Tetra Tech to Rebuild New Orleans Floodwall and Levees
Tetra Tech EC in Norcross, GA won a $33.3 million, 18-month firm-fixed-price contract to build a hurricane risk reduction floodwall and five floodgates in the Lake Ponchartrain area of New Orleans, LA.
Under the contract, Tetra-Tech EC will demolish and rebuild a floodwall and gates, drive piling, build earthwork to upgrade levees that reach from the 17th Street Canal to Topaz Street along the lakefront, and upgrade roadwork and utility installations. Bids were solicited on the web with 4 bids received by the US Army Corps of Engineers’ Hurricane Protection Office in New Orleans (W912P8-09-C-0077).
Hurricane Katrina, which hit New Orleans in 2005, had a major impact on Lake Ponchartrain…
Lake Pontchartrain is a 630-square-mile shallow, brackish lagoon, with the city of New Orleans located along its southern shore.
According to a US Environment Protection Agency report [PDF], Lake Ponchartrain suffered dual assaults from Hurricane Katrina, a category 3 storm that hit New Orleans on Aug 29/05, with the eyewall passing along the eastern edge of the lake:
“Not only was Lake Pontchartrain’s delicate ecosystem subjected to nature’s fury–Katrina packed 135-mi/hour (217-km/hour) winds and a 20-30-ft (6-9-m) storm surge–the lake also faced an additional challenge by becoming the primary dumping ground for the flood waters that lingered throughout New Orleans during the 3-week period following Katrina.
New Orleans and the surrounding area are situated in a bowllike depression that lies typically 4-12 ft (1.3-3.7 m) below sea level. A network of levees and seawalls protect the city from nominal flooding, and an intricate system of large pumps evacuates accumulated rainfall from even normal storm events. The protective levees held during the initial landfall of Katrina; however, after 12-24 hours of continuous stress from the elevated water level, breaches occurred at several locations, most dramatically at the Metairie Outfall Canal (popularly known as the 17th Street Canal) and the Inner Harbor Navigation Canal (popularly known as the Industrial Canal).
The storm-driven water rapidly poured through the breaches, filling the natural basin of Orleans Parish and adjacent St. Bernard Parish with resultant flood waters that reached heights of 4-12 ft (1.2-3.7 m). While the pumping system was being repaired, these areas remained flooded for up to 2 weeks. The city’s sewage, stores of industrial and agricultural chemicals, petrochemicals, medical wastes, pharmaceuticals, food stocks, and even the remains of humans and domestic pets were all enveloped in the stagnant water, creating a cesspool of biological and chemical contaminants.
When the pumps were finally reactivated, the bulk of contaminated water from the city was jettisoned for many days directly into the southern portion of Lake Pontchartrain with a discharge estimated at 2-3 percent of the volume of the lake, or approximately 30-50 billion gallons (100-200 billion liters).”