Project Spotlight – Effluent Force Main Design

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Effluent Force Main

The Challenge

EARTHRES prepared the detailed design, permit application documents and construction bid packages for the construction of leachate pretreatment components and a 5-mile long effluent force main for the conveyance of pre-treated leachate from a new equalization/storage tank to the pump station. The force main would require construction through ecologically sensitive areas and wetlands.   Due to the remote location of the majority of the pipeline, a remote telemetry system via a PLC would need to be installed.  EARTHRES would have to prepare a Basis of Design report for the project which analyzed several design alternatives from a technical and capital/operating cost perspective.

Project

Effluent Force Main Design

Location

Confidential

The Solution

The following permit applications were prepared and successfully obtained: State DEP Solid Waste (two applications – one for pretreatment components and one for the force main), State DEP Water Quality Part II,  HOP, E&S Control Plan, and wetlands disturbance with vernal habitat construction. EARTHRES prepared three construction bid packages for construction of the effluent force main, the landfill leachate force main, and wetland/vernal habitat construction.

A fourth bid package was prepared for construction of the leachate pre-treatment components (combined leachate valve chamber, grit chamber, and grit chamber pump station) and the effluent force main support components (effluent pump house, new Tank 3 with an aeration system, and force main remote monitoring and telemetry system). The bid packages included plans, profiles, construction details, technical specifications, contract documents, unit price bid form, site safety requirements and relevant construction permit attachments (E&S Plan, Highway Occupancy Permits). The bid documents included construction of the following:

  1. Wastewater grit chamber and combined leachate valve chamber design;
  2. Leachate force main (~2 mile long raw leachate force main with secondary containment);
  3. Post-Sequencing Batch Reactor (SBR) wet well design evaluation, valve vault design, and Post-SBR (pre-effluent force main) equalization tank and aeration system design; and
  4. Five-mile long effluent force main (with secondary containment) from the landfill to the municipal authority pumping station which included leak detection and pressure monitoring components connected to a master PLC control system via solar powered and line powered radio telemetry.

The effluent pipeline path required construction through wetlands and ecologically sensitive areas. In order to reduce client liability and satisfy State DEP concerns, the design included dual-contained HDPE piping, primary conveyance piping equipped with pressure sensors, and valve station/air release vaults equipped with liquid detection sensors. Due to the remote location of much of the pipeline, monitoring equipment is powered by local weatherproof and secure equipment panels equipped with solar panels. Repeater stations were strategically located in areas with existing infrastructure and powered via overhead or underground service. A master radio located at the landfill pump station monitors the remote telemetry system via a PLC.

EARTHRES developed a logic structure that polls the system every few seconds for pre-set high/low pipeline pressure and vault liquid detection. Any variation outside the pre-set parameters results in a pumping system shutdown and automated alarm to the leachate treatment plant operators. The same PLC system also allows the operators to select the flow rate and total daily flow to the publically operated treatment works (POTW). Based on the operator input, the system operates continuously with pipeline “surge” cycles at higher scour velocity, or in batch cycles during low flow conditions. EARTHRES assisted in the bid evaluation process, evaluated potential cost-reduction measures, performed submittal review, and provided engineering assistance throughout construction.

The Results

Designed and constructed an effluent force main through wetland and ecologically sensitive areas.  The force main will remain in compliance with PLC system with logic structure set to poll the system for pressure and leak detection.

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