SAN FRANCISCO  (AP) — Power utility PG&E Corp. on Thursday posted a fourth-quarter loss, weighed down in part by the costs of environmental issues related to historic operations and pipeline-related expenses.

For the three months ended Dec. 31, the San Francisco-based company lost $13 million, or 3 cents per share. That compares with a profit of $83 million, or 20 per share, a year earlier.

Taking out the environmental costs, natural gas matters and other items, earnings were 59 cents per share.

Analysts, on average, forecast slightly higher earnings of 60 cents per share, according to a FactSet poll.

The environmental costs are related to groundwater contamination in Hinkley, Calif., an issue that dates back to operations there in the 1950s and 1960s. The issue was first publicized during a 1996 court case and inspired the movie "Erin Brockovich." During the quarter, about 200 homeowners agreed to sell their homes in Hinkley to PG&E. Earlier in 2012, the company was ordered to provide permanent, in-home source of clean water to residents.

Full-year net income declined 3 percent to $816 million, or $1.92 per share, from $844 million, or $2.10 per share, in 2011.

Adjusted earnings were $3.22 per share.

Annual operating revenue was flat at about $15 billion.

For 2013, PG&E foresees adjusted earnings in a range of $2.55 to $2.75 per share.

Analysts expect earnings of $2.77 per share, on average, with estimates ranging from $2.55 to $2.90 per share.

PG&E said that it plans infrastructure investments of $4.5 billion to $6 billion a year between 2014 and 2016 so that it can maintain safe and reliable electric and gas service. The company said it anticipates needing "substantial amounts of equity" to fund part of the investments.

It expects up to $30 million in costs related to the issues in Hinkley.

PG&E's stock dropped 99 cents, or 2.3 percent, to $42.13 in Thursday morning trading.