I'm analyzing a 34" line at onshore gas terminal and here are a few basic questions regarding applying wind loads to my pipeline model:

1. What's the minimum height of pipeline that need to consider windloads factor?

2. I try to use ASCE#7 Wind Load Parameters but my Basic Wind Speed is only 18 m/sec. I received a message saying that my Basic Wind Speed must be at least 31.29 m/sec. Does that means i do not need to apply windloads since my Basic Wind is less than 31.29 m/sec? Is there any publication to support this?

3. On Topographic Factor Parameters, what is a "Crest"? and what is "Escarpment"? Can anyone sketch me a "Crest" and "Escarpment" for better understanding?