114 LIBERTY 2 OF 2

z z o o S I o o ■0 c o Page 4, Numbers 2 and 6 - These two items reference the collection of the air samples and are contradictory in the flow rate. The flow rate in o CT cn number 2 of 3 liters per minute will result in a 20-hour air sample. The flow rate in number 6 of 10 liters per minute will result in a six-hour air o’ tn "0 4^ sample, which is similar to what EPA is using. My suggestion would be to delete number 2. O O 03 Page 5, Clearance Criteria, Clearance table - Change crystalline silica in air to 1 ug/m3 and change PAHs in settled dust to a primary clearance O o value and change the value to 0.3 mg/m2. o c 3 Discussion only, not Intended to go into the document - We had discussed on the phone that the PAH number will be changing to 0.15 a> 3 mgZm2, however this has not been officially adopted at this date, so there is no documentation to support this value at this time. However, in all likelihood, this value will change during the completion of your project, which is why it is imperative that the detection limit for PAHs be set at 1 ug. This will allow us to compare the data collected at 114 Liberty to the new value and indicate compliance. In addition, ha ring a data set for PAHs with a detection limit at 1 ug will add scientific credibility to the clearance of 125 Cedar Street, which did not meet the clearance values due to detection limits and help bolster the evidence gathered at 110 Liberty by EPA.