Safety, security, and emergency preparedness
Safety, security, and emergency preparedness questions test whether you can keep workers alive and keep water flowing during a crisis. Expect confined spaces, chlorine hazards, lockout/tagout, hazard communication, security, and emergency response plans.
Core rules
- Confined spaces require a permit, atmospheric testing before entry and continuously, an attendant, and a rescue plan. Acceptable entry: oxygen 19.5–23.5%, flammable gas below 10% LEL, and hydrogen sulfide below 10 ppm unless stricter limits apply.
- Never enter a space to rescue an unconscious worker without SCBA and backup. Call 911 and use non-entry rescue first.
- Chlorine gas is heavier than air and highly toxic. Evacuate upwind, use SCBA, and do not re-enter until the area is tested and ventilated.
- Lockout/tagout isolates energy sources before repair. HazCom requires labels, SDS access, and training for chemicals such as chlorine, fluoride, and coagulants.
- Security: lock gates and buildings, control keys and SCADA access, and report suspicious activity.
- Community water systems serving 3,300 or more people must complete a risk and resilience assessment and emergency response plan under AWIA and update them every five years.
Worked example: confined space
A meter reads 19.2% oxygen, 8% LEL, and 3 ppm H2S. The LEL and H2S are acceptable, but oxygen is below 19.5%. Entry is prohibited. Ventilate the space, retest from outside, and do not enter until oxygen is at least 19.5% and all other readings are acceptable. If the meter later reads 20.9% oxygen, 0% LEL, and 0 ppm H2S, entry may proceed under the permit with continuous monitoring.
Traps
Treating 19.5% oxygen as a target rather than a minimum; using a meter without calibration; entering to rescue; forgetting the attendant; and writing an emergency plan that is never practiced.