The Loma Rica Reservoir is located directly east of the City of Grass Valley, Nevada County, California, at an elevation of 3,154 feet above mean sea level (msl). The reservoir is located on property owned by the Nevada Irrigation District (NID) and it is approximately 1,500 feet east of the Nevada County operated airport and public use runway. The reservoir is part of the NID water-supply system and it stores raw water delivered through the Cascade Canal and the Banner Cascade Pipeline. The reservoir had a maximum capacity of 96.9 acre-feet (31.6 million gallons) when it was first constructed in the early 1960’s. Since then silt and sediment deposited in the reservoir with the incoming water sources have significantly decreased its capacity. This decrease adversely effects capacity of NID’s drinking and irrigation water systems.
Water from the Loma Rica Reservoir supplies the Loma Rica Water Treatment Plant and the Chicago Park Canal, an NID supply route for raw-water customers. The reservoir is not directly connected with any local creeks nor does it discharge to any natural water bodies or streams.
The Project entails a multi-year process of removing accumulated sediment from the Reservoir. The Loma Rica Reservoir Cleaning Project began with the dredging of the Reservoir in the fall of 2017. A second and third dredging period occurred in 2018 and 2019, respectively. Approximately 48-50,000 cubic yards of sediment was removed during the last three years.
The removal of the sediment was accomplished by first draining the reservoir followed by approximately one month of drying. The sediment was then excavated using front-end loaders and excavators. The excavated sediment was then placed either on adjacent previously disturbed land or transported off site to and deposited on the Nevada County airport property that filled in a depression north of the runway.
The Reservoir cleaning generally occurred between September and January. This time frame minimizes environmental impacts and takes advantage of lower water demands for the NID such that the reservoir inactivity will not significantly affect NID’s operation. The District removed approximately 9,000 to 11,000 cubic yards in 2019. The District has determined that sediment removal from the reservoir is complete. Remaining stockpiled sediment adjacent to the reservoir is in the process of being moved to locations on the County airport.
The identified potentially significant impacts of the project were less than significant with the incorporation of mitigation measures into the project. The potentially significant project impacts and associated mitigation measures are included in the project’s Initial Study/Limited Negative Declaration dated April 5, 2013. The environmental documents are located on this page under "Project Documents"
The adoption of this project occurred at the NID public Board Meeting on May 22, 2013.