Project Overview
New Orleans, one of America’s most iconic cities, is vulnerable to flooding from powerful hurricanes. PND designed critical deep temporary cofferdams and permanent canal walls to protect the city as part of the Permanent Canal Closures & Pumps (PCCP) Project, the first major design-build project solicitation for the U.S. Army Corps of Engineers (USACE) New Orleans District. The PCCP project was the capstone of a broad USACE program to protect the city from a 100-year hurricane flood surge. The project included pump stations, variable-position flood gates, and barrier walls. In the event of a hurricane, the system shields the city from high water levels in Lake Pontchartrain and discharges floodwaters into the lake via pump stations on three flood drainage canals.
PND contributed final design and engineering support for construction of temporary OPEN CELL SHEET PILE™ (OCSP™) cofferdams, classic braced cofferdams, and permanent OPEN CELL™ retaining wall structures at the three canal sites. PND’s proprietary OCSP™ system efficiently retained in-situ soft soils in the deep excavations at each pump station site and sealed the cofferdam against ominous extremes of water pressure. While the cofferdams in which the impressive permanent pump stations were constructed were short-lived, they were vital for enabling the design-builder to bid, win, and successfully deliver this major infrastructure project to USACE for the civil defense of New Orleans from storms and flooding.
Our Role
- Construction Engineering: provided critical guidance on configuration, detailing, specifications, quantity documentation, and construction methods to install temporary cofferdams and permanent retaining walls at three large pump stations
- Geotechnical Engineering: prepared all necessary geotechnical calculations for design of the temporary cofferdam structure and the permanent canal lining walls. PND’s analysis heavily focused on confirming excavation stability to the current standard of care and preparing all calculations to withstand detailed scrutiny by subject matter experts
- Structural Engineering: provided structural design for nine cofferdams―a deep OCSP™ system for the pump station; a classic braced cofferdam for the shallower-founded bypass structure; and an interstitial cofferdam between the pump station and bypass structure―under the imposed geotechnical loads established for the soft ground at the sites
- OPEN CELL SHEET PILE: designed a temporary OCSP cofferdam to facilitate quick excavation and three permanent OCSP retaining wall structures to protect New Orleans from a 100-year flood
Critical Infrastructure Strengthens Hurricane Protection System
The pump stations were the final components of the USACE hurricane protection system for New Orleans. The temporary cofferdams and permanent retaining walls were required to construct the three large pump stations along Lake Pontchartrain’s shoreline. PND’s permanent OCSP™ retaining walls flank the pump station approaches to support the canal banks and allow for a water drawdown of 24 feet during future pumping operations, safeguarding the city by providing a much higher exposed face than traditional braced walls used in the soft grounds of south Louisiana.
Additionally, the temporary OCSP™ cofferdam is a unique design to PND that allows the cofferdam to be fully excavated without the need for interior braces, which slow down and interfere with construction. PND’s pump station cofferdams are the deepest shored excavations ever constructed under USACE contract in Louisiana. The OCSP™ cofferdam structures were featured in 2016 editions of Engineering News-Record and PileDriver magazines, while the PCCP project was showcased on HISTORY Project Impossible in 2018 and Civil Engineering magazine in 2019.
Pump Stations
now provide New Orleans with flood protection
Cubic Feet of Water per Second
can be pumped from the city in a flooding event
Tons
capacity within 5 feet of each OCSP™ cofferdam’s edge
