Shell Key North Pass and the Grand Canal
Background
In recent years, large amounts of sand have accumulated at the entrance of Grand Canal (Dents Channel). A recent feasibility study by coastal engineers at APTIM found that, without human intervention, the entrance to Grand Canal could close within the next five years.
Description
The project involves dredging of the Grand Canal entrance channel as depicted in Figure 1. As permitted, the Grand Canal entrance channel would be dredged to approximately 11.5 feet deep and 3,000 feet long. This dredging will permit large vessels to continue to access navigable waters via the Grand Canal. The previously proposed deposition basin, which was to act as a sand trap, will not be constructed at this time due to the emergence of seagrass in approximately half of the basin area.
Historical Information
The Shell Key Preserve, including the island and surrounding waters, covers 1,828 acres and has been managed by Pinellas County since 2000. The management plan focuses on balancing public use with habitat preservation, particularly for nesting and migratory shorebirds.
The original plan was approved in 2000 by the Florida Department of Environmental Protection, Acquisition Restoration Council. The first plan update was approved by Pinellas County in October 2007. The latest plan update was drafted in 2018.
June 2011: Waterfront residents adjacent to the Preserve became concerned about the closing of the pass located between Shell Key and Collany Island, referred to as the Shell Key North Pass (SKNP).
2013: The residents hired a dredge to dredge the channel. However, by early 2015, the SKNP had filled in and closed.
October 2015: Tampa Bay Watch held a public meeting where concerns were heard ranging from water quality to predation of shorebirds and sea turtles. Data showing changes in predation due to pass closure is lacking and County analysis suggested that the overall water quality conditions in the Preserve have remained healthy and seagrass coverage has been improving.
May 2016: Pinellas County contracted with the University of South Florida to complete a dual-inlet study of Bunces Pass and Pass-A-Grille Inlet, which included the Shell Key Preserve and adjacent coastal waters. The 2018 study found the estimated maintenance dredging cycle among the three scenarios ranged from one year for a 20-meter-wide cut, to five years for an 80-meter-wide cut.
December 2018: A coastal engineering feasibility study by the County developed an alternatives analysis to identify the options to re-open the SKNP and/or mitigate the potential closure of the southern opening of the Grand Canal. Public input was sought at key stages in the study and several public meetings were held. The dredging of the entrance channel and Basin A as described above are progressing according to schedule.