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(a) Many tanks have been outfitted with PVC drain pipes from each sample tap running into a barrel.
- Initial Cost: $300.00 - $500.00
These barrels must be sucked out occasionally. In the winter a steam truck is required to assist vac.
- Summertime (vac only & already on lease): $25.00
- Wintertime (Steamer and vac traveling together): .5 to 1.0 hr each;
Total times and cost estimate for both trucks combined to do the job
NOTE:
Operators advise that these barrels are sucked out on average 3 times per winter, and 3 times per summer. With the Enviro Vault, there is no additional cost, winter or summer, as the truck cleans out the vault when accessing tank by simply closing the 4" and opening the 2" vault suck out valve.
(b) The overflow/equalization tube is an option that can
save costs in a couple of ways.
The overflow aspect is quite simple. If the fluid in the tank rises too high, it simply flows down the tube into the vault. A spill under approximately 3 barrels could be fully contained in the vault. If the spill over was of a larger volume, it will simply run out the cracks of the door. This would limit the mess on the tank to the bottom 3 feet and prevent a major tank cleanup caused by a spill out of the thief hatch. Cost Savings: Steamer and man basket to clean tank spill from thief hatch $500.00 - $1500.00, much more in a group tank setting.
The equalization aspect is theoretical only and has not been proven. The theory is that if the thief hatch and top vent were to freeze off and a load of fluid was removed from the tank, air would travel up the tube equalizing the negative pressure prior to any tank damage occurring (i.e.: caved in roof). I have been in touch with the Alberta Research Council and they advise that while they can prove the theory one way or the other, the cost to do so will be very high.
Operators advise that even in a dyked area, the mess on the ground under the valves must still be cleaned regularly and the waste disposed of at an approved disposal facility. Crew time and disposal costs could easily exceed $75.00 to $100.00/lease/year. There is NO such cost with the Enviro Vault. In fact, operators advise that they use the Enviro Vault to dispose of wellhead sample fluid as well as mess from ground around wellhead. Sample fluid from leases without Enviro Vaults are also brought to tanks with Enviro Vaults for disposal.
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