After having been home to a succession of chemical manufacturing plants from the 1860s onward, cleaning up the 33-acre property on the Mystic River in Massachusetts, abandoned for decades due to the extent of contamination, has reportedly cost Wynn Resorts Ltd  (NASDAQ:WYNN) two times the amount originally expected.

The Boston Globe newspaper reports that after a year and a half of work and removing nearly a million tons of soil, the Las Vegas-based casino-hotel company announced Wednesday that it has concluded the cleanup of what was a product of significant industrial use and deficiency of environmental protection at the site of its $2.5 billion recently renamed Encore Boston Harbor.

Wynn Resorts reportedly said in a statement that the original $30 million estimate for the cleanup ended up costing the company $68 million.

According to the news agency, the 18 months of work involved hauling away huge volumes (840,000 tons) of contaminated soil and removing pollutants beneath the water by dredging 41,000 tons of sediment. Thirty-thousand tons of clean sand capped the river bed and 24,000 square feet of living shoreline was planted by Wynn Resorts “to bring the site to its original condition, facilitate the natural cleanup of the Mystic River, and support the return of native fish and wildlife to the area,” the company said, according to The Boston Globe.

Wynn Resorts’ plan to landscape the 6-acre harbor walk park located in front of Encore Boston Harbor will reportedly see it spend an additional $14 million.

The company said that in addition to the significant rise in cleanup expenses, an increase to the size of the ballroom and adding more restaurants has also reportedly contributed to the overall cost of the venture, which has spiked from $2.4 billion to $2.5 billion, according to the news agency.

“You can’t put a price tag on turning back the clock and unlocking a spectacular waterfront park that will bring beauty and enjoyment for generations to come,” said Encore Boston Harbor President Robert DeSalvio. “At every point of our constantly evolving cleanup process, when a decision needed to be made, we went with the option that delivered the best quality and most beautiful outcome.”

Encore Boston Harbor is slated to open in June next year.