|
|
The alternatives analysis focuses on the ways that the long-term, cumulative impacts of routine maintenance could be reduced. The proposed project is adoption of the Stream Maintenance Program (SMP) and implementation of its work performance protocol and programmatic mitigation. The proposed SMP is characterized as the Multi-Year Program (Preferred Alternative). The Existing Program Alternative represents the District not adopting the SMP and continuing the current practice of routine maintenance on an annual basis. The No Work Alternative would eliminate all maintenance in streams and canals by the District within its jurisdiction. The Reduced Work Alternative would eliminate work in unmodified channels, and does not include hardscape bank protection. The No Herbicides Alternative and the Modified Pajaro River Basin Alternative reduce the amount of area treated with herbicides.
The main differences between the alternatives are: 1) the amount of flood protection provided; 2) the amount of stream vegetation affected; and 3) the amount of area treated with herbicide. Other areas of potential impact do not vary appreciably among alternatives. As with the Preferred Alternative, other potential impacts can be avoided or reduced to insignificance with the same BMPs or a version of the compensatory mitigation program incorporated in the project.
The District could have considered maintenance of streams and canals as an effort to maintain facilities in their originally constructed condition with no further need to provide mitigation than what was originally provided. However, to be consistent with its mission to protect and enhance natural stream resources, to resolve controversy, and to provide greater assurance in obtaining permits, the District has decided under the SMP to provide compensatory mitigation for wetland and riparian impacts which cannot be avoided during the course of routine maintenance.
This EIR does not consider redesign of the channel, limiting or modifying upstream land uses, or watershed management as alternatives to reducing the impacts of stream maintenance. While the need for maintenance and hence the wetland and riparian impact of maintenance in some streams could be reduced by changing the channel condition, preliminary investigations show the necessary design and construction work are beyond the scope of routine maintenance and the proposed SMP. Additionally, the built-up urban environment is a major constraint to implementing either engineered or geomorphic alternatives. The District will be considering geomorphic options in its future flood protection designs. Control of land uses and watershed management are not entirely within the responsibility of the District. The District is participating in other efforts to encourage more compatible land use and watershed management to reduce effects to streams. In the meantime, maintenance of the streams and canals will be necessary, and the SMP is intended to reduce the environmental effects of such activities while continuing to provide flood protection and water supply benefits. Watershed level sediment and storm water management could also reduce the need for maintenance on some streams. The District is currently involved in such cooperative programs, but the benefits to maintenance will only be realized in the long term.
A. SCOPE OF ANALYSIS
The proposed project is the Stream Maintenance Program for Routine Maintenance Activities on District facilities and is referred to as the Multi-Year Program. The SMP would apply BMPs to avoid or minimize impacts and a regional mitigation program to compensate for unavoidable impacts at individual maintenance sites. The EIR examines a series of alternatives to meet statutory requirements and to evaluate the possibility that the effects of the proposed project could be lessened or avoided.
1. Requirements of CEQA
Section 15126 (6)(b) of the CEQA Guidelines states: "Because an EIR must identify ways to mitigate or avoid the significant effects that a project may have on the environment (Public Resources Code Section 21102.1), the discussion of alternatives shall focus on alternatives to the project or its location which are capable of avoiding or substantially lessening any significant effects of the project, even if these alternatives would impede to some degree the attainment of the project objectives, or would be more costly". Thus the purpose of this analysis is to determine if there are alternatives that reduce the long-term or cumulative environmental impacts that would occur as a result of the proposed project. There is no way to reduce the need for ongoing maintenance, especially in-stream sediment removal, as much of the cause of the sediment is beyond the District's control.
CEQA Guidelines also require EIRs to analyze off-site alternatives. However, CEQA Guidelines state that if the District, as Lead Agency, concludes that no feasible alternative locations exist, it must disclose the reasons for this conclusion, and should include the reasons in the EIR. In the case of the proposed program, no suitable off-site (outside District jurisdiction) alternatives exist. The objective of the proposed program is to maintain established District facilities. The location of the channel sediment, vegetation management and bank failure problems is determined by the channel history, watershed land use, and fluvial geomorphology, therefore maintenance cannot be practically accomplished at a different location.
As required by CEQA, alternatives are compared to the Multi-Year Program (Preferred Alternative), as described in detail in Chapter II. Refer to Tables V-1 and V-2 which provide information for each alternative. The proposed project includes sediment removal, vegetation management, bank protection, and minor work activities throughout the District's jurisdiction (and below the 1000-foot elevation contour).
2. Maintenance Baseline
One approach to determining the impacts of maintenance to stream resources could be to assume that maintenance is an activity which preserves the original design of a flood protection project, and therefore does not have any impacts greater than those originally caused during construction of the project. Some existing and proposed regulations even suggest that maintenance of flood protection facilities should be considered differently than original fill caused by a project. This approach to impact analysis is referred to herein as the Maintenance Baseline and is based on existing or proposed regulations which state that mitigation may not be necessary for these types of activities.
In referencing these regulations, one could come to the conclusion that the following maintenance activities would not require mitigation: sediment removal in tidal areas, concrete-lined channels and in-channel siltation basins; bank protection; and vegetation management.
Under the Corps' Nationwide Permit (NWP) 31 for Maintenance of Existing Flood Control Facilities, routine maintenance activities that are performed on a regular basis may not require mitigation. NWP 31 includes language which states, "In determining the need for mitigation, the DE [Corps' District Engineer] will consider the following factors: any original mitigation required, the current environmental setting, and any adverse effects of the maintenance project that were not mitigated in the original construction" (Federal Register, December 13, 1996, B.31). A Corps guidance letter on NWP 31 states, "As a general rule, normal cyclic maintenance of flood protection channels, even where vegetation is removed, is viewed as involving no more than minimal adverse environmental effects, since regular, cyclical maintenance activities cause only a temporary loss of wetland functions and values . . . After the establishment of the maintenance baseline and the requirement of any needed mitigation, maintenance activities that are part of subsequent cyclical maintenance of flood protection facilities, and that do not exceed the limits of the maintenance baseline, do not require mitigation (Hess, 1997).
One could interpret NWP 31 as allowing routine maintenance work in tidal areas to be permitted without requiring additional mitigation as long as the maintenance work has been conducted on a regular basis, and the original construction of the project was after 1970. The assumption is that since all projects constructed after 1970 were reviewed under CEQA, then either mitigation was offered for the original construction, or the impacts were evaluated at that time as not significant. Almost all of the tidal portions of the District's flood protection facilities have been constructed or modified after 1970. This standard would only apply to maintenance work in tidal areas because, currently, the Corps only regulates sediment removal in tidal areas.
Staff of the San Francisco Bay Region of the Corps Regulatory Branch has indicated that they may not agree with this interpretation of NWP 31. Indeed, in 1997, this office approved use of NWP 31 for a District sediment removal project on Jones and Morey Creeks, and a condition of that approval was that these projects be incorporated into the SMP for consideration of impacts and mitigation.
A Regional General Permit currently being proposed by the Corps and San Francisco Regional Water Quality Control Board also suggests that mitigation may not be necessary for sediment removal in concrete channels, vegetation management and bank protection. This proposed regulation, referred to as the Minimal Threat Flood Control Channel Maintenance Activities permit, would apply to major flood protection districts in the San Francisco Bay area, and is expected to be enacted sometime in the Year 2001. The Regional General Permit would allow sediment and debris removal in concrete lined channels and in-channel siltation basins, vegetation management, maintenance of structures, and bank protection. According to this proposed Regional General Permit, with implementation of the appropriate BMPs, these activities typically would not require mitigation. Prohibitions under the proposed regulation include a condition that there should be no permanent loss or significant temporal loss of wetland or riparian habitat in terms of acreage, function or value, however, these conditions have not been defined yet. A condition for bank protection activities is that the structure be no longer than 500 feet in length.
The San Francisco Bay Region of the RWQCB may not agree with the Maintenance Baseline interpretation of either NWP 31 or the Regional General Permit. Staff of the RWQCB have told the District that they expect mitigation for maintenance impacts to wetlands even under NWP 31, and they do not believe the Regional General Permit is meant to cover large maintenance projects such as those commonly undertaken by the District.
The District considered the Maintenance Baseline approach during development of the SMP. However, eventually the District decided to provide mitigation for maintenance impacts to stream vegetation and developed the one-time accounting approach (see explanation in One-Time Accounting Method for Stream Vegetation Impacts in Chapter IVB) to provide permanent mitigation for temporary but repetitive impacts which are unique to maintenance activities. To be consistent with its mission to protect and enhance natural stream resources, to resolve controversy, and to provide greater assurance in obtaining permits, the District has decided under the SMP to provide compensatory mitigation for wetland and riparian impacts which cannot be avoided during the course of routine maintenance. All the alternatives evaluated below likewise use this threshold for determining impacts from maintenance.
3. Effects to be Avoided
As described in the environmental analysis, the direct impacts of the individual maintenance projects under the proposed maintenance program can be mitigated to insignificance through application of the BMPs and the implementation of the compensatory mitigation program. The proposed project has the potential for significant cumulative effects to wildlife in streams throughout the county due to fragmentation of habitat by repetitive maintenance activities over the next twenty years. There is also a potential for either a reduction or change in type of stream vegetation in the Pajaro River Basin due to the resumption of herbicides.
With the exception of the No Work Alternative, the Multi-Year Program and all the alternatives will have no adverse effect or will use the same set of BMPs to reduce any potential impacts to a level of less than significant for the following: consistency with land use and policies, aesthetics, air quality, odor, noise, and public services (excluding flood protection). Therefore, these potential impacts are not discussed further in this chapter except for some clarification under the No Work Alternative.
The alternatives analysis focuses on the ways that long-term, cumulative impacts to geomorphology, biology, cultural resources, and public safety could be reduced by reducing the level or changing the method of recurring maintenance disturbance.
B. ALTERNATIVES EVALUATED IN EIR
The following slate of alternatives meets the requirements of CEQA and includes consideration of the current maintenance practices. When screening potential alternatives for this program, the District initially considered multiple combinations of design methods, service levels, impact analysis, mitigation packages, and approaches to environmental review and permitting. Over one dozen combinations were examined in further detail, screened for feasibility, and evaluated as to whether they responded to the program objectives, CEQA requirements and comments from agencies and internal and external stakeholders. The preferred alternative is summarized first and followed by the five alternatives which were identified for analysis under the EIR because they meet all or most of the program purposes. Table V-1 defines the basic elements of each alternative.
Background Information on Initial vs. Long Term Impacts to Stream Vegetation. When comparing impacts to stream vegetation from different alternatives, DEIR considers both initial impacts and long term impacts. Because some alternatives will include the substitution of one type of vegetation management for another, there will be a long term change and seasonal changes in the amount of vegetation present in the channels. Table V-2 compares alternatives for levels of initial and long term impacts on vegetation. Initial impacts assess the general level of vegetation removal that will occur in the first few years of implementing the new alternative. Long term impacts assess the general level of vegetation removal that will occur after the new alternative has been implemented for several years. The difference between these two amounts indicates what change in the amount of vegetation would occur either year round or seasonally as a result of implementing a new technique for vegetation management.
The different methods of vegetation management are implemented in different times of the year, therefore, they result in a seasonal difference in vegetation being present in the channel. Removal of woody saplings by hand is undertaken July 1 through March 1. Hand removal and mechanical mowing of herbaceous wetland vegetation is undertaken in November and December. This is because herbaceous vegetation resprouts after hand or mechanical treatment, and to provide the best clearance for flood protection, it is better to cut this material directly before the flooding season. Herbicide treatment is undertaken in the channel from July 1 through October 15. Furthermore, herbicides are more effective at killing plants and preventing them from regrowing than hand removal or mechanical methods of managing vegetation, therefore, herbicides result in less vegetation being present in the channels year round.
As a result of the combination of the effectiveness of herbicides and the different seasons that different methods are implemented, two types of biological impacts can occur when switching from one method to another. Over time, for areas which will switch from a hand removal method to herbicides, there will be less wetland vegetation present in the channel year round, thus less wildlife habitat especially during the summer breeding season. On the other hand, after the first few years under herbicide treatment, there will be less vegetation removed every year, therefore there will be less annual disturbance of resident wildlife. Herbicide spraying tends to have a gradual effect on vegetation whereas hand and mechanical methods of removing vegetation tend to be more immediate and noisy acts of disruption to resident wildlife.
For areas which switch from herbicide use to hand removal or mowing, there will be more vegetation and therefore more wildlife habitat present in the channels from the early winter period through the summer breeding season. On the other hand, the amount of stream vegetation which will be annually removed will increase, estimated here to be twice the amount in area, and the actual act of removing vegetation will be more disruptive to resident wildlife. This EIR assumes that the seasonal presence of a greater amount of vegetation has greater biological benefits than the adverse disruption caused by mechanically removing a larger amount of vegetation later in the year.
Using the one-time accounting method (see Chapter IVB) to assess the impacts to stream vegetation, the only area which will show a change in impact amounts due to the effects of switching from a non-herbicide use to a herbicide use (or reverse) will be those stream reaches where only vegetation management is undertaken, not in stream reaches where sediment removal is also undertaken. This is why the change is stream vegetation impacts in Table V-2 is not exactly doubled or halved between short term and long term impacts.
As described further in Chapter IVB, it is likely that not every channel will respond in this way from conversion to herbicide use. In some channels, it is more likely that the actual amount of vegetation will not change but the type of vegetation will change.
Table V-3 compares alternatives to the Multi-Year Program according to the impacts found to be significant or potentially significant. Table V-4 compares costs of the alternatives.
1. Multi-Year Program (Preferred Alternative)
The Multi-Year Program, which is the Preferred Alternative and is described in detail in the SMP, includes sediment removal, vegetation management, bank protection and minor associated work. Projected levels of work are based on historical levels with minor adjustments made for foreseeable future changes. The extent of work under the Multi-Year Program would be 61 miles of sediment removal and 258 miles of channel vegetation management. The extent of maintenance is defined as the total length or area on which stream maintenance will repeatedly take place.
Initial impacts to stream vegetation would consist of 116 acres of freshwater wetlands, 30 acres of tidal wetlands and 78 acres of riparian vegetation. Herbicides would be used for vegetation management in both the Santa Clara Basin and Pajaro River Basin. Over time, with the use of herbicides in the Pajaro River Basin where hand and mechanical methods are currently used, it is projected there would be seasonally less wetland vegetation in the channels of the Pajaro River Basin. Thus, the long term level of impacts to stream vegetation would be 114 acres of freshwater wetlands, 30 acres of tidal wetlands, and 77 acres of riparian vegetation. However, the mitigation program is based on the level represented by the initial impacts which are greater rather than the long term impacts in order to compensate for the gradual loss of vegetation in the sections of the Pajaro River Basin where vegetation management work is undertaken without sediment removal.
BMPs as incorporated in the SMP would avoid or reduce many impacts. A compensatory mitigation program for impacts to stream vegetation from the sediment removal and channel vegetation management activities would consist of restoring 30 acres of tidal wetland, creating 14 acres of freshwater wetlands, preserving and enhancing 920 to 1210 acres of stream and watershed, and control of 125 acres of giant reed. Refer to SMP, Chapter V for details.
The bank protection work would include both hardscape and softscape designs with a programmatic exchange of mitigation between designs which tend to limit biotic potential and those which tend to retain it. Refer to this EIR Chapter 2, Project Description and Appendix E of the SMP for details on the mitigation program for bank protection activities.
This programmatic EIR would serve as the major vehicle for evaluating future work under CEQA, and projects are expected to be covered by 10-year permits.
2. Existing Program Alternative
The Existing Program Alternative represents a continuation of current maintenance practices with minor foreseeable future changes, and therefore, it is one form of the No Project Alternative as defined under CEQA. The Existing Program Alternative includes the same amount of sediment removal, vegetation management, bank protection and minor activities as the Multi-Year Program. This alternative will not include the use of herbicides in the Pajaro River Basin since that is not the existing practice.
The Existing Program Alternative will continue to affect 116 acres of freshwater wetlands, 30 acres of tidal wetlands, and 78 acres of riparian vegetation, and the amount of stream vegetation will not change over the long term.
As with the Multi-Year Program, current BMPs will be used and new best management practices will be developed, as new information becomes available.
Each year, the projected maintenance projects will be reviewed under CEQA. Projects will be reviewed as categorical exemptions where appropriate, or may be combined into packages for review under either Initial Studies/Negative Declarations, or EIRs, depending on their potential for significant impacts. The District will apply for permits each year from the various regulatory agencies, qualifying for exemptions, regional permits, and Corps nationwide permits whenever possible. In addition, as the need for new projects is discovered outside of the regular annual planning process, additional CEQA reviews and permit applications will be prepared. Because of the amount of time it will take each year to review sets of projects under CEQA and apply for multiple permits, the amount of maintenance work completed on an annual basis may actually be somewhat reduced compared to the Multi-Year Program.
The requirements for mitigation will be negotiated each year and mitigation projects will be developed or managed individually rather than as a program. It is assumed under this alternative, that during negotiation of annual permits, the baseline for assessing impacts and estimating mitigation would be the same as for the Multi-Year Program, with the inclusion of the one-time accounting method. That is, mitigation would be provided for all impacts to tidal wetlands, freshwater wetlands, and riparian vegetation from sediment removal and vegetation management, but over the years, new mitigation would not be offered for repeated activities in the same channel reach. Over time, compensatory mitigation would consist of the same four components as described for the Multi-Year Program, but because mitigation is negotiated each year, the implementation may be more spread out and not as coordinated.
Bank protection projects would be designed, reviewed under CEQA, permitted, and installed on an individual basis. It would be more difficult to exchange mitigation credit between different types of bank protection designs if they are not managed as a program. Cumulative impact analysis would be more difficult if not managed as a program.
Under the Existing Program Alternative, it would be more difficult to reassess cumulative impacts of stream maintenance after several years since projects are evaluated on an annual and case-by-case basis only.
The same amount of flood protection would be provided as under the Multi-Year Program, however, because of the greater expense of the hand and mechanical methods compared to herbicide use for vegetation management, average annual costs would increase approximately $2 million or 19% compared to the Multi-Year Program (Table V-4).
3. No Work Alternative
The No Work Alternative discontinues all maintenance of streams, canals and associated District facilities, and therefore, it is the other form of the No Project Alternative as defined under CEQA. Geomorphic adjustments would occur. If maintenance ceased, the stream channels would develop a more meandering pattern and the evolution of a low flow channel would begin. Tidal channels would fill in with sediment and the channel would change alignment. Establishment of a fully geomorphic alignment would be constrained by development along the creek and by the maintenance of property, homes, roads and bridges by individuals and by other agencies. None of the impacts identified in Chapter IV.A. Geomorphology would occur, because these impacts are directly related to maintenance work.
Over time, these facilities would fill in with more sediment and in many cases with more vegetation. The reduction in short-term, recurring disturbance would allow a greater amount of wetland to become established in channels and a greater opportunity for riparian forest to establish on sandbars. In some channels, however, the existing maintenance program is creating conditions conducive to wetland vegetation, and at these locations, sediment buildup would reduce the amount of stream vegetation, or eventually shift it towards more riparian or upland species rather than wetland. Establishment of a fully-geomorphic alignment would be constrained by the development along the creek and by the maintenance of property, homes, roads and bridges by individuals and by other agencies.
No impacts to stream vegetation by the District would occur as the result of maintenance under this alternative, therefore, no mitigation would occur. Without maintenance activities, there would be no impacts as a result of work to aesthetics, odor, noise or public services (excluding flood protection).
The No Work Alternative would cause significant threat to flooding to areas
that have been removed from the flood plains as a result of flood protection
projects constructed by the District. The main reason for the proposed project
is to provide adequate flood protection, which would not be provided if this
alternative was implemented. The No Work Alternative would be inconsistent with
policies of the various cities and county regarding the provision of flood protection
and public safety. The estimated number of parcels and acreage that would be
impacted are shown below:
| Land Use | Number of Parcels | Acres |
| Residential | 77,262 | 11,900 |
| High-density residential | 2,733 | 1,612 |
| Public | 432 | 674 |
| Commercial | 2,624 | 3,206 |
| Industrial | 1,796 | 6,158 |
| Agricultural | 358 | 4,574 |
| Vacant and open space | 1,560 | 3,521 |
|
Total |
86,765 | 31,645 |
Source: Information from the District's GIS/WWMM dated March 20, 2001
Owners of properties that are in a flood plain are required to maintain a flood insurance policy for each property. Depending on the location, the flood insurance policy for a typical residential property can cost a property owner from $300 to $1,000 a year. Using the lower flood insurance rate of $300/year, the potential flood insurance cost to residential properties alone from the No Work Alternative is approximately $23.2 million a year.
4. No Herbicides Alternative
The No Herbicides Alternative assumes no use of herbicides in routine stream or canal maintenance. Instead, herbicide treatment of vegetation in the Santa Clara Basin will be replaced by mechanical and hand methods in those areas in which herbicides are currently used. As is currently the practice, no herbicides will be used in the Pajaro River Basin. The No Herbicides Alternative includes the same amount of sediment removal, vegetation management, bank protection and minor activities as the Multi-Year Program.
Initial impacts to stream vegetation would consist of 116 acres of freshwater wetlands, 30 acres of tidal wetlands and 78 acres of riparian vegetation. Over time, with the cessation of herbicide use in the Santa Clara Basin, there would be more vegetation present in the channel, and long term impacts to stream vegetation would be 142 acres of freshwater wetlands, 31 acres of tidal wetlands, and 109 acres of riparian vegetation. The biological impacts would be reduced under this alternative, because vegetation would be trimmed back instead of being killed, allowing wildlife cover, roosting, feeding and nesting opportunities for a period of a few months every year before it is removed. Vegetation would be removed by mechanical and hand methods later in the season than if it were to be removed by herbicide use, thus providing habitat for migratory birds that arrive before work commences. This is a beneficial effect to biological values. On the other hand, a greater amount of vegetation will be removed by more disruptive methods every year, although it will occur after the breeding season.
The same BMPs would be applied except for those which are relevant only to herbicide use. The mitigation program would be the same as for the Multi-Year Program. The approach to multi-year CEQA review and permits would be the same as under the Multi-Year Program. The same amount of flood protection would be provided as under the Multi-Year Program, however, because of the greater expense of the hand and mechanical methods compared to herbicide use for vegetation management, average annual costs would increase approximately $8 million or 66% compared to the Multi-Year Program (Table V-4).
5. Modified Pajaro River Basin Alternative
The Modified Pajaro River Basin Alternative is similar to the proposed Multi-Year Program except that it will not include the use of herbicides in stream channels of the Pajaro River Basin unless they are for the control of non-native, invasive plants. Instead, hand and mechanical methods will continue to be used to control vegetation in the Pajaro River Basin stream channels. Herbicides will be used in adjacent upland areas in the Pajaro River Basin, and in channels, canals and associated upland areas in the Santa Clara Basin.
The Modified Pajaro River Basin Alternative includes the same amount of sediment removal, vegetation management, bank protection and minor activities as the Multi-Year Program.
Initial impacts to stream vegetation would consist of 116 acres of freshwater wetland, 30 acres of tidal wetland, and 78 acres of riparian vegetation and this amount would not change over time since there is no conversion of vegetation management types in the channel. This would result in a greater amount of in-channel vegetation in the Pajaro River Basin than under the Multi-Year Program and would provide a beneficial effect to the streamside habitat because vegetation would be trimmed back instead of being killed, allowing wildlife cover, roosting, feeding and nesting opportunities. This would also result in less streamside habitat fragmentation caused by vegetation management activities. However, the annual amount of stream vegetation removed in the Pajaro River Basin would be greater than for the Multi-Year Program over the long term, and the method would be temporarily more disruptive to resident wildlife.
The BMPs, compensatory mitigation, and approach to multi-year CEQA review and permits would be the same as under the Multi-Year Program. The same amount of flood protection would be provided as under the Multi-Year Program, however, because of the greater expense of the hand and mechanical methods compared to herbicide use for vegetation management, average annual costs would increase approximately $2 million or 17% compared to the Multi-Year Program (Table V-4).
6. Reduced Work Alternative
The Reduced Work Alternative would reduce the overall amount of routine stream maintenance work. Sediment removal and vegetation management would no longer take place in unmodified channels except 100 feet upstream and downstream of bridges or road crossings as needed and at stream gages, outfalls, trash racks and other structures as described under the minor work activities in Chapter II, Program Description. Unmodified channels are channels in which no modifications have been made by the District for flood protection purposes. Unmodified channels may be in a natural condition with stream meanders and trees lining the bank. However, some unmodified channels have been altered by historical land uses and in appearance, are more like a ditch than a natural channel. Maintenance activities in canals would be the same as under the Multi-Year Program. Herbicide use would resume in the Pajaro River Basin. The extent of work under the Reduced Work Alternative would be 58 miles of sediment removal and 190 miles of channel vegetation management (Figure V-1).
This alternative would not include any hardscape designs in the bank protection program. The hardscape designs excluded are those defined in Chapter II as Bank Protection Techniques That Tend to Limit Biotic Potential. Bank Protection Techniques That Tend to Retain Biotic Potential (as defined in Chapter II) are included in this alternative. The number and length of sites which can be suitably designed with softscape in the future is not known, therefore the only prediction which can be made about the amount of future bank protection under this alternative is that it will average less than 2500 feet per year. Other stream bank projects will be completed under individual CEQA permits. None of the geomorphic or biological impacts related to hardscape bank protection would result from this alternative, thus resulting in beneficial effects.
Initial impacts to stream vegetation would consist of 105 acres of freshwater wetland, 30 acres of tidal wetland, and 39 acres of riparian vegetation. The level of long term impacts would be slightly reduced to 103 acres of freshwater wetland, 30 acres of tidal wetland and 38 acres of riparian vegetation
The BMPs and approach to multi-year CEQA review and permits would be the same as under the Multi-Year Program. The compensatory mitigation program would be reduced due to the reduced impacts, and would consist of restoring 30 acres of tidal wetlands, creating 14 acres of freshwater wetlands, preserving and enhancing 909 to 1199 acres of streams and watersheds, and control of 72 acres of giant reed.
Routine stream maintenance activities are performed in unmodified creeks to preserve the existing flood conveyance capacity of these creeks. These activities are also conducted in response to requests from the public, both individuals and neighborhoods, that the District help protect property and public roads from the threat of flooding. Since these are unmodified creeks, information is not available to evaluate the level of protection afforded by the maintenance work. Implementation of this alternative is expected to result in increased flooding in areas adjacent to the unmodified channels which are excluded.
Average annual costs would decrease approximately $500,000 or 4% compared to the Multi-Year Program (Table V-4).
There are two alternatives that qualify for the Environmentally Superior alternative
under CEQA: the No Work Alternative and the Reduced Work Alternative. Both of
these alternatives result in less impacts to stream vegetation and would not
contain hardscape bank protection. Because the No Work Alternative would not
provide flood protection, and would therefore attain none of the District's
objectives, the Environmentally Superior Alternative is the Reduced Work Alternative.
Table V-1
Definition of Alternatives
| Alternative | Amount of Work
(extent of channel maintenance) |
Initial Impacts to Stream Vegetation | Herbicide Use in Santa Clara Basin | Herbicide Use in Pajaro Basin |
| 1. Multi-Year Program
(Preferred) |
Sediment removal 61 miles
Channel veg. management 258 miles |
Freshwater Wetlands 116 acres
Tidal Wetlands 30 acres Riparian Vegetation 78 acres |
Yes | Yes |
| 2. Existing Program | Sediment removal 61 miles
Channel veg. management 258 miles |
Freshwater Wetlands 116 acres
Tidal Wetlands 30 acres Riparian Vegetation 78 acres |
Yes | No |
| 3. No Work | Sediment removal 0 miles
Channel veg. management 0 miles |
None | No | No |
| 4. No Herbicides | Sediment removal 61 miles
Channel veg. management 258 miles |
Freshwater Wetlands 116 acres
Tidal Wetlands 30 acres Riparian Vegetation 78 acres |
No | No |
| 5. Modified Pajaro River Basin | Sediment removal 61 miles
Channel veg. management 258 miles |
Freshwater Wetlands 116 acres
Tidal Wetlands 30 acres Riparian Vegetation 78 acres |
Yes | No in channels, Yes in uplands |
| 6. Reduced Work | Sediment removal 58 miles
Channel veg. management 190 miles |
Freshwater Wetlands 105 acres
Tidal Wetlands 30 acres Riparian Vegetation 39 acres |
Yes, less than SMP | Yes, less than SMP |
Table V-2
Alternatives Comparison of Initial Stream
Vegetation Impacts
|
Impacts to Stream
Vegetation from |
|||||||
|
Initial Impacts
|
Long Term Impacts
|
||||||
| Freshwater Wetlands | Tidal Wetlands | Riparian Vegetation | Freshwater Wetlands | Tidal Wetlands | Riparian Vegetation | ||
| 1. Multi-Year Program (Preferred) | 116 | 30 | 78 | 114 | 30 | 77 | |
| 2. Existing Program | 116 | 30 | 78 | 116 | 30 | 78 | |
| 3. No Work | 0 | 0 | 0 | 0 | 0 | 0 | |
| 4. No Herbicides | 116 | 30 | 78 | 142 | 31 | 109 | |
| 5. Modified Pajaro River Basin | 116 | 30 | 78 | 116 | 30 | 78 | |
| 6. Reduced Work | 105 | 30 | 39 | 103 | 30 | 38 | |
Source: SCVWD 3/01
Table V-3
Comparison of Alternatives by Impacts
| Impact | 1. Multi-Year Program (Preferred) | 2. Existing Program | 3. No Work | 4. No Herbicides | 5. Modified Pajaro River Basin | 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. | 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 hardscape and implementation of BMP 2.1 Minimize Vegetation Removal, BMP 2.3 Minimize Hardscape in Bank Protection Design, BMP 3.5 Minimize Loss of Aquatic Habitat from Bank Protection Work, and BMP 3.14 Maintain or Provide Escape Cover. [may need revision once Jose redefines bank prot program.] |
Less than Significant assuming individual review of bank protection projects results in redesign or mitigation and implementation of BMPs 2.1, 2.3, 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 and implementation of BMPs 2.1, 2.3, 3.5 and 3.14. |
Less than
Significant
with limitation on average annual amount of hardscape and implementation of BMP 2.1, 2.3, 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. | 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 Protocol for Unexpected Discovery of Archaeological or Cultural Materials and Protocol for Discovery of Native American Burials. | Less than Significant with implementation of 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 Protocol for Unexpected Discovery of Archaeological or Cultural Materials and Protocol for Discovery of Native American Burials. | Less than Significant with implementation of Protocol for Unexpected Discovery of Archaeological or Cultural Materials and Protocol for Discovery of Native American Burials. | Less than Significant with implementation of 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. |
|
ALTERNATIVES V-23 | ||||||||||||
| Table V-4
Cost Comparison of Alternatives | ||||||||||||
| 1. MULTI-YEAR (PROPOSED) ALTERNATIVE | 2. NO PROGRAM (EXISTING) | 3. NO WORK ALTERNATIVE | 4. NO HERBICIDE ALTERNATIVE | 5. MODIFIED PAJARO BASIN ALTERNATIVE | 6. REDUCED WORK ALTERNATIVE | |||||||
| Average | 20-Year Cost | Average | 20-Year Cost | Average | 20-Year Cost | Average | 20-Year Cost | Average | 20-Year Cost | Average | 20-Year Cost | |
| Santa Clara Basin | $ | $ | $ | $ | $ | $ | $ | $ | $ | $ | ||
| Sediment Removal | $2,768,000 | $55,360,000 | $2,768,000 | $55,360,000 | 0 | 0 | $2,768,000 | $55,360,000 | 2,768,000 | 55,360,000 | $2,729,178 | 54,583,560 |
| Vegetation Management | $1,290,475 | $25,809,500 | $1,290,475 | $25,809,500 | $0 | $0 | $6,558,375 | $73,792,500 | $1,290,475 | $25,809,500 | $1,202,163 | $24,043,260 |
| Total | 4,058,475 | 81,169,500 | 4,058,475 | 81,169,500 | $0 | $0 | $9,326,375 | $129,152,500 | $4,058,475 | $81,169,500 | $3,931,341 | $78,626,820 |
| Pajaro Basin | ||||||||||||
| Sediment Removal | $266,000 | 5,320,000 | $266,000 | 5,320,000 | 0 | 0 | $266,000 | 5,320,000 | 266,000 | 5,320,000 | $253,993 | 5,079,860 |
| Vegetation Management | $642,480 | 12,849,600 | $2,924,080 | 58,481,600 | $0 | 0 | $3,079,670 | 61,593,400 | $2,699,270 | 53,985,400 | $469,480 | 9,389,600 |
| Total | $908,480 | $18,169,600 | $3,190,080 | $63,801,600 | $0 | $0 | $3,345,670 | $66,913,400 | $2,965,270 | $59,305,400 | $723,473 | $14,469,460 |
| Bank Protection and Repair | $3,780,000 | $75,600,000 | $3,780,000 | $75,600,000 | $0 | $0 | $3,780,000 | $75,600,000 | $3,780,000 | $75,600,000 | $1,890,000 | $37,800,000 |
| Levee Maintenance | $1,590,000 | $31,800,000 | $1,590,000 | $31,800,000 | $0 | $0 | $1,590,000 | $31,800,000 | $1,590,000 | $31,800,000 | $1,590,000 | $31,800,000 |
| Debris and Obstruction Removal | $3,170,000 | $63,400,000 | $3,170,000 | $63,400,000 | $0 | $0 | $3,170,000 | $63,400,000 | $3,170,000 | $63,400,000 | $3,170,000 | $63,400,000 |
| Canals | $109,565 | $2,191,300 | $109,565 | $2,191,300 | $0 | 0 | $109,565 | $2,191,300 | $109,565 | $2,191,300 | $109,565 | $2,191,300 |
| Mitigation | $1,910,000 | $38,200,000 | $1,910,000 | $38,200,000 | $1,910,000 | $38,200,000 | $1,910,000 | $38,200,000 | $1,720,000 | $34,400,000 | ||
| ALTERNATIVE TOTAL | $11,746,520 | $234,930,400 | $14,028,120 | $280,562,400 | $0 | $0 | $19,451,610 | $331,657,200 | $13,803,310 | $276,066,200 | $11,244,379 | $224,887,580 |
C. CONSIDERATIONS OF GEOMORPHOLOGY, ENGINEERING REDESIGN, AND WATERSHED APPROACH
1. Role of Fluvial Geomorphology
Section IV.A. Environmental Analysis, Geomorphology, in this EIR explains the basic fluvial processes that define the physical environmental setting of the creeks and give rise to the changes that reduce flood capacity and bank stability. Routine maintenance is directed at these adverse changes to protect property and public safety.
Fluvial geomorphology addresses the role sediment transport plays in defining channel geometry. Sediment deposition, obviously, directly affects the sediment removal component of routine maintenance. Sediment also forms the substrate for vegetation growth in-channel, and thus affects vegetation management and flood capacity. Erosion is a source of sediment and thus affects the need for bank protection. The general discussion of alternatives to maintenance is relevant to all three primary maintenance activities.
As long as those fluvial processes adversely impact the capacity of the channels, the need for maintenance will persist. The only way to reduce that need would be to alter the channels themselves or to change the sediment regime that defines them.
These types of changes are outside of the scope of the SMP because they generally would require time consuming development of Capital Improvement Projects, substantial funding from unidentified sources, acquisition of substantial additional right-of-way in urban areas, or control over land use in watersheds which is beyond the authority of the District. Some maintenance sites, particularly tidal sediment removal sites, have no prospect of change to eliminate sediment deposition and would always require maintenance to keep flood capacity at design levels. Some changes could be made in the course of Capital Improvement Projects, but that would still leave the rest of the stream system needing routine maintenance.
2. Design Alternatives
Design Alternatives would entail modification of the stream channel and surrounding floodplain. The modification may involve structural changes to provide excess capacity which can tolerate degradation from sediment accumulation or structural changes to create stable channel geometry that provides equivalent floodwater capacity but is no longer subject to sediment deposition or erosion.
New construction to increase capacity would include rebuilding road crossings (hydraulic structures), raising levees and reconfiguring the channel cross section to accommodate greater flow and greater sediment and vegetation. The environmental impact of such changes would depend on site conditions, but in nearly every instance, would completely disturb existing channel and streamside vegetation. The reduced cycle of future disturbance may produce an environmental benefit if post-construction conditions allowed a greater area of undisturbed wetlands to form.
Theoretically, one solution to sediment removal problems would be to create a geomorphically stable channel that could pass the sediment load from upstream, provide an acceptable level of flood protection, and have ecologically valuable features common to streams (riparian vegetation and diversity in topographic and hydrologic conditions). Although such an opportunity may exist in some sediment removal sites, the majority suffer from the fact that the original continuity of sediment transport has been significantly disrupted, and that the stream corridor is too narrow. Natural sediment depositional areas such as deltas, alluvial fans and tidal channels now occur in narrow flood protection channels. Even without maintenance, episodic flood flows destroy this vegetation.
Many of the District's sediment removal sites occur in
narrow, confined stream channels with little room to
accommodate sediment deposits or a stable channel and
meander belt width. Typical maintenance problems are
discussed in Section IV.A. Geomorphology, and classified in
Table IV-A-2.
Many channels have been designed to maximize hydraulic capacity while minimizing stream width and hydraulic roughness caused by obstructing riparian vegetation. Because stream corridor width is restricted in most cases by urban development, it is usually impossible to create a stable channel within the existing right-of-way without a potentially significant loss of flood protection.
Engineered and geomorphic solutions cannot be implemented at the present time. Redesigned channels could reduce maintenance and result in lower long-term economic and environmental cost. The magnitude of this benefit would need to be measured against the economic and environmental cost of the structural changes. Significant changes to facilities require individual CEQA documents. At present, the proposed project with a regional mitigation program is a demonstrably achievable alternative and structural solutions are indeterminate and speculative. Tidal action, low channel slope, and urban floodplain encroachment mean that there are no simple changes that can be implemented as easily as ongoing maintenance.
3. Watershed Approach
Reduced sediment input into the channel would reduce the sediment removal and vegetation management maintenance work needed downstream and hence reduce the environmental impact.
In-channel sediment reduction would result from identification of and abatement of potential erosion sites, including bank areas with unstable soils, overly steep slopes or insufficient vegetative cover.
Other upstream sources of accelerated erosion and excessive sediment supply include quarries (active, inactive), graded and unvegetated areas, naturally erodible deposits subject to mass wasting, forest and brush fire sites, and steep areas such as roadcuts subject to gully erosion. A systematic study would be necessary to determine whether the sources are significant, and if they are controllable.
Many man-made sediment source areas would be largely in upland areas not directly under District jurisdiction, but the District works cooperatively with the local land use authorities to abate the influx of sediment.
Watershed management is not a complete alternative to maintenance. Sediment input and land use induced channel instability could be reduced, but the effect would more realistically come from changes in future land use rather than in retroactive modification of past land uses. While the District may seek to reduce long-term cost through further coordination with surrounding jurisdictions, that approach does not materially diminish the projected need for maintenance work described in this Program EIR.
The cumulative effect of the watershed scale approach defined above would be to gradually reduce maintenance needs. The current land use encroachment and impacts on basin hydrology are not significantly reversible. The principal benefit for watershed level cooperative work with land use jurisdictions would be realized as a reduction in future maintenance impacts.
RETURN TO TOP OF PAGE RETURN TO TABLE OF CONTENTS