Above Ground Storage Tank or AST

Above Ground Storage Tank or AST Common Questions

 

Above Ground Storage Tank or AST, like an Underground Storage Tank (UST), contain heating oil for the purpose of heating homes and buildings. There are specific differences between the two tanks and these are some of the most common questions we are asked regarding ASTs.

What is an above ground storage tank or AST?

Homes, apartments, farms and some businesses that are currently or were heated using diesel heating oil, used an above ground storage tank (AST) to store the heating oil. ASTs are most commonly mounted on a stand or a ground pad either outside or in a basement. ASTs can also be partially buried in the ground, usually in a basement or crawlspace.

Since it isn’t underground, do I really need to be worried about an AST?

Yes, even above ground tanks can leak, resulting in contamination of soil and drinking water supplies. Any oil spill can pose a serious threat to human health and the environment, regardless of where the tank is located.

What is the difference between an AST and a UST?

The distinct difference between the two tanks is this:

  • If the tank and its piping is located 10% BELOW ground surface it is considered a UST, anything ABOVE 10% ground surface is considered an AST.
  • Another exception is that, ASTs are not regulated by the DEQ, therefore not governed the same way as a UST.

For example, if a UST is leaking above 50 PPM (parts per million) the contractor is required to report this to the DEQ and is subject to remediation, based on the level of contamination. After the clean-up has been completed, the UST is then decommissioned and registered with the DEQ. This scenario can also be compared for an out of service underground storage tank, once the tank has been decommissioned it can then be registered with the DEQ.

The circumstances for an AST are different. When an AST is or has leaked, is no longer in-service, or the homeowner is switching to a new heat source, the tank can simply be removed, no decommissioning or registration with the DEQ is required. However, like decommissioning an underground storage tank, each AST removal can bring about a different set of considerations.

What to do with an Above Ground Storage Tank AST when decommissioning is not an option

If you don’t decommission and register the AST with the DEQ, what do you do?

First, we would need to determine where is the tank located?

  • Outside the home
Above Ground Storage Tank or AST

Above Ground Storage Tank or AST – Exterior AST secured to concrete pad foundation.

  • In a basement or crawlspace, with a separate exterior access
Above Ground Storage Tank or AST

Above Ground Storage Tank or AST – AST located in basement with exterior access.

  • In a basement or crawlspace, with access through the home only
Above Ground Storage Tank or AST

Above Ground Storage Tank or AST – AST located within a crawlspace, no exterior access. For this AST to be removed, it will need to be cut into pieces.

Regardless of where the above ground storage tank or AST is located on your property, it is very important to have it removed by a licensed contractor with pollution insurance. If the AST is removed by a general contractor, and they usually DO NOT have pollution insurance, and heating oil is spilled in the house or the yard, the homeowner will be left with the clean-up, not the contractor.

Once the location has been determined:

  • All heating oil and sludge are pumped out, the tank removed and disposed of via recycling.
  • Depending if the tank is on the exterior or interior of the home determines if the tank can be removed as one piece or if it will need to be cut into portions and carried out of the home.
  • If applicable, the fill and vent are removed and holes would be patched.
    • Removing or concreting over the fill eliminates the possibility of an accidental fuel re-fill.
Above Ground Storage Tank or AST

Above Ground Storage Tank or AST – AST Vent (the larger pipe) and fill pipe.

When an Above Ground Storage Tank (AST) Leaks

What would cause an AST leak?

There are numerous reasons an AST can leak; improperly secured tanks, tank corrosion, equipment or support failure, overfilling the tank, or it could be as simple as human error.

Above Ground Storage Tank or AST

Above Ground Storage Tank or AST – Tank that has fallen down, if the contents are not pumped out, diesel fuel would be leaked into the yard.

My AST is leaking, what should I do?

  • Place a bucket underneath the tank to catch the release
    • If the AST is within the home, block all floor drains to prevent discharge into a drywell or sewer
  • Call a qualified heating oil tank provider that can respond to and clean-up a leaking tank
    • The AST would be pumped of all residual liquids
    • Clean-up would be performed to remove any heating oil contamination
Above Ground Storage Tank or AST

Above Ground Storage Tank or AST – Leaking AST, small bowl has been placed underneath the leak to catch the heating oil.

Septic Tank Decommissioning

Septic Tank Decommissioning Common Questions

What is a septic tank?

A septic tank processes wastewater from the home and consists of two main parts, the tank and a drain field.  It encompasses a piping connection, allowing the waste to flow from the home, through the tank and into the drain field, these connections are made through a T pipe, allowing liquid to enter and exit without disturbing the surface above.  The septic tank treats the wastewater and allows the separation of solids and liquids, once broken down the solids remain in the tank while the liquids drain into the leach field.

Septic tanks may be concrete or metal, 5 to 7 feet long and 5 to 7 feet deep, and will be located 5 to 30 feet away from the home.

Are there dangers associated with abandoned septic tanks?

Septic tanks that are buried underground are susceptible to corrosion, thus weakening the stability of the structure. The instability can cause the system to collapse, causing serious injury or death. Septic tanks contain dangerous gases due to the breakdown of decomposing matter, falling into a tank can cause the possibility of being overcome by noxious gases.

How do I know if I have a cesspool or septic tank on my property?

Within the Portland Metro area, there are two methods that may help determine if you have a cesspool or septic tank on your property:

  • For a general rule:
    • If your home is east of the Willamette River, most systems installed were cesspools.
    • If your home is west of the Willamette River, most systems installed were septic tanks.

How do you find a septic tank?

The location of the system would need to be determined by sending out a technician to the property.  The technician locates the main plumbing stack that comes through the roof and visually extends a straight line from the exterior foundation line.  From the foundation, the technician would follow the visual straight line out to the septic tank, between 5 to 30 feet from the home.

Decommissioning of a septic tank

How do you decommission a septic tank?

The proper septic tank decommissioning permit will need to be obtained for the city and/or the county the septic system is located in.

EcoTech uses excavation equipment to dig to the top of the structure to expose and open the septic system.  Once accessed and per OSHA regulation, shoring of the area around the system is completed to prevent collapse of the shaft and to ensure the safety of our technicians.

Our technicians will then inspect the interior of the tank, and pump any liquid or sludge that may be present.

Contingent on the city and/or county permitting process, inspection of the system may need to take place prior to filling the tank.  Inspection may also need to take place after the tank has been filled, depending on permit requirements.

When the tank has been pumped of all sludge, and all relevant inspections completed, the tank can be filled with either sand or gravel.  Once the septic tank is decommissioned, the technicians would replace the soil overburden, bringing the area back to surface grade, along with a closed permit for the decommissioned septic tank.

Septic Tank Decommissioning

Septic Tank Decommissioning – Dug down and exposed septic tank

Septic Tank Decommissioning

Septic Tank Decommissioning – Roped off septic pit for safety

Septic Tank Decommissioning

Septic Tank Decommissioning – Broken terracotta pipe, this is part of the system that allows wastewater to drain from the home. When the pipe is broken, this allows waste to seep into the yard.

Septic Tank Decommissioning

Septic Tank Decommissioning – Filled septic tank, with T piping junction of metal pipe to terracotta pipe.

Septic Tank Decommissioning

Septic Tank Decommissioning – Filled septic tank, with T piping junction of metal pipe to terracotta pipe.

Septic Tank Decommissioning

Septic Tank Decommissioning – Filled septic tank, ready for overburden to be replaced

For more information on local cities requirements on septic tank decommissioning within the Portland Metro area, please click on the following links: