(Adds Sarnia-Lambton Environmental Assessment comment)
CALGARY, Alberta, Aug 16 (Reuters) - Imperial Oil IMO.TO said on Tuesday its Sarnia, Ontario refinery is not the source of an oily sheen observed on the St. Clair River, adding that there are no operational issues at the facility.
Imperial spokeswoman Lisa Schmidt said the sheen on the river was spotted flowing alongside Imperial's operations at 8:30 a.m. Eastern time (1230 GMT) and the company reported it to local authorities.
The source of the sheen is still unknown, but Dean Edwardson, general manager of the Sarnia-Lambton Environmental Association, said there had been very heavy rains in the area that may have washed out sewers.
"We don't see anything on our water monitors downriver, there are no elevated levels of contaminants," Edwardson said. An oily sheen on the river was uncommon, he noted, but did occur from time to time.
Sarnia in southwestern Ontario is one of Canada's largest refining and petrochemical hubs.
A spokeswoman for Royal Dutch Shell RDSa.L , which also runs a refinery in the area, said its operations were normal.