SAN PABLO -- Doctors Medical Center looks destined for closure after voters on Tuesday rejected a mail-in parcel tax measure that supporters had said was needed to keep open the area's only public safety-net hospital.

Only 51.93 percent of voters -- about 16,000 residents -- supported the tax, which needed two-thirds approval to pass.

Measure C would have generated an estimated $20 million annually for the hospital, which is hemorrhaging about $1.5 million every month despite cost-cutting and new revenues that have cut the operating deficit in half in recent years. Hospital officials said they would vote to close the hospital if the tax, which required two-thirds approval, failed.

View of Doctors Medical Center in San Pablo, Calif., at dusk on Tuesday, Jan. 21, 2014.  DMC is the only public hospital serving West Contra Costa County
View of Doctors Medical Center in San Pablo, Calif., at dusk on Tuesday, Jan. 21, 2014. DMC is the only public hospital serving West Contra Costa County and faces possible closure due to a $16 million budget deficit this year. More than 40,000 patients visit DMC's emergency room annually. (Ray Chavez/Bay Area New Group) ( RAY CHAVEZ )

Parcel taxes passed in 2004 and 2011 already pump $10.9 million annually into the hospital but have proved insufficient to keep the facility solvent.

The California Nurses Association sent out a statement after the vote was made public, saying that the closure of a hospital that has almost 80 percent of the West Contra Costa region's hospital beds would create a "dire public health crisis."

"As a registered nurse who has worked for many years at Doctors Medical Center, I am intimately familiar with the critical need for a fully operational hospital (in the region)," said registered nurse Seung Choo. "Many neighborhoods in the community we serve border the refineries and people live in close proximity to heavy industries which has caused asthma rates among children to skyrocket.

Choo added that more than 15,000 people sought treatment from hospitals in the region after the August 2012 explosion and fire at the Chevron refinery in Richmond, saying that "the incident was not the first of its kind nor will it likely be the last."

Ballots were mailed to roughly 107,000 registered voters in the West Contra Costa Healthcare District and were due back by Tuesday evening.

The board in January authorized the mail-in ballot election in hopes of averting closure and making the long-struggling hospital more attractive to potential partners. The proposed parcel tax would have been 14 cents per square foot of developed property, or about $210 annually on a 2,000-square-foot house, and would raise about $20 million a year.

The hospital's $143 million operating budget is strained under the weight of its mostly uninsured and underinsured patients. DMC is the leading provider of hospital care to the area's Medicare and Medi-Cal patients, and cuts to Medicare reimbursement rates have exacerbated the fiscal straits, hospital spokeswoman Remy Goldsmith said.

The only other emergency room in West Contra Costa is Kaiser Richmond, which has only 15 emergency beds. DMC has 25.

If DMC closes, the results would be "catastrophic" to the region, according to a 2011 report commissioned by Contra Costa Emergency Medical Services.

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