Read this paragraph that I got fromt he above link and you'll see where I came up with what I qouted about the welder certification. I wouldn't think that they would want unqualified welders welding on these things.
Workmanship and Welding Quality Requirements
Weld design, preparation, procedures, materials, and quality shall conform to ANSI/AWS D14.3-94 and ANSI/AWS D14.4-97.
Welded joint design shall be per ANSI/AWS standards as described in referenced publications.
Although certified welders are not required, it is expected that the final weld quality will be equivalent to a weld made by a certified welder.
Table A includes common symbols used on State of California Division of Equipment Drawings. Weld drawing symbols conform to ANSI/AWS standards and weld details.
The State of California Quality Assurance Inspection will conform to the guidelines and recommendations covered in AWS publication B1.11:2000 Guide for the Visual Examination of Welds.