MARTINEZ -- Construction is scheduled to begin next spring on a regional transit hub near the Interstate 680 and Highway 4 interchange in Pacheco.

The County Connection bus agency, the Contra Costa Transportation Authority and Caltrans are working jointly on a $2.6 million makeover of the old park-and-ride lot on Blum Road. Upgrades include landscaping, a bus transfer facility, bike lockers, lighting and repaving the parking lot.

Funding for the project comes from bridge tolls, a countywide half-cent sales tax and a $4 billion state transportation bond that voters approved in 2006.

County Connection asked Martinez to manage the project after the agency struggled to oversee construction of a transit center at Diablo Valley College in Pleasant Hill. In part, the agency turned to Martinez because the city planned to annex 111 acres of North Pacheco, including the transit hub site. Voters narrowly rejected annexation last month, but Martinez engineering and public works staffers still will perform construction and project management.

The project budget includes $30,000 to cover city staffers' time and $100,000 to move B&D Trailers, a business at 5041 Blum Road. County Connection also is supposed to pay Martinez about $25,000 per year for five years to pick up trash from the parking lot and maintain the lights and other infrastructure.

Although the transit hub has been in the works for about three years, Caltrans must approve the plans by Oct. 1 to avoid spending an estimated $50,000 to redesign the project to comply with new state specifications. Caltrans required that the city approve contracts to manage construction of the transit hub and provide long-term maintenance for the site. Under these agreements, Martinez is responsible for paying all construction and tenant relocation costs associated with the project.

However, City Attorney Jeff Walter is still negotiating with County Connection to transfer the funding and project management responsibility to the city.

"All the ducks are not in line yet; primarily, and in my view, most importantly the financial ducks," Walter told the council last week. "We have some general commitments by CCTA and (County Connection) to pay the city the funds necessary to do this project, but they're not in an agreement. What if the budget is exceeded? We're hoping that (County Connection) will come up with the additional dollars, but we don't know."

To avoid getting stuck with the bills, the council approved the Caltrans contracts with the condition the city will honor them only if it secures the funding from County Connection. According to spokeswoman Mary Burdick, County Connection doesn't have any money dedicated to the transit hub project other than the tax and bond money, so it's unclear how any cost overruns will be paid for.

County Connection buses don't stop at the existing 56-space park-and-ride lot, a carpool pickup spot for commuters headed west to jobs primarily in San Francisco and Oakland. Construction of 12,272 housing units and 6 million square feet of commercial space on the site of the former Concord Naval Weapons eventually may bring more commuters to the area.

"There are very few park-and-ride lots in this central area that have access for bus use, and it's in a prime location at an intersection where there's already construction work being done," Burdick said.

However, County Connection has never done any ridership projections for the project, nor has the agency determined which of its bus routes will stop at the new transit hub, according to Burdick. So far, no other public transit agencies have committed to serving the transit hub, either.

Lisa P. White covers Martinez and Pleasant Hill. Contact her at 925-943-8011. Follow her at Twitter.com/lisa_p_white.