Green Gulch Farm Streamflow and Water Storage Improvement Project

Green Gulch Farm Streamflow and Water Storage Improvement Project

The CEQA Findings are based on the following project description. The Green Gulch Farm Streamflow and Water Storage Improvement Project is located within Green Gulch Farm (Farm), operated by the San Francisco Zen Center (Zen Center), situated along Green Gulch in the southwest corner of Marin County, California at 1601 Shoreline Hwy, Muir Beach, CA 94965 (37° 51' 57.4704'' N and 122° 33' 58.8816'' W). The site includes two assessor parcels (APNs 199-160-17 and 200-020-21) of which San Francisco Zen Center is the owner. The Farm contains 7.5 acres of irrigated fields and is surrounded by Golden Gate National Recreational Area (GGNRA) land. The Green Gulch Streamflow and Water Storage Improvement Project will restore Green Gulch’s natural hydrograph and increase streamflow to improve wildlife habitat and provide ecosystem resiliency in over 3,000 linear feet of lower Green Gulch and over 2,000 linear feet in the Redwood Creek estuary by eliminating spring and dry season direct diversion from Green Gulch. To accomplish the project goal, water storage will change from on-channel reservoirs to an off-channel pond to improve operational functionality, efficiency, and resiliency of Green Gulch Farm’s water storage and irrigation infrastructure; to provide the Farm with sufficient water to meet irrigation and emergency supply needs into the future in the face of climate change while reducing use to support ecological function. The project's primary emphasis is to create and enhance habitat for coho salmon and steelhead. The project will enhance instream flow and improve habitat conditions in Green Gulch and Redwood creeks, which are listed as high-priority watersheds in federal recovery plans for coho salmon and steelhead trout as well as sensitive species that are protected under the federal and California Endangered Species Acts. Both streams have experienced low summer baseflows causing loss of rearing habitat for these species, and both streams have had salmonid restoration projects implemented in the recent past. This project will have additional long-term benefits to coho and steelhead by increasing freshwater flow in the summer months when sufficient water is one of the most critical factors for juvenile survival. The project implements the following specific actions set forth in the recovery plan for California Central Coast coho salmon (NMFS 2012): • Work with the Muir Beach Community Services District and Green Gulch [F]arm to eliminate water diversions that affect flow within Redwood Creek. (ReC-CCC- 25.1.1.1) • Provide incentives to water rights holders willing to convert some or all of their water rights to instream use via petition change of use and §1707. (ReC-CCC- 25.1.1.2) • Promote off-channel storage to reduce impacts of water diversion. (ReC-CCC- 4.2.1.2) The restoration and improvement of the stream channel, reservoirs, and additional wetland and riparian features will create breeding and foraging habitat for California red-legged frog, California giant salamander, and northwestern pond turtle. The project will meet many of the recovery objectives for the California red-legged frog as described in the 2002 USFWS Recovery Plan (USFWS 2002). It increases the quantity and availability with habitat creation of aquatic breeding areas with an adjoining mix of riparian and upland habitats along Green Gulch and within an unnamed tributary area. These project components are designed to extend the habitat created by the National Park Service and the Golden Gate Parks Conservancy in 2010 and 2011 in the lower reach of Redwood Creek at Muir Beach, immediately downstream of the Redwood Creek/Green Gulch confluence. Creation of improved aquatic and riparian habitat associated with the project will also work toward recovery goals for the northwestern pond turtle as stated in the Western Pond Turtle Range-wide Management Strategy (Western Pond Turtle Range-wide Coalition (2022). The strategy provides guidance for the conservation and management of habitats to maintain resilient populations. The project will improve aquatic habitat while surrounding areas will provide the upland habitat required by the turtles. The project will create net benefits to the climate resiliency of both the habitats within, and species dependent on, Green Gulch Creek. The project design prioritizes conservation water management with a system that captures large amounts of water during periods of precipitation and stores it efficiently for use during the dry season; eliminating the need for diverting water from Green Gulch during the critical-dry season period where stream flow is essential for aquatic species. As drought and low-flow conditions become an increasingly common feature of the region's climate, the project's dry-season flow enhancement benefits will be increasingly vital to the climate resiliency of the stream and its biota. Likewise, the restored wetland features will act as buffers and refugia during high flow events. For Green Gulch Farm, the improved and consolidated off-channel storage will provide water for irrigation and fire protection even in dry years, ensuring further resilience to produce organic produce for themselves and the community. These project functions will become increasingly important as high flows and drought occur more frequently and at greater extremes in a changing climate. For example, maintaining a wetted channel through the dry season may allow fish to move between low flow refugia below the Project site and/or increase aquatic production supportive of the stream's food web. Several project components are needed to meet the project’s restoration goals. • A new 11.6 AF off-channel pond/Reservoir 7 will be constructed to replace the storage capacity eliminated by the removal of reservoirs 3 and 4 (discussed below) and to provide sufficient water storage to eliminate summertime direct withdrawals from Green Gulch at Zendo Pond. A new water pump will be installed adjacent to Reservoir 7 to move stored water to the farm fields for irrigation and to provide water if necessary, during fires or other emergency situations. The reservoir will include a cover to reduce evaporative losses by over an acre-foot per year. • The project will replace direct, dry-season flow diversion from Reservoir 3 (Zendo Pond) with a gravity-flow surface water diversion system during the wet season while maintaining minimum flows in Green Gulch during the withdrawal period. To accomplish this, Reservoir 3 (Zendo Pond) on Green Gulch will be filled to convert the on-channel pond to a channel and adjacent floodplain wetland that are vegetated with native wetland and riparian species to maximize habitat value. The existing point of diversion for the water right will be maintained to fill the new, offchannel reservoir (Reservoir 7) during winter high flows. The diversion period is November 1 through April 1, and diversion will only occur when flows in Green Gulch exceed 0.5 cfs (minimum bypass flows to Green Gulch). Flow that exceeds the capacity of the surface water diversion structure during the diversion period will continue down Green Gulch and into Redwood Creek. The maximum diversion rates will be 234 gallons per minute or about 0.52 cubic feet per second. • The project will decommission the storage capacity of an existing on-channel reservoir (Reservoir 4) by reducing the height of the pond embankment. The existing point of diversion will be maintained, and a new surface water diversion structure will be installed to provide a means to support filling Reservoir 7 as necessary during drought conditions and only used during the diversion period. Projected flows from the surface water diversion structure through a 2-inch pipe to Reservoir 7 would be about 300 gallons per minute or 0.7 cubic feet per second maximum. Flows exceeding the capacity of the surface water diversion structure will continue down the new rocked channel and into Redwood Creek. The reservoir area will be allowed to naturally transition to a wetland except for an area of the pond designed to hold perennial water for California red-legged frog breeding habitat. The goal of the decommissioned reservoir site is to provide habitat for California red-legged frog and other wetland-dependent species. • Installation of a new siphon at Reservoir 5 will replace the aging pump and maintain the ability to use water to help fill Reservoir 7 in emergency situations, such as drought. This siphon will be a screened high volume centrifugal 3-inch pump intake. The pump will be screened with a ½-inch by 1-inch mesh to allow fine particles through while keeping other items out. It will draw water, as needed during periods of extreme drought. • A new water-efficient irrigation system will be constructed to replace an existing, dilapidated system and will include connections to access water for fire emergencies. An existing in-stream pump (Pondato pump) and casing will be removed from the stream, and the irrigation supply will be replaced by Reservoir 7 and the newly constructed pump. • The project includes completion of petitions to change the Farm’s riparian and licensed appropriative water rights to enable implementation of the project. This will result in a reduction in the existing water rights from 17 AFA (acre feet per annum) to 15 AFA. It will eliminate use of riparian water rights from April through October annually, and it will result in the dedication of 2.0 AFA for instream flows. A change in the appropriative and the riparian water right is necessary to accomplish the goals of the project, and the Farm is dedicating a portion of their historic water rights to streamflow for the benefit of fish and wildlife. This Instream Flow Dedication (CA Water Code 1707) will protect the additional streamflow from any other use in perpetuity. The change in water right will reduce the licensed amount of water storage from 17 AFA to 15 AFA, and the Farm will cease using riparian rights from April through October for irrigation. • Project monitoring and adaptive management will ensure project goals and objectives are achieved. Monitoring will focus on the stability and revegetation of the restored areas at Zendo Pond, Reservoir 4, and along with the new rocked outfall below Reservoir 4 to ensure the areas are functioning and the vegetation efforts are successful. Adaptive management activities may include additional plantings of native vegetation and removal of invasive species through the restored areas. Although not necessarily expected, adaptive management may also include grading or at Zendo Pond or Reservoir 4 if monitoring shows the newly created wetlands, the frog pond, or the stage zero channel and surrounding wetlands/floodplain is not functioning as well as expected. This work could occur for up to five years following the completion of construction. Implementation of the restoration elements described above will occur over two June- October construction seasons once implementation funding is secured (2026-2027 or later). Adaptive management will occur in up to five subsequent years, primarily focusing on function of the water diversion structures, revegetation efforts, and function of the California red-legged frog pond. The approximate final footprint for the anticipated improved habitat conditions includes the following: • Reservoir 3 wetland restoration: 0.4 acres • Reservoir 4 seasonal wetland restoration: 0.1 acres • Reservoir 4 upland native vegetation restoration: 0.7 acres • Enhanced streamflow reach (Green Gulch): 3,200 linear feet • Enhanced streamflow reach (Redwood Creek): 2,000 linear feet Project implementation methods include grading to restore floodplain and wetland areas and to construct off-channel storage at the new Reservoir 7, installation of erosion control, and revegetating with native wetland, riparian, and upland plants. Institutional elements of project implementation include water rights changes to reduce licensed water storage, eliminate direct diversion during April to October, and maintain minimum stream flows during the November through March collection period.

unincorporated area

Marin

Northern California, San Francisco Bay Area, Unincorporated

Marin