secondary containment wall height 3

[kahlilj]

Does anyone know if there is a minimum height requirement for a concrete wall secondary containment for AGHST's?

I have read that the containment volume should be adequate to contain the volume of the largest tank plus have sufficient freeboard for a 100 year storm event (for a 24 hr period?) & that is typically 110% of the largest tank; but is there any minimum (or maximum) requirement for the wall height (i.e., the sides) of the spill containment area?

 

[Ashereng]

That sounds about right.

I don't have any experience with designing secondary containment, however, I have heard things such as what you propose.

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[kahlilj]

so as far you know there is no wall height requirement?

 

[Ashereng]

There is no specified height requirement.

For us, it is 100% of the larget tank plus the greater of:
- 10% of the largest tank, or
- 10% of the agregate of all tanks (excluding the largest one)

There is no provision for rain.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
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[JJPellin]

I work in an oil refinery. We require containment equal to the largest tank in the containment plus a 25 year 24 hour rainfall (9 inches, worst case for our Corpus Christi refinery). Wall hight requirements have a maximum that is based on the soil loading considerations and is unrelated to tank size.

 

[Ashereng]

JJ,

Yes, the wall height has to be engineered to sufficiently do the job (loading, foundation, etc.). If the wall is too high, there is also the possibility of confined space entry requirements, etc.

I interpreted the OP as pertaining to something akin to "... or a minimum of 3 feet" or something.

We are currently putting in 2 different tanks. One by it self, and the other into an exisitng containment area. We do not have requirements for rain.

Seems like each site uses different estimates.

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[zdas04]

The current SPCC (40 CFR 112) is still being litigated pretty agressively, and the requirement for implementation has just slipped again (this time to October 31, 2007). Everyone thinks that it will be modified again prior to implementation, but that is not certain and many companies have given up the fight and are implementing the pending legislation. What it says is you have to have "sufficient capacity to hold the contents of the largest tank plus sufficient freeboard for precipitation".

EPA Region 9 has published one of their usual guidance documents that says hard and fast that the requirement is 110% of the cross-connected volume or the largest tank that is not cross connected. That is the only place I've ever seen the requirement for the cross-connected volume. If three 1,000 bbl tanks have a line to a common pump-suction header then Region 9 would require 3,300 bbl minimum containment volume.

As has been said above, the height of the containment is not mentioned in the SPCC, but the suggestions to use good engineering practices is the way to go since the SPCC plan has to be stamped by a PE.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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[kahlilj]

thanks folks! this confirms things for me.

we have two lube oil tanks with existing concrete containment which needs repairing. we will likely keep the wall at its current height.

david & ashereng, i am not sure if these two tanks are cross-connected or not. i presume they are, but will verify it later. i was not aware of any alternate to the 110% capacity of largest tank. does "aggregate of all tanks (excluding the largest one)" mean the total volume of all tanks except the largest one? which region does this apply to? i'm in georgia (i think region 4). or is this a national requirement?

jj, i seem to recall having read/heard something about a 3 foot minimum some time ago as well. i thought maybe i read it in NFPA 30, but after reviewing that spec the other day i could not find that in relation to a concrete containment wall. it does make reference to that for berms (i think earthen berms/dikes).

 

[Ashereng]

kahlilj,

My site is in Alberta Canada.

We have 3 tanks, 100,000 bbl, 60,000 bbl and 60,000 bbl,

Our secondary containment is sized for 112,000 bbl.

1) largest tank is 100,000 bbl
2) 10% of 100,000 is 10,00 bbl, 10% of aggregate is 12,000 bbl so we use 12,000 bbl



"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[zdas04]

The SPCC is a US national code. Each EPA region is charged with enforcing it. The folks at EPA are just folks and they each will put their own spin on how they understand the code.

The only time I've seen the largest tank excluded is in the language for calculating the berm capacity after you've determined the volume requirement. Assuming you have several tanks sitting on the ground within your secondary containment that are not cross connected, then the reasoning is that if the largest tank splits wide open you don't have to exclude the volume it occupies from your available berm size, but you do have to exclude the volume of the other tanks up to the berm height because they will not have been be breached.

David

 

[kahlilj]

the tanks can be cross-connected. there are 2 tanks (6,000 gal & 3,000 gal). the can be connected by opening a valve at the pump that services both of them. however, this valve is normally closed. it is a rare & emergency only occassion in which the valve would be opened.

that being said, we will have sufficient capacity using either the largest tank OR both based on the existing wall height. i just determined the capacity for the planned containment area (~1782 c.f.) at that wall height will be way more than the required volume (~1324 c.f.).

so it looks like we'll be covered either way.

thanks all for your guidance.

kahlil