2. GENERAL GUIDELINES TO ENTER STILLING WELLS
3. GUIDELINES FOR STILLING WELLS THAT FAIL ANY ATMOSPHERIC TEST
A. Stilling Well Entry Sign
B. Stilling Well Safety Evaluation Form
C. Example of a Job Hazard Analysis
D. Summary of Basic Entry Requirements for Stilling Wells
E. Summary of Entry Requirements for Stilling Wells that have Failed any
F. Frequently Asked Questions
This safety policy and set of guidelines establishes specific safety standards and safe work practices for all WRD stilling well operations that meet OSHA’s definition of confined space. A confined space is a space that is large enough and so configured that an employee can bodily enter and perform assigned work, has limited or restricted means for entry or exit, and is not designed for continuous employee occupancy.
Field personnel, supervisors, and managers are all responsible for safety in the workplace (Executive Order 12196, “Occupational Safety and Health Programs for Federal Employees” and OSHA regulation 29 CFR 1960). “Basic Program Elements for Federal Employee Occupational Safety and Health Programs and Related Matters” require that supervisors and managers be responsible and accountable for correcting existing and potential hazards, and for providing a safe and healthy workplace and working conditions. It is, therefore, the responsibility of managers and supervisors to ensure that the safety procedures and guidelines prescribed in this document are followed for all stilling wells that meet OSHA’s definition of confined space.
2. GENERAL GUIDELINES TO ENTER STILLING WELLS
A. Provide engineering solutions to reduce the need to enter the stilling well. for example, an electric tape can be used to measure water levels in the stilling well rather than entering the well to read a staff gage.
B. Place a sign at every entry to the stilling well: “Safety Hazard Unauthorized Personnel DO NOT ENTER" (example provided in Appendix A). Cooperators or other non-USGS personnel visit many USGS gaging stations. The purpose of the sign is to warn everyone who may have access to the stilling well that there is a hazard and they should not enter.
C. Conduct a safety evaluation of the gaging station stilling well. Safety evaluations should be conducted either annually or just prior to entry. Personnel who conduct the safety evaluation for both physical and electrical safety hazards must have the necessary experience and skills needed to complete the evaluation. Personnel who conduct the atmospheric tests need to be trained to calibrate and use the instrumentation. Safety evaluation guidelines are described below:
1. Document the number of years the stilling well has been safely entered. Review historic safety evaluations/incidents to help identify potential safety concerns.
2. Evaluate and eliminate all identified physical hazards.
a. Are ladders safe? Is fall protection needed? Fixed ladders require a safety
device if they are more than 20 feet high (29 CFR 1917.118).
b. Objects such as tools, shovels, sounding weights, nitrogen tanks, etc.
that could fall into the stilling well should be secured or removed. Personal
protective gear (hard hat, rubber gloves, eye protection, etc.) must be
available and used as appropriate.
3. Evaluate and eliminate all identified electrical hazards.
a. All AC electrical circuits in gaging stations and stilling wells must be protected by a Ground Fault Circuit Interrupter (GFCI) device.
b. Electric power tools used in stilling wells must be double-insulated or
connected to a GFCI circuit.
4. Evaluate and eliminate all identified biological hazards such as sanitary concerns, snakes, wasps, mice (hantavirus), bats (histoplasmosis), etc.
5. Measure and verify that oxygen and carbon monoxide concentrations in the stilling well are safe (before mechanical ventilation).
a. Before entry into any stilling well, open all doors and vents for a minimum of five minutes. Doors should always be secured in the open position to prevent inadvertent entrapment. Measure the atmosphere in the stilling well near the expected breathing zone of an entrant.
Oxygen concentration is acceptable if it is between 19.5% and 23.5%.
Carbon monoxide concentration is acceptable if it is 0 to 35 PPM.
6. Determine if there are other potential atmospheric concerns in the stilling well in addition to carbon monoxide and oxygen. All potentially hazardous atmospheric conditions must be evaluated and determined to be safe (before mechanical ventilation). For example:
a. Propane heaters in stilling wells can create very dangerous confined space
The propane may leak, displacing oxygen.
The propane may leak, creating an explosive hazard.
The propane heater may burn inefficiently, creating carbon
The propane heater may consume the oxygen in the stilling well.
If propane heaters are used, the entry procedures for stilling wells that fail any atmospheric test, described later, must be used.
b. If there is considerable organic debris in the bottom of the stilling well, carbon dioxide may be displacing oxygen.
D. The results of the stilling well safety evaluation for physical, electrical, biological, and atmospheric hazards must be documented. An example of a form used to document the safety evaluation is included in Appendix B. Documentation should be filed in a manner that will allow field personnel easy access. The Stilling Well Safety Evaluation provided in Appendix B (excluding the atmospheric testing section) can also be used as a quick safety checklist prior to every entry.
E. A Job Hazard Analysis (JHA) that describes the hazards and the required safe entry procedures for working in stilling wells must be completed. The JHA should include a plan for emergency help such as phone numbers for rescue and medical help. Supervisors will discuss the JHA and safe entry procedures with every employee who may enter a stilling well. The JHA should be placed in the field folder for that gage. An example of a JHA for a stilling well with a confined space hazard is provided in Appendix C.
F. After steps A-E have been completed, provide mechanical ventilation, such as a portable blower, to supply fresh outside air into the stilling well during every entry. The blower should be able to supply enough fresh air to replace the total volume of air within the stilling well three times each minute. The fresh air exhaust duct from the blower should be placed near the water surface in the stilling well. Exhaust from gasoline or propane powered sources must be vented downwind and down gradient from the stilling well and the mechanical blower, to prevent accidental introduction of contaminated air in the stilling well.
A summary of these General Entry Requirements is provided in Appendix D.
3. guidelines for Stilling wells that fail any atmospheric test
If any atmospheric test is unacceptable, it is recommended that the use of the stilling well be discontinued and alternate methods to measure stage be used.
If entry into a stilling well that has failed any atmospheric test is needed, significantly more restrictive entry procedures must be used. These entry requirements must be used every time the stilling well is entered during the life of the stilling well:
A. Use the General Guidelines for Entering Stilling Wells outlined in steps A – E above. In addition:
B. Require a minimum of two people, an entrant and an attendant, every time the stilling well is entered.
C. Provide mechanical ventilation, such as a portable blower, to supply fresh outside air into the stilling well during entry. The blower should be able to supply enough fresh air to replace the total volume of air within the stilling well three times each minute. The fresh air exhaust duct from the blower should be placed near the water surface in the stilling well. Exhaust from gasoline or propane powered sources must be vented downwind and down gradient from the stilling well and the mechanical blower, to prevent accidental contamination of air in the stilling well.
D. Measure the stilling well atmosphere near the expected breathing zone of the entrant
during mechanical ventilation for oxygen, carbon monoxide and any other atmospheric
hazards identified as part of the safety evaluation.
Oxygen concentration is acceptable if between 19.5% and 23.5%.
Carbon monoxide concentration is acceptable if between 0 to 35 ppm.
If propane is used to heat the stilling well during the winter:
1. The propane must be turned off prior to entry.
2. The first atmospheric test must be for oxygen concentration (most
combustible gas meters will not provide reliable readings in an oxygen-
3. The next atmospheric test must be for combustible gas.
Combustible gas is acceptable if below 10% of Lower Explosive Limit.
4. The next atmospheric test should be for carbon monoxide concentration.
If any atmospheric measurement is unacceptable, even with mechanical ventilation, do not enter. This stilling well must be treated as a "Permit-Required Confined Space." Contact your Regional Safety Officer for further instructions.
E. If all atmospheric measurements are acceptable, continue to mechanically ventilate the
stilling well and enter the well. The attendant will continuously monitor the stilling well
atmosphere, near the breathing zone of the entrant, from outside the stilling well. If
atmospheric monitoring indicates unsafe conditions, the entrant must exit the stilling well immediately.
A summary of the entry requirements for stilling wells that have failed any atmospheric test is provided in Appendix E. Answers to frequently asked questions are provided in Appendix F.