DHEC staff: Experimental seawalls should not be allowed
December 12th, 2016
By Jake Lucas
Staff from the state’s coastal management agency say the experimental plastic seawalls installed on the beach in stretches of Wild Dunes and on a sea island near Beaufort should come down and not be allowed in the future.
That’s the recommendation Blair Williams, manager of the critical area and wetland permitting section of the Department of Health and Environmental Control’s office of Ocean and Coastal Resource Management (DHEC-OCRM), presented to DHEC’s board last Thursday. The board will ultimately make the final ruling on the devices after a 60-day public comment period and a public hearing.
Staff made the determination after reviewing the results of a roughly five-month pilot program and study of the experimental devices, called a “wave dissipation system” by the group – that includes a Mount Pleasant resident and a Citadel engineering professor – that developed them. The system was studied and analyzed by The Citadel, staff from OCRM, and GEL Engineering, whom the department brought on as a third-party reviewer of the results.
In a report explaining the recommendation, staff say the system does not do enough to fight erosion, has a negative impact on the beach and does not meet the provisions of the budget proviso that permitted the pilot study in 2014.
But in The Citadel’s own report on the study and a letter prefacing it, researchers are critical of what they call “fictitious constraints assigned through the study period” that “made performing research unreasonable at best and impossible at worst.”
Their analysis of the study period reaches a different conclusion than OCRM staff.
“At all sites, the [wave dissipation system] protected the structures behind the system and when used as recommended (not as detailed in this study) the results will be even better,” the report says.
It is signed by Citadel professors Timothy Mays and Mary Watson. The system was dreamed up by Mount Pleasant resident Deron Nettles, who teamed up with Mays to make it.
The system is made of removable PVC pipes that stretch horizontally between vertical piles encased in plastic to make a sort of flexible wall. The spacing between the horizontal pipes can be adjusted, and the pipes can be removed depending on the tide and wave conditions with the goal of taking the punch out of waves while still allowing some sand and water to pass through the system.
One of the Citadel researchers’ main contentions is that they were not allowed to use the system as flexibly as it was designed to be.
“The [wave dissipation system] is a dynamic system that must be configured appropriately for optimal performance and … its use will require modifications and some degree of sand replenishing after severe erosion events,” the researchers write.
Mays and a lawyer representing the group behind the system did not respond to multiple requests to comment on OCRM staff’s recommendation.
In an email, Director of OCRM’s Coastal Services Division Daniel Burger said throughout the study, the department allowed The Citadel to make all kinds of modifications to the system, including adding tiers of protection, removing horizontal pipes, lowering horizontal pipes, adding other experimental panels at the base of the horizontal pipes, and putting sand on the land side of the system.
At one point, OCRM did deny The Citadel team’s request to scrape and move sand that had accreted behind the system at Beachwood East in Wild Dunes on Isle of Palms after the thousand year flood event because staff said it would compromise the study data. The Citadel researchers write that it would have allowed them to rebuild the dune to its configuration before the flood, and it was disappointing that, "OCRM did not allow the research team to prove that it could function in this capacity."
To determine whether the wave dissipation system addressed erosion, staff looked at three indices: did it maintain the scarp line – where the beach is steeply or vertically eroded like a cliff face – from receding, did it maintain or add to the amount of sand landward of where it was installed, and did it minimize erosion at the base of where it was installed, which can create trenches that make erosion worse.
The answer to all three of those questions, OCRM staff determined, is no.
Burger said those indices were chosen as performance measures because they were “directly related to The Citadel’s stated purpose of studying the [system]” or were noted by the Citadel as areas of concern.
OCRM staff also write in their report that the system may have prevented sea turtles from laying eggs. The Citadel’s report says the horizontal pipes could easily be removed from the system during turtle season, and they would have done so during the study period if not for an objection from OCRM that it would have altered the results of the study.
Earlier this month, the South Carolina Environmental Law Project filed a lawsuit against against DHEC on behalf of the Sierra Club and the S.C. Wildlife Federation claiming the wave dissipation system is harming endangered sea turtles under the Endangered Species Act by getting in the way of them nesting. The Law Project threatened the suit at the end of June, and DHEC ordered the walls to come down at the end of the study period in response and after consulting the Department of Natural Resources.
But lawyers representing the property owners where the system is installed challenged that ruling, and in October, the DHEC board ruled that the system should stay in place until it makes a decision on the future.
In their report on their recommendation to the board, staff say the system also has a negative impact on the beach and the public's ability to access it by not adequately keeping erosion in check, enabling trenches to form and requiring excavation in the course of installing the system.
Together with the potential impact on sea turtles, staff say those shortcomings put the system at odds with a number of the elements of a “qualified wave dissipation device” laid out in the budget proviso that authorized the study.
From here, there will be a 60-day public comment period and a public hearing on staff’s recommendation ahead of the board taking its final vote on whether the system can be used in emergency situations in the future and whether it must come down where it is currently installed.
If the board rules not to allow it, that would leave property owners seeking emergency protection for structures sandbags as their only option. However, Williams, the wetland permitting manager for OCRM, said the agency is trying to push people toward longer term solutions like renourishment.
“The thing to keep in mind here is these things are temporary protection,” he told the board. “They should be temporary protection, and what they’re really doing, even with sandbags, is it gives them a false sense of security.”
In the case of Isle of Palms, the city is submitting a permitting application for a beach restoration project at both the eastern and western ends of the island.
While the city applied for the expansive permit, officials have yet to decide whether to include the western end of the island nearer breach inlet in the project, which rough estimates suggest could add as much as $4 million to an already $15 million project. At the eastern end of the island, the project targets two linear miles of beach from 53rd Avenue to the 18th hole of the Wild Dunes Links Course, including the stretches where the wave dissipation system is currently installed.