U.S. Sen. Brian Schatz is one of four Democrat senators today calling for an investigation into the planned, periodic shutdown of healthcare.gov, the official federal website established by the Affordable Care Act.

Schatz (D-Hawaii), along with Sens. Elizabeth Warren (D-Mass.), Cory Booker (D-N.J.), and Chris Murphy (D-Conn.) are demanding to know why the Trump administration plans to make the website inaccessible for 12 hours on nearly every Sunday and on the first night of the 2018 open enrollment period. The open enrollment period is from Nov. 1 to Dec. 15, 2017.

The four senators asked Centers for Medicare and Medicaid Services administrator Seema Verma why and how the scheduled shutdowns were deemed necessary and asked the agency to extend the open enrollment period to Jan. 31. In a second letter, the senators also asked Department of Health and Human Services inspector general Daniel Levinson to investigate the need for and impact of these scheduled shutdowns.

“We are disappointed to learn that CMS has created a new barrier to enrollment,” the senators wrote in their letter to Verma. “This planned downtime will be particularly harmful as this year’s Open Enrollment Period is only 45 days – significantly shorter than previous OEPs, which were at least 90 days. Furthermore, the planned downtime is peculiar given that HealthCare.gov had successfully met its goal of having a system uptime of 99 percent or greater in previous OEPs.”

The senators also allege that the Trump administration has made a number of actions to undermine the ACA, including drastic funding cuts to its advertising and outreach programs.