The U.S. Fish and Wildlife Service (USFWS) will need even more time to revise its Endangered Species Act (ESA) review of the Mountain Valley Pipeline (MVP), according to a FERC filing.

In a letter dated Friday, USFWS officials told the Federal Energy Regulatory Commission they will need another 45 days to complete their consultation on MVP under Section 7 of the ESA.

Last year, the USFWS reopened its review of the 2 Bcf/d, 300-mile MVP project on FERC’s request. That move followed a legal challenge to MVP’s Biological Opinion and Incidental Take Statement, necessary components of the pipeline’s FERC certificate that USFWS prepared under the ESA.

Days after environmental groups asked the U.S. Court of Appeals for the Fourth Circuit to look at the USFWS documents, MVP’s developers voluntarily halted construction in some areas. The Fourth Circuit still opted to stay the USFWS approvals.

The USFWS already had to extend the original 90-day consultation period — set to expire in December — by 60 days, moving the deadline to this week. That extra time proved inadequate to complete the required review, officials told FERC.

“The Service and the project applicant have made considerable progress but estimate than additional 45 days are needed to complete the consultation,” the USFWS officials wrote. “The additional time is needed primarily to allow for the completion of an updated technical analysis of project-related sedimentation, which will facilitate the Service’s evaluation of potential effects on threatened or endangered aquatic species.”

Project opponents have accused the USFWS of failing to protect the endangered Roanoke logperch in its original review of MVP’s plans. They have also claimed that the agency didn’t set limits for the number of threatened or endangered bats that could be harmed or killed by the pipeline’s construction, an argument that caused problems for the similarly routed Atlantic Coast Pipeline.

MVP is a joint venture between EQM Midstream Partners LP, NextEra Capital Holdings Inc., Con Edison Transmission Inc., WGL Midstream and RGC Midstream LLC. MVP received its FERC certificate in late 2017 and started construction soon after. According to the developers, the project was 90% complete as of August.