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Sewer entry differs in three vital respects from other permit entries;first, there rarely exists any way to completely isolate the space (a sectionof a continuous system) to be entered; second, because isolation is notcomplete, the atmosphere may suddenly and unpredictably become lethally hazardous (toxic, flammable or explosive) from causes beyond thecontrol of the entrant or employer, and third, experienced sewer workersare especially knowledgeable in entry and work in their permit spaces because of their frequent entries. Unlike other employments where permitspace entry is a rare and exceptional event, sewer workers' usual workenvironment is a permit space.
(1) Adherence to procedure. The employer should designate as entrants only employees who are thoroughly trained in the employer's sewer entry procedures and who demonstrate that they follow these entryprocedures exactly as prescribed when preforming sewer entries.
(2) Atmospheric monitoring. Entrants should be trained in the use of,and be equipped with, atmospheric monitoring equipment which soundsan audible alarm, in addition to its visual readout, whenever one of thefollowing conditions is encountered: oxygen concentration less than 19.5percent; flammable gas or vapor at 10 percent or more of the lower flammable limit (LFL); or hydrogen sulfide or carbon monoxide at or abovetheir permissible exposure limit (PEL) (10 ppm or 25 ppm, respectively,measured as an 8-hour time weighted average (TWA)). Atmosphericmonitoring equipment needs to be calibrated according to the manufacturer's instructions. Substance specific devices should be used wheneveractual contaminants have been identified. The instrument should be carried and used by the entrant in sewer line work to monitor the atmospherein the entrant's environment, and in advance of the entrants' direction ofmovement, to warn the entrant of any deterioration in atmospheric conditions. Where several entrants are working together in the same immediate location, one instrument, used by the lead entrant, is acceptable.
(3) Surge flow and flooding. Sewer crews should develop and maintain liaison, to the extent possible, with the local weather bureau and fireand emergency services in their area so that sewer work may be delayedor interrupted and entrants withdrawn whenever sewer lines might besuddenly flooded by rain or fire suppression activities, or whenever flammable or other hazardous materials are released into sewers during emergencies by industrial or transportation accidents.
(4) Special Equipment. Entry into large bore sewers may require theuse of special equipment. Such equipment might include such items asatmosphere monitoring devices with automatic audible alarms, escapeself-contained breathing apparatus (ESCBA) with at least 10 minute airsupply (or other NIOSH approved self-rescuer), and waterproof flashlights, and may also include boats and rafts, radios and rope stand-offsfor pulling around bends and corners as needed.
Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.