FAIRFIELD -- Partnership HealthPlan of California expanded its reach into Marin and Mendocino counties, giving the nonprofit managed Medi-Cal plan some 38,000 additional Medi-Cal enrollees.

"Our membership has grown by more than a third, so it's really quite a significant increase for us," spokesman Dave McCallum said.

With the addition of those two counties, effective July 1, Fairfield-based Partnership HealthPlan is now in six counties: Solano, where it was founded in 1994, as well as Sonoma, Napa and Yolo.

The quasipublic agency administers benefits for roughly 200,000 Med-Cal and Medicaid patients across its six-county network.

In Marin and Mendocino counties, the partnership's primary care provider network will include all hospitals and federally qualified health centers; most medical groups, including Prima Medical Group; Tamalpais Pediatrics; Sutter Pacific Medical Foundation; Kaiser Permanente and some private practices.

Mr. McCallum said Partnership HealthPlan's expansion will enable more physicians in Marin and Mendocino counties to accept more Medi-Cal patients because the organization will offer providers a better reimbursement rate than what the state can offer. Partnership's reimbursement to physicians includes a fee-for-service payment, capitation and additional incentives for taking on Medi-Cal recipients, versus a predetermined, non-negotiable state reimbursement.

Partnership HealthPlan also contracts with a number of specialists in throughout the Bay Area, who are paid an "enhanced rate" to encourage access. 

"This is a more streamlined process," of Medi-Cal, Mr. McCallum said. "It increases access by bringing more physicians into the Medi-Cal system."

According to the partnership's 2009--10 annual report, the health plan increased its net assets by $31.5 million in fiscal 2010, compared with an increase of $17.1 million in fiscal 2009.

Partnership HealthPlan is one of six not-for-profit county-organized health systems operating in the state.

Earlier this year, Partnership purchased the building  on Business Center Drive that will soon be vacated by CoPart, an online vehicle auctioneer that is relocating corporate headquarters to Dallas. Partnership paid $16.5 million for the building and will lease it back to CoPart until December 2012, when it will relocate to accommodate its growth.