Regulatory and court challenges swirled around the four-state, 1,172-mile Dakota Access LLC oil pipeline project on Thursday, although for the most part construction aimed at completion by year-end continued.

Mounting opposition turned to the Obama administration with 31 protesting groups asking for the president’s intervention, and a lawsuit filed in a DC federal district court by Earthjustice is still pending a ruling on a preliminary injunction.

Echoing shades of the national protest groups that fought the now abandoned Keystone XL oil pipeline from western Canada, 31 environmental groups sent a letter to Obama, seeking to halt construction and repeal U.S. Army Corps of Engineers (USACE) river-crossing permits for the $3.7 billion project linking Bakken crude oil to markets in the East and Gulf coasts.

The battlegrounds have focused on an Iowa regulatory hearing and federal court cases tied to challenges by opponents in North Dakota who have formed a “protest encampment” near parts of the construction, but Thursday the environmental groups, ranging from the Sierra Club to Waterkeeper Alliance, alleged in their letter to the White House that sacred the Standing Rock Sioux Native American Tribe’s ancestral lands and culturally important landscapes are at risk.

In addition, the project, which is fully permitted and several months into its construction in each of the four states it crosses (North and South Dakota, Iowa and Illinois), could affect the Sioux water supply by its proposed crossing under the Missouri River upstream of the tribal water facilities, the opponents contend.

On Thursday, the three-member Iowa Utilities Board (IUB) denied an eleventh-hour request from 14 landowners along the pipeline route to stay construction work on their lands pending a ruling from the courts, but on a 2-1 vote the IUB gave them until 9 a.m. Monday to separately pursue a stay from the courts.

The environmental groups told Obama they support both the tribes and local landowners along the pipeline route, which have raised many belated concerns, despite the fact that the project has been in state and federal permitting processes dating back two years. In November 2014, Strategic Economics Group, a Des Moines, IA-based research firm, published a study concluding that the pipeline would provide several billion dollars worth of economic benefits to the four-state region.

Meanwhile, on Wednesday a DC federal district judge took under advisement the request for an injunction stopping some of the work that was filed by attorneys for Earthjustice on behalf of the Sioux alleging that the USACE has violated the National Historic Preservation Act by ignoring the tribe’s concerns. A telephone conference on the matter has been set for Sept. 14, according to the district court clerk.

Work near the North-South Dakota state border south of the Standing Rock Sioux’s reservation has become problematic, drawing fire power from Gov. Jack Dalrymple, pipeline backers and opponents, and various levels of governmental officials in North Dakota. Dalrymple earlier declared a state of emergency to “manage public safety risks associated with the protest.”

On Tuesday, four skilled craft union presidents wrote to Dalrymple urging him to use his powers to further protect the jobs of “thousands of workers who are lawfully constructing the Energy Transfer Partners’ (ETP) pipeline being built by Dakota Access Pipeline.” And earlier a local county sheriff reported an ongoing investigation of two incidents of alleged laser strikes against aircraft being used to observe the pipeline protest site.

“Aiming a laser pointer at an aircraft is a federal violation,” said Kyle Kirchmeier, sheriff of Morton County. More than 20 people so far have been arrested on charges of disorderly conduct and trespassing onto the construction site, according to news reports. Protest leaders insist everything has been peaceful and no guns or drugs are allowed among the people occupying the protest camp.

Still pending, is Earthjustice’s Sioux Tribe lawsuit and a request for a preliminary injunction to block construction of the pipeline. The complaint, filed in federal court in Washington, DC, argues that the USACE is violating the National Historic Preservation Act by failing to address the Tribe’s concerns about the pipeline’s impact to sacred sites and culturally important landscapes, and that the river-crossing permits need to be subject to review under the National Environmental Policy Act.

The permits for the Dakota Access project were granted using the USACE “nationwide permit 12,” a fast track permitting process that has allowed the oil and gas industry to build numerous fossil fuel pipelines across the country, even on private property, without project-specific environmental review or public input process, the environmental groups contend.

“After years of pipeline disasters — from the massive tar sands oil spill in Kalamazoo, MI, in 2010, to the recent oil pipeline spills in the San Joaquin Valley and Ventura, CA — our organizations and our millions of members and supporters are concerned about the threat these projects pose to our safety, our health, and the environment,” the groups said in their Obama letter. “[This] is yet another example of an oil pipeline project being permitted without adequate public engagement or sufficient environmental review.”