ARDEN HILLS — Development of the Twin Cities Army Ammunition Plant site has reached a critical juncture.

Planners are preparing for the next phase of work at the sprawling Arden Hills site. A state bonding bill includes $30 million for road work necessary to propel development of the property. It will pay for upgrades to two arterial roadways officials describe as crucial to the successful development of the 427-acre site in Arden Hills.

“We’re looking to bring in up to 1,700 housing units and 4,000 jobs. … We need those roads to be able to handle that kind of capacity,” said Jim McDonough, chairman of the Ramsey County Board of Commissioners. “This is a critical step for us as we move forward with Arden Hills to fully develop that site and maximize its potential.”

Ramsey County bought the heavily contaminated property for $28 million in 2012. The plan is to develop up to 1,700 housing units on 168 acres of the parcel, 2 million square feet of office space on 156 acres, 300,000 square feet of retail space on 18 acres and 53 acres of open space.

Employment at the small arms ammunition plant was at its peak in 1943 when about 26,000 people worked there. More than half were women.