For years, infiltration washed substrate into a double-barrel 48-inch reinforced concrete culvert under Duval Road in Starke, Fla., causing sinkholes. The road feeds the main training areas of the Camp Blanding Joint Training Center.

The Florida Army National Guard feared damage to heavy military equipment and the trailers transporting it when the wheels dropped into the sinkholes. After every heavy rain, forestry workers filled them in and resurfaced the road. Finally admitting defeat, the guard called Engineered Lining Systems, a Jacksonville-based company with a specialty in cured-in-place pipe and structure restoration.

"When we investigated, every joint in the 125-foot-long pipes was gone," says project manager Danny Knight. "As a sinkhole formed, it caused the section of pipe under it to fall a little and offset further. Even small rains flushed sand and debris into the barrels until they were half full."

Because Sulfur Creek trickled through the culvert, Knight chose the SAERTEX fiberglass-reinforced plastic lining system with two layers of foil sealing the epoxies inside the tube and protecting the environment. The liners also provided structural support. Third-party test results showed that they have a flexural modulus of 1.7 million psi and flexural strength of 36,000 psi with less than 0.5 percent shrinkage factor.

The creek became a raging river when Tropical Storm Debbie dropped 27 inches of rain in three days, then it rained every afternoon. "The most challenging aspects were dealing with the water in the creek and material in the barrels," says Knight. "There was so much of both, more than we ever anticipated."

Getting there

The culvert lay 25 feet below the road at the bottom of a steep wooded hill. The center's forestry division cleared trees and built roads to both sides of the culvert, but ELS crews cut more trees to enlarge the upstream work area. Using a Caterpillar 225 trackhoe and Bobcat skid-steer from Sunbelt Rentals, they dug upstream and downstream detention pits 20 feet in diameter and 15 feet deep in the middle of the creek. They used the spoil to fill in the creek to the culvert.

A Quiet Flow 6-inch diesel pump from Sunbelt Rentals dewatered the upstream pit. Workers ran the discharge hose through the inactive barrel to the downstream pit beyond the work zone. "Water running down a little ditch beside the upstream headwall wanted to enter the culvert, so we channeled it into a corrugated pipe discharging to the upstream pit," says Knight.

Before the crew left in the evening, they shut off the pump and allowed water to flow through both barrels, then pumped it down the next morning. Dewatering also lowered the groundwater level, stopping infiltration that was substantial enough to fill the barrels halfway.

Tricky and delicate

Standing on the downstream headwall, jetter/inspection technician Jody Wright used a tiger tail to protect the jet hose from scraping against the concrete as he cleaned the barrels with a C-Ray sewer nozzle from NozzTeq. Technician Josh Knowles operated the GapVax MC 1510 combination vacuum truck parked on Duval Road. Because Knowles was so far from the culvert, Wright signaled when to pull back on the hose or send it down the pipe. Technician Mikal Biegner assisted Wright when he couldn't see what was happening.

"The gaps between joints were so bad that every time Jody ran the jetter through a pipe, it pulled in more sand than he removed," says Knight. "We had to go low and slow, cleaning with 65 gpm/1,500 psi."

As the jetter dislodged material, the trackhoe operator scooped it out of the pipe and stockpiled it for the skid-steer operator, who transported it up the hill and packed it in washed out areas alongside the road.

Knight rejected the idea of pulling a pig through the barrels. "The joints were out of alignment in all four directions," he says. "If the pig caught on the 10 to 15 percent offsets, it would cause more damage." The team removed 30 cubic yards of sand and debris in three days.

Throughout the operation, two workers monitored the pump and dewatering operation. "Everything was muddy because of the rain," says Knight. "My truck became stuck repeatedly as I brought fuel for the pump, and the excavator had to pull me out."

Lining procedure

Overnight, infiltration washed a quarter of a cubic yard of sand into the barrels, which workers removed in the morning. Then the vacuum truck sucked up the puddles. "Water is a bad thing because we're using electricity and lights," says Knight.

The 12.5-mil liners, weighing 85 pounds per foot, arrived from the factory wetted out, slipped inside UV-protective gray foil sleeves, folded into light-proof crates, and shipped with a spool of 2 mm thick gliding foil. The trackhoe operator set the crates on concrete slabs left over from construction of the headwalls.

While some workers pulled the gliding foil into the pipe, others positioned the leading edges of the liner inward, inserted a pulling collar, and secured everything with a ratchet strap. They tied a 1.25-inch double-braid polyester/nylon rope to the collar, enabling the trackhoe operator and foreman Joey Vance to pull in the liner from across the road.

At this point, Knight erected a tent over the light-sensitive liner. "Sunlight hitting them will begin the curing process in seconds," he says. Workers cut the liner to length, inserted steel packers (cans) on either end, secured them with ratchet straps to seal the liner, then inflated it enough to insert the Double Core 10-foot-long UV light train.

Curing power

"The light train has eight 1,000-watt UV bulbs, four forward and four aft between the two sets of legs," says Knight. "It also has temperature sensors and a fixed camera on one end." Another camera attaches to the inside of the downstream packer.

Once workers pulled the train to the head of the liner, they replaced the can and inflated the liner. A computer controlled the speed of the train based on the liner's diameter and thickness. Curing took nine hours moving at less than 6 inches per minute.

Although the liners indented somewhat at the joints, the smooth interiors dramatically increased flows. Before leaving, the ELS crew filled in the detention pits, restored the creek, and graded areas roughed up by the equipment.