A scientist’s take outlines likely causes
Re “Explosions, flames, and fear” (Page A1, Sept. 14): A scientific explanation of the seemingly random gas explosions may be appropriate as a starting point in guiding an investigation. Many urban gas distribution networks are leaky. Boston is a prominent example. The explosions are probably due to leaky utility infrastructure outside the homes, not a problem inside. Buildings are efficient collectors of gases originating in the soil pore space due to a phenomenon known as the stack effect. Temperature and pressure gradient in two-story houses make this possible, drawing gas through plumbing entries and cracks in foundations and basement walls.
Normally, soils are dry enough to allow microbial oxidation of methane to carbon dioxide in the soil pore space. This is called methanotrophy. Oxygen from the atmosphere is required. A significant period of wet weather will inhibit air and oxygen penetration into the soil, causing the methanotrophs to become less efficient. Gas accumulates and leaks into houses in what seems to be a random distribution. Which houses ignite is dependent on leakiness of the nearby infrastructure as a first-order cause, then soil conditions, and finally, as the last level in the process, openings in the foundations.
The writer is a professor emeritus at the Colorado School of Mines.
Blasts viewed as a warning of what could happen elsewhere
Heads up, Mayor Walsh, Boston City Council, and all Boston first responders. A wake-up call is on the line from the northern suburbs.
While pipelines explode and neighborhoods burn in Lawrence, Andover, and North Andover, a pipeline with 750 pounds per square inch of pressure is flowing underneath a densely populated neighborhood in West Roxbury.
The pipeline ends across from an active blasting quarry. Yet the people of Boston are still waiting for their so-called safety plan.
Please heed the call.