Rainbow approves contract to install Morro Reservoir tank mixing system

The Rainbow Municipal Water District approved a contract to install a reservoir mixing system in the Morro Reservoir.

Helene Brazier did not participate in the Sept. 22 board meeting, when the other four board members gave support to the contract with CPC Systems Inc. The contract will be for $232,998 and CPC Systems, which is based in Irwindale, will install nine Kasco mixers with an option to install three more Kasco mixers.

“It’s just another system that’s going to help maintain and improve water quality in one of our reservoirs,” Tom Kennedy, Rainbow general manager, said.

Rainbow responded to changes in state and federal law by installing covers on the district’s three open reservoirs between 2010 and 2012. The Morro Reservoir is the largest of those three with a capacity of 150 million gallons, and during the design process Rainbow staff determined that the chlorine management system needed to be upgraded to allow for the formation of chloramines in the water leaving the reservoir. Chloramines slow the creation of disinfection byproducts which are regulated by the state.

After the new system was put into operation Rainbow staff could not easily achieve a stable chloramine residual with the installed equipment. Various potential solutions were tried but did not produce ideal results.

The system used an in conduit mixing system which has a short lay length of pipe for the chloramine mixing to take place, and the flow rates out of the reservoir are significantly variable. The control system relied on readings from an analyzer which can only produce an accurate read approximately once every five minutes.

“In any water storage facility, you want to maintain your water quality. One way we do that is cycle our tanks up and down,” Robert Gutierrez, Rainbow operations manager, said. “If you stir it, you keep it fairly fresh.”

Changes in temperature and water quality can lead to mixing deficiencies. Cooler and denser water will settle to the bottom of the reservoir and layers of water with a different chemistry will be present in the water column up to the top. The top layer can be significantly warmer than the bottom layer, especially with a black surface, and without mixing certain layers of water can age differently.

“All these factors contribute to the degradation of water quality,” Gutierrez said. “We need to have a good even temperature throughout the storage facility.”

The Kasco mixer will allow Rainbow to use existing rainfall removal pump power systems to feed power to the new mixers. The Kasco mixer will only require the use of three of the reservoir’s four cover pump electrical panels, so if the mixing with the nine mixers in insufficient three more can be installed in the fourth panel.

Joe Naiman can be reached by email at [email protected].