@A_9_9 - if you're working on a NTSDOT project you need to discuss design criteria with GEB since they will prepare the FDR. Chapter 17 of the GDM doesn't address lateral loads for pile designs of IA bridges. However, the Chapter was published in 2010 and is still considered a draft.
If it's not a NYSDOT project maybe you can convince the owner that gravity loads only are sufficient. In my office, we just did an IA bridge in NY - not for NYSDOT - but included lateral loads in the pile design. We just did a bunch of IA bridges for a design-build proposal for NYSDOT and the geotechs included lateral loads.