Underground water tank

Plastics and GRP-reinforced tanks are also suitable materials.

Another possibility to consider is coating the inside of the existing tank with a bitumen-like material, though it does depend on "how far gone" the tank is.

Thanks for the comment. With regards to repair, what I failed to mention is that while it is generally level around the tank, the ground is now falling away on one side. I interpret this to indicate the tank leakage is washing the earth away underground beneath the tank. I expect to find something like a sink hole under the tank.

At this time we keep a 3/4 inch hose feeding water into the tank when it is in use in order to keep it filled to working level.

I have failed to find government or commercial/professional specifications governing tank installations (except for thirty or so mil specs that are cancelled or "inactive" and are not really useful in any case.) Having an engineering specification (from a civil engineering professional organization, or such) which addresses application and installation would be most helpful in establishing a workable contract for the effort.

I currently working for a company the installs fuel tanks for airports in the U.S. I perfer not to install tanks in the ground because they are hard to maintain and for hazardous chemical they need to be two ply walls. The enviromental engineers hate the idea to install tanks in the ground. The only reason people put tanks in the ground are for lack of room on the land, or to keep the tanks from being an eye sore. (such as gas stations) They do make fiberglass tanks, they are pretty expensive. My suggestion is to stop using that tank immediately, because the ground support is being washed away from the tank. The ground is becoming very unstable the more you use the tank and if a sink hole is developing someone can get hurt or die.

My suggestion is to remove the tank below ground and fill the hole with dirt. Install a new metal water tank above ground and have a qualified tank installation company to inspect the tank once a year for leaks and put a new coat of paint on the tank. That way the tank will last for many years. If you are using the tank for hazardous chemical you will need to put a concrete chemical containment.

If you are in city limits you will need to have a qualified contractor to pull your permits and properly remove the water tank.

I failed to mention is that while it is generally level around the tank, the ground is now falling away on one side. I interpret this to indicate the tank leakage is washing the earth away underground beneath the tank. washing the earth away underground beneath the tank.

Can you be sure that the side or part of the top of the tank has not caved in? There is also the possibility of the lid caving in and someone falling into the hole.

I would put a barracade around it immediately, and do something to replace it urgently

I agree with this 110%. I don't know anything about your water, but the FRP tank is probably a good way to go. But you have to keep people away from the area before somebody is sucked into the sink hole.

Thanks. I agree. It is "taped off" with safety tape to warn of potential danger. The situation is being approached with some urgency.

When you say process water, is it water only, with no contaminants?

What temperature is the water? Why do you need storage?

If possible, I would put it indoors and would purchase a plastic tank. They cost less than $5000, they don't weigh a lot, and are simple to install.

As far as the old tank is concerned, if all that was in it was water, fill it with sand, without digging it up. Digging it up, removing the tank, and filling the hole will cost you $5000, assumming there are no buried utilities.

Filling with sand should be $1000. There are cement companies that have a special slurry mix that is mostly sand with a little concrete mixed in. This product will compact without tamping, and will not settle. It also can be hand dug after it sets, in case it is needed.

hi,

it is very dangerous to answer your question without a professional assessment of the structural integrity of the tank itself.Assuming it' s a carbon steel tank and taking in consideration the depth the tank is buried ( weight of the covering dirt over the tank v/s resistance of the wall of the empty tank ), the depth of the overall rust of the carbon steel sheets should be measured .Rust pin holes can easily go deeper than 1/16 of an inch. Filling it with a liquid sludge would be a very costly option should the tank to be removed in the future, in reference to planning foundations resistance for a construction over this area. Temporarily for 2 to 5 years you can stop leaks with hot liquid asphalt coating layers all around the inside of the tank( same as the gasoline tanks before being buried). But the best lost is the first one. I suggest you don't trow good money after bad. So I would accept that it is no longer viable and safe to repair it and replace it by one or two rotational molded plastic tanks. Just by removing it, the installation cost of a plastic tank would be mostly covered!And these tanks are not expensive! The same equipments that would be required to remove it would be used to install the new tank, and the same truck that would bring the new tank would take away the old one.Just plan well the sequence of use of the rented equipments. That's where you can save.

issa

Its not sludge. It is approximately 90% sand, and 10% cement. It will set up as a very good solid base, that won't cave in. It has very little shrinkage, and will form around any configuration. Before filling, I would put a few holes in the bottom so that if there is undermining, it will fill the void. That's why it is used for fill as a roadway base. If water or sewer lines are close and may have to be dug up in the future, it is perfect.

If this tank is similar to a water storage tank (cistern) it can be replaced with a concrete septic tank. The septic tanks can have openings placed wherever you want them and whatever size you want. They are many times delivered by a truck that can place the tank wherever you want it saving the cost of a crane or other heavy equipment. It does sound like a replacement is in order.

It rusted away... Cathodic protection could have lengthened the life of the tank. Fiberglass will probably be your most economocal choice for replacement.

In response to your question about what questions to ask, you may find this website useful.

http://www.epa.gov/OUST/ or

http://www.tceq.state.tx.us/compliance/compliance_support/licensing/ust_lic.html

I'd get the tank out of the ground asap and replace it with an aboveground tank, 4500 gal is not very big. Is there a reason that it has to be underground?

You'll have to replace the tank. Repairs on a corroded leaking tank are seldom cost efficient.

I suggest looking here http://www.watertanks.com/agindustrialtanks/.

Underground tanks raise lots of regulatory eyebrows. I suggest finding your local code enforcement website and/or contacting their office to determine those issues for both removal and replacement.

I woudl be surprised if repair is a cost effective option.

Rotation molded polyethylene tanks, either single or dual containment depending on your needs, are probably your low cost option aboveground. Belowground, my guess is the regulatory requirements exceed the technical req'mts so no comment based on the information available.

Some additional information:

The tank contains fresh (non-potable) water, no deliberate contaminants, used for cooling machinery. It is an expansion volume to hold water when the system is secured and to provide extra water for transients and such. Inlet is gravity fed from a set of cooling towers (located above the tank) and outlet provides positive inlet pressure to a (centrifugal) cooling water pump.

I have confirmed with the state evnironmental regulatory agentcy that there areno regulatory issues with such a water tank, underground or otherwise, from their perspective.

While I have no documentation on the matter it seems the location (below ground) was chosen to provide easy orientation to the cooling towers and pump, and to protect the tank from freezing in winter. There is about five feet clearance between the ground and the towers, so a tank could be ppositioned there above ground, although this would impose additional maintenance requirements to ensure continued heating (to avoid freezing.)

I appreciate everyone's comments. Please continue.

r/

Good that the tank contains only water. Even so, steel tanks are no longer buried as as they once were. Put it above ground, or replace in underground location with material other than steel (FRP for example).

Another possibility is buried steel with passive cathodic protection system installed.

I recommend to construct a new concrete pit under the ground instead of that rusted steel tank.

Is the tank issue resolved? Did you order a tank truck to substitute or permanent lease?

I think your answers are listed above and I would agree that if the tank is just used for water (even potable) a good inexpensive solution is to use cisterns or septic tanks made from concrete. I have used these in the past and they are readily available and not expensive. You can even use two or three together to get the volume you need.

In the interim, you might want to rent a plastic tank. These guys are pretty good:

http://www.rainforrent.com/products/tanks.htm

They can also help with sorting out the details on the old tank.

Stephan

www.bradleyventures.com

some questions you may want to ask yourself. The tank stores water for what purpose? If the tanks is to be used for domestic consumption, how is the water made safe? Is underground the best for storing domestic water. Most domestic water is also filtered, how is this to be accomplished? What is the source of the water stored in the Tank? There are many more questions to ask, but this is a beginning and are some of the questions a civil engineer would ask before designing any water storage tank.

I recommend asking an inspector to prepare a technical inspection report, upon which we can suggest the proper procedure for repairing or replacing. The inspection report shall clarify type and grade of material, nominal and min. wall thicknesses, type of corrosion (uniform, localized, pitting size), places of leakage, age of tank, type of stored water and its temp., schematic tank drawings, ... etc.

Hi , It not a nuclear water cooling reservoir. Its just an old burred rusted tank and I am amazed how we are drawn to solve a problem that does not exist! He is only asking for what's cheapest way to get rid of it! Just sell it for scrap metal and replace it with whatever will serve the purpose.Lets raise the challenge guys!

Issa

Lets raise the challenge guys!

OK let us go ....

I'm not sure (what) that your question has not been talked around to some degree. Of course, your inquiry does give the answer to "why not" install another metallic tank? (Because it rusts and leaks and eventually caves in--whether or not you carry liability insurance to keep you safe from losing the land and/or improvements.) In addition to preserving surface and air space above grade, I see a another good reason to remove and--even at added expense over above-ground--to replace the existing tank. If the tank is left to rot away, it's likely to collapse, possibly at the most inopportune moment, taking down anything on top, including those pedestrians. Many counties no longer permit metallic tanks underground for just this reason; and many also will require such tanks to be (inspected and certified or) removed before backfilling, or backfilled in place. If the replacement tank is for use only for water, and the need to replace has already been established, seems to me that going ahead with taking bids is the most natural and most productive way to get the answers, and the questions, you seek. Let the installer worry about old tank disposal.

Was there more to it than this?

you are looking at a fairly large tank (approximately 8x14 feet . you can go to the ASTM guides and standards for underground water storage tanks epa will also have the guidelines for these tanks but you also need to check with your local codes to see if they superseed ASTM then you would probaly want to contact a tank manufacturer for recomendations as to materals and coatings to be used inside and outside of the tank you will probably want to install a gravel leach bec arround the tand to keep outside moisture from crooding the tand and washing the soil awayfrom the tank

good luck with your endevors

The fuel storage tank industry is undergoing a change of late in this area of Florida. Underground storage tanks constructed of fiberglass that are only 10 years old are being removed, because of more stringent fuel loss monitoring codes. If one of these tanks were available, it might be an inexpensive solution to your needs. Good luck.

Hi Sam,

While I admit I may not know exactly what you are referring to in the context of your "process-water" application, you ask a very interesting question. While the application may not be pursued as actively by the pipe manufacturers as longer large diameter pipelines, I am aware that there have been multiple projects over many years where engineers and utilities have employed large standard diameter, cement-mortar lined ductile iron piping (DIP) and othe rpipe materials in effect as sort of modular tanks (e.g. for such services as chlorine contact tanks etc.) I am not aware of problems with these pipes in such services The volume of these large pipes is e.g. illustrated in Table 17-4 pg 17-12 at http://www.acipco.com/adip/products/Sect17.pdf (e.g. three 42" DIP have a capacity of a little more than 4,600 gallons, while two 54" DIP pipes would have far greater capacity in shorter lengths).

If the tanks are at any time subjected to even quite high pressure, accidentally or on purpose, ductile iron piping is even well-known as being suited for such, though either restrained joint pipes and closures, or adequate thrust blocking must of course be employed. Outlets can be fabricated to the pipes and taps, entry-exit points, air releases, etc. can be provided wherever desired, and even in tangential orientations if this is helpful for mixing etc. Most utilities or large industries are familiar with any issues that may involve corrosion of their cast/ductile iron piping in abnormally corrosive soils, and there are also contemporary means to deal with even quite aggressive exterior soils (as can be explored through the above portal or dipra.org etc.)

I guess I can see argument in some cases as to whether many of these installations are really tanks or just big,short low flowing pipelines, but in either case I don't know what if any local preferences or regulations you may otherwise have to deal with. However, I do suspect such modular tanks can give a designer great flexibility, are of formidable impact and other strengths, can be readily shipped and handled, and can be very quickly installed by virtually any contractors familiar with large piping (and with very simple tools, procedures etc.) I don't know enough about the tank business to know how this option compares cost-wise with thinner or weaker alternatives, however.

Randy Conner

<concrete or glass fiber tank. However, it is not clear why?
>.

I may recommend Atmospheric Pressure ConcreteTank -Cylindrical below Ground/garden ID 12'X6' DEEP.Rebars will be needed embedded on Outer diameter to take the hoop stress. So also radially/circumferentially cast into bottom dish.If you wish annual cleanup then build in a 4" pipe up thro' dish centre and a radial drain -out at a few inch below top rim.Other piping IN-OUT as you need.

Lid-Better dished FRP .Lift up/replacement possible by 2 persons Lid can be see-though for UV/Sunlight

Above will be possible by any contractor in your area--and cheap /longlife/non-contaminating solution .

Iwill be scared of longterm reliability of a FRP 13' dia. Chemical fabricators may offer it.At whatPrice??

Thanks to all who have contributed to this discussion. Some notes of clarification and information follow. The task is contracted to remove the old tank and replace it with FRP of 3000 gallons, 5 foot diameter and 20 foot length, horizontal installation strapped in a cradle and anchor system of concrete on an appropriately draining base strata

The discussion of this thread have been most helpful in pointing out issues, considerations and solutions. It was important to my task completion and I thank you all.

Best Regards,

Sam