NYC 9/11 Public Portal Document
Lihicrty
Mutual.
WTC INDUSTRIAL HYGIENE INFORMATION
Date: 03/07/2002
To: Bovis/AMEC - Ray Master
DDC- Bob Adams
CC: LMIG- John Rabovsky
LMIG- IH File
From: Mike Ramsey
RE: Supporting Data for H2S Continuous Monitoring Recommendation
Enclosed is supporting data for our recommendation for continuous hydrogen sulfide
measurements in trenches. This information was requested by attendees of past
safety meetings.
The table below summarizes the results of the samples collected so far.
Hydrogen Sulfide Results Summary
Total Number Total Total Above
Type of Sample Collected Detectable Limit
Time Weighted Average, Area 48 7 1
Time Weighted Average, Personal 31 3 0
Instantaneous, Direct Reading * 5 2
* The direct reading results are not in electronic format, so the total number is not
easily retrievable. Therefore, it is not being reported here.
The samples having detectable results were extracted from our database and are listed
in the attached spreadsheet.
While the number of samples above the exposure limit is small, we are detecting
quantifiable concentrations of hydrogen sulfide periodically. Because it is being
detected and because of the anecdotal reports of hydrogen sulfide odors that have
been heard from workers on the site, we believe that seepage of hydrogen sulfide into
below grade excavations is a distinct possibility.
Because of this possibility of seepage and because of the particularly dangerous
properties of hydrogen sulfide, we recommended continuous monitoring of hydrogen
sulfide during below grade work.
We will distribute this data at next week’s safety meetings along with our regular
summary of industrial hygiene measurements.
1
NYC-WTC_000149973
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