MARTINEZ -- Just when it seemed all loose ends had been tied up on a complex agreement allowing for 678 acres of land to be considered for annexation into Antioch, a new hurdle has emerged.

The latest hang-up between Antioch and Contra Costa County officials in the plan for the waterfront land northeast of the city centers on 114 acres owned by Forestar real estate.

The county wants to remain the lead agency in potential development of that property so developers won't have to start from scratch. Antioch tentatively agreed in August to allow the county to keep review and entitlement authority for that area -- part of a tax-sharing agreement for the entire annexation area.

But, two weeks later, the county proposed a three-party development agreement as a way for Antioch to delegate its land use authority.

Having multiple parties involved introduces some legal complications, mainly the city delegating away its "police power" by giving up its land use authority, said Victor Carniglia, a city-hired consultant.

"When you peel back the layers, it appears there are some impediments legally," he said.

County senior administrator Rich Seithel told the Local Agency Formation Commission board Wednesday that the two sides are in discussion to "find the vehicle to make it all work."

City Manager Jim Jakel suggested county staff work as a consultant to the city to process any agreement as "middle ground" since it has that expertise.

County Supervisor Federal Glover of Pittsburg, a formation commission board member, said the legal counsels for both sides need to get together and "figure it out."

It could be weeks, even months, before a tax agreement is hashed out. It would then go before the county Board of Supervisors for consideration. Then the annexation package would go before the formation commission.

Frustrations among fellow board members mounted Wednesday. The commission has chided the city and county several times throughout the annexation process, which started three years ago.

"It just keeps dragging on. I just don't understand it," Commissioner Dwight Meadows said. "Let's get this cloud off the area and move forward."

All other parts of the draft infrastructure plan and tax-sharing agreement approved by Antioch remain the same.

The city and county will contribute $3 million over 10 years to add water, sewer and storm drains to the 103-acre area off Viera Avenue, with Antioch covering the rest with grants and loans. The city estimates it would cost about $10.7 million, and nearly $5 million more in other engineering and contingency costs, to add the infrastructure.

Antioch has also agreed to help the 200 or so residents in the rural area cover the $18,000 to $20,000 connection costs to city water and sewer lines.

The city estimates the area could yield about $900,000 in net tax revenue each year and provide other economic opportunities on the waterfront. Both parties will also set aside $500,000 over the next five years to boost area economic development initiatives.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.