fossil fuels, all of which are imported. The electricity sector is run by PREPA, a government run agency that owns the transmission and distribution infrastructure as well as ~ 85% of the main island’s generating capacity (U.S. Energy Information Administration 2018). In September 2017, Hurricanes Irma and Maria hit Puerto Rico and caused severe damage to all critical infrastructure, including the power grid. These events provide ideal case studies for understanding the impacts that a hazard can have on power infrastructure including: asset-level damages, interdependencies within the electricity grid system and with other critical infrastructures, the impact of supply chain disruptions, considerations for planning and policy, and the costs of building back better.

Hurricane Irma was a Category 5 storm that made landfall on September 6, 2017, and left 70% of electricity customers without power and damaged critical infrastructure (Campbell, Clark, and Austin 2017; New York Power Authority et al. 2017). On September 20, 2017, Hurricane Maria made landfall in Puerto Rico as a Category 4 storm with wind speeds of over 250 kph (Campbell, Clark, and Austin 2017). These storms caused catastrophic damage, especially to the electrical grid (Central Intelligence Agency 2018). Hurricane Maria brought torrential rainfall with a range of 38 to over 100 centimeters, resulting in widespread flooding across the island (Campbell, Clark, and Austin 2017). The northern coast was severely impacted as the rotation of the hurricane led to severe coastal storm surge, which coupled with major rain runoff from the central mountains resulting in sustained flooding (New York Power Authority et al. 2017). The damage was so extensive that even undamaged generators could not supply power (U.S. Energy Information Administration 2018). The damage resulted in electrical power outages to 90% of the island as well as loss of housing and infrastructure and contamination of potable water (Central Intelligence Agency 2018).

Puerto Rico’s Office of Emergency Management reported that the storms had incapacitated the central electric power system, decimating transmission and distribution lines across the island and caused widespread wind and flood damage to substation, distribution, and generating facilities (Campbell, Clark, and Austin 2017; New York Power Authority et al. 2017). Hurricane Maria was the worst storm to hit the island in over 80 years, and the cost of the damage is estimated in the tens of billions of dollars (Central Intelligence Agency 2018). The request for disaster recovery funds, submitted by the Governor of Puerto Rico Ricardo Rossello in November 2017, totaled just under a trillion dollars. The second largest category in this request, behind housing, was for nearly at nearly $18 billion to restore the power grid and increase resiliency (R. Rossello 2017).

Much of the island’s electricity is generated at power plants on the southern coast, while the largest population centers are in the north, making the system highly dependent on its 2,400 miles of transmission and 30,000 miles of distribution lines in the island’s forested, central mountain range (U.S. Energy Information Administration 2018). Due to staffing shortages at PREPA, no one had been cutting back the jungle growth on these south to north transmission lines (Ferris 2018). As a result, the combination of long distances, inaccessibility, and wind and tree damage led to a near total wipeout of the electricity grid when Hurricane Maria hit (Ferris 2018). In particular, transmission lines and towers in the center of the island were severely damaged by high winds that were funneled through changes in the terrain (New York Power Authority et al. 2017). In all, approximately 101 transmission line segments, 636 poles, and 673 conductors/insulators were damaged by the storm, Table 16 (New York Power Authority et al. 2017).

In early October 2017, only 20% of all transmission lines in Puerto Rico were functioning (Ferris 2018). Steep hills and muddy slopes in the north-south corridor made access to damaged transmission lines difficult, leading to repair times lasting up to a year in some locations (New York Power Authority et al. 2017). Virtually 100% of PREPA customers did not have power for over a week following the storm, and this slow pace of recovery meant that many customers were left without power for several months (U.S. Department of Energy 2018a).

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