The primary purpose of the Survey Control Network is to provide a series of horizontal and vertical reference points, on a uniform datum, which spans the entire length of the project alignment. Since NGS has previously released information documenting this region as a subsidence area (meaning that these monuments are subjected to downward motion over time), and in an effort to maintain consistent elevations throughout the project alignment it is necessary to periodically adjust the SCN throughout the system alignment. Therefore, the TLCD, every few years performs a static survey of 15 monuments throughout the project alignment and adjusts the elevations to the updated network. The survey benchmarks of the SCN were observed using redundant static GNSS (GPS) observations and processed with GNSS observations from Continuously Operating Reference Stations (CORS) maintained by NGS and the LSU Center for Geoinformatics (C4G).