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Longboat Key Wednesday, Feb. 2, 2011 8 years ago

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Sometimes, you just need to try, experiment, see if it works, take a calculated risk. Be bold.

Governments are not good at this. They are risk averse. And for the most part, that’s a good attribute. For one, no taxpayer wants his government taking high-risk bets with his tax dollars.

But sometimes this no-risk or little-risk approach can become an impediment to innovation and progress. At times, this is the way it seems on Longboat Key.

The town, for instance, has been using Coastal Planning and Engineering as its beach consultant for about two decades. And under CP&E, the town consistently has followed a beach maintenance strategy that fits with the nature of the Gulf of Mexico’s southerly tides and flows: Replenish the sand system with hundreds of thousand or millions of cubic feet of sand every six to eight years and treat the beach’s hot spots as they require it.

This strategy has been working the way it is supposed to. What’s more, St. Denis says, our beach maintenance system is often considered among the more innovative and successful in all of Florida.

But now we have a new wrinkle — the extreme erosion on the northern tip of the Key. As St. Denis explained last week, the erosion there appears to be the result of several factors: the hurricanes in the mid-2000s; the way the U.S. Corps of Engineers added a southerly curve to its dredging of the Longboat Pass channel; and the way the waves hit that part of the beach with water coming from the north and south.

To thwart this natural and man-made phenomenon, the town’s engineers believe the best way to manage the erosion there is to replenish the sand and install a terminal groin, similar to the one that juts out from the Anna Maria side of the pass.

Sarasota engineer Fred Derr, however, believes his soil cement-step revetments would be much less expensive and equally effective, if not more effective.

St. Denis and the town’s beach engineers believe the revetments are not the right choice. They may be totally right.

Nonetheless, there is still an intriguing element to Derr’s revetment. The fact Derr was able to obtain a permit from the Florida Department of Environmental Protection for his Casey Key project gives his soil revetments a large degree of credibility. The FDEP is rarely sympathetic to anything out of the norm.
What also comes to mind is a business analysis that entrepreneurial CEOs often employ when they consider new, unproven ventures. They ask themselves:

What’s the worst that could happen if it fails? Would the new venture’s failure destroy the company?
In this instance, would the failure of a revetment be disastrous to private property? Now let’s add a corollary to the that question, which is another approach entrepreneurial CEOs employ:

Spend a little, learn a lot.

In other words, give it a try. Test a soil cement-step revetment. Surely engineers can create a model to replicate the north-beach erosion and test its efficacy. Who knows? It could save us millions in the long run.

Think where all of us would be if we were afraid to take a risk.

CASEY KEY BEACH: BRUCE ST. DENIS RESPONDS; FRED DERR RESPONDS
Last week’s front-page of the Longboat Observer reported how Fred Derr’s soil cement-step revetments helped stop erosion in the 1990s on Casey Key.

Derr told Longboat Observer City Editor Kurt Schultheis he met with Longboat Key Town Manager Bruce St. Denis and Public Works Director Juan Florensa two years ago to explore a similar idea for Longboat Key. Derr told us St. Denis would contact him after St. Denis consulted with the town’s beach engineers about Derr’s revetments. Derr says he hasn’t heard back from St. Denis.

In a letter below, St. Denis provides his response to our report. And below that, Derr responds to St. Denis’ letter.

Make your own conclusions.

+ Not the right solution
Dear Editor:
Regarding the step revetments on Casey Key …

Midnight Pass started to close in the mid-to late-1980s. Subsequent to that, 400,000 cubic yards of the ebb shoal destabilized and attached to the north end of Casey Key, which grew to up to 300 feet of additional width.

This sand eventually worked its way southward, providing a uniform beach of approximately 150 feet in width. These beach changes occurred around the same time as construction of Fred Derr’s step revetments.

The step revetments are about 1,500 feet to 1,600 feet in length. The total beach area improved by the collapse of the ebb shoal approaches 20,000 linear feet, meaning there is a substantial beach on North Casey Key whether or not there is a revetment in place.

It would be up to Fred Derr to provide pre- and post-survey data to show that the step revetments are actually causing beach accretion.

I did meet with Mr. Derr in early September 2008 and have great respect for him and his
accomplishments. In our discussion, I expressed my doubt about the ability of any type of revetment to hold or accumulate sand. However, I agreed that staff members would go to Casey Key to look at the project area.

Longboat Key Public Works Director Juan Florensa and Longboat Key Project Manager James Linkogle met on Casey Key with Mr. Keith Ravazzoli, who is the president of Frederick Derr & Co. They met and had coffee with the Collinses, who are shown in the Longboat Observer photograph on page 8A. Staff’s conclusion after the visit was that there did not appear to be a correlation between beach width and the step revetments on Casey Key.

We took the additional step of requesting that Coastal Planning & Engineering evaluate the step revetments and their impact on sand accumulation. We received the following response on Oct. 29, 2008.
“1. The revetment is one of many upland protections that are available for use. All of them will not be reviewed favorably by the Florida Department of Environmental Protection (FDEP) for both littoral transport and sea-turtle protection considerations.

“The sediment transport curve appears to be quite steep (erosive) in a northerly direction at Northshore Road. The application of the revetment should not stabilize the sandy beach under these conditions. It is not clear what the littoral transport conditions are along Casey Key Road.

“We do not recommend further consideration of this technology.”

In summary, we did meet with Mr. Derr and explained that we did not think that the revetment was the appropriate solution as long as the town’s emphasis was on maintaining a sandy beach.

We also visited the revetment project on Casey Key and, finally, the beach engineers recommended against further consideration of revetments as part of an effort to maintain a sandy beach.
Bruce St. Denis
Longboat Key town manager

+ Fred Derr responds
Midnight Pass in the early 1980s began an accelerated northward migration, which eventually impacted the Siesta Key homes of artist Syd Solomon and a Mr. Carter.

In December 1983, they hired a firm to dredge Midnight Pass and deposit the spoil on their property.
The pass was dredged three times, and each time Mother Nature closed the pass every time it was dredged. After the third dredging, the project was abandoned; Midnight Pass has been closed ever since.

So Mr. St. Denis’ statement that the pass started to close in the mid-to late-1980s is incorrect.

I am unable to comment as to whether there was 300 feet of additional width on North Casey Key, but I can tell you that in 1991 when we began the permitting process for the step revetment, there was about
100 feet of beach in front of Mr. Will Collins’ house.

When we received the permit three years later in 1994, we had only 25 feet of beach left and the houses we were trying to protect were teetering on a 20-foot bluff ready to topple into the Gulf.

So the sand providing a uniform beach of about 150 feet in width was nowhere to be seen in January 1994.

As far as the length of the three step revetments is concerned, they were 3,215 feet total. So it appears there was 3,215 feet of beach area that was not improved by the collapse of the ebb shoal, which according to St. Denis provided 20,000 feet of substantial beach.

Now that we have established that the closing of Midnight Pass did not provide any substantial beach in the areas where the soil cement-step revetments were constructed, I can only conclude that the property owners in these areas have fared much better since the revetments were completed than they were before.

In the coastal-erosion business there are no guarantees. There are too many variables — wind, tides, currents, wave action and storms. After careful thought, combined with reasonable assumptions, you almost have to call your project an experiment.

Fortunately, for the property owners on Casey Key, our assumptions were correct, and the structures have performed exceedingly well.

As to whether a soil cement-step revetment would work at the north end of Longboat Key, I cannot guarantee that it would, but I suspect that if properly configured and constructed, chances of success are pretty good.
Fred Derr
Sarasota

 

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