structure, and the nature of the intended interventions. The underlying principle is that no harm is done to the structure in the course of the intervention which would damage the structure or make it unavailable to future generations. In addition, it is important that the historic portions of the structure be able to be understood and comprehended apart from the newer interventions. Infrastructure projects Future-proofing is also a methodology to address vulnerabilities of infrastructure systems. For example, analysis of domestic water infrastructure in the Southern California and Tijuana area completed by Rich and Gattuso in 2016 demonstrates that potential vulnerabilities include levee failures, material deterioration, and climate change. With changes in the hydrologic conditions due to climate change, there will be increased emphasis on ensuring that the water infrastructure systems continue to function after a natural hazard event where specific components or facilities in the system are compromised. Many new potable water technologies, such as desalination, physical treatment, chemical treatment, and biological treatment systems, can help to address these vulnerabilities. However, development of a future-proof infrastructure system can have longer lasting benefits. The San Diego Regional Water System has been implementing a program of infrastructure improvements to ensure plentiful water sources in the future. These include developed an emergency storage program aimed at providing a 75% service level and includes several key elements of the regional water system. The regional water authority is also in the middle of a multi-decade long project to reline the existing pipeline system to increase their service life (Water-technology.net, 2012). The region also seeks to supplement the water supply through diversification of sources of water which will support continued growth of the regional population. Priorities for development of new water sources (in order of preference) are seawater desalination, indirect potable reuse (wastewater recycling), and additional water from the Colorado River. The strategies being employed in San Diego and Tijuana are future-proofing their potable water infrastructure systems by including seismic loops and flexible oversized systems to prevent damage in seismic events accommodate future changes in use and population growth. The San Diego Regional Water System is pursuing strategies that diversify and increase redundancy of water supplies by including metropolitan water district sources, irrigation water transfer, canal lining to prevent leakage, conservation or reduced consumption, recycled wastewater, desalination, groundwater sources, and surface water sources. Development of new water tunnels and relining water mains, branches, and canals extends