Part Per Billion

Did you know that many cleanup objectives for soil and water are measured in parts per billion (ppb) or, in some cased, parts per trillion (ppt)?  For example, the New York State Groundwater Standard for benzene is 1 ppb.  But how do you ‘envision’ one part per billion?  Think of it this way: one part per billion is equal to one second in 32 years!  Looked at another way, 4 drops of liquid in a 50,000 gallon tank would equal one part per billion.