WAY OT - chemical engineering questions *LINK*

Re: WAY OT - chemical engineering questions

Frank Martin (Chicago, IL)

>Bill,

I am an environmental enginner by training, but now practising consulting in a different area. However, I have professionally dealth with situations very similar to what you are describing.

I only briefly skimmed through the report you provided the link to.

First, I think you should be happy that they are putting in a remediations system. If they put it in place carefully and operate diligently, it sure will reduce the contaminant levels.

Precursor organics refer to the weathered gasoline in the ground (soil and groundwater). They are called precursor, because over time they degrade into other compounds which may even be more toxic than the "precursor" compounds.

In terms of your other question 1.6E-2 = 0.016. The ambient levels of these compunds would be zero in uncontaminated environments. However, the law is such that the target concentrations for remediation are calculated based on the risk they pose to human health (that is the reference in the engineer's report about 10 in one million risk). This is because there are some practical limits to how far you can reduce contaminant concentrations. Think of it this way, if it costs $100 to remove 99% of contamination, it may cost $1000 to remove 99.5%.

Hope this helps a bit. If you have other questions, feel free to post them and I will do my best to respond.

Re: WAY OT - chemical engineering questions

Jim in Houston, Texas

>I'm not sure which precursors the report is referring to, but I believe that 1.6 E-2 is actully .016 which is ten times greater than your figure above. It would seem that if there were a leak then the chemicals entering the environment would be products from the breakdown of the gasoline rather than precursors to the gasoline. Maybe it's two ways of saying the same thing.

I am not now nor have I ever been a Chemical Engineer though I was a Chemistry teacher in a former incarnation....

Re: WAY OT - chemical engineering questions

Scott in Douglassville, PA

>As noted above, the E-02 gives you a number ten times higher than you had (my eyes need fixin'). Precursors to benzene (defined as "toxics" in the report) would be cyclohexane, or any number of benzene-derivatives (that is, compounds derived from benzene). Toluene and xylene are in this group. The chemistry involved to convert the cyclic alkanes or organics to benzene are different, and may or may not be likely. Think all of these can be found in gasoline, though it's not my area.

less than active gas station will produce

bill tindall

>If this gas station is an on going business there will be (or there were) a lot more gasoline vapors than that coming from tank filling.