Guajataca Dam, spillway erosion, and repairs

As Puerto Rico continues to grapple with the aftermath of Hurricane Maria, information on damage to the Guajataca Dam remains scarce, while reports suggest spillway repairs may be ongoing.

Hurricane Maria made landfall in Puerto Rico last month, bringing 150 mph winds and 20 inches of rain.  Damage to infrastructure was widespread, and the destruction of electricity and communications networks hindered efforts to assess the damage and move toward recovery.

Early reports suggested that the Guajataca Dam had "failed".  On September 22, the National Weather Service's San Juan office tweeted an alert of a "flash flood emergency for a dam failure" at the Guajataca Dam and noted ongoing evacuations.

But as reported by Vox on September 30, an Army Corps spokesman said that the dam was not breached and "has not failed and not collapsed."  The article described damage to the dam's overflow spillway.

According to a Department of Defense posting dated October 1, 2017, the Defense Department has deployed more response capacity to Puerto Rico, while the Guajataca Dam spillway continued to erode.  The Defense Department said U.S. Transportation Command delivered 900 super sandbags for spillway stabilization to Aguadilla Airport on September 30, and that spillway sandbag installation by the Army Corps of Engineers would start on October 1 and will be complete by October 2.

An article posted by The Independent on October 4 describes the Army Corps' use of Osprey V2 rotor-tilt heavy-lift aircraft to drop concrete barriers from the dam into the spillway, in an attempt to limit further erosion of the spillway channel.  The article says the "channel has suffered serious erosion as much of its cement cladding was washed away."

Dam safety and flood control spillway damage have featured prominently in recent news.  California's Oroville Dam's spillway was damaged earlier this year, including a concrete failure on the lower chute of the gated flood control spillway, severe erosion under the gated spillway, and erosion in the areas on the hillside beneath the emergency spillway.  According to the California Department of Water Resources, repairs at Oroville Dam will remain ongoing into 2018 or beyond.