Background

The groundwater table in the project area is located at a depth of about five feet and is comprised of saline water. The sewer lines are vitrified clay pipes originally installed on extremely steep inclines and at profound depths, well below the water table.

It is suspected that the pipelines have cracked allowing water from the Salton Sea to enter the collection system, thereby increasing the total dissolved solids (TDS) concentration in the entire system. The treatment process does not remove salts from the wastewater, so high TDS concentrations are percolating into the ground adjacent to the treatment
plant, with the latent risk of contaminating the groundwater.

Description

To address this problem, the District is undertaking a project to replace portions of the existing wastewater collection system with high-density polyethylene (HDPE) pipes, which are more flexible than vitrified clay and less likely to crack from normal ground settlement pressures. Since the new lines will be installed at flatter slopes and shallower depths, the
pumping infrastructure will also be simplified, which will significantly reduce maintenance requirements for the district.

Major project components include:

• Replacing about 8,100 ft. of sewer lines along the peninsulas
• Installing an 18” collector along 3,200 ft. of Thomas Avenue
• Plugging and abandoning the force main from Lift Station No. 6
  and constructing a 400 ft gravity line between the lift station and
  the Thomas Avenue collector.
• Upgrading lift stations No. 2 and No.6
• Eliminating two submersible pumps

Benefits

The Project will improve the quality of the groundwater near the treatment plant by reducing the TDS concentrations of the effluent, which will help protect the region’s water table. In addition, simplifying the pumping system will reduce operating and maintenance costs for
Desert Shores residents. These improvements will ensure that effluent discharges from the treatment plant comply with California quality
requirements.