The construction of Israel’s underground security barrier aimed at countering the Hamas terror group’s attack tunnels is picking up speed, the head of the IDF’s Southern Command said Wednesday, with hundreds of workers operating around the clock on the massive engineering project.

Maj. Gen. Eyal Zamir said the military was concerned that the construction on the barrier could spark a conflict with Hamas. The terror group sees its tunnels as a central weapon in the fight against Israel and the Defense Ministry’s barrier presents a threat to them.

“We hope they don’t try to challenge us,” he said.

Another military official added on Thursday that the army does not believe Hamas has any justification — “ethical, moral or military” — to prevent Israel from building a protective barrier. It will therefore not tolerate any attempts by the terror group to interfere with its construction, the official said.

“If it tries to, Israel will defend this barrier in every way possible,” the official said. “This barrier will be built. Period. At any price.”

In addition to disclosing additional information about the border barrier, the military on Wednesday also revealed that it had found two alleged Hamas tunnel sites buried beneath an apartment building and a family’s home in the northern Gaza Strip.

IDF Chief of Staff Gadi Eisenkot, center, visits the Gaza Division with Col. Yaakov “Yaki” Dolef and head of the Southern Command Maj. Gen. Eyal Zamir in southern Israel on August 30, 2016. (IDF Spokesperson)

IDF Chief of Staff Gadi Eisenkot, center, visits the Gaza Division with Col. Yaakov “Yaki” Dolef and head of the Southern Command Maj. Gen. Eyal Zamir in southern Israel on August 30, 2016. (IDF Spokesperson)

Zamir accused the Hamas terror group of purposefully building the tunnels under civilian structures to provide cover for its operations. That being the case, the general warned, “these sites are legitimate military targets. Anyone inside of one, should another conflict begin, endangers himself and endangers his family, and the responsibility is on the Hamas organization.”

The work on the 37-mile (60-kilometer) barrier began in earnest earlier this summer, and Zamir said it would be completed within two years. It will feature an advanced underground protection system that extends dozens of meters below the ground — the army would not specify the depth — in order to detect and destroy tunnels that attempt to penetrate into Israeli territory, as well as an above-ground metal fence adorned with sensors.

The Defense Ministry will also bulk up the defense along the Gaza coast, putting up breakwaters and other protective measures in order to prevent infiltration into Israel from the sea, as occurred during the 2014 Gaza war.

The military proposed building the barrier following the 2014 Gaza war, known in Israel as Operation Protective Edge. During the fighting, Hamas made extensive use of its tunnel networks to send fighters into Israel as well as to move its terrorist operatives and munitions within the Gaza Strip.

IDF infantrymen congregating around a tunnel entrance in Gaza, July 24, 2014. (Courtesy IDF Flickr)

IDF infantrymen congregating around a tunnel entrance in Gaza, July 24, 2014. (Courtesy IDF Flickr)

However, some experts harbor doubt that the barrier will truly be the silver bullet to the tunnel problem that it’s often considered.

“There is no physical barrier that cannot be overcome,” said Col. (res.) Yossi Langotzky, who previously served as adviser to the IDF chief of staff on the threat of tunnels, during a conference on the issue last year.

Col. (res.) Yossi Langotsky, a former adviser to the IDF chief of staff on the issue of tunnels. (Weinspen/Wikimedia)

Col. (res.) Yossi Langotsky, a former adviser to the IDF chief of staff on the issue of tunnels. (Weinspen/Wikimedia)

He told The Times of Israel at the sidelines of the conference that should Israel build a system that could detect a tunnel up to dozens of meters underground, Hamas will only furrow deeper to build their tunnels.

The project is expected to cost approximately NIS 3 billion ($833 million), with each kilometer of the underground portion of the barrier costing approximately NIS 41.5 million ($11.5 million). The above-ground fence is significantly cheaper at just NIS 1.5 million ($416,000) per kilometer.

In order to speed up construction, concrete factories were built next to the Gaza Strip.

“We’re working according to plan on the barrier. In the next few months, this project is going to gain significant momentum,” Zamir said.

Currently, dozens of construction workers and engineering specialists from around the world are working on the project, at a few different sites, in order to fine-tune their operating methods. They wear flak jackets and are guarded by IDF soldiers.

By the year’s end, over 1,000 people, both Israelis and migrant workers, will be operating on the border barrier in approximately 40 locations.

This February 10, 2016, file photo shows IDF soldiers keeping watch as a machine drills holes in the ground on the Israeli side of the border with the Gaza Strip as they search for tunnels used by Palestinian terrorists planning to attack Israel. (AFP/Menahem Kahana)

This February 10, 2016, file photo shows IDF soldiers keeping watch as a machine drills holes in the ground on the Israeli side of the border with the Gaza Strip as they search for tunnels used by Palestinian terrorists planning to attack Israel. (AFP/Menahem Kahana)

The order in which the areas along the border receive the underground barrier is determined in accordance with an assessment of the security risk, a military official said last year.

The Defense Ministry offered tenders to a variety of companies, who are charged with building not only the underground barrier but also army posts and command-and-control centers along the border.

The barrier is being built inside Israeli territory, Zamir said. The current metal fence surrounding the Strip, which lies exactly on the border, will remain in place, while the new fence is built a few dozen meters inside Israel.

Illustrative. A hydromill at a construction site in Tel Aviv. (Sharshar/Wikimedia/CC BY-SA 4.0)

Illustrative. A hydromill at a construction site in Tel Aviv. (Sharshar/Wikimedia/CC BY-SA 4.0)

In order to construct the underground barrier, the workers are using a German hydromill, a powerful piece of drilling equipment that cuts deep, narrow trenches into the earth.

In addition to opening up the ground where the barrier will be constructed, the hydromill is also expected to expose any previously undiscovered or newly dug Hamas tunnels that enter Israeli territory.

The space left behind by the hydromill — and any Hamas tunnels that get in the way — is then filled with a substance known as bentonite, a type of absorbent clay that expands when it touches water.

This is meant to prevent the trenches from collapsing, but also has the additional benefit of indicating the presence of a tunnel, as the bentonite would quickly drain into it.

Workers then pour regular concrete into the trench. Metal cages with sensors attached are then lowered into the concrete for additional support.

In the briefing, the general described the current situation in the Strip as precarious. “On the one hand there’s stability, on the other it’s potentially explosive,” he said.

Zamir said Hamas does not appear interested in fighting a war with Israel now. “We see that Hamas is deterred, restrained and is also reining in terror attacks” from Gaza.

‘On the one hand there’s stability, on the other it’s potentially explosive’

In July 2014, Israel launched Operation Protective Edge in response to rocket fire from Gaza. During the 50-day campaign, the IDF destroyed some 14 tunnels that entered Israeli territory, along with 18 internal tunnels, and depleted Hamas’s weapons stores.

In the time since the 2014 war, on average between one and two rockets have been fired from Gaza into Israel each month. They have been fired by fringe Salafist groups, not by Hamas, which took control of the Strip in 2007 and has ruled the coastal enclave ever since.

But Zamir added that while the terror group is working to prevent attacks in the Strip — Tuesday night’s rocket notwithstanding — Hamas is still “fanning the flames” and directing terrorist activities in the West Bank and Jerusalem.

“It is also continuing to strengthen itself and prepare for the next war,” Zamir said.