Is Containment Area a Confined Space

[structure_engineer]

Hello All Civil Engineers,

I have to design a containment area large enough to contain the rupture of 3 12-foot diameter and 20 feet tall tanks. The volume of the containment is for the content of all three tanks content (not a typo), plus the freeboard corresponding to a 25 year, 24 hour rain event. The way the drains are designed is to drain the content of all three tanks. The rain fall for a 25-year recurrence interval for a 24-hour duration is 10.5 inches, rounded up to 11 inches. Total volume for 3 tanks is 6786 ft3. The total containment volume is 9533 ft3. The area required is 2450 ft2 (with some allowance for the octagon pedestals for the tanks plus some supports) because we have to stay under 4' so I used 3'-11", due to the confined space height. My question is: how is this a confined space? The size is 62' x 41', with 2 stiles to get in and out of the containment area. To me, the limitation of not to exceed 4' is when we are digging a trench and that qualifies as a confined space. What is your opinion on this topic? Do I need to follow the "confined space" and limit my wall height to not to exceed 4'? Or that rule does not apply here as you have a wide-open enough space and there are 2 means of egress to get into and out of the containment area easily.

 

[dik]

In general, a confined space is defined as an area that has limited or restricted means for entry or exit and is not designed for continuous occupancy. When I was doing some work on the floodway gates it was considered 'confined' since there is only one access and it is not intended for occupancy.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[SwinnyGG]

Limited means of access/egress: check

Not intended for occupancy: check

Osha also specifically lists the following as a condition which designates a location as a permit required confined space:

Permit-required confined space (permit space) means a confined space that has one or more of the following characteristics:

(1) Contains or has a potential to contain a hazardous atmosphere;

(2) Contains a material that has the potential for engulfing an entrant;

(3) Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section; or

(4) Contains any other recognized serious safety or health hazard.

It sounds to me like an employee could be engulfed by the contents of a tank, should a tank burst while an employee is in the area... so it's not only a confined space, its a permit required confined space.

 

[dik]

Thanks, Swinny... didn't know of the other issues.

Ran into some issues with the confined space I noted... I had a testing agency get some coupons of the gate reinforcing. The entrance 'desk' was vacant... the guy had gone for coffee... so we signed in and went down (we had proper equipment, including gases, etc.) I shouldn't have done that... one of the few times I've been PPWhacked in my career; I can still feel the pain and that was a decade back.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[structure_engineer]

Thanks for the comments dik and SwinnyGG. I will leave it like it is and use a wall height of 3'-11" for now. Unless I have confirmation from OSHA, it will remain as 3'-11". Better to be on the safe side.

 

[bimr]

The safety person at the site determines what is a confined space.

In order for a work area to be defined as a confined space it must meet all three of the following criteria:

1) Limited Openings for Entry and Exit. A confined space may be difficult to enter and perform repair work, or general maintenance. If something goes wrong while you are inside a confined space, escape/rescue may be difficult. Just because a work area has more than one way of escape, does not necessarily mean it is not a confined space. If the space has limited ways to get in and out, it could be a confined space. An open top tank would have limited openings for entry and exit.

2) The Space is not Intended for Continuous Human Occupancy. This means that the space was designed to hold something other than people. Examples include tanks and manholes.

3) The Space is Large Enough for You to Enter and Conduct Work. If you cannot fit your body into the space you cannot become trapped inside.

In order for something to be defined as a confined space, it must meet all three of the about definitions. According to the Occupational Safety and Health Administration (OSHA) if a space does not meet all three of the above definitions, it is not considered a confined space.

 

[dik]

Thanks for the added item... There may not be a safety person on site... In the case of the floodway gate, the space was likely over 1000 sq.ft.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[FacEngrPE]

The safety person at the site determines what is a confined space.

could also be "The safety person responsible for the site."
If the site has any permit required confined space, then it needs to have a compliant confined space access permit procedure.
The 4 foot rule for trench excavation may not always apply to other situations (like entering a bund, or an open top tank/vat). The site safety documentation may provide some enlightenment, or perhaps the site needs to perform a HAZOP/PHA (you can do this even for situations where it is not a legal requirement).