Advancing the Practice with New Guidelines for Thin Layer Placement

The USACE dredges more than 200 million cubic yards of sediments every year as part of their mission to ensure that ports and waterways remain open to traffic. In S5E6, we talked with Lt. Gen. Spellman, the 55th Chief of Engineers and the Commanding General of USACE, about his 70/30 goal to increase the beneficial use of these sediment from about 30% up to 70% by the year 2030. Supporting the USACE environmental protection and restoration missions, this ambitious goal calls for innovative uses of sediment. Our guests are advancing the practice of thin layer placement (TLP) through the development of new guidelines based on leading practice applications.

In Season 6, Episode 9, hosts Sarah Thorne and Jeff King, Lead of the EWN® Program at USACE, welcome Candice Piercy, Research Environmental Engineer at the Engineer Research and Development Center (ERDC), USACE; Ram Mohan, Senior Principal at Anchor QEA and Adjunct Professor at Texas A&M University; and Monica Chasten, Coastal Engineer and Project Manager in the Philadelphia District, USACE. Candice and Ram coauthored the recently published Guidelines for How to Approach Thin-Layer Placement Projects with their colleague, Tim Welp, a renowned dredging expert who passed away in 2021. Tim was the inspiration behind the guidelines, and this episode is dedicated to him. Monica is an innovator and leading light in the dredging community with responsibilities for keeping open the coastal navigation channels in NJ and Delaware. She was an early adopter of EWN and one of the first movers of beneficial use of dredge materials.

TLP is defined as the purposeful placement of thin layers of sediment (e.g., dredged material) in an environmentally acceptable manner to achieve a target elevation or thickness. As Candice explains, “TLP really reflects a different approach where we’re purposefully placing the material in relatively thin lifts to accomplish an ecological objective. We’re often doing this because the natural process of sediments collecting in our marshes is not sufficient for it to keep up with rising sea levels.”

Early in his career, Ram wondered whether dredged material could be used as a resource to improve coastal habitats. TLP essentially consists of spraying dredge material so that it rains down in a very gentle manner. Rom notes, “Whether you place it over a marsh or in a subaquatic habitat, this low stress placement method allows it to gently deposit over the existing bottom, making it very conducive to future recovery within two to three growing seasons.”

Monica gets passionate about sediment and doing the right things with it. “Prior to becoming a Project Manager for navigation projects, I was working on beach fill projects for the Corps where every grain of sediment is incredibly valuable. Then I moved into the navigation world in the back bays in NJ where we were basically throwing beautiful sediment away. Looking at all types of sediment and how we could use it innovatively became a mission for me.”

Jeff notes, “Sediment is supposed to move and be transported by natural processes in various areas of estuarine systems. When we take it out, we’re starving the wetlands. With TLP, these systems are going to be much better off.” Jeff adds that LTG Spellmon’s 70/30 goal and the new guidelines are game-changing: “I talk with practitioners all over the country, and I know people have been eagerly awaiting them. They are really going to move the needle.”

For more information and resource links, please visit the EWN Podcast page on the EWN website at https://www.engineeringwithnature.org/
• Jeff King at LinkedIn
• Candice Piercy at EWN
• Ram Mohan at LinkedIn
• Monica Chasten at EWN