Confined Space Entry at a Wet Well with a Rising H2S Reading

Stop the entry. Nobody goes down that ladder on the current setup, and any crew member has the authority to say so.

Why, specific to this scene:

• H2S rose 12 ppm in three minutes with no ventilation. The trend, not the 26 ppm number, is the danger - it can keep climbing past 100 ppm, which is immediately dangerous to life and health. H2S also deadens the sense of smell in the tens of ppm, so the operator cannot smell his way out.
• 20.1% O2 is acceptable at the top, but that reading was taken at grade. Wet wells consume oxygen at depth and the working-level reading is unknown.
• 0% LEL only rules out flammable gas at that moment; it does not clear the space.
• A half-mask respirator provides no protection in an oxygen-deficient atmosphere and is not adequate for H2S at an unknown concentration.
• Administrative failures: no permit, no ventilation, no attendant at the entry, no retrieval system, and a rescue plan that cannot arrive in time. Rescue is the leading cause of confined-space fatalities, and would-be rescuers are the most common victims.

Right now: secure the area, keep the meter running and logging, call a supervisor, and see whether the clog can be cleared without entry - vacuum or jet from grade, or bypass pumping - so the entry becomes unnecessary.

Eliminate first, then engineer the entry:

1. Forced-air ventilation for at least 15-20 minutes, then re-test at the entry point and at the working depth - not just at the top.
2. Acceptable atmosphere: O2 between 19.5% and 23.5%, LEL below 10%, and H2S below 10 ppm (use 10 ppm as a ceiling; many programs use 5 ppm as the action level). If H2S will not come down, the entry requires supplied air or SCBA and is treated as an IDLH-capable job.
3. Continuous monitoring with alarms, by a meter that was bump-tested and calibrated that shift, worn by the entrant or the attendant at the entry.
4. Attendant stationed at the opening who never leaves, with communications; retrieval system (tripod, lifeline, full-body harness) rigged before entry.
5. Trained entrant, attendant, and entry supervisor; a signed permit posted at the site; lockout and isolation of any equipment; fall and traffic protection.
6. A rescue plan with a competent rescue service that can actually reach the site. If the named department is volunteer and 25 minutes out, get a written agreement and confirm they are trained in confined-space rescue - or stage a trained rescue team on site. If you cannot, entry is not allowed.

Judgment point: verify rescue capability before the permit is signed, not in the plan binder after an incident.

Regulatory/reporting:

• If the clog caused or threatens a sanitary sewer overflow, notify the state promptly - SC generally requires notification within 24 hours of becoming aware - followed by a written report as specified in the NPDES/SSO permit. Photograph the site, record volume and receiving water, and the corrective action. Confirm the exact deadline in your permit.
• OSHA: a recordable injury goes on the 300 log within 7 days; a fatality must be reported within 8 hours, and an in-patient hospitalization or amputation within 24 hours. A near-miss alone is not recordable, but it must be investigated.
• Pull the four-gas meter calibration and bump-test records - a meter that was not bumped is not evidence of anything.

Internal: near-miss/stop-work report the same night, with the readings, timeline, and who made the call. Thank the person who stopped it, publicly.

Program changes:

• Pre-job hazard review for every wet well, with a required meter reading at the entry point.
• Blowers, tripods, harnesses, and retrieval lines on every truck.
• Refresher training on H2S physiology and on the half-mask limitation.
• A written rescue agreement with a measured response time you can defend.