Draft EIS_072312.pdf - Middle Fork American River Project ...

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20120723-4002 FERC PDF (Unofficial) 07/23/2012 Water Year Location Wet Above Normal Action reservoir dam May 26 May 12 Reduce the flow to a minimum of 190 cfs May 29 May 15 Reduce the flow to a minimum of 115 cfs June 1 May 18 Reduce the flow to a minimum of 65 cfs June 5 May 22 Release the minimum instream flow requirement Rubicon River below Hell Hole reservoir dam Middle Fork American River below Middle Fork interbay dam North Fork Long Canyon Creek below North Fork Long Canyon diversion dam South Fork Long Canyon Creek below South Fork Long Canyon diversion dam May 15 May 1 Increase flows from the minimum instream flow release to a minimum of 200 cfs June 21 May 16 Reduce the flow to a minimum of 150 cfs June 23 May 18 Reduce the flow to a minimum of 90 cfs June 26 May 21 Release the minimum instream flow requirement May 15 May 7 Increase flows from the minimum instream flow release to a minimum of 200 cfs May 16 May 8 Increase flows to a minimum of 450 cfs May 24 May 10 Reduce the flow to a minimum of 360 cfs May 26 May 12 Reduce the flow to a minimum of 260 cfs May 29 May 15 Reduce the flow to a minimum of 155cfs June 1 May 18 Release the minimum instream flow requirement May 15 May 1 Release a minimum of 50 cfs or inflow, whichever is less May 16 May 2 Close diversion completely May 25 May 4 Release a minimum of 35 cfs or inflow, whichever is less (can reopen diversion) May 27 May 6 Reduce the flow to a minimum of 21 cfs or inflow, whichever is less May 30 May 9 Release the minimum instream flow requirement May 15 May 1 Release a minimum of 100 cfs or inflow, whichever is less May 16 May 2 Close diversion completely May 25 May 4 Release a minimum of 70 cfs or inflow, whichever is less (can reopen diversion) May 27 May 6 Reduce the flow to a minimum of 35 cfs or inflow, whichever is less May 30 May 9 Release the minimum instream flow requirement Our recommended pulse flow measure is similar to PCWA’s proposed measure except that: • during wet years, the pulse flow we recommend would begin on May 15, and PCWA’s proposed pulse flow would begin on May 1; 326
20120723-4002 FERC PDF (Unofficial) 07/23/2012 • our recommended pulse flow measure includes additional details regarding the time of day to begin pulse flows and testing the ability to release the pulse flows during the first two pulse flow events downstream of French Meadows and Hell Hole reservoirs; and • our recommended measure specifies that, within 1 year of license issuance, PCWA would develop and implement a feasibility study to identify the maximum pulse flow between 200 and 600 cfs that can safely and reliably be released from the existing low-level outlet at Hell Hole dam. We find in section 3.3.1.2, Geologic and Soils Resources, that both pulse flow measures would restore sediment supply to the reaches downstream of the small diversion dams and improve sediment supply to the reaches downstream of Middle Fork interbay and Ralston afterbay dams. The increase in sediment supply would provide long-term channel geomorphology and aquatic and riparian ecosystem benefits to the small dam bypassed reaches. The proposed and our recommended spring pulse flows specified for all bypassed reaches in May of wet and above normal years, combined with more natural recession rates, would restore natural dynamics of riparian vegetation recruitment similar to what might occur in a comparably sized stream under unregulated conditions. The frequency of gravel bed mobilization and scour would be sufficient to maintain the channel geometry and minimize fine sediment accumulation in pools and spawning gravels. Our recommended pulse flow measure specifies that during wet years, pulse flows would begin on May 15 instead of on May 1 (PCWA’s proposal). This later initiation of pulse flows would provide more time for rainbow trout fry to emerge from the gravel prior to a planned high flow event, thus offering further protection to incubating eggs. The additional details that our recommended measure provides (regarding the time of day when pulse flows would be released), would benefit whitewater boaters by providing trip-planning information when compared to PCWA’s unspecified start of pulse flow events. Our recommended provision to conduct a feasibility study regarding the maximum pulse flow that can safely be released from Hell Hole dam would provide a reasonable balance between providing the environmental benefits of pulse flows and ensuring the safe operation of the dam is not compromised. The estimated levelized annual cost for this measure is included in the costs presented for minimum flows and would be similar to the costs associated with PCWA’s proposed pulse flow measure. We conclude that the extra protection and greater specificity of our recommended measure warrant any related minimal increased costs. 327
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41 Table 3.3.1-1. Average number of
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43 Site/Release Location Gravel Ini
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45 a Q 1 - TSR, Table G-1 (PCWA, 20
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69 Table 3.3.2-3. Hydrology for sel
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71 Exceedances and Summary Statisti
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91 Figure 3.3.2-6. Fish passage bar
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105 Location American River below M
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135 Species Name Status a Butte Cou
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145 Table 3.3.3-5. Special-status w
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147 Species Name Status Habitat Occ
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195 Figure 3.3.5-1. French Meadows
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197 Figure 3.3.5-3. Long Canyon, re
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253 Table 3.3.6-1. Archaeological a
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255 Resource Number Type a Descript
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Page 309 and 310: 279 Enhancement/Mitigation Measures
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Page 351 and 352: 321 Location Middle Fork American R
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