June is National Homeownership Month, a perfect time to celebrate the joys and responsibilities of owning a home. Promoted by organizations like the National Association of Realtors® and the U.S. Department of Housing and Urban Development (HUD), this month reminds us of how homeownership builds wealth, stability, and strong communities. As you buy or sell a residential property, addressing potential environmental hazards early is key to a smooth transaction and long-term peace of mind. At Curren Environmental, we specialize in helping homeowners, buyers, and sellers identify and resolve these issues, ensuring your real estate journey is safe and successful.

Why Environmental Inspections Matter in Residential Real Estate

Many older homes or properties in certain regions hide environmental risks that can affect health, safety, and property value. Common concerns include buried oil tanks from former heating systems, mold growth, lead-based paint, and asbestos materials. Ignoring these can lead to unexpected repair costs, health issues, or complications during sale. Proactive inspections during due diligence protect buyers from inheriting problems and help sellers disclose issues transparently, avoiding delays or disputes.

Since 1998, Curren Environmental has served New Jersey, Pennsylvania, and Delaware, providing targeted environmental services for residential transactions. Our goal: smooth closings with no surprises.

Key Services Curren Environmental Offers for Home Buyers and Sellers

We focus on the most relevant inspections for single-family homes and residential properties, delivering fast, reliable results with in-house expertise and equipment.

Tank Sweeps with Ground Penetrating Radar (GPR)

Many homes built before the 1980s used underground oil tanks for heating. Abandoned tanks can leak, contaminating soil and groundwater—a major red flag in transactions. Our tank sweeps use advanced GPR technology to non-invasively scan for buried tanks or anomalies. If detected, we handle safe removal and closure, compliant with state regulations (NJDEP, PADEP, DNREC), preventing future liability.

Underground Storage Tank (UST) Removal and Soil Remediation

If a tank is found or suspected, we expertly remove it, test the surrounding soil, and remediate any contamination. This turnkey service resolves issues quickly, allowing transactions to proceed without delays.

Mold Inspections

Mold thrives in damp areas and can cause respiratory problems. We conduct thorough visual assessments, air/surface sampling, and provide remediation guidance if needed—essential for buyer safety and seller disclosure.

Lead Paint Inspections

Homes built before 1978 often contain lead-based paint, hazardous, especially to children. Our certified inspections identify risks, helping families make informed decisions and comply with disclosure laws.

Asbestos Testing

Common in older insulation, flooring, and siding, asbestos fibers pose serious health risks if disturbed. We sample and test materials, advising on safe management or abatement during renovations or sales.

Our dedicated project managers oversee every step, ensuring clear communication, timely reports, and cost-effective solutions—no subcontractor delays or markups.

Ensuring Smooth Residential Transactions

Environmental concerns don't have to derail your home sale or purchase. By addressing them early—often during the inspection contingency period—buyers gain confidence in their investment, and sellers can market properties as "clean" and ready. We've helped thousands of residential clients close deals worry-free.

This National Homeownership Month, prioritize a healthy, safe home. Partner with Curren Environmental for the right inspections tailored to residential needs.

Ready for a seamless transaction? Visit www.currenenvironmental.com to explore our services or schedule a consultation. Here's to your dream home—and a brighter future!

Hidden underground storage tanks pose serious environmental and financial risks to property owners. Whether you're buying a new property or suspect your current one may have undisclosed tanks, a professional tank sweep (also called a geophysical survey) is essential for locating these buried hazards before they become costly problems.

The Right Tool for the Job: Why GPR Beats Metal Detectors

When most people think about finding buried metal oil tanks, metal detectors seem like the obvious choice. However, this assumption can lead to missed oil tanks and false readings. Here's why:

The Metal Detector Problem: Underground environments contain countless metal objects—nails, pipes, rebar, natural iron deposits, and decades of buried debris. A metal detector will signal on all of these, creating a confusing maze of false positives that obscures actual tank locations as well as leads to exploratory digs. 

The GPR Advantage: Ground Penetrating Radar (GPR) works differently. Instead of detecting metal, GPR sends electromagnetic pulses into the ground. When these signals encounter any solid mass—whether it's a tank, void space, or density change—they bounce back to the surface unit. This creates a detailed subsurface image that trained technicians can interpret to identify tank-like anomalies while filtering out irrelevant metal debris.

Experience Makes the Difference

Having sophisticated equipment is only half the equation. The success of any oil tank sweep depends heavily on the technician's experience and knowledge.

Why Oil Tank Removal Experience Matters: At Curren, our technicians don't just operate scanning equipment—they've actually removed oil tanks from the ground. This hands-on experience with various installation methods, depths, orientations, and tank types provides crucial context that pure equipment operators lack.

No Standard Installation: Petroleum tanks were installed in countless ways over the decades. Some are horizontal, others vertical. Installation depths vary wildly. Some tanks were professionally installed while others were DIY projects with unique configurations. Only technicians who have encountered these variations in real removal projects can accurately interpret scanning data.

When Equipment Isn't Enough: A Real-World Case Study

Recently, Curren performed an oil tank sweep using over $50,000 worth of advanced scanning equipment. The sophisticated GPR and other instruments detected no subsurface anomalies that would indicate a buried tank.

However, our experienced technician observed multiple on-site clues pointing to historical oil heat usage. Combined with pre-survey historical research suggesting oil heating, the technician suspected a tank remained on the property despite the equipment readings.

The key insight? The technician determined the most likely tank location was beneath a building addition—an area physically inaccessible to our scanning equipment.

The Outcome: Months later, the property owner contacted us after removing interior flooring and discovering the leaked tank exactly where our technician suspected—buried beneath the addition, where no scanning equipment could reach.

The Bottom Line

This case perfectly illustrates why professional oil tank sweeps require both cutting-edge equipment and experienced interpretation. While GPR technology provides the best available subsurface imaging, it takes a seasoned professional to:

• Recognize site clues that equipment might miss
• Understand historical installation patterns
• Identify areas where physical access limitations affect survey results
• Correlate multiple data sources (equipment readings, visual clues, historical research)

When it comes to protecting your property investment from underground storage tank risks, don't settle for equipment alone—choose professionals with the experience to interpret what they find and, just as importantly, what they can't access.

• Curren was unable to scan under the addition. Based on the location of noted historical oil usage,  it is suspected that a heating oil UST is present under the addition.

                   

 

I am confident most companies would have missed the oil tank.  I say this because in the same week we dug up a pile of stone that a company said was an oil tank, the stone did have a Metallic signature, it just was not a tank. 

Environmental Questions?

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The Problem with Metal Detectors for Underground Storage Tank Detection 

Have you ever used a metal detector at the beach? You probably found pennies, nickels, dimes, maybe some paper clips or a thumb tack. But did you ever find that diamond ring or emerald necklace that would be like winning the lottery? Probably not.

That's exactly what it's like using a metal detector to find Underground Storage Tanks (USTs).

Why Metal Detectors Fail for UST Detection

Here's the fundamental problem: metal detectors find ALL metal, not just underground storage tanks. Consider what surrounds every home:

• HVAC units and air conditioning systems
• Chain-link fencing
• Reinforced concrete with rebar
• Underground utilities and pipes
• Electrical conduits and wiring

When you hire someone with an $800 metal detector who charges $200 to essentially "find a penny," you're not getting the precision you need for underground storage tank detection.

The Hidden Costs of Inaccurate Tank Detection

Real Case Study: A homeowner purchased a property after having a metal detector scan performed. When they later tried to sell, a potential buyer hired Curren Environmental to perform a GPR scan. Result? We found a leaking underground storage tank that the metal detector had missed entirely. The remediation cost exceeded $45,000.

Don't let this happen to you.

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Why Ground Penetrating Radar (GPR) is Superior for Tank Scanning 

What is Ground Penetrating Radar?

Ground Penetrating Radar (GPR) is a geophysical method developed over the past thirty years specifically for shallow, high-resolution subsurface investigations. Unlike metal detectors, GPR uses high-frequency pulsed electromagnetic waves (10 MHz to 1,000 MHz) to create detailed underground maps.

Key Advantages of GPR for Underground Storage Tank Detection

1. Detects Non-Metallic Objects

• Finds plastic pipes and non-conductive materials
• Locates tanks regardless of material composition
• Identifies buried objects metal detectors completely miss

2. Real-Time Subsurface Imaging

• Provides immediate visual feedback
• Shows exact location and depth
• Offers adjustable digital color displays
• No waiting for data processing

3. Precision Over General Detection

• Specifically designed for underground tank scanning
• Distinguishes between tanks and other buried objects
• Reduces false positives dramatically

How GPR Technology Works

GPR operates by:

1. Propagating energy downward into the ground
2. Reflecting signals back from boundaries with electrical property contrasts
3. Creating detailed subsurface maps of solid buried objects
4. Providing real-time analysis for immediate decision-making

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Professional GPR Equipment vs. Consumer Metal Detectors 

Investment in Professional Technology

Professional GPR units cost over $20,000 and require trained technicians to operate effectively. This isn't just equipment—it's an investment in:

• Accurate results the first time
• Avoiding costly mistakes like missed tanks
• Professional expertise in interpretation
• Comprehensive reporting and documentation

Optimal Scanning Conditions

GPR performs best in:

• Unpaved areas (grass, dirt, gravel)
• Non-landscaped spaces with minimal obstructions
• Areas without heavy concrete or asphalt coverage

Note: While signals may attenuate over solid ground cover like concrete or pavers, professional GPR can still detect underground storage tanks in these conditions.

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Real-World Case Studies and Success Stories 

Case Study 1: The $20,000 Mistake

Situation: The Homeowner relied on a metal detector scan for the property purchase. Problem: Metal detector missed a leaking underground storage tank. Solution: GPR scan identified the tank location. Outcome: Tank removal and $20,000+ remediation required

 

Case Study 2: Inconclusive Metal Detective Results

Situation: Multiple properties with "inconclusive" metal detector scans. Problem: Recommendations to "dig it up" or get GPR scan. Solution: Curren Environmental GPR scanning Outcome: Definitive results without unnecessary excavation

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Frequently Asked Questions About Underground Storage Tank Detection (GPR FAQ) 

Q: How much does professional GPR tank scanning cost compared to metal detection?

A: While GPR scanning has a higher upfront cost, it prevents expensive mistakes. Curren has seen up to $500,000 in soil remediation costs. 

Q: Can GPR detect tanks under concrete or pavement?

A: Yes, though signal quality may be reduced. Professional GPR equipment can penetrate various surface materials.

Q: How deep can GPR detect underground storage tanks?

A: GPR can typically detect tanks at depths of 10-15 feet, depending on soil conditions and tank size.

Q: Is GPR safe for my property?

A: Absolutely. GPR is non-invasive and doesn't damage landscaping, driveways, or structures.

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The Bottom Line: GPR vs. Metal Detectors for Underground Tank Detection

Remember this key distinction:

• Metal detectors find anything metal in the ground
• Ground Penetrating Radar specifically scans for Underground Storage Tanks

When you're dealing with property purchases, environmental compliance, or potential contamination issues, you need precision, not guesswork.

Ready to Schedule Professional Underground Storage Tank Detection?

Don't risk the costly mistakes that come with inadequate tank detection methods. Contact Curren Environmental for professional GPR tank scanning services that deliver accurate, reliable results.

Professional GPR tank scanning protects your investment and ensures environmental compliance.

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For more information about professional underground storage tank detection services, contact Curren Environmental. Our technicians use state-of-the-art GPR technology to provide accurate, reliable results for residential and commercial properties.

Oil tank sweep inspections are gaining traction, leading to a surge of small companies equipped with metal detectors touting their professionalism. But can they truly deliver?

At Curren, we've encountered numerous oil tank sweep companies and reviewed their reports, often with disappointing results. In many cases, these one-person shops scan for an oil tank and provide a report that recommends  “oil tank removal”, which requires a few weeks to ramp up to perform with permits and utility mark out.  On the day of removal, it turns out to be little more than a sham, involving no oil tank in the ground at all. Unfortunately, clients are left feeling deceived, as their money is used for the tank removal, with no oil tank removed from underground. All the while, the real estate transaction is stalled.

It's time to choose a trustworthy partner for your tank removal needs—make informed decisions to protect your investment. What makes a great oil tank sweep inspection company? A company that removes oil tanks—one that knows oil tanks inside and out.

 

Oil Tank Sweep Fail.  The company said there was an oil tank.  No tank was found. 

Many inspections are performed when buying a home, and most are cursory visual inspections of the HVAC system, soffits, chimneys, foundation, plumbing, sidewalks, decks, swimming pools, etc.  These building components are commonly evaluated as part of your home inspection.  What is missed by many buyers is the environmental liability aspect of purchasing a home. Environmental can be asbestos, radon, mold, lead paint, and oil tanks.  Of all these environmental liabilities, oil tanks represent the biggest risk relative to remedial costs.  A hidden underground oil tank can cost a couple thousands of dollars to a new homeowner if it's not caught during the inspection process.  Worse is when an oil tank leaks, which can lead to costs in the tens of thousands of dollars.

If you're considering whether to get an oil tank sweep, remember this: when you decide to sell your home in the future, potential buyers may request one. Taking care of it now can save you stress and help you avoid surprises later. Over the past 30 years oil tank sweeps, oil tank scans, and/or oil tank inspections have become a common part of the home-buying process.

Why perform an oil tank sweep?

Oil tanks belong to the property and if you buy a home with an oil tank you purchased all the costs associated with the oil tank, including oil tank removal, soil testing, and the most expensive part soil remediation (if required). 

Oil heat was popular in the Northeastern United States from the 1930s to the mid-1980s, this time frame encompasses a large part of the homes in the Northeast, meaning chances are the home you are looking to purchase utilized oil heat in the past.  Also, homes built before 1930, most likely had oil heat. since coal was phased out as soon as a homeowner had a chance to switch, since coal required physical feeding of the furnace several times a day during the heating season.

 What percentage of tank sweeps find prior oil heat?

With over 30 years of experience with oil tanks, we have crunched the numbers and found an average of about 75% of the oil tank sweeps find evidence of prior oil heat.  That number should not be that surprising since natural gas really only became popular in the 1970s.

Who pays for the oil tank sweep?

Buyers typically pay for the oil tank sweep as it is part of their due diligence.  Due diligence is what a reasonable person would do to investigate a property for problems prior to ownership.

Do property owners ever do oil tank sweeps?

Most property owners do not perform oil tank sweeps as they do not want to find an oil tank.

Oil Tank scan with Ground Penetrating Radar (GPR) or metal detector?

You should use both GPR and a metal detector to be thorough when performing a tank scan or oil tank sweep. Rely on GPR the most as it is what commercial sites use, metal detectors are more to prove that the object found by GPR is metallic.  Remember, the best equipment is the most expensive, an $800.00 metal detector on Amazon.com should not be relied upon.

Metal detectors beep if they find iron sand (a real thing), buried pipes, get too close to a metal fence or a structure with metal (yes homes have metal) or simply encounter buried metallic trash.   GPR uses a screen so the geophysical technician can see the graphical image detected by the GPR antenna.     Larger signals are tanks, smaller signals are usually pipes.

Should the oil tank scan company perform removals?

 

Yes, the oil tank scan company should be responsible for removing oil tanks. This is because their technicians are well-versed in identifying underground and aboveground oil tanks, as well as recognizing other potential structures. Curren has been contacted by many clients who have hired oil tank scan companies and discovered anomalies or tank-like structures on their properties. These clients often request either a Ground Penetrating Radar (GPR) scan to further investigate or an immediate tank removal. The cost for tank removal typically exceeds $1,000, and in many cases, no actual tank is found. Instead, there may be large rocks, sewer lines, clay deposits, iron sand, or other materials that resemble a tank structure.

    

Oil tank sweeps are not required by law but are 100% prudent when buying a home built before 2000.  Oil tanks are a Recognized Environmental Condition (REC) and the liability or responsibility of cleaning up a tank leak occurs to the property owner.    An oil tank sweep is the best way to locate buried oil tanks.  Leaking oil tanks (Rust Never Sleeps) and improperly abandoned underground oil tanks are a financial liability and hazard.

Consider that a small oil tank leak can cost $10,000 and some soil remediations can exceed $100,000, oil tanks are a huge liability.

The soil remediation to the left cost $45,000, which included engineering and structural support of the building, restoration of concrete and stairs, and HVAC relocation. 

The oil tank was found buried and hidden under the stairs before purchase.  The buyer dodged a bullet on this one

An oil tank sweep is meant to protect a buyer from purchasing a property with an undisclosed oil tank that can leak and cost tens of thousands of dollars to remediate.   Now the hard part is getting a quality oil tank sweep.

The term oil tank sweep is like saying "I'll have a steak", there is a broad range of types & quality.     While price does not always denote quality, "You get what you pay for" rings true regarding oil tank sweep.

Oil tanks were installed in no standard fashion, size, or location on a property because they were installed by fuel oil dealers, plumbers, builders, and excavation contractors.    Over 30 years of removing oil tanks has allowed Curren Environmental to see this firsthand.   When you do an oil tank sweep you want the company to have years of experience removing oil tanks, and be currently licensed to remove oil tanks, because when you find an oil tank, people want a cost to remove it.

There is no licensing for individuals who perform oil tank sweeps and like hobbyist's treasurer hunters, most people incorrectly rely on a $1,000 metal detector to sweep for an oil tank.     You will find this approach when you get a cost under $300 for an oil tank sweep.   Metal detectors will pick up all metal and cannot differentiate between an oil tank and geology or surface metal like a fence of buried pipes.   

The below snip is from a metal detector scan,  this is the whole report, one page.  I have no idea how the house is heated, oil or gas, or if any evidence of an old buried tank was found inside the house because they do not reference if they went inside the house.

 

 

 

 

The photo to the left is the house where this oil tank sweep was completed.  The photo shows their metal detector on top of where they believe a tank is located, in the rear of the house.

 

This photo shows the view of the front of the house.  In the photo, two pipes are protruding from the side of the house.  These are pipes for a basement oil tank, although the one-page report doesn't state that the home is on oil heat but does state "No vent pipes, fill pipes or fuel distribution lines were found during the inspection."  A qualified company would note the basement oil tank which based on the age of the home increases the probability of a 2nd tank, which could be the metal object they found.  But follow me here the oil tank is in the rear of the house, and the existing tank is in front of the house.  That is weird because the oil tank wants to be near the heater and the more likely location for a buried oil tank would be near the basement oil tank but obviously on the outside of the house.  Turns out there was no buried tank just metallic soil.

The takeaway here is Ground Penetrating Radar (GPR) was not used to scan for an oil tank.  GPR is a commercial application, meaning it is used for commercial and more complex sites.   GPR provides a visual image of what is in the ground, cost is more in the $400, range but you get tens of thousands of dollars of sophisticated equipment that allows you to professionally scan a property.

   

Being licensed to remove oil tanks also helps.  It gives hands-on training to the technicians who scan for oil tanks.  Meaning after you find an undisclosed oil tank you can be involved with the removal of the oil tank so you verify what you found. 

         

 

Does the owner of the property have to be made aware tanks weep is being performed?

A tank sweep is a form of due diligence, like a home inspection, every seller has to allow inspections, although they don’t have to agree to fix anything.  Every seller should be aware that the buyer is paying for these inspections, so they are aware these items are a concern.  Nobody likes to be surprised by problems, which inspections by nature are looking for.

The owner should be aware we are doing an inspection specific to oil tanks because if we find a tank we want it removed and I was told they have no knowledge of any oil heat.

Do you need to go inside the building during a tank sweep?

100% you have to go inside the building and inspect for evidence of prior oil heat.  Anyone not going inside is doing an incomplete inspection. To provide a thorough tank scan, Curren needs access to the basement heater room during the scan and no cars in the driveway.

An oil burner switch and an oil burner fuse inside the door are both clues that are indicative of oil heat.  Curren also sees "cut outs" in the flooring of the basement, or lines sticking out of the flooring, both are clues that an oil tank was present on the property at some point in time. 
 

      

Speaking of visual assessment as part of a tank sweep, one of the photos below suggests an oil tank the other is 100% not an oil tank.  The trained technician knows the difference.

     

 

What happens if you find an oil tank during a tank sweep?

When a tank is found the owner/seller must be informed of the tank and that it needs to be removed and tested to verify no leaks.  But it goes deeper than that, a cascading series of events occurs.

1. The settlement will need to be pushed back typically a month or more as you need time to get permits, remove the tank and get soil sample results. Example: We just had a tank located and removed prior to the settlement they pushed back settlement twenty days on day fourteen we removed the tank and it leaked, now the leak is reportable to the state environmental agency, and you will have to do reporting to the government, which takes time.   As we waited a week for the test results, the settlement was not moved back any further, three days before settlement we get all the test results 100% failure and soil remediation required. The Realtor, mortgage company, and buyer were like deer in the headlights as there was no backup plan.

2. Find a tank, the seller must address the tank for the buyer or cancel the contract and disclose the tank to all FUTURE BUYERS, meaning updating the Disclosure Statement.  A Realtor must update the listing referencing the tank. Example: had one where we found a tank, the seller canceled the contract, and got a new buyer but NEVER DISCLOSED the tank.   Buyer found tank AFTER PURCHASE.   Man, the number of attorneys and people getting sued was large and the buyer walked away winning.

3. Find a tank, and see if the seller will take care of it because as you have just read, they need to do the right thing.  Buyer can push back settlement until at least the tank is removed and soil sample results are returned, and it can be determined if remediation is or is not required. Example: Had this situation occur, but the tank was found under a deck, buyers paid for soil testing where we could test, and contamination was found.   We found cancer, but the extent was not known because the deck prohibited access to drill test borings.   The buyer and seller came to some financial agreement on the purchase and the buyer got monies back or off the purchase price.   We remove the tank and performed a remediation, but the contamination was extensive, and the buyer needs more money to clean up the leak but the seller is saying they agreed on an amount and no more funds will be provided.

 

 

What  happens when a home inspection finds a possible underground oil tank?

A common request our office receives regarding a tank sweeps.

"Hello, I'm selling my home and we suspect that the buyer did a tank sweep with a metal detector vs GPR. They supposedly think they found a tank on the property. We do not see any evidence of a tank, nor was one disclosed by the previous owner (who bought the home in the 70s, house is 80 years old). Is it possible that this 'tank' is just a gutter drain pipe, part of our sprinkler system and/or rubble backfill such as a chunk of concrete sidewalk with rebar or metal containing soil? If so, would a GPR scan be conclusive? Thanks."

This is a common situation we get from property owners who are told they have a buried oil tank.   The owner has the question regarding if the meta detector is reliable.    Here are some common talking points...

1. The property owner is unclear how the suspect tank was found.  Was it found with a Metal detector, or  Ground Penetrating Radar or both? (both GPR and a metal detector would be best) The solution would be having the owner receive a copy of the Tank Sweep Report so they would have a baseline regarding what they found and where. Yes, every professional service should come with a report, no report, then question how professional the service was.
2. The property is over 70 years old, so while the owner has no knowledge that there was an oil tank, they also have no documentation that there was not an oil tank. A 70 year old property most likely had oil heat at one point in time as oil was very popular in the past and other fuel sources such as natural gas was not commonly available or financially appealing until the 1970's.
3. The tank scan found a buried object, presumably metal. If only a metal detector was utilized, you can't say 100% if the metal found is a tank as metal detectors detect metal and properties have all sort of buried metal. Metal can be in the soil naturally, you could have buried debris, buried metal pipes or surface metal (like a fence) that distracted the metal detector and have a false buried metallic signature reading. Happens all the time. A metal detector on a sandy beach is great it will find buried metal, likely a bottle cap, but people hope for coins or expensive jewelry. People paying a couple hundred dollars for someone to use an $800 metal detector to find a tank are also helpful.

The photo below was where a metal detector thought there was a tank.  There was no tank, just soils with a metallic signature.

The guy in shorts, is using a $900.00 metal detector and found a suspect tank in the front yard.

When you scan for a tank, the more expensive the equipment the better.   GPR (Ground Penetrating Radar) costs tens of thousands of dollars because it has the technology to do the job.

 Effective Oil Tank Scan or Oil Tank Sweeps like on commercial sites would use GPR as it will                            provide a signal (image) of buried objects.

The signal above shows the underground oil tank. 

Purchasers of commercial properties are more aware of the liability associated with leaking USTs (Hundreds of thousands of dollars) compared to a residential home buyers (Homeowners think a few thousand dollars is a lot.) So on the commercial side of real estate tank sweeps are completed with GPR, not metal detectors. Most environmental consultants that perform tanks weeps will use GPR and discount the cost for residential sites. Nobody wants to see someone buy a house and find a $50,0000 cleanup is required.

What if a buyer finds a suspect tank?

This is a really hard question because it relies so much on the quality of the tank sweep.    If they used GPR, if the property is likely to have had an oil tank (older the home, the more likely) and if the buried anomaly has the signature of a tank.  Well then you have to excavate and confirm that object is an oil tank.

Who pays for the oil tank removal?

Owner will pay 98% of the time as finding a hidden oil tank is a defect that needs to be addressed.

Do they have buried oil tanks at the beach (shore)?

If the home wanted heat, then yes homes along the coast and on islands had buried oil tanks.  Oil was king up until the late 1970's in New Jersey.  The photo below is of a home we scanned on a barrier island.  Many older beach houses eventually converted to natural gas, as gas could also  fuel the stove, dryer,  hot water heater etc.   After conversion to gas, it was not uncommon that the tank was just left in the ground.  So short answer beach houses had oil tanks.

What if a suspect tank is found and we don't believe its a tank?

Short answer prove your opinion right and dig it up and verify its not a tank.

What is the best tank sweep?

Using Ground Penetrating Radar is the best technology for finding buried tanks at properties, period.  Can you use a metal detector to verify a GPR signal that identified a tank?  Sure, always verify the object is metal.  GPR can't penetrate metal so when a GPR sweep pings a tank, it means the radar can't penetrate the object (likely a metal tank) but there are buried concrete tanks.  Metal detectors can verify an object is metal, but a metal detector  should not be used to be your sole technology