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  1. #1
    Join Date
    Nov. 29, 2008
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    Default Underground Heating Oil Tank/ New Pasture

    We have an existing 1930's 1000 gallon underground heating oil tank that we want to have removed. We've spent the last year putting in new pastures and fence, and we are going to bring one of the fence lines up past our house. The tank where it is now would end up in the new pasture.

    Removing the tank has been on our to-do list for a long time anyway, but it's always been a scary prospect for us due to the possibility of it leaking, and the cost of cleaning it up if it does leak.

    There's been no outward signs that it does leak, and during the summer when the only thing using oil is the water heater, the tank oil level measurements confirm oil usage that fits exactly with the firing rate of the water heater. There's never been any water in the tank either.

    Here's the question:

    Just for our own peace of mind before we hire the contractor to remove the tank. We dug two test holes six feet away from the outside of the 48 inch diameter underground tank using the post hole digger on the tractor and went down 48 inches into the ground.

    We took a hand operated post hole digger and pulled up some samples from the bottoms of the holes, and put our noses to it. There is no oil smell whatsoever in the dirt.

    So our question is, when oil does leak from an underground tank how does it typically disperse into the soil?

    Does it have any tendency to be driven up to the surface when it rains because oil is lighter then water?

    If the soil around the tank perks well, does the oil have any tendency to just absorb into the soil around the tank and just remain there?

    Or are there cases when the oil leaks out of a tank and goes straight down into the ground beneath the tank, and just goes deeper and deeper into the ground below, with no migration to the soil surrounding the tank at all?

    We don't want to get ripped off by a contractor, as we have heard of some horror stories of contractors who create a spill, or fake the soil test results, so that they can profit from the clean up.

    Any advice from anyone who has had experience having an oil tank removed would be very helpful. Also advice about how to keep the contractor honest would be helpful too.

    Should we first hire some sort of independent contractor who can take deep soil core samples around the tank to have a record of the soil conditions before the removal contractor begins work?

    Thanks.



  2. #2
    Join Date
    Oct. 28, 2007
    Location
    NY
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    4,895

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    In principal I'd get an independent contractor from outside of your area (so no collusion) , and if it possible get it certified clean. Then with the certification, hire removers with a contract stipulation that if anything leaks the removers have to clean it up at their expense. Of course that may not be possible.
    A casual search found this site http://www.oiltanksolutions.com/soil...sampling.shtml
    I'd research on the net before calling anyone, so you know your state laws and can't be bamboozled. It's always better to be knowledgable going into something like this.



  3. #3
    Join Date
    Jan. 27, 2004
    Location
    Yonder, USA
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    2,561

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    Technically, fuel oil should migrate down to the top of your water table, then move laterally with the ground water. Because of capillary action through the soil, the path will be kinda smeary rather than straight down/straight over. Heavy clay soil will slow movement to a snail's pace.

    It should only come to the surface if your water table is shallow enough to come to the surface following a heavy rain. There is *some* sticking to organic particles in the soil--just as the lighter molecules will evaporate into the air in the soil voids--but generally not enough to matter.

    So, digging around the tank will likely yield nothing unless you're smack up against the tank (at which point you might as well pull it out and look under it). If you really want to look for an underground tank leak, go downhill of the tank a meter or two and have a couple monitoring wells installed through the vadose zone into the saturated zone (in other words, deeper than you went). Even if your water table is too deep to reach, you should be able to use direct-push to collect soil samples below-and-slightly-downhill of the tank.

    Of course, by that point, you might as well just pull the tank out...

    ETA: If you want to educate yourself a bit more, research "LNAPL" (light, non aqueous phase liquid) movement in unsaturated soils. Also, "LUST" (leaking underground storage tank), particularly as applied to old gas stations. Fuel oil is pretty much diesel fuel.
    ---------------------------



  4. #4
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    Jan. 26, 2006
    Location
    Fort Worth, Texas
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    5,354

    Default

    Are you confident of the tank size being 1,000 gallons? If greater than 1,100 gallons it will fall under different regulations.



  5. #5
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    Nov. 29, 2008
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    Quote Originally Posted by Chall View Post
    In principal I'd get an independent contractor from outside of your area (so no collusion) , and if it possible get it certified clean. Then with the certification, hire removers with a contract stipulation that if anything leaks the removers have to clean it up at their expense. Of course that may not be possible.
    A casual search found this site http://www.oiltanksolutions.com/soil...sampling.shtml
    I'd research on the net before calling anyone, so you know your state laws and can't be bamboozled. It's always better to be knowledgable going into something like this.
    I like the outside of area contractor idea, the link is helpful too, thank you for your ideas.



  6. #6
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    Nov. 29, 2008
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    Quote Originally Posted by WildBlue View Post
    Technically, fuel oil should migrate down to the top of your water table, then move laterally with the ground water. Because of capillary action through the soil, the path will be kinda smeary rather than straight down/straight over. Heavy clay soil will slow movement to a snail's pace.

    It should only come to the surface if your water table is shallow enough to come to the surface following a heavy rain. There is *some* sticking to organic particles in the soil--just as the lighter molecules will evaporate into the air in the soil voids--but generally not enough to matter.

    So, digging around the tank will likely yield nothing unless you're smack up against the tank (at which point you might as well pull it out and look under it). If you really want to look for an underground tank leak, go downhill of the tank a meter or two and have a couple monitoring wells installed through the vadose zone into the saturated zone (in other words, deeper than you went). Even if your water table is too deep to reach, you should be able to use direct-push to collect soil samples below-and-slightly-downhill of the tank.

    Of course, by that point, you might as well just pull the tank out...

    ETA: If you want to educate yourself a bit more, research "LNAPL" (light, non aqueous phase liquid) movement in unsaturated soils. Also, "LUST" (leaking underground storage tank), particularly as applied to old gas stations. Fuel oil is pretty much diesel fuel.
    This is exactly what we were looking for. We did some searching on the net and found illustrations that showed how oil flows down through the soil and forms what they called a "plume", that flows out horizontally with the direction of the ground water.

    One of our test holes was downhill from the tank, and in the bottom of the hole there was wet clay soil that looked and smelled perfectly fine. I realize now that those tests could miss a leak, but it's still reassuring that there was no obvious oil that we could detect.

    We're going to put a lot of thought into this before proceeding. We have our own backhoe, and could do a very deep test hole down hill from the tank at a safe distance so as not to disturb it. Maybe take some samples from that level and try to find an independent testing lab to get a preliminary result.

    We certainly want to make sure we do this with all the proper permits and in accordance with all relevant regulations, so we need to research that as well.

    It really is a very big worry for us having contractors in to do work, as we have a nice farm, and that makes a lot of contractors think big dollars, so we feel we need to become experts on what needs to be done and micromanage the work to keep any games from being played on us.

    Thank you for your good advice!



  7. #7
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    Quote Originally Posted by clanter View Post
    Are you confident of the tank size being 1,000 gallons? If greater than 1,100 gallons it will fall under different regulations.
    That's a good question because we did read about regulated vs. unregulated underground storage tanks.

    We've had the tank filled so many times that it's true size is not a question.

    Additionally, we use a standard 1000 gal oil tank chart and use it for figuring the oil level and how much oil we use. When we have a delivery we always take before filling, and after filling, measurements and record those in a record. The oil level measurements are always exactly in accordance with the amount delivered. We try to never let the level go below 10 inches, and have never had a delivery of more then 800 gallons or so.

    So yes, it is a 1000 gal tank.



  8. #8
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    Jun. 20, 2000
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    Full time in Delhi, NY!
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    Sorry to be stupid. Can't you just empty it and leave it in place. Fill it with sand maybe?
    ~Kryswyn~ Always look on the bright side of life, de doo, de doo de doo de doo
    Check out my Kryswyn JRTs on Facebook

    "Life is merrier with a terrier!"



  9. #9
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    Nov. 29, 2008
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    Quote Originally Posted by Kryswyn View Post
    Sorry to be stupid. Can't you just empty it and leave it in place. Fill it with sand maybe?
    That's not a stupid question...

    From what we understand abandoning a tank in place is an option. But everything we've read so far says that complete tank removal by an EPA licensed contractor is best for maintaining property value. Having that paper trail showing that everything was done properly with all the proper permits is important if you ever decide you want to sell your farm.



  10. #10
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    Jan. 27, 2004
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    Yonder, USA
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    Is the whole area surrounding and under the tank clay, or is the clay present in layers with other types of soil mixed in?

    If everything is good clay below the topsoil, you should be in great shape since any leak would be contained by the clay. But if you're digging down and find layers, like: topsoil, clay, sandy stuff, more clay, then pay really close attention to the layers of not-clay.

    Since you're concerned about paper trail and future property sales, do make sure you budget for someone to *correctly* collect some soil samples from the bottom of the hole immediately after the tank is lifted out and have them tested at an EPA-certified enviro lab. IIRC, methodology is something like a couple places that were immediately under the removed tank, then digging in a couple more spots at 6-12"? A person who does that would know. Do micromanage by making sure it looks like they're using very clean (decontaminated) tools, sealed sampling containers, etc. It shouldn't be some guy with no gloves, a dirty spoon, and a plastic baggie if you want good documentation.



  11. #11
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    Nov. 29, 2008
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    Quote Originally Posted by WildBlue View Post
    Is the whole area surrounding and under the tank clay, or is the clay present in layers with other types of soil mixed in?

    If everything is good clay below the topsoil, you should be in great shape since any leak would be contained by the clay. But if you're digging down and find layers, like: topsoil, clay, sandy stuff, more clay, then pay really close attention to the layers of not-clay.

    Since you're concerned about paper trail and future property sales, do make sure you budget for someone to *correctly* collect some soil samples from the bottom of the hole immediately after the tank is lifted out and have them tested at an EPA-certified enviro lab. IIRC, methodology is something like a couple places that were immediately under the removed tank, then digging in a couple more spots at 6-12"? A person who does that would know. Do micromanage by making sure it looks like they're using very clean (decontaminated) tools, sealed sampling containers, etc. It shouldn't be some guy with no gloves, a dirty spoon, and a plastic baggie if you want good documentation.
    That's one thing that's been very consistent as we have been installing new fencing, is a layer of dense clay at the bottom of practically every post hole we've dug. So I'd say the likelihood is very good that the whole area under the tank is dense clay.

    That's why we felt pretty good when we dug the test holes around the tank, as the first 3 feet was more of a rocky top soil, and at the bottom we hit the clay layer.

    Because we dug the test hole down hill from the tank, we figured if significant quantities of oil were leaking, it would have "absorbed" into the more permeable top soil layer above the clay, and migrated down hill from the tank through that top layer of soil.

    That's what brought me here to ask the questions about how oil disperses in soil from a leaking tank.

    Thanks again WildBlue!

    All your advice contains just the sorts of details we were hoping to have, and they are really very helpful for us!



  12. #12
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    Jun. 24, 2005
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    Alabama
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    Kryswyn-one problem about leaving it empty, is empty tanks rise to the surface. That's why a gas station that goes out of business has to have the tanks removed ASAP. And I doubt anywhere has environmental regs that allow an abandoned tank to stay in place, even if filled in. Any tank could eventually leak, and that could be very pricey to get rid of, and clean up.
    You can't fix stupid-Ron White



  13. #13
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    Sep. 5, 2005
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    Mass.
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    How do you know it is not leaking? That's something you have no way of telling unless you get it out and look underneath, yes?

    I would spend the money and have it professionally removed. For one thing, if you ever sell, you'll have to. Once it's out, you may still need to have the site cleaned up. Even if you spend a couple thousand dollars, at least it will be gone and you won't have to worry about it anymore. Also, if the whole thing rusts out, then you're going to have a sink hole, which is its own problem.
    I realize that I'm generalizing here, but as is often the case when I generalize, I don't care. ~ Dave Barry



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