'Golden Gate' bridges strategic Afghan crossing
January 9, 2013
BAGRAM AIRFIELD, Afghanistan (Jan. 9, 2013) -- As NATO forces work toward bridging the gap from military operations to a self-sufficient Afghanistan, Army, Navy and Marine engineers of Joint Task Force Empire took the mission literally as they conducted Operation Golden Gate near Sangin, Helmand province, Afghanistan, through the months of November and December.
Golden Gate was a Regional Command-Southwest, or RC-SW, combined-joint engineering mission to construct a bridge complex spanning the Helmand River in southwest Afghanistan. The operation design was to improve mobility at the Sabit Qadam Flood Plain Crossing across the Helmand River. This strategic crossing links the Sangin, Musa Qa'lah and Now Zad districts close to Forward Operating Base Sabit Qadam (Jackson).
The mission carried strong strategic importance for coalition and Afghan National Security Forces, or ANSF, as well as the local Afghan population. It also carried historical and inherent natural challenges. The waterways are highly unpredictable, as the shoals (intermediate land masses) and surrounding areas typically flood from January through May.
"The research, concept development and engineering design surrounding the crossing of the Helmand River was enormously difficult, especially conducting this phase of the operation from a combat zone with minimal resources," explained Maj. Michael J. Hults, P.E., Regional Command-Southwest/West, or RC-SW/W, coordination cell officer in charge and Operation Golden Gate mission commander. "The Helmand is considered a braided river due to the network of adjacent channels, shoals, sandbars and rapids. Braided rivers are known for having erratic hydrologic activity and a dynamic topography which makes predicting either component extremely difficult. Further, any added man-made feature will ultimately have effects that cannot be readily forecasted."
"Our specific scenario leads to a crossing point that is furthermore a floodplain during the months of March through May when the Kajaki Reservoir swells from the melting of the surrounding mountain's snowpack," Hults continued. "The river levels can fluctuate by as much as eight feet during these flood periods. How do you construct a year-round expeditionary crossing point for both military and civilian traffic through, over or on top of a floodplain that is highly unpredictable, all the while trying not to negatively impact the local populace? Also, add to this scarce and subpar construction materials, a small budget and the fact that it will be constructed in a combat zone. Now, that's a challenge."
Hults said the solution began digitally by developing a virtual river model through software that uses empirical data and complex algorithms to predict the hydraulic events and subsequent outcomes.
"The way it was actually solved here was to have the RC-SW/W coordination cell design around agreed upon assumptions, available materials, time constraints and the various constructing unit's assets and abilities," said Hults. "Further, the cell identified and evaluated different risk factors and developed engineering solutions that could be implemented to mitigate the potential negative outcomes to a point where the risk was acceptable."
"Another challenge to this mission was the highly kinetic project site and the diminished battle space owner personnel. The [Marines] experienced a huge drawdown of infantry personnel during the recent surge recovery," Hults recalled as he described the many security aspects involved in a project of this scale. "It took a combined joint effort to keep the constructing units safe and secure. Even with the numerous entities coming together, the battle space owner still felt the pinch of thinning personnel resources due to the requirements of this mission."
Coordinating with the local contractors for material delivery was another hurdle to overcome. The project required crushed stone for soil stabilization and 60 concrete box culverts for hydraulic pressure relief along the elevated causeway. The contractors were hired, but required security and, were susceptible to delays due to route clearance requirements along the roads to the site. Additionally, military dump trucks delivered approximately 1,700 tons of riprap from Camp Leatherneck to the project site.
"Riprap is large broken concrete or boulders used to shield shorelines, abutments and levees to prevent scouring and erosion from flowing water," Hults elaborated. "The riprap available at Leatherneck was plentiful and consisted of large chunks of concrete from an old air strip. Without the proper amount and type of riprap emplaced on the bridge complex, the structure would have surely failed during the first flood season."
The flood season caused major problems with past projects at the site. Two previous bridging operations were beat back by the elevated water levels of the flood plain. Originally, a 12-bay medium girder bridge was constructed in the area for seasonal crossing in August 2010. These bridges can cover a 31-meter gap. A constructed earthen shoal ramp decreased the original gap to 25 meters.
The high river level forced the removal of the MGB the following January. A second attempt constructed another earthen shoal ramp, decreasing the gap to 28 meters and emplaced an MGB in October 2011. The high river level again forced an emergency bridge removal in March 2012. The repeated earthwork had caused the river to scour the shoal and increased the gap width to 50 meters.
"Each time this earthwork was introduced into the river, it drastically changed the topography. During the flood season after the 2010 MGB emplacement, the river cut through both earthen piers," Hults explained.
Riprap was added to the west side earthen pier in preparation for the following crossing season.
"This caused the raging river to redirect the flow until it not only erased the east side pier, it scoured approximately 20 meters of the hard pack shoal, therefore increasing the main river channel width," he said.
The Marine 8th Engineer Support Battalion conducted a recon of the site in June 2012 and determined an MGB could no longer span the gap. Additionally, the shoal was too severely scoured to emplace another earthen ramp. Combined recon teams revisited the site in July, August and September. A final survey in December was used to develop the "as-built" drawings.
The final solution consisted of two 17-bay Acrow bridges with a 300-meter interconnecting elevated causeway system. After providing a full design package, Joint Task Force Empire was tasked with the development and overseeing the construction of the project.
Regional Combat Team 7 secured the floodplain site as the 12th Georgian Battalion and Afghan National Security Forces conducted security on the east side of the river. Naval Mobile Construction Battalion 133, Task Force Anchor and the 12th Georgian Battalion secured the immediate project site. The 507th Engineer Battalion, Task Force Warhammer, provided route clearance patrols in the area as constant aerial over watch was maintained.
Through the efforts of the 2nd Battalion, 7th Marines, Afghan awareness of the project was increased with meetings with district governors and various ANSF officials as well as informative engagements with the local populace about project status and benefits. Afghan National Army escorts coordinated with the Marines to ensure delivery of building supplies for the project.
Task Force Anchor took the onsite lead on the bridge complex construction. The Seabees modified the existing pier by both increasing the elevation and width. They constructed levee systems and bridge abutments and formed the elevated causeway with crushed stone and local fill. Finally, they compacted, shaped and graded the bridge complex. Box culverts were installed within the elevated causeway. Riprap hauled by the ANA 2nd Battalion, 215th Brigade engineers was emplaced along the levees, bridge abutments, causeway and around the culverts.
Engineers worked 24 hours a day for 50 days straight on rotating 12-hour shifts under increasingly harsh winter conditions, with a steady diet of heater meals, long convoys to and from the site, and a daunting task ahead. The engineers of Golden Gate faced the challenge.
"The morale was the lowest in the beginning of the project when the extensiveness of the construction seemed insurmountable," Hults recalled. "Once the Seabees started to extensively change the landscape of the floodplain through their relentless efforts, morale continually improved until culminating with mission completion."
"Morale was very high," agreed Sgt. 1st Class Jason Armano, 411th Engineer Brigade chief bridging noncommissioned officer. "They were eager to get the job done. They worked 12-hour shifts. The night crew had it the hardest. The temperature at night was below freezing making it difficult to work in. Construction went as smoothly as any construction project goes. It had its issues and hurdles that any construction project needs to overcome, but the Army, Marines and Seabees worked through it to get the mission accomplished."
Members of Joint Task Force Empire, Task Force Warhammer and the 132nd Multirole Bridge Company installed the first Acrow bridge Nov. 22-24, on the Sangin side of the Helmand River. The bridge was 170 feet long and 14 feet wide with the capability to span a 150 foot gap. It will support normal one-way traffic.
The river can rise 10 feet before causing the need to remove the bridge. A second, similar bridge was then installed Dec. 7-13, at the Musa Qa'lah side of the river. The river level can rise nine feet before the bridge would need to be removed.
"This was our first really big bridge build in country," Sgt. Matthew Coleman, squad leader, 2nd Platoon, 132nd MRBC. "What really made the difference were the Soldiers out there doing the work. They were the ones who made it happen. They worked hard. They didn't complain. They were out there ready to go. We came together as a team."
The ANA 215th Brigade soldiers provided project site security including vehicular checkpoints, ferry station checkpoints, local contractor site security and interpreter support. The ANA leadership provided the local populace project-related information keeping a constant communication line open, further garnering strong support. Afghan Uniformed Police assisted with ferry checkpoints, security support and traffic control.
A contingency of Seabees will remain on Sabit Qadam to monitor the bridge complex and provide maintenance and emergency repair support, as they transition the mission to the 215th ANA engineers. Members of JTF Empire will continue to regularly visit the site to verify bridge integrity and provide maintenance support. During the flood season (January-April), data will be collected to provide RC-SW recommendations for any site upgrades.
The mission's result is greatly improved freedom of movement for coalition members, ANSF and the surrounding Afghan population which had become dependent on lengthy alternate routes or a limited and costly ferry system.
"The local population had to use a crude ferry system to get their vehicles, livestock and themselves across the area," explained Armano. "The ferries only operated during daylight hours. Now with the levee system and the two bridges installed they can cross the area freely."
"A more accessible and quicker crossing point will save logistic, engineer and security convoys valuable time, especially when bases are few and far between and the distances required to travel grows. It will benefit the military base demilitarization process. " added Hults. "The locals travel back and forth across the river to bring their livestock and goods to the different bazaars. Prior to the bridge, the locals relied on a ferry system as a paid service. The ferry process was also slow and unreliable. "
The meticulously planned and cooperatively executed mission has its biggest challenge waiting at the end of winter with the quickly approaching flood season. The engineers are steadfast in their confidence of the new crossing, as well as its lasting effect.
"The mission was incredibly successful as witnessed by the construction of an impressive bridge complex within time and budget and, the extremely positive atmospherics of the local population. From the standpoint of the local populace, ANSF, coalition forces and the engineering community, this was a huge success," stated Hults. "For the first time since we operated in the Helmand province, It brings year-round freedom of movement while, providing a quality of life improvement for the locals. It strengthens security, commerce and prosperity for the local population."