By Barbara Liston

ORLANDO, Fla. (Reuters) - A trust affiliated with billionaire Bill Gates will pay a $30,000 fine over horse manure in a settlement expected to be approved on Thursday by a special magistrate in the affluent south Florida village of Wellington.

But the Microsoft Corp co-founder, ranked as the world's richest person by Forbes magazine, will receive the village's standard 80 percent discount on the fine, which at one point reached $147,000, said code compliance manager Steven Koch.

Gates bought a $9 million estate in 2013 in the name of Mallet Hill Trust in the equestrian community, which is home to the International Polo Club. The trust is affiliated with Gates, Koch said.

His property was cited beginning in January 2014 for placing an old manure bin too close to a canal, and for building a second bin without a permit to replace the old one, Koch said.

With as many as 12,000 horses in residence community-wide during the winter season, and 100,000 tons of manure produced a year, Koch said the community took proper disposal seriously to protect the nearby Everglades National Park and other waterways.

Koch said code violation notices were sent to the address of record, but apparently did not reach the appropriate contact at Gates' trust. Fines began accruing at $250 a day in the summer of 2014, Koch said.

Koch, who was initially unaware of Gates’ affiliation, said the trust responded in late 2014 only after a reporter figured out who owned the property and the violation hit the news.

A representative for the trust did not immediately respond to a request for comment.

The magistrate’s approval of such settlements is routine, said Koch, who added that Gates was unlikely to appear at the hearing.

(Editing by Letitia Stein and Peter Cooney)