News reports on Dec. 2 said the site had handled more than 700,000 visitors that day.
"The site is now stable and operating at its intended capacity with greatly improved performance," Mr. Zients said in a teleconference with reporters.
The Obama administration has been under fire from both the American public and congressional lawmakers in both parties since HealthCare.gov opened for business two months ago today, as error rates, slow response times, and repeated system outages made it impossible for many new consumers to complete an application for health coverage.
Residents in 36 states are relying on the site as the primary avenue for obtaining subsidized coverage under the Patient Protection and Affordable Care Act, mostly because Republican leaders in much of the country declined to establish state-operated exchanges.
In the report released Dec. 1, HHS noted that for some weeks in October, the site was down 60 percent of the time.
An assessment conducted shortly after Mr. Zients came on board found the root causes of the website's problems were a mix of technical and management challenges that included hundreds of software bugs, inadequate hardware and underlying infrastructure systems, a lack of incident monitoring, slow decision-making and unclear accountability.
"We needed the team to work with the speed and efficiency of a private-sector company," Mr. Zients said.
The progress report recounts that the CMS—with contractor QSSI serving as a general contractor—began to right the ship as tech teams made more than 400 fixes on their so-called punch list, established 24-7 monitoring of the system, and held "war room" meetings twice a day.
"While we strive to innovate and improve our outreach and systems for reaching consumers, we believe we have met the goal of having a system that will work smoothly for the vast majority of users," the report said.
Among the most notable improvements to the site was the installation of new hardware that more than quadrupled throughput for the registration database, which Mr. Zients likened to widening "the system's on-ramp to four lanes instead of two." About 50 fixes were made to the site just last night, some of which Mr. Zients described as "critical" improvements.
The site's increased capacity, however, may not be sufficient to handle the expected increase in demand. Waves of consumers are expected to return to the site because the White House has promised for weeks to have it running smoothly by Nov. 30, and because they'll be trying to sign up in time to be covered at the first of the year. Mr. Zients noted that the site witnessed heavier traffic this weekend than is normal for a weekend.
As a response, CMS will employ what Mr. Zients called a "queuing system"—which he said was not available when the site launched—that allows users to leave their e-mail addresses so the CMS can alert them about a better time to return to the site. When they return, those users will be able to start at the head of the line.
While the CMS welcomes new users to the system, it will also focus on helping those who encountered problems with HealthCare.gov return to the site and complete the process successfully, spokeswoman Julie Bataille said.
Meanwhile, Mr. Zients stressed the capability of general contractor QSSI—part of UnitedHealth Group subsidiary Optum—after reporters questioned how smoothly operations will run after Mr. Zients leaves next month to serve as director of the National Economic Council.
"I am head-down focused on this project 24-7," Mr. Zients said of his work overseeing improvements with HealthCare.gov. "The general contractor and rapid response team has served us well. They have been in seat and will stay in seat."
This report appeared on the website of Modern Healthcare magazine, a Chicago-based sister publication of Tire Business.