Guajataca Dam repairs, a successful interagency team effort

Published May 13, 2019
Chinook helicopter places a large sand bag on the spillway

A CH-47 Chinook helicopter from the Puerto Rico Army National Guard places a large sand bag on the spillway of the 89-year-old Guajataca Dam in Isabela, Puerto Rico, Oct. 9, 2017, after the dam was damaged during Hurricane Maria. The U.S. Army Corps of Engineers, the guardsmen and local contractors stabilize the dam’s spillway to ensure the safety of the residents downstream. The Department of Defense and other organizations assist civil authorities to provide disaster relief in Puerto Rico in response to Hurricane Maria. (U.S. Army photo by Pvt. Alleea Oliver)

damaged spillway

A Navy MH53 helicopter places a barrier down to strengthen the broken dam, Oct. 5, 2017 at Guajataca Dam, Isabela, Puerto Rico. The Department of Defense is conducting on-going missions to rebuild and assist the citizens of Puerto Rico. (U.S. Army photo by: Pfc. Deomontez Duncan)

The devastating path of Hurricane Maria in 2017 affected all of Puerto Rico in one way or another. As a result the Federal Emergency Management Agency immediately activated the U.S. Army Corps of Engineers to serve as part of the post-Hurricane María Response Team.

Only four days after the hurricane overwhelmed the island, a team of over 40 USACE volunteers from different parts of the United States arrived in Puerto Rico to respond to this emergency. The team augmented the local USACE Antilles Area Office staff in the efforts to visually inspect 17 dams determined to be high hazard, or thought to have incurred damage during the hurricane.

Guajataca Dam, the most important water storage structure in the northwest of the island owned by the Puerto Rico Electric Power Authority, was found to be in an active state of failure resulting from water overflowing the spillway. The erosion destroyed most of the spillway and the water supply line that crossed beneath it, as well as severely damaged the dam outlet gates. The team, along with local and federal agencies mutually agreed that immediate repair was necessary.

USACE immediately coordinated with FEMA and PREPA to stop the progressive loss of the spillway and potential failure of the dam. Different branches of the military provided aircraft support to deliver materials. Moreover, USACE installed water pumps that helped both maintain safe water levels at the reservoir and supply water to the seven municipalities served by the Guajataca Dam.

“Over ten local and federal agencies as well as military personnel supported the emergency mission of stabilizing the spillway, we were successful because of their rapid response and their willingness to collaborate towards the same goal” said USACE’s Antilles Area Engineer Maricarmen Crespo. “USACE’s rapid response in requesting reach back support to the U.S. Armed forces to deliver material to the dam prevented a potential catastrophe.”

The initial emergency measures were only intended to reduce the risk of imminent dam failure. Since the spillway continued facing an unacceptable risk of failure during a future natural disaster USACE recommended additional measures. Therefore, FEMA assigned USACE the mission of implementing six temporary measures intended to lower risk and protect the communities living downstream of Guajataca Dam until permanent repairs could be implemented. This was achieved through four contracts awarded to a local contractor and through the Small Business Administration, totaling over $20 million.

As of December 2018, four of the temporary measures were completed. At that time, PREPA and the Puerto Rico Aqueducts and Sewer Authority regained water supply operations. The remaining temporary measures are expected to be completed this year.

Every aspect of the work at Guajataca, including the coordination and decision making has been a team effort between FEMA, PREPA, PRASA, USACE, and the Puerto Rico Emergency Management Agency.

“We are working hand in hand with PREPA and PRASA, communicating on a daily basis, ensuring that all the work is completed safely and on time,” said USACE’s Antilles Resident Engineer Wilmel Varela. “We recognize the importance that this project entails and the best way to accomplish it is as one team.”

In order to manage the risk of catastrophic dam failure while being repaired, USACE recommended PREPA to maintain the reservoir’s water levels throughout the repairs at 192.5 meters during the wet season and 194.25 meters for the dry season. However, the reservoir levels never exceeded the 193 meters due to the local weather conditions and low precipitation during 2019 dry season.

As FEMA’s technical advisor and construction agent USACE will continue making recommendations with the objective to protect lives of the population downstream of the dam and the integrity of the dam’s infrastructure. PREPA and PRASA remain responsible for making determinations and working with local authorities to inform the public regarding the amount of water discharged from the reservoir. As the reservoir’s owner, PREPA manages the dam and the raw water distribution to PRASA’s treatment plants. Meanwhile PRASA is in charge of treating the raw water and for supplying potable water to its customers. USACE executes its functions, per operational procedures and requirements of both agencies.

Failure of the Guajataca Dam would be catastrophic for the health and safety of the local population and for the economy of the North West area and Puerto Rico in general. For this reason PREPA has notified USACE that it is one of its top priorities to evaluate the integrity of the dam system to determine the additional work required to proceed with permanent repairs without any delays once the temporary measures are fully implemented. PREPA requested USACE’s assistance to perform a risk analysis of the dam and all necessary studies to develop plans and specifications to construct a permanent solution.

“USACE is committed to continue supporting PREPA with the implementation of permanent repairs and bring the dam to current dam safety standards,” said Jacksonville District’s Lead Engineer for Dams and Levees Daniel G. Blaydes.

Due to all the information required to gain a clear understanding of the existing dam conditions, the implementation of permanent repairs has been divided in three phases. This will help determining the most efficient way to, not only increase resilience, but also meet best industry practices and dam safety criteria consistent with the USACE’s design methodologies.  

The first phase will comprise all necessary studies and investigations with a detailed risk analysis on the actual conditions of the dam and alternatives to solve any deficiencies identified in the studies. The second phase will consist of the preparation of plans and specifications incorporating identified alternatives. The third phase will include the construction of the permanent solutions.

It is estimated that the cost for all the repair work will be in the hundreds of millions of dollars. At this moment FEMA is in the process of establishing a mechanism to partially fund the first phase.

The work at the Guajacata Dam is one of the many flood control projects that the USACE is executing throughout the Island. The USACE has extensive flood control experience in Puerto Rico, including the construction of the Portugues & Cerrillos Dams, multi-million dollar projects, to reduce impact of flooding in Ponce from the Portugues and Bucana Rivers.

“The Corps has very capable, knowledgeable, and committed workforce,” said Jacksonville District’s Project Manager Brenda E. Calvente. “We are proud and honored to be a part of this effort and to continue finding lasting solutions that will benefit Puerto Rico.”

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