(Corrects apportionment figures in paragraphs 8-9)

CALGARY, Alberta (Reuters) - Enbridge Inc
tested the integrity of a pipeline it repaired after a rupture
spilled heavy crude into a Michigan river system, and
regulators will use the results to determine if it is ready to
resume deliveries, a spokeswoman said Monday.

The pressure validation test involves running water through
the segment of Line 6B that broke last month near Marshall,
Michigan, using a higher pressure than employed for normal oil
shipments, spokeswoman Jennifer Varey said.

"The pressure validation test is under way today," she
said.

Enbridge executives have said the test is likely to last
about eight hours.

The company is waiting for the U.S. Department of
Transportation's Pipeline and Hazardous Materials Safety
Administration to rule on its plan to restart the 190,000
barrel a day pipeline.

The line serves refineries in the U.S. upper Midwest and
southern Ontario that, together, process more than 700,000
barrels a day. It is part an Enbridge pipeline network, which
moves the lion's share of Canada's oil exports to the United
States.

The refineries have had to secure supplies via other
pipelines, although Enbridge has rationed space on some of its
other conduits in the region as shippers scrambled to reroute
volumes.

On Monday, it limited volumes on the 193,000 barrel a day
Spearhead Pipeline, which extends to the major oil storage hub
of Cushing, Oklahoma, from Flanagan, Illinois, to 20.45 percent
of its shippers' September nominations.

It also cut nominated volumes on its Ozark pipeline, part
of its 231,000 bpd Midcontinent system, to 12.77 percent. The
Ozark line runs to Wood River, Illinois, from Cushing.

Last week it said it was rationing space, a practice called
apportionment, on two others -- Line 5 and Line 61, also called
Southern Access -- to help deal with the situation.

At least three refineries in Ohio and Pennsylvania have
reduced output as a result of the July 26 pipeline break, which
spilled 19,500 barrels of oil into the Kalamazoo River system,
and price discounts for Canadian heavy crude oil.

Enbridge shares fell 12 Canadian cents to C$52.91 on the
Toronto Stock Exchange. Its U.S. affiliate, Enbridge Energy
Partners , lost 90 cents, or 1.6 percent, to close at
$53.70 in New York.
($1=$1.06 Canadian)
(Reporting by Jeffrey Jones; editing by Janet Guttsman)