Environmentally Friendly & Inexpensive Underwater Blasting/Demolition Process

Focus Area



Community & Cultural Concerns, Environmental Process




Under $99k


1-2 years

Research Idea Scope

Much of the nation’s transportation system needs updating or replacing and some of this infrastructure is in-and-around environmentally sensitive marine environments. Removing underwater concrete bridge piers and rock outcroppings can either be done by slow mechanical jackhammer/sawing processes, or by quick blasting and dredging. Either demolition method has environmental consequences that must be considered and quantified for permitting processes. For bridge replacement projects, resource agencies may allow SDOTs to use blasting to quickly remove abandoned in-water piers and reduce prolonged impacts to wildlife. As a permit requirement, a complex and expensive “bubble curtain” or Blast Attenuation System (BAS) may be necessary to absorb and reduce underwater blast energy. Rather than use detonation, which creates a sonic blast wave, a less harmful demolition approach may be to use ‘deflagration’, which releases energy slightly slower and doesn’t create a sonic shock wave. Out of water, deflagration works the same way as detonation, and is capable of demolishing concrete structures and huge boulders without creating a blast wave and throwing debris. Marketing for this subsonic-blast-technology indicates that deflagration is safer in several aspects, works under 90 feet of water, and follows the same typical set-up process as regular blasting (detonation). This applied-research-study would examine deflagration technology and determine if there is potential for reducing environmental impacts and reducing project costs and complexity of blast attenuation. This study would examine if there are advantages and performance limits to deflagration and what kinds of demolition projects might benefit from this technology. In order to determine if deflagration has practical application for efficient and effective use on underwater demolition projects, input from experienced and knowledgeable blast engineers would be a primary component of this study. A final portion of this study would be to confirm and validate subsonic energy levels and work potential by capturing in-the-field underwater hydroacoustic measurement data from a reasonably representative underwater demonstration. Deflagration might have additional application for other transportation agencies that need to clear rock outcroppings near boat docks or deepen navigable waterways. In the realm of blasting science, deflagration is an established and well-known process. Would deflagration have wider application in minimizing environmental impacts, and has it been overlooked as an alternative to underwater demolition? Out-of-water, Caltrans is currently using deflagration very safely and successfully to remove huge rockslide boulders (see links below). In-water, deflagration may have been a potential alternative to blasting on the large San Francisco Oakland Bay Bridge pier demolition project that was complex and lasted over three years from 2016 to 2019. Deflagration could minimize both in-air and under-water demolition noise impacts on many forms of wildlife near demolition projects. Related links: Caltrans YouTube Video Caltrans News Flash #123 – Rockblast on SR-78 https://www.youtube.com/watch?v=k9EN1IWUDKo Caltrans News Flash #61 – Kyburz Boulder Blast https://www.youtube.com/watch?v=mB3F_6ugM48 Deflagration Technology Vendor: www.autostemtechnology.com Autostem deflagrates at 340 meters/sec – no blast wave; lower release of energy. Drill 2/3 depth of boulder; no stemming required.

Urgency and Payoff

Protects environmentally sensitive marine environments and speeds up transportation infrastructure projects. Significant reduction of environmental impacts to wildlife as well as time and money savings on marine demolition projects. Potentially much-lower environmental impacts could speedup environmental review, permitting, and approval process. Reduces the cost and complexity of mitigating construction noise impacts and reduces the duration of demolition work.

Suggested By

Bruce Rymer Caltrans / Division of Environmantal Analysis 916-653-6073

[email protected]