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Title: Environmental Assessment : Flood Control & Coastal Emergency Repair, Indian River Inlet North Shore, Sussex County, Delaware, Flood Control and Coastal Emergency (PL 84-99)
Authors: United States. Army. Corps of Engineers. Philadelphia District
Keywords: New Jersey
Shore protection
Flood control
Environmental protection
Environmental management
Publisher: United States. Army. Corps of Engineers. Philadelphia District.
Abstract: The project area for this action is the Delaware Seashore State Park beach north of the Indian River inlet jetty located in Sussex County, Delaware. The project area encompasses the flood shoal borrow area located near the federal navigation channel within Indian River Inlet and the beach extending from the jetty for approximately 5,200 feet (ft) north. The north shore of Indian River Inlet has a long history of beach erosion due to the interruption of the northward flow of sand caused by the construction of the inlet jetties. This erosion has made the critical infrastructure of Delaware Route 1 and the approach to the Indian River Inlet Bridge more vulnerable to storm damages. To provide a consistent source of sand for the north shore, a sand bypass facility was constructed in 1990 by the Corps of Engineers and is operated and maintained by the State of Delaware. This sand bypass system basically mimics the natural net flow of sand from south to north by actively pumping sand from the south fillet across the inlet, and placed on the north shore. The sand pumping rates are variable, but are on average about 100,000 cubic yards (cy) per year. Prior to the construction of the sand bypass system, sand was periodically obtained from the interior Indian River Inlet and placed on the north shore beach. From 1957 to 1990, over 2 million cy of sand were dredged from the inlet interior for the Federal navigation channel, and to obtain beach fill for the eroding shoreline north of the inlet. However, with the start of the Indian River Inlet sand bypassing program in 1990 and subsequent work on scour holes located near the USCG facility in 2010, no additional inlet interior dredging has been required or performed to obtain beachfill or for maintenance of the channel. In recent years, the annual pumping of the sand bypass alone at Indian River Inlet has not kept pace with erosion on the north side (due to a number of factors), which resulted in a diminished beach profile, and a higher vulnerability to storm damages. This vulnerability was exposed in October of 2012 when Hurricane Sandy eroded hundreds of thousands of cubic yards of sand from the northern side of the inlet. This resulted in Route 1 and the approach to the newly constructed Indian River Inlet bridge experiencing overwash from the storm surge. This overwash forced the closure of this critical highway for several days until State crews could remove thousands of cubic yards of sand, and make necessary repairs. Following Hurricane Sandy, an estimated 520,000 cy of sand will be needed to restore the beach template. This sand will be used to rebuild the dune system, which protects the roadway (Hwy 1), newly constructed Indian River Inlet Bridge, and to replenish the beach. Pumping of sand by DNREC occurs seasonally during non peak tourism months and deposits approximately 100,000 cy of material onto the beach north of the jetty. Replacement of sand on the beach is an emergency action. This area, if subjected to additional storm events, would likely fail completely allowing for impacts to transportation on the Highway 1 corridor and possible loss of infrastructure leading to even further costs and loss of coastal transportation and commerce by land. In addition, to the current need of 520,000 cy to repair the north shore beach, a sand source such as the proposed flood shoal sand source (borrow area) may be required for future actions due to storms/emergency actions, and to supplement the existing annual sand nourishment from the sand bypass plant on an “as needed” basis.
Description: Environmental Assessment and Finding of No Significant Impact
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Environmental Documents

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