Some Ewa Beach residents are concerned that a Marine Corps plan to install 1,500 feet of steel barrier to protect part of the oceanfront Puuloa Range Training Facility from beach erosion could create new problems for residents on either end.
The proposal comes amid statewide concern over rising sea levels and eroding beaches--and a proliferation of sea walls to try to counter those effects.
"When erosion threatens the built environment a common reaction is to armor the shoreline with a seawall or revetment, " the Hawaii Coastal Erosion Website under the University of Hawaii states.
Past studies show that 70 % of Hawaii's beaches are eroding. Armoring a chronically eroding coast leads to further beach loss, according to shoreline experts.
On Tuesday, U.S. Sen. Brian Schatz called on the U.S. Marine Corps to review the environmental impact of its plan to build the retaining wall in Ewa Beach.
"It is incumbent that the Marine Corps explore long-term resilience benefits for the Puuloa Range Training Facility that avoid unnecessary environmental impacts on Hawaii's beaches and the residents of Ewa Beach, " wrote Schatz.
The Hawaii Democrat asked that the Marine Corps revisit alternatives for the project "to ensure that it has assessed the feasibility of designing a project that draws on natural and nature-based features, consistent with existing engineering best practices for coastal zone management and beach erosion."
As of Tuesday, meanwhile, 1,126 people had signed a petition at change.org seeking a more thorough environmental impact statement analysis for the effects of the shoreline construction beyond the less robust environmental assessment already conducted.
The Marine Corps in late August produced a proposed "finding of no significant impact " for the plan for about 1, 500 feet of "sheet pile " that likely would be steel along the boundary of long-distance ranges A and B, and a "retreat " of about 100 feet from the sea for short-distance ranges C through F.
Sheet pile would be installed on the "fast land " boundary (above the tidal influence ) by driving it through sand and coral seaward of a range berm topped by a concrete wall.
The modifications are needed to protect the range shoreline from continuing erosion that could compromise the heavily used range needed to train combat-capable forces for worldwide deployments, the Corps said.
"No significant impacts are expected to adjacent shoreline areas due to the predominant west to east longshore sand transport, the buffer areas provided at either end of the proposed sheet pile, and the design elements of the proposed sheet pile which would minimize impacts from end (sand ) scour, " the Marine Corps report said.
But longtime Ewa Beach resident Mike Plowman said he has concerns about the effects of the Marine Corps sea wall in combination with nine big T-head groins placed nearby off what was then Iroquois Point and now is known as Kapilina Beach Homes.
Nine thousand cubic yards of sand that had drifted around into the Pearl Harbor entrance channel was dredged and used to fill the T-head groins as part of the project completed in 2013.
Although the Marine Corps' plan is to pile-drive the sheet pile into sand and coral so that only about a foot is visible, Plowman said as soon as sand is displaced, it becomes a de facto sea wall.
"And how that is going to affect the Ewa Beach shoreline is undetermined, " Plowman said. "There's history with the nine groins that were placed at Iroquois Point which they cite in the (environmental assessment ) and some resulting erosion at (Puuloa ) because of that."
With further beach erosion, the Marine Corps sheet pile could be exposed to wave action and adversely affect one or both sides of the beaches that it's adjacent to, he said.
The 165-acre Puuloa range is owned and operated by the Marine Corps but used by all military branches as well as state and county police, the FBI and other law enforcement, according to the environmental assessment.
The area was acquired by the Army between 1904 and 1905 as part of the coastal defense of Oahu. By the end of 1915, the Marine Corps had established a pistol range and rifle range up to 1, 000 yards with a tent camp for officers and enlisted service members.
The range, which extends along 3,000 feet of sandy shoreline and is part of the Pearl Harbor Naval Defensive Sea Area, has six small arms ranges as well as ranges A and B on the west end that are up to 3, 000 yards.
Beginning just east of the range, the shoreline had been chronically and severely eroding for more than 60 years and prompted the T-head groin construction, the Marine Corps noted. The nearest groin is 500 feet east of the range boundary.
The Marine Corps indicated it would begin the sheet pile project as soon as funding becomes available.
Schatz wrote to Marine Corps Commandant Gen. David Berger noting that the U.S. Army Corps of Engineers "Engineering With Nature " initiative offers lessons for drawing on nature-based approaches to mitigate coastal erosion.
Schatz gave the example of developing artificial reefs to reduce the effects that waves have on beach erosion. He asked for a response "with an explanation of the way forward on this project " no later than Dec. 6.
This article is written by William Cole from The Honolulu Star-Advertiser and was legally licensed via the Tribune Content Agency through the NewsCred publisher network. Please direct all licensing questions to firstname.lastname@example.org.