A mining business was fined almost $300,000 for improper hazardous waste disposal. A dairy farmer dumped wastewater into a municipal storm sewer. A power plant burned more than 22,000 tons of wood treated with formaldehyde and other resins.

These are some of the 143 violations cited by the Minnesota Pollution Control Agency in the second half of 2012. The number of cited violations doubled from the previous six months.

I looked at the MPCA's enforcement actions for air, water, hazardous waste and other violations. The agency issued nearly $1.3 million in fines and orders for environmental projects, down from $1.4 million in the first half of last year.

Following are the 12 violators that paid more than $10,000 in penalties. All of the businesses consented to the agency's orders. Most were required to take corrective action.

Northshore Mining Co., Silver Bay, fined $292,973 for solid waste/hazardous waste violations

Northshore Mining sprayed 39,200 gallons of a "corrosive hazardous waste leachate" over its Lake County coal-ash landfill to control dust and improperly sent an equal amount to a nearby water-treatment plant, exceeding permitted levels.

It is the fourth time since 2010 that the taconite company has been fined for violating Minnesota pollution laws.

The company failed to immediately report the violations and failed to properly monitor pH levels in the leachate.

Of the total penalty, $50,000 was donated to the Western Lake Superior Sanitary District for renovation of a hazardous-waste collection site.

Minnesota Department of Transportation and Northstar Materials Inc., doing business as Knife River Materials Inc., Bemidji, fined $235,170 for storm-water violations

Northstar was acting as general contractor for the resurfacing of Hwy. 11 near Birchdale and the construction of bridges and culverts near streams, drainage areas and the Rainy River in 2010.

The contractor discharged "excessive amounts of construction-related sediment to surface water," polluting waterways and damaging fish and wildlife habitat.

Acuity Brands Lighting Corp., doing business as Winona Lighting, Winona, fined $99,500 for air quality violations

The company operated as many as five paint spray booths, a sandblasting unit and a degreaser, installed between 1978 and 2000, without proper environmental permits. The company improperly stored and transported hazardous waste.

Bongards' Creameries, Perham, fined $79,069 for water quality violations

The business sprayed wastewater over snow-covered land, allowed excessive buildup of wastewater in treatment ponds and discharged it into Perham's storm sewer system.

Minn-Dak Farmers Cooperative Inc., Wahpeton, N.D., fined $70,000 for water-quality and solid-waste violations

The company allowed polluted water from three of its sugar beet storage facilities in Wilkin County, Minn., to enter the Rabbit River watershed.

The company also burned plastic and other solid waste in violation of state regulations and made "material errors" in reports to the MPCA.

American Crystal Sugar Co., Moorhead, fined $24,943 for air quality violations

Fine particle emissions from kilns at an East Grand Forks processing plant exceeded permitted levels, monitoring equipment was out of service and the facility failed to keep records of some equipment inspection results.

Superior Industries LLC, Morris, fined $20,000 for air quality violations

Hazardous air pollutants, including volatile organic compounds, exceeded permitted levels every month for four years. A sandblasting booth lacked control equipment and "problems existed with spray hood certification and recordkeeping."

Lunda Construction Co., Black River Falls, Wis., fined $17,500 for storm-water violations

While working on two bridges over the Rum River near Princeton, Minn., in 2010, Lunda failed to have adequate erosion-control measures in place. The violations allowed sediment-laden storm water to wash into the river.

Darlow Excavating, McGregor, fined $15,000 for sewage-treatment violations

The company poured untreated sewage into a gravel pit it owns, but exceeded allowed limits by more than 360,000 gallons over three years, creating a threat to groundwater.

Fibrominn, Benson, fined $14,000 for air quality violations

The company, which generates power by burning turkey manure and other biomass, improperly burned at least 22,428 tons of plywood and other treated wood over the course of almost four years. The wood contained resins such as phenol formaldehyde.

Craig Benedix, Mantorville, fined $14,000 for water quality/feedlot violations

Benedix pumped hog manure onto a cornfield that flowed to a grassy waterway and then into the Zumbro River watershed. A complainant said that water in a nearby creek was "discolored, foaming and smelled like manure."

U.S. Postal Service, Eagan, fined $13,000 for air quality violations

Fourteen gas-fired boilers and seven diesel-fueled generators were installed and operated at a Lone Oak Parkway facility as early as 1998 without permits. The USPS also failed to file emissions reports between 1998 and 2007.

Hard Data digs into public records and puts a spotlight on rule breakers in Minnesota. Contact me at jfriedmann@startribune.com.