HOOKSETT — A Hooksett sand and gravel company will pay a $60,000 fine and emission fees as part of an agreement with state officials over improper operation of diesel generators, the New Hampshire Attorney General said.

Authorities said Plourde Sand and Gravel Inc. did not obtain proper air emission permits for diesel generators it operated in Hooksett and Allenstown.

The Attorney General’s Office said Plourde has a history of failing to respond to requests for information, failing to keep required records and installing devices prior to obtaining permits.

Authorities said Plourde also violated air pollution control rules while a lawsuit over previous violations was pending.

The diesel generators are used to process sand and gravel; their emissions cause ground-level ozone, also known as smog.

The actual settlement calls for fines of $80,000, but $20,000 is suspended as long as Plourde does not commit any more violations in the next three years. The company must pay all emission fees that are due also.

As part of the settlement, Plourde must retain a qualified professional to assist with submittals of air-related information.