentially leading to accelerated wear and corrosion of structural components. The placement of these mechanical systems in such a vulnerable location raises concerns about their long-term functionality and maintenance needs.

Another issue is the substandard clear roadway width, which accommodates only a single travel lane measuring 16 feet wide. This narrow configuration restricts traffic flow and increases the risk of accidents, especially given the bridge’s frequent use by both vehicles and non-motorized users.

Despite the high volume of daily pedestrian and bicycle traffic, the bridge lacks essential features such as shoulders, sidewalks, or dedicated bicycle lanes. This absence not only endangers pedestrians and cyclists but also contributes to an overall unsafe environment for all users. The lack of these facilities forces non-motorized users to share the limited roadway space with vehicles, heightening the potential for collisions and injuries.

Moreover, the Blackburn Point Bridge fails to meet the minimum lane and shoulder widths prescribed by the American Association of State Highway and Transportation Officials (AASHTO). AASHTO guidelines recommend specific dimensions to ensure safe passage for all types of road users. The failure to adhere to these standards further underscores the inadequacies of the bridge’s design and raises concerns about its ability to safely accommodate current traffic demands.

Images below show active corrosion on structural components of the bridge.

Evacuation and Safety Improvements

The Blackburn Point Bridge serves a critical role in emergency evacuations, particularly during storm events. It is located on Blackburn Point Road, which connects Casey Key to US 41 and is designated as an emergency evacuation route. This designation underscores the importance of the bridge in facilitating safe and efficient evacuations for residents and visitors alike.

However, the existing structure presents significant challenges during emergencies. One of the primary concerns is that there is insufficient room on the bridge to accommodate vehicles passing each other, especially if one vehicle becomes stalled. This limitation can create bottlenecks that hinder evacuation efforts when time is of the essence.

To address these issues, proposed improvements to the Blackburn Point Bridge aim to increase its width. By expanding the bridge, it will allow for adequate space for vehicles to pass around any stalled vehicles, thereby enhancing the overall efficiency of evacuation procedures during emergencies.

In addition to evacuation considerations, there are also important bicycle and pedestrian interactions that need to be addressed. Currently, the bridge lacks sidewalks that comply with accessibility requirements established by the Americans with Disabilities Act (ADA). This absence poses a safety risk for pedestrians who cross the bridge daily. Furthermore, there are no dedicated bicycle lanes on the bridge; instead, it features an open grid metal deck that can be hazardous for cyclists. The existing warning signs instructing cyclists to “Walk Bikes Across Bridge” highlight this concern but do not provide a long-term solution.

The proposed improvements will not only enhance vehicular traffic flow but will also significantly improve safety for pedestrians and cyclists. The plans include adding sidewalks and dedicated bicycle lanes along with replacing the open grid deck with a solid surface. These enhancements will ensure safer passage for all users of the bridge and align with current safety standards.

Marine Vulnerabilities

In addition to navigational concerns, the Blackburn Point Bridge exhibits several vulnerabilities related to marine safety and structural integrity:

Coastal Storm Protection: The existing structure does not meet current standards designed to protect against damage from coastal storm wave action. This lack of resilience raises concerns about the bridge’s ability to withstand severe weather events.

Collision Resistance: The swing bridge design is inadequate for sustaining direct collisions with vessels. Given the high traffic volume on the Gulf Intracoastal Waterway, this presents a significant risk not only to the bridge itself but also to maritime safety.

Corrosion Risks: The low members of the bridge are situated within the splash zone, exposing them to wave impacts during large coastal storms. Additionally, these components are susceptible to accelerated corrosion due to saltwater exposure and salt-laden air, further compromising their structural integrity over time.

Stakeholder Meetings

Blackburn Point Bridge Project Presentation May 2025

FAQs

Why is replacement-in-kind not being considered?

Replacement-in-kind would not address the needs for marine traffic, specifically the existing substandard channel width of 51-feet. The United States Coast Guard has indicated they will not approve a new bridge that does not meet their published horizontal guide clearance of 90-feet.

Why is rehabilitation not being considered?

Rehabilitation would retain the existing bridge geometry which does not meet the needs for safety or mobility.

What will the project cost?

The cost of the project will be a function of the alternative selected for design and construction. Initial cost estimates for each alternative will be presented at the Alternatives Workshop public meeting.

What happens after the PD&E phase?

Following selection of a preferred alternative the project will continue into a design phase to be followed by a construction phase. The timing and duration of these phases will be established based on the alternative and funding availability.

Is the project funded?

The project is funded for PD&E and Design. The project is not yet funded for construction as funding sources are being evaluated.

Will the bridge be closed during replacement? For how long?

Efforts will be made in design and construction planning to keep the existing road open to the extent practical. However, there will be short term closures of the road necessary to replace the existing bridge with a new bridge, even if a temporary bridge is included.

What will happen if the existing bridge fails?

The County’s emergency plan is to detour traffic to the Albee Road Bridge to the south. Beyond that, an emergency plan would be developed to address the specific cause of the failure.

Can we reduce the weight limit for vehicles using the bridge?

Analysis of the existing bridge indicates the structure is adequate to carry the current vehicles. Reducing the weight limit could limit typical garbage trucks, construction trucks, and most importantly EMS vehicles.

Does the project include adding bike lanes west across the Dryman Bay Bridge cost?

No. The project limits do not include the Dryman Bay Bridge or Blackburn Point Road west of the bridge.

What happens after the Public Hearing? How long will it take for a new bridge to be constructed?

Following the Public Hearing, the project will proceed with final design and permitting. The duration for final design, as well as for construction, are dependent upon the selected alternative. In general, final design is expected to take about one year and finish in the 3^rd quarter of 2027. Advertisement and award of a construction project is anticipated to take 3 to 6 months. Construction is estimated to take approximately 2 to 3 years with a finish date in 2030 or 2031.

The project schedule indicates a one-year duration between the alternatives workshop and the public hearing. Why so long?

A year is estimated to develop and analyze the alternatives, conduct environmental review and prepare for the public hearing. To expedite the project, the County intends to advance preliminary design once a preferred alternative is identified. This can proceed in paralleled with final environmental documentation and public hearing preparations.

What’s the best- and worst-case scenario about how long we won’t have a bridge?

Traffic will need to be detoured for short durations to safely conduct certain major construction activities. The duration of these detours may vary from 6 to 8 hours overnight to 3 to 5 days. The number of longer detours is not expected to exceed a dozen over the duration of construction. Nighttime restrictions, either short full closures, or lane closures, will be needed for periodic material delivery.

Can something be done to accommodate letting both bikes and cars to get by?

A new bridge will accommodate bikes, cars, and pedestrians concurrently.

Will creating a wider navigation channel allow larger vessels to pass?

Yes, a new bridge with a wider channel will accommodate larger vessels than could use the existing channel. However, few if any larger vessels are anticipated as they have not been recorded passing through other bridges to the north and south that have wider navigation channels. The number of barges is expected to increase as those vessels using the Gulf Intracoastal Waterway would no longer divert around the restricted channel at the Blackburn Point Bridge and out into the gulf.

During construction, will signs be placed during construction to let residents know what is going on?

Yes. The County will provide advanced warning signs to alert the public of any upcoming activities that impact traffic.

Who will make the final decision on bridge replacement?

The final decision will be made by the County Commission following a recommendation from the project team.

Will the project require right-of-way acquisition?

The project is currently not expected to require acquisition of adjacent private property.

Will the project impact driveways or access to adjacent properties?

Design alternatives will be developed with the goal of avoiding or minimizing impacts to the driveways accessing adjacent properties. Construction of the project will likely require temporary impacts to driveways. As the design alternatives develop these impacts will be assessed and discussed with the property owners, including avoidance and mitigation measures.

Contact Us

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You may also call or email us at the following:

Phone: Bradley Robertson, 941-861-5000 or Email: [email protected]