The air monitoring action levels and required response when an action
level is exceeded will be included in the Work plan if contaminants of
concern are known.
General requirements for air monitoring are described below.
For organic vapors, the level of PPE will be raised from EPA
Modified Level D to Level C if the PID detects concentrations greater
than the values listed in the Work plan for the compounds suspected
to be present at the individual study areas. When insufficient information
is available to project what contaminants are likely to be present,
background measurements of organic vapor concentrations will be taken
upwind of the study area and if at any time a reading of 1
ppm above background is indicated on the PID continuously for at least
1 minute, or a reading above 2 mR/hr is detected on the radiation survey
meter, all personnel will evacuate the area until further guidance
is received from the Operation Section Chief. (The 1 ppm
action level may be superseded in the Work plan, based upon exposure
limits of known contaminants of concern). Upon receipt of notice to proceed,
PPE will be upgraded to Level C. If dusty conditions occur, or are generated
during sampling activities, appropriate respiratory protection will be
worn when performing operations where contaminants of concern may be,
or become, airborne.
If combustible gas levels at the borehole exceed 10 percent
and the alarm sounds, the area will be evacuated until the levels dissipate
and the Incident Safety Officer determines that it is safe to return
to the area. It may be necessary to flood the borehole with air or
clean water to help dissipate the combustible gases. If the combustible
gas concentrations cannot be lowered using engineering controls, the
borehole will be abandoned and a new location selected.
If the alarm is triggered on the CGI, field activities will
cease until the CGI reading is reduced to less than 10 percent of the
LEL. Although work will be conducted in the ambient environment and
no change in oxygen concentration is expected, oxygen indicator readings
less than 19.5 percent or greater than 23 percent also will be cause
to halt work and evacuate the area. The CGI will operate continuously
during activities if combustible contaminants are suspected.