Cross Connection Removal Project

Portions of the City of Modesto’s storm runoff are diverted into the sanitary sewer system through what are known as cross connections. In most cases, a cross pipe from a surface inlet or from a rock well directly connects to a sewer manhole. During heavy storm events these cross connections overburden the sewer system, Increase the cost for the wastewater treatment plant to treat the storm water, and occasionally lead to sanitary sewer overflows (SSO’s). The 2007 City of Modesto Waste Water Master Plan (WWMP) proposed to remove the cross connections due to this increased burden and cost.

We start with an existing park such as Garrison park (Pictured)
The park is excavated to completely submerge the storm chambers
The storm chambers are installed and crushed rock is used to fill the voids
Pre-Treatment Devices are Installed to remove contaminents from the storm water
The storm chambers are covered with dirt and new sprinklers are installed
Grass is then placed to cover the excavated area
The baseball field was renovated and a basketball court was added
The final result is a pleasantly soft, green play area and reduced storm water run off

There are 54 known cross connections throughout the city. The first phase of cross connection removal was completed in November 2014 and was referred to as Phase 1 Garrison Park (pictured above). The project removed 3 cross connections and twenty failed rock wells in the Carver/Orangeburg area. Several hundred feet of storm drain piping were installed to convey storm water from an approximate 24-acre tributary area to nearby Garrison Park where the storm water is pre-treated and then stored in underground percolation chambers. Additional benefits of the project are the reduction of local street flooding, improved water quality, and ground water recharge.

The design of Phase 2 – Roosevelt Park was completed in Summer 2018. Construction began in Fall 2018 and will be completed in Summer 2019. With this phase, improvements to the City’s sewer system will be achieved by removing 6 existing storm to sewer cross connections that currently overburden the sanitary sewersystem during storm events. The removal of these cross connections not only provides significant benefits for the sanitary sewer system as a whole, but also directly implements much needed improvements to the Roosevelt Park neighborhood. Currently, this area relies on older rockwells to collect storm water but is not adequate to handle average to large storm events, resulting in street flooding.