Posted on December 16, 2024
DNREC has begun the emergency dredging project to repair the North Indian River Inlet Beach. Beginning the week of Nov. 25, dredged material from the Inlet flood shoal will be used to restore the beach and dune system.
The project aims to strengthen shoreline resiliency and protect critical infrastructure, like Delaware State Route 1 (SR 1), an evacuation route, from the damaging effects of coastal erosion.
Project Overview
The $15 million project (cost-shared with the federal government) will accommodate dredging up to 400,000 cubic yards of sand from the Indian River Inlet Flood Shoal for rebuilding up to 5,000 linear feet of shoreline.
Dredged material will be transported via pipeline and screened for munitions and explosives of concern (MEC) prior to placement on the beach. Sand will be spread and graded to rebuild the dune system to an overall elevation of 16 feet by 25 feet wide.
The beach will be constructed to an elevation of 9.2 feet, or about 7 feet above the average high tide, and width of approximately 100 feet. The final beach width will be determined by the available dredge volume.
Restoration will begin at the north inlet jetty and extend northward along the shoreline.
Dredgit Corporation is currently staged near the Indian River Inlet north shore marina and campground. The dredge and support equipment are being prepared to pump sand starting the week of Nov. 25. In addition, the dredge pipeline has been fused and routed around the Delaware Seashore State Park North Campground and under the Inlet Bridge.
The North Indian River Inlet Beach (North Beach) is currently closed to ensure public safety. DNREC will monitor the situation and work with the contractors to reopen this area when it is deemed to be safe for park visitors and surfers.
Pedestrian and bicycle access is limited from the North Campground to the SR 1 northbound lane. ADA-compliant multiuse ramps will be provided at all pedestrian pipeline crossings. However, due to safety considerations, access to the area is discouraged.
The U.S. Coast Guard has been given notice for mariners to exercise caution and maintain a safe distance from the ongoing dredging activity, including floating and submerged pipelines, the dredge and support vessels within the area of operations in the Indian River Inlet.
Nov. 17, 2024, aerial view of the dune breach at Delaware Seashore State Park (looking north). The SR-1 northbound lane is closed to vehicles and completely covered in ocean water, sand and debris
The Need for Beach Repair
The North Indian River Inlet coastline has a long history of erosion due to construction of the inlet jetties that began in 1928. The jetties were built to stabilize the inlet and improve navigation, but the hard structures interrupt the natural northward flow of sand via the longshore current.
As a result, sand is trapped by the south jetty and accumulates on the updrift (or south) side, creating a larger beach in that area. Consequently, the downdrift (or north) side of the north jetty experiences a lack of sediment supply, leading to erosion.
From 1957 to 1990, over 2 million cubic yards of sand was dredged from Indian River Inlet to maintain the channel and obtain beach fill for the eroding north Inlet beach. In 1990, the U.S. Army Corps of Engineers (USACE) built the Sand Bypassing Facility to continuously pump sand from the south Inlet beach to North Beach via pipeline and was the primary maintenance activity for many years.
The Sand Bypassing Facility became inoperable in 2019. Since then, DNREC has relied on truck-haul sand from inland sources for beach nourishment. Over time, conditions at North Beach have severely deteriorated and adding sand via truck-haul could no longer overcome the rate of erosion.
Dune breaches occurred during March and August of 2024 due to offshore storms. These storms resulted in flooding and closure of the SR 1 northbound lane for several hours as ocean water subsided, and the roadway could be cleared of sand and debris.
North Beach requires a large volume of sand that is rapidly delivered to reconstruct the dune system to a template that would mitigate erosion. By implementing this project and repairing the Sand Bypassing Facility (expected early 2025), we anticipate North Beach will be sustained for several years.
Indian River Inlet Flood Shoal
The Indian River Inlet Flood Shoal is a sandy borrow area that was previously used by the USACE in 2013 to rebuild North Beach following Hurricane Sandy.
Topographic survey data showed that nearly 100% of the sand dredged from the flood shoal in 2013 had recovered within four years; therefore, DNREC evaluated the current material as a borrow source for repairing North Beach.
Sediment cores from the Indian River Inlet Flood Shoal were evaluated for grain size and the presence of contaminants (metals, PAHs, PCBs, pesticides and Dioxins/furans) with associated potential toxicity to benthic aquatic life and human health using risk-based assessment methods and the appropriate guideline concentrations.
Laboratory results confirmed sandy material (an average of 96%) and detected a few contaminants in composite samples, but none were found at concentrations that would impact aquatic life or human health if sediments were dredged and used to rebuild North Beach.
