Source: http://www.inforum.com, November 3, 2016
By: Tu-Uyen Tran
When construction workers were digging up a downtown parking lot on Roberts Street a few months ago, they found a couple of underground storage tanks that didn’t appear on any of their maps.
One in the vicinity of the Carnegie Library, which stood at the site from 1903 to 1970, seemed to be really old because it was really deep.
“When we excavated we ended up finding two different floor slabs over in that area and this tank below both of the floor slabs,” said Nick Berglund, construction services manager with the consulting firm NTI. “I believe they built over it twice previously.”
Workers ultimately removed both tanks, which may have contained some sort of fuel, and the contaminated soil surrounding them.
Finding a surprise tank is an oddly common occurrence in construction sites in older parts of the city, especially downtown, said Grant Larson, director of environmental health at Fargo Cass Public Health. Governments didn’t track the location of underground tanks in the past, and many kinds of tanks aren’t regulated, including heating-oil tanks for private use.
More forgotten heating-oil tanks are buried under Fargo’s booming downtown than other parts of the city because it’s the oldest, and oil was the most common form of heating before natural gas, Larson said.
But that means there’s another added cost to building downtown and in other older parts of the city where streets and sewers already exist, which Fargo city officials encourage as a more efficient form of development. Experts say the amount of cost it adds to a project varies, depending on how much cleanup is required.

Regulation gaps

The state of North Dakota began regulating underground storage tanks in 1986, when owners of tanks that hadn’t been taken out of service by 1974 had to register them with the Department of Health. There are 323 registered tanks in Fargo, most of which belong to gas stations. Of these registered tanks, 124 had reported some leak in the past though all have been cleaned up or is in the process of being cleaned up.
Registration is required for tanks containing petroleum products for sale, agricultural chemicals and other regulated substances such as industrial waste. Excluded are septic tanks and fuel tanks for on-site use, such as heating oil used by office buildings and private homes.
Tanks that aren’t regulated and old tanks that were not in use as of 1973 may not appear on maps and could be a surprise to new owners, who would be responsible for cleaning up any leaks.
Berglund, whose firm assesses the risk of contamination for developers, said unregistered tanks can’t really be assessed.
“We don’t know what we’re going to find where, at what depth, or anything, contents, all that stuff,” he said.
Their potential stealthiness isn’t the only problem with older tanks. They weren’t as well-designed as today’s tanks. According to the U.S. Environmental Protection Agency, most tanks made before the mid-1980s were made of bare steel and “likely to corrode over time,” leading to leaks. The main risk is to groundwater, but oil leaks can increase fire risks and, for homes with drain fields, the vapors can back up into the home.
Reuben Panchol, a scientist with the North Dakota Department of Health, said most tanks today are double-walled with one wall or both made of fiberglass to resist corrosion. Steel single-wall tanks are still allowed but usually must have some other form of corrosion control.

Tank removal

At the Roberts Street parking lot, where Fargo development firm Kilbourne Group is erecting a new parking ramp and mixed-use building, the two tanks contained mostly water contaminated with whatever had been in them, according to Berglund.
He said the tanks could’ve stored heating oil for the library or fuel for the adjacent auto service shop. The old fire-insurance maps he used aren’t precise.
A vacuum truck removed the water and took it to the city’s sewage plant for treatment, Berglund said. The tanks were then removed, as well as the soil around them. To find out if they’ve removed enough soil, workers used a gas detector and sometimes their noses, if there is too much gas vapor in the air for the detector to zero in on the source.
The work is overseen by the state Department of Health, which has authority over underground tanks. County public health provides guidance.
Contaminated soil from the Roberts ramp site were trucked to the Polk County (Minn.) landfill where it goes through a process called “land farming,” Berglund said. That’s where the soil is spread out in a thin layer and turned occasionally until all the fuel has evaporated.
Berglund said the risk of leakage is relatively low in downtown and other parts of Fargo where there is a lot of clay in the ground. “It’s probably the worst material to work with, to build with. It’s old lake bottom. But it’s great for making levees, and it’s great for containing leaks,” he said.
Construction companies typically charge a few thousand dollars for removing underground tanks, but leaks can cost tens of thousands. The EPA has estimated the cost of cleaning up a leak of a commercial tank at $125,000.

Downtown development

The tanks at the Roberts ramp construction site aren’t the only ones by Kilbourne Group, a downtown-focused company founded and owned by Doug Burgum, the Republican nominee for North Dakota governor in next week’s general election.
Until recently, it has mostly been involved in renovating the interior of downtown buildings, the exception being the 300 Broadway building south of the Fargo Theatre. But, in several recent projects involving excavation, it’s stumbled upon some unmapped underground tanks.
There were the two tanks at the Roberts ramp.
Before that there was a tank at the Ball Building at 63 Fifth St. N., the former home of the Ball Auto garage and later Doyle Checker Cab. After Kilbourne demolished the building, excavation uncovered some sort of fuel tank.
Panchol said it was too difficult to remove, so the owner filled it with inert material and left it in place, a standard procedure for inactive tanks. He said it’s now registered with the state.
Under downtown, there are dozens of other inactive tanks registered with the Department of Health. The Forum building has one, so does the Radisson Hotel, the old Great Northern train station, the post office, the federal courthouse and the fire station, among others.
Larson said many old storage tanks were left in place when they were no longer useful. Many of the tanks under commercial buildings were big and bulky and taking them out could undermine the integrity of the building, he said. For homeowners with fuel-oil tanks in the backyard, he said, the choice to not remove them was about saving money.
In the spring, when Kilbourne plans to begin building the Block 9 highrise downtown near U.S. Bank, it will probably encounter another unregistered tank. The bank had used the tank to store heating oil until it converted to natural gas, she said.
“I think a lot folks are unaware of the challenges of infill development,” Kilbourne spokeswoman Adrienne Olson said, meaning developing properties in established parts of town instead of on surrounding farmland. “We certainly believe it is work worth doing.”