Aspen Continues To Provide Full Suite Of Environmental Services For Littlerock Sediment Removal Project
Littlerock Reservoir and Dam were built in 1924 for the purpose of impounding seasonal water flows (rainfall and snow melt) from Little Rock Creek. The facility is owned by Palmdale Water District (District) and is located within Angeles National Forest. The water stored within Littlerock Reservoir is a critical part of the larger potable water system serving the City of Palmdale and the growing surrounding unincorporated communities.
Annual water flow from Little Rock Creek transports fine sediment into the Reservoir. Major fire events within the Forest (such as the 2009 Station Fire) have also caused transportation of unusually large quantities of sediment into the Reservoir. Over time, sediment build-up within the Reservoir has reduced its design water storage capacity by approximately 30 percent. The Littlerock Reservoir Sediment Removal Project (project) was proposed by the District to restore the Reservoir’s water storage capacity through ongoing sediment removal.
The portion of Little Rock Creek just upstream of Littlerock Reservoir has been designated critical habitat for the federally endangered arroyo toad. In order to preserve critical habitat for the arroyo toad, Aspen Environmental Group was retained by the District to develop a creative design component in the form of a grade control structure, which was not originally part of the project. The proposed project includes the following key features and actions:
Construction of a subterranean grade control structure, which ensures that sediment removal does not result in erosion (or headcutting) of upstream areas of Little Rock Creek that support arroyo toad and its designated critical habitat.
Removal of approximately 1,200,000 cubic yards of sediment from the Reservoir over 12 years, restoring the design water storage capacity. Once restored, Reservoir capacity would be maintained by removing approximately 50,000 cubic yards of sediment every 3 to 5 years as part of regular operations and maintenance activities. Removed sediment will be transported via truck to nearby quarries to backfill exhausted sand/gravel mining pits.
Aspen has been providing the District with a multitude of services for this project and, so far, has prepared a joint Environmental Impact Statement/Environmental Impact Report (EIS/EIR) analyzing the environmental effects of the project, with the District serving as lead agency under the California Environmental Quality Act (CEQA) and the USDA Forest Service (Angeles National Forest) serving as the Lead Agency under the National Environmental Policy Act (NEPA). The District certified the EIR and approved the project in March 2017. The Forest Service approved the EIS and signed the Final Record of Decision approving the project in June 2017. Currently, Aspen is coordinating with permitting agencies (i.e., CDFW, RWQCB, USACE, etc.) to secure permits for the project, and we are working on finalizing the design for the grade control structure. The next phase of work for Aspen will include development of the excavation plan, assisting the District with the construction bid packet, training construction personnel, and conducting mitigation and compliance monitoring.