Covanta provided MoreThanTheCurve.com a statement explaining the overnight incident at its plant in Conshohocken (Plymouth Township) that resulted in a loud noise at 2:00 a.m.

Below is the statement:

Covanta Plymouth experienced a shutdown around 2 a.m. Tuesday when the main electrical breaker tripped and disconnected the plant from the grid. All plant control systems worked as designed. We are working diligently to understand why this event occurred.
 
Both combustion units and the turbine generator are designed to shut down upon a loss of power. When this happens, steam used to generate power is vented through safety valves, which causes a loud noise, much like a giant tea kettle. This noise is an unfortunate byproduct of an important safety precaution and diminishes over time as the amount of steam in the system decreases.

At Covanta our top priority is conducting our businesses in an environmentally-responsible way. We understand the concerns of our neighbors and sincerely apologize for this disruption. We are committed to fixing this issue and dedicated to ensuring that our high operating standards are upheld.  

We’ll continue to provide updates as information is available.
 
Should any neighbors have concerns or questions, we have established a 24-hour hotline and can be reached at 610-569-9372.

One thing not addressed is the smell people have been reporting today and after previous malfunctions. Covanta always denies it is the source.