Howard County has selected a firm to design and build its new $140 million circuit courthouse, but the head of the County Council said she won’t sign off on the deal until more of the contract is hammered out.

Bethesda-based developer Edgemoor- Star America Judicial Partners has been chosen to lead the design, construction and maintenance of the courthouse as part of a public-private partnership that would cost the county more than $300 million over 30 years.

The council must approve the agreement between the firm and the county.

Council chairwoman Mary Kay Sigaty said she’s wary of the deal because of information she said is missing from the contract, including the exact amount for the first annual payment from the county to Edgemoor-Star.

The amount is estimated to be $10 million, but could shift depending on interest rates and inflation. The numbers likely won’t be final until the close of the deal this fall, according to county spokesman Paul Milton.

Sigaty said there are other issues as well, such as how soon after the contract is