Spill Containment for Natural Gas Storage Facility

[Trackfiend]

The proposed site is an underground gas storage facility. Currently the site is being drilled for future operations (storage). The post developed site will have 6" of crushed stone for the majority of the area (300' x 300') and will have an earthen containment berm (2:1 slope, 4' high) surrounding the site. During normal operations and rainfall events, a single outfall culvert with a sluice gate will be utilized to handle all stormwater. In the event of a spill (brine or other), the sluice gate will be closed, effectively containing any spilled substance.

Currently the soils are poor (organic and "fat" clays) and I am awaiting the geotechnical report to confirm. I have several questions in determining what is the best solution to a spill containment:

1. Should I use a liner for the containment berm (GCL)? If so, should it only line the berm or the whole site (kinda like a swimming pool)?

2. Should the entire berm just be constructed of a quality clay (bentonite)?

Any other suggestions or ideas into what could be used for spill containment would be helpful. I'm leaning toward using a geosynthetic clay liner only for the berm, but I also want to see what the geotechnical engineer has to say in his/her report.

 

[bimr]

What are you trying to contain with the spill containment?

 

[TDAA]

Use the fat clays, sans organics. What do you think the bentonite classifies as?

 

[Trackfiend]

bimr,

They are trying to contain any brine spilled on the ground. In the event of a spill, the sluice gate will be closed, and the brine will be cleaned up. Brine is produced when injecting water into a salt dome to create the storage space for the natural gas.

TDAA,

Would a "lean" clay such as one with a lower LL be better suited for berm material or would a higher swell capacity be more desirable for this situation? I'm guessing either will have low hydraulic conductivity.

I'm just unfamiliar with how to properly "seal" off a containment area with an earthen berm and am curious if just the berm needs to be impervious or the berm including some depth beneath it should be impervious.

 

[Trackfiend]

It looks as though maybe a cutoff trench would be a good option also. Some of the documentation I've found online suggests a depth extending either to the next impervious layer in the ground or 3/4 of the height of the berm.

The function of the berm in this application is not flood protection, only for proper stormwater discharge. I'm not sure if what I'm finding is overkill for this situation being that most of the documents I've found so far is for levee or dam construction.

 

[bimr]

If you have secondary containment on any solution mining tanks and secondary containment on the piping, you will not need secondary containment for the entire site.

http://www.subterraes.com/pdf/Underground_Gas_Storage_Definitions.pdf

 

[konman]

If the site is being drilled already, you are already too late to contain spills from the highest risk operation. Drilling mud used for salt caverns are either brine or invert based. As cavern development moves into the mining stage, the risk of a spill is reduced significantly. There is little to no risk of a brine spill once the brine has been displaced by natural gas.

 

[EngineerofSteel]

I work in the Ag Industry. One company I work for does a lot of EPA remediation work. The issue of clay v. liner is a very hot issue here in California.

Experience shows that the liners puncture easily. This results in costly repairs.

The clay liners, however, function extremely well- when constructed correctly.

Every industry expert, as far as I know, wants clay liners. Only the EPA pushes the plastic liners.

If allowed in your state, use clay.

 

[Trackfiend]

Thanks DairyDesigner.

The geotech is running the permeability tests right now so once I get those results (coupled with environmental boys allowance for detainment time within the berm should a spill happen) it will help in determining if a clay liner or clay cutoff trench is the best solution.

Thanks again for all the replies.

 

[hmcrae]

I have not designed such facilities, but have worked with GCL on petroleum projects as a contractor. The American Petroleum Institute seemed to be the governing body on designs for much of that project. Have you checked their codes?

 

[cvg]

cutoff trench will only prevent underseepage below the berm. Since your site consists of fat clays, I'm not sure a cutoff trench is necessary. The cutoff trench does not prevent percolation like a liner would. However, again since your site consists of fat clays, it does not sound necessary for a liner either. Underseepage for a 4 foot high berm, built on fat clay soils sounds highly unlikely. Rather than researching this online, why aren't you having this conversation with your geotech?

 

[Trackfiend]

cvg,

I've yet to discuss this with the geotech but will shortly to see what his recommendation is.

 

[Trackfiend]

I've just received the geotechnical report and the geotech has given several options:

1. Constructing the berm out of suitable clay material (PI < 40).
2. Lime treatment of existing clay material to lower PI.
3. Synthetic liner.
4. Sheetpile installed through the berm section.

Per my discussion with the client, it seems that we will go the rout of utilizing suitable clay material for both the berm construction and the site itself.

Thanks for all the replies.