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LAND USE AND COMMUNITY VALUES
This section discusses environmental issues that define a livable community: land use planning, aesthetics, air quality, noise, public services and recreation. The District's Stream Maintenance Program will not directly cause any substantial change in land use or be incompatible with surrounding land uses throughout Santa Clara County because maintenance will be confined to District property or easement. Land uses on adjacent parcels may be indirectly affected by changes in visual condition, dust, odor, noise, or changes in access created by maintenance work. These potential impacts on community values are reduced to less than significant by either the short-term period over which these conditions occur at any one location, or by application of best management practices
Much of the routine maintenance will take place in built-up areas within cities, as opposed to rural county areas. The potential significance of land use and community value impacts is related to the type of land uses adjacent to creeks and canals as well as the frequency and duration of the impact. In general, since the District's maintenance work is either directly requested by the landowners or occupants adjacent to the creeks, or is done for their benefit, the landowners would not be overly sensitive to such effects if they occur. The adjoining land use sensitivity is also reduced because the duration of the work is relatively short (a few days or weeks), and infrequent (once a year or less often).
1. Land Use and Planning
a. Setting
1) Geography of Santa Clara County Streams
During the early 1900's, farmers straightened and sometimes relocated many creeks in Santa Clara County. These stream changes were intended to facilitate agriculture and were not designed to carry major flood flows. Since 1929, the predecessors to the present-day Santa Clara Valley Water District further modified creeks by excavating channels, building levees and providing drop structures at large grade breaks. As the years went by, a higher level of flood protection was needed, and many creeks were channelized to a trapezoidal configuration and lined with concrete.
The pattern of development and urbanization in the Santa Clara Valley over the past 50 years is characteristic of post-World War II development throughout suburban California. Houses, apartments, commercial and industrial facilities, roads, freeways and parking lots have been created in areas once covered with orchards and fields. Infrastructure such as sewers and storm drains have been buried underground, with outfalls to streams or to the bay. Most importantly, streams that were at the top of the alluvial fan were impounded by reservoirs, then further narrowed and channelized which allowed development on the historic floodplains.
Today, the land uses adjacent to the watercourses include a full range of uses (e.g. residential, commercial, industrial, public, open space) under the land use jurisdiction of either Santa Clara County or one of its 15 incorporated cities. Each jurisdiction currently has as its goals the preservation of open space and the riparian corridors, but historically, most prior development has not considered the natural character of streams as an amenity. Houses are located adjacent to a narrowed riparian corridor, with back-yard fences at the tops of banks.
2) Maintenance Program and Local Land Use Jurisdictions
The District is a special district with its own charter, and manages its mostly linear properties within the jurisdiction of the cities and County for the primary purposes of flood protection and water supply. The District does not have any authority to control land uses under the jurisdiction of the cities and County. However, land uses on adjacent properties, no matter the jurisdiction, can affect each other, therefore, a general description of the types of land uses adjacent to creeks and canals is provided below. For more information regarding jurisdictional issues, please see Chapter III, Plans, Ordinances and Policies.
The greatest extent of creek lengths in SCVWD jurisdiction are in the County, the City of Gilroy sphere of influence, and the City of San Jose and its sphere of influence.
Most of the proposed sediment removal, vegetation management, and bank protection work is expected to take place within incorporated cities. For certain creeks (e.g. Canoas, Madrone Channel , Sunnyvale East Channel), all of the creek within each respective jurisdiction will be impacted by sediment removal under the proposed program.
3) Land Uses Adjacent to Creeks
In the SCVWD jurisdiction, 25% of the creeks run through residential areas (low to high density), 50% through natural open space or agriculture, 5% through recreational and park land, and the remaining 20% is variously commercial, institutional or industrial (TRA, 1997). Creeks with large extent of residential land use (more than 3 miles) adjacent to channels include Adobe, Matadero, Permanente, San Francisquito and Stevens, San Tomas Aquino, Saratoga, Wildcat Creeks and Sunnyvale East Channel, Canoas, Los Gatos, Ross Creeks and the Guadalupe River, and Lower Silver Creek. Creeks through residential areas have a greater potential for land use issues because of the higher numbers of affected citizens.
The greatest extent and proportion of natural open space and agricultural lands adjacent to creeks is in the Pajaro River Basin (101 miles), compared with 71 miles in the Santa Clara Basin. Open space, agricultural and park uses tend to have fewer land use issues because there are relatively fewer users and less potential for property damage due to flooding.
b. Significance Criteria
A project would be normally considered to have a significant effect on land uses if one or more of the following factors were met:
Criterion LU-1 Conflict with any applicable land use plan, policy or regulation of the jurisdiction in which the project is located adopted for the purpose of avoiding or mitigating an environmental effect.
Criterion LU-2 Physically divide an established community; for example, installation of an above-ground pipeline through an established neighborhood that would cause a permanent disruption in the physical arrangement of that neighborhood.
c. Impacts
1) Overview
The land use discussion below is in accordance with the significance criteria outlined above. If the maintenance projects conform to the BMPs included in the proposed program, there will be no significant land use impacts. These BMPs are described in the Project Description section of this EIR and the relevant BMPs are summarized at the end of each of the following subsections.
Many land use impacts are annoyance impacts such as increase in noise, dust production, and odor or decrease in aesthetic qualities, as well as interference with access. All of these effects are described in their respective sections in this chapter. The potential significance of impacts is related to the type of land uses adjacent to creeks as well as the frequency and duration of the impact. In general, since the District's maintenance work is either directly requested by the landowners or occupants adjacent to the creeks, or is done for their benefit, the landowners are by and large not sensitive to such effects, if they occur.
The adjoining land use sensitivity is also reduced because the duration of the work is relatively short (a few days or weeks), and infrequent (every other year or less). Historic records from 1977 to 1999 indicate that the average duration of sediment removal work is 10 working days, with an average of 3,200 cy of material removed. The duration of sediment removal work is very project specific, however, and duration has ranged from ½ day (6 cy) to 84 days (7,040 cy along San Tomas Creek in 1992). Historic records for erosion repair work indicate that the average duration of a bank stabilization project is 10 working days. Duration has ranged from 1 day (repairing 1,900 lineal feet of gabion baskets) to 104 days (installing 520 feet of sacked concrete along Saratoga Creek in 1990)(Mary Stone, personal communication, 2/15/01). By comparison, the duration of most vegetation management activities in an area is usually a few hours. However, for hand removal of vegetation from a channel, the work can take place in the same neighborhood from ½ day to 5 working days. During that time period, the work will progressively move along the stream and won't be located behind any single home for longer than a few hours (Mark Wander, personal communication, 2/01/01).
2) Sediment Removal, Vegetation Management and Bank Protection Activities
The District's Maintenance program will not directly conflict with any applicable land use or be incompatible with surrounding land uses. The requirement for the District's work is related to the prior land use change which has contributed to the need to modify and provide flood protection of the creeks. The program is a result of prior land use change; the program does not cause land use change. As there are no proposed land use changes, there is no impact.
The District's Maintenance program will not alter or be in nonconformance with any regional, federal, state land use or environmental plans or policies (see Chapter III, Plans, Ordinances and Policies). The land uses within the District will not change as a result of the proposed program. There is no impact.
The District's Maintenance program will not conflict with the County's flood protection management policies of the 15 cities and County government. This is also further discussed in Chapter III. One of the main objectives of the Stream Maintenance activities is to increase flood protection by restoring flood capacity (where possible, to the 1% level for sediment removal and 2% for bank protection). The effects of maintenance on the risk of substantial flooding may result in a beneficial impact.
The District's maintenance program will not disrupt the physical arrangement of any community. No above-ground pipelines will be installed as part of the proposed project.
2. Aesthetics
a. Existing Conditions
The streamside areas within the District vary widely and hence the sensitivity to aesthetic or visual impact varies widely. Open space along the District's creeks is found mostly in the agricultural and semi-rural areas in the south county. Riparian remnants occur in the north county areas in the less urbanized and foothill areas. In the heavily urbanized areas, development along streams have been often designed without visual contact or physical interaction with the channel, except at road crossings, where the creek is enclosed in box culverts. Many of the streams are closed off by chain link fences at the bridge crossings.
The chapter on Geomorphology (IV. A.) defined five types of channels that characterize the work area of most of the District's maintenance effort. These physical classifications tend to share a similar visual setting and are a convenient way to organize a discussion of the project's potential aesthetic effects. A discussion of five types of channels in the District and the existing viewsheds in these types follows.
Most of the urban area of the Santa Clara Valley is built on alluvial fans, foothill valleys and alluvial flood plains. Thus, many of the channels in the Type 1 streams (Alluvial Fans, Foothill Valleys and Alluvial Flood Plains) are encroached by residential, commercial and industrial uses right up to the tops of channel banks. These channels vary in vegetation types and quantities, from bare ground and sack concrete to heavily wooded willow thickets. Because of the flood plain and bank encroachment, middle and long-distance view corridors are not usually present. In agricultural areas of the South County, vegetation, especially willow thickets, are the main indicator of a stream in the area. The extent of vegetation in these channels depends upon the area of flood plain. Recreational trails along many of the streams are currently being implemented (San Tomas Aquino Creek, Guadalupe River, Coyote Creek), with more trails in planning stages.
Types 2 and 3 streams (Deltas and Tidal Channels) are wider, straighter and flatter, offering more middle and long-distance views. However, views of the channel from other areas and views from inside the channel may be constrained by tall levees . These channels also vary widely in vegetation types and quantities, but most Types 2 and 3 streams contain bands of wetland vegetation (tules, willows) along the edges of the channel.
Types 4 and 5 streams (Channelized Streams and Streams Influenced by Hydraulic Structures) can be wide compared to unmodified channels. These channelized streams are flood protection channels designed to maximize flow area and minimize hydraulic roughness. Slopes are usually unvegetated concrete or rock. Hydraulic structures such as bridges, culvert crossings, bank protection structures, concrete channel sections and other structures are present in channelized streams and are highly visible.
b. Significance Criteria
A project would normally be considered to have a significant effect on aesthetics if one or more of the following factors were met (CEQA Guidelines:
Criterion Aes-1 Permanently and substantially alter or degrade the visual character or quality of the site and/or surrounding area due to:
-- Major natural landform alteration, e.g. one or more distinct and prominent geologic or topographic features would be destroyed, permanently covered or substantially modified. Such features may include, but are not limited to, hilltops, ridges, canyons, ravines, and rock outcrops.
-- Removal of major stands of vegetation and/or trees which are a visually prominent feature of the landscape as seen from public areas.
-- Removal of visually prominent rock outcroppings, or
-- Introduction of structures that are not of the same style or scale as surrounding development.
-- Result in permanent structural development located within ½ mile of a designated scenic highway that would be highly visible in a way that detracts from the existing scenic quality and character of the corridor.
Criterion Aes-2 Permanently and substantially obstruct or block any scenic vista or view corridor that is designated on local plans as a significant or important view corridor or scenic area.
Criterion Aes-3 Produce a new source of substantial light and glare, which would adversely affect day or nighttime views in the area or pose a nuisance. This includes ambient nighttime illumination levels that would be increased beyond the property line or use of highly reflective building materials.
c. Impacts
1) Overview
The potential for aesthetic impact is limited because, in most cases, channelized creeks in urban residential and commercial areas of the District are screened from view except from immediately adjacent land parcels. The channel bottoms where maintenance is done are below grade and not always visible from adjacent land uses.
Residents adjacent to creeks or creek-side trail users could be temporarily affected by stream maintenance activities. If maintenance projects conform to the BMPs included in the proposed program, there will be no significant temporary or permanent aesthetic impacts to sensitive receptors. These BMPs are described in the Project Description section of this EIR and are also listed at the end of each of the following subsections of Sediment Removal, Vegetation Management and Bank Protection.
Maintenance has a beneficial effect on aesthetics when work crews remove trash and debris in and along creeks.
No local, state or federally-designated historic buildings will be affected by the SMP. Nor will it have any adverse effects on any areas within a designated state scenic highway corridor would be altered. No scenic vistas or view corridors that are designated on local plans would be permanently or substantially altered.
Stream Maintenance activities normally occur only during daylight hours, from 7:00 a.m. to 5:00 p.m. Night lighting is rarely used and thus maintenance activities would not produce a new source of substantial light and glare.
2) Sediment Removal
Removal of sediment may also remove vegetation from the channel. Depending on the aspect from the surrounding land uses, this may result in a scenic vista being temporarily changed from that of a vegetated creek to a partially vegetated or bare creek until the vegetation regrows. Large trees are not removed by these types of routine stream maintenance activities and the bottom of the channel is not always visible from adjacent land uses.
Sediment removal sites would not be altered permanently by sediment removal activities as many of these activities are cyclical (sediment is removed during the dry season, then more sediment is deposited at the same reach during the following rainy season). While large equipment in creek channels, creek banks and along levees would be visible to sensitive receptors, sediment removal activities are temporary. There will be no significant temporary or permanent aesthetic impacts to sensitive receptors from sediment removal projects. However, there still may be negative environmental effects resulting from sediment removal activities that are below the stated thresholds of significance. Implementation of the following BMPs will reduce these negative environmental effects:
| 1.4 | Avoid Erosion When Restoring Flows |
| 1.6 | Use of Wheel and Track Mounted Vehicles in Stream Bottoms |
| 2.1 | Minimize Vegetation Removal |
| 2.2 | Minimize Stream Access Impacts |
| 3.6 | Remove Sediment from One Side of Large Channels in Alternate Years |
| 4.3 | Stabilized Construction Entrance |
| 4.6 | Work Site Solid Waste Management |
3) Vegetation Management
Vegetation management could permanently alter and degrade the visual character of creeks if it were to remove major stands of large vegetation, such as willow thickets along the Pajaro River. However, large stands of trees would not be removed by routine vegetation management activities, as the District's policy is to not remove material in creeks larger than 6" diameter at breast height (dbh) by mechanical means, or larger than 2" dbh by herbicides. This effect is considered Less than Significant, as there will be no permanent change in these willow-covered creek channels from vegetation removal activities.
Depending upon the aspect from the surrounding land uses, vegetation management activities may cause a scenic vista to be temporarily changed from that of a vegetated creek to a partially vegetated, or bare creek until vegetation regrows.
Vegetation removal on levees and maintenance roads will be limited to that necessary for facility inspection purposes, to meet regulatory requirements, to comply with fire codes, provide visual clearance to inspect the condition of a facility, and to meet capacity requirements. If maintenance work leaves slopes in a bare soil condition, the District will plant slopes with native vegetation or use other soil stabilization techniques consistent with the facility's design and the probable success of revegetation. There will be no significant temporary or permanent aesthetic impacts to sensitive receptors from vegetation management projects. However, there still may be negative environmental effects resulting from sediment removal activities that are below the stated thresholds of significance. Implementation of the following BMPs will reduce these negative environmental effects:
| 2.2 | Minimize Stream Access Impacts |
| 2.5 | Planting |
| 2.6 | Mulching |
| 2.9 | Revegetation Site Maintenance |
| 6.1 | Spill Prevention |
4) Bank Protection
Bank protection may either replace an eroded earthen bank with soft structures (vegetated slopes, willow wattles), hard structures (i.e., rock, concrete, sack concrete), or a mix of soft and hard structures. The District estimates that approximately 1 mile of bank protection work would be done annually. Thus, bank protection work could occur on 20 miles of the approximately 1650 miles of bank under District jurisdiction over the life of the program. Bank protection rarely results in the removal of large trees, because the eroded bank is usually unvegetated by the time an erosion problem has developed.
Bank protection activities could have significant and cumulative visual impacts to sensitive receptors such as trail users, homeowners and adjacent land users (in areas of high visibility) if BMPs were not implemented. Implementation of the following BMPs will reduce potential impacts to a less than significant levels:
| 1.11 | Concrete use near waterways |
| 2.2 | Minimize Stream Access Impacts |
| 2.3 | Minimize Hardscape in Bank Protection Design |
| 2.5 | Planting |
| 2.6 | Mulching |
| 2.9 | Revegetation Site Maintenance |
| 3.14 | Maintain or Provide Escape Cover |
3.Air Quality
a. Setting
The Stream Maintenance program is located in Santa Clara County which lies along the southern portion of the San Francisco Bay. The climate of the San Francisco Bay region is classified as Mediterranean, with little or no precipitation during the summer months and moderate precipitation during the winter months. This climate is controlled primarily by the Pacific High which migrates northward during the summer months holding storm tracks well to the north. During the winter months, the Pacific High migrates southward permitting storm centers to swing into and across California. Rainfall is variable across the project area, generally higher on the west and at higher elevations. The seasonal climate dictates that maintenance work is usually done in the drier summer and fall period.
All of Santa Clara County is in the Bay Area Air Quality Management District (BAAQMD). The Bay Area is in attainment for all national ambient air pollutant standards, but is in non-attainment for state standards for two pollutants, ozone (one-hour standard) and fine particulate matter (PM10, both annual mean and 24 hour standards). Fine particulate matter represents the respirable fraction of particulate matter and is termed PM10 for particles smaller than 10 microns in diameter (regulated by the state) or PM2.5 for particles smaller than 10 microns in diameter (regulated by the state). Mobile sources - vehicles - are major sources of these pollutants, with wood fires and unpaved roads contributing also to PM10. Generally, combustion tends to produce the finer particles and mineral earth sources of dust, such as earthmoving, tend to produce coarser particles.
b. Significance Criteria
A project would be normally considered to have a significant effect on air quality if one or more of the following factors were met (CEQA Guidelines):
Criterion AQ-1 Violate any air quality standard or contribute to an existing or project air quality violation.
Criterion AQ-2 Major alteration of air movement, moisture or temperature, or any change in climate, either locally or regionally.
Criterion AQ-3 For a stationary use or permanent project operations, result in a generation of emissions of or in excess of 80 pounds per day for ROG, NOx, or PM10 or 550 pounds per day of carbon monoxide.
Criterion AQ-4 Result in temporary generation of dust (PM10) due to sediment removal in stream or drainage channels equivalent to grading an area of 2.2 acres per day.
Criterion AQ-5 Expose sensitive receptors (i.e., residents, schools, hospitals) to substantial pollutant concentrations, i.e. those that exceed the BAAQMD standards identified above.
Criterion AQ-6 Emit toxic or hazardous air pollutants resulting in a significant increased human health risk, in which the probability of contracting cancer for the Maximally Exposed Individual (MEI) exceeds 10 in one million or ground-level concentrations of non-carcinogenic toxic air contaminants would result in a Hazard Index greater than 1 for the MEI.
Criterion AQ-7 Create frequent objectionable odors affecting a substantial number of people (500 or more) or create other nuisance problems.
Criterion AQ-8 Conflict with or obstruct implementation of Bay Area Air Quality Management Plan.
For construction activities, BAAQMD significance criteria emphasize implementation of effective and comprehensive dust control measures. The BAAQMD considers any construction project that complies with the appropriate dust control measures to be less than significant.
c. Impacts
1) Overview
These maintenance activities are essentially construction activities and have a similar potential for air pollutant emissions: diesel exhaust emissions from equipment at the work site (including mowing), spray rigs and on-highway trucks, and fugitive particulate (dust) from disturbed earth at the work site and from hauling sediment and green waste to upland locations. If the maintenance projects conform to the BMPs listed as part of the proposed program (including BAAQMD dust control measures), there will be no significant PM10 impacts to sensitive receptors.
2) Criteria Pollutants
Air quality can be affected by both fugitive and exhaust emissions. Fugitive PM10 emissions are the most potentially significant. Emissions from maintenance vehicles would be short term and spread out over the length of channel. Because these activities are temporary construction projects, the potential for localized high concentrations of air pollutants is low.
Residences, recreational trails, commercial/office uses and agricultural uses are all considered sensitive receptors and are often located near creeks. PM10 emissions would not be significant, because these activities would be temporary. Sensitive receptors would occasionally be exposed to large particulate (visible dust) from construction. Dust exposure potential for any one receptor would decrease as activity moved downstream and would end once the short term project is completed.
If the maintenance projects conform to the BMPs included in the proposed program, there will be no significant permanent air quality impacts. These BMPs are described in the Project Description section of this EIR and are also listed at the end of each of the following subsections of Sediment Removal, Vegetation Management and Bank Protection.
3) Sediment Removal
Annual sediment removal work entails handling large volumes of earth and off-site disposal. The annual average of roughly 80,000 cubic yards of sediment on about 16 miles of channel may vary from year to year, depending in part on rainfall conditions of the past season. Trucks traveling over dirt roads, gradealls, trucks hauling sediment, and other maintenance activities will lift particulate matter and suspend it in the atmosphere. The potential for fugitive dust is reduced because most creek work areas are naturally damp and because most of the drier, non-tidal sites have a coarse particle size with a low silt content. Local emissions are caused largely by travel on unpaved roads and earth spilled onto paved roads.
The average sediment removal construction period is 10 working days, though this activity can last as long as 3 months. Sediment removal sites typically have an area of less than 4 acres, and only about 10% of this area is worked on in any one day: work teams proceed from one end of the site to the other at a rate of 200 to 400 feet per day. Teams move from site to site through the course of the summer to carry out maintenance activities where they are needed. While individual work sites may be of short duration and small area, cumulatively, the District's work will affect several tens of acres spread over a roughly six-month activity period. In order to minimize the cumulative effects of maintenance on dust and PM10 generation, standard BAAQMD controls are adopted as BMPs.
If the maintenance projects conform to the BMPs listed as part of the proposed program (including BAAQMD dust control measures), there will be no significant PM10 impacts to sensitive receptors.
| 4.3 | Stabilized Construction Entrance |
| 5.1 | BAAQMD Basic Dust Control Measures |
| 5.2 | BAAQMD Enhanced Dust Control Measures |
4) Vegetation Management
Vegetation management activities typically involve using vehicles to travel to the job sites and using mowers and spray rigs once at the job sites. As listed above , these activities from maintenance vehicles would be short term and spread out over the length of channel. Because these activities are temporary construction projects, the potential for localized high concentrations of air pollutants from engine exhaust is low.
Vegetation management projects can cause PM10 effects as dust is raised from mowing and traveling along dirt roads during the dry season. The implementation of the BAAQMD dust control measures will reduce air quality effects from vegetation management activities to less than significant levels.
Herbicide application uses water as a carrier and the potential for volatile organic gas emissions is minimal. The herbicides used for vegetation management are not hazardous air contaminants when used in accordance with state law. The broader issue of pesticides and public and environmental health is addressed in Chapter IV. F., Public Health and Safety. If the maintenance projects conform to the BMPs listed as part of the proposed program (including BAAQMD dust control measures), there will be no significant PM10 impacts to sensitive receptors.
| 4.3 | Stabilized Construction Entrance |
| 5.1 | BAAQMD Basic Dust Control Measures |
| 5.2 | BAAQMD Enhanced Dust Control Measures |
Bank Protection
Bank protection work typically averages 8 days. In addition to the vehicles used to travel to the job sites, equipment used for bank protection may include excavators, dozers, cranes, loaders and 10-and 20- cubic-yard dump trucks, concrete trucks, and pumps and water trucks. Water pumps and piping, and cofferdams of earth, gravel, sandbag, hay bales or rubber or other suitable material may be brought by large vehicles to the work sites. As stated above, emissions from maintenance vehicles and fugitive dust from operation of these vehicles would be short term and spread out over the length of channel. The following BMPs will reduce or avoid all impacts from fugitive dust and air emissions.
| 4.3 | Stabilized Construction Entrance |
| 5.2 | BAAQMD Enhanced Dust Control Measures |
Cumulative Emissions
Cumulative emissions for all Stream Maintenance activities for the District are shown in Table IV-C-1. Note that these emissions would be generated at several locations distributed over the entire District and that they would occur for short periods at each location. Emissions for a typical site that also includes dust control measures are presented in Table IV-C-2.
Table IV-C-1
District-wide Maintenance Emissions (Pounds)
| Average Day 1 | Maximum Day2 | Annual Total | ||||
| Pollutant3 | Equipment Emissions | Fugitive Emissions | Equipment Emissions | Fugitive Emissions | Equipment Emissions | Fugitive Emissions |
| PM10 | 11 | 34 | 21 | 69 | 740 | 241 |
| CO | 676 | -- | 1,350 | -- | 47,300 | -- |
| ROG | 45 | -- | 90 | -- | 3,150 | -- |
| NOx | 208 | -- | 415 | -- | 14,500 | -- |
| SOx | 23 | -- | 45 | -- | 1,570 | -- |
Source: Thomas Reid Associates and the BAAQMD CEQA Guidelines, Assessing the Air Quality Impacts of Projects and Plans, April 1996.
All calculations based on 42,000 gallons of diesel fuel used per year, a 70 day work year, an average site size of 3.37 acres, and 10% of each site is worked on in the maximum day.
1 Assumes 2 teams working simultaneously in 2 different parts of the District.
2 Assumes 4 teams working simultaneously in 4 different parts of the District.
3 PM10 -- Fine particulate matter, less than ten microns in diameter, respirable.
CO -- Carbon monoxide
N0x -- Nitrogen oxides
ROG -- Reactive organic gases
S0x -- Sulfur oxides
Table IV-C-2
Emissions for a Typical Site with Basic Dust Control Measures
(Pounds/Day)
| Pollutant1 | Equipment Emissions | Fugitive Emissions | Total |
| PM10 | 5.3 | 8.6 | 13.9 |
| CO | 338.5 | -- | 338.5 |
| ROG | 22.5 | -- | 22.5 |
| NOx | 103.8 | -- | 103.8 |
| SOx | 11.3 | - | 11.3 |
5) Odor
Sediment Removal
The sediments removed from channels have some potential to release odor or to build up odorous gases when stockpiled. The problem has been encountered in the past and is particularly associated with sediments in tidal areas that have high organic material and saltwater content. Under anaerobic conditions, microorganism metabolism of organic material often produces malodorous, volatile organic compounds. Seawater contains sulfate ions, which microorganisms can use in the metabolic process, producing reduced sulfur compounds, hence the rotten-egg smell of some tidal mudflats.
These conditions are unavoidable in tidal areas. The potential for odor comes from the initial removal process, and from sediment stockpiling to dewater or schedule removal. In the stockpiles, fine-grained sediment will impede air movement and lead to anaerobic conditions. When there are large volumes of organic material present, as from stockpiles with heavy wetland vegetation, the stockpile will release odors. In general, when the pile is disturbed again for removal, odor will be released at the site and from the trucks carrying the material off-site.
The extent of odor is difficult to predict. Low wind speed and/or winds directing odor at residential areas would obviously exacerbate the problem. Favorable conditions for initial sediment work and subsequent removal would be sunny and windy days (because unstable atmospheric conditions favor rapid dispersal). These conditions are common in summer and early fall. This corresponds to the July 1 through October 15 period of Stream Maintenance. Stockpiles left beyond the end of the normal maintenance period into winter when unfavorable meteorological conditions are more likely to have a greater potential for causing odor problems. If the maintenance projects conform to the BMPs listed below there will be no significant odor impacts to sensitive receptors.
| 5.3 | Avoid Stockpiling Potentially Odorous Sediments |
Vegetation Management
Dead vegetation has minimal potential for odor when left in place because the mass of material is small and there is adequate air for gradual aerobic decomposition. Where vegetation is removed and piled along a channel, there may be odors unless the piles are adequately aerated. This problem is similar to any debris management for landscaping or agriculture. Green waste is typically disposed of at green waste landfills or on District property where the waste is composted. Herbicide residue does not affect disposal. Therefore, there is no impact.
Bank Protection
Bank protection has little potential for odor, because it does not require the removal or stockpiling of large amounts of sediment or vegetation subject to potential odorous conditions. Therefore, there is no impact.
4. Noise
a. Terminology
Noise is unwanted sound. Noise is measured on the logarithmic decibel scale (dB), usually with a frequency sensitivity that matches the human ear, called "A-weighting." Thus, most environmental measurements are reported in dBA, decibels on the A-scale. Because decibels are logarithmic units, the noise level in dBA from two noise sources are not arithmetically additive. For example, doubling of the noise energy by the addition of two equal noise sources results in an increase of 3 dB (e.g. 56 dBA + 56 dBA = 59 dBA).
The equivalent noise level, Leq, represents the level of a steady noise having the same sound energy as the time-varying noise measured. Leq(x) represents the time-weighted average for x minutes, while Leq(h) is used to describe the time-weighted average for one hour. Leq will be used to describe the noise levels produced by District activities.
According to State general plan law, cities and counties must describe the noise characteristics of areas within their jurisdictions using measures that account for both the daytime and nighttime noise levels. Twenty-four hour noise environment exposure over a day is often described by CNEL (Community Noise Environment Level) or DNL (day/night level), measurements that assign penalties to noise levels that occur in the quieter evening and nighttime hours, to account for the increased annoyance and intrusive quality of nighttime noise. CNEL will be used to describe the overall noise environment of areas within the scope of the proposed program.
Noise spreads out uniformly in waves from a source and attenuates (decreases in force and magnitude as it spreads) at a rate of 6 dB decrease in noise level for distance doubled. Sensitive receptors are persons and facilities that could be adversely affected by noise. To predict the noise impacts of the program on sensitive receptors, noise levels must be determined away from the site at the location of sensitive receptors. Treating the project equipment as a "point" or stationary noise source, the noise levels can be predicted at any distance because sound pressure varies inversely away from a source. By theory, noise attenuation from a point source is 6 dB for each doubling of the distance from the source. In practice, "soft" non-reflective ground and intervening vegetation between the noise source and the receptor produce a drop-off of 9 dB for each doubling of distance and air absorption over distances greater than 1,000 feet increases noise attenuation.
b. Noise Policies
Each of the cities and Santa Clara County have policies and guidelines for their jurisdictions that attempt to minimize the effects of noise on people through construction standards, zoning restrictions, hours of operation and suppression techniques. Goals for noise levels are defined that are compatible with the various land use types within each jurisdiction. However, all jurisdictions recognize that higher than standard noise levels will be generated from time to time by heavy equipment engaged in construction or maintenance activities throughout the jurisdiction. Because heavy-equipment noise is an unavoidable necessity to modern life, jurisdictions typically include wording in noise ordinances and elements exempting these short-term, temporary, higher noise levels from compliance with the overall standards for the various land uses.
c. Setting
Within the district boundaries, background noise levels vary greatly from the very low noise levels in the semi-rural western and eastern foothills to the high noise levels of the urbanized central Santa Clara Valley floor. The highest noise levels in the project area would probably be encountered in the vicinity of the San Jose International Airport. The noise environment of the north central portion of the Santa Clara Valley is heavily influenced by takeoffs and landings and, in accordance with State law, the airport monitors noise levels throughout the Valley to identify the area most impacted. Noise monitoring has defined an elliptical contour around the San Jose Airport within which noise levels from aircraft alone exceed 65 dBA CNEL. More localized noise sources such as traffic on nearby freeways and surface streets would further elevate CNEL within this area.
Noise generated by heavy equipment engaged in Stream Maintenance activities could impact sensitive land uses adjacent to the proposed sites for future work. Land uses sensitive to noise generation are primarily those with an outdoor use component that includes an expectation of quiet noise levels. Low noise levels can normally be accomplished for interior spaces through modern construction techniques. Interior noise levels inside residences adjacent to creeks would typically be less than 45 dBA CNEL with the windows closed because of the noise attenuation provided by walls and windows. Examples of sensitive land uses include backyards and gardens in residential areas, parks and open space reserves, outdoor shopping areas, schoolyards and cemeteries. In these areas, excessive noise levels would be a nuisance to outdoor users. Typically, outdoor areas cannot be easily shielded from high noise levels without the construction of intervening barriers.
d. Significance Criteria
A project would be normally considered to have a significant effect on sensitive receptors if one or more of the following noise factors were met:
Criterion N-1 Expose persons to or generate permanent noise levels in excess of standards established in the local general plan, noise ordinance or applicable standards.
Criterion N-2 Result in a substantial permanent increase/change in the ambient noise level (i.e. a 5 dBA increase in an area where the existing noise level is considered acceptable or a 3 dBA increase in areas where existing noise levels are not considered acceptable, as defined by state or local noise/land use compatibility standards) or generate noise levels in excess of 65 dBA CNEL at the property line that could affect residents, schools or hospitals (The sources for these levels are the General Plans of the County and each city).
Criterion N-3 Create substantial and prolonged increased noise levels over the course of the construction period, especially in residential areas during evening, weekend and nighttime hours or anytime within 1,000 feet of sensitive receptors (i.e., schools, hospitals).
Criterion N-4 Expose persons to or generate excessive, continuous ground borne vibration.
e. Impacts
1) Overview
Stream Maintenance practices typically involve the use of heavy machinery and equipment. This equipment may include bulldozers and other earthmovers, dump trucks, gradalls and other wheeled vehicles. Vegetation management can be accomplished through mowing, discing, hand clearing or herbicide applications (depending on the environmental conditions of the site). Mowing and discing can be accomplished through either large tractors or mowers. The muffling of this equipment is part of the standard District practices in areas where residences, businesses or other sensitive receptors would be affected. If the project conforms to the BMPs included in the proposed program, there will be no significant permanent noise impacts to sensitive receptors. These BMPs are described in the Project Description section of this EIR and are also listed at the end of each of the following subsections of Sediment Removal, Vegetation Management and Bank Protection.
Many of the creeks have an overall width of less than 100 feet. For heavy equipment to operate in these creeks, it is necessary to either position this equipment immediately adjacent to property lines on the top of the bank (and in many cases, adjacent to backyards) or directly in the creeks.
Noise impacts from heavy equipment are limited to the hours of the week typical of other construction and maintenance activities. Stream Maintenance is generally scheduled for Monday through Friday. Field crews report to the maintenance yard at 7:00 am and arrive at work sites between 7:30 am and 8:00 am depending on the distance from the maintenance yard to the work site. Field work stops at approximately 3:30 pm and crews return to the maintenance yard. In a typical work day, equipment could be operating as long as 7 hours (Dennis Ely, pers. comm., 1996).
Because maintenance is a transient activity, no permanent change results and the significance thresholds addressing permanent noise sources do not apply. Construction type impacts are judged non-significant if they are limited to the conventional work day. In the following discussion, the potential for noise impacts is determined to be insignificant according to the District criteria. Because maintenance will produce activity in what is usually a quiet area, maintenance noise may be perceived by neighbors as disturbing or intrusive to privacy. Some of that intrusion could be minimized by advance notice so that neighbors are not surprised by unaccustomed noise.
Routine stream maintenance may occur in the vicinity of local airports, such as along the Guadalupe River adjacent to San Jose International Airport, and along streams near Reid-Hillview and San Martin Airports. Temporary noise levels may exceed 75 dBA, however, data in the CalTrans' Division of New Technology, Materials and Research Technical Analysis Notes states that jet flyovers at 1,000 feet in elevation can produce 110 dBA. Because stream maintenance is short-term and substantially quieter than jet flyovers (73 dBA vs. 110 dBA), no permanent significant impacts would occur.
2) Sediment Removal
Occasionally, it may be necessary to work outside of the normal 7:30 am to 3:30 pm time period, or work on weekends to meet special site conditions, respond to pending bad weather, or complete work before the end of the season. Except under special circumstances, it is the goal of the District maintenance staff to conform to the hours of construction activity for the jurisdiction in which the work is being performed. For example, when working within the City of Campbell, field crews do not begin before 8:00 am in keeping with that City's regulations (Dennis Ely, pers. comm., 1996).
To remove sediment from creek channels or place riprap on channel slopes, heavy equipment operates from either the top of the bank, if accessible, or within the channel itself. When working within the channel, the channel slopes would serve to shield receptors from noise generated by heavy equipment. Receptors adjacent to District facilities would be less shielded from heavy equipment operating on the top of the bank.
Monitoring of a district excavator sited on the top of the bank and removing sediment from Lower Penitencia Creek channel recorded an Leq of approximately 67 dBA at 100 feet (TRA, 1995). Given standard attenuation of 9 dB per distance doubled for soft noise, an excavator working 50 feet from a residential backyard with soft ground and intervening vegetation would generate 76 dBA. Sediment removal projects typically progress at a rate of 200 to 400 feet of creek channel per day (Dennis Ely, pers. comm., 1996). A typical subdivision lot at 60 feet wide and 50 feet from operating equipment would be subject to 73 dBA for one to two hours during sediment removal operations. As the equipment moves further along the channel, noise levels would attenuate until equivalent to the background noise levels and would no longer be perceptible.
Because these activities are temporary, they are not considered significant. The following BMPs will provide notice and reduce intrusiveness to neighbors.
BMPs which reduce or avoid all significant Noise impacts from Sediment Removal projects:
| 4.1 | Notify Local Governments of Scheduled Work |
| 4.2 | Minimize Disturbances to Surrounding Neighborhoods |
3) Vegetation Management
Of the three basic Vegetation Management methods, hand removal (which includes chain saws, weed eaters, etc) and mechanical (including mowing and discing) have the highest potential to create high noise levels. Hand removal with chain saws produces noise levels of 75 dBA at 100 feet, but chain saws are used infrequently and typically only for short periods. Weed eaters and large mowers, 65 to 70 dBA at 100 feet, are a typical noise type of moderate durations, depending upon the size and type of material to be mowed. Herbicide applications in-channel use a truck-mounted tank with a small gasoline powered pump. Noise levels for the pump are similar to noise from a lawn mower: 65 dBA at 100 feet (page 2000-7, California Department of Transportation, Division of New Technology, Materials and Research, Technical Analysis Notes, 2nd Draft March 1991).
Because these activities are temporary, they are not considered significant. The following BMPs will provide notice and reduce intrusiveness to neighbors. ,p>
| 4.1 | Notify Local Governments of Scheduled Work |
| 4.2 | Minimize Disturbances to Surrounding Neighborhoods |
4) Bank Protection
Noise levels recorded were sampled for typical bank protection activities such as a truck unloading rock, an excavator placing the rock in the stream channel, and a water truck pumping up the excess silted water from the channel bottom. Noise levels ranged from 68 to 73 dBA at 100 feet with both the truck unloading and the excavator working. Given standard attenuation, noise levels within 50 feet of working equipment would be 74 to 79 dBA. Bank protection work, such as the placement of riprap, has a wide range of progression from 40 to 200 feet per day depending on the difficulty of the characteristics of the channel. The standard 60 foot wide lot within 50 feet of riprap placement would experience the highest noise levels for 3 to 10 hours depending on the difficulty of the project. Noise levels would decrease as distance doubles and would further decrease if there is intervening vegetation between the residence and the heavy equipment.
According to the CEQA Guidelines, if a project or plan would "increase substantially the ambient noise levels of adjoining areas," the effect is considered significant. Based on the measurements taken and the close proximity (less than 50 feet) between heavy equipment and residential property boundaries, sediment removal and vegetation management activities could increase ambient noise levels by 3 dB or more at the residences in areas where the DNL currently approaches the "satisfactory" standard, or could cause the interior noise levels to exceed 45 dBA when windows in the residence are closed (exterior noise levels would exceed 65 dBA). These increases would be of short duration, typically less than one day to a few days at any given location. Bank protection work would usually be singular occurrences over the life of the program while some sediment removal operations are scheduled to repeat two or three times over the twenty year project.
Even though the levels experienced at nearby residences could exceed thresholds of significance for noise impact, the project impact would not be considered significant because of the short duration of the noise increase. In addition, the work, particularly erosion repair work, is done in many instances at the request of the homeowner. If the adjacent homeowner views the work as a benefit in protecting his or her property, the intrusiveness of any noise impact may be lessened.
Because these activities are temporary, they are not considered significant. The following BMPs will provide notice and reduce intrusiveness to neighbors.
| 4.1 | Notify Local Governments of Scheduled Work |
| 4.2 | Minimize Disturbances to Surrounding Neighborhoods |
5. Public Services and Utilities
a. Setting
Many of the urban stream channels now have or will be developed to have recreational access and trail systems. More people are taking an interest in urban creeks, and environmental education is taught at many schools, using local creeks as subjects. The District recognizes this trend and cooperates with recreation providers.
Stream channels, especially in the urban areas of the District, are crossed with pipelines, cables and other delivery systems of utilities to consumers. Many of the bridges that cross over streams link utilities from one side of the stream to the other.
b. Significance Criteria
A project would be normally considered to have a significant effect on public services if one or more of the following factors were met (CEQA Guidelines):
Criterion Pub-1 Result in a prolonged temporary or a permanent deterioration in the quality of existing recreational uses along stream corridors used for walking and outdoor passive recreational activities.
Criterion Pub-2 Result in demands for public services or utilities that exceed service capacities and would require additional facilities, staff or equipment in order to maintain acceptable service ratios, response times or other performance objectives--related to fire protection, police protection, schools or parks.
Criterion Pub-3 Cause prolonged interruption to utility services due to construction, i.e. interruption of service for longer than 8 hours.
Criterion Pub-4 Result in wastewater flows that exceed sewer line or treatment plant capacity, contribute substantial increases in flows to existing impacted sewer lines or require substantial expansion of wastewater collection or treatment facilities, the construction of which would cause significant environmental effects.
Criterion Pub-5 Exceed wastewater treatment requirements established by the RWQCB.
Criterion Pub-6 Result in water demand that exceeds capacity of the water supply or infrastructure system or would require substantial expansion of water supply, treatment or distribution facilities, i.e. project demand exceeds capacity.
Criterion Pub-7 Generate solid waste in area served by a landfill with limited and/or insufficient permitted capacity to accommodate the project.
Criterion Pub-8 Result in non-compliance with federal, state and/or local statutes and regulations related to solid waste.
c. Impacts
Residential land uses are the most potentially sensitive to such annoyance effects because the residents are there year-round, as much as 24 hours per day, as compared to park lands where visitors are transient. However, in park lands, the recreational experience is diminished if there is unwelcome noise, dust or odor. Dust and odor have been discussed in the Air Quality section of this chapter, and Noise has also been discussed in this chapter. In commercial or industrial areas, the occupants are both there for only the work day and are often in enclosed buildings with non-opening windows that are relatively insensitive to such annoyance effects.
The long term impacts of work on recreational land uses are parallel to the visual impacts. If the visual impact is considered significant, then the recreational impact may also be considered significant because the work may then reduce the quality of the recreational experience. However, the impact of the routine maintenance in designated parklands or along trail corridors would be mitigated by the BMPs that are listed in the aesthetics section of this chapter.
The District's Maintenance program does not increase the demand for neighborhood or regional park or recreational facilities. Because maintenance activities do not permanently affect existing recreational facilities or uses, this is not considered a significant impact. As is stated in Chapter II, Project Description, average sediment removal construction periods are 10 days, though they can last as long as 3 months. Vegetation management and bank protection work average less than 10 days. Because most of these activities would be performed during the weekdays, it is possible that these recreational facilities would be accessible during the weekend when most recreationalists would be present. This is not considered a significant impact.
While sediment removal projects may occur annually along the same reach of stream corridors, routine maintenance periods as listed above will not result in a prolonged temporary or a permanent deterioration in the quality of existing recreational uses along stream corridors used for walking and outdoor passive recreational activities.
The Stream Maintenance activities will not cause prolonged interruption to utility services due to construction, nor will they result in demands for public services or utilities that exceed service capacities. No new fire protection, police protection, schools or parks would be necessary as a result of the proposed program. Fire protection would be provided and improved by the vegetation management aspect of the Stream Maintenance program.
The Stream Maintenance activities will not contribute to wastewater flows and therefore will not exceed sewer line or treatment plant capacity, nor will they require substantial expansion of wastewater collection or treatment facilities.
Stream Maintenance generates dredged sediments, trash and debris, and sometimes vegetation, which are disposed of at landfills. Green waste from vegetation management activities is largely composted. While the local landfills can accommodate the annual average of 80,000 cubic yards of sediment, the District is undertaking a Solids Material Management Program to develop and implement long-term strategies for managing its solid waste materials. One of the purposes of this study is to reduce the amount of sediment disposed at landfills by finding other appropriate and beneficial uses of the sediment. Other beneficial uses of sediment which are being investigated are: reuse for streambed or wetland restoration, and in construction. Preliminary results on the feasibility of these other beneficial uses will be available in the Summer 2001 (Uday Mandlekar, SCVWD, personal communication, 3/5/01).