specific documents, estimates were made using equivalent U.S. based design structure and components.

A final consideration for resilient infrastructure design is the incremental design costs relative to the probability that an event occurs over the lifetime of the infrastructure. While a full analysis of the power grid infrastructure in Puerto Rico and occurrence of hurricane-level storms is outside the scope of this paper, Table 17 provides an estimate based on historical storm occurrences since 1901. More detail is provided in Appendix D and E. Taken together, this information lays a foundation for a probabilistic risk assessment and cost-benefit analysis of different infrastructure investment decisions and is an area for future work.

Table 17: Summary statistics for windspeed events occurring in Puerto Rico, 1901-Present. Data for windspeed recorded in one-minute sustained wind speeds at approximately 100 meters above ground elevation. (For details on calculation, see Appendix E). _Data from:_ <u>National Centers for Environmental Information (2018)</u>

||Top Windspeed<br>for Category<br>(miles/hour)|Top Windspeed for<br>Category (km/hour)|Annual Prob.<br>Of 1 event|Number of<br>Storms since<br>1901|
|---|---|---|---|---|
|Tropical Storm|40-74|63-118|10.6%|14|
|Hurricane-Category 1|74-95|119-153|2.5%|3|
|Hurricane-Category 2|96-110|154-177|2.5%|3|
|Hurricane-Category 3|111-129|178-208|0.8%|1|
|Hurricane-Category 4|130-156|209-251|2.5%|3|
|Hurricane-Category 5|>156|>251|0.8%|1|

# **5.0 – SUMMARY OF FINDINGS**

# 5.1 – Power Grid Infrastructure

Generation plant vulnerabilities were the broadest area in our case studies. However, the data do suggest specific guidelines about resilience (or lack the of) of specific power generation systems (fuel types) in the context of specific hazards. For example, in Section 4, the performance of 4 solar photovoltaic farms in Puerto Rico are detailed to show how the design parameters of a system define the impact it sustains from a hurricane event. Similarly, in Section 3.1.3, transmission and distribution investments totaling $6 million made in New Zealand for higher seismic design standards are estimated to have saved Orion an estimated $30-50 million in direct asset replacement costs during the 2010-2011 earthquake events <u>(Fenwick and Hoskin 2011). In this context, an important finding is that more robust design standards</u> (such as a higher design threshold for wind speed) is directly related to performance during and after a hazard event. A next step in assessment would be to calculate the relative incremental cost of a more or less robust asset design and both the dividend in terms of performance in a hazard situation and the resilience dividend<sup>5</sup> .

> 5 The resilience dividend is defined as the value of more resilient infrastructure _in the absence_ of the event it is designed for. This can include things like aesthetics, job creation and performance in other events than the specific design threshold. It is similar to the idea of ‘co-benefits’, but explicitly tries to value to benefit to a community of spending more on infrastructure that is more resilient beyond the resilience to a specific event.

26