Enhanced Recharge in the Santa Ana River Spreading Basins
Phase 1A and Phase 1B
The Seven Oaks Dam lies 4 miles northeast of Redlands, in the San Bernardino National Forest. The dam was constructed between 1993-2000 across the Santa Ana River. It was engineered to withstand up to a magnitude 8.0 earthquake and has a 2,980 foot crest length.
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Background
The main purpose of the Seven Oaks Dam is to serve as flood protection to Orange, Riverside, and San Bernardino Counties. However, it is also used to impound stormwater for groundwater recharge.
Using the stored water from the Seven Oaks Dam strategically for groundwater recharge can augment local water supply, protect water quality, restore ecosystems, and enhance downstream habitats for several key species.
In order to fulfil these goals, San Bernardino Valley Municipal Water District (Valley District) spearheaded the Santa Ana River Enhanced Recharge Project, in collaboration with the Western Municipal Water District (Western), City of Riverside Public Utilities, and San Bernardino Valley Water Conservation District (Conservation District). Due to environmental permitting and other constraints, the Project has been strategically proceeding in a phased approach.
Phase 1A
Stormwater captured behind the Seven Oaks Dam can be put to beneficial use when diverted from the Santa Ana River to spreading basins and delivered to local water agencies. Phase 1A of the Santa Ana River Enhanced Recharge Project involves construction of a new diversion structure, sedimentation basin, Plunge Pool Pipeline, and inlet channel to facilitate the conveyance of water from the Seven Oaks Dam—up to 500 cubic feet per second (cfs)—to be diverted for recharge into the San Bernardino Basin.
A major portion of the construction for the Phase 1A Project started in 2017 was subsequently completed in early 2019. Since then, the diversion structure, Sedimentation Basin, Pipeline, and other associated appurtenances have been tested and are in operation as designed. However, possibly due to past uses for the area where the Sedimentation Basin is located, excessive percolation resulting in localized flooding in the adjacent area of the Basin was observed during testing and needs to be addressed by partially lining the basin.
The Phase 1A Liner Project includes the construction of a geosynthetic liner partially across the existing Sedimentation Basin that is designed to reduce water turbidity—haziness caused by particles of sediment—before it travels into the downstream groundwater recharge basins. The liner is intended to slow the infiltration rate to 5 cubic feet per second within the Basin, which allows the fine sediment to drop out of the stormwater, while also minimizing potential impacts to the surrounding environment from rapidly percolating water.
The Sedimentation Basin temporarily stores diverted water and allows the sediment to settle out before moving the water downstream to groundwater recharge basins. This prevents fine sand and silt from entering the Plunge Pool Pipeline. Fine sand is removed before the water is delivered to Valley District facilities for recharge or direct delivery to water treatment plants.
The Plunge Pool Pipeline is 8 feet in diameter, approximately 1,900 feet long and connects the end of the Sedimentation Basin to an extension of the existing Foothill Pipeline. This Pipeline extends southwest from the basin, then northwest along the north side of Greenspot Road. The Foothill Pipeline extension will be approximately 1,328 feet long.
Phase 1B
This phase of the Enhanced Recharge Project is set to more than double the number, size, and capacity of recharge basins immediately downstream of the Seven Oaks Dam. This phase includes improvements to an existing canal to accommodate increased water flow, and construction of 337.4 acres of new basins to expand recharge capability. Phase 1B activities will integrate with previously constructed Phase 1A Project facilities. These improvements mean that the amount of stormwater from the Santa Ana River that can be captured during wet years and stored underground for beneficial use during dry years is greatly increased.
The stormwater captured by this Project and recharged into the San Bernardino Basin will benefit approximately 400,000 people who overlie the groundwater Basin, as well as the approximately 326,400 people in the City of Riverside that utilize water from the San Bernardino Basin. Current drought conditions in the Santa Ana River Watershed, the San Bernardino area, and the City of Riverside range from Severe Drought to Extreme Drought, according to the US Drought Monitor. These conditions highlight the importance of this Project to the region. Phase 1B of the Enhanced Recharge Project will enhance stormwater capture and recharge an average of 15,412 AFY, resulting in 10,807 AFY additional water supply and substantially increasing the drought resiliency of this crucial groundwater source. Construction for this Project is estimated to be completed by March 2024.
The Wash Plan
The land used for the Enhanced Recharge Project is balanced with the needs of the community and industry, as well as the environment. The San Bernardino Valley Water Conservation District's Upper Santa Ana River Wash Habitat Conservation Plan (Wash Plan) facilitates these needs, increasing natural habitat protection, water conservation, and mining. The Enhanced Recharge Project is a Covered Activity under the Wash Plan.
The Wash Plan establishes 1,660 acres of habitat in the Santa Ana River Watershed to help protect five species, four of which are listed as threatened or endangered under the Federal Endangered Species Act. The five Covered Species include two plants: the slender-horned spineflower and Santa Ana River woolly-star (both federally listed as endangered); one small mammal: San Bernardino kangaroo rat (federally listed as endangered); and two birds: the coastal California gnatcatcher (federally listed as threatened), and cactus wren. The Wash Plan also provides in-perpetuity (forever) funding for habitat restoration and monitoring of the 1,660-acre preserve.
The Wash Plan designates disturbed areas for mining operations, which supports job opportunities and significant economic benefits (mining operations are estimated to generate over $36 million in construction payroll to the region annually). Public trails which promote environmental education and appreciation of the Wash's natural resources are also a component of the Plan. The Wash Plan facilitates enhanced replenishment of the underlying groundwater basin, which can later be used by districts across the valley and to supply thousands of households with water. Specific to the Enhanced Recharge Project, the Wash Plan helps to offset environmental disturbance to the five Covered Species listed above, and their associated habtat, that may occur from construction of project.
Impact
The estimated overall cost for Phase 1A and 1B of the Enhanced Recharge Project is approximately $100 million. It took 19 years in order to secure water rights to capture water from the Seven Oaks Dam, and 9 years to permit, design, and construct just the Phase 1A Project. However, the time and money spent on these facilities will benefit one million people from Yucaipa to Fontana to Riverside County who will support their homes and businesses with the water this Project will provide. On average, this project will capture and recharge approximately 15,400 AFY of stormwater, resulting in approximately 10,800 AFY additional water supply. This Project is the result of over three decades of work to improve drought resiliency through capture and recharge of local stormwater in the San Bernardino Basin.
Explore these resources on Enhanced Recharge in the Santa Ana River Basin and other Valley District Projects
An interactive map of current Valley District projects
