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Sewerage System Upgrades
Upgrade Overview
The Sewerage and Water Board (S&WB) of New Orleans began a major rehabilitation and capacity upgrade of its aging sewage collection system in 1996, following a public hearing to obtain citizen input on the plan.
Like most of the nation's major metropolitan areas, New Orleans' underground water and sewer systems are at least 40 years old and, in many cases, up to 100 years old. Factors common to this area, such as unstable soil conditions and large numbers of tree roots, contribute to a higher-than-normal number of breaks and deterioration of the sewer pipes.
At the public meeting, the S&WB's staff and consultants provided details of the now $600 million multi-year program to the public, environmental, preservation and neighborhood groups, elected officials and the news media.
The SSERP, or the Sewer System Evaluation and Rehabilitation Program, was eventually incorporated into the consent decree the S&WB signed with the EPA in 1998. At that time, timetables and deadlines were established for the work in each district.
The S&WB selected Montgomery Watson Harza (MWH), a global leader in large capital program management, to serve as SSERP program manager. MWH's program management experience includes planning and management of design and construction of extensive sewer rehabilitation-related projects in Houston, Baton Rouge, Miami and San Francisco.
In addition, the S&WB sought out EPA Federal grants to support the program totaling approximately $100 million over 10 years. The $100 million has been authorized by Congress. To date the Sewerage and Water Board has received $38.8 million in Federal Funds.
Rebuilding New Orleans' Underground
Currently, the sewage collection system services an area of approximately 86 square miles and a population of approximately 497,000. It consists of over 1,600 miles of gravity collection and trunk sewers ranging in size from 8 inches to 84 inches in diameter and over 100 miles of force mains ranging in size from 6 inches to 72 inches in diameter. There are 83 pump stations which help convey wastewater to the City's two wastewater treatment plants, one on the East Bank and one on the West Bank (Algiers) of the Mississippi River with a combined capacity of 132 million gallons per day (mgd).
The SSERP program will rehabilitate this wastewater system using state-of-the-art trenchless and traditional methods. The trenchless methods allow for rehabilitation of buried pipe and manholes without the need for excavation and the disturbance to residents that it causes.
The project is divided into ten districts. Each year, one of these districts will undergo a system evaluation survey that will result in an estimated $12 to $47 million in sewer structural rehabilitation needs. This comprehensive study includes smoke and dyed water testing, flow and rainfall monitoring, manhole inspections and surveys, and closed circuit televising (CCTV) of approximately 35 percent of the system. Sonar technology is also employed to determine the condition of sewer lines that cannot be de-watered.
In fact, SSERP engineers developed a computerized decision model to automatically determine a cost-effective rehabilitation method from encoded CCTV data. Engineers record detail sewer data for each study area -- such as location, size and current conditions -- using a closed-circuit television recording device. That data is electronically transferred to the computer decision model, where algorithms determine efficient repair methods based on existing conditions and the S&WB's rehabilitation strategy. This process has helped reduce design time and costs so more dollars can be utilized for rehabilitation measures.
Early Efforts Completed On-time and Within Budget
So far, sewer evaluation surveys have been completed in the Lakeview and Gentilly districts located adjacent to Lake Pontchartrain, Uptown, Lower Ninth Ward, Carrollton, and in the Central Business District, Warehouse District and French Quarter (CBD/WD/FQ) areas. Survey efforts in the New Orleans East district were initiated in early 2003.
The Lakeview area district sewer structural rehabilitation was completed at the end of 2001. These efforts included manhole rehabilitation, gravity sewer pipe lining, excavated point repairs and replacement, resulting in the rehabilitation of some 2,000 manholes and over 163,000 feet of sewer line.
Marcia St. Martin, interim executive director of the Sewerage & Water Board, explained: "We've learned a lot during the rehabilitation of this first district. Our contractors and suppliers need to offer speed and versatility to support this massive job in the turnaround that we need to support the stringent EPA guidelines."
In addition to the Lakeview area, construction activity in the Central Business District/French Quarter district is well underway. Work in this area includes cleaning and televising over 300,000 feet of sewer line, rehabilitating some 650 manholes and nearly 70,000 feet of sewer line.
Contractors are rehabilitating aging sanitary sewer manholes through the addition of lightweight cementitious lining, replacing frames and covers, installing flexible corbel seals, and simply raising of covers to match adjacent ground levels. These adjustments are very extensive due to New Orleans' dynamic soil conditions.
D&O Contractors, Inc. of Kenner, Louisiana, was charged with rehabilitating nearly 1,200 of these manholes in the Lakeview area district, relying on lightweight cementitious liner to complete the job. SSERP engineers selected cementitious liners because the application and installation are effective, straightforward and relatively quick. The rehabilitation effort for another 800 manholes in the Lakeview district was completed by E.B. Feucht and Sons of Eunice, Louisiana.
Prior to the installation, each manhole is cleaned with a minimum 3500 pounds per square inch (psi) hot water pressure wash and steam. Next, the lining is applied through a spray process and troweled smooth. Then crews apply a flexible urethane coating to seal the lining on the wall to the metal casting. This seal allows expansion and contraction while remaining water tight within the manhole wall structure, which is stationary and expands at a different rate than the metal casting.
In terms of gravity sewer pipe rehabilitation, the job is much larger.
Crews from Boh Brothers Construction Co., LLC, of New Orleans, Insituform Technologies, Inc. of Hammond, Louisiana, and Fleming Construction Company of Metairie, Louisiana, as of May 2003, have completed cured-in-place manhole-to-manhole lining of over 200,000 lineal feet of existing sanitary sewer (8-inch to 30-inch diameter) as part of the contracts awarded through the SSERP program.
The SSERP projects began in May 1999 and, according to contract guidelines, required the teams to meet interim milestones during the project timeline. Failure to complete the designated rehabilitation or reconstruction activities may have resulted in significant monetary penalties. All contracts for sewer rehabilitation performed under the SSERP have met all required milestones resulting in no penalties for non-compliance. The majority of the effort is focused on trenchless pipeline reconstruction but also includes excavated point repairs, the rehabilitation of service laterals, site video work and the conventional excavated replacement.
Much of the trenchless pipeline reconstruction will be accomplished using a polyester felt liner impregnated with resin and inverted into the damaged pipe with water, then cured in place with hot water to the shape of the host pipe. During the installation process, the resin is forced into cracks, joints and other irregularities of the host pipe to form a mechanical lock between the host pipe and the liner that holds them firmly in place. After the new pipe has cured, service lateral lines will be reopened with a remote-controlled robotic cutter.
Additional contracts for the rehabilitation of the remaining 40,000 lineal feet of existing sewers to be rehabilitated in the Central Business District will be completed by the end of 2005.
Sewer design and structural rehabilitation activities in the Gentilly area began in July 2001. The rehabilitation work in this area includes rehabilitating some 1,600 manholes and 163,000 feet of sewer line. The contracts are being performed by D&O Contractors, Boh Brothers Construction, and Wallace C. Drennan of New Orleans, Louisiana, and Roland Pugh Construction Birmingham, Alabama.
The Sewer Rehabilitation Future
Surveys in the remaining districts will be conducted at a rate of one per year, with the final survey scheduled for completion in 2006. In addition, planning is ongoing for numerous capacity related projects, which will provide for improved hydraulic capacity to pump stations and force mains. Actual construction and remedial work in the nine districts on the East Bank must be completed by 2010, according to consent decree requirements.
Thus far, the Sewerage and Water Board and its contractors have met the tight consent decree timeline for the initial phases of the project--most ahead of schedule. In addition, the traffic delays along several major avenues were cut in half by the use of trenchless technology.
At this time, discussions of future funding options are underway by the S&WB, its financial advisors and bond counsel. The future of SSERP, naturally, depends on the availability of funds to complete the projects and complete them in accordance with EPA deadlines to avoid large fines of up to $15,000 per day.
The S&WB has kept the public informed of the SSERP projects through billing inserts, its website, news releases, media briefings, public hearings and meetings, special neighborhood meetings and participation in meetings scheduled by the Mayor or councilpersons.
Because of the high visibility of smoke and dyed water testing and televising of the sewer lines, the S&WB schedules special demonstrations of the tests prior to work beginning. Invited to the demonstrations are area residents, neighborhood and civic associations, environmental groups, elected officials and the media.
To date, over $93 million has been expended for work identified under the SSERP. In addition, the following inspection and rehabilitation efforts have been completed so far:
* 5.1 million feet of sanitary sewer pipe have been inspected;
* Over 291,000 feet of sewer pipe have been rehabilitated;
* Over 19,200 sewer manholes have been inspected; and
* Over 2,600 sewer manholes have been rehabilitated.