A new retaining wall at a rental property would it be considered 5, 15, 27.5 year?

See https://www.irs.gov/publications/p527#en_US_2022_publink1000219075

15 years, same as fences, roads, misc. hard surfaces (land improvements).

Duplicate post

is a retaining wall replacement depreciation  be 275 years or 20

neither under the GDS (MACRS) system land improvements are 15 years. 

if you select land improvements as the type Turbotax should automatically use 15 years 150%db