Treasure Island East Causeway Roadway & Drainage Improvements Project
Drive the Treasure Island Causeway and you'll see that many of the bottle brush trees that lined the causeway for years are now mere stumps. Removal of these iconic trees, though many at the end of the useful life, is required to create better drainage on a section of the causeway that historically "ponds up" after a heavy rain.
Construction plans are being finalized for the East Causeway. The updated design does not require a shift in the roadway and thus the central median width is maintained. Subsurface investigation found that the roadway’s base material was in a generally suitable condition to remain in place. As evidenced by imperfections seen on the roadway, spot repair of the base material will be needed in some locations. These repairs made and there will be an evaluation of the cost effectiveness of other base rehabilitation techniques once formal construction bids are received.
Stormwater improvements will focus on increased collection efficiency while improving the quality of water that is discharged to Boca Ciega Bay. Gently sloped depressional areas, called bioswales, will be constructed along the outer edges of the roadway to allow rainwater to flow off the driving surface. Low Impact Development (LID) design techniques were utilized so that the “first flush” is retained within the bioswales. The “first flush” is a small volume of water collected during the beginning of a storm that typically contains a high concentration of pollutants and debris. While this small volume of water will be retained within the bioswales and allowed to infiltrate over a 72-hour period, any remaining stormwater will flow to Boca Ciega Bay through existing and newly constructed pipes.
Pedestrian improvements will be focused at the intersection of 79th Street. Here, curb ramps with detectable warning surfaces will be installed at each corner of the intersection to comply with current accessibility standards. The current crosswalk locations will be re-striped and rapid flashing beacons will be installed at the intersection prior to the east bridge. This eastern pedestrian crossing will also be improved to current standards.
In effort to beautify the corridor and to assist with nutrient uptake from collected stormwater, Florida-friendly landscaping will be provided within the bioswales. Upon completion of the roadway and drainage improvements, the median will be re-landscaped and the lighting will be changed out to provide decorative poles as seen on the western side of the Causeway. The new poles will be energized by an underground feed that eliminates the need for aboveground wires. The landscaping plan for the median is currently under development.
Project Management & Schedule
The Contractor will be required to maintain an organized work site and safe traffic patterns. The project has been designed in a manner that will minimize the need to for long-duration roadway closures. However, there will be certain phases during construction where traffic detours will be needed. Residents and visitors will be notified in advance of these occurrences. The roadway and drainage construction are anticipated to begin early 2021 and will be complete by the end of the year. The lighting changeout and the median landscaping will occur soon thereafter.