Rainbow MWD adds Dentro De Lomas Pump Station to Hoch design contract

Joe Naiman

Village News Reporter

Last year, the Rainbow Municipal Water District board approved a professional services contract with Hoch Consulting to design the Hutton and Turner pump stations. On Aug. 30, the board amended the contract to add the Dentro De Lomas Pump Station to the work.

The 4-0 vote, with Miguel Gasca absent, authorized Rainbow general manager Tom Kennedy to execute a change order adding $299,061 to the original $166,149 amount and adding the scope of services necessary for the third pump station. The action also extends the end of the contract from June 30, 2022, to Feb. 24, 2023, and finds that the design portion of the project is not subject to California Environmental Quality Act review.

In January 2021, Hoch Consulting, which is headquartered in Oceanside, was awarded the Rainbow contract to design the Hutton and Turner pump stations. Both pump stations are along the San Diego County Water Authority's Second Aqueduct route just west of Interstate 15. The Hutton Pump Station is near the Old Highway 395 bridge north of West Lilac and the Turner Pump Station is south of Camino Del Rey.

The SDCWA annually shuts down portions of the Second Aqueduct for inspection and maintenance as does the Metropolitan Water District of Southern California. The CWA takes over operation of the aqueduct from MWD approximately six miles south of the Riverside County border. During those shutdowns, Rainbow rents, installs, and operates temporary pump stations in up to four locations to supply water to the Hutton, Turner, and Gopher Canyon tanks. The temporary pump stations Rainbow rents create noise as well as expense.

The Robert A. Weese Filtration Plant is owned by the City of Oceanside and operated by Oceanside's Water Utilities Department but is physically located in the Rainbow service area off of Silverleaf Lane in the Gopher Canyon area. In August 2017, the Rainbow board authorized district staff to proceed with the design for an interconnection to the Weese Filtration Plant. The eventual design contract included the replacement of the pumps which supply the Hutton and Turner tanks.

Four of Rainbow's eight connections to the aqueduct are from MWD rather than from the CWA, and during the design of the interconnection project, Rainbow decided that regular use of the pumps to move water from the Morro Zone to the south zones would allow Rainbow to save money (currently approximately $173 per acre-foot) by using the MWD connections even when the CWA portion of the aqueduct is operational.

The temporary pumps also require fueling, so permanent pump stations will also reduce the risk of a fuel leak or spill.

The Hoch design work includes general site layout, structural foundation, connection details, integration with Rainbow's supervisory control and data acquisition (SCADA) system, and site valving.

During the design of the two pump stations, the project team determined that the design criteria did not include all information needed to model the demands in Rainbow’s southern zone. Hoch and Rainbow staff proposed a macro approach to Rainbow’s comprehensive hydraulic model to determine the sizing of the Hutton and Turner pump stations. Due to Turner Pump Station infrastructure limitations, it was proposed to shrink the Turner Zone, expand the Hutton Zone, and create the Dentro De Lomas Pump Station.

The Dentro De Lomas Pump Station had already been envisioned as a component of the Bonsall Oaks development (that is the current name of the project; it was called the Polo Club in 1993 when the San Diego County Board of Supervisors approved the tentative map), and the water and sewer infrastructure to be added by the project includes a pump station.

“This one we just need to design to be ready to go,” Kennedy said.