Guajataca Dam Repairs PR (C)

May 2023


Guajataca Dam Repairs, PR
Puerto Rico Electric Power Authority (PREPA)
Congressional District: Puerto Rico


On 20 September 2017, Hurricane Maria caused failure of the spillway structure and damaged the water supply line and the dam outlet works. On 3 October 2017, FEMA tasked USACE through a Stafford Act Mission Assignment (MA) to avoid failure of the dam which could immediately impact approximately 1,000 people living directly downstream of the dam and cut off the water supply to over 250,000 people. USACE addressed the situation at Guajataca Dam in three stages based on risk: Stage 1, Threat of Imminent Flooding; Stage 2, Implementation of Interim Risk Reduction Measures (IRRMs); and Stage 3, Permanent Repairs. As part of Stage 1, USACE completed some limited emergency stabilization measures to prevent failure of the dam, but the spillway continued to face an unacceptable risk of failure under future flood discharge events. Therefore, USACE implemented six critical IRRMs as part of Stage 2: (1) grouting voids under the existing concrete spillway, (2) installing anchors to stabilize the spillway, (3) outlet gates repairs, and (4) water-supply line reconnection, (5) spillway and channel reinforcement, and (6) stabilization of the slopes near the inlet tower. The Stafford Act provided USACE the authority and funding to implement these six IRRMs. USACE accomplished four of the six IRRMs by the end of 2018, providing approximately a 100-year level of flood protection. The remaining two IRRMs were completed in Sep 2019 to provide approximately a 1000-year level of flood protection and further reduce risk to the general public.


Estimated Total Cost $900M to $1,1B
Estimated Federal Cost $0
Allocation thru FY22 $0
Allocation for FY23 $0
President's Budget FY23 $0



Puerto Rico Electric Power Authority (PREPA) 
1110 Avenue Ponce de Leon
San Juan, PR 00907-3802


Final inspection conducted on 12 Sep 2019. Final report and closeout documents transferred on 19 Dec 2019. The implementation of the IRRMs stabilizes the critical conditions of the dam and provides risk reduction while permanent repairs of the dam are designed and constructed. Since the overall risk of the dam is expected to remain excessively high due to hydrologic and seismic hazards. PREPA requested USACE assistance to perform a risk analysis of the dam and all necessary studies to develop plans and specifications and construct a permanent solution. The Chief’s Economy Act permits the Corps to undertake the Guajataca Dam project since project will be funded by FEMA. FEMA’s supporting letter received June 2022. USACE provided FEMA a detailed cost estimate to support and validate project cost ($550M) to negotiate project budget with PREPA. In 2022, SAJ started preparing a Memorandum of Agreement (MOA) to implement Guajataca Dam Stage 3, Final Repairs, as well as a supporting agreement for Phase I, Study and Risk Assessment, and Phase II, Design. As part of MOA coordination, the schedule and budget were updated due to the original project budget being developed in 2019. Currently, the MOA with PREPA for the Guajataca Dam under the authority of the Chief’s Economy Act is under SAD review, and it is expected to be executed by 30 Jun 23.