Draft memo forwarding thread, April 2002

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o 1. Evaluate data, including trends over time Lower limit for air considers detection limit and 1/10 ■D c o NIOSH REL CT o o' Ca5 Settled dust 2. Evaluate need to warn sensitive group (people ■D CD O tn >5% crystalline with breathing problems) 3. ro 03 silica 3. Identify source and take action to reduce levels o o o and below 6 ;zg/m’ c 3 CD

Air 4. Evaluate dust loading and silica content to 6 to 49 /zg/m’ determine if dust clean up is needed

5. Resample after actions have been take, or if no action, continue to monitor to confirm elevated levels 1. No restrictions on access to any area Respirable silica defined as silica less than 4 //m. Air Settled dust action level set as close to 1/10 NIOSH REL as > 5% crystalline 2. Evaluate dust loading and silica content to practical based on sampling methods (NIOSH 7500). silica determine if dust cleanup is warranted and Activity level, as well as dust content and loading, will Air 3. Air monitor under high activity conditions to influence air levels of silica. If air sampling was under < 6 /zg/m’ determine if there is a potential for elevated silica in aggressive conditions, this represents worse case and air due to dust content the area can be cleared. Settled dust No further actions Respirable silica defined as silica less than 4 //m. Air < 5% respirable action level set as close to 1/10 NIOSH REL as silica practical based on sampling methods (NIOSH 7500). and Air < 6 /zg/m-’

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