EBRP Outfall Pipelines for
Central Wastewater Treatment Plant
SJB Group, LLC was contracted by the East Baton Rouge City/Parish to design a new outfall pipeline from their Central Wastewater Treatment Plant located on River Rd. approximately a mile south of the I-10 Bridge. SJB Group was also asked as originally part of the scope for this project to investigate the condition and assess and design the appropriate rehabilitation method to enable continued service of the existing 36” outfall pipeline currently in use at the plant. Since it is not possible to divert or shut-off the inflow of influent to the plant for a prolonged period, it will be necessary to construct the new pipeline and place it in service before investigation and rehabilitation of the existing 36” pipeline can be fully accomplished. SJB explored various options for relining or replacement of the existing line to determine the least cost alternative pipe upgrade. SJB also surveyed and developed site plan of the existing 36” line. However, City/Parish suspended further rehab investigations due to discharge permitting revisions. Total Construction Cost estimated to be around $2,186,982.00.
The design capacity for the new pipeline was for a total flow of 65 million gallons per day. The new pipeline will be required to connect to existing effluent piping at an appropriate location within the plant and must be routed up and over the top of the existing Mississippi River Levee. The capacity of the proposed pipeline required a thorough analysis and integration of several aspects of the effluent piping system. Primary concerns of the design involved minimum and peak flow and head conditions during both dry and wet weather flows. Other variables included the height of the pipeline over the levee, the effect of river stages and the existing effluent pump station pump capacities and the existing 36” effluent pipeline possibly contributing and not contributing to outflow.
SJB analyzed the existing pump station for its hydraulic capacity under the varying peak flow and head conditions to assess the potential for pump station modifications, i.e. new pumps and motors, wet well capacity and valve vault manifolding of discharge. The resulting design was for a proposed 48” pipeline which was found to handle in excess of 65 million gallons a day without requiring replacement or substantial modification to the existing effluent pump station. The importance and benefits of rehabbing the existing 36” pipeline were significant for two reasons. 1) The existing pipeline was originally installed beneath the levee and allowed gravity flow during low river stages which correlated to no power requirements. 2) Secondly, SJB’s analysis also showed that during high river stages, pumping through both pipelines actually lowers the HP requirements and thus provides a power savings when pumping is required.
Additional aspects of the project design performed by SJB, included the design of an effluent flow meter and sampling system for continuous monitoring of both pressurized and gravity flow situations. There was also a significant level of coordination with the US Army Corps of Engineers and the Pontchartrain Levee District regarding the levee crossing, structural support systems and the outfall location and pipeline anchoring methods within the Mississippi River Bank areas.
- Pump Station Hydraulics (Wide Flow Range)
- Pipeline Hydraulics
- Pipeline Construction Economics – Trenchless vs. Open Cut
*This project represents a difficult hydraulic balance of varying peak flow and head conditions of the inlet and outlet of one pump station which discharges into “2” effluent lines during varying river stages. The pointed objective of design was to minimize power consumption during effluent discharge and save energy costs.