CHICAGO (CBS) — It cost almost twice as much to clean up Grant Park after Lollapalooza this year than it did last year, thanks to a rainy August and the extra day of music at the annual festival.

The Chicago Park District said it cost $453,000 to get Grant Park back into shape after Lollapalooza at the end of July, compared to about $236,000 last year.

READ MORE: Chicago Police Union President Urges Aldermen To Repeal Mayor's Vaccine Mandate For City Workers, Judge Denies Request To Extend Gag Order

The 91 percent increase in the cost for restoring the fields at Grant Park was due to larger crowds, because Lollapalloza was expanded from three days to four to celebrate its 25th anniversary.

“There were 400,000 people versus 300,000 people last year,” said Grant Park Conservancy president Bob O’Neill.

READ MORE: Chicago Weather: Most Locations To Remain Dry Overnight

In addition, heavy August rains made it re-seeding and re-sodding the fields more difficult.

“Grass seed washes away. It’s also hard; the soil, if it’s super-saturated or soggy, is a lot more difficult to work and to grade and to get into shape and level and so forth,” O’Neill said.

The good news is Lollapalooza organizers, not taxpayers, pick up the tab for repairing Grant Park’s fields after Lollapalooza each year.

MORE NEWS: Illinois State University Student Jelani Day's Death Ruled A Drowning

“We’re very dependent on Lollapalooza now – Grant Park is – in terms of improvement, and one of the reasons it’s so beautiful now more than ever is because of Lollapalooza,” O’Neill said.