Consultant provides annual report to County Commission
Data that has been collected since its reopening by Hurricane Milton on Oct. 9, 2024 shows that Midnight Pass “is dynamically stable.”
That was part of the news that a consultant who has been working with the county on the monitoring of the south Siesta Key channel presented to the County Commission this week.
Mike Jenkins, a senior principal engineer at Geosyntec Consultants, launched his Sept. 22 presentation by reminding the board members that their charge to him has been to keep the pass open.
Further, he reported that he and county staff have an emergency plan in place — with the necessary approval of permitting authorities — to reopen the pass if it should close. A major storm, he explained to the commissioners, would be the most likely, anticipated cause of the filling in of the waterway.
At the same time, Jenkins said, he and staff have had discussions with representatives of the Florida Department of Environmental Protection (FDEP) and the U.S. Army Corps of Engineers (USACE) about the permits that would be needed to keep the channel open over the long term between the Gulf and Little Sarasota Bay.
At the board’s direction this week, Jenkins and staff formally will begin that long-term permitting process.
Further, on the basis of details of Jenkins’ report, the commissioners approved a motion directing staff to work on informational signage to help the public navigate the waterway, warn boaters to watch out for non-motorized vessels, and to help protect manatees in the area.
During his presentation, Jenkins emphasized, “There’s a lot of interest in this new inlet,” with representatives of non-governmental organizations and academicians doing studies on their own. Among those initiatives is a focus on the monitoring of the seagrass conditions, he added.
Coordination is occurring among all of those parties and the county, Jenkins noted.
Further, he pointed out of the pass, “It is a very popular inlet. It is highly utilized these days. … It is a unique inlet in the range of stakeholders that use it.”
In fact, he told the commissioners, “I’m not aware of another inlet in this state that has the high use of non-motorized vessels. You see a lot of kayaks, a lot of paddleboards … But you also have the high boat use [and] a lot of jet skis.”
Regular surveys of the “crosshatch of the inlet” continue to take place, Jenkins reported, showing the board members a slide. Those have occurred almost every week since Oct. 9, 2024, he said, resulting in a total close to 90.
“What we have found,” he continued, “is that there are two specific orientations of the inlet within the inlet throat, and that the inlet is oscillating between those two cross sections. … They’re not very far apart.” In fact, Jenkins pointed out, “The only reason we know they exist is ’cause we surveyed to this kind of high level of accuracy.”
The distance is approximately 60 feet, he noted.
Using his hands to demonstrate the action, Jenkins said, “It’s only moving a little bit within a controlled area, and that is dynamic. … It is acting as … we would expect an inlet to act. So, overall, very good news regarding this data.”
Moreover, he said, “We’re seeing an overall trend in increased area. … It is adjusting to an equilibrium area of about 1,400 feet, so it gets bigger at times; it gets smaller at times.”
Additionally, Jenkins told the board members, “We have seen an increasing trend in depth … [to] around 16 feet … in the inlet throat … “At times,” he continued, “it will get shallower, when we get large wave conditions and the inlet has some sand pushed into it.”
However, Jenkins added, the inlet has “shown that it can restore that cross section when it gets smaller … It opens back up within about two weeks.”
He turned next to the flow of the pass. Eight field initiatives to measure the current had shown that the inlet has two channels, Jenkins said. One goes to the north; the other, to the east. “The majority of that water coming in the inlet,” he pointed out, “is going through the east channel” — about two-thirds of the flow.
Further, Jenkins reported, “We have a maximum total flow in excess of a hundred meters per second.” To provide the commissioners context for that, he explained that that is “enough flow … to fill an Olympic-size swimming pool in less than 25 seconds.”
That is another sign of the overall stability of the waterway, Jenkins noted.
Turning again to the flow of water in the pass, Jenkins said that the data has shown that “some of that [water] actually goes around the island and connects. So at times, water comes in one channel and then goes out the other.”
Next, Jenkins reported on what he called “geotechnical investigations,” including the collection of samples from the beach and from the waterway’s interior at a depth of about 10 feet. The dominant material is what he called “shell hash,” or “coarse crushed shell.”
“This is a bit of a surprise, just given regional geology,” Jenkins said, plus the fact that “north Siesta Key is known for fine white [sand]. That is not what is in this inlet.”
However, he explained, “That is good in the sense that it encourages inlet stability …” The shell hash allows for the steeper slope in the inlet, he added, as well as for the relative stability of the channels.
The emergency response plan and future permitting efforts
Jenkins then discussed the emergency response plan that he and staff had worked out with FDEP representatives.
“Our actions would be limited … to restoring the pre-emergency condition,” he explained. “We would be able to restore what’s there today”: the throat and the channels. However, Jenkins pointed out, no expansion of the inlet would be allowed, and no structures could be put in place to try to keep the waterway open.
Moreover, he said, “That work has to conform with accepted practice regarding environmental limitations. Even under an emergency order, we have to consider nesting turtles; we have to consider manatees; we have to consider other resources … But that’s not atypical.”
He also noted that he and staff had confirmed that “the existing county contracts for emergency response can be used for doing this kind of corrective action … So we would not have to bid that work.”
Those existing “at-will” contracts could be used, Jenkins added, “to rapidly deploy … a contractor.”
Then he explained that the work likely would begin with land-based equipment, with access primarily from the north. “It does not preclude the use of in-water equipment,” Jenkins said. However, he explained, “It normally takes time to get … in-water equipment [in place]. Dredges are not just readily available. Land-based equipment is readily available under the existing contract.”
Further, Jenkins told the board, “Excavated material would primarily be placed on the beach to the south of the inlet, because the net movement of sand is to the south.” He added, “Based on what we have seen to date, the conceptual volume is on the order of 25,000 cubic yards. … That is well within the accepted practice for what can be moved with mechanical equipment.”
Commissioner Mark Smith did ask Jenkins, “What’s your definition of ‘rapid response’? … Is that days? Weeks? Months?”
“Weeks to months,” Jenkins replied.
As for a long-term inlet management program: Jenkins pointed out, “We have been engaged with the regulatory agencies” at the state and federal levels. The data collection to-date, he added, is sufficient for that next step. “We know what the cross section of the inlet is,” for example, he noted. “We can now advance a design … towards a formal regulatory permit.”
Nonetheless, Jenkins noted, “It’s a multi-year process.”
Signage and other options
In regard to the variety of people and watercraft using the inlet, Jenkins brought up the fact that no signage exists to promote slow speeds or no wakes; no signage warns boaters to be cautious about manatees; and no signage is provided to denote the de facto channel.
Moreover, he said, no navigational markers exist. “Based on our observations,” he added, “at times, there are some issues” with boaters not knowing the best way to enter the inlet, so they end up “dragging their motors …”
Opportunities also exist, he continued, for dredging the channels, though he said he did not recommend “radically changing the overall channel dimensions. This is always going to be a small draft kind of channel.”
Jenkins showed the commissioners an aerial view of the pass with two areas highlighted by red circles. Those spots, Jenkins said, are where “some infilling” has been taking place.
The north channel, Jenkins pointed out, can be “particularly shallow … at low tide. It’s hard to get a boat around that corner.”
Yet that channel also is the one preferred by kayakers and paddleboarders, he noted. “A couple of informational [signs] saying, ‘Hey, watch out for boats. Watch out for kayakers’ wouldn’t be a bad idea,” he added. “That’s a bit of a blind corner.”
Further, Jenkins pointed out, the greater depth in the east channel is along the south shoreline. With “some strategic dredging,” he continued, “more consistent water depth” could be provided.
He also encouraged the board members to consider providing signage to mark that channel, so it would be clear to boaters that they should anchor outside the channel; kayakers should be outside the channel, too. That “helps with safety concerns,” he said.
If any dredging is done, however, Jenkins stressed, the goal is to make sure that it is used for navigational purposes, “not in any way where we could destabilize the inlet and make it … wanna migrate or do something that we don’t want it to do.”
In response to a question posed by Commissioner Joe Neunder, Jenkins explained, “We tend to have more sand movement during the winter, when we have cold fronts, than in the summer, especially this summer, when we [have] had no tropical events. … There’s not nearly as much sand moving around as we see when we have those cold fronts.”
Commissioner Neunder ended up making the motion to direct staff to proceed with work on the “Future Efforts” delineated in a slide Jenkins had presented to them:
Commissioner Teresa Mast seconded the motion, and it passed 5-0.