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3.4.4.11 Northwestern pond turtle (Clemmys marmorata marmorata) (SC/CSC) The northwestern pond turtle is a subspecies of the western pond turtle with a range that extends from the Sacramento Valley north of the American River into the State of Washington (Holland 1994). The species was once common in the Central Valley marshes, and remains well distributed throughout its historic range, but in greatly diminished numbers. Loss, degradation, and fragmentation of habitat are the primary factors contributing to its decline. The northwestern pond turtle occurs and forages in both permanent and intermittent aquatic habitats, including ponds, marshes, lakes, streams, and irrigation ditches; exposed rocks, logs, or other basking sites are required. Terrestrial overwintering occurs in burrows in leaf litter or dry soil near aquatic habitats, and the species may spend over 100 days in such overwintering habitats. Female pond turtles also leave aquatic habitats in June to deposit eggs in sunny upland habitats, including pastures. Nesting may occur at some distance from aquatic habitats (402 meters is reported by Jennings and Hayes 1994). Overland movement of over a mile may occur when it is necessary to seek new aquatic habitats. The pond turtle and giant garter snake are sympatric within the range of the latter species. Pond turtles were observed basking on a fallen log in the Main Drain during a March 2004 survey. Other portions of the Action Area do not provide suitable habitat. There is no connectivity from the Main Drain to the Combined Pumping Plant/Fish Screen site. Pond turtles could occur in the Colusa Basin Drainage Canal and the Main Drain, and could incidentally move into temporarily flooded unlined farm irrigation ditches and rice fields. 3.4.5 Environmental Consequences 3.4.5.1 Data Potential effects associated with construction and operation of the Proposed Project on protected species of plants, wildlife, and fish have been evaluated. The evaluation was based on consideration of (1) construction activities and the area anticipated being disturbed, (2) habitat conditions currently existing in the Action Area, and (3) known or presumed occurrence of protected species in the area. Data sources for the analysis of effects included:
Results of these plant, wildlife, and fishery studies provide the scientific basis for evaluating potential adverse effects of the proposed project on protected species and EFH. 3.4.5.2 Approach to Analysis of Environmental Effects to Biological Resources Based on information regarding habitat conditions and the occurrence of special-status species in the Proposed Project area, environmental consequences of implementing the Proposed Project were evaluated based on analysis of potential direct and indirect effects of the project. The analysis included identification of potential disruption of habitat conditions, above existing baseline conditions that would potentially affect the occurrence and distribution of protected species within the proposed Action Area. The proposed project actions were then evaluated to assess their potential for modifying environmental conditions within the Action Area above existing baseline conditions. The potential mechanisms for activities to affect special-status species were defined. The focus of analysis was to examine each element of the Proposed Project, identify mechanisms of effect (stressors), the timing and duration of effects, and thus the potential for effects on species, by life history stage. The analysis approach was then used to evaluate potential project effects on each of the identified protected species and their habitat related to:
The potential project effects on the species addressed in this EA/Initial Study are summarized on Table 3-6 and explained in detail following the table. Table 3-6. Summary of potential project effects on special-status species, by project element.
3.4.6 Environmental Consequences: Spring-run Chinook, Winter-run Chinook, Winter-run Critical Habitat, Steelhead, Fall-run/late Fall-run Chinook, Proposed Critical Habitat for Spring-run Chinook salmon and Steelhead, and Essential Fish Habitat for Pacific Salmon 3.4.6.1 Rational for consolidation of Effects Analysis for these Species Sacramento River fish species that have been identified for protection under the State and/or Federal ESAs that are evaluated as part of this EA/Initial Study include winter-run and spring-run Chinook salmon, and Central Valley steelhead. The Sacramento River in the Action Area has also been designated as critical habitat for winter-run Chinook salmon. NOAA Fisheries is currently evaluating the proposed designation of the Sacramento River as critical habitat for spring-run Chinook salmon and Central Valley steelhead. Fall-run and late fall-run Chinook salmon are also included as part of the EFH assessment. The potential environmental consequences of the Proposed Project are expected to be similar for winter-run and spring-run Chinook salmon, and steelhead; hence, they are discussed collectively below. The juvenile life stages of each of these protected species are vulnerable to entrainment at the currently unscreened RD108 facilities and, therefore, each of these species would benefit from reduced mortality resulting from operation of the proposed positive barrier fish screen. Based on information regarding their habitat distribution and known or presumed occurrences in the area of the Proposed Project's 4-mile reach of the river, an assessment has been made of the potential effects associated with construction, operation, and maintenance of the facility on each of the identified fish species. Results of the assessment are briefly discussed below. 3.4.6.2. Effects of Combined Pumping Plant/Fish Screen Construction Direct project effects on salmon and steelhead would result only from cofferdam installation, construction of the Combined Pumping Plant and Fish Screen, cofferdam removal, dismantling of existing diversions, and long-term operations effects on fish habitat. Other aspects of the project do not involve work in or adjacent to the mainstem Sacramento River. There are several potential mechanisms for construction of the proposed project to directly affect salmon and steelhead. Direct effects are related to:
The effects of these mechanisms will vary on the various salmonids in the river depending on the timing of the 60-day period of cofferdam construction (Table 3-7). Table 3-7. Cofferdam construction timing and salmonid ESU impacts from noise, sedimentation, and stranding.
As Table 3-7 indicates, there is no 2-month construction period for cofferdam construction that avoids potential for project effects on salmonids, although the June through August period probably affects the fewest ESUs/runs. It should be noted that delay in implementation to avoid cofferdam construction impacts could result in exposure of all ESUs/runs to an additional year of unscreened diversions at existing facilities. Loss of Habitat: The construction of temporary cofferdams and the Combined Pumping Plant/Fish Screen will remove up to 0.10 acres (0.4 hectares) of aquatic habitat along banks of the river (300 feet x 5 feet; 91 x 1.5 meters). At the same time, the improvement of screening facilities for RD108's agricultural diversions will reduce entrainment of juvenile salmon and indirect diversion-related effects on adult salmon migration. Although various special-status fish species are present seasonally in the area, the habitat within the Sacramento River at this site is not unique and is characterized by levees stabilized with riprap and lacking in emergent vegetation, a relatively deep, high velocity channel, and silt and sand substrate. The area is not used as spawning habitat by salmonids. Juvenile Chinook salmon and steelhead use the area as a migratory corridor and juvenile foraging area during downstream migration. Juvenile and adult salmon and steelhead would continue to utilize the Sacramento River as a migratory corridor. Given the presence of riprap and a lack of submerged aquatic and emergent vegetation cover habitat, the area of channel where the facility will be placed would not be considered to have favorable rearing habitat quality for salmon or steelhead; in addition, there are smallmouth and largemouth bass in the river, which are non-native warmwater predators on juvenile salmonids. Use of the channel with its lack of cover habitat under present conditions does not provide any advantages to juvenile salmonids and carries the risk of predation. The net value of the channel lost due to the project is therefore low. A vertical fish screen in this reach of the river would not reduce movement in the migration corridor and the difference in habitat quality between the riprapped and unvegetated channel margin and a fish screen will be minor. The change in habitat is not likely to adversely affect Chinook salmon or steelhead populations, critical habitat for winter-run Chinook salmon (or pending critical habitat for spring-run Chinook salmon and Central Valley steelhead). Stranding of Salmonids during Construction: Over the 24-month construction period, adult and juvenile salmonids may be stranded behind the cofferdam following initial construction and at any time when high river flows overtop the cofferdam. Fish stranded in the area behind the cofferdam would be rescued (netted) and returned to the river. The life history stage affected during the initial closing of the cofferdam will depend on construction timing. The preferred timing for construction of the cofferdam is during low-flow periods in the fall (July-September 2005). If construction occurs during this time period, it would most affect winter-run Chinook salmon juveniles rearing and migrating through the project reach. Early spring cofferdam construction schedules would shift effects to spring-run Chinook salmon juveniles, fall-run/late-fall-run Chinook salmon juveniles, and winter run Chinook salmon adults. Adults on their spawning run may be stranded, but large adult fish can be more readily removed from the cofferdam area during dewatering. Although salmonids respond well to handling, there would be incidental injury and death to individuals of the various salmonid species as a result of handling and it is probable that the rescue program would not capture and release every juvenile. Results of a similar fish rescue operation behind the cofferdam installed during construction of the RD 108 Wilkins Slough fish screen showed that no salmonids were stranded (less than 10 fish total were collected in the fish rescue) suggesting that the potential loss of salmonids to stranding in any season is low. Depending on the season when the cofferdam is installed some (unquantifiable) loss of salmonids due to stranding is nonetheless probable. This is an adverse direct effect. During construction of the Proposed Project, RD108 would continue to divert water at the three existing diversions in the project reach (Boyers Bend, Howells Landing, and Tyndall Mound). These diversions would be made in a manner consistent with current practices and no changes in diversion quantities or timing of diversions are anticipated. There would be no change in the effects of these diversions on the aquatic biota. Turbidity and Suspended Sediments: The site of the proposed Combined Pumping Plant/Fish Screen was selected because of its uniform depth and substrate. It will this be feasible to drive cofferdam pilings into the substrate without prior dredging. Pilings will not be removed following construction, but will be cut off, and the buried sections of these pilings will remain to provide added scour protection for the concrete foundation of the plant. Following cofferdam construction, the area behind the cofferdam will be dewatered. The only mechanism for creation of turbidity and suspended sediments during construction is therefore the driving of pilings. The period of increased turbidity would be limited to the period of installation of the cofferdam(s), a period of about 60 days. Driving pilings creates vibrations at the edge of the piling as it enters the sediment, causing displacement of sediment and re-suspension of fines. This occurs at the surface of the channel bottom, where a narrow stream of fine sediments may be resuspended. It is not likely that heavier sediments will be re-suspended more than several inches, and they will probably fall out of suspension within less than 100 feet (30 meters). Observations during similar construction activities associated with the installation of cofferdams and construction of the RD 108 Wilkins Slough Pumping Plant fish screen suggest that increases in turbidity and suspended sediments would occur in an area of about 100 feet (30 meters) wide and 1,000 feet (300 meters) long or less. Increased turbidity and suspended sediments would occur intermittently during construction of the cofferdam; water quality conditions would be expected to return to background levels within hours after construction activity is completed. This short-term increased turbidity and suspended sediment concentrations has the potential to adversely affect protected fish species, potential migration of winter-run Chinook salmon through critical habitat within the Action Area, and EFH for Pacific salmon, depending on the seasonal period when site preparation and installation/removal of the cofferdam occurs. Since site preparation and installation of the cofferdam are most likely to occur during periods of reduced flow within the Sacramento River the likelihood of adverse affects to winter-run Chinook, spring-run, and fall-run fry migration, critical and essential fish habitat and steelhead migration is reduced. Spring-run and fall-run Chinook salmon and juvenile steelhead may occur in the Action Area during the spring and would potentially be exposed to increases suspended sediment concentrations. The turbidity plume resulting from site preparation is not expected to extend across the entire Sacramento River, but rather the plume is expected to extend downstream from the site along the western edge of the channel. As a result of the limited distribution of the plume within the river salmonids would have the opportunity to readily avoid the plume during either upstream or downstream migration. The projected localized increase in turbidity during portions of the construction periods may result in short-term (hours or days) changes in behavior or distribution of salmonids within the immediate vicinity of the site but would not be expected to have adverse effects such as mortality or blockage of migration on special-status salmonids. Erosion control measures along access roads result in this portion of construction having no adverse effect on salmonids. Although increases in turbidity associated with installation and removal of the cofferdams has been identified as a potential effect to protected fish species and EFH, the magnitude of this effect is likely to be very small. The EFH specifically discusses habitat concerns related to sediment discharge in terms of (Pacific Salmon Fisheries Management Plan, Appendix A, 1999): "Reduced survival of eggs and alevins, reduced primary and secondary productivity, interference with feedings, behavioral avoidance and breakdown of social organization, pool filling" As explained below, the project would not generate suspended sediments that would raise these concerns related to EFH. First, the period of effect is short. Based on bathymetry measurements there should be no need to dredge prior to cofferdam installation and cofferdam construction will occur in 60 days or less. Second, the area of the river downstream of the project site potentially affected by suspended sediment concentrations above background conditions is estimated to be 100 feet (30 meters) wide and less than 1,000 feet (300 meters) in length, based on observations during similar construction activity within the Sacramento River. Suspended sediment concentrations during installation and/or removal of the cofferdam would be managed, to the maximum extent possible, within the limits and constraints of RWQCB permit conditions that have been included as a conservation measure (Section 4). Third, the physiological and behavioral effects of turbidity on salmonids are likely to be minor. A substantial body of scientific information exists regarding the response of juvenile and adult Chinook salmon, steelhead, and other fish and macroinvertebrates to elevated suspended sediment concentrations and turbidity. Wilbur and Clarke (2001), Clark and Wilbur (2000), Newcombe and Jensen (1996), Burton (1985), Gregory and Levings (1996), Johnston (1981), Newcombe and MacDonald (1991), Newell et al. (1998), O’Connor et al. (1976), Peddicord et al. (1976), Peddicord and McFarland (1978), Servizi and Martens (1991), Sherk (1971), Sherk et al. (1974, 1975), Sigler et al. (1984), Stern and Stickle (1978), Whitman et al. (1982), and other investigators have synthesized and reviewed the available scientific information on the effects of suspended sediments on various species and lifestages of fish and macroinvertebrates. The potential for adverse effects resulting from suspended sediment and/or turbidity exposure is a dose response that varies depending on the magnitude of the concentration of sediments, the duration of exposure, the type of material, the species and life stage of the organism, and other factors. Ross (1982) reported 50% mortality for juvenile Chinook salmon exposed to suspended sediment concentrations of 11,000 mg/l over a 96-hour exposure period. Phillips (1970) reported reduced feeding activity by adult Chinook salmon exposed to suspended sediment concentrations of 25 mg/l over a 4-hour exposure period. Whitman et al. (1982) reported a behavioral response for adult Chinook salmon exposed to suspended sediment concentrations of 350 mg/l while Redding and Schreck (1982) reported that adult steelhead exposed for nine hours to a suspended sediment concentration of 500 mg/l experienced sublethal changes in blood chemistry. Griffin (1938) reported that adult Chinook salmon exposed to suspended sediment concentrations of 525 mg/l experience no effect after an exposure in excess of 500 hours. Newcombe and Flagg (1983) reported 50% mortality for juvenile Chinook salmon after a 36-hour exposure to volcanic ash at a concentration of 9,400 mg/l. Newcombe and Flagg (1983) also reported that adult Chinook salmon experienced no mortality or apparent adverse effects after a 24-hour exposure to volcanic ash at a suspended sediment concentration in excess of 39,000 mg/l. This body of information on suspended sediment and turbidity affects on various lifestages of Chinook salmon and many other fish and macroinvertebrate species have been used in developing water quality criteria that would be protective of the aquatic species inhabiting the Sacramento River and other areas. The suspended sediment and turbidity concentrations and duration of exposure for Chinook salmon or steelhead in the Sacramento River during cofferdam installation are expected to be substantially below the levels reported in the literature resulting in adverse effects. The RWQCB standard for effects is "activities shall not cause settleable matter to exceed 0.1 ml/l in surface waters as measured in surface waters 300 feet (91 meters) downstream from the project. Because ambient suspended sediment data are recorded in mg/l (a measure of weight), it is necessary to convert the volumetric RWQCB standard (ml/l) to a weight. Assuming that the suspended sediment consists mostly of quartz and other silicates weighing about 2.6g per ml, the RWQCB threshold of impact converts to 0.26g/l or 260 mg/l. Note that this standard is a measure of the volume and weight of suspended sediments, and larger particles (fine to coarse sands) make up the vast majority of the volume and weight in any suspended sediment measure. To quantify the effect of the project on ambient suspended sediment concentrations in the Sacramento River, it is necessary to determine whether the amount of sediment generated by the project will increase ambient settleable sediment concentrations to a level exceeding the RWQCB standard. Ambient suspended sediment concentrations in the Sacramento River can be quite high during periods of flooding, and ambient concentrations of sediment are in excess of 20-30 mg/l on a routine basis. Ambient suspended sediment concentrations in the Sacramento River are collected upstream of the Action Area at USGS Station 11389500 (Colusa). In a relatively normal-dry water year (1999-2000), the suspended sediment concentrations taken at this station were:
These levels are similar to those taken at the USGS Knight's Landing gauging station (Station 11391100) and thus are probably representative of conditions in the mainstem river at the site of the Combined Pumping Plant/Fish Screen, which is between these two stations. Ambient suspended sediment concentrations, which are almost entirely made up of settleable materials, clearly vary with flow and also reflect seasonal conditions, particularly the release of reservoir storage, with relatively low suspended sediment concentrations, in the summer and fall. To determine if the project would contribute sediment to this background concentration in excess of that permitted by the RWQCB, it is necessary to estimate the amount and distribution of sediments generated by project construction activities and convert this to mg/l. Based on monitoring data from the RD 108 Wilkins Slough Pumping Plant project, the Proposed Project's construction activities would generate a turbidity plume that may extend 1000 feet (300 meters) downstream and be about 100 feet (30 meters) wide and 20 – 30 feet (6 to 9 meters) deep (approximate channel depth). This plume would be composed almost entirely of very fine sediments (silts and clays) and the majority of suspended sediment (by weight) would likely not be distributed into the upper water column at all by the vibrations of the sheet pilings during installation. A flow rate of about 2 ft/s (0.6 m/s) is required to suspend sands (USGS 1976), and sands rapidly settle out of suspension. Wallingford (1994, cited in CSL 1999) found that coarse sands spilled from dredging barges in 25 meter-deep (82-feet) water with current velocities of 1.75 m/s (5.7 f/s) fell out of suspension within 50 meters. This equates to a settlement rate of about 0.9 meters per second (3 ft/s). Fine sands fell out of suspension at a much lower rate of about 0.045 meters per second or 0.15 ft/second. Since mid-channel flow rates in the Sacramento River reach velocities of 2 f/s when flows are in the 10,000 to 15,000 cfs range (typical of conditions during the proposed construction periods), and side channel flow where construction will occur would have lower velocities, even fine sand mobilized and suspended as much as 3 feet (0.9 meters) above the bottom during pile driving would settle out of suspension (at a flow of 1 to 1.5 f/s or 0.3 to 0.45 m/s) in about 20 seconds, or within about 20 to 30 feet (6 to 9 meters). Coarse sand would fall out of suspension more rapidly. Thus, the area of effect related to suspended sediments would be quite small; in a worst case, with flows in the 20,000 cfs range and flow velocities greater than 2-3 f/s (0.6 to 0.9 m/s), medium to coarse sediments would be expected to fall out of suspension within 100 to 200 feet (30 to 60 meters). At a distance of 300 feet (91 meters) downstream from the project, suspended sediment loads generated by the project would no longer be measurable, as they would consist entirely of very fine silts and clays, which create turbidity, but do not contribute to the concentration of settleable materials. In short, suspended sediments generated by the cofferdam construction would affect a small part of the channel bottom and an even smaller percentage of the water column. A visible turbidity plume of 1000 feet (300 meters) in length and 100 feet (30 meters) in width would also be possible during cofferdam construction. Given the curve of the channel in this location, this plume would probably be contained on the west side of the river, and fish could readily avoid it. Maintaining water quality conditions within the bounds established by the water quality conservation measure described in Section 4 would avoid sublethal or other adverse effects on juvenile and adult life stages of all ESUs/runs of Chinook salmon and steelhead as a result of the proposed installation of the cofferdam. No turbidity-related effects to salmonid physiology or behavior are therefore anticipated as a result of the project. Exposure to Underwater Sound Pressure Levels: Installation of sheet pile and beams during construction of the cofferdam would be performed using a vibrating method, with sheet piling installation occurring 8 hours a day, 5 days a week for about 8 weeks. Both vibratory and percussion hammers produce sound waves that can be perceived by fish. Based on studies of the use of sound as a potential barrier to fish movement (Hanson 1996), salmonid behavioral responses to sound are inconsistent. There is some potential for fish to avoid the west side of the river in response to pile driving. Vibrating hammers do not produce sound pressure levels at the 180 db pressure level resulting in damage and increased mortality to fish. In the event that river bottom substrate does not allow installation using the vibrating technique, limited use of a percussion hammer would be required. The percussion hammer would produce underwater sound pressure levels that would potentially affect salmonid behavior and physiology. The bottom substrate is expected to be relatively soft based on results of core sampling at the site and similar substrate conditions encountered during installation of the cofferdam during construction of the RD 108 fish screen. Based on these conditions it is expected that a relatively small percussion hammer would be used and underwater sound pressure levels would be less than the 180 db pressure level resulting in damage and increased mortality to fish. The percussion hammer, if needed for cofferdam installation, would be used on an intermittent and short duration basis. Use of the percussion hammer would be minimized to the maximum extent possible, however depending on the seasonal period of cofferdam installation there is the probability that juvenile and/or adult salmonids may be in the area and potentially affected by exposure to elevated underwater sound pressure levels. Given the limited and intermittent use of the percussion hammer (expected to be hours or days), the relatively soft bottom substrate, and the rapid attenuation of sound in water, the area of potential affect is expected to be small and the magnitude of potential adverse effects is expected to be low. Given the uncertainty in the need to use the percussion hammer, the resulting sound pressure levels, the duration when the hammer is in use (expected to be hours for installation of individual sheet piles or beams), and the seasonal timing of construction activity relative to the migration of salmonids in the Action Area, the magnitude of effect can not be predicted with confidence, but is expected to be temporary and localized. Although the potential magnitude of exposure to elevated sound pressure levels and the resulting affects to salmonids is expected to be very low, limited use of the percussion hammer for cofferdam installation is identified as an adverse project effect. 3.4.6.3 Effects of Decommissioning Existing Diversions As noted in the project description, above water portions of the existing facilities will be removed, and then, in low-water conditions during summer and/or fall, pilings at the three decommissioned pumping plants will be removed by cutting the off below grade and then lifting the remaining pilings from the water with a crane. This operation will involve divers using conventional cutting tools to cut off pilings at about 2 feet (0.6 meters) below the channel bottom and lifting of pilings out of the river. This operation, which may take as many as 7-14 days per site, would result in disturbance of the sandy/silty bottom and in a small plume of suspended sediments and turbidity every time a piling is removed. This will create a localized and short term increase in suspended sediment and turbidity levels, but (as noted above) these levels will decline rapidly and will be limited to a small portion of the river channel. The sites affected by facility removal are disturbed and removal is not anticipated to affect the shoreline vegetation outside of the disturbed area. When existing pipelines are removed, this will expose small portions of the bank, which will be treated with erosion-control measures to minimize potential erosion. 3.4.6.4 Effects of Operating Screens and Diversions Long-term operation and maintenance of the fish screens would have beneficial effects on salmonids, by reducing entrainment and related mortality of juveniles. Long-term operations would not affect diversions, which would remain at environmental baseline levels. Long-term operations of the fish screen in accordance with the design criteria would contribute directly to improved protection from entrainment for juvenile salmonids and is constant with ESA protections and recovery of these species. The Proposed Project is being designed to meet CDFG and NOAA Fisheries design criteria and would be maintained and operated to meet these criteria. The technology being utilized is known and reliable. Prior to each irrigation season, RD108 would inspect and repair the facility, as needed to meet criteria, and would maintain a stock of replacement screens that can be installed rapidly in case repair is needed. Long-term operation is, therefore, expected to be reliable; periods of non-function would be brief. In addition, the high debris loads that would be associated with potential damage or clogging of the screen will generally occur outside of the irrigation season, and thus the facility is unlikely to require significant repair or replacement of equipment during the operational period. The long-term operation of the proposed fish screen would have beneficial effects on all salmonid species which utilize the Sacramento River for movement and/or foraging and rearing. In particular, the screen would substantially reduce entrainment of emigrating juvenile salmonids of all species as a result of water diversions. This is considered a substantial positive effect of the proposed project. Fish exposure to screens may cause injury and may affect swimming behavior, resulting in increased vulnerability to predation. NOAA-Fisheries and CDFG approach velocity criteria have been established to minimize changes in swimming behavior and fish contact with the screen. In addition, screens have been designed to present a non-abrasive surface to fish which may come in contact with them. The lowered approach velocities provided by the screen would offset some of these effects. Given that approach velocities to the screen would be lower than those of the existing unscreened diversion, the net effect on fish swimming behavior in the vicinity of the diversion is likely to be beneficial. The fish screen has been designed to have a smooth exterior surface and upstream and downstream transition areas that reduce or eliminate areas where juvenile salmonids are concentrated or disoriented to reduce the risk of predation, as well as to reduce or eliminate structural locations offering cover for ambush predatory fish such as bass. The net area with suitable riprap cover for predators is decreased by the project, which removes about 100 feet of riprap and replaces is with a vertical foundation and screen. Predation effects may therefore increase (due to lack of cover for juvenile salmonids) or decrease (due to increased ability of juvenile salmon to avoid the screen as a result of lower approach velocities at this diversion and due to reduced cover for predatory fish such as smallmouth bass which require cover as part of their predation strategy). For a number of reasons, these,are not quantifiable:
In addition, it is not possible to visually monitor fish movement past the screen face to determine their behavior in the vicinity of the screen without affecting their behavior and/or localized currents. Predictions of the effects of fish screens on fish passing the screen are therefore based on recent literature related to screen effectiveness. The Bonneville Power Administration has funded a number of studies of the effectiveness of fish screens installed and operated in the Columbia River Basin. For example, Blanton, McMichael, and Neitzel (1999) examined screens in the Yakama River Basin. They found that flat panel screens met NOAA-Fisheries screening criteria 95% of the time, and that failure to meet criteria was often a function of problems such as debris build up, failure to maintain screens, and loose caulk at screen boundaries. The Proposed Project incorporates screens which slide along fixed plastic-lined guides, precluding problems such as caulk failure. Blanton, McMichael, and Neitzel (1999) also noted that monitoring of fish presence and behavior near the screen was difficult due to high turbidity. Similarly, McMichael et al. (2004) found low incidences of fish screen failure to meet NOAA-Fisheries screening criteria, even for screens over twenty years old. Few controlled tests of screen ability to exclude fish have been undertaken, but Nobriga et al. (2004) tested adjacent screened and unscreened irrigation diversions in the Sacramento River and found that (a) entrainment at screened diversions was 23 fish compared to entrainment of 8501 fish at the unscreened diversion, a reduction of 99.25%. They found that the screens excluded a number of fish smaller than the size for which the screens were designed. In another recent study, Swanson, Young, and Cech (2003) evaluated stress and survival of juvenile salmonids associated with movement past fish screens under a variety of flow conditions, in the lab and then validated these laboratory studies under field conditions. They noted that fish contact rates with the face of the fish screen decreased with increasing water sweeping velocity. RD 108 has selected the Combined Pumping Plant and Fish Screen site in part because of its position along a sweeping curve in the river where there are high sweeping velocities (as evidenced by persistent scour). Siting of the facility therefore will minimize contact and injury rates. Based on these data, and the fact that there is no salmonid spawning habitat in the project reach of the river, the screens are not anticipated to entrain any eggs or larvae of salmonids and will not entrain emigrating fry or smolts, which are too large to pass through the screen mesh. No direct mortality is therefore anticipated for salmonids. Given relatively high sweeping velocities, screen contact and injury is also likely to be minimal. The facility would not alter water diversions from the Sacramento River and would, therefore, not affect instream flows, which have been identified under the EFH designation as a significant factor influencing the survival and habitat quality for Chinook salmon and other fish inhabiting the Sacramento River. The fish screen diversion facility has been designed for a capacity of 300 cfs; approximately 77 cfs less than the combined capacity of the existing diversions. Although the combined diversion capacity would be 77cfs less than the historical combined diversion capacity, the total acre-feet of water diverted each year is anticipated to remain the same as historical levels, based on recent demand studies that show current irrigation demands can be met at a delivery capacity of 300 cfs. Actual deliveries will vary annually, depending on water allocations but will not exceed contract amounts. The proposed fish screen project would not result in a change in the seasonal distribution of diversion operations. Installation of the Combined Pumping Plant/Fish Screen would increase the flexibility and reliability of operations by RD108. No flow-related effects would occur, direct or indirect. Operation of the fish screen would substantially reduce the effects of diversions on local current patterns and water velocities in the vicinity of the intake, and reduce a flow cue that may affect juvenile salmonid behavior. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||