Pima County is on the verge of finalizing a purchase agreement for a 286-acre parcel in the west-side Painted Hills area.

County officials will ask the Board of Supervisors to approve an agreement to buy the coveted land from the Dallas Police and Fire Pension System for $7.5 million, including a $3 million down payment, according to a county memo.

The board is expected to vote on the measure at its Aug. 18 meeting.

If the purchase is approved, the county will have reached its goal of preserving Painted Hills — which is between West Speedway and Anklam roads, west of Greasewood Park. The county wants to connect the area with Tucson Mountain Park to its west.

The county will use money from a 2004 open-space bond program for the down payment.

Officials would then make five payments of about $1 million, which includes 5.75 percent interest, according to the memo.

The county is hoping to pay the balance of the cost with money allocated for open space from a possible November 2015 bond election.

If that option fails, then the money could come from a special environment fund the county shares with the JW Marriott Starr Pass Resort, funded with sales revenues from the resort.

The approval of the purchase would culminate a pursuit that began in 1997, when the county made the property part of its open-space bond program.

The county was outbid for the property in 2006 when the Dallas pension fund bought it for $27 million.

Officials had another shot at getting the property in 2012, when the city and the pension fund negotiated a land swap involving the downtown Ronstadt Transit Center and Painted Hills.

But the deal collapsed when word leaked about the discussion and transit supporters protested.

The land was originally slated for development.

The most recent appraisal of the land set its value at $8 million to $12 million, officials said.

Once the purchase is approved, it would bring the number of properties acquired by the county under the bond program to 53.

That represents 20 percent of the land identified in the bond ordinance as priorities for conservation, according to the county memo.

Contact reporter Jamar Younger at jyounger@azstarnet.com or 573-4242. On Twitter @JamarYounger