Passive alarm to prevent buried infrastructure damage

Abstract

A method and apparatus are disclosed for preventing excavation damage to buried infrastructure. A plurality of excavation-sensing modules is buried near the buried infrastructure. The modules protect buried infrastructure by emitting dense clouds of highly visible gas when the modules are activated by impact with excavation equipment. In most cases the visible gas will be brightly colored and it may also have a strong odor and may produce a loud sound when the module is activated. The dense clouds of highly visible gas, the optional odor and loud sound alert construction crews or other workers that their excavation is nearing a protected underground structure. Once installed, no maintenance or active monitoring is required. In a preferred embodiment of the excavation-sensing module, the dense cloud of highly visible gas is produced by ignition of a smoke grenade within the module. In the preferred embodiment, the smoke grenade is ignited by the interaction of the excavator striking and breaking the buried module. Also in the preferred embodiment, the excavator will normally pull the ignited smoke grenade out of the buried module and to the surface increasing the visibility of the gas. Also in the preferred embodiment, a more reliable design for ignition of the smoke grenade is disclosed.