Wet-well pump motors in hazardous locations

November 5, 1979
Mr. J. D. Spooner
Vice President and General Sales Manager
Weil Pump Company
[Recipient address omitted]
Dear Mr. Spooner:
This is in response to your recent telegram addressed to Mr. William Simms concerning OSHA's policy on classification of a wet well as a Class 1, Division 1 location.
The General Industry Standard [29 CFR 1910.399(a)], NEC Sections 500 and 501, applies to situations for OSHA-covered employers. Hazardous concentrations of flammable gases, such as methane and hydrogen sulfide, may exist continuously, intermittently, or periodically under normal operating conditions in a waste-water (containing organic matter) collection system. If at least one OSHA-covered employee is exposed to the hazard, then the wet well pump motor must be of a type indicated in the National Electrical Code Section 501-8(a) for a Class 1, Division 1 location. The employee need not be in the wet well to be exposed to the effects of an explosion.
We hope this information will be helpful to you. If we may be of any further assistance, please feel free to call or write.
Sincerely,
Grover C. Wrenn, Director
[Directorate of Enforcement Programs]
[Corrected 6/2/2005]