Appendix F


Frequently Asked Questions


**Do all stilling wells have a confined space hazard?


No. If a stilling well does not have a confined space hazard there is no need to use the entry requirements described in this memorandum.


**How can one determine if a stilling well has a confined space hazard?


If your answer is yes to these questions, you have a confined space hazard:


·        Is the space large enough that a person can bodily enter?

·        Is the space configured so that a worker can perform work inside?

·        Does the space have limited or restricted means for entry or exit? (For example:  Only one way in and one way out.)

·        Does the space have the “potential” to contain a hazardous atmosphere?

·        Does the space contain a material that has the “potential” for drowning) an entrant?


**I am uncertain if a specific stilling well has a confined space hazard or not.  What should I do?


Contact your Regional Safety Officer for an evaluation.


**How do I fix physical hazards in the stilling well if it is required that all hazards be eliminated before entry.


Eliminate all hazards that do not require entry first, then perform atmospheric tests.  If atmospheric tests indicate no hazards, provide forced air ventilation and enter the well to resolve any physical hazards.


**Do I need to provide safety evaluations and atmospheric tests annually even if it may not be necessary to enter the stilling well for three years?


No.  Safety evaluation need only be performed 12 months prior to entry or just before entry.  If entry isn’t required over a several year time span, the safety checks and atmospheric testing is only required just before entry.


**It has been 13 months since the last safety evaluation and atmospheric test.  Do I need to repeat the safety evaluation and atmospheric tests prior to entry?




**If a stilling well failed an atmospheric test in 1999, but subsequent atmospheric tests in later years fail to identify the hazards again, do I need to continue completing the more strict entry requirements?


Yes.  Intermittent atmospheric hazards constitute a significant hazard.  However, if the cause for the hazardous atmosphere can be positively identified and eliminated, send the documentation to your regional safety officer who will determine if it is ok to step back to the general entry requirements.


**I’m using a propane heater to warm a stilling well in the winter. I need to enter the stilling well for five minutes or less.  Do I need to complete the strict entry procedures?


Yes. Using propane heaters in the confined space of a stilling well is very hazardous.


**Do I need to use forced air ventilation every time I enter a stilling well?


Yes, if the stilling well has a confined space hazard.


**Should all gaging station structures, that have AC electrical power, have Ground Fault Circuit Interrupter (GFCI) devices installed?


Yes. GFCI devices provide considerable protection from electronic shock at a very low cost. 


**It has been reported that high humidity in some gaging station locations may be causing the GFCI device to trip causing lost record. Are their alternatives to using GFCI devices in all gages?


A very cautious yes. It is recommended that in situations where GFCI devices seem to be tripping unexpectedly, additional efforts be made to identify other factors that may be causing the device to trip. Battery backup can be used to prevent record loss. If GFCI devices continue to trip unexpectedly, contact your regional safety officer who can help identify alternatives to protect field personnel from electrical shock hazards. 


**If the use of a stilling well is discontinued, does this mean the structure must always be removed?


No.  The structure can continue to be used as an instrument shelter as long as modifications are made to ensure personnel can never enter the stilling well.


**I need to enter a non-USGS stilling well operated by a cooperator.  DO I still need to follow the new guidelines?


Yes, if there is a confined space hazard.


**A cooperator wishes to enter a USGS stilling well with a confined space hazard.  Does the cooperator need to follow the new guidelines?