Tank Testing Nightmares as Chronicled by a Massachusetts Tank Company
Tank testing of underground storage tanks (USTs) should be a straightforward process. A tank test company employs technicians certified by the manufacturer and state in which they operate. Customers’ heating equipment or generators that each tank powers are first isolated from the tank system being tested. One or more manways are then removed. The fuel system supply, return and vent lines are then closed off or plugged. The level of groundwater in groundwater monitoring wells is then verified prior to tank testing. Tank testing equipment is inserted in the tank fill pipe or test point and the test process begins. Unfortunately, a tank testing service rarely happens as we just described and this impacts the time to test, cost of testing, and the duration that the facilities equipment is offline.
For a range of reasons, tank testing services don’t always happen in this manner. When fuel, oil, or other types of storage tanks are not properly prepared for testing, the test may be adversely affected. Use of the tank is then affected due to longer time to test. Price of testing can increase. Tank offline time can also increase.
Applications for Proactive Tank Testing
If a tank tightness test is required for your home or facility’s underground storage tank, it’s a good practice to schedule a tank inspection prior to scheduling the test. Equipment configuration changes often necessitate this important step, since many USTs were not installed with future testing in mind.
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Customers should check for these common UST requirements prior to scheduling a test:
- Groundwater monitoring well within 25 feet of the UST
- Size of fill pipe diameter greater than 2 inches
- Fill or test piping free of corrosion
- Vent pipe accessible from a rooftop or less than 16’ high
- Storage tank easily isolated from piping (tank with shutoffs or unions are ideal)
- Manifolded USTs able to be disconnected and tested separately
- UST access (Elevated or below grade USTs can be difficult to reach with test equipment)
- UST sumps accessible (tight spacing limits the use of wrenches if piping needs to be disconnected to add test plugs)
Storage tank access can sometimes be blocked by temporary structures, especially if located in a parking lot. Products such as roll-off containers or trash compactors are often installed near underground tank pads and can cover tank manways. Applications and examples of high traffic areas include vehicle access to facility loading docks, hospital entrances, and marine boat ramps. Traffic restrictions should be in place prior to performing a tank test.
Underground Storage Tank Testing Companies
The level of training and certification required to use tank testing methods are provided by each manufacturer of tank testing equipment. Each one of the test methods are evaluated by the National Work Group on Leak Detection Evaluations (NWGLDE) and certified by a 3rd party to meet EPA leak detection performance requirements. The technician performing the tightness testing must be trained and certified for the equipment they use and include their certification number on the tank test report. The State of NH also requires the technician to have an International Code Council (ICC) Certification for UST Tank Tightness Testing. A list of certified tank testing companies can be found on the NH UST Program Resources Page.
EPA Requirements for Tank Testing
The requirement for tank testing is typically covered by Automatic Tank Gauges (ATGs) installed at regulated facilities. ATGs use the ‘Continuous In-Tank Leak Detection Method’ which meets EPA leak detection requirements. If the monitoring equipment has failed or is in an alarm condition then the state or local fire department can require a tightness test. A range of real estate transactions may also trigger testing. The buyer may need a written statement for the bank or insurance company that proves the UST is sound.
Consumptive use tanks (tanks that supply fuel to heating systems or gas to fleet vehicles) larger than 1,100-gallons, do not have the same leak detection requirements as regulated tanks. An interstitial monitor that is capable of detecting leaks from the inner wall to the outer wall meets the leak detection requirement for Consumptive Use tanks.
USTs connected to emergency generators and fire pumps, larger than 1,000-gallons and installed prior to January 2, 2015, that do not have ATGs, are required to undergo annual tightness tests. Owners of USTs, smaller than 1,000-gallons, can utilize weekly tank gauging per CMR 80.26(7) as it satisfies the leak detection requirements or perform monthly gauging and annual tightness testing.
Tank Testing Nightmares
In our experience with tank testing, there are a number of tough jobs that we refer to as “nightmare” projects. The following are examples of problem jobs and images of properly installed tanks to highlight the difference between a poor installation and a successful one as it applies to tank testing.
The UST in Figure 1 had three elbows coming off the 4” riser pipe which connects to an aboveground spill bucket. This configuration is a “nightmare” for tank testers because there is no direct access to the tank. A tester is not able to measure the fuel and water levels, or the diameter of the tank, which is critical information for testing an underground tank. Also, technicians need a direct access point to install their volumetric and non-volumetric instruments. Figure 2 is an example of an ideal test point. The fill pipe is 4” diameter and is piped straight to the top of the UST.
Figure 3 is an example of galvanic corrosion. The fill pipe is so corroded that the aluminum drop tube has bonded to the steel riser pipe. Test instruments cannot be inserted into the fill pipe if a rusted part like this drop tube is blocking access. Figure 4 shows a drop tube inside a riser pipe of a well-maintained UST.
UST sumps are designed to contain piping leaks but they will hold 50 to 100-gallons of water if left exposed to the elements. Nothing slows down a tank tightness test like submerged pipes and fittings. The water accumulation in Figure 5 can be avoided by installing a manway larger than the diameter of the sump and installing a covered sump. Figure 6 shows an ideal sump and manway installation. The containment sump is inside this 36” manway. A compression lid will cover the piping so any water that enters the manway will pass into the crushed stone around the sump.
The interstitial space test point in Figure 7 is filled with soil. Tank testers aren’t usually equipped with tools for removing soil in tank sumps. The tank owner should check this manway on monthly walk-through inspections and clear any debris buildup. Figure 8 shows a clean, dry test point. It not only provides easy access to the interstitial test point but will reduce corrosion and prevent soil and water from entering the piping.
The vent pipe in Figure 9 is mounted in a location that is inaccessible for tank testing. It is also not installed to code despite it being a school building. The vent is mounted too close (must be at least 24 inches away) to a window which will allow fuel vapors to be drawn inside. The building in Figure 10 shows an underground tank vent pipe properly mounted above the roofline. This location is safe and provides rooftop access to the vent so it can be plugged for testing.
Common Causes of Tank Testing Failures
Underground storage tanks are not usually the source of a leak detected during a tank tightness test. It’s typically a fitting connected to the tank that fails. Here is a listing of tank failure points starting from most to least common:
- Fill Pipe – Fill pipes are the most actively used fitting in an underground tank. Vibration during the delivery of fuel is the primary reason for this pipe loosening.
- Spill Buckets – Groundwater regularly entering a spill bucket will result in rust and corrosion developing at the riser pipe attachment.
- Vent Pipes – a vent pipe can become loose just below grade, or above grade joints may dry out, depending on the location of the tank and the support structure for the pipe.
- Tank Manways – Leaks found at manways usually occur if the sump protecting the manway is not watertight. The rubber seals will dry out over time and need to be replaced. A manway leak is usually confirmed by injecting helium in the tank and tracing the leak with a helium sensor.
- Level Gauges – These gauges will allow air in through the gauge pump so they must be disconnected and the line plugged.
- Level Sensor Mount Points – USTs that have Automatic Tank Gauges use an electronic level sensor to measure the fuel level. These need to be removed prior to testing because the seals aren’t always airtight.
- Fuel Supply and Return Lines – It is rare to have a leaking supply or return line but small leaks do occur in the threaded fittings in UST sumps. Typically a visual inspection will catch this leak prior to testing.
- Check Valves – Check valves prevent siphoning and are used to keep a fuel pump primed. Check valves can wear over time and allow air to pass through the valve. Isolating USTs by disconnecting and plugging supply and return lines removes check valves from the test.
Reporting Tank Tightness Test Failures
In Massachusetts, the owner/operator and fire depart must be notified within 24 hours of a UST or piping that fails a tightness test. Any piping that has failed must be isolated and emptied immediately. A failing UST must be emptied within 72 hours of a failed tightness test. Once the tank or piping is repaired it must be tested within 30 days.
New Hampshire requires notification of the Department of Environmental Services (DES) within 24 hours after a test failure. The tank owner must investigate the cause of the leak within 7 days or temporarily close the system within 7 days and permanently close within 30 days.
Declaring a Tank “Tight”
An underground tank system is declared tight when testing is performed in accordance with the EPA “Standard Test Procedure for Evaluating Leak Detection” and is capable of detecting a leak of 0.1 gallons/hour with a probability of detection of no less than 95%. After January 1, 2018, the testing systems are required to have a detectable leak rate of .05 with a probability of detection of no less than 95%. Equipment manufacturers must show their leak detection methods meet these performance requirements. Ask the underground tank test company that performs your test for a copy of the evaluation results to keep on file with your report. This will satisfy the EPA’s record-keeping requirement.