Background

The City of Holtville, through its Public Works Department, is responsible for providing wastewater collection and treatment services. In 2012, wastewater collection coverage was estimated at more than 98% through 1,369 sewer residential and commercial connections. All of the collected wastewater is treated at the city’s wastewater plant, which has a treatment capacity of 0.85 million gallon a day (mgd).

The existing wastewater gravity main conveys 100% of the collected wastewater 3.2 miles from the city to the Holtville Wastewater Treatment Plant. The pipeline was constructed approximately 84 years ago using short segments of vitrified clay pipe requiring numerous
mortared joints, which due to aging have cracked allowing water infiltration from nearby canals and agricultural fields. Segments of the pipeline slope are flat resulting in inadequate flow velocities, the buildup of solids and corrosive anaerobic conditions. Offsets along the length of the pipeline from settlement and seismic activity also impede wastewater flow and contribute to anaerobic conditions. As a result, most of the manholes along the length of the pipeline are extremely deteriorated and susceptible to collapse posing a safety hazard to
vehicles and pedestrians.

In addition to replacing the deteriorated wastewater main, the City is also proposing to expand its wastewater collection system to 23 homes within two neighborhood blocks. This project will replace undersized and unreliable sanitary sewer collection lines and residential connections, as well as failing on-site treatment systems, eliminating wastewater overflows that have been reported in the project area.

Description

The City proposes improving its wastewater collection and conveyance
system through two projects:

Wastewater main replacement
This project entails construction of an 18-inch PVC wastewater main extending 18,100 lineal feet.

Wastewater collection expansion
The main components of the project include the construction of two 600-foot, 8-inch PVC sewer lines, installation of 23 residential.

Benefits

Both projects will reduce the potential for groundwater and surface water contamination from sewage spills and leaks, thus providing a cleaner healthier environment for local residents. The second project will also provide first-time sewer service to 23 households, collecting an
estimated 8,100 gallons a day of wastewater for treatment.

connections, and the abandonment of the septic systems in the area