The three companies responsible for a 2007 oil spill in a residential area in Burnaby, B.C., entered guilty pleas in Vancouver on Monday.

Two contractors and Trans Mountain Pipeline, the company that owns the pipeline, each entered guilty pleas under a 21-count indictment in B.C. Provincial Court.

The charges come under the Environmental Management Act and essentially add up to introducing pollution into the environment.

The Crown is looking for each of the three companies to pay a $1,000 fine and to make a $149,000 contribution to the Habitat Conservation Trust Foundation, which works to protect B.C.'s fish, wildlife and habitats.

Trans Mountain Pipeline will also be asked to contribute $100,000 to an educational and training program.

The sentences are expected to be handed down later this month.

The oil spilled into Burrard Inlet, contaminating the water. Rafal Gerszak/Canadian Press

An excavator working on a sewage line pierced a pipeline in July 2007, releasing more than 250,000 litres of crude oil. About 70,000 litres flowed into Burrard Inlet, sparking a $15-million cleanup.

Crude oil also sprayed 11 houses on Inlet Drive and caused a large evacuation of the area, forcing 250 residents from their homes.

A report released by the Transportation Safety Board of Canada in 2009 concluded a lack of communication was one of the main factors that contributed to the break.

The report said a lack of respect for on-site pre-construction procedures and inadequate communication compromised the safe operation of the pipeline.

The report found the pipeline was not accurately represented on the contractor's design drawings, which were based on a 1957 drawing.