AUGUSTA — Cranes, earth-moving equipment and tons of construction materials are already on the site as a formal groundbreaking takes place Friday for MaineGeneral Medical Center’s new $312 million, 640,000 square-foot regional hospital.

It will be built on a 40-acre site just off Interstate 95 in a rural area of north Augusta, which will ease access for patients who now use downtown hospitals in the capital city and Waterville, about 20 miles away. The new hospital is being funded entirely with private sources, mostly 30-year bonds issued by MaineGeneral.

Funding also includes a $35 million grant from the Harold Alfond Foundation, named for the shoe company founder and philanthropist, which also provided major funding for the 4-year-old Harold Alfond Center for Cancer Care that’s next to the new hospital’s site.

MaineGeneral says the project, due for completion in the summer of 2014, will be a huge economic boost to the region. At the peak of construction, it’s expected to employ 630 workers, bringing $266 million into the state in direct and indirect spending, according to the Maine Development Foundation.

Chuck Hayes, president and chief executive officer of MaineGeneral Medical Center, said it became clear a few years ago that “we had to rethink our model and regionalize our approach, and make it more efficient.”

The new regional medical center will not only improve efficiency in buying and delivering services, but also in attracting physicians, he said.

“We’ve already had significant success in attracting physicians to the area since we announced our plan for a regional hospital,” said Hayes.

Once it’s built, the hospital will have more than 3,800 employees, making MaineGeneral the largest single private employer in the area. With an annual payroll exceeding $136 million, it’s estimated that $29 million will be spent yearly with central Maine businesses.

MaineGeneral will convert its Thayer campus in Waterville from an inpatient facility to an outpatient facility, and it will close both the downtown Augusta location and its Seton campus in Waterville, which currently provides rehabilitation and other services and offices.

MaineGeneral is working with officials in the two cities to find new users for the properties. The Thayer campus will remain open as an outpatient service center.

Each of the new hospital’s 192 rooms will be limited to one patient, which will enhance patient healing by reducing the risk of infection and allow confidential communications with doctors and nurses. The rooms will include pull-out couches so family members can stay overnight. The hospital will have an education center with meeting spaces for up to 300 people, and separate corridors for the public and for patient movement.

Among the other features are three operating rooms that are made to accommodate new technology that may be developed, and seven specialty-sized or general operating rooms. The hospital will have an emergency department built for easier entry and exits and closer to needed services, and an emergency helipad.