U.S. Army Engineers Take Proactive Approach to Levee Repair

Sliplining is one of the most used and trusted trenchless solutions for culvert rehab across a variety of infrastructure needs.Levees form a critical part of the United States infrastructure, as past flooding has demonstrated. When a levee is breached, it causes both personal and financial hardship. With 43 percent of residents living in a county with at least one levee, their upkeep is essential.

Of the 100,000 miles of levees in the United States, approximately 14,700 miles are designed, maintained and inspected by the United States Army Corps of Engineers (USACE) through the National Levee Database (NLD). The levees in the NLD average an age of 55 years or older and protect about 14 million people living and working behind them.

Keeping the nation’s estimated 100,000 miles of aging levee systems – in addition to a deteriorating, decades-old highway system – from failing, is a major undertaking for local and federal agencies.

It is no surprise that the levees maintained by the USACE represent a model of repair for the other 85 percent of levees in the United States that are locally owned, operated and maintained. The maintenance of USACE levees is held to rigorous standards as a primary protection to citizens and property in the event of a natural disaster — and as a standard by which locally-maintained levee system repairs are measured.

“Many of our flood control structures and pipes are 40 to 50 years old and they are exceeding their useful life,” said USACE engineer Neal Lewis. “We are lining (drainage) pipes in an effort to extend the life cycles of our existing structures.”

In many cases, the corrugated metal pipes (CMPs) within the levee systems are corroded and rapidly deteriorating. Deteriorated drainage pipes can lead to seepage through the levee, pipe collapse and a potential breach of the levee system.

“CMPs will rust over time,” said Lewis. “Coatings applied to protect them when they were constructed deteriorate, leaving the metal exposed to the environment. Storm water runoff in agricultural areas tends to be more corrosive, which shortens the lifespan of CMPs.”

And like aging levee culverts, corrugated metal culverts built 50 years ago with the U.S. Highway System are also deteriorating and in need of repair. Culverts are critical infrastructure under highways, roads, levees and dams; and addressing their structural integrity is a necessity.
Sliplining is one of the most used and trusted trenchless solutions for culvert rehab across a variety of infrastructure needs.

Culverts are critical infrastructure under highways, roads, levees and dams; and addressing their structural integrity is a necessity.By the time the culvert is identified as needing replacement, the embedment material around the host pipe is typically compromised. Compromised embedment reduces the structural integrity of the host pipe, which can ultimately result in a catastrophic failure.

“Snap-Tite HDPE liner pipe is one of the few products that is suitable for direct burial,” said Tim Tolliver, with Advanced Pipe Services, an engineering and technical services company serving the storm water, sanitary sewer and agricultural irrigation pipe industries. “Therefore, it is capable of carrying the load of the overburden and live loads.

“Snap-Tite provides both a structurally-sound solution and a hydraulic-efficient solution.”

Sliplining can be an added service for contractors that already perform infrastructure maintenance or it can be done by state and municipal crews with their own people and equipment. Tolliver has worked with the Department of Transportation engineers that are in charge of developing national standards for specifying materials for use in the highway infrastructure.

City, county and state agencies maintain the majority of the levees in the USACE Levee Rehabilitation and Inspection Program (RIP), which means they must source the repair work and pay for it. A very small percentage of levee systems critical to flood control are maintained and repaired by the Army Corps of Engineers.

But all levee systems in the RIP program — locally and federally managed — are regularly inspected by the USACE. And all levee systems in the RIP program must meet the standards set by them.

“The USACE is responsible for maintenance on certain levees in Louisiana and Mississippi, and they are repairing drainage pipes proactively to eliminate concerns over future pipe collapse,” said Stephen Boggess, director of the Snap-Tite division of ISCO Industries. “These repairs could be a template for future repairs done at the local level by local sponsors.”

Significant due diligence by local agencies, and the USACE, is required to determine the best method of repair. In the USACE’s Vicksburg, Miss., district, the Corps of Engineers selected Snap-Tite solid-wall HDPE pipe liner as their choice for critical levee repairs.

The primary alternative — digging up the pipe and replacing it — is costly and requires cutting into the levee, potentially affecting the long-term structural integrity of the entire system.

Often by the time a metal culvert is identified as needing replacement, the invert of the culvert has been perforated by corrosion. The corroded culvert will have exposed bedding and backfill material, and the bedding and backfill is washed out or eroded. This condition of corrosion and erosion reduces the hydraulic capacity below the original hydraulic design capacity of the original culvert.

HDPE culvert liner systems have a Manning’s coefficient, a formula used to determine flow calculation in open flow channels, approximately 50 percent less than the Manning’s coefficient of a corrugated metal pipe. This lower Manning’s coefficient for HDPE results in a significant increase in hydraulic capacity for the same size pipe. In the case of HDPE culverts, the inside diameter will be reduced by a minimum of the wall thickness of the re-liner pipe. The reduction in diameter is offset by the lower Manning’s coefficient.

The ability of the storm water to get into the culvert pipe is controlled by the inlet condition of the pipe. In the case of corrugated metal pipe, the ends are often projected ends that have an adverse effect on the amount of water that can enter.

A rehabilitated system using HDPE liner pipe will have a lower Manning’s coefficient and are often designed with a special inlet treatment that allows more water to get through the culvert pipe.

“A relined system, using an HDPE culvert lining pipe like Snap-Tite, is often more hydraulically efficient than the original design,” Tolliver said.

Snap-Tite can also be installed comparatively easily and inexpensively. The construction crew sliplines the existing CMP with Snap-Tite and grouts the liner fully in place, maintaining the structural integrity of the levee system. The new Snap-Tite liner maintains the same necessary hydraulic flow of the storm drainage into the river, with high-quality material and water-tight joints.

A unique feature of Snap-Tite is that it does not require fusion to join the HDPE pipe together. The ends of the Snap-Tite pipe are machined on each end. The machined male and female ends are then “snapped” together, piece-by-piece, on site using come-a-longs and chains.

“The Snap-Tite pipe was reviewed by another Corps district and was determined to be an acceptable product for lining pipes, likewise our district is using Snap-Tite,” Lewis said. “By lining CMPs, we hope to extend the life cycle of our existing structures. We will extend the life of our structures and reduce the cost of our backlog maintenance work.”

Melissa Moody is public relations coordinator at ISCO Industries, Louisville, Ky.
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