There is a great article by Mark Vessely that touches on issues of acceptable risk in the context of retaining walls (and all geotechnical assets), the potential for a growing problem in our industry, and what owners and geotechnical engineers can do about it.
He talks about an experiment he did last summer to monitor the news for retaining wall failures and came up with a particular incidence rate and poses the question if that rate of failure is acceptable. And he also extends that line of thinking to the likely possibility that that rate will accelerate as our infrastructure continues to age and we continue to add new walls to our “inventory”. It is definitely worth the read. Mark is the author or co-author of several geotechnical asset management publications for the FHWA and Transportation Research Board.