Typically, only large leaks in pipelines can be detected if there is a drop in pressure. (sciencedaily.com)
Even more disturbing than the thousands of large leaks on the street were the levels of methane in manholes. (sciencemag.org)
The following day, President Obama said «there have been varying reports over the last few days about how large the leak is, but since no one can get down there in person, we know there is a level of uncertainty. (sciencemag.org)