Economics of Seismic Retrofit of Water Transmission and Distribution Systems

One way to gage the need for seismic retrofit of water systems is to examine the case evidence as to how much has been already spent on such endeavors. In the United States, there are more than 10,000 individual water system operators. Of these, perhaps a few dozen or so have embarked on some sort of system-wide seismic retrofit. This is not to say that the other water utilities have ignored seismic issues: in fact, the vast majority of water system operators follow codes like the UBC 97 for design and construction of new buildings. But the fact of the matter is that much of the water infrastructure currently (year 2003) in place has been designed and constructed either to no seismic standard (as is the case for 99.9%+ of all buried water pipelines and redwood tanks); out-dated seismic standards (as is the case for most pre-1973 steel and concrete tanks); arguably inadequate seismic standards for steel and concrete tanks built post-1972 in high seismic regions; lack of attention to seismic detailing for many types of non-structural items such as anchorage of motor control centers, restraint of emergency generator batteries, use of vibration isolators for diesel generators and air compressors, use of flexible suspended tbar ceilings over operator work areas, lack of restraint of glassware and equipment in water quality laboratories, etc. About the only type of component that is consistently built to relatively good seismic standards are building structures, likely because the UBC (and similar) codes of the past many years are reasonably good and quite rigorously followed.