Florida Keys News
Wednesday, May 17, 2017
City mulls plans to shore up beach
City to remedy Coco Plum erosion

MARATHON — Coco Plum Beach has long provided a sandy stretch on the Atlantic Ocean popular with both sunbathers and nesting sea turtles. Erosion, however, is washing away the beach and altering the shoreline.

The Marathon City Council recently approved a plan to replenish the beach while seeking grant funding since solutions are costly.

The council last month discussed options in a study conducted by Bermello Ajamil & Partners as well as recommendations by staff on how to save the beach. The goal is to reduce erosion, by determining its rate, cause and direction, and to provide alternatives with requirements for implementation and cost.

Coco Plum Beach, which is managed by the city, is a natural beach with an adjacent wetland area. It is situated in an area of partially-reclaimed land about 1,700 feet from a condominium to the west. In its current condition, beach width is 15 to 20 feet during low tide, according to the study. 

As evident by numerous complaints of the condition of Coco Plum Beach since the last re-nourishment project, conditions have deteriorated to the point where the beach is often unusable, staff said. 

During high tides, the beach is almost non-existent as the water level covers the sand all the way to the planted dunes, the study found. During periods of heavy seaweed, when the tide recedes, up to 6 inches of seaweed covers the entire beach.

The city provides beach raking twice a week; however, the gaps during the week allow more seaweed to accumulate. Physical removal of the seaweed is limited as it further aggravates the situation due to the difficulty of separating sand from wet seaweed, thus accelerating the removal of sand from the beach. The continual raking of the beach not only accelerates the removal of the beach sand, but also diminishes the quality of the remaining sand, the study found.

The study shows that the orientation of the beach, combined with a predominantly easterly wind and wave direction, rapidly erodes the sand. Sand added to the beach is typically eroded away to the current condition in approximately three years. The typical cost of the beach re-nourishment in the existing condition is $100,000 to $150,000.

Proposed improvements on reducing erosion were given in three alternatives: 

• Alternative 1 proposes the continuous re-nourishment of the beach without any other measures to address future erosion. Permits with state and federal agencies are required, but the impact is minimal and the permitting period is typically three to four months. In the short term, this is the most economical alternative; however, due to continual erosion over a 10-year period, it becomes the most expensive due to the requirement of re-nourishment every three years, staff said. This alternative also provides the least amount of usable beach width for use by the public.

• Alternative 2 proposes constructing small breakwaters every 50 to 80 feet along the shore and one to the northeast. This alternative has minimal to no impact on marine resources and would provide an approximate beach width of 30 feet. While no direct impact to marine resources is anticipated under this alternative, work will still be proposed waterward of mean high water, necessitating permitting through the state Department of Environmental Protection and the U.S. Army Corps of Engineers. The estimated permitting process with the Army Corps would take approximately two years. This alternative provides an estimated 10-year solution before any additional re-nourishment to the beach is necessary.

• Alternative 3 proposes constructing slightly larger T-groins and breakwaters approximately 80 to 140 feet apart. These structures would project further into the water and would impact marine resources consisting of sparse seagrass. This alternative would provide an approximate beach width of 40 feet, the widest of all alternatives. Like the second alternative, the work requires permitting from the same agencies and likely would require some type of mitigation for the proposed impacts. The estimated time for a future re-nourishment project also is 10 years.

Staff reviewed the costs and benefits of each alternative and, because the city seeks and typically obtains grant funding for re-nourishment projects, it recommended proceeding with the design work and permitting for Alternate 3 at a cost of $1.26 million. Alternative 2 will serve as a fallback position.

“Since we are anticipating two to two-and-a-half years of permitting for alternatives 2 or 3, this gives the city ample time to seek funding for this project,” wrote Public Works Director Carlos Solis, who recommended that the city design and submit for permitting on Alternate 3 while seeking grant funding, which would provide the best benefit for use by the public. “Depending on funding availability, the project can be scaled back to Alternate 2 if the funding for the more intense project is not available.”

To get to Coco Plum Beach from U.S. 1 at mile marker 55, visitors turn on to Coco Plum Drive and the beach entrance is 1.4 miles on the right. Restrooms and a covered pavilion are available, and hours are from 7:30 a.m. until dusk.

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