SAFETY - Policy and Guidelines for Surface-Water Gaging Station Stilling Wells That Meet OSHA's Definition of Confined Space 


In Reply Refer To: 
Branch of Operational Support 
Mail Stop 405 
Sunset Date:  April 2005 

                                                                        
May 3, 2000 

WATER RESOURCES DIVISION POLICY MEMORANDUM NO. 2000.10 

Subject:  Policy and Guidelines for Surface-Water Gaging Station Stilling 
Wells That Meet OSHA's Definition of Confined Space 

Many Water Resources Division (WRD) stilling wells used at surface-water 
gaging stations meet the definition of confined space as defined by Title 
29 of the Code of Federal Regulations (CFR) sections 191.146.  The 
Occupational Safety and Health Administration (OSHA) requires employees to 
be protected from hazards associated with confined space entry.  The 
confined space hazard in stilling wells is real.  It is easy, however, to 
become complacent about this hazard because of the lack of recent serious 
accidents.  The probability of a serious accident in a stilling well is 
low, however, the results can be fatal.  A fatal accident that occurred in 
August 1960 is described below: 

An employee was "mucking out" a well on the Arkansas River near Little 
Rock.  The stilling well was constructed of cement and 30-40 feet deep.  A 
gasoline-powered pump was tied to the stilling well ladder and was being 
used to lower the water in the well and pump out the mud.   Tubing was 
used to vent the exhaust outside the well.  Exhaust fumes that 
inadvertently leaked into the well overcame the employee in the well and 
caused him to pass out.  A student assisting at the site turned off the 
pump and tried, but was unable to remove the employee from the well.  The 
student began to seriously suffer from the exhaust fumes in the well, so 
he tied off the employee to the stilling well ladder and sought help from 
railroad personnel working nearby.  When help arrived, the water in the 
stilling well had risen and engulfed the employee.  It is unknown if the 
employee died as a result of the exhaust fumes or drowned.  The need to 
address the confined space in stilling wells has been addressed by two 
committees, the WRD Confined Space Subcommittee and the WRD Safety 
Committee.  After considerable review, policy and guidelines have been 
developed on safe entry to existing stilling wells.  The policy and 
guidelines are provided in the attached document and are effective 
immediately.  They apply only to those stilling wells that must be 
physically entered as a requirement of station operation and meet the 
definition of a confined space.  New stilling wells with a confined space 
hazard should not be constructed unless alternative procedures to collect 
the required data are not technically feasible. 
    
Any questions regarding this policy and guidelines should be directed to 
your Regional Safety Officer. 


                                                                /SIGNED/ 

                                             Catherine L. Hill 
                                             Associate Chief Hydrologist 
                                             for Program Operations 

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This Policy Memorandum supersedes previous WRD Memorandums No. 94.30 and 
No. 97.32. 

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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Catherine L. Hill Associate Chief Hydrologist for Program Operations clhill@usgs.gov 441 National Center 703-648-5031 (Phone) U.S. Geological Survey 703-648-5295 (Fax) Reston, Va 20192 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~