WASHINGTON (Reuters) - In a wide-ranging request for documents and analysis, President-elect Donald Trump’s transition team asked the Department of Homeland Security last month to assess all assets available for border wall and barrier construction.

U.S. Republican presidential nominee Donald Trump appears at a campaign roundtable event in Manchester, New Hampshire, U.S., October 28, 2016. REUTERS/Carlo Allegri/File Photo

The team also asked about the department’s capacity for expanding immigrant detention and about an aerial surveillance program that was scaled back by the Obama administration but remains popular with immigration hardliners. And it asked whether federal workers have altered biographic information kept by the department about immigrants out of concern for their civil liberties.

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The requests were made in a Dec. 5 meeting between Trump’s transition team and Department of Homeland Security officials, according to an internal agency memo reviewed by Reuters. The document offers a glimpse into the president-elect’s strategy for securing the U.S. borders and reversing polices put in place by the Obama administration.

Trump’s transition team did not comment in response to Reuters inquiries. A spokeswoman for the Department of Homeland Security and U.S. Customs and Border Protection declined to comment.

In response to the transition team request, U.S. Customs and Border Protection staffers identified more than 400 miles along the U.S.-Mexico border, and about the same distance along the U.S.-Canada border, where new fencing could be erected, according to a document seen by Reuters.

Reuters could not determine whether the Trump team is considering a northern border barrier. During the campaign, Trump pledged to build a wall and expand fencing on parts of the U.S.-Mexico border but said he sees no need to build a wall on the border with Canada.

One program the transition team asked about, according to the email summary, was Operation Phalanx, an aerial surveillance program that authorizes 1,200 Army National Guard airmen to monitor the southern border for drug trafficking and illegal migration.

The program once deployed 6,000 airmen under President George W. Bush but was downsized by Barack Obama, a move blasted by some conservatives who argue the surveillance is vital to border security.

POLICY SHIFT

The transition team also asked for copies of every executive order and directive sent to immigration agents since Obama took office in 2009, according to the memo summarizing the meeting.

Trump has said he intends to undo Obama’s executive actions on immigration, including a 2012 order to allow children brought to the U.S. illegally by their parents to remain in the country on temporary authorizations that allow them to attend college and work.

The program, known as DACA, collected information including participants’ addresses that could theoretically be used to locate and deport them if the policy is reversed. Another request of the transition team was for information about whether any migrant records have been changed for any reason, including for civil rights or civil liberties concerns, according to the internal memo seen by Reuters.

A Department of Homeland Security official, speaking on condition of anonymity, said the agency interpreted the request to mean the transition team wanted to make sure that federal workers were not tampering with information to protect DACA recipients and other migrants from deportation.

On the campaign trail, Trump vowed to deport more undocumented immigrants, a promise that may have prompted the transition team’s request for information about the feasibility of expanding temporary detention facilities.

The internal memo summarizing the meeting between Trump’s transition team and U.S. Customs and Border protection said the team had requested a comprehensive picture of border security as well as resources available for walls and barriers.

The Department of Homeland Security official said agency representatives who attended the meeting believed the request to include both the northern and southern borders. U.S. Customs and Border Protection then prepared a report on specific locations and costs of building a fence along the U.S.-Canada border.

Reuters reviewed a copy of the report, which estimated the cost of building fencing along the northern border fence would be $3.3 billion and cover 452 miles along border of Canada and the states of Washington, Idaho, Montana, New York, Vermont, New Hampshire and Maine.

Adding 413 miles of fencing on the southwest border would be more expensive, according to the estimate of $11.37 billion, because it would be aimed at keeping pedestrians as well as vehicles from crossing.

Pedestrian fences require more staff and would cost $11.2 million per mile versus $4.1 million per mile to build to build, according to the report.

In fiscal year 2015, the latest year for which data is available, border patrol agents apprehended 2,626 illegal migrants on the U.S.-Canada border compared to 331,333 apprehended on the U.S.-Mexico border.