Benchmark 3B
The Nature of Technology: Design and Systems
Grades 3-5, page 50

Even a good design may fail. Sometimes steps can be taken ahead of time to reduce the likelihood of failure, but it cannot be entirely eliminated.
 

NSES Content Standard E 
Science and Technology: Understandings about science and technology 
Grades 5-8, page 166 
Perfectly designed solutions do not exist. All technological solutions have trade-offs, such as safety, cost, efficiency, and appearance. Engineers often build in back-up systems to provide safety. Risk is part of living in a highly technological world. Reducing risk often results in new technology.