Virginia regulators conditionally approved a state water quality permit for the Atlantic Coast Pipeline (ACP) Tuesday, marking another step forward for the controversial 600-mile, 1.5 Bcf/d natural gas pipeline.

But with additional approvals still pending from the Virginia Department of Environmental Quality (DEQ), full construction likely won’t start until next year.

The Virginia State Water Control Board approved the Clean Water Act Section 401 certification for ACP by a 4-3 vote Tuesday, but that certification won’t take effect “until certain studies are completed by the applicant, then reviewed and approved by Virginia DEQ. DEQ will then present those reports to the board,” agency spokesman Bill Hayden told NGI.

The conditional approval threatens to further prolong the review process for a project that was first announced in 2014 and received a certificate from FERC in October.

“No specific timetable was set” for issuing final approval for ACP, “though DEQ already has determined that the required erosion and sediment control plans for the pipeline will not be approved until March or April,” Hayden said.

“The other main reports are on stormwater management and karst terrain. No construction can begin until the erosion and sediment control plans have been approved by DEQ, or later if the board makes that determination.”

The board issued its decision amid vocal protests urging the outright rejection of ACP and the similarly-routed Mountain Valley Pipeline, which the board approved last week.

The conditional 401 certification is “one of the key remaining approvals that we need,” ACP spokesman Aaron Ruby told NGI. “It’s obviously a big step forward for the project.”

Ruby said lead ACP developer Dominion Energy Inc. expects to “begin pre-construction activities by the end of this year” while acknowledging that “we don’t expect to have all the approvals we need to begin full construction until next year.”

ACP would cross mountainous terrain along the Virginia/West Virginia border to make way for Marcellus and Utica shale natural gas delivery to markets in the Southeast and Mid-Atlantic via an interconnect with the Transcontinental Gas Pipe Line (Transco). ACP would then extend south into North Carolina, with a lateral running to southeastern Virginia.

The project is a joint venture of Dominion Energy Inc., Duke Energy, Piedmont Natural Gas and Southern Company Gas.

North Carolina’s Department of Environmental Quality has multiple ACP permit reviews in process, including a 401 water quality certification, an air quality permit, an erosion and sedimentation control permit and a general stormwater permit. The agency has issued multiple requests seeking additional information from the pipeline in recent months as it conducts its reviews.

Last week West Virginia waived its 401 water quality certificate for ACP.

With the Federal Energy Regulatory Commission, along with the U.S. Forest Service, approving the project, the state-level reviews for ACP have taken on more significance for opposition groups, especially with the recent efforts of New York state regulators effectively slowing or stalling projects there.

ACP’s “opponents are not going to rest easy until these pipelines are rejected outright,” said Oil Change International Senior Research Analyst Lorne Stockman following Tuesday’s decision. “…This delay puts serious obstacles before” the developers.

“The Atlantic Coast Pipeline, like the Mountain Valley Pipeline, is a boondoggle that imperils our climate and communities. It must not be built. The Water Board has given itself an important opportunity to complete its work the right way by finalizing a complete rejection of the Atlantic Coast Pipeline and doing the same for Mountain Valley Pipeline as well.”

Opponents seeking to appeal FERC’s ACP certificate may not find much joy in the near-term, as the Commission issued a tolling order Monday giving it more time to decide on rehearing requests filed against the project. FERC’s tolling order could effectively stall eventual legal challenges of ACP, since a final decision on rehearing from FERC is generally necessary before opponents can turn to the courts.

FERC’s use of tolling orders has come under fire from pipeline opponents, with the Commission’s quorumless stretch earlier this year fueling accusations that the practice frustrates due process.

“FERC has once again lived up to its reputation as a rubber stamp for the fossil fuel industry by fast-tracking the fracked gas Atlantic Coast Pipeline while it is still in legal limbo,” said Sierra Club’s Kelly Martin. Project opponents “deserve their day in court, but today’s decision reminds everyone that FERC has an express lane for corporate polluters. Construction of the ACP would severely damage our health, communities, and climate, and not a single foot should be built until all legal challenges are settled.”

Meanwhile, ACP signed project labor agreements last week with four leading construction trade unions to line up the 13,000 workers needed to build the pipeline. According to Dominion, the agreements include commitments to hire at least half of that workforce through local union membership along the project route.

“From day one we’ve committed to building this project to the highest standards of quality and safety,” said Dominion Energy Vice President Leslie Hartz, who heads up engineering and construction. “These organizations represent the most highly-skilled and well-trained professionals in the industry. They have the training, dedication and experience we need, and we’re proud to have them on board for this historic project.”

The agreements are with the Laborers’ International Union of North America (LiUNA), Teamsters National Pipeline (Teamsters), International Union of Operating Engineers (IUOE) and the United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry of the United States (United Association), Dominion said.