June 1, 1995

Ms. Janice Gelhaus, CIH
Safety and Occupational Health Office
Department of the Army
South Atlantic Division
Corps of Engineers
Room 313
77 Forsyth Street, S.W.
Atlanta, Georgia 30335-6801

Dear Ms. Gelhaus:

Thank you for your April 27 letter regarding your Permit-required Confined Space (PRCS) interpretation request concerning a hydropower dam's 22 foot diameter sluice tunnel. Your letter was referred to the Office of Federal Agency Programs for response.

In 29 CFR 1910.146(c)(1), the Confined Space Standard, OSHA placed the responsibility on the employer to evaluate and determine if any "spaces" would come under the confined space standard. The standard's performance language makes it inappropriate for OSHA to give employers specific entry or exit dimensional information.

To answer your questions we offer the following:

Question 1a. Does OSHA equate distance with limited access/egress?

Answer: Yes.

Question 1b. If so, how far must an employee travel to an exit to qualify a space as having limited access/egress?

Answer: The amount of travel time to the point of safety should be considered; not the travel distance.

Question 2. If you conclude that the space is in fact a confined space, would it be classified as a Permit-required confined space (PRCS)?

Answer: There is insufficient information in your request to assist the Army in making this initial employer determination. The following statements may assist you in your determination.

A. If none of the hazard characteristics which trigger the standard are present then the space would not be a PRCS.

B. If the exhaust gases of the vehicle used to drive to the inspection site present an acute hazard (not chronic), then the space and hazard present would meet the definition of a PRCS.

C. The potential engulfment by water held back by the double sluice gates should not be an issue. The standard accepts a double block and bleed situation as a form of isolation.

Question 3. Is there an interpretation that would assist us in demonstrating that the natural ventilation provided by the 400' air shaft is adequate for operating a gasoline powered vehicle within the tunnel?

Answer: No. The Corps should make this and other determinations on a case by case basis as they are all unique. Applying the ventilation principles associated with tunnel construction is inappropriate.

Question 4. Would OSHA require that entrants demonstrate that the ventilation met the established criteria prior to each entry?

Answer: With regard to the PRCS, pre entry atmospheric testing is only required for permit spaces. Thus, if the Corps determines the tunnel is a permit space then all appropriate standard requirements would apply. If a permit space exists, whether it is the tunnel in question or any other space, OSHA would require the employer, not the employee, to demonstrate that the atmosphere is acceptable for entry under the Corps' program.

We have enclosed OSHA Instruction CPL 2.100, Application of the Permit-Required Confined Spaces (PRCS) Standard, 29 CFR 1910.146, dated May 5, 1995, to assist you with your evaluation. Appendix E contains Questions and Answers that may give you additional guidance.

If you have additional questions or concerns, please contact Barbara H. Burr at 202-219-9329, extension 160.

Sincerely,



John E. Plummer, Director
Office of Federal Agency Programs

Enclosure



April 27, 1995

Safety and Occupational Health Office

SUBJECT: 29 CFR 1910.146 Interpretation

Don Kallstrom
Director of Compliance Assistance
U.S. Dept. of Labor - OSHA
200 Constitution Ave., N.W.
Washington, D.C. 20210

Dear Don,

We need your assistance in answering question that have been raised during surveys to identify confined spaces at our facilities. I am referencing a specific space to illustrate the issues. We cannot decide whether it meets the OSHA criteria for limited access/egress. The following is a brief description of the space and I have also enclosed a diagram to help you visualize it.

DESCRIPTION: (see attached diagram) The emergency low-level sluice at a hydropower dam. Its purpose is to release water from the lake into the lower pool during appropriate conditions. It consists of a 2532' long tunnel connecting the lake to a downstream channel. It contains 2,in-line gates which control the water flow through the sluice. The gates are in a chamber slightly upstream of the midpoint of the sluice. There is a 10' diameter, 400' air shaft above the gate chamber, which extends to an adit building on the surface. The air shaft is divided into 2 sections one of which contains an elevator for transport of equipment, but not personnel. The 1452' portion of the sluice downstream of the gate chamber is a 22' diameter unlined horseshoe tunnel, the floor of which is a road bed. The portion of the sluice upstream of the gate chamber is always filled with water and is not entered. The downstream portion is normally dry and employees periodically enter that section to inspect the tunnel and the gates (they usually drive trucks into the tunnel to perform the inspection).

Some members of our organization believe that the distance that must be traveled to reach an exit qualifies the space as having limited access/egress. Others believe that the dimensions of the tunnel preclude it having limited access.

Please assist us by answering the following specific questions raised during our evaluation of the space:

1. Does OSHA equate distance with limited access/egress? If so, how far must an employee travel to an exit to qualify a space as having limited access/egress?

2. If you conclude that the space is in fact a confined space, would it be classified as a permit required confined space?

3. Is there an interpretation that would assist us in demonstrating that the natural ventilation provided by the 400' air shaft is adequate for operating a gasoline powered vehicle within the tunnel? For example would it be appropriate to compare the volumne and velocity of air movement in the tunnel to that referenced in 29 CFR 1926.800(k)(2) and (3), even though it is supplied through natural rather than mechanical means.

4. Would OSHA require that entrants demonstrate that the ventilation met the established criteria prior to each entry?

To help in your determination, I offer the following additional information: The purpose of entering the tunnel is to examine it for structural integrity and to evaluate the operation of the gates which can be used to release water from the lake. Normally water passes through an adjacent powerhouse and would only be released through the sluice during an emergency adjustment to the lake's water level (i.e. during flooding). The 2 in-line gates allow the entrants to inspect the operation of each without the release of water from the sluice. There is an established procedure to ensure that water is not released to protect the tunnel's road bed as well as the entrants.

If you need more information, please contact me or Ms Mary Hay at (404) 730-3327. Thank you for your time and effort.

Sincerely,



JANICE GELHAUS, CIH

(For Figure 1, see printed copy.)