By Jeffrey Jones

CALGARY, Alberta (Reuters) - Enbridge Inc
has cut oil flows by 8 percent on a major pipeline that is an
alternative to the one that ruptured in Michigan last month, an
executive said Monday, as the company waits for regulators
to respond to its reworked plan to restart the downed line.

The cutback on Line 5 to Sarnia, Ontario, from Superior,
Wisconsin, represents as much as 39,200 barrels of oil a day.
Refiners have been relying more heavily on that pipeline as a
crude supply source since the July 26 rupture of Line 6B.

The break near Marshall, Michigan, spilled about 19,500
barrels of heavy Canadian crude into the Kalamazoo River
system. Cleanup efforts involving 1,300 workers continue.

"We reduced capacity of Line 5 by about 8 percent last
week, and that's the only line that we've taken those measures
on in terms of the review that we always do on the various
lines that we have," Steve Wuori, head of Enbridge's liquids
pipelines division, told reporters on a conference call.

"The reduction was voluntary. It wasn't mandated by
anyone."

Line 5 has a capacity of 490,000 barrels a day, compared
with 190,000 for the damaged Line 6B, which runs to Sarnia from
Griffith, Indiana.

Calgary-based Enbridge moves the bulk of Canadian crude
exports to the United States on several pipelines. So far it
has not been forced to ration space on the system, Wuori said.
That measure would reduce deliveries for all its shippers.

However, the company's storage volumes are high, he said.

Refiners in Ohio, Michigan, Pennsylvania and southern
Ontario have been forced to seek alternative crude supplies
since the outage began.

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Factbox on the impact on refiners

Graphic of the pipeline and refiners affected
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Another Enbridge pipeline, Line 9 to Sarnia from Montreal,
has been running at above-normal rates, but it does not carry
the same types of heavy crude as the ones from Western Canada,
Wuori said.

Prices for Western Canadian heavy oil have been pressured
as supplies build up upstream of the line break. Some
refineries in Ohio and Pennsylvania have been forced to cut
production as the summer driving season approaches its end.

On Friday, Enbridge filed a revised plan to restart Line
6B, agreeing to undertake more testing of the conduit's
integrity. The U.S. Department of Transportation's Pipeline and
Hazardous Materials Safety Administration has yet to issue its
response.

"Line 6B remains shut down as directed by PHMSA's July 28
Corrective Action Order and will not be allowed to restart
until the agency is confident Enbridge can address required
safety issues," the agency said in a statement.

Enbridge shares fell 68 Canadian cents to C$50.22 on the
Toronto Stock Exchange Monday, while its U.S. affiliate,
Enbridge Energy Partners, fell 60 cents to $55.33 in
New York.

($1=$1.04 Canadian)
(Editing by Peter Galloway)
(jeff.jones@thomsonreuters.com; +1 403 531 1624; Reuters
Messaging: jeff.jones.reuters.com@reuters.net))