Abstract: A light weight structural composite panel adapted for use in a vertical orientation in an underground worker protection system is disclosed. The panel comprises first and second fiberglass reinforced resin matrix facing layers and a balsa-containing core means, weights less than about 5.5 to about 6 lbs. per square foot, and when supported in a vertical plane adjacent an excavation wall, is able to withstand an extended load in Type C solid (OSHA, CFR 1926) of at least 592 pounds per square foot with a minimum safety factor of 3:1. Methods of preparing the panels and methods of assembling the panels into excavation support systems are also disclosed.