On 6 January 1970, 22 frogmen from Underwater Demolition Team TWELVE began blasting a narrow, five-and-a-half mile canal across a remote plain in South Vietnam. If successfully completed, the Kinh Gay (Gay Canal) would be the first canal ever to be constructed with demolitions in Vietnam—and the largest combat demolition job in U. S. naval history.
This operation—“Deep Channel”—was being undertaken to cut the enemy’s busiest infiltration route into Saigon and the upper Mekong Delta near its origin at the Cambodian border. When completed, it would connect two major rivers, the Song Vam Co Tay and the Song Vam Co Dong, providing a vital interdiction route for naval patrol boats and a timesaving commercial route for the civilian population.
Time was not on the frogmen’s side. The expected Tet offensive early in February was rapidly approaching. Local intelligence sources warned that the area where the crew would be working would be heavily trafficked at night by the enemy. The headquarters for Viet Cong and North Vietnamese Army (NVA) battalions and a VC mobile force totalling 550 men was reported to be within 20 kilometers of the canal site and intelligence warned that terrorist raids, mortar attacks, and booby-trapping should be expected during the operation.
The blasting would occur within sight of the Cambodian border on the swampy Plain of Reeds, approximately 35 miles east of Saigon. The two rivers parallel the borders of the “Parrot’s Beak” section of Cambodia and join southeast of Saigon to form the handle of the “Giant Slingshot” which feeds the Mekong Delta river system.
The Kinh Bobo, an overgrown, neglected canal which runs southeast from the Parrot’s Beak toward the confluence of the two rivers, was known to be the most important of numerous infiltration routes into Saigon from this part of Cambodia. The entire Parrot’s Beak region was a major staging and rehabilitation area for Viet Cong and NVA troops. Estimates of the number of enemy in that region ranged at various times up to 60,000. Using the Kinh Bobo and related streams, the enemy could move virtually without interference to within ten miles of Saigon.
A year earlier, in December 1968, ComNavForV had established Operation Giant Slingshot, in which a combined force of U. S. and Vietnamese Navy patrol craft had been ordered to interdict these rivers, canals, and their tributaries.
There was no navigable waterway which offered access to the Kinh Bobo, and it had become clear to NavForV that this route would have to be heavily patrolled if the operation was to have a chance of success. The logical solution was to extend the Kinh Gay southwest to meet the Kinh LaGrange, thus opening a direct waterway between the villages of Tuyen Nhon and Tra Cu on the two rivers. This route would be 30 kilometers long, and would allow a 20-minute reaction time to any point along the canal from either of the Navy’s advanced tactical support bases (ATSBs) at Tuyen Nhon or Tra Cu.[*]
[Map of canals in the vicinity of the Plain of Reeds]
ComNavForV had requested studies to determine the feasibility of dredging the distance between the existing canals. Both had been dredged by the French in the 1940s and 1950s but the Kinh Gay had never been completed. Work on the Kinh LaGrange had been terminated in 1953 after the Viet Minh had sabotaged the original dredge and its two replacements. The distance that would have to be made navigable was 8.6 kilometers, or 5.45 miles. A portion, 5.3 kilometers of this—from the end of the LaGrange to the intersection with the Kinh Bobo—was an oversized drainage ditch long overgrown with weeds. Once, perhaps, it had been wide enough for a sampan, but now it was only a habitat for reptiles and birds and a hiding place for enemy munitions. The remaining 3.3 kilometers had once been a navigable section of the Kinh Gay, but could not bear even small motorized traffic now without weed clearance and deeping.
In July 1969, the Force Civil Engineers had reported to ComNavForV that dredging bids ranged from $2.6 to $5 million, with completion estimates ranging from seven to 18 months. Even the lowest cost was prohibitive, and the time inconceivable. A construction company operating in such remote, hazardous terrain would be exceptionally vulnerable, and would require three permanent U. S. Army platoons for security. Furthermore, the large size of the dredge would create a canal much bigger than necessary for PBRs and indigenous craft to pass.
It had been suggested that the job might be done with demolitions, and seven specialists from UDT Twelve were deployed to the area with an assortment of demolitions to determine if this was feasible. Their tests confirmed that blasting with military explosives would be possible and well within acceptable time and cost limitations. Provided that the necessary explosives were on hand, it was estimated that a canal five feet deep, 30 feet wide, with turn-around areas every 1,000 feet, could be completed in 45 days for under $500,000. The great advantage was that this could be accomplished exclusively with military assets.
ComNavForV made the decision to proceed with the plans for the operation. Since UDTs deployed in WestPac are assets of Commander Seventh Fleet, permission had to be obtained to “borrow” enough additional men to do the task. Two officers and 20 men were deemed adequate for the job. UDT Twelve Detachment Delta, originally comprised of one officer and four enlisted men, was reinforced with six men who were on loan to NavForV (serving with other UDT units in-country) and 11 others approved by ComSeventhFlt. The detachment was assigned to Task Group 194.9, Giant Slingshot.
Lieutenant (j.g.) Walter R. Harvey, U. S. Navy, was designated officer-in-charge of the job, and in mid-November, he was assigned to write the operation order and to oversee all preparations. With assistance from NavForV and the newly-formed Naval Special Warfare Group, Vietnam Detachment—created to supervise UDTs, Sea, Air, Land (SEAL) Teams and Mobile Support Teams in-country—the Lieutenant ordered the demolition material and made arrangements for ground security forces, artillery and air support, equipment, berthing and other logistical needs.
Tentative plans were made to begin the operation on 4 January 1970, the earliest possible date. All plans were contingent upon the arrival of the demolitions—6,200 lengths of Mark 8, Mod 2 explosive hose—the 230 tons representing 60% of the Free World’s supply. Only 400 lengths were on hand in WestPac; the rest had to be shipped from the states, and the projected date of arrival in Vung Tau, RVN, was 8 January. It was decided to move the detachment up the river from Naval Support Activity, Nha Be, on 4 January, and begin work two days later with the 400 lengths on hand—at least two days’ supply. The remainder was expected to arrive by 9 or 10 January. To allow for the uncertainties of in-country transportation, members of the new detachment had been released from their prior units before New Year’s day, and filtered into Nha Be over the holiday. On the morning of 4 January, the 22 piled their gear into the welldeck of an LCM-8, amid forklifts, air mattresses, demolitions equipment, and motion picture gear, the latter being the property of Navy and DoD cinematographers who were aboard to document the event. Two Vietnamese LDNNs (Navy frogmen) were also on board to assist with the rigging and hauling of demolitions.
Many of the UDT men had not seen each other since before the team deployed in August, and were enjoying the reunion. The group included three chief petty officers and four first class petty officers, the bulk of the team’s senior enlisted men, and the best of the younger operators. About half of this group would be spelled by other team members by the time the job was finished.
Although, during the two-day trip to Ben Luc and Tuyen Nhon, they made jokes about the hazards of the job, most were not without private apprehensions, especially those with the burden of responsibility—Lieutenant (j.g.) Harvey and Chief Gunner’s Mate George B. McNair, who, for 18 years, was a member of a UDT and was the team’s most experienced demolitions man.
Among the numerous problems confronting the planners was the transportation of 230 tons of explosives from ConUS to Vietnam on time, and then moving them safely to the blasting site. For safety reasons, no more than three days’ supply could be stockpiled at ATSB Tuyen Nhon.
Chief McNair had an immediate solution for the laying of the explosives which he believed would eliminate the transportation problems, increase the safety factor, and cut the operation time in half. The charges would be rigged by section at Vung Tau, flown by CH-46 Chinook helicopter to the canal site, connected, and blasted. This would eliminate a need for forklifts, boats, and a stopover in Tuyen Nhon. Lieutenant (j.g.) Harvey, however, was unable to obtain this crucial service until the canal was almost half-finished, after many alternate methods had been tried and discarded.
Lieutenant (j.g.) Harvey had to plan a second method. Demolitions would be flown to Tuyen Nhon, and moved by forklifts onto LCMs. Boats would carry it to near the blasting site, where it would be implanted by hand with the assistance of flotation devices, and detonated. The obvious problem was moving the charges up the narrow new canal as it progressed. It was questionable that even an LCM-6 could navigate the canal. Other smaller craft were to be available if this failed; and as a last resort, demolitions could be moved a long way by hand.
Another consideration was the spirit of the men, who were not comfortable about the open location of the job, its length, or the security measures provided for it. Lieutenant (j.g.) Harvey had to settle for Army Air Cushion Vehicles and Civilian Irregular Defense Group soldiers (CIDG) in lieu of regular Army troops. The ACVs would circle the crew as it worked, providing a mobile perimeter, and four CIDG would ride each ACV. There were, however, qualms about the CIDG, Vietnamese mercenaries whose reputation for reliability was spotty at best.
Ostensibly, Operation Deep Channel was just a bigger demolition job, but the situation was significantly different here than in any of the riverine reconnaissance, demolition or patrolling work which the UDT had been doing in Vietnam since 1968. Here the frogman would work unarmed, with both feet in deep mud, literally miles from any cover or concealment, amid poisonous krait snakes. Every afternoon at about the same hour, he would announce his precise location and his day’s progress to the enemy with a multi-ton explosion visible for 20 miles. He would then go home via exactly the same dangerous route he had come to work, with no alternate or escape routes, and he would rely entirely on unfamiliar men and machines for his defense.
These were the very same conditions he had spent 20 arduous weeks in UDT/SEAL training learning to avoid, for obvious reasons. The crew was only slightly reassured by the fact that artillery from three locations, and helicopter gunships, and fixed-wing planes would be available on an on-call basis.
The Advanced Tactical Support Base (ATSB) at Tuyen Nhon was comprised of a long row of “hooches” (huts) strung out along one side of the Kinh LaGrange. It was protected against the open grassy spaces by armed watch towers, a complex network of barbed and concertina wire, and a field of claymore mines and trip flares. On one side of the base was a Special Forces camp; on the other, a short clay airstrip that could barely accommodate the C-130 aircraft which would bring in the demolitions.
The base was headquarters for the U. S. and Vietnamese patrol craft which were tied along the canal in front of the hooches—many PBRs, ASPBs (Armored Support Patrol Boats), Monitors, ATCs (Armored Troop Carriers), and LCMs. Although primitive, mosquito-ridden, and muggy hot, certain human comforts were evident: electric fans, armchairs made by local villagers, unopened tins of Christmas treats, and innumerable friendly dogs.
Just after dawn on the morning of 6 January, the team boarded two ASPBs and two LCM-8s, one of which carried 400 crated charges of explosives. The small convoy headed northeast on the Kinh LaGrange, toward Fire Base Gettysburg, where the blasting would begin. Along the banks of the Tuyen Nhon village, bleary-eyed children in undershorts watched the boats, still too sleepy to yell for the tins of C-Rations that the sailors often threw to them.
Across the Song Vam Co Tay was the Plain of Reeds, an endless flat ocean of grass with a few clumps of trees barely visible to the west in Cambodia. Boat crews manned their guns. From long habit, the UDTs carried M-16s. This desolate 12-kilometer stretch between the river and the fire base was the likeliest place for an ambush.
Less than a mile from the fire base, the men passed by seven brown bodies, enemy soliders [sic] who had been gunned down by helicopters three days before.
The Kinh LaGrange River ended abruptly at the fire base where the French had stopped dredging. The security forces were already waiting: common radio frequencies and call signs were established and the procedures reviewed.
The LCM-8 had dropped its ramp in the mud at the end of the LaGrange. At 0840, work began without confusion, under the supervision of Chief McNair, the crew commenced to rip apart the wooden crates that housed the demolitions. The welldeck and ramp of the LCM provided a handy working platform for rigging.
During the October tests, the Mark 8 hose had been found to be more effective and faster than any combination of M-3-shaped charges, 40-lb. cratering charges, or C-4 demolition packs. The hose consists of a reinforced rubber fabric casing filled with Composition “A” and aluminum powder, with a TNT booster at either end. Each charge weighed 75 pounds, was 25 feet long, and was 2.5 inches in diameter. It was connected at either end with a male or female brass coupling, with a recession for an electric blasting cap. The charge looked so similar to a length of conventional fire hose that it was frequently mistaken for it.
For use on most of the canal, five lengths were lashed together into a pyramid to form a 25-foot section of charge. Each charge was moved into its position along the canal bed and coupled with the ones before and after it. One end of the entire length was then fitted with a blasting cap and connected to a reel of electrical firing wire. The shot was detonated from at least 400 or more feet away. In theory, there was no limit to the size or length of the charge. If 8.6 kilometers of explosives could be planted in one day, a twist of the wrist could detonate the whole business.
The first day’s operation was surprisingly smooth. The goal was to complete the 400-foot connecting link from the LaGrange to the Kinh Gay extension, and make the 90 degree turn to the northeast toward the navigable portion of the Kinh Gay. One group uncrated and rigged the hose while two groups staggered through the water and mud and coupled the charges together. About half of this connecting link to the Kinh Gay extension was now a pond, which had been created during the October tests. It was decided to blow the area again to assure continuity of the canal. Parts were so deep that men had to swim the charges into position on air mattresses.
Beyond this experimental section was muck and tangled growth, with a fast trickle of water just wide enough to permit the mattresses to be pulled upstream between the weeds. After a few minutes on the job, the crew members were so wet and filthy that they changed from whatever uniforms they had worn to swim trunks and boots. The motion picture teams, equally dirty, were recording all of this for posterity on a variety of cameras and recording machines.
By noon, the shot had been prepared almost as far as the turn. It had been decided to limit the length of this explosion because of the proximity to Fire Base Gettysburg. This base, located just 6.5 kilometers from the tip of the Parrot’s Beak, was a cleared dirt area occupied by three Army artillery platoons. Their fulltime job was to provide gunfire support for any targets within range. Because of the demolition activity, artillery operations had been suspended for two days, and the weapons and projectiles had been sandbagged and covered to prevent possible damage from shock or falling debris. The base captain had moved his troops well to the rear in anticipation of the blast. They collected in a large crowd, where a carnival spirit prevailed; the occasion which had given them two days’ rest was providing some entertainment, too, a rare occurrence on the Plain of Reeds.
The device used for detonating an electrical explosion is called a “Hell-Box” and, for obvious safety reasons, its handle is never attached until all parties are ready for the explosion. It is the responsibility of the man supervising the shot to keep it on his person until this time. At 1210, Chief McNair twisted the handle, instantaneously detonating the first explosion of Deep Channel.
Before a blast there is a quiet, expectant calm. Suddenly, before there is any noise at all, a black wall 500 feet long bursts upward from the flat land like a phalanx of geysers. The huge explosion and staggering shock wave follow, and the wall keeps rising, hundreds of feet into the air and perfectly intact. At its peak, well over 300 feet high, the wall begins to disintegrate. Millions of particles of soil and water are atomized and suspended for seconds, apparently motionless, looming tike a ponderous thundercloud above the plain. Then, huge chunks of earth splatter noisily along the banks of the new canal behind the veil of black mist, which slowly begins to fall. The smaller hunks hit the ground first and then everything streams back to earth in a heavy, hissing mud rain.
Like oil erupting from a new well, the mud from this blast coated everything with a sludge-like gray film. Chief McNair and Lieutenant (j.g.) Harvey, black from the murk, emerged grinning and led the crew through mounds of sucking mud to survey the new stretch of canal. The mud had been blown up and away from the canal bed, and two vertical banks had been formed, they had been packed hard enough by the blast to resist crumbling under the weight of the water which was draining back into the canal.
The CIDG troops had left the ACVs and foraged in the mud for stunned fish which, along with krait snakes and other fauna, were scattered along the banks.
The new canal was rapidly filling with water from the Kinh LaGrange; several members plunged into it to test the depth. One 50-foot section just before the turn was too shallow, and would have to be blown again.
Two more shots were blown the first day: the second smoothed and widened the turn from the Kinh LaGrange onto the connecting segment, and the third eliminated most of the shallow spot and turned the corner, pointing the new waterway toward the Kinh Gay and Tra Cu.
The labor involved in preparing this final shot indicated more serious problems to come. The LCM-8 which carried the demolitions could not navigate the new canal. The ASPBs could enter the canal, but with their four-foot draft, mud was sucked into the sea-strainers and pumps so they could not be used. For the third shot, the demolitions could not be brought by boat to the spot where the charges would be laid. They would have to be moved by hand or floated the 500-foot distance the first two shots had covered before the men could begin to lay them. If 1,000 feet were to be implanted, the last charge would have to be moved 1,500 feet. Implications of this were obvious. If some mechanical means of moving the charges from Fire Base Gettysburg up the new canal to the work site were not found, the men might wind up moving the final charge of the operation, 8.6 kilometers, by hand. Lieutenant (j.g.) Harvey had envisioned this problem when his request for helicopters was turned down in December. He had been assured that an LCM-6 could traverse the canal, and would be available for the job. To date, however, no LCM-6 had arrived for work, and there was no indication that one was on its way.
In spite of this dim prospect, the crew was elated, if weary, on the return trip to the ATSB late that first afternoon. Their apprehensions had eased as they had caught the spirit of teamwork in the mud, and the blasts had been eminently satisfying. Oppressive as the mud was, it offered comic relief. People slipped and fell in it, wallowed in it, became stuck in it, and even flung wads of it at each other.
That evening, a crew meeting was called at the ATSB to discuss the problem of moving demolitions up the canal, and to hear suggestions for improving procedures. It was immediately decided to radio to CTG 194.9 (Giant Slingshot) to request an LCM-6 or an LCVP—realizing that these, too, might fail, but were worth a try. There were three other possibilities: hauling the demolitions up the canal by PBR, towing them with motorboats on flotation devices, or moving everything by hand.
In his planning, Lieutenant (j.g.) Harvey had relied heavily on the PBRs as the sure alternative if all else failed. But because of her size, each PBR could carry only small amounts of hose at a time, and on a given day each boat would take quite a beating going up and down the new canal. Finally, the PBR commander at Tuyen Nhon stated flatly that he had other commitments for his boats and hence did not feel he could subject them to this beating on a regular basis.
Both of Detachment Delta’s outboard engines were still awaiting repair in Nha Be, where they had been for two months, and no others were readily available to power the Boston Whalers.
At this meeting the crew also decided to uncrate and pyramid the hose on the LCM-8 in the mornings while en route to the first fire base. (The LCM-8 would continue to be used until replaced by a smaller craft.) The trip up the Kinh LaGrange took over an hour, which would allow time for rigging and would then free everyone to haul the hose up the canal bed. The prospect of being on board a craft loaded with eight tons of explosives was not enticing, but the risk had to be taken.
The next morning, the crew made an important discovery: the Vietnamese villagers craved the wood from the demolition crates. They would use all they could get. Reaching the village of Tuyen Nhon, the crew stopped to buy ice and found they could trade wood crates for it. Subsequently, the crates were traded for more ice, for food, for sundries made by the local Vietnamese, and for labor.
When the crew reached the fire base, all charges were rigged. The next two days passed without unexpected problems. Charges were floated along the finished canal, and then pushed on air mattresses through the choked weeds and mire of the ditch. A trickle of water less than three feet wide ran swiftly southwest, allowing space for the mattresses. Thus, the remainder of the 400 lengths of Mark 8 hose on hand was expended, and the crew ceased operations for two days while waiting for the new supply of demolitions, which had arrived as scheduled at Vung Tau on 8 January.
During this stand-down, an LCM-6 arrived from somewhere downriver. Ironically, no one, not even her crew, knew who was responsible for sending her to Tuyen Nhon. The boat was in disgraceful condition; one engine dead and the other dying. The steering was in disrepair and the ramp didn’t function at all. Ship-fitters and enginemen in the UDT crew repaired one engine, the steering, and the ramp, making the craft marginally functional for operation.
By this time, Lieutenant (j.g.) Harvey had made an agreement with the captain of the local CIDG forces to exchange labor for wooden crates. The CIDG began work on 10 January, and continued to uncrate and rig charges regularly under the supervision of one UDT man. This might have worked had it not occurred to the CIDG captain that he should get an extra crate for himself for each man he provided. This irked Lieutenant (j.g ) Harvey, who promptly fired him and employed local villagers.
Work began again on 11 January, using the renovated LCM-6. It performed, but not smoothly. Since the tide was in its neap phase, there was insignificant change in the water level, and the LCM could traverse the new canal and provide a working platform as the LCM-8 had done. Getting the boat up the canal was one thing, but coming back out was something else again. Indentations were blasted every 1,000 feet to provide space for the PBRs to turn around, but these were not big enough to accommodate an LCM. It was a difficult stunt indeed to back this craft down a 25-foot wide canal on one engine, but even this was infinitely preferable to the alternatives of moving the explosives by hand.
On the fourth day of this procedure, 14 January, the crew encountered its second shallow spot 1,000 meters from the first turn. This was the second of three such areas which would slow the operation. Three unsuccessful attempts were made to deepen this section with extra loads of explosives. The spot was deep enough to allow the passage of a PBR, but the LCM-6 could not cross it. It was decided to continue with the canal, returning to deepen this section later, time permitting, when an effective method for doing the job was worked out.
The reason for the difficulty lay principally in the composition of the ground. Explosives must encounter resistance. The more resistance, the more effective the explosion. These shallow spots were narrow corridors of the plain which were less compact, and which contained more moisture and more absorbent organic materials than other areas. Because of their porosity, the abundant waters of the plain moved easily through these corridors. The canal happened to transect three of them. They absorbed the shock, and more sophisticated techniques would be needed to bring them to the required depth.
The LCM-6 limped along for several days after the shallow spot was reached, and then it was grounded there, and the demolitions were moved beyond by other means. Initially, they were dragged and floated by hand, and then someone suggested that the Air Cushion Vehicles might be able to tow the charges. Motorized boats could not be used because of the density of the weeds. The O-in-C requested the service of ACVs from CTG 194.9, and was provided with a smaller variety of air boat, a craft similar to the type used in the Florida Everglades, which served the purpose well. Slowly, 2,000 more meters were blasted using these methods. The hose had to be towed gently and carefully through the weeds, but it saved considerable labor.
Anything that saved labor helped. Since the beginning of the operation, the forklift had been an invaluable tool for moving the crates of demolitions from the aircraft, and then for moving rigged charges into the welldeck of the LCMs. About the time the second shallow spot was encountered, the forklift broke down, and, for several days, the UDTs and CIDG troops had to do everything entirely by hand. Crates were broken open on the plane and charges were carried off individually. They were then rigged as usual, and carried by shoulder onto the well deck of the LCM. Such labor, occurring before and after the working day in the mud, took its toll psychologically as well as physically.
During this week, the Commander of Naval Forces, Vietnam, Vice Admiral Elmo Zumwalt, made his first of several visits to the canal site, where he was briefed on the progress and technical problems, and stayed to watch the day’s explosion.
On the morning of 19 January, the daily load of demolitions came from Vung Tau, not by C-130 or Caribou aircraft as usual, but by CH-46 Chinook helicopter—exactly what Lieutenant (j.g.) Harvey had originally asked for, and which subsequent events had proven were badly needed. He reasoned now that if they could fly the 180-mile round trip, they could probably hop the extra 10 or 15 miles to the canal site on the return route. He notified CTG 194.9 of this proposal, and suggested that the helos bring a cargo net of crated hose to ATSB Tuyen Nhon, exchange it there for a cargo net of rigged charges, drop these at the blasting site, and return to Vung Tau. Possibly Lieutenant (j.g.) Harvey’s conversation with Vice Admiral Zumwalt several days before had had something to do with the prompt response to the request. The first day of helo operations would confirm that the idea was indeed worthwhile.
On 22 January, after about three kilometers had been completed, two helos delivered nets of 20 rigged charges down at a smoke signal along the canal site. The UDT crew assembled the charges along the bank, rolled them onto air mattresses or rubber boats, and floated ten to the left and ten to the right of where they had been dropped. A third cargo net appeared, and 1,500 feet were implanted and successfully detonated that day. The previous maximum distance achieved had been 1,000 feet. The average had been about 750.
For each of the next three days, helos were promised, and each day the crew travelled to the site by PBR and waited. The helicopters never came. Shortly after noon each day, Lieutenant (j.g.) Harvey secured the ACVs and CIDG troops and returned with his men to the ATSB. Previously, there had rarely been any time on the work site to relax or loiter, and now there were three long mornings. The crew was now a long distance from the relative security of the fire base, and, with nothing to fill their time, the men began to grow impatient and anxious.
At about 1600 on the third day, long after the crew had returned, word came that two helicopters with demolitions would arrive at Tuyen Nhon at 1800. Because of the hour and the absence of security, Lieutenant (j.g.) Harvey decided not to take his people to the canal site that evening, but his decision was overruled by the UDT Twelve Executive Officer, who felt that an alert unit of 20 frogmen, if necessary, could handle any of the smaller enemy units that would be moving through the area. FAC (Forward Air Control) observer pilots regularly reported numerous sampans and small groups of enemy soldiers gathering along the Cambodian border before sunset, but rarely saw units of more than ten men.
The crew departed from Tuyen Nhon about 1700 in PBRs, armed with M-16s, grenades, and a heavy load of ammunition. Much of their work would be done in twilight, possibly in dusk—prime hours for the enemy to be crossing the approximate area of the canal. The regular daytime security force had been secured; and the Air Cushion Vehicle platoon which was normally assigned to set night ambushes along these infiltration routes would not be present that night because of mechanical difficulties in Ben Luc, some distance away. Nor would helo gunships be available for overhead surveillance and protection. This meant that the UDT crew would have to provide its own security while working that evening. The likelihood of obtaining helicopters for emergency evacuation, if necessary, would be slim. A fourth consideration was that the tide was in its full moon phase, and would be approaching low. There was some question as to whether the PBRs would be able to passage the canal at all, much less cross the shallow spot 2,500 meters from the blasting site.
The crew went—not encouraged by the situation, but eager to work, nevertheless. A perimeter guard was posted 50 meters from each side of the canal site: one man each beyond the limits of the workers and one man in the middle. The men worked with weapons, H-harnesses, and ammunition on their backs. The hose-carrying helos arrived on schedule; 1,000 feet of explosives were rigged by 1945, and were detonated by 2000.
But now the tide had fallen too low. The PBRs had not been able to cross the shallow spot, and were awaiting instructions at the fire base. No helicopters were available in the area to extract the men. The crew lost radio contact with Gettysburg and then with the PBRs. Then they lost radio contact altogether.
There was no choice but to walk out. Darkness had fallen and the moon had not yet risen. The crew assumed a loose patrol formation in the chest-high grass along the canal, and began to sweep southwest in the same manner that they had searched the river banks for bunkers in other parts of Vietnam. They hand-carried the demolition chest, air pumps, and most of the mattresses. A few others were used to float the two 150-pound cargo nets which they towed along the canal.
After they had covered almost half the distance back to the fire base, a helo approached, landed on a signal, and took the men to the PBRs. Caked with mud, they returned to the ATSB after 2200, to find that the chow hall and the showers had been secured.
The following day the helicopters came in the morning and the crew blasted a record 2,500 feet in less than four hours time.
When the helicopters became an established part of the routine, the crew consumed the canal at a rate of nearly 1,500 feet per day. The most important psychological victory was the reaching of the Kinh Bobo, the focal point of the operation. The first 5.3 kilometers were by far the hardest: beyond the Bobo, the Kinh Gay was recognizable as a canal. The remaining 3.3 kilometers were impenetrably choked with weeds and partly filled with sediment, but the pyramid charges could now be reduced from five to three sections each and still clear the canal effectively.
All records for progress were broken the day the crew blasted 3,800 feet of canal, using 28,000 pounds of explosives—probably the largest single blast in UDT history. This was more than one-eighth of the total distance of the canal.
By 8 February, the dedication day for the canal, only 800 feet remained to be blasted to connect the waters of the Song Vam Co Tay with the Song Vam Co Dong. Several areas still needed attention, notably two shallow spots and one corner which had to be widened.
The solution for deepening the resistant corridors was the use of a multiple delay explosion. Instead of the usual single-pyramided length, four were used. Two were implanted in mid-canal 18 inches apart, and two others were placed along the banks. All were connected to the firing reel and detonated as a single shot, but the center charges were rigged with a 50-millisecond delay cap. The outside charges went instantaneously, creating a partial vacuum that substantially reduced the resistance for the delayed charges. This method was used successfully to deepen both spots.
The dedication of the canal was originally planned for 10 February, but the date was changed to 8 February, and ComUS MacV, General Creighton Abrams, U. S. Army, was the honored guest. With him were Vice Admiral Zumwalt, the Vietnamese Chief of Naval Operations, and four Army general officers. The UDT crew planted the last 800 feet of hose that morning. When the dignitaries arrived, Lieutenant (j.g.) Harvey briefed General Abrams on the progress and problems of the operation to date. Chief McNair explained the operation of the blasting machine, and the general took custody of the Hell-Box handle and detonated the final explosion.
Operation Deep Channel ended five days later on 13 February, after the last touches had been put on to the canal. The job had been completed in 29 working days—only two-thirds of the anticipated time—at two-thirds of the anticipated cost.
The Tet offensive never materialized, and no one on the demolition crew was even injured by the enemy, something of a miracle itself. Before the operation, Chief McNair had reasoned wryly, that, “The only reason they might not get us is if they figure they can use the canal themselves.” That theory—and the military success of the canal itself—remain to be proved.
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A graduate of Yale University in 1965 and Columbia University Graduate School of Journalism in 1966, Mr. Howard worked for several newspapers as reporter and copy editor prior to entering Officer Candidate School in January 1967. In December 1968, he completed UDT Basic Training at Coronado, California, and served as platoon officer, intelligence officer, and public information officer with UDT-12 until May 1970. He served two tours in Vietnam and participated in Operation Deep Channel. Since his release from active duty, Mr. Howard has pursued independent writing and nature photography, and is working with Area Cooperative Educational Services in Hamden, Connecticut.