The City of San Diego’s Public Utilities Department last week took a major step toward completing an innovative project to improve water quality in Lake Hodges. A newly installed oxygenation system, designed by city engineers, will introduce highly oxygenated water to the bottom of the reservoir to reduce the accumulation of excess nutrients and harmful algae growth.
Two projects underway will enhance fish habitat and water quality at Murray Reservoir.
The reservoir in Mission Trails Regional Park is owned by the City of San Diego and operated by its Public Utilities Department.
“As stewards of the area, it is important for us to improve and enhance the environment in and around Murray Reservoir,” said Shauna Lorance, director of the San Diego Public Utilities Department. “Working closely with state and local agencies allows us to better achieve this goal.”
Over the next six months, the Urban Corps of San Diego County will remove non-native plants and trees along Airoso Avenue to Murray Dam as part of the Chaparral Canyon Habitat Restoration Project.
The removal of invasive plants and native habitat restoration will directly benefit the City of San Diego and the San Diego River Conservancy by improving water quality in the San Diego River, reducing the canyon’s vulnerability to wildfires.
Funding for the $382,513 project comes from the San Diego River Conservancy and the California’s Water Quality, Supply and Infrastructure Improvement Act of 2014.
In addition, the city is working with California Department of Fish and Wildlife on a fisheries habitat enhancement project at Murray Reservoir through June 2020. The project is intended to increase fish abundance and angling opportunities for the public by adding fish habitat structures to the reservoir.
The fish habitat structures, including brush and synthetic materials, will provide the type of physical cover that several fish species prefer to nest near. The new structures are intended to increase reproduction and provide additional areas where juvenile and adult fish can avoid predation.
Murray Reservoir is open daily from sunrise to sunset and closed on Christmas and New Year’s Day. A valid California Fishing License is required for anglers 16 years of age or older.
The City of San Diego’s Public Utilities Department last week took a major step toward completing an innovative project to improve water quality in Lake Hodges. A newly installed oxygenation system, designed by city engineers, will introduce highly oxygenated water to the bottom of the reservoir to reduce the accumulation of excess nutrients and harmful algae growth.
The increase of nutrients and algae in the water has been caused by human activities in the watershed upstream of the reservoir, including residential and commercial development, agriculture, and land clearing. Degraded water quality can restrict the ability to move water in and out of the reservoir.
“The ‘Speece cone’ is a fairly unique method for adding oxygen to a reservoir – there are only a few of them in the world,” said Jeff Pasek, project manager at the City of San Diego Public Utilities Department. “This project derived from a planning study that was done about five years ago, which identified oxygenation using the ‘Speece cone’ as being the most cost-effective way of addressing the water quality problems in Hodges.”
Last week, the 130,000 pound cone – named after the inventor of the technology, Richard Speece – was lowered eighty feet to the bottom of the reservoir.
The precisely coordinated operation involved lifting the 20-foot tall stainless steel cone with a large crane, while simultaneously driving a barge out from underneath. Once the cone was lowered into the water, divers headed to the bottom of the reservoir to unhook the cone from the crane, check to make sure it settled in the correct spot, and fasten it down.
In order to build a solid foundation underwater, crews excavated approximately 11 feet of silt from the bottom of the reservoir and constructed a concrete base. Before submerging the cone, crews installed and tested a pump that will move water through the cone. A large diffuser pipe was then lowered and connected to the cone by divers. The diffuser will distribute the oxygen-rich water throughout the reservoir.
Now underwater, the cone will distribute oxygen-rich water throughout the reservoir to reduce the accumulation of excess nutrients and prevent harmful algae growth. Photo: Water Authority
Hodges Reservoir is owned and operated by the City of San Diego, and it serves the San Dieguito Water District and the Santa Fe Irrigation District. It is connected to the San Diego County Water Authority’s Olivenhain Reservoir as part of the Emergency & Carryover Storage Project, which is designed to ensure regional water reliability in case of emergencies or if the region is cut off from imported water supplies.
“There are multiple benefits to this project – first and foremost being the water quality improvements for Hodges Reservoir,” said Goldamer Herbon, a senior water resources specialist at the Water Authority. “Ancillary benefits include operational flexibility for regional supply benefits and preventing the accumulation of mercury, which can be harmful to people and wildlife that eat fish from the reservoir.”
The California State Department of Water Resources awarded the City of San Diego a $3.4 million grant funded by the San Diego Integrated Regional Water Management program to complete the oxygenation project, which began in February 2019.
The Water News Network is San Diego County’s source for water news and information.
