A man accused of using the cover of the Plumas National Forest to grow more than 3,700 marijuana plants changed his plea to guilty at a hearing Wednesday, according to court documents.

Alejandro Soto-Silva, 22, a man residing in the country illegally, was charged with conspiracy to manufacture marijuana, manufacture of marijuana, and depredation of public lands and resources, according to court documents.

Soto-Silva was arrested in July 2014 after U.S. Forest Service agents found a massive marijuana grow operation containing 3,724 plants near the Soda Creek drainage area of the national park.

“Law enforcement observed irrigation piping running from a water source to man-made reservoirs, used to water thousands of marijuana plants under cultivation,” authorities said in a statement.

Authorities told the Reno Gazette-Journal that the damage to the federal park is estimated to have been $9,500.

The charge of depredation of public land and resources carries its own maximum penalty of 10 years in prison and a $250,000 fine.

Sentencing has been set for April 15. Soto-Silva faces up to 20 years in prison, a $1 million fine, and deportation to Mexico.