Beneath the grounds of what once was the Amoco oil refinery lurk millions of gallons of groundwater contaminated by nearly a century of oil-refining activity.

BP, the company that inherited the property from Amoco, must rid the grounds of as much of this contaminated water as possible if it is to fulfill its end of the clean-up agreement the company made with the city of Casper and the state of Wyoming.

To accomplish this goal, BP has installed on the grounds of the old refinery a $15 million water-treatment facility designed to cleanse water polluted by crude oil, hydrocarbons and other contaminates like iron and benzene.

The facility functions around the clock and currently cleanses about 500 gallons of water per minute, 30,000 gallons per hour, 720,000 gallons per day, and 262.8 million gallons a year, BP spokesman Bill Stephens said.

Translated into everyday terms, BP's treatment facility processes as much fluid in a year as is contained in 584 million six-packs of 12-oz. cans of Coke or beer.

By the time the once-polluted groundwater passes through the facility, it is clean enough to meet the Department of Environmental Quality's standards for aquatic life, fisheries, and drinking water.

The process

The groundwater cleansing process begins when both water and oil are extracted by the 20 or so recovery wells dug on the refinery site, Stephens said.

The recovery wells have dual pumps; one that reaches down about 26 feet to extract water and another that reaches down about 23 feet to extract the oil that floats atop the water table, Terry Tebben of BP said.

After the oil is extracted by the shallower pumps, it is piped into large tanks on the north side of the Platte River Commons - the new name of the refinery property.

The oil is of high enough quality that it can be taken directly from these tanks to the Little America refinery in Evansville, where it is turned into gasoline and other petroleum products, Stephens said.

The water pulled out of the ground by the deeper pumps is piped to a oil-water separator located in a building also on the north side of the property.

In the separator, the oil so long trapped in the water is removed.

Since the new separator became operational in April, it has processed on average 450 gallons of water every minute of every day. Out of this water it has extracted only about 1,200 gallons of oil.

The relatively little amount of water extracted by the separator is due to the fact that the vast majority of the oil under the refinery site sits above the water and is able to be extracted separately from the water.

The new separator is a vast improvement over the old separator BP had used on the site, Stephens said. The old machine was open to the air and vapors released by the separation process would foul the air near the old refinery.

The new separator, however, is closed to the air and no vapors are released into the atmosphere when it is in use. One can stand in the same room as this machine while it is working and not detect any hydrocarbon smell.

Even with the oil separated from it, the groundwater is still contaminated with hydrocarbons and other pollutants like iron and benzene.

To rid these contaminants, the water is pumped from the separator to an air stripper in a building buried in a hillside next to the 16th tee of the new Three Crowns Golf Course.

From the outside, the buried building resembles a kind of high-tech Hobbit hole and a visitor to the grounds may mistake its doors as leading to restrooms.

Inside the camouflaged building, the air stripper bombards the groundwater with jets of air that blast out the residual hydrocarbon vapor.

The new hidden air stripper is a colossal aesthetic improvement over the air stripper BP used previously, which consisted of two industrial towers located directly across the North Platte from the western end of Amoco Park, Stephens said.

The vapor removed from the water by the air stripper is piped over to a biofilter buried under Three Crowns' driving range. In the biofilter, air and water are added to the vapor, creating an environment conducive to microbes, which break down the hydrocarbon molecules, Stephens said.

Meanwhile, the vapor-free water is piped from the air stripper to an iron sedimentation pond, where ferric material long suspended in the water sinks to the bottom.

The sedimentation pond doubles as a water hazard on the par-3 16th hole of Three Crowns. So when the course opens, misfired Titleists, Pinnacles and Maxflis will join the iron at the bottom of the pond.

After the iron sedimentation process is complete, the water flows down a creek, which also doubles as water hazard, to underground wetlands.

In the man-made wetlands, air is bubbled through the water, microbes eat at the few contaminants left and plants suck up a few more of these nasty vestiges of pollution.

Following the wetland treatment, BP tests the samples of the water to see if it meets with pertinent Department of Environmental Quality specifications.

Thus far, all the water tested after going through the system has met these specifications, Stephens said.

After the water has gone through this whole treatment process, it is now pumped into a holding pond on the property, yet another hazard on Three Crowns, then flushed into the city of Casper's sewer system.

Later this year BP plans to begin pumping the treated water to its Soda Lake facility north of town, Stephens said. BP may also use some of the treated groundwater to irrigate the golf course, he added.

Is it the water clean?

To receive a permit allowing it to pump the treated groundwater to Soda Lake, BP first had to demonstrate that its treatment facility produces water that meets the DEQ's aquatic life specifications, said Todd Parfitt, the DEQ's National Pollutant Discharge Elimination System (NPDS) program manager.

BP has already obtained the permit. And in the company's application, BP showed its treatment facility is up to snuff, Parfitt said.

The permit also allows BP to pump the treated groundwater directly into the North Platte River, where the water must meet the more stringent fishery and drinking water supply standards, Parfitt said.

To meet the DEQ's aquatic life, fishery and drinking water standards, BPO must demonstrate the treated water contains safe levels of toluene, xylene, ethylbenzene, benzene total petroleum hydrocarbons, iron, phenols, PH and total suspended solids, Parfitt said.

According to BP's permit application, the new treatment facility is doing an adequate job of removing these contaminants, he added.

The DEQ has also mandated BP to test the treated water four times a year for 12 other contaminants not normally found in untreated water beneath the refinery, Parfitt said.

The permit to pump the treated water into Soda Lake and the North Platte is good for five years and requires BP to test the treated water frequently and report the results to the DEQ, Parfitt said.

The DEQ will also periodically inspect BP's water treatment facility and will test the water that comes out of it from time to time, he added.

Later this year BP plans to install about 20 more recovery wells around the old Amoco refinery grounds. This will allow the company to double the amount of water it extracts - from 500 to 1,000 gallons per minute - and double the amount of groundwater it treats with its new facility, Stephens said.

In 2007, BP plans to install a new infiltration line that will pump clean water into the subsurface in order to flush out more of the contamination, a process that works a lot like an oilfield water flood, Stephens said.

When the infiltration line is installed, the treatment facilities will clean about 1,500 gallons of water every minute, 90,000 every hour, 2.16 million gallons every day, and 788.4 million gallons every year, Stephens added.

That yearly total is equal to the amount of fluid amount contained in 10.5 billion cans of Fresca.