CALGARY, Alberta (Reuters) - Enbridge Inc
has submitted its plan for restarting a pipeline that ruptured
last month and spilled oil into a Michigan river system, but
the timing for turning the valves back on is still not known,
the company said Tuesday.

Enbridge, which ships most of Canada's crude exports to the
United States, filed its plans with an agency of the U.S.
Department of Transportation late Monday as it repaired the
190,000 barrel a day Line 6B pipeline, spokeswoman Gina Jordan
said.

The agency, called the Pipeline and Hazardous Materials
Safety Administration, must sign off on the proposed measures
before the line can resume flowing crude to refineries in
Michigan, Ohio, Pennsylvania and Southern Ontario.

"It's up to PHMSA to review and modify, if required, and
then approve that restart plan," Jordan said.

The July 26 pipeline break near Marshall, Michigan, caused
19,500 barrels (800,000 gallons) of heavy Canadian crude oil
to leak into the Kalamazoo River system, forcing a cleanup
effort that has involved more than 1,000 workers and tens of
thousands of feet of containment and absorbent boom.

It arguably gained increased profile against the backdrop
of the much bigger BP disaster in the Gulf of Mexico.

Line 6B, part of Enbridge's 1.7 million bpd Lakehead
system, runs to Sarnia, Ontario, from Griffith, Indiana.

At least three refineries in the U.S. upper Midwest have
been forced to cut output due to a shortage of supplies since
the pipeline was taken out of service.

Refiners in the Sarnia area have sought alternative crude
sources on other pipelines and made other arrangements to keep
their plants running at normal rates.

The shutdown of the pipeline has added pressure to prices
for Canadian heavy crude, market sources say.

Shares in Enbridge rose 21 Canadian cents to C$51.83 on the
Toronto Stock Exchange. Its U.S. affiliate, Enbridge Energy
Partners, fell 77 cents, or 1 percent, to $56.60 in New
York.

($1=$1.03 Canadian)
(Reporting by Jeffrey Jones; editing by Rob Wilson)