"Ziman, Steve (SDZI)" 02/22/02 05:39 PM To: John Silvasi/RTP/USEPA/US@EPA <> John, Good to talk to you today. I am sending this to you because it reflects some of the real concerns with use of modeling to develop a comprehensive strategy based on few episodes. While the topic is measurements, this first idea is discussed in the second paragraph. Moreover, given that it is a document from the San Joaquin Valley Technical Committee, it is a document that reflects industry and agency thinking at a technical level. And finally, it may reflect on the idea suggested in option 3 of the Holmstead memo. Trying to set classification status based on modeling is extremely questionable. I should note from our conversation this morning that we have seen here that solving for the worst episodes may have little or even adverse effect on less episodes, based on a lot of data analysis (which for looking at episodes is a lot more robust than modeling one, two or a few). So good luck, but this is going to be a difficult problem Steve Ziman, Ph.D Senior Staff Scientist Air Issues; Health, Environment and Safety Group Chevron Research and Technology Co. 100 Chevron Way Richmond, California 94804 sdzi@chevrontexaco.com phone: 510-242-1530 fax: 510-242-5577