Petroleum Contamination

The Weights and Measures Division monitors petroleum quality by checking all motor and heating fuels. Providing high quality uncontaminated petroleum products is vital in today's business climate.

Protect the Environment and Product Quality

Providing high quality, uncontaminated petroleum products is vital in today's business climate. Customers expect their cars and trucks to perform flawlessly on the gasoline or diesel fuel they buy. They expect their vehicles to start, accelerate, and deliver good mileage.

The operator of a retail petroleum business plays an important role in maintaining the level of product quality that helps develop and keep satisfied customers. Clean, uncontaminated petroleum products contribute to a cleaner and healthier environment, and to automotive safety.

Handling and disposal of contaminated fuel can contribute to long term environmental damage. It can also be costly to station owners.

In the short term, it is expensive to repair fuel-related damage to customers' cars. A station owner's insurance rates can increase as a result of repeated problems.
In the mid term, failure to care for the environment will cost customers. Many customers are increasingly aware of the need to preserve the environment -- they will not patronize a business that is careless about the environment.
In the long term, any environmental damage affects station owners and their children and grandchildren. Petroleum products spilled in the ground will end up in the water supply. Station owners who don't want to drink gasoline, should not spill any.

Prevent Storage Tank Leaks

Tank maintenance is the first step toward preventing petroleum product contamination. Tanks must be leak free. Above ground and underground storage tanks are subject to U.S. Environmental Protection Agency regulations, enforced by the Minnesota Pollution Control Agency (MPCA).

Station owners must regularly monitor tanks for leaks. Procedures for detecting leaks and preventing corrosion and spills are specified in federal regulations. The procedures vary depending on the age, type, and size of the tanks, and the type of piping between the tanks and pumps.

Avoid Water Entry into Storage Tanks

In Minnesota's climate, water is the most common contaminant in petroleum storage tanks. Water in tanks requires cleanup actions that range from pumping the water out of the tank, to removing all the product stored in the tank . It is critically important to keep water out of tanks.

To prevent water contamination:

Make sure that fill pipes are located on high ground, and that snow melt and runoff are directed away from them.

Check fill pipe caps. They must be water tight. Seals and latches must be in excellent condition. Replacing a fill cap is a lot less expensive than replacing a tank full of contaminated product, or paying to repair fuel-related damage to a customer's car.
Check vent pipes. They must have special caps to allow ventilation and prevent rain water entry. Faulty or missing vent caps are a common, but frequently overlooked, source of water contamination.
Newer tank installations have large catch basins surrounding the fill pipe openings. These basins are designed to catch product spills and overflow during tank filling. They're also great for catching and holding water. Catch basins must be kept clean and dry.
Many catch basins are equipped with a drain valve. This is not a water drain. It was designed to drain spilled product back into the storage tank. Water and dirt drained from catch basins will drain directly into storage tanks. Water and dirt must be removed from catch basins with a pump, mop, or sponge.
Water lying at the bottom of the storage tank can cause rust-through and leaking. Water removed from the bottom of a storage tank is loaded with toxic substances. Please don't pump water or petroleum products onto the apron, or into a storm sewer or drainage ditch.

Avoid Unloading Errors

Unloading the wrong product into a storage tank is another common cause of product contamination. To help prevent these errors, state law requires an identification tag which must be constructed of one 3-1/2 inch by 3-1/2 inch piece of aluminum or stainless steel. All surfaces of the tag must be coated with a permanent enamel paint or powder coating. The coating must be light blue for gasoline and alcohol products and dark green for petroleum distillate products. Lettering must be at least three-eighths of one inch high, and printed on the tag with permanent enamel paint or powder coating. Lettering must be black for gasoline and alcohol products and white for petroleum distillate products.

To help the transport driver avoid overfilling, the department recommends that the capacity of each storage tank be marked on the fill pipe. When an unloading error occurs, the mixed or contaminated product must be removed from the storage tank. Pumping is a potential source of spills. The easiest way to avoid a spill is to prevent unloading errors by clearly marking tanks.

Please note: Color-coded or marked storage tank covers are not acceptable. Covers are often lost during snow plowing, exchanged during inventory checking, or flipped over when product is delivered.

Store Oxygenated Gas Properly

Oxygenated gasoline is more prone to contamination than straight gasoline. It requires special handling. Gasoline sold in Minnesota must be blended with ethanol. Ethanol is the only oxygenate used in Minnesota.

There are two important factors to consider when storing oxygenated gasoline:

Ethanol and other oxygenates act as solvents, or cleaning agents. Storage tanks must be clean before filling with oxygenated gasoline.

Gasoline will not mix with water -- oxygenates will. Ethanol has a higher water tolerance than other oxygenates, but ethanol's ability to absorb water is limited. When storing oxygenated gasoline, tanks must be dry before filling, and must be kept dry.

If there is too much water in storage tanks, the oxygenate will separate from the gasoline. This is called a phase separation and will cause a layer of gasoline on top of a layer of oxygenate/water blend. The amount of water needed to cause a phase separation is temperature related. If the oxygenate/water blend is deep enough, it will be picked up by the pumps and delivered into customers' cars.

When a water/oxygenate blend develops at the bottom of a storage tank, it must be pumped out. Again, pumping is a potential source of spills and subsequent environmental contamination. The easiest way to avoid a spill is to prevent water problems. Check tanks, fill caps, and fill pipe vents regularly.

What to Do if Contamination Occurs

Water contamination in storage tanks. Water pumped from the bottom of a storage tank may be considered a hazardous waste, depending on the level of dissolved contaminants like rust, dirt, and petroleum products.

In most cases, this liquid will have to be treated as hazardous waste. For information on handling and disposal of wastes, station owners should contact:

the county Environmental Health office, if they live in the Twin Cities area;
the MPCA Hazardous Waste Generator Unit (651-297-8332) in the Twin Cities or 1-800-657-3864 statewide);
the Minnesota Technical Assistance Program (612-624-1300) in the Twin Cities, or 1-800-247-0015 statewide).

For assistance in having tanks pumped, station owners should contact their petroleum equipment repair company.

Oxygenated fuel that has separated. Station owners experiencing a phase separation problem should follow the recommendations above to dispose of water and water/oxygenate mixtures pumped from tanks. In addition, the gasoline that remains in tanks after removing a water/oxygenate mixture will not meet state requirements for oxygenated gasoline. The fuel supplier should be contacted for assistance in blending and handling the remaining product.

Product unloading errors. A contaminated product may have to be pumped from a storage tanks if a transport driver has unloaded the wrong product into the tank. When an unloading error occurs, contact the fuel supplier for assistance in correcting the problem.

For complete information on regulations and procedures, contact the MPCA. In the Twin Cities, call 651-297-8679. From outside the Twin Cities, call 1-800-657-3864.

Water & Ethanol Blends

Facts about water, ethanol and how the two can combine.

How do you know if there is water in a station's gasoline?

Water is heavier than gasoline and, if present, will settle to the bottom of a storage tank. Environmental regulations require new storage tanks to be equipped with electronic sensors which alert the station operator if water is present.

The Department of Commerce Weights and Measures Division tests stations' storage tanks for water during its routine inspections. Tanks containing a gasoline/ethanol blend absorb water which may not be detected by either the tanks' sensors or the Weights and Measures investigator. Ethanol acts very much like the Isopropynol some people add to their vehicles' gas tanks in the winter. It absorbs the water and prevents gas line freeze. In small amounts, water in a gasoline/ethanol blend will not affect a car's performance.
How does a station operator remove the water from a phase-separated blend?

The best way to correct a water problem in an ethanol/gasoline tank is to drain the tank completely and replace it with uncontaminated product. An alternate method is to remove the ethanol/water mixture from the bottom of the tank and then wait 24 hours. The product CANNOT be sold to the public during this time. If more ethanol/water precipitates out, the operator must remove it from the tank and wait another 24 hours.

If no more ethanol/water precipitates out, the tank may be `topped off' with a mixture of ethanol and gasoline. It is very important to contact the Weights and Measures Division when using this method since the quantities of ethanol and gasoline added will depend on the size of the tank, the amount of the product remaining, and the amount of ethanol removed from the original blend. When the Weights and Measures Division determines that the product in the tank meets all octane and oxygenate requirements, the product may again be put up for sale to the public. The operator then contracts with a licensed hazardous waste carrier to transport the ethanol/water mixture which was removed from the bottom of the tank. The hazardous waste operator must dispose of the ethanol/water mixture in accordance with environmental regulations.
If ethanol absorbs water, how can you have water contamination in a gasoline/ethanol blend?

A gasoline/ethanol blend can absorb a certain amount of water. In general, the greater the percentage of ethanol in the blend, the larger the amount of water the blend will hold. Also, the higher the temperature, the greater amount of water the blend will hold. A blend that contains the maximum amount of water it can absorb for that temperature and percentage of ethanol is saturated.

If a saturated blend drops in either temperature or percentage of ethanol, the water will start to precipitate (fall) out of the solution and settle at the bottom of the tank. This water will be mixed with ethanol since ethanol bonds more easily with water than gasoline. The gasoline mixture at the top will still be saturated. It will continue to precipitate out a water/ethanol mixture as the percentage of ethanol drops until there is either no more water in the gasoline, or another saturation point is reached (if the temperature is rising at the same time, for example). This is what is referred to as a phase separation. A phase separation can occur in a storage tank or in a vehicle's gas tank. As soon as water/ethanol begins to precipitate out, an in-ground tank's sensors will be able to detect its presence and signal the operator that there is a problem.
If station operators do not intentionally water down their product, how does water get into a station's storage tank?
If water might not be detected, what prevents station owners from "watering down" their gasoline/ethanol blends?

Common sense. Gasoline/ethanol blends cannot absorb unlimited amounts of water. The amount they can absorb without causing customer problems depends on the volume of product, the percentage of ethanol, the temperature of the station's in-ground storage tank, the temperature of the customer's gas tank, and the amount of ethanol already in the customer's gas tank.

It would be almost impossible for station owners to water down their product and be sure that none of their customers would experience car problems. Station owners are liable for repairs if they sell water contaminated gasoline. They may also be subject to criminal prosecution if they are intentionally adding water to their product. Most station owners want to avoid those consequences and maintain a good reputation with their customers.

In addition, the Weights and Measures Division regularly samples diesel fuel and gasoline around the state and analyzes them in its laboratory. Laboratory tests can detect even small amounts of water in gasoline/ethanol blends. Station operators are usually happy to be informed of any water found so that they can take corrective action before it causes their customers problems.
Is water contamination in gasoline a big problem in Minnesota?
What happens if people buy phase-separated gasoline?
What should I do if I suspect I have purchased water contaminated gas?

Drain your tank and change your fuel filter. This is extremely important for carbureted vehicles since water can damage the carburetor. If the gasoline appears cloudy, or if it separates into visible layers, it probably contains water. Contact the station operator. (A canceled check or receipt to show when you purchased the gasoline is useful.) Most operators will be happy to work with you if the contaminated product came from their station.

If the operator is sure that the station's product is not contaminated with water, contact the Weights and Measures Division (651-539-1555). An investigator will be sent out to test the tanks and to collect samples for laboratory analysis. Make sure to call the Division as soon as possible. Most stations receive fuel shipments several times a week. It is best if the investigator can collect samples before another shipment has arrived. The investigator will contact you with the test results. In some cases the investigator may request a sample of the gasoline you drained from your tank.

If the station's product was not contaminated with water, the problem may lie with your vehicle tank. Tanks which are allowed to sit empty over the winter, or tanks with missing or improperly fitting gas caps may collect water. Keeping your gas tank full in the winter months and making sure that your gas cap is tight can reduce this problem. Remember, a rag stuffed into a fill pipe acts as a wick for moisture; it will not keep water out of your tank.
Will everyone who buys phase-separated gasoline experience car problems?

Fortunately, no. Very few people usually experience problems. Many people buying a water-saturated product will still have some unsaturated gasoline/ethanol blend in their tanks. Most people's gas tanks are often warmer than stations' in-ground storage tanks during the spring, summer, and fall months. This means that a blend which is saturated in the ground will no longer be saturated in the car's tank. In a few rare cases the water/ethanol phase in a contaminated tank may reach the level of the tank's discharge pipe. Usually a phase separation is detected and corrected long before this is the case. Any customer who purchases part of the water/ethanol phase will experience difficulties immediately.