Missouri River L-575 Levee Repairs

Background

The L-575 Benton-Washington-McKissock-Buchanan-Atchison-Hamburg Levee System experienced significant damage after major flooding in the area. This led to seven breaches, along with substantial other damages, occurring throughout the levee system. APTIM was selected for the final repair contract to fully complete and restore the L-575 levee system to its pre-flood condition.

During the fall months of 2018, the lower Missouri River Basin experienced a very active weather pattern and above average rainfall, resulting in wet soil conditions heading into the winter season. During March 2019, as a result of the storm events, the mainstem Missouri River experienced high flows, picking up large inflows from unregulated tributaries in southern South Dakota, western Iowa, and eastern Nebraska. Record flows and stages were observed on the Missouri River south of Omaha in the proximity of and downstream of the confluence of the Platte River. As a result of this flood event, the L-575 levee system was overtopped, breached, and sustained significant flood damage that required repair. (Photos by USACE, Omaha District)

• Project Challenges
  • 43 miles of levee across 3 states
  • 5 levee districts and multiple sponsors
  • Identifying, investigating, and securing over 200 acres of borrow areas for backfill
• Project Requirements
  • Time critical emergency repairs
  • Levee repairs
  • Structural and breach repairs
  • New construction
  • Pump station inspection/repair
  • Heavy civil work
  • High-volume earth moving

Services Provided

APTIM is providing time-critical L-575 levee repairs for USACE Omaha District along the Missouri River to mitigate damage caused by record flooding. APTIM is working along the entire length of the 40-mile levee, performing general repairs, structures inspections, seepage well testing and replacement, and surfacing of the levee. Most of the civil earthwork is concentrated around the breach repairs and the construction of new features such as seepage berms. Other repairs include:

• Breach closure activities to include the repair of four major breaches with the placement of 1,295,000 CY of backfill, installation of 468,000 SF of sheet pile, and placement of 33,000 tons of rip rap and other miscellanies slope protection measures
• Reconstruction of the levee crests and slopes with 145,000 CY of cohesive material
• Installation of 55,000 tons of levee surfacing aggregate
• Repair of riverside scours with 150,000 CY of cohesive material
• Repair of seepage berms with 850,000 CY of sand
• Relief well-pump testing, abandonment and replacement for 195 wells
• Drainage structure inspection, cleanout, and repairs of 32 drainage structures
• Pump station inspections and repairs for six pump stations
• Sediment and debris removal on the levee slopes, crest, and berms
• Rehabilitation and reconstruction of 70,000 feet of levee toe drains
• Final site restoration

Accomplishments

As of February 29, 2020, the entire L-575 levee system has been returned to full height, which is a critical milestone in levee repairs. The team will continue with repair activities to restore the levee system to its pre-flood condition.

APTIM surpassed project expectations by closing Breach G ahead of schedule to beat a milestone date of three months from notice to proceed (NTP). This extremely challenging task involved moving over 1-million CY of material and installing more than one mile of sheet pile over 49 days in winter conditions to provide 100-year-level flood protection for surrounding communities. To-date, APTIM has moved over 3-million CY of material, installed over 8,200 feet and 400,000 sf of sheet pile, and received and replaced 78,000 tons of aggregate and Rip Rap. APTIM has worked over 180,000 manhours with zero incidents.

Learn more about APTIM’s Flood Control Engineering and Emergency Management services.