Building code (IRC R401.3) requires the site grading to direct water away from the foundation. Where space is available the ground should drop a minimum of 6" in 10' in a direction perpendicular to the foundation. If this is not possible due to adjacent property lines or other obstructions, swales or a drain system may be used to convey water away from the foundation. These are the minimum prescriptive building code requirements. The engineer that designed the foundation may have grading requirements that are more stringent than the IRC requirements.