The U.S. Border Patrol chief for the San Diego sector said the installation of a new wall system has made a “startling” difference in terms of illegal crossings into the country.

Fox News reported that 14 miles of 18-foot primary steel bollard fencing has been built in San Diego, along with 80 percent of a secondary 30-foot steel bollard barrier.

The system replaces 8-foot fencing made of landing mats, which were often supported by steel mesh.

“It’s incredibly different. … I’m able to see the old landing mat right next to the bollard and I’m able to see the old mesh right next to the new bollard, and the difference is startling,” Douglas Harrison, chief patrol agent of Border Patrol’s San Diego Sector, told Fox News.

The number of apprehensions in the sector dropped from 6,880 in March to 3,326 in August, the report said.

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Harrison said there has been a surge of new commercial construction in San Diego near the border as the new barriers have gone up, providing much-improved security.

“Even with the old wall system we had here in San Diego, we’ve got multimillion-dollar developments going up within sight of the border that could not have existed in the environment prior to starting to put that barrier out there,” he said.

“There was too much crime, too many people running through,” Harrison said.

Trump visited the site of the new wall construction last month and even signed his name on the new barrier.

WATCH: President Trump signs the Border Wall. pic.twitter.com/i77s5oCKU8 — CSPAN (@cspan) September 19, 2019

“So it’s a very powerful, very powerful wall, the likes of which, probably, to this extent, has not been built before,” he said.

“But the numbers now are way down,” the president added, concerning illegal crossings. “And as the wall goes up — literally, as the wall goes up, the numbers go down.”

MUST WATCH: @edhenry joined @realDonaldTrump at the border wall near San Diego to see the miles of brand-new wall being built along the border! pic.twitter.com/5rov317AJJ — GOP (@GOP) September 20, 2019

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Earlier this month, acting Homeland Security Secretary Kevin McAleenan credited Mexico with helping bring down the number of apprehensions at the southern border.

“I can say that our international partnerships have actually been essential to the progress we’ve made over the last four months. We reduced unlawful crossings by 65 percent,” McAleenan told Fox Business.

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“Families coming from Central American are down 80 percent,” he said. “That was a key driver of the crisis.”

Mexico is securing its own southern border, and Guatemala, Honduras and El Salvador have ramped up their efforts to stem the flow of migrants.

“Really what we’ve seen is those administrations step forward and take responsibility for migration flows, and that is unprecedented in the region,” McAleenan said.

The Border Patrol said the administration has built over 70 miles of wall along the border and expects to complete between 450 and 500 miles by the end of next year.

Border Wall System update: ▫️73 miles completed

▫️160 miles under construction

▫️276 miles in pre-construction pic.twitter.com/X8i0pj5iuQ — USBPChief (@USBPChief) October 15, 2019

Last month, the Supreme Court gave the Trump administration a major victory by upholding a policy that requires anyone seeking asylum in the U.S. to apply in Mexico or other countries they pass through first.

The court’s 7-2 ruling is not a final decision on the merits of the case but does prevent any lower court from issuing an injunction against the policy while the litigation proceeds in the 9th U.S. Circuit Court of Appeals and other jurisdictions.

Time-lapse video of the 30-foot replacement wall being installed in #YumaSector near San Luis, AZ. Over 10 of the 27 miles for this project have been completed to date. @CBP pic.twitter.com/cp3JCy83PT — CBP Arizona (@CBPArizona) August 24, 2019

The administration also issued its Migrant Protection Protocols, which require those seeking asylum in the U.S. to remain in Mexico while they await their immigration hearings.

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