The second of three principle computational steps to computing energy losses through an access hole, according to the HEC-22 (Third Edition) procedure, is the summation of all additional structure losses. Total Additional Structure Losses () is the relative step increase in energy grade line from the Initial Access Hole Energy Level () up to the value of the reported Energy Grade Line (In) () at the upstream boundary side of the node.

= Initial Access Hole Energy Level. See also: HEC-22 (Third Edition) Entrance Loss.

The Total Additional Structure Losses () is the combination of all additional structure losses due to benching, angled inflows, and plunging flows through the structure:

= Additional loss for benching. See also: HEC-22 (Third Edition) Loss for BenchingHEC-22 Energy (Third Edition) – Benching.

= Additional loss for angled inflows. See also: HEC-22 (Third Edition) Loss for Angled Inflow.

= Additional loss for plunging flows. See also: HEC-22 (Third Edition) Loss for Plunging.