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Re: Below-Ground Vault or Wet-Well for Fire Water Storage

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I've always found it interesting that "highway loading" is do often 
specified for structures like this.

If you've done any bridge design, you realize that the highway truck 
loading is highly generalized and takes into account a whole slew of things 
 that an occasionally-loaded structure never will see, meant to represent a 
 high incidence of overloaded large trucks traveling at highway speeds.

It's convenient to use because everyone thinks "oh, yeah, trucks," but the 
HS and HL (used since mid-90s) type loadings are NOTIONAL LOADS and mostly 
overkill for small-area and small-instance-of-load situations.

It would be great if someone came up  with a loading alternative for "stuff 
 on the ground that things roll over" but I'm not holding my breath.

William L. Polhemus, Jr. P.E.


> On Feb 24, 2014, at 5:57 PM, "Lloyd" <lloyd(--nospam--at)> 
> wrote: 
> I've done these types of systems and have used both concrete and
> poly vaults.  The only thing that we had to do, beyond a typical septic
> tank vault, was where the vault might be driven over.  With the
> possibility for a truck load on the top of the vault, we had to design
> the top and lid of the vault to an HS-20 load standard.
> I would also consider the vault's potential for floating up out of the
> ground when it gets sucked empty and the soils around it
> have a high ground water condition.
> HTH,
> Lloyd
>> On 24 Feb 2014 at 21:52, Polhemus, William wrote:
>> This is kinda civil-y, but I thought someone here might have some idea
>> if there are any governing requirements I need to be aware of.

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