Revised Table V-V-3

Comparison of Alternatives by Potentially Significant Impacts

Impact 1. Multi-Year Program (Preferred) 2. Existing Program 3. No Work 4. No Herbicides 5. Modified Pajaro River Basin (Preferred) 6. Reduced Work
Geomorphology
Impact Geo-1. Sediment removal in certain locations may increase erosion downstream of the removal site. Less than Significant with BMP 1.13 Prevent Scour Downstream of Sediment Removal. Less than Significant with implementation of BMP 1.13. No effect since no sediment removal would occur. Less than Significant with implementation of BMP 1.13. Less than Significant with implementation of BMP 1.13. Less than Significant with implementation of BMP 1.13.
Impact Geo-2. Elimination of in-channel vegetation may increase sediment accumulation downstream. Less than Significant with BMP 1.14 Minimize Sediment Transport Downstream from In-Channel Herbicide Sites. Less Than Significant with implementation of BMP 1.14. No effect since no herbicide application would occur. No effect since no herbicide application would occur. Less Than Significant with implementation of BMP 1.14. Effect less likely to occur due to no herbicide use in Pajaro River Basin. Less Than Significant with implementation of BMP 1.14. Effect less likely to occur due to reduced level of work.
Impact Geo-3. Removal of vegetation may increase local erosion. Less than Significant with implementation of BMP 1.16 Minimize Local Erosion Increase from In-Channel Vegetation Removal Less Than Significant with implementation of BMP 1.16. No effect since vegetation removal would not occur. Less Than Significant with implementation of BMP 1.16. Less Than Significant with implementation of BMP 1.16. Less Than Significant with implementation of BMP 1.16. Effect less likely to occur due to reduced level of work.
Impact Geo-4. Bank protection measures can direct flows downstream, resulting in new erosion and bank instability problems at locations downstream of the repaired site. Less than Significant with implementation of BMP 1.15 Prevent Erosion Downstream of Bank Protection Sites. Less Than Significant with implementation of BMP 1.15. No effect of erosion downstream of bank protection sites since bank protection would not occur. However, without bank protection program, there would be a greater amount of bank instability. Less Than Significant with implementation of BMP 1.15. Less Than Significant with implementation of BMP 1.15. Less Than Significant with implementation of BMP 1.15. Since this alternative does not include hardscape, this effect less likely to occur.
Impact Geo-5. Removal of woody debris may reduce channel bed diversity. Less than Significant with implementation of BMP 3.9 Retain Woody Materials and Vegetation Less than Significant with implementation of BMP 3.9 No effect since removal of woody debris would not occur. Less than Significant with implementation of BMP 3.9 Less than Significant with implementation of BMP 3.9 Less than Significant with implementation of BMP 3.9. This effect less likely to occur since no work will occur in unmodified channels.
Biology
Impact Bio-1: Sediment removal and vegetation management would impact in-stream wetland and riparian vegetation Less than Significant with BMP 1.13 Prevent Scour Downstream of Sediment Removal, BMP 2.1 Minimize Vegetation Removal, BMP 3.6 Remove Sediment from One Side of Large Channels in Alternative Years, and with compensatory mitigation program for tidal, freshwater, and riparian vegetation. Less Than Significant with implementation of BMPs 1.13, 2.1, 3.6 and same compensatory mitigation program as for Preferred Alternative. Compensatory mitigation may not be implemented as soon and as coordinated as under Preferred Alternative. No effect since sediment removal and vegetation management would not occur.

Overall greater amount of vegetation expected in channels if no work is conducted although some wetland areas may convert to riparian or upland vegetation.

 Less Than Significant with implementation of BMPs 1.13, 2.1, 3.6 and same compensatory mitigation program as for Preferred Alternative. Less Than Significant with implementation of BMPs 1.13, 2.1, 3.6 and same compensatory mitigation program as for Preferred Alternative. Less Than Significant with implementation of BMPs 1.13, 2.1, 3.6 Less disturbance of vegetation due to no work occurring in unmodified channels. Compensatory mitigation program would be proportionally less than for Preferred Alternative due to lower impacts.
Impact Bio-2: The project could result in removal of heritage-sized trees Less than Significant with implementation of BMP 2.1 Minimize Vegetation Removal, BMP 2.2 Minimize Stream Access Impacts, BMP 2.8 Replace Heritage Trees, and BMP 3.9 Retain Woody Materials and Vegetation. Less Than Significant with implementation of BMPs 2.1, 2.2, 2.8 and 3.9. No effect since no bank protection would occur. Less Than Significant with implementation of BMPs 2.1, 2.2, 2.8 and 3.9. Less Than Significant with implementation of BMPs 2.1, 2.2, 2.8 and 3.9. Less Than Significant with implementation of BMPs 2.1, 2.2, 2.8 and 3.9. Effect less likely to occur since hardscape bank protection projects not included.
Impact Bio-3: Program implementation could introduce invasive plant species into native, riparian, or wetland habitat areas Less than Significant with implementation of BMPs 2.1 Minimize Vegetation Removal, 2.5 Planting, 2.6 Mulching, and 2.7 Seeding. Giant Reed Control component of compensatory mitigation reduces amount of giant reed throughout county. Less than Significant with implementation of BMPs 2.1, 2.5, 2.6, and 2.7. Without use of herbicides in upland areas in Pajaro River Basin, it will be more difficult to control yellow star thistle. Giant Reed Control component of compensatory mitigation reduces amount of giant reed throughout county. No effect from stream maintenance on introducing invasive plants species. There would be no giant reed control program. Less than Significant with implementation of BMPs 2.1, 2.5, 2.6, and 2.7. Without use of herbicides in upland areas in either basin, it will be more difficult to control yellow star thistle. Giant Reed Control component of compensatory mitigation reduces amount of giant reed throughout county but would be more difficult to implement without the use of herbicides. Less than Significant with implementation of BMPs 2.1, 2.5, 2.6, and 2.7. Without use of herbicides in upland areas in Pajaro River Basin, it will be more difficult to control yellow star thistle. Giant Reed Control component of compensatory mitigation reduces amount of giant reed throughout county. Less than Significant with implementation of BMPs 2.1, 2.5, 2.6, and 2.7. Giant Reed Control component of compensatory mitigation reduces amount of giant reed throughout county although at about one-half the level as for the Preferred Alternative.
Impact Bio-4: The cumulative impact of sediment removal and vegetation management would fragment wildlife habitat Significant

/Unavoidable even with the implementation of BMP 1.13 Prevent Scour Downstream of Sediment Removal, BMP 2.1 Minimize Vegetation Removal, BMP 3.6 Remove Sediment from One Side of Large Channels in Alternate Years, and compensatory mitigation program for tidal and freshwater wetlands and riparian vegetation due to cumulative effects throughout the county, 20 year time period, and increasing development of surrounding uplands.

 Significant

/Unavoidable

as with the Preferred Alternative.

 No effect would occur as a result of stream maintenance, since no stream maintenance would occur. Significant

/Unavoidable

as with the Preferred Alternative.

 Significant

/Unavoidable

as with the Preferred Alternative.

 Significant

/Unavoidable

as with the Preferred Alternative, however, level of impact somewhat reduced due to cessation of work in unmodified channels.

Impact Bio-5: Bank protection would cause a loss of riparian vegetation functions and values, which would cause a significant cumulative adverse impact on wildlife and fisheries habitat Less than Significant

with limitation on average annual amount of, and implementation of BMP 2.1 Minimize Vegetation Removal, BMP 2.3 Minimize Hardscape in Bank Protection Design, 2.5 Planting, BMP 3.5 Minimize Loss of Aquatic Habitat from Bank Protection Work, and BMP 3.14 Maintain or Provide Escape Cover. Additionally, the proposed 3.1 mitigation for impacts from impervious hardscape and unvegetated rock bank protection would provide a net increase in stream-side habitat over the long run.

 Less than Significant assuming individual review of bank protection projects results in redesign or mitigation and implementation of BMPs 2.1, 2.3, 2.5, 3.5, and 3.14. No direct effect since no bank protection work would be undertaken. There may be a reduction in overall bank vegetation as some loss of riparian vegetation may occur as bank erosion continues, and no program to replant banks is undertaken as with the Preferred Alternative. Less than Significant

with limitation on average annual amount of hardscape, mitigation and implementation of BMPs 2.1, 2.3, 2.5, 3.5 and 3.14.

 Less than Significant

with limitation on average annual amount of hardscape, mitigation and implementation of BMP 2.1, 2.3, 2.5, 3.5 and 3.14.

Less than Significant

with implementation of BMP 2.1, 2.3, 3.5 and 3.14. Since hardscape projects would not be included in this alternative, there would be a lower likelihood of bank protection projects resulting in a cumulative loss of riparian vegetation.

Impact Bio-6: The cumulative effects of resuming herbicide use in the Pajaro River Basin would substantially reduce the value of the habitat for wildlife Significant

/Unavoidable even with the implementation of BMP 2.1 Minimize Vegetation Removal, BMP 3.2 Minimize Impacts to Breeding Birds Via Site Assessments and Avoidance Measures, BMP 3.18 Herbicide Use in Aquatic Areas, BMP 3.19 Develop a Biodiversity Monitoring Program and compensatory mitigation program for freshwater and tidal wetlands and riparian vegetation due to the uncertainty on the amount of vegetation loss or conversion and secondary effects on cumulative fragmentation of wildlife habitat.

 No effect since this alternative will not resume herbicide use in the Pajaro River Basin. No effect since there will be no use of herbicides in either basin. No effect since there will be no use of herbicides in either basin. Without the use of herbicides, there will be a greater amount of vegetation in channels in the Santa Clara Basin, although this will also result in a greater level of disturbance every year when vegetation management is undertaken. No effect since this alternative will not resume herbicide use in the Pajaro River Basin except for upland use and to control nonnative invasive vegetation. Significant

/Unavoidable even with the implementation of BMPs 2.1, 3.2, 3.18, 3.19 and compensatory mitigation program for freshwater and tidal wetlands and riparian vegetation. This effect will be reduced compared to that of the Preferred Alternative since no work will occur in unmodified channels of the Pajaro River Basin.

Impact Bio-7: Chemical use by the District, especially for rodent control, could adversely affect non-target species Less than Significant with the implementation of BMP 2.1 Minimize Vegetation Removal, BMP 3.1 Minimize Impacts to Special-status Animals Via Site Assessments and Avoidance Measures, BMP 3.18 Herbicide Use in Aquatic Areas, BMP 3.20 Minimize Herbicide Impacts on Non-target Species, BMP 3.21 Minimize Rodent Control Impacts on Non-target Species and BMP 4.7 Herbicide Use Requirements. Less Than Significant with implementation of BMPs 2.1, 3.1, 3.18, 3.20, 3.21, and 4.7. No effect since rodenticides would not be used. Less Than Significant with implementation of BMPs 2.1, 3.1, 3.18, 3.20, 3.21, and 4.7. Less Than Significant with implementation of BMPs 2.1, 3.1, 3.18, 3.20, 3.21, and 4.7. Less Than Significant with implementation of BMPs 2.1, 3.1, 3.18, 3.20, 3.21, and 4.7. Effect slightly less likely to occur since work will not occur on unmodified channels.
Impact Bio-8: Maintenance activities could introduce invasive wildlife species Less than Significant with implementation of BMP 3.4 Mitten Crab Control Measures. Less Than Significant with implementation of BMP 3.4. No effect would occur since no disposal of sediment would occur. Less Than Significant with implementation of BMP 3.4. Less Than Significant with implementation of BMP 3.4. Less Than Significant with implementation of BMP 3.4.
Impact Bio-9: Maintenance activities could directly harm nesting species protected under the Migratory Bird Treaty Act and other statutes Less than Significant with implementation of BMP 2.1 Minimize Vegetation Removal, 3.2 Minimize Impacts to Breeding Birds Via Site Assessments and Avoidance Measures, BMP 3.9 Retain Woody Materials and Vegetation, and 3.19 Develop a Biodiversity Monitoring Program. Less Than Significant with implementation of BMPs 2.1, 3.2, 3.9, and 3.19. No impact since no vegetation management, sediment removal or minor maintenance would occur. Less Than Significant with implementation of BMPs 2.1, 3.2, 3.9, and 3.19. Less Than Significant with implementation of BMPs 2.1, 3.2, 3.9, and 3.19. Less Than Significant with implementation of BMPs 2.1, 3.2, 3.9, and 3.19. Effects would be somewhat reduced since no work would occur in unmodified channels.
Impact Bio-10: Maintenance work conducted in channels could substantially interfere with migration, spawning, incubating, or rearing habitat for native aquatic species Less than Significant with implementation of BMP 2.2 Minimize Stream Access Impacts, BMP 3.7 Salvage Native Aquatic Vertebrates from Dewatered Channels, BMP 3.9 Retain Woody Materials and Vegetation, BMP 3.11 Avoid Dewatering an Entire Isolated Stream Reach, BMP 3.12 Maintain Low-flow Fish Passage, BMP 3.13 Remove Temporary Fills as Appropriate, BMP 3.14 Maintain or Provide Escape Cover, BMP 3.15 Restore Riffle and Pool Configuration of Channel Bottom, 3.16 Restore Spawning Gravels in Work Site Areas, BMP 3.17 Reuse Sediments and Gravels As Appropriate. Less Than Significant with implementation of BMPs 2.2, 3.7, 3.9, 3.11, 3.12, 3.13, 3.14, 3.15, 3.16, and 3.17. No effect to fisheries since no stream maintenance would occur. Less Than Significant with implementation of BMPs 2.2, 3.7, 3.9, 3.11, 3.12, 3.13, 3.14, 3.15, 3.16, and 3.17. Less Than Significant with implementation of BMPs 2.2, 3.7, 3.9, 3.11, 3.12, 3.13, 3.14, 3.15, 3.16, and 3.17. Less Than Significant with implementation of BMPs 2.2, 3.7, 3.9, 3.11, 3.12, 3.13, 3.14, 3.15, 3.16, and 3.17. Effect would be somewhat reduced since no work would occur in unmodified channels.
Impact Bio-11: Temporarily suspended sediment can adversely affect aquatic or semi-aquatic species Less than Significant with implementation of BMP 1.1 Conduct Work During Low Flow Periods, BMP 1.2 Tidal Work Areas, BMP 1.3 Dewater/Bypass Water at Non-tidal Sites, BMP 1.4 Avoid Erosion When Restoring Flows, BMP 1.5 Erosion and Sediment Control Measures, BMP 1.6 Use of Wheel and Track Mounted Vehicles in Stream Bottoms, BMP 1.7 Pump/Generator Set Operations and Maintenance, BMP 1.8 Handle Sediments So As to Minimize Water Quality Impacts, BMP 1.9 Soil Stockpiles, BMP 1.12 Groundwater Management, BMP 1.14 Minimize Sediment Transport Downstream from In-channel Herbicide Sites, BMP 1.15 Prevent Erosion Downstream of Bank Protection Sites, BMP 2.2 Minimize Stream Access Impacts, and BMP 3.10 Conduct In-Channel Work During the Dry Season. Less Than Significant with implementation of BMPs 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.12, 1.14, 1.15, 2.2, 3.10. No effect since sediment removal would not occur. Less Than Significant with implementation of BMPs 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.12, 1.14, 1.15, 2.2, 3.10. Less Than Significant with implementation of BMPs 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.12, 1.14, 1.15, 2.2, 3.10. Less Than Significant with implementation of BMPs 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.12, 1.14, 1.15, 2.2, 3.10. Effect would be somewhat less likely to occur because less channel disturbance in unmodified channels and no installation of hardscape.
Impacts Bio-12, Bio-13, Bio-14 and Bio-15: Sediment removal, vegetation management, bank protection and minor stream maintenance activities would adversely affect special-status species Less than Significant with implementation of BMP 1.14 Minimize Sediment Transport Downstream from In-Channel Herbicide Sites, BMP 1.15 Prevent Erosion Downstream of Bank Protection Sites, BMP 1.3 Dewater/Bypass Water at Non-tidal Sites, BMP 1.4 Avoid Erosion When Restoring Flows, BMP 1.5 Erosion and Sediment Control Measures, BMP 2.1 Minimize Vegetation Removal, BMP 2.2 Minimize Stream Access Impacts, BMP 2.3 Minimize Hardscape in Bank Protection Design, BMP 2.4 Minimize Impacts to Special-status Plants by Avoidance Based on Site Assessment, BMP 2.5 Planting, BMP 2.6 Mulching, BMP 2.7 Seeding, BMP 3.1 Minimize Impacts to Special-status Animals Via Site Assessments and Avoidance Measures, BMP 3.2 Minimize Impacts to Breeding Birds Via Site Assessments and Avoidance Measures, BMP 3.3 Avoid Serpentine Habitat, BMP 3.6 Remove Sediment from One Side of Large Channels in Alternate Years, BMP 3.7 Salvage Native Aquatic Vertebrates from Dewatered Channels, BMP 3.9 Retain Woody Materials and Vegetation, BMP 3.10 Conduct In-Channel Work During the Dry Season, BMP 3.11 Avoid Dewatering an Entire Isolated Stream Reach BMP 3.12 Maintain Low-flow Fish Passage, BMP 3.15 Restore Riffle and Pool Configuration of Channel Bottom, BMP 3.16 Restore Spawning Gravels in Work Site Areas, BMP 3.18 Herbicide Use in Aquatic Areas, BMP 3.20 Minimize Adverse Effects of Herbicides on Non-target Species, BMP 4.5 Vehicle and Equipment Cleaning, BMP 4.7 Herbicide Use Requirements, BMP 6.1 Spill Prevention, BMP 6.4 Vehicle and Equipment Fueling, and BMP 6.5 Vehicle and Equipment Maintenance. Less Than Significant with implementation of BMPs 1.14, 1.15, 1.3, 1.4, 1.5, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 3.1, 3.2, 3.3, 3.6, 3.7, 3.9, 3.10, 3.11, 3.12, 3.15, 3.16, 3.18, 3.20, 4.5, 4.7, 6.1, 6.4, and 6.5.

 No effects since no stream maintenance work will occur. Less Than Significant with implementation of BMPs 1.14, 1.15, 1.3, 1.4, 1.5, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 3.1, 3.2, 3.3, 3.6, 3.7, 3.9, 3.10, 3.11, 3.12, 3.15, 3.16, 3.18, 3.20, 4.5, 4.7, 6.1, 6.4, and 6.5. Less Than Significant with implementation of BMPs 1.14, 1.15, 1.3, 1.4, 1.5, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 3.1, 3.2, 3.3, 3.6, 3.7, 3.9, 3.10, 3.11, 3.12, 3.15, 3.16, 3.18, 3.20, 4.5, 4.7, 6.1, 6.4, and 6.5. Less Than Significant with implementation of BMPs 1.14, 1.15, 1.3, 1.4, 1.5, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 3.1, 3.2, 3.3, 3.6, 3.7, 3.9, 3.10, 3.11, 3.12, 3.15, 3.16, 3.18, 3.20, 4.5, 4.7, 6.1, 6.4, and 6.5. Effect would be somewhat reduced since no work would occur in unmodified channels.
Cultural
Impacts Cul-1 and Cul 2: Disruption of Cultural Resources or Native American Burials Less than Significant with implementation of BMP 7.1 Discovery of Cultural Remains or Historical Artifacts and BMP7.2 Review of Projects with Native Soil Protocol for Unexpected Discovery of Archaeological or Cultural Materials and Protocol for Discovery of Native American Burials. Less than Significant with implementation of BMPs 7.1 and BMP7.2 Protocol for Unexpected Discovery of Archaeological or Cultural Materials and Protocol for Discovery of Native American Burials. No effect since no disruption of previously undisturbed native soil would occur. Less than Significant with implementation of BMPs 7.1 and BMP7.2 Protocol for Unexpected Discovery of Archaeological or Cultural Materials and Protocol for Discovery of Native American Burials. Less than Significant with implementation of Less than Significant with implementation of BMPs 7.1 and BMP7.2 Protocol for Unexpected Discovery of Archaeological or Cultural Materials and Protocol for Discovery of Native American Burials. Effect less likely to occur since undisturbed cultural materials or burials more likely to occur at unmodified channels where work will be excluded under this alternative.
Public Safety
Impact WQ-1. Erosion of mercury containing sediment. Less than Significant with implementation of BMP 1.10 Avoid Exposing Soils with High Mercury Levels. Less than Significant with implementation of BMP 1.10. No effect from stream maintenance since no maintenance work would occur. However, no removal or sealing of mercury laden soils would occur as a result of maintenance activities. Less than Significant with implementation of BMP 1.10. Less than Significant with implementation of BMP 1.10. Less than Significant with implementation of BMP 1.10.