Just south of Lehigh Valley Hospital-Muhlenberg's remodeled emergency department — the one LVH spent $7.25 million renovating two years ago — workers are clearing a construction site at the corner of Schoenersville and Jacksonville roads.

There, in a few months, a new facility will be ready to handle even more emergency-care patients. Patient First, a private company that operates urgent care walk-in centers in three states, is planning to open a center on the site in January. Around that time, another one will open in Wilson, a few blocks from Easton Hospital.

They are part of health care's growing physical presence in the Lehigh Valley. Once dominated by a few large hospitals, the Valley now is being served increasingly by retail health clinics, private urgent-care centers in strip malls and business parks, and hospital-based emergency care rooms. It's a change driven in part by business competition and Obamacare, which could open health care doors to more than 1.2 million Pennsylvanians next year.

"Not a day goes by where we don't see something popping up in our area," said John Haney, chief operating officer of St. Luke's Physician Group. "The competition is getting a little tight."

Urgent-care centers alone are growing at a 15 percent annual clip, said Sam Yates, founder of the recently formed Urgent Care Association of Pennsylvania. With millions of newly insured patients on the horizon, he said, walk-in centers are a "growth industry for the foreseeable future."

Some health-care representatives downplayed the impact of the Affordable Care Act on the walk-in care industry. But the growth trend in walk-in centers on the eve of full roll-out of Obamacare, which will add up to 30 million people to the ranks of the insured, is unmistakable.

Patient First, which began 32 years ago in Richmond, Va., plans to add 26 centers in the coming months, an increase of more than 50 percent. MinuteClinic, a retail walk-in site in some CVS stores, has 680 centers and hopes to have 1,500 nationwide by 2015, said Sharon McGraw, a nurse practitioner at a new clinic in Bethlehem. Local hospital networks are opening their own urgent-care centers and offering walk-in care at family health centers, too.

A research brief released in July by the Center for Studying Health System Change said urgent-care centers first developed in the 1980s and were slow to gain patients' acceptance. But as demand for accessible care increased, so did the centers.

Insurance companies also started recognizing relatively recently that walk-in centers could provide care at a lower cost than hospital emergency departments, said Sheila Shingles, practice administrator at the Cedar Crest EmergiCenter on South Cedar Crest Boulevard in Salisbury Township.

"Once the insurance companies saw the money they could save by sending their patients to us, that's when they started covering it," said Shingles, whose husband opened the practice in 1981.

The "explosion" in walk-in care centers is directly linked to new patients receiving coverage through Obamacare, she said.

There now are more than 9,000 urgent-care centers nationwide, the Center for Studying Health System Change said.

Growth is expected to be even greater for retail health clinics set up in pharmacies, according to the management consulting firm Accenture. It said in a recent report that retail clinics will continue growing by 25 percent to 30 percent a year. At that rate, they'll double in number to more than 2,800 by 2015, it said.

Getting a complete picture on walk-in care centers in Pennsylvania is difficult, since the state Department of Health does not regulate or inspect the facilities.

The centers have their own inspections and oversight, and may have accreditation from the American Academy of Urgent Care Medicine. Some, such as MinuteClinic, are accredited by the Joint Commission.

The Convenient Care Association and Urgent Care Association of America also promote standards among their members.

Retail clinics may be staffed with physician assistants or nurse practitioners, who are licensed to diagnose and treat ailments and prescribe medications.

Urgent care centers usually have a doctor on-site. Some, such as the Cedar Crest facility, have several doctors on hand most hours of the day and house family practices and lab facilities.

Industry officials say that the walk-in centers are defined by who uses them. For those with episodic health needs, such as cuts, colds or infections that require immediate attention, retail clinics may be appropriate. Urgent care centers may be able to provide higher levels of service, such as advanced imaging. Patients with serious injuries are likely to be referred to a hospital emergency department.

Walk-in care centers, representatives said, are in the area to increase patient choice, not replace family physicians.