PROJECT DESCRIPTION
CTI provided engineering and construction services to USACE St. Louis District – Southern Residence District to excavate and repair collapsed CMP piping associated with a levee control structure. Following the repairs, slip-ling with 63-inch HDPE was completed. Scope of this project was to repair complete blockage on one of the two 72-inch CMP culverts. Mod 2 included the development of construction documents, construction sequence planning and material staging in anticipation of potential high water events, piping replacement, slip-lining, levee re-construction, site restoration, and project close-out documentation.
“CTI was issued the first task order in a series of levee slide repair contracts that utilized a new testing protocol. Being the first, they encountered a number of unexpected issues and conflicts with respect to the consistency of test results. CTI proactively sought out solutions to these conflicts that were ultimately utilized on successive contracts.”
Jeff Derrick, Area Engineer
Culverts on both the land and river sides of the gate structure were completely obstructed and needed excavation and repair. The amount of complete pipe obstruction, believed to be around 20 linear feet, was actually approximately 100 linear feet. In general, this repair process includes the following:
- Removal and stockpiling of topsoil.
- Excavation to a depth of 35 feet to access and remove two damaged 10-foot sections of CMP. Levee materials were stockpiled nearby for emergency use in the event of projected high water.
- Removal of over 100 linear feet of material completely filling the 72-inch CMP sections to remain in-place.
- Slip-lining over 580 feet of CMP with 63” HDPE.
- Reconstruction of the levee with stockpiled soils and compaction to 95% of the Standard Proctor maximum dry density.
- Restoration of the levee included topsoil placement, seeding, and fertilization.
PROJECT CHALLENGES
The amount of blockage in the culverts was found to be five times greater than expected. This blockage could potentially have caused the length of pipe replacement (and the project costs) to increase correspondingly. CTI’s field staff noticed that the obstructing materials could be removed from the pipe by water flow, and configured a coffer dam to route all water into the obstructed pipe, then worked inside the pipe to loosen the debris and facilitate its removal by the natural flow of water available at the site. Over 86 feet of completely obstructed pipe was cleared in two days with no impact to the project schedule.
Movement of the concrete gate structure had to be held to a minimum, with a specified tolerance of 0.021 feet of movement. Movement in excess of the specified value was observed. CTI’s engineers and field crew worked closely with SLD to evaluate the cause and significance of the movement. It was resolved that the observed movement (0.031 feet) was acceptable and required careful monitoring. Quickly identifying and resolving this issue kept the project on schedule.
PROJECT HIGHLIGHTS:
- Excellent Construction Safety Record
- Self Performed 66 % of Work
- Two Culvert Repairs 35 feet Below the Levee Road
- 580 feet of HDPE slip-lining
- Maintained Project Schedule Despite Several Lost Work Days from High Water
- Encounter And Cleaned over five Times the Expected Amount Of Obstructed Pipe with No Schedule Impact
- Identified Movement of the Gate Well Structure, Proactively Identified the Significance of the Movement, and Maintained Project Schedule
- Excavation, Culvert Replacement, Backfilling, Soil Compaction Testing, and Quality Control
- Silt Fencing and Storm Water Protection
- Turf Establishment and Final Levee Road Construction
- Final Construction As-Built Drawings and Geotechnical Testing Documentation