Spanning approximately 3,460 ft, this levee will be made of compacted clay fill with a unit weight of 110 pcf, and cohesion of 1000 psf. The levee will have a slope of approximately 3H to 1V, a crown width of 16’, and a height of 1.5’ above the 100-year flood free boad elevation. While backside erosion may be a concern, it will be too costly to provide the entire internal perimeter with installed rip rap. Rather, to account for backside erosion, rip rap will be stocked piled on site so that it is readily available for the emergency armoring of the internal portion of the levee. Also, to allow for visual monitoring and ensure adequate maintenance vegetation must be continually removed along the toes of the levees. The Hydroponics component of the proposed system is a synthesis of Nutrient Film Technique and Deep Water Raft Hydroponics to address the needs of the Aquaponics Water Management System. Component design ratios are based on the reliable and robust University of Virgin Island’s 1/8 acre system which has been in operation since the 1980’s and is a model system for commercial aquaponics around globe. Hydroponics includes three main sub-components: Nutrient Film Tubes, Buoyant Rafts, and Anchors. Nutrient Film Tubes are hollow core pipes that transport nutrients to the plant roots. They are constructed from polyvinyl chloride and have holes eight inches apart containing net pots with growing media that supports plant roots. With 36 100-ft tubes per subsystem, each will support 5400 planters for an expected annual production of 11,000 lbs of vegetation. Aquaponics Water Management System will be designed with 600 subsystems,flower pots for sale so there are 3,240,000 planters in total for an approximate annual yield of six million pounds of produce. Buoyant rafts are constructed from PVC encapsulated Styrofoam, which may be recycled from Styrofoam used in packaging or other prior uses.
The buoyant force per volume of Styrofoam raft is approximately 55 lbs per cubic foot. The buoyancy required to keep each subsystem afloat is approximately 35,000 to 40,000 lbs. Therefore Aquaponics Water Management System requires approximately 400,000 cubic ft of Styrofoam rafts to produce approximately 21 to 24 million pounds of buoyancy to keep the system afloat. Anchors are based on a pole and slide method designed to prevent lateral movement of the rafts by wind and wave action while allowing for vertical movement of the rafts when there are changes in water height. The pole is a pier encapsulated with PVC and anchored in the ground by a concrete foundation or helix foundation anchor depending on the engineering load requirements. The loop is designed to slide vertically along the pier and is attached to the rafts as shown in Figure 4. The advantage of hydroponics over terrestrial agriculture is that it allows for more diverse crop production. While corn, asparagus, and sugar beets were abundantly grown on Sherman Island during most of the twentieth century, the majority of crops currently grown are field crop, such as wheat and barley. A variety of leafy vegetables, herbs, and other crops proven compatible with hydroponics can be potentially grown on Sherman Island with this system: artichokes, arugula, asparagus, basil, beets, broccoli, brussels sprouts, cabbage, carrots, cauliflower, celery, cilantro, collard, eggplant, endive, garlic, lavender, leek, lettuce leaf, okra, onions, parsley, parsnips, peas, bell peppers, radishes, raspberries, spinach, strawberries, and tomatoes. Floriculture is also compatible with hydroponics. Combinations of these candidates would be used in Figure 4. Schematic of anchoring system . order to take advantage of seasonal cycles, though some of these crops grow continuously throughout the year. Because the area does not experience extreme temperatures and frost, biennials and perennials could survive in the outdoor environment of the system. This system provides a competitive opportunity to produce crops that are unique to the area, specific to a niche market, and possibly organic. However, additional research needs to be done to test which crops would be successful at growing on site, especially with regards to the effects of seasonal weather, water salinity, bird migration, insect plagues, and other factors that may cause crops to fail.
While the equipment and resources for Aquaculture greatly depends on the fish species, a general design will be described. Incubation jars and tanks of varying sizes are needed to raise the fish. Stocking density depends on the fish size and stage of life and affects the number of tanks needed. Tanks should have water control values. Aerators and pumps are needed to provide oxygen and circulation. For fish health, filters are needed to regulate particulate concentrations in the water to the fish tanks, although not many would be needed by having snails in the tanks for cleaning. Feed may be live or dry, with the latter able to be delivered by automation. Depending on the temperature control needed, heaters or chillers may be necessary. A barn-like structure is necessary to house incubation and larvae tanks while adult fish tanks can be kept outdoors. Adequate piping and electrical wiring is needed among tanks, filters, and controllers. Parameters of concern to monitor are water pH, total ammonia nitrogen concentration, salinity, water temperature, and dissolved oxygen concentration. These parameters can be monitored by sensors and controlled by filters, heaters or chillers, and aerators. Each of the 600 aquaculture subsystems is comprised of 8,240 gallons of rearing tanks, 400 gallons of filtering and degassing tanks, 2,000 gallons of clarifiers, 50 gallons of base addition tanks, and 200 gallons of sump. The Aquaculture system has the potential to produce fish species for several purposes including conservation, fishing or live market sale. At first, conservation of the Delta Smelt or other endangered species was considered, but this prospect was discouraged after speaking with Dr. Joan Lindberg, director of the Fish Conservation and Culture Lab, who explained that Delta Smelt aquaculture is greatly resource-intensive and not economically viable for the proposed location because the California Department of Water Resources is planning other fish conservation efforts in Rio Vista. Therefore, fish rearing of species popular for fishers or sale on the live market would be more feasible for Aquaponics Water Management System.
Expert opinions agree that sturgeon or catfish are good candidates for this system to produce net profit on the live market. In addition, these species are currently fished in the Delta. Numerous literatures on the sturgeon and catfish aquaculture allows for detailed design and protocol to be easily made. Because catfish aquaculture is predominantly in the Southeast of the United States and sturgeon aquaculture research has been completed at U.C. Davis, this report will focus on sturgeon. Sturgeon aquaculture is especially lucrative for its caviar production. While it takes almost nine years for female sturgeon to be mature with eggs, younger sturgeon is valuable for its meat. At about 18 months of age, sturgeon is profitable to sell on the live market. Raising some fish from this age to 36 months allows for sex determination, and females may be further raised for caviar production while males sold for meat. With the 600 subsystems, there is enough capacity for fifteen brood stock and their offspring. This is expected to yield 215,000 fish for sale at 18 months. Since sturgeon is already present in the Delta, unintentional release into the San Joaquin River would not jeopardize the Delta’s fragile ecosystems.The internal cutoff levee encloses the flood storage zone and will serve as a secondary defense should river levees fail. In doing so, it must be able to withstand the principal causes of levee failure: over topping, surface erosion, internal erosion , and slides within the levee embankment or the foundation soil. Any levee constructed on Sherman Island inherits a number of issues that require intensive design, first and foremost being the quality of the foundation soils. The generalized subsurface soil profile and proposed internal levee when the internal area is back flooded to a level of 3ft is shown below in Figure 5. Most concerning is the approximately 40 foot peat layer that immediately underlies the levee. As a result, the foundation soils are extremely weak and compressible, variable, and feature severe underseepage vulnerability, which if left unaddressed can lead to piping and levee failure. The most common method of stabilizing is excavation and replacement of the peat layer however this is not economically feasible because the peat layer is too large. In addition to the problems with the peat layer there is a deep sand layer that has the potential to liquefy during a seismic event. US Army Corp of Engineers standards dictate that levees should be designed to a factor of safety of 1.3 to 1.4, dependent on the time scale for which a levee will be holding back elevated levels of water. Table 1 shows the minimum factors of safety for levee slope stability as designated by the USACE. While the internal levee will not be kept at a high flood level indefinitely,tower garden the levee must maintain at least a factor of safety of 1.4 as it is the critical piece of infrastructure protecting the aquaculture system and the rest of Sherman Island. Modeling of our proposed clay fill levee will determine the optimum back flooding to maintain this factor of safety while equalizing the pore pressure as much as possible. During design and construction of this levee, the consolidation of the peat soil needs to be considered.
Until the peat layer has been compressed, there will be minimal structural stability to the levee. Since, as described by Dr. Seed , for approximately every foot of fill placed the peat will settle approximately a foot. As such, the levee will need to be constructed in stages with a first layer being installed and then allowed to settle. To allow for sufficient consolidation, this layer will remain for approximately a year and a half. At this stage the second layer can be added up to the specifications of the levee design. The levee will be constructed with compacted clay fill with a unit weight of 110 pcf and cohesion of 1000 psf, to best limit flow through the levee.The existing levees that surround Sherman Island feature clearly delineated layers of soil similar to that in the internal portion of the island. Under seepage is a significant issue for these levees with the most common failure concern being piping. Additionally, the levees are constructed of sand rather than low hydraulic conductivity clays. Settlement through the years has led to constant repairs, and as such an irregular levee shape. Figure 6 displays the soil and levee profile that will be used for the geotechnical analysis. This levee is extremely susceptible to failure in high flood water events due to the high head differential between the rivers and subsided land inside Sherman Island. Therefore back flooding the flood storage zone is a favorable approach because it reduces the difference in hydraulic gradient.To determine the effects of back flooding, on the existing levees and the constructed levee, seepage analyses and slope stability analyses parented from the seepage analyses were performed. For the proposed internal levee, the profile was generated from soil borings and CPT tests provided by Caltrans for the Antioch Bridge. The profile for the existing levee was created for the RESIN project and given to us for use by Anna Harvey. This profile is appropriate for the project site as this profile was taken from an area near a previous failure, and has an extremely large peat layer. If the flood management can benefit this failure prone levee, then it can aid in the protection of levees at the southwest site. It should be noted that the actual 100 year and 50 year flood levels are +7.5 ft MSL and +5.5 ft MSL respectively. However, for simplicity of the model and to account for variability such as sea level rise, +8 and +6 ft were chosen, to provide a lower end estimate of factors of safety. The slope stability analyses were run with the Spencer method, as it is most applicable to this situation and is most accurate. . Additionally, the simulations were run assuming no tension crack. The data given in Table 2 from simulations performed demonstrate that back flooding the internal cutoff levee to a level of MSL + 6 ft maintains a factor of safety of 1.4 while MSL + 7 ft maintains a factor of safety of 1.3.