So you have a few underground storage tanks? Regulation required the installation of corrosion protection and spill / overflow protection on the tanks and lines by December 1998 for gasoline, diesel fuel, kerosene, alcohol, and other extremely flammable substance tanks. Any fuel oil tanks installed after 1985 have no upgrade requirements.

Even if you do not need to upgrade, you may want to remove and replace your existing tanks. Compounding the problem is the inability of inventory control to discover a leak before it becomes a major release. The tank owner has to balance the risk of a leak over the cost of replacing the tank with an upgraded system. The following methods are available to test a tank for leakage:

• Tank tightness testing
• Test boring
• Vapor monitoring wells
• Tracer gas release
• Installation of electronic monitoring system

Tank Tightness Testing involves filling the tank and piping entirely with fuel and measuring for small amounts of leakage, correcting for temperature, pressure and tank expansion / contractions. This test can usually be accomplished in less than a day if the tank fitting has easily removed spill / overfill devices.

The cost of a tightness test is approximately $500 to $800 per tank.

Some disadvantages of using tank tightness testing are:

• The tank has to be completely full of fuel, which will have to be removed if a leak is discovered.

• The test will not tell you where the tank is leaking - piping, fitting, tank bottom, etc.

• The test itself can release more fuel into the environment.

• The test is a one-time glimpse of the tank's environment and will not ensure that leaks may not occur shortly after.

Test Boring will discover any fuel contamination in the soil around a tank. By drilling bore holes in the excavation area around a tank, soil samples can be tested for the presence of fuel hydrocarbons. This contamination can be tested for concentration and depth to determine source of leakage. The depth and concentrations of the soil vapors can also determine a surface spill or tank leakage.

Cost of soil boring around tank averages $500 to $1,000, depending on difficulty.

The disadvantages of using soil borings to determine the leakage are:

• Exact determination of tank leakage is not possible.

• Soil borings in "tight" soils will not show leakage.

• Possible damage to underground wiring that is not properly marked.

Vapor Monitoring Wells are installed in the boring around the tank if little or no contamination is present. Their purpose is to provide a monitoring point for vapors, which are released in the soil by the fuel hydrocarbons. If a slight contamination problem has occurred because of fuel spilled on the land surface, the concentrations of hydrocarbons will dissipate with time. If a tank is leaking, the concentration of hydrocarbons will increase.

The cost of vapor monitoring wells is approximately $500 to $800.

The disadvantages of this system are:

• A release has to occur to be discovered.

• Tight soils may delay discovery.

• Manual testing equipment is expensive.

Tracer Gas Release is a new development in leak detection. A special chemical tracer substance is released into the tank and allowed to move through the system for two weeks. Soil vapors are then pulled out of the soil through tubes driven into the soil around the tank. The gas is analyzed for the presence of the special tracer gas. If the gas is present, a leak has occurred and the location can be determined by comparing depth and concentration.

The cost of tracer testing starts at $1,500 and goes up, depending on complexity.

Disadvantages are:

• High cost.

• Limited availability.

• Inability to predict future leaks.

Electronic Monitoring Systems are the most responsive leak detection devices. The installation of an electronic probe into the tank and the installation of the monitoring system will require modifications to the tank. If the system is properly designed, it can be reinstalled in a new tank upon replacement.

The cost of an electronic monitoring system is from $4,000 to $6,000, plus installation.

Advantages are:

• Detect leakage before major release occurs.

• Expedites inventory control and recordkeeping.

• Monitors tank condition constantly.

Disadvantages include:

• High cost.

• Requires installation of wiring and probe into existing tank and the replacement tank must be the same diameter.

In summary, many forms of leak detection are available to monitor underground storage tanks. Choosing the best system to protect the environment depends upon availability, budgetary constraints and local conditions.

If a tank is located in an area of high groundwater or porous soils, immediate forms of leak detection will be important. If a tank is located in dry, "tight", clay soils, less expensive forms of leak detection will suffice.

Scheduling tank removal can be accomplished on a tight budget by performing some form of leak testing on the tanks and removing only the tanks which are currently leaking. Installation of a leak detection system will allow use of the tanks until they can be fit into a long-term replacement plan, while ensuring that they do not seriously contaminate the environment.

Think you have a leaking tank? Many states have special assistance programs to help owners of leaking tanks. Check with your local or state agency for assistance. In Minnesota, the "Petrofund" provides monetary assistance to owners of leaking tanks to off-set the costs of removal and cleanup. The Petrofund has been extended to 2005, so a little more breathing room has been added for your removal and cleanup projects. The Petrofund will reimburse up to ninety percent of clean up costs in the event of a leak, so it is in your best interest to get your tanks pulled / upgraded now. Just because the date has been extended doesn't mean Petrofund money will be available through 2005. When the money is gone, the program will close, regardless of the date. Don't be left with a pile of stinky soil!