The answer below is from the BC Government:

All oil and gas activity, including coalbed gas development, undergoes environmental assessment as regulated by the Oil and Gas Commission (OGC). The OGC requires companies undertake assessments specific to an issue and appropriate to the phase of development.

An environmental assessment performed by the British Columbia Environmental Assessment Office is performed when the coalbed gas project triggers certain requirements under the British Columbia Environmental Assessment Act (EA Act). For example, groundwater extraction and pipeline construction could trigger an environmental assessment if thresholds set out in the EA Act are expected to be exceeded.

The fact of the matter is that the levels that can be expected from BP's development will not exceed those set to trigger an Environmental Assessment.