Military aims to dredge coral reef

Scoured rock, coral rubble, and a contoured sea floor would be left of a vital reef off Tinian, if a ramp for military assault vehicles were to be built.

Unai Chulu, 20-30 percent of Tinian’s reef flat habitat and an “Essential Fish Habitat” for fish to spawn, breed, and grow, is the beach targeted for the dredging work.

The proposed coral dredging is detailed in the CNMI Joint Military Training Environmental Impact Statement, which regulatory agencies are now poring over in detail in time before its 60-day comment period ends.

The ramps would be “constructed on federal submerged lands,” the military says, and would support training on the military leased land on Tinian.

But when sought for comment, the Bureau of Environmental and Coastal Quality said this could still have a “spillover effect” for the CNMI.

In 2014, President Barack Obama exempted from transfer to the CNMI the submerged lands adjacent to the islands of Tinian and Farallon de Medinilla, a routine-bombing area. Obama, in his proclamation, called these lands “essential for ensuring” that the U.S. forces are adequately trained and “ready to respond immediately and effectively” to national order and security.

“Unfortunately the submerged lands next to Tinian were not conveyed back with the other submerged lands in January 2014,” BECQ federal consistency specialist Megan Jungwiwattanaporn told Saipan Tribune.

“However, the CNMI will still be expressing concerns over the offshore construction described in the CJMT EIS. The military plan to dredge coral is a definite concern and BECQ will be commenting on it. The public comment period for the EIS allows us to express concerns on military land. As we go forward with federal consistency requirements, we will show how dredging such a large expanse of coral could have spillover effects for the CNMI.”

Unai Chulu

The EIS calls this reef area physically complex, with very deep, irregularly spaced spurs and grooves.

These groves interconnect with other grooves and create a network of tunnels, grottoes, fissures, and chimneys that penetrate from shallow reef to deep.

The EIS describes an in-water landing area for amphibious assault vehicles that would alter the limestone and coral reef of this sea floor.

The landing area would be contoured into a pile-armored ramp at a 15-degree slope, and would consist of “a gravel bed atop” the coral base, and a “durable grooved concrete slab” designed to resist severe wave conditions.

Trenches with concrete anchors would secure the ramp. The ramp would be 656 feet long and average 160-feet wide with an anticipated dredge volume of 798,111 cubic feet.

Temporary causeways would be need for construction, in which “steel sheet piles and steel pipe piles would be installed” into the reef and penetrate about 40 feet into it.

These pipes would be removed after the 36-week construction. Excess dredge material could be re-used or disposed of in-water or upland.

The EIS finds, though, that construction will not significantly modify the shoreline coastal processes or trigger erosion at the beach.

The EIS says water quality effects like turbidity would be minimized. It says the “primary physical impact of in-water construction would be to permanently convert complex and variable reef habitat to an essentially flat surface bordered by disturbed areas of coral rubble, and scoured rock.”

The EIS notes that biological diversity and productivity within the impacted area would be diminished.

But construction would be “soft-start” so that fish could “have a chance to leave the area to avoid injury prior to the impact hammer operating at full capacity.”

The EIS finds that construction would cause temporary, as well as permanent, loss and degradation of coral reef habitat. Fish may be displaced. Coral reef would be permanently altered and removed. Changes to local fish populations would occur.

Citing studies that say the beach is “one of seven well-developed reef flats on Tinian, “the EIS finds that given the importance of this habitat as “Essential Fish Habitat” and its limited availability on Tinian, “the removal of the coral reef at this beach” during construction would result in “significant impacts to marine habitats.”

Fish loss would be roughly equivalent to loss of reef, the EIS says. Colonies of endangered coral species, Acropora globiceps, would also be significantly impacted by the construction.