HomeMy Public PortalAboutResolution - 23-21- 20230913 - Addendum IS/MND Alpine RoRESOLUTION NO. 23-21
RESOLUTION OF THE BOARD OF DIRECTORS OF THE MIDPENINSULA
REGIONAL OPEN SPACE DISTRICT APPROVING AN ADDENDUM TO THE
INITIAL STUDY/MITIGATED NEGATIVE DECLARATION FOR THE ALPINE
ROAD TRAIL IMPROVEMENTS PROJECT AND APPROVING MINOR PROJECT
MODIFICATIONS
WHEREAS, pursuant to the California Environmental Quality Act (Public Resources
Code § 21000 et seq.) ("CEQA"), the Midpeninsula Regional Open Space District (the
"District") is the lead agency for environmental review of the Alpine Road Trail Improvements
Project (the "Project"); and
WHEREAS, on January 13, 2021, the Board of Directors of the District (the "Board")
adopted the Initial Study/Mitigated Negative Declaration ("IS/MND") for the Project by
adopting Resolution No. 21-01; and
WHEREAS, subsequent to the approval of the IS/MND and the Project, the District
identified certain minor modifications to the Project, including additional work to correct a trail
and creek bank slope failure at the northern end of the Project site (the "Project Modifications")
due to storm damage sustained during the Winter 2022-2023; and
WHEREAS, the Project Modifications are desirable to the District because they will: 1)
allow the District to fulfill the goal of the Project to provide a safe, low maintenance pedestrian
and bicycle trail, and to allow access to address ongoing or potential erosion and sediment
sources to receiving waters; and 2) repair the slope failure and rebuild the existing trail bed at the
Project Modifications site; and
WHEREAS, the District has prepared an Addendum to the IS/MND in accordance with
CEQA Guidelines section 15164 to describe the Project Modifications, which is attached hereto
and incorporated herein by this reference (the "Addendum"); and
WHEREAS, the Project Modifications constitute minor technical changes and would not
alter any of the conclusions in the IS/MND for the Project, or result in new significant impacts to
the environment, there is no substantial increase in the severity of previously identified impacts,
and no new mitigation measures are required.
NOW, THEREFORE, BE IT RESOLVED AND APPROVED by the Board of Directors as
follows:
1. The Addendum to the IS/MND fully describes the proposed1minor changes to the
Project and has been prepared in compliance with CEQA (Cal. Public Resources
Code section 21000 et seq.) and the CEQA Gurqelines (Cal. Code of Regs.
section 15000 et seq.)
2. The Addendum reflects the Board of Directors' independent judgment and
analysis.
1
3. In accordance with CEQA Guidelines section 15164, the Addendum, considered
together with the IS/MND, adequately addresses the potential environmental
impacts associated with the Project Modifications.
4. The documents and other materials constituting the administrative record of the
proceedings upon which the Board's decision is based are located at the
Midpeninsula Regional Open Space District, Administration Office, 5050 El
Camino Real, Los Altos, CA 94022.
5. The Addendum is hereby approved by the Board and shall be considered a part of
the District's environmental review of the Project.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
PASSED AND ADOPTED by the Board of Directors of the Midpeninsula Regional
Open Space District on September 13, 2023, at a Regular Meeting thereof, by the following vote:
AYES: CYR, GLEASON, KERSTEEN-TUCKER, KISHIMOTO, MACNIVEN,
RIFFLE
NOES: NONE
ABSTAIN: NONE
ABSENT: HOLMAN
ATTEST:
Craig Gleason, Secretary
Board of Directors
APPROVED AS TO FORM:
Hilary Stevenson, General Counsel
APPROVED:
I, the District Clerk of the Midpeninsula Regional Open Space District, hereby certify
that the above is a true and correct copy of a resolution duly adopted by the Board of Directors
of the Midpeninsula Regional Open Space District by the above vote at a meeting thereof duly
held and called on the above day.
Exhibit A: Addendum to the Initial Study/Mitigated Negative Declaration for the Alpine Road Trail
Improvements Project
2
September 2023
A D D E N D U M T O T H E A L P I N E R O A D
I M P R O V E M E N T S P R O J E C T
I N I T I A L S T U D Y/ M I T I G AT E D N E G AT I V E
D E C L A R AT I O N
SLIDE REPAIR ADJACENT TO ALPINE ROAD SITE #21
SAN MATEO COUNTY, CALIFORNIA
Exhibit A
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September 2023
A D D E N D U M T O T H E A L P I N E R O A D
I M P R O V E M E N T S P R O J E C T
I N I T I A L S T U DY/ M I T I G AT E D N E G AT I V E
D E C L A R AT I O N
SLIDE REPAIR ADJACENT TO ALPINE ROAD SITE #21
SAN MATEO COUNTY, CALIFORNIA
Submitted to:
Scott Reeves, Senior Capital Project Manager
Midpeninsula Regional Open Space District
5050 El Camino Real
Los Altos, CA 94022
Prepared by:
LSA
157 Park Place
Pt. Richmond, California 94801
510.236.6810
Project No. 20231016
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TABLE OF CONTENTS
INTRODUCTION .......................................................................................................... 3
Purpose of this Addendum ............................................................................................................ 3
CEQA Framework for Use of an Addendum .................................................................................. 4
PROJECT DESCRIPTION ................................................................................................ 5
Project Background ....................................................................................................................... 5
Prior Environmental Review .......................................................................................................... 5
Project Site .................................................................................................................................... 6
Revised Project .............................................................................................................................. 6
ANALYSIS OF POTENTIAL ENVIRONMENTAL EFFECTS ................................................. 15
Aesthetics .................................................................................................................................... 15
Agricultural and Forestry Resources ........................................................................................... 16
Air Quality .................................................................................................................................... 17
Biological Resources .................................................................................................................... 18
Cultural Resources ....................................................................................................................... 20
Energy .......................................................................................................................................... 20
Geology and Soils ........................................................................................................................ 21
Greenhouse Gas Emissions ......................................................................................................... 22
Hazards and Hazardous Materials ............................................................................................... 23
Hydrology and Water Quality ...................................................................................................... 25
Land Use and Planning ................................................................................................................ 26
Mineral Resources ....................................................................................................................... 27
Noise ............................................................................................................................................ 28
Population and Housing .............................................................................................................. 29
Public Services ............................................................................................................................. 29
Recreation ................................................................................................................................... 30
Transportation ............................................................................................................................. 30
Tribal Cultural Resources............................................................................................................. 32
Utilities and Service Systems ....................................................................................................... 33
Wildfire ........................................................................................................................................ 33
COMPARISON TO THE CONDITIONS LISTED IN CEQA GUIDELINES SECTIONS 15162
AND 15164 ............................................................................................................... 35
Substantial Changes to the Project ............................................................................................. 35
Substantial Changes in Circumstances ........................................................................................ 35
New Information ......................................................................................................................... 35
CONCLUSION ............................................................................................................ 37
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FIGURES AND TABLES
FIGURES
Figure 1: Regional Location ..................................................................................................................... 8
Figure 2: Aerial Photograph of the Project Site ...................................................................................... 9
Figure 3A: Existing Biological Resources ............................................................................................... 10
Figure 3B: Existing Biological Resources ............................................................................................... 11
Figure 3C: Existing Biological Resources ............................................................................................... 12
Figure 4: Proposed Additional Slide Repair at Site #21 ........................................................................ 13
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INTRODUCTION
This document, prepared pursuant to the California Environmental Quality Act (CEQA) and the
regulations and policies of the Midpeninsula Regional Open Space District (District), is an Addendum
to the Alpine Road Improvements Project (approved project) Initial Study/Mitigated Negative
Declaration (2021 IS/MND)1 which was adopted by the District on January 13, 2021. The 2021 IS/MND
evaluated the potential environmental impacts anticipated to result from the approved project, which
included grading, drainage, and erosion control repairs and maintenance activities along
approximately 7,400 linear feet of the existing Alpine Road Trail alignment in Coal Creek Open Space
Preserve. In Winter 2022‐2023, storms which passed throughout the region resulted in a slope failure
along the existing Alpine Road Trail alignment. The District subsequently determined that an
additional slide repair would be necessary immediately upstream of the Site #21 project site. Per
CEQA Section 15164, this Addendum evaluates whether implementation of the Slide Repair Adjacent
to Alpine Road Site #21 (revised project) would result in new or substantially more severe significant
effects or require new mitigation measures not identified in the 2021 IS/MND. The District is the CEQA
Lead Agency for environmental review of the revised project.
For purposes of this review, the District has identified the revised project evaluated in this Addendum
as an additional slide repair immediately upstream of the Site #21 project site. Section 2.0 of this
Addendum provides a detailed project description and summary of the project history, background,
location, and existing site characteristics.
As discussed in this Addendum, implementation of the revised project would not cause new significant
environmental effects not identified in the 2021 IS/MND, nor would impacts associated with the
project revisions be substantially more severe. The analyses in this Addendum also show that no
substantive changes have occurred with respect to current circumstances under which the project
would be undertaken that would cause new or substantially more severe significant environmental
effects than were identified in the 2021 IS/MND. In addition, no new information has become
available that shows that the project would cause new or substantially more severe significant
environmental effects which have not already been analyzed in the 2021 IS/MND.
PURPOSE OF THIS ADDENDUM
The purpose of this Addendum is to evaluate whether the proposed revisions to the approved project
would result in any new or substantially more severe significant environmental effects or require any
new mitigation measures not identified in the 2021 IS/MND. This Addendum, together with the 2021
IS/MND, will be used by the District when considering approval of the revised project. The 2021
IS/MND is hereby incorporated by reference.
1 Midpeninsula Regional Open Space District. 2020. Alpine Road Trail Improvements Project Initial
Study/Mitigated Negative Declaration. Prepared by LSA Associates, Inc. December.
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CEQA FRAMEWORK FOR USE OF AN ADDENDUM
CEQA Guidelines Section 15164 allows for the preparation of an Addendum to an adopted MND “if
some changes or additions are necessary but none of the conditions described in Section 15162 calling
for preparation of a subsequent EIR [or MND] have occurred.” CEQA Guidelines Section 15164
identifies the following conditions that would require preparation of a subsequent MND:
Substantial changes in the project are proposed which require major revisions to the MND due to
the involvement of new significant environmental effects or a substantial increase in the severity
of previously identified significant effects;
Substantial changes occur with respect to the circumstances under which the project is
undertaken which require major revisions to the MND due to the involvement of new significant
environmental effects or a substantial increase in the severity of previously identified significant
effects; or
New information of substantial importance, which was not known and could not have been
known with the exercise of reasonable diligence at the time of MND adoption, shows any of the
following:
○ The project will have one or more significant effects not discussed in the MND,
○ The project will result in impacts substantially more severe than those disclosed in the MND,
○ Mitigation measures or alternatives previously found not to be feasible would in fact be
feasible and would substantially reduce one or more significant effects of the project, but the
project proponent declines to adopt the mitigation measure or alternative, or
○ Mitigation measures or alternatives that are considerably different from those analyzed in
the MND would substantially reduce one or more significant effects on the environment, but
the project proponent declines to adopt the mitigation measure or alternative.
Pursuant to CEQA Guidelines Section 15164(e), this Addendum summarizes the revisions to the
approved project, any impacts associated with the revised project, and the reasons for the District’s
conclusion that proposed changes to the project and associated environmental effects do not meet
the conditions described in CEQA Guidelines Section 15162 calling for preparation of a subsequent
EIR or MND. The following chapters provide a description of the proposed revised project and provide
substantial evidence to confirm that the proposed revisions to the project do not result in any new or
more severe significant impacts and the mitigation measures included in the 2021 IS/MND are
adequate for the current project, per CEQA Guidelines Section 15164, and that no further CEQA
review is required.
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PROJECT DESCRIPTION
The following describes the proposed Slide Repair Adjacent to Alpine Road Site #21 Project (revised
project). The Midpeninsula Regional Open Space District (District) is the Lead Agency for
environmental review.
PROJECT BACKGROUND
Within the project area, Alpine Road was formerly used as a paved, County‐maintained public road
and was drained by numerous ditch relief and stream crossing culverts. The County closed the road
to vehicles at the southern end of Portola Valley in 1979 in response to neighbor concerns over illegal
uses. The District purchased what is now the Coal Creek Open Space Preserve (Coal Creek OSP), in
1982 and used Alpine Road Trail for patrol, maintenance, and emergency access until the mid‐1990s
when a large slide closed a portion of the road. The County ceased maintenance of the road at this
time. Since then, the road has been used only by pedestrians, bicyclists, and maintenance vehicles.
In 2007, District staff completed drainage improvements to stabilize the northern section of Alpine
Road Trail to prevent degradation and erosion along that segment. During the winter storms of 2013‐
2014, a sinkhole developed at the site of a 220‐foot‐long, 48‐inch‐wide culvert. Plans were developed
to slip line the culvert; however, implementation of the repair was delayed and during the winter of
2016‐2017, the road at the culvert site completely failed. The road failure at the culvert site along
with another 60‐foot failure of the road edge have further restricted District vehicle access on Alpine
Road Trail, prohibiting access north of the junction with the Meadow Trail.
Other locations along the trail alignment also require repair stemming from a lack of maintenance
over the past two decades. Existing asphalt paving has degraded in most locations to the point where
it is no longer visible. Existing culvert crossings have been assessed and found to be in need of
replacement due to inadequate capacity, cut or fill slope failures, pipe corrosion, or a combination of
the above. A lack of maintenance has led to rutting of the road surface and poorly controlled drainage.
In many locations, runoff is concentrated along the road or trail alignment due to inadequate drainage
features, causing rutting of the traveled surface, and has led to excessive surface rilling, gullies, and/or
fill slope failures. In its current condition, the road and trail alignment are rapidly degrading and
cannot be fully accessed for required maintenance.
The approved project, evaluated in the 2021 IS/MND, includes grading, drainage, and erosion control
repairs and maintenance activities along the existing Alpine Road Trail alignment to provide a safe,
low maintenance pedestrian and bicycle trail that also allows for vehicular access where economically
feasible, and to address ongoing or potential erosion and sediment sources to receiving waters.
Implementation of these improvements are currently underway.
PRIOR ENVIRONMENTAL REVIEW
An Initial Study/Mitigated Negative Declaration (2021 IS/MND)2 for the proposed Alpine Road
Improvements Project (approved project) was prepared and subsequently adopted by the District on
2 Midpeninsula Regional Open Space District. 2020. op. cit.
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January 13, 2021. The 2021 IS/MND evaluated the potential environmental impacts anticipated to
result from construction and operation of the Alpine Road Improvements Project (approved project),
which included grading, drainage, and erosion control repairs and maintenance activities along
approximately 7,400 linear feet of the existing Alpine Road Trail alignment. The approved project also
included repair of fill slope failure at the northern end of the Coal Creek OSP, where Alpine Road
meets Ciervos Street (Site #21). The purpose of the approved project is to provide a safe, low
maintenance pedestrian and bicycle trail, that also allows for vehicle access where economically
feasible, and to address ongoing and potential erosion and sediment sources to receiving waters. The
approved project improvements are needed to provide year‐round access while addressing existing
drainage, erosion, and slope stability concerns.
In Winter 2022‐2023, storms which passed throughout the region resulted in a slope failure along the
existing Alpine Road Trail alignment. The District subsequently determined that an additional slide
repair would be necessary immediately upstream of the Site #21 project site, within the San
Francisquito Creek Watershed. The addition to the approved project of the proposed slide repair
upstream of Site #21 constitutes the “revised project,” which is further described below.
PROJECT SITE
The project site consists of approximately 6.51 acres of the existing Alpine Road Trail alignment
located within the Coal Creek OSP, which is managed by the District. The Coal Creek OSP is located in
unincorporated San Mateo County (County), approximately 4 miles east of the Town of La Honda and
6 miles southwest of the City of Los Altos. The project site is generally located north of Page Mill Road,
about 0.7 miles north of its intersection with Skyline Boulevard (State Route [SR] 35). Figure 1 depicts
the project site’s local and regional context. The project area is depicted in Figure 2.
The site of the additional slide repair consists of an approximately 600‐square‐foot area along Alpine
Road Trail immediately upstream of the Site #21 project site on Corte Madera Creek, within the San
Francisquito Creek Watershed. The Alpine Road Trail alignment is located within the Coal Creek OSP,
which is managed by the District. The site of the additional slide repair as well as the existing resources
within the project area are shown on Figure 3.
REVISED PROJECT
The revised project includes one additional slide repair along Alpine Road Trail immediately upstream
of the Site #21 project site on Corte Madera Creek, within the San Francisquito Creek Watershed.
Grading activities would occur to establish construction access to the repair site, remove loose and
soft debris from the scarp3 footprint, and to establish minor benches. It is anticipated that an
approximately 600‐square‐foot temporary impact area would be required for staging and access to
the repair site and the area of excavation would be approximately 817 square feet. Excavation at the
site would result in approximately 140 cubic yards of cut material and approximately 165 cubic yards
of fill material, 6 cubic yards would be placed below the Ordinary High Water (OHW) line and 159
cubic yards above the OHW line. Rock slope protection would be placed in the scarp footprint, capped
with native soils and erosion control protections. The proposed slide repair would also require the
3 A scarp refers to a steep slope or cliff found at the margin of a flat or gently sloping area.
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removal of one tree, a California bay laurel (Umbellularia californica), which is considered an upland
tree. The remainder of the slide repair area consists of bare ground and does not contain any
vegetation. The design of the additional slide repair is provided in Figure 4.
The revised project comprises a combination of individual site repairs, general road surface upgrades,
and a limited amount of trail construction for the rerouting of the bypass trail. Individual repairs would
either be implemented simultaneously to allow completion in one season or could be phased over
several years. To date, the majority of the proposed site repairs evaluated in the 2021 IS/MND have
been completed. Construction of the remaining work, including the additional slide repair
immediately upstream of Site #21 is anticipated to take 6 weeks.
The following types of equipment would most likely be required for the general road repairs and
culvert replacements (Sites #2 through #18): a scraper, box scraper, dozer, skid‐steer, loader,
excavator, rock trucks, and a water truck. In addition to the above, Site #21 would require more
specialized equipment, including drill rig(s), a concrete pump, and a concrete truck. Similar equipment
would be needed for the additional slide repair upstream of Site #21.
As part of the revised project, best management practices (BMPs) for construction site housekeeping
would be implemented as described in the Storm Water Pollution Prevention Plan (SWPPP). These
practices include but are not limited to the following:
Limit construction to the dry season;
Limit disturbance areas to only those absolutely necessary;
Phase work to minimize the area of disturbance at any given time;
Install sediment management devices (e.g., silt fence and fiber rolls) at the downslope perimeter
of work;
Maintain functional restroom facilities on site;
Control dust emissions using water trucks;
Provide concrete washouts where necessary;
Maintain spill kits at all active work sites;
Protect all stockpiles with plastic tarps when not in use;
Remove garbage regularly; and
Seed and mulch all disturbed areas as soon as possible following grading.
Project Site
SOURCE: Esri World Street Maps (03/2022).
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FIGURE 1
Alpine Road Trail Improvements ProjectSan Mateo County, CaliforniaProject Location and Vicinity
0 1500 3000
FEET
Project Location
LEGEND
Alpine Road Trail
Bypass Trail to be Re-routed
Project Site
SOURCE: USGS 7.5-minute Topo Quad - Mindego Hill, Calif. (1995).
I:\MOS1901.01\GIS\Maps\Cultural\Figure 2_Project Area.mxd (3/24/2022)
FIGURE 2
Alpine Road Trail Improvements ProjectSan Mateo County, CaliforniaProject Area
LEGEND
Alpine Road Trail
Bypass Trail to be Re-routed
0 1000 2000
FEET
")
")")
")")")
")")
")
")
")
")
")
")
")
")
$+
Additional Slide Repair Location
Site Location 21
MA
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SOURCE: Vollmar Natural Lands Consulting (2019, 2020); LSA (2019); Google Aerial (2020)..
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FIGURE 3A
Alpine Road Trail Improvements Project
San Mateo County, California
Existing Biological Resources
LEGEND
Alpine Road Trail
Proposed Bypass Trail
")San Francisco Dusky-footed Woodrat House (Mapped in 2019)
$+Tree with Hollows (Mapped in 2019)
Vegetation (VNLC 2019)
Broadleaved Upland Forest
Broadleaved Upland Forest, Pacific Madrone
Riparian Woodland
Non-wetland Channel
Culvert
0 100 200
FEET
")
")
")
")
")
")")
")
")
")
")
")
")")
")
")
")
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")")
")
!(
Site Location 15Site Location 16
Site Location 17
Site Location 18
MA
T
C
H
L
I
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MA
T
C
H
L
I
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E
SOURCE: Vollmar Natural Lands Consulting (2019, 2020); LSA (2019); Google Aerial (2020)..
I:\MOS1901.01\GIS\Maps\Bio Report\Figure 3_Existing Biological Resources.mxd (4/22/2020)
FIGURE 3B
Alpine Road Trail Improvements Project
San Mateo County, California
Existing Biological Resources
LEGEND
Alpine Road Trail
Proposed Bypass Trail
")San Francisco Dusky-footed Woodrat House (Mapped in 2019)
!(Tree Snag (Mapped in 2019)
Vegetation (VNLC 2019)
Broadleaved Upland Forest
Broadleaved Upland Forest, Pacific Madrone
Riparian Woodland
Non-wetland Channel
Culvert
0 100 200
FEET
")
")
")
")
")
")
")
")
")
")
")
")
")
")
")
")
")")")")")
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!(!(
!(
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Site Location 5
Site Location 10 & 11
Site Location 7
Site Location 9.5
Site Location 14
Site Location 13
Site Location 12
Site Location 9
Site Location 8
Site Location 2
Site Location 3
Site Location 4
Site Location 6
MA
T
C
H
L
I
N
E
SOURCE: Vollmar Natural Lands Consulting (2019, 2020); LSA (2019); Google Aerial (2020)..
I:\MOS1901.01\GIS\Maps\Bio Report\Figure 3_Existing Biological Resources.mxd (4/22/2020)
FIGURE 3C
Alpine Road Trail Improvements Project
San Mateo County, California
Existing Biological Resources
LEGEND
Alpine Road Trail
Proposed Bypass Trail
")San Francisco Dusky-footed Woodrat House (Mapped in 2019)
!(Tree Snag (Mapped in 2019)
Vegetation (VNLC 2019)
Broadleaved Upland Forest
Broadleaved Upland Forest, Pacific Madrone
Riparian Woodland
Non-wetland Channel
Culvert
0 100 200
FEET
FIGURE 4
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Proposed Additional Slide Repair at Site #21Addendum to the Alpine Road Improvements Project IS/MND
FEET
1260
SOURCE: Waterways Consulting, Inc.
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ANALYSIS OF POTENTIAL ENVIRONMENTAL EFFECTS
The focus of this analysis is on the potential environmental impacts resulting from the revised project
and whether there would be any difference in identified impacts or required mitigation measures
from those identified in the 2021 IS/MND.
The following analysis is used to: (1) compare the environmental impacts of the revised project with
impacts expected to result from development of the approved project and evaluated in the 2021
IS/MND; (2) to identify whether the revised project would result in new or more severe significant
environmental impacts; and (3) to identify if there have been substantial changes with respect to the
circumstances under which the revised project would be undertaken since the 2021 IS/MND was
adopted that would result in new or more severe significant environmental effects.
Mitigation measures are measures that would minimize, avoid, or eliminate a significant impact. The
analysis contained herein evaluates each topic to identify whether additional mitigation measures
beyond those identified in the 2021 IS/MND would be warranted. As discussed for each topic in the
following analysis, no new mitigation measures would be required for the revised project.
This analysis confirms that the revised project is within the scope of the 2021 IS/MND, and the project
would cause no new or more severe significant effects and no new mitigation measures are required.
The following discussion has been undertaken pursuant to the provisions of CEQA Guidelines Sections
15162 and 15164 to provide the District with the factual basis for determining whether any changes
in the project, any changes in circumstance, or any new information since the 2021 IS/MND was
adopted requires additional environmental review.
AESTHETICS
Section 3.1 of the 2021 IS/MND analyzed the visual conditions of the project area. The 2021 IS/MND
identified less than significant impacts associated with aesthetics and visual resources.
Similar to the approved project, the revised project would not substantially impact a scenic vista, nor
would it substantially damage scenic resources within a State scenic highway. The revised project
would not include the construction of any new structures and would not include any alterations at
the trailheads on Alpine Road or Page Mill Road, where publicly available scenic vistas may exist.
Additionally, the project site is characterized as a rugged, hilly area covered by mixed hardwood
woodland and non‐native grasslands. Therefore, the project site is not visible from any existing scenic
vistas. The closest State scenic highway is Skyline Boulevard (SR 35), which is located approximately
0.25 mile southwest of the project site at its closest point. However, due to the topography and
vegetation of the project site and surrounding area, the project site is not visible from SR 35.
Publicly accessible vantage points near the project site consist of turnouts and parking areas along
Page Mill Road, Skyline Boulevard (SR 35), and Alpine Road. As noted above, the project site would
not be visible from any scenic vistas due to the hilly nature of the project site and the dense vegetation
that surrounds it. Further, the additional repair proposed by the revised project would ameliorate
erosion conditions, slides, and slope failures along the trail alignment, which would improve the visual
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conditions within the project site. Therefore, the revised project would have a less than significant
impact related to visual character, similar to the approved project.
Similar to the approved project, the revised project would not include any new lighting features.
District Ordinance 93‐1, Section 805.2 prohibits the use of the Coal Creek OSP by the public between
one‐half hour after sunset and sunrise. Therefore, Coal Creek OSP and trail users and their vehicles
that are parked near the project site would leave the project area during daylight hours. Vehicles
parked near the project site (and their windows) would not substantially increase glare in the area
such that views would be adversely affected. All temporary construction‐related sources of light or
glare (i.e., construction equipment headlights/safety lights) would cease following completion of
construction. Therefore, implementation of the revised project would not result in impacts associated
with light or glare that would adversely affect day or nighttime views in the project area.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts on visual resources,
nor result in new significant impacts. With adherence to applicable regulatory requirements there
would be no new or substantially more severe significant impacts related to aesthetics. No new
impacts or increase in severity of impacts related to aesthetics would occur.
AGRICULTURAL AND FORESTRY RESOURCES
Section 3.2 of the 2021 IS/MND analyzed potential impacts to agriculture and forestry resources in
the project area. The 2021 IS/MND identified either no impacts or less than significant impacts
associated with agriculture and forestry resources.
Similar to the approved project, the revised project would not convert Prime Farmland, Unique
Farmland, or Farmland of Statewide Importance (Farmland) to non‐agricultural use; conflict with
existing zoning for agricultural use or a Williamson Act contract; or conflict with existing zoning for
forest land, timberland, or timberland zoned Timberland Production. According to the State
Department of Conservation, Farmland Mapping and Monitoring Program (FMMP), the project site is
classified as “Other Land”. In addition, the Coal Creek OSP is managed as open space and is not
currently used for agricultural production. The project site is public land and zoned RM on the San
Mateo County Zoning Map. The project site is not zoned for agricultural use nor is it under a
Williamson Act contract. The project site also is not zoned for forest land or timberland. The revised
project would be located in the same vicinity as the approved project. Similar to the approved project,
the revised project would consist of grading, drainage, and erosion control repairs and maintenance
activities along approximately 7,400 linear feet of the existing Alpine Road Trail alignment, including
at the new repair site just upstream of Site #21. As such, the revised project would not result in the
introduction of any new uses on the project site.
Although trees are dispersed around the project site and some may be removed or otherwise affected
by project construction, including the removal of one California bay laurel tree, these trees are located
within an open space preserve and do not constitute forest land. Furthermore, the revised project
would be consistent with the District’s management of the Coal Creek OSP as open space. Therefore,
similar to the approved project, the revised project would not result in the loss of forest land or
conversion of forest land to non‐forest uses. Further, implementation of the revised project would
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not involve other changes in the existing environment which, due to their location or nature, could
result in conversion of farmland to non‐agricultural use or conversion of forest land to non‐forest use.
Therefore, the revised project would not adversely affect agricultural or forestry resources.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts on agriculture and
forestry resources, nor result in new significant impacts. No new impacts or increase in severity of
impacts related to agriculture and forestry resources would occur.
AIR QUALITY
Section 3.3 of the 2021 IS/MND analyzed potential air quality impacts associated with implementation
of the approved project. The 2021 IS/MND determined that all air quality impacts would result in
either less than significant impacts or less than significant impacts with mitigation incorporated.
The 2021 IS/MND indicated that construction emissions associated with the approved project would
be less than significant for ROG and PM2.5 and PM10 exhaust emissions; however, NOx emissions would
be above the BAAQMD threshold. The 2021 IS/MND also indicated that the closest sensitive receptors
that could be impacted during construction activities include the scattered rural residential uses and
open space uses managed by the District that border the site to the north and east. As such, Mitigation
Measure AIR‐1 was prescribed to reduce construction dust and NOx emissions and ensure
construction impacts would be less than significant. Similar to the approved project, although the
revised project may expose these surrounding sensitive receptors to airborne particulates, as well as
a small quantity of construction equipment pollutants (i.e., usually diesel‐fueled vehicles and
equipment), construction contractors would be required to implement BAAQMD Basic Construction
Mitigation Measures, as required by Mitigation Measure AIR‐1. With implementation of Mitigation
Measure AIR‐1, project construction emissions would be below BAAQMD significance thresholds. The
revised project would involve additional construction activities to repair the new slope failure located
upstream of Site #21, resulting in an increase in construction‐related air quality emissions. However,
the increase in construction‐related emissions would not be substantial and would not result in air
quality impacts that could not be reduced to less than significant impacts with implementation of
Mitigation Measure AIR‐1. As such, similar to the approved project, the revised project would
implement Mitigation Measure AIR‐1 to ensure construction impacts on air quality would be less than
significant.
The 2021 IS/MND determined operation of the approved project would not result in the generation
of criteria air pollutants that would exceed BAAQMD thresholds of significance due to the nature of
the project (slide repairs). As the revised project would add an additional slide repair upstream of Site
#21 and would not introduce a new use at the site that could result in increased air quality impacts,
operational air quality impacts would be similar to the approved project, and would continue to be
less than significant.
Similar to the project, the revised project would utilize various diesel‐powered vehicles and
equipment during construction that could create localized orders. However, these odors would be
temporary and are not likely to be noticeable for extended periods of time beyond the project site.
No odors would be associated with project operation. Therefore, similar to the approved project, the
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revised project would result in less than significant impacts associated with odors. In addition, the
revised project would generally implement the applicable measures outlined in the Clean Air Plan,
including Transportation Control Measures, similar to the approved project. Therefore, the revised
project would not disrupt or hinder implementation of a control measure from the Clean Air Plan.
Implementation of Mitigation Measure AIR‐1 as identified in the 2021 IS/MND would remain
applicable to the revised project and ensure that all air quality impacts would be reduced to less than
significant levels. No new impacts or increase in severity of impacts related to air quality would occur
and no additional mitigation measures are required.
BIOLOGICAL RESOURCES
Section 3.4 of the 2021 IS/MND analyzed potential impacts on biological resources with
implementation of the approved project. The 2021 IS/MND determined that all impacts would be
reduced to less than significant levels with incorporation of mitigation. The discussion of biological
resources within the project site and vicinity included in the 2021 IS/MND was based on field surveys
conducted at the project site, review of relevant documents prepared for the project, and review of
on‐line biological resources databases. Biological surveys and field assessments were conducted at
the project site on September 27, 2019; reconnaissance‐level surveys were conducted at the site on
March 4 and May 30, 2019; botanical surveys were conducted on March 21, April 25, and July 18,
2019, with additional botanical information collected on June 12, 2019; and wetland delineation
investigations were conducted on June 12 and July 18, 2019, and January 14, 2020. Additional follow‐
up botanical surveys were conducted on March 4 and April 27, 2022.
The 2021 IS/MND identified areas of potential impact, including adverse effects on special‐status
species, sensitive natural communities, wetland areas of the project site, and migratory movements
of wildlife species. To address impacts on special status species, including special status amphibians
and reptiles, nesting birds, the San Francisco dusky footed‐ woodrat, roosting bats, and steelhead, the
2021 IS/MND prescribed Mitigation Measures BIO‐1 through BIO‐5. Implementation of Mitigation
Measures BIO‐2 through BIO‐5 would also reduce impacts on migratory movements of wildlife and
nursery sites to less than significant levels. The revised project would be located within the same area
as the approved project and could result in similar impacts to special‐status species. Similar to the
approved project, the revised project would be required to implement Mitigation Measures BIO‐1
through BIO‐5, which would ensure impacts on special‐status species would be reduced to less than
significant.
To address impacts on sensitive communities, including riparian woodland, the 2021 IS/MND
prescribed Mitigation Measures BIO‐6 and BIO‐7, which require replacement of impacted riparian
trees and shrubs and impacted Pacific madrone trees and understory native plant species. In addition,
Mitigation Measure BIO‐8 was prescribed to reduce potential impacts to trees from Phytophthora (a
soil‐borne pathogen that infects trees, and woody plants, and can lead to Sudden Oak Death). These
mitigation measures would also apply to the revised project. The proposed slide repair would require
the removal of one tree, a California bay laurel (Umbellularia californica), which is considered an
upland tree. The remainder of the slide repair area consists of bare ground and does not contain any
vegetation. Though the California bay laurel tree is an upland tree, the California Department of Fish
and Wildlife (CDFW) may consider this tree to be riparian since it is growing along the bank of Corte
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Madera Creek. If so, CDFW may require replacement of the tree to be replaced at a minimum 3:1
ratio, as part of the required permit amendment. No new mitigation measures would be required.
As described in the 2021 IS/MND, the approved project was considered a self‐mitigating repair
project; therefore, no compensatory mitigation for permanent impacts to jurisdictional waters was
prescribed. To address temporary construction impacts on jurisdictional waters, including wetlands,
the 2021 IS/MND prescribed Mitigation Measure BIO‐9 requiring best management practices (BMPs)
to prevent erosion and sedimentation into stream channels, prevent impacts to upland areas outside
of designated work zones, control dust, and prevent accidental fuel or oil spills in or near stream
channels or other sensitive habitats.
The revised project would result in approximately 817 square feet (0.019 acre) of permanent impacts
to the bank of Corte Madera Creek, which is classified as “Other Waters of the United States/State.”
Approximately 50 square feet/10 linear feet of these impacts would occur within the ordinary high
water mark of the creek, while 767 square feet/25 linear feet would occur above the ordinary high
water mark. Like the approved project, the revised project would be considered a self‐mitigated
project because it would repair and stabilize the bank of Corte Madera Creek, preventing further
erosion and impacts to the creek. In accordance with State and federal requirements, impacts to the
Waters of the United States/State resulting from project implementation would require appropriate
permits from the U.S. Army Corps of Engineers, Regional Water Quality Control Board, and California
Department of Fish and Wildlife. Similar to the approved project, the revised project would be
required to implement Mitigation Measure BIO‐9, which would ensure impacts on jurisdictional
waters/wetlands would be less than significant.
In addition, although an estimated 47 native trees, including 19 coast live oak, 3 Pacific madrone, 14
big‐leaf maple, and 10 Douglas fir would be removed as part of the approved project, none of the
trees proposed for removal are considered riparian trees. Since the County would not require these
trees to be replaced, this impact was determined to be less than significant. The revised project would
require one additional tree removal, a 5‐inch diameter at breast height (dbh) California bay laurel
tree. This tree is not considered a riparian tree and due to its small size, the County would not require
this tree to be replaced. Therefore, the revised project would result in similar impacts on protected
trees as the approved project.
In addition, similar to the approved project, the revised project would not conflict with an adopted
Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional,
or State habitat conservation plans as the project site is not located within the limits of an adopted
Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional,
or State habitat conservation plan.
Implementation of Mitigation Measures BIO‐1 through BIO‐9 as identified in the 2021 IS/MND would
remain applicable to the revised project and ensure that impacts to all biological resources would be
reduced to less than significant levels. No new impacts or increase in severity of impacts related to
biological resources would occur and no additional mitigation measures are required.
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CULTURAL RESOURCES
Section 3.4 of the 2021 IS/MND analyzed potential impacts on cultural resources with implementation
of the approved project. The 2021 IS/MND determined that all impacts associated with cultural
resources would be reduced to less than significant levels with incorporation of mitigation.
The 2021 IS/MND indicated that no above‐grade structures (historic or otherwise) are present within
or in the immediate vicinity of the project site and no significant historical materials were observed
or are known to occur within the project site. In addition, literature review and a records search
indicate that no known previously recorded Native American or historic cultural resources are located
within 0.25 miles of the project site. However, the 2021 IS/MND indicated that there are previously
recorded archaeological sites within 0.5 mile of the project site. These archaeological sites are situated
on ridges, indicating a general sensitivity of such locations in the vicinity of the project site for pre‐
contact archaeological deposits and features. As no known cultural resources are present on the
project site, and the revised project would be located in the same area as the approved project,
implementation of the revised project would not impact any known or previously identified cultural
or historical resource. However, the 2021 IS/MND identified the possibility that unidentified
archaeological deposits or human remains exist on the site and may be impacted as a result of ground
disturbing activities, and prescribed Mitigation Measures CUL‐1 and CUL‐2. Similar to the approved
project, the revised project has the potential to encounter cultural deposits during construction
activities. As such, the revised project would also be required to implement Mitigation Measures CUL‐
1 and CUL‐2 identified in the 2021 IS/MND which would ensure that the impacts to cultural resources
would be reduced to a less‐than‐significant level.
In addition, similar to the project, because the revised project is anticipated to discharge fill in waters
of the United States, the District must meet requirements of Section 404 of the Clean Water Act and
would need to obtain a permit from the San Francisco District of the United States Army Corps of
Engineers. As such, the Corps will need to “take into account” the effect of the revised project in
compliance with Section 106 of the National Historic Preservation Act (NHPA).
Implementation of Mitigation Measures CUL‐1 and CUL‐2 identified in the 2021 IS/MND, which
require following proper protocols if unrecorded cultural resources or human remains are
encountered, would ensure that the impacts to cultural resources would be reduced to a less‐than‐
significant level. No new impacts or increase in severity of impacts related to cultural resources
would occur and no additional mitigation measures are required.
ENERGY
Section 3.4 of the 2021 IS/MND analyzed potential energy impacts with implementation of the
approved project and determined that energy impacts would be less than significant.
Similar to the approved project, construction of the revised project would require the use of energy
to fuel grading vehicles, trucks, and other construction vehicles, which would be primarily derived
from non‐renewable resources. However, construction activities are not anticipated to result in an
inefficient use of energy as gasoline and diesel fuel would be supplied by construction contractors
who would conserve the use of their supplies to minimize their costs on the project. In addition,
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implementation of Mitigation Measure AIR‐1, which requires equipment idling times be restricted to
5 minutes or less and construction workers to shut off idle equipment, would further reduce
construction impacts to less‐than‐significant levels. Although the revised project would involve
additional construction activities to repair the additional slope failure located upstream of Site #21,
this additional construction is not anticipated to result in energy impacts that could not be reduced
to less than significant with implementation of Mitigation Measure AIR‐1.
Typically, energy consumption is associated with fuel used for vehicle trips and electricity and natural
gas use. However, the revised project would include replacing 14 old culverts, constructing surface
drainage features (e.g., regrading road cross slope, installing reverse grade dips, and rocking the
surface of problem areas), and repairing an additional slope failure upstream of Site #21. Similar to
the approved project, the revised project would not generate additional vehicle trips through the
project area, increasing fuel usage. As such, operational energy impacts associated with the revised
project would be less than significant. In addition, similar to the approved project, the energy usage
in the project area during construction and operation would be relatively small in comparison to the
State’s available energy sources and energy impacts would be negligible at the regional level. Because
California’s energy conservation planning actions are conducted at a regional level, and because the
project’s total impact to regional energy supplies would be minor, the revised project would not
conflict with California’s energy conservation plans as described in the 2019 Integrated Energy Policy
Report.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified energy impacts, nor result in
new significant impacts. With adherence to applicable regulatory requirements there would be no
new or substantially more severe significant impacts to energy resources. No new impacts or increase
in severity of impacts related to energy would occur.
GEOLOGY AND SOILS
Section 3.4 of the 2021 IS/MND analyzed geological, seismic, and soil conditions within the project
area and potential impacts relating to geology and soils with implementation of the project. The 2021
IS/MND determined that implementation of the approved project would not cause substantial
adverse effects due to rupture of a known earthquake fault, strong seismic ground shaking, seismic
relation ground failure such as liquefaction, or landslides. Further, the 2021 IS/MND determined that
the project would not result in substantial soil erosion or the loss of topsoil or be located on an
unstable geologic units or expansive soil. The 2021 IS/MND did, however, identify potential impacts
associated with paleontological resources.
Construction of the revised project would occur in the same vicinity as the approved project and
would be subject to similar geological and soil conditions. As such, impacts related to geology and
soils would be similar to the project, and less than significant. Although mapping at the project site
indicates that the Pilarcitos Fault crosses Site #21, the Pilarcitos Fault is not believed to have been
active in the past three million years. Therefore, the revised project would not directly or indirectly
cause substantial adverse effects related to fault rupture. Similar to the approved project, completion
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of the revised project, which involves drainage improvements, flattening slopes, and slope repairs,
would improve the performance of the existing trail alignment during earthquakes. Although, 90
percent of the length of the project site and Site #21 have been mapped by the California Geological
Survey as being within areas subject to earthquake‐induced landslides and the project site is located
on an unstable geologic unit, the improvements as part of the revised project would reduce the
severity of landslides within the project site and improve the performance of the existing trail during
seismic and heavy precipitation events.
Similar to the approved project, the revised project would not include any new buildings, including
sanitary facilities. Therefore, there would be no impact related to septic tanks or alternative
wastewater disposal systems.
The 2021 IS/MND identified a potentially significant impact associated with undiscovered
paleontological resources as the project site crosses several geologic units, including Lambert Shale,
Alluvium, Vaqueros Sandstone, San Lorenzo Formation, and Butano Sandstone, which contain
foraminifera. None of these fossils would likely be unique, and the formations in which they are
contained are extensive. Therefore, it is unlikely that a significant paleontological resource would be
disturbed by the revised project. However, because the possibility of accidental discovery of
paleontological resources during project construction cannot be ruled out, the 2021 IS/MND
prescribed Mitigation Measure GEO‐1, which requires redirection of work, consultation with a
qualified paleontologist and appropriate treatment, if resources are encountered during ground
disturbance. As the revised project would be located on the same site as the approved project,
implementation of the revised project would result in similar impacts on undiscovered paleontological
resources and would also be required to implement Mitigation Measure GEO‐1. With implementation
of Mitigation Measure GEO‐1, potential impacts to paleontological resources would be reduced to
less than significant levels, similar to the approved project.
Implementation of Mitigation Measure GEO‐1 as identified in the 2021 IS/MND would remain
applicable to the revised project and ensure that impacts associated with geology and soils would be
reduced to less than significant levels. No new impacts or increase in severity of impacts related to
geology and soils would occur and no additional mitigation measures are required.
GREENHOUSE GAS EMISSIONS
Section 3.9 of the 2021 IS/MND analyzed potential impacts relating to greenhouse gas (GHG)
emissions with implementation of the project. The 2021 IS/MND determined all greenhouse gas
impacts would be less than significant.
Similar to the approved project, construction of the revised project would emit GHGs through the
operation of construction equipment and from worker vehicles, each of which typically uses fossil‐
based fuels to operate. Similar to the approved project, the revised project would implement
Mitigation Measure AIR‐1 to ensure construction GHG impacts would be less than significant.
Although the revised project would involve additional construction activities to repair the additional
slope failure located upstream of Site #21, this additional construction is not anticipated to result in
GHG impacts that could not be reduced to less than significant impacts with implementation of
Mitigation Measure AIR‐1. The 2021 IS/MND also determined operation of the approved project
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would not generate additional vehicle trips through the project area and, therefore, would not
increase mobile source emissions. In addition, the approved project would not be a source of energy
or area source emissions due to the nature of the approved project (slide repairs). As the revised
project would add an additional slide repair upstream of Site #21 and would not introduce a new use
at the site that could result in GHG emissions, GHG emission generated by the revised project would
be similar to the approved project and would be less than significant.
San Mateo County has an adopted Energy Efficiency Climate Action Plan (EECAP), which meets the
BAAQMD requirement of a Qualified GHG Reduction Strategy and outlines policies, programs, and
activities that will achieve County GHG reduction targets. As the revised project consists of grading,
drainage, and erosion control repairs and maintenance activities along approximately 7,400 linear
feet of the existing Alpine Road Trail alignment, similar to the approved project, the EECAP strategies
would not be applicable to the revised project. In addition, as discussed above, construction and
operational GHG emissions would be less than significant. Therefore, the revised project would not
generate substantial GHG emissions that would have a significant effect on the environment and
would not conflict with the strategies of the EECAP. Similar to the approved project, the revised
project would not conflict with plans, policies, or regulations adopted for the purpose of reducing
GHG emissions.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified GHG impacts, nor result in
new significant impacts. With adherence to applicable regulatory requirements there would be no
new or substantially more severe significant impacts related to GHG emissions. No new impacts or
increase in severity of impacts related to greenhouse gas emissions would occur and no additional
mitigation measures are required.
HAZARDS AND HAZARDOUS MATERIALS
Section 3.9 of the 2021 IS/MND analyzed potential impacts associated with hazards and hazardous
materials. The 2021 IS/MND identified either no impacts or less than significant impacts associated
with hazards and hazardous materials with implementation of the approved project.
Similar to the approved project, the revised project would not create a significant hazard to the public
or the environment through the routine transport, use, or disposal of hazardous materials, or through
reasonably foreseeable upset and accident conditions involving the release of hazardous materials
into the environment. The project site is located within the Coal Creek OSP and was previously used
as a County road until it was closed in the mid‐1990s. There is no indication of current or historical
hazardous materials use, storage, disposal, or release at the project site. No areas of ultramafic rock,
a type of igneous rock that may undergo metamorphosis to serpentine, a potentially asbestos‐
containing rock, are mapped in the project vicinity. Soils and rock at the site would therefore not be
expected to contain naturally occurring asbestos. Construction at the project site would require the
use and transport of hazardous materials. These materials would include fuels, oils, and other
chemicals used during construction activities. Improper use and transportation of hazardous materials
could result in accidental releases or spills, potentially posing health risks to workers, the public, and
environment. However, similar to the approved project, construction activities at the project site
would require implementation of a SWPPP, which would incorporate current BMPs for construction,
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including site housekeeping practices, hazardous material storage, inspections, maintenance, worker
training in pollution prevention measures, and containment of releases to prevent runoff via
stormwater. Although designed to protect stormwater quality, implementation of the SWPPP would
also reduce the potential impacts of hazardous materials releases during construction to a less‐than‐
significant level. In addition, similar to the approved project, operation of the revised project would
not require the routine transport, use, or disposal of significant quantities of hazardous materials.
The project site is not listed on any list of hazardous materials sites compiled pursuant to Government
Code Section 65962.5.4 The Chambers Property, located south of the project site at 7007 Page Mill
Road, was previously listed as a Leaking Underground Storage Tank (LUST) site. However, the State
Water Resources Control Board (State Water Board) issued case closure in January 1998; therefore,
no potential exists for those contaminants to have migrated and affected soils and groundwater at
the project site.5 Therefore, no significant hazard to the public or environment would be associated
with this listed site. As the revised project would be located in the same area as the approved project,
impacts associated with the project site being included on a list of hazardous materials sites compiled
pursuant to Government Code Section 65962.5 would be the same as approved project.
Similar to the approved project, the revised project would consist of repairs and improvements to an
existing trail within the Coal Creek OSP and hazardous or acutely hazardous materials would not be
handled at the project site and operation of the revised project would not result in hazardous
emissions. Further, no schools are located within 0.25 miles of the project site. As the revised project
would be located in the same area as the approved project, the revised project would not emit
hazardous emissions or handle hazardous materials within one‐quarter mile of an existing or
proposed school. The project site is also located more than 10 miles from the nearest public airports,
which include San Jose International Airport, Moffett Federal Airfield, and the Palo Alto Airport.
Therefore, there would be no impact related to airport safety hazards.
The project site is located within an existing open space preserve and is not located near a population
center. The San Mateo County Office of Emergency Services, a division of the Sheriff’s Department,
established to coordinate emergency response planning for communities in the County, identifies the
La Honda Fire Brigade and the Woodside Fire Protection District as the nearest agencies with
established emergency response plans. As the revised project would be located in the same area as
the approved project, would be a similar distance from established populations center and would
consist of the same types of improvements (e.g., slide repair), no impairment or interference with
emergency response or emergency evacuation plans from either of these agencies would occur,
similar to the approved project.
The project site is located in an area of high wildfire hazard, as mapped by the California Department
of Forestry and Fire Protection (CAL FIRE). The District coordinates with local and regional fire agencies
and undertakes a number of wildfire management practices to reduce wildfire risks on District lands.
These measures include vegetation management, mowing or brushing back vegetation from roads
4 California Environmental Protection Agency. 2020. Cortese List Data Resources. Website: calepa.ca.gov/
sitecleanup/corteselist (Accessed August 11, 2023).
5 State Water Resources Control Board. 2015. GeoTracker. Website: geotracker.waterboards.ca.gov/
profile_report.asp?global_id=T0608502029 (Accessed August 11, 2023).
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and trails, closing access points during periods of high fire risk, ensuring access for emergency vehicles,
and training personnel in fire prevention and response.6 Although trail users and workers could be
exposed to wildland fire risks during project development and operation, management of the OSP
would not change with development of the revised project. Therefore, implementation of these
measures and policies would reduce the potential wildland fire risk to a less than significant level,
similar to the approved project.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts associated with
hazards and hazardous materials, nor result in new significant impacts. With adherence to applicable
regulatory requirements there would be no new or substantially more severe significant impacts
related to hazards and hazardous materials. No new impacts or increase in severity of impacts related
to hazards and hazardous materials would occur.
HYDROLOGY AND WATER QUALITY
Section 3.10 of the 2021 IS/MND analyzed potential impacts on hydrology and water quality with
implementation of the project and identified less than significant impacts associated with hydrology
and water quality.
The project site is located in the Corte Madera Creek subbasin of the San Francisquito Creek
Watershed. Stormwater from the project site is collected in the nearby Corte Madera Creek, which
discharges to the San Francisco Bay near the city of East Palo Alto. The San Francisquito Creek Total
Maximum Daily Load (TMDL) for sediment, which is an action plan to restore clean water throughout
the watershed, calls for specific actions, including bank stabilization and landslide repair along Alpine
Road, to reduce pollutants.7 Similar to the approved project, construction activities associated with
the revised project would cause disturbance of soil during excavation work, which could adversely
impact water quality. Contaminants from construction vehicles and equipment and sediment from
soil erosion could increase the pollutant load in runoff being transported to receiving waters during
development. During construction of the revised project, contaminants from parked vehicles could
become entrained in stormwater and impact runoff quality. Similar to the approved project, the
revised project would be regulated by the NPDES Program, which is established through the federal
Clean Water Act and administered by the Water Board and San Mateo County. According to the water
quality control plans of the Water Board, any construction activities, including grading, that would
result in the disturbance of 1 acre or more would require compliance with the General Permit for
Stormwater Discharges Associated with Construction and Land Disturbance Activity (Construction
General Permit). With the additional slide repair at Site #21, the project site would be approximately
6.51 acres in size and would be subject to compliance with the Construction General Permit.
Construction of the revised project would also be subject to the Water Board’s Municipal Regional
Permit (MRP), implemented in 2015 by Order R2‐2015‐0049. Provision C.6 of the MRP addresses
construction site control for all projects. Provision C.6 requires BMPs for erosion control, run‐on and
6 Midpeninsula Regional Open Space District. 2008. Draft Wildfire Management Policy, Agenda Item 1,
Meeting 08‐27. December.
7 San Francisquito Creek Joint Powers Authority. 2004. San Francisquito Creek Watershed Analysis and
Sediment Reduction Plan Final Report. May.
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run‐off control, sediment control, active treatment systems (as necessary), good site management,
and non‐stormwater management. Additionally, several elements have been incorporated into the
approved project design to address stormwater runoff, including locating construction equipment in
flat areas where runoff is not concentrated, covering soil stockpiles, and placing sediment
containment devices around the base of stockpiles and the downslope perimeter of staging areas.
The revised project would also incorporate these elements. Similar to the approved project, all
exposed soil surfaces in the construction staging areas would be seeded and mulched prior to the
onset of the rainy season. Disturbed areas along the improved trail alignment would be seeded and
mulched as appropriate. As such, the revised project would not violate any water quality standards or
waste discharge requirements, or otherwise substantially degrade surface or groundwater quality.
The revised project would also not conflict with or obstruct implementation of a water quality control
plan.
Similar to the approved project, the revised project does not include the use of groundwater.
Increases in impervious surfaces can affect groundwater levels through a reduction in groundwater
recharge through stormwater percolation; however, based on the relatively small area of impervious
surface added by the revised project with the construction of retaining walls and other erosion control
features, this potential impact would be less than significant. Further, this relatively small increase in
impervious surface area would not substantially alter the existing drainage pattern of the area such
that substantial erosion or siltation, flooding, or the impediment of flood flows would occur. As the
revised project would not include the use of groundwater and would not substantially increase the
amount of impervious surfaces on the project site, the revised project would also not conflict with or
obstruct implementation of a sustainable groundwater management plan.
The 2021 IS/MND determined the project site is also not located flood hazard area mapped by the
Federal Emergency Management Agency (FEMA) and is a sufficient distance from the ocean and
nearby closed bodies of water such that the risk of tsunami, seiches, and project inundation is not
anticipated. As the revised project would be located in the same area as the approved project, impacts
associated with risk of inundation due to tsunami or seiche would be less than significant.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts on hydrology and
water quality, nor result in new significant impacts. With adherence to applicable regulatory
requirements there would be no new or substantially more severe significant impacts associated with
hydrology and water quality. No new impacts or increase in severity of impacts related to hydrology
and water quality would occur.
LAND USE AND PLANNING
Section 3.11 of the 2021 IS/MND analyzed potential impacts associated with land use and planning
with implementation of the approved project and identified less than significant impacts. The revised
project would be implemented in the same vicinity as the project and would be subject to the same
land use plans discussed in the 2021 IS/MND. The project site is located within the existing 508‐acre
Coal Creek OSP in unincorporated San Mateo County, which is managed as open space.
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Similar to the approved project, the revised project would not physically divide an established
community as it would consist of repairs and improvements to the existing Alpine Road Trail and
would not result in the removal of any means of access or the closure of any trails. Overall, similar to
the approved project, the revised project would enhance public access to Alpine Road Trail and the
Coal Creek OSP as a whole. Therefore, the revised project would not disrupt or divide the physical
arrangement of an established community but would instead result in an overall benefit to
connectivity within the area, similar to the approved project.
Similar to the approved project, the revised project would not conflict with applicable land use plan
and regulations that govern the site, including the San Mateo County Zoning Ordinance, San Mateo
County General Plan, and District Use and Management Plans. The project site is designated in the
County’s General Plan as General Open Space (OS) and zoned RM. The RM district was established to
meet the County’s objectives for the protection of open space and conservation. The project site is
also located within the existing Coal Creek OSP, which is managed as open space with low‐intensity
recreation and is compatible with the RM zoning district. The OS designation is intended for resource
management and production uses, and specifically encourages the District to “acquire, protect, and
make available for public use open space lands in rural areas.” Because the revised project would
result in low‐intensity recreational improvements that would enhance public access to the Coal Creek
OSP, the District’s management of the Coal Creek OSP as open space would continue, and the revised
project would be consistent with the County General Plan. Although the revised project would consist
primarily of trail and drainage improvements, it would require construction of retaining walls and
culverts. Because the revised project would obtain a permit pursuant to the requirements for
development within the RM district and the proposed uses of the revised project would help meet
the County’s objectives for the protection of open space and conservation, the revised project would
be consistent with the County Zoning Ordinance, similar to the approved project. Further, the revised
project would include drainage and erosion improvements and would result in the reopening of the
trail for public use, which would help the District meet one of its top 25 priority action of reopening
Alpine Road as detailed in the District’s 2014 Open Space Vision Plan.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified land use and planning
impacts, nor result in new significant impacts. With adherence to applicable regulatory requirements
there would be no new or substantially more severe significant impacts related to land use and
planning. No new impacts or increase in severity of impacts related to land use and planning would
occur.
MINERAL RESOURCES
Section 3.12 of the 2021 IS/MND analyzed potential impacts on mineral resources with
implementation of the approved project and identified no impacts. The San Mateo County General
Plan Mineral Resources Map does not identify any known mineral resources or mineral recovery sites
within or adjacent to the Coal Creek OSP or the project site. As the revised project would be located
in the same area as the approved project, the revised project would not result in the loss of availability
of a known mineral resource of value to the region or residents of the State, or the loss of availability
of a locally important mineral resource recovery site, similar to the approved project.
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Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts on mineral
resources, nor result in new significant impacts. There would be no new or substantially more severe
significant impacts related to mineral resources. No new impacts or increase in severity of impacts
related to mineral resources would occur.
NOISE
Section 3.13 of the 2021 IS/MND analyzed potential noise impacts associated with implementation of
the approved project. The 2021 IS/MND determined that implementation of the approved project
would result in less than significant impacts associated with temporary or permanent increase in
ambient noise levels or vibration at the project site. In addition, as the project site is not located within
two miles of a public or public use airport, the approved project would not result in the exposure of
people residing or working in the project area to excessive noise levels.
Similar to the approved project, construction of the revised project would result in a temporary
increase in ambient noise levels and ground borne vibration in the project area. The closest sensitive
receptors to the project site include the scattered rural residential uses and open space uses managed
by the District that border the site to the north and east. The 2021 IS/MND indicated that the closest
sensitive receptor may be subject to short‐term maximum construction noise reaching 79 dBA Lmax
during construction. However, construction equipment would operate at various locations within the
7,400‐linear‐foot length of the project; and as such, construction activities at any one receptor
location would occur for a limited duration. In addition, Mitigation Measure NOI‐1 was prescribed to
limit construction activities to daytime hours and would reduce potential construction‐period noise
impacts for sensitive receptors to less‐than‐significant levels. As the revised project would be located
on the same site as the approved project, implementation of the revised project would result in similar
construction noise impacts as the approved project and would be required to implement Mitigation
Measure NOI‐1. Although the revised project would involve additional construction activities to repair
the additional slope failure located upstream of Site #21, this additional construction is not anticipated
to result in noise impacts that could not be reduced to less than significant with implementation of
Mitigation Measure NOI‐1. With implementation of Mitigation Measure NOI‐1, impacts associated
with construction noise would be similar to the approved project and would be less than significant.
In addition, similar to the approved project, although construction vibration levels at the adjacent
land uses would have the potential to result in temporary annoyance (e.g., six week duration), these
vibration levels would no longer occur once construction of the revised project is completed.
Therefore, the temporary ground borne vibration and noise impacts generated by construction
equipment would be less than significant.
The 2021 IS/MND determined operation of the approved project would not result in a perceptible
increase in traffic noise levels at receptors in the project vicinity and, therefore, would not increase
ambient noise levels in the project area. As the revised project would add an additional slide repair
upstream of Site #21 and would not introduce a new use at the site that could result in increased
noise at the project site, impacts associated with operational noise levels would be similar to the
approved project and would be less than significant.
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In addition, as the revised project would be located on the same site as the approved project,
implementation of the revised project would not result in the exposure of people residing or working
in the project area to excessive noise levels as the project site is not located within two miles of a
public or public use airport.
Implementation of Mitigation Measure NOI‐1 as identified in the 2021 IS/MND would remain
applicable to the revised project and ensure that all temporary construction noise impacts would be
reduced to less than significant levels. No new impacts or increase in severity of impacts related to
noise would occur and no additional mitigation measures are required.
POPULATION AND HOUSING
Section 3.14 of the 2021 IS/MND analyzed potential impacts associated with population and housing
and identified no impacts with implementation of the approved project. Similar to the approved
project, the revised project would result in repairs and improvements to the existing Alpine Road Trail
and would not result in an increase in use. No new residential uses would result with implementation
of the revised project and no utility infrastructure would be required to serve the revised project.
Therefore, the revised project would not directly or indirectly induce population growth. In addition,
the project site is located within the Coal Creek OSP and does not contain any residential uses.
Therefore, similar to the approved project, the revised project would not displace existing people or
housing, necessitating the construction of replacement housing elsewhere.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts associated with
population and housing, nor result in new significant impacts. No new impacts or increase in severity
of impacts related to population and housing would occur.
PUBLIC SERVICES
Section 3.15 of the 2021 IS/MND analyzed potential impacts on public services with implementation
of the project and identified either no impacts or less than significant impacts associated with public
services. Similar to the approved project, the revised project would not result in the need for
additional or altered fire or police protection services and would not increase demand for school
services, new park facilities, or other public facilities or services within the vicinity of the project site.
Similar to the approved project, the revised project would not result in a substantial increase in usage
of the Coal Creek OSP and would not include housing units or other structures. Therefore, the demand
for fire and police protection services would not substantially increase with development of the
revised project. In addition, the revised project would result in better access along the existing Alpine
Road Trail, and therefore would aid in timely response for medical emergencies. Because the revised
project would not include housing or employment creation facilities and would not result in
substantial population growth, the revised project would not increase demand for school services,
new park facilities, or other public facilities or services within the vicinity of the project site.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts associated with
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public services, nor result in new significant impacts. No new impacts or increase in severity of
impacts related to public service would occur.
RECREATION
Section 3.16 of the 2021 IS/MND analyzed potential impacts on recreation with implementation of
the project and identified less than significant impacts. Similar to the approved project, the revised
project would include repairs and improvements to the existing Alpine Road Trail. These
improvements may result in a minor increase in the numbers of hikers and bicyclists based upon the
ease of access. Due to the size of the Coal Creek OSP, limited availability of parking, the extensive trail
system and linkages, the proximity of other open space preserves, and the daily hours of operation,
it is likely that the arrival of visitors would be dispersed over time on any given day, and the visitors
themselves would be dispersed throughout the Coal Creek OSP. In addition, similar to the approved
project, the revised project is not anticipated to result in a significant increase of use at the project
site or within the Coal Creek OSP. Therefore, the revised project is not expected to result in a
substantial impact to the existing trail system, existing parking or recreational resources of the Coal
Creek OSP.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts associated with
recreation, nor result in new significant impacts. No new impacts or increase in severity of impacts
related to recreation would occur.
TRANSPORTATION
Section 3.17 of the 2021 IS/MND analyzed potential transportation impacts with implementation of
the project and identified less than significant impacts. Similar to the approved project, the revised
project is anticipated to result in less than 100 net new peak‐hour trips during construction and
operation of the revised project, which is under the San Mateo County Department of Public Works
established threshold for requiring preparation of a traffic impact analysis. Similar to the approved
project, construction vehicles associated with the revised project would utilize three separate entry
points to access the construction site. As described in the 2021 IS/MND, primary access to the
construction site would be from Page Mill Road (Site Access #1) and would extend approximately
4,000 feet from Page Mill Road to Site #14. In order to accommodate construction equipment, the
trail at Site #10 would need to be widened to approximately 12 feet by cutting into the inboard edge
where a fill slope failure has narrowed the road width to approximately 6 feet. Access for construction
vehicles to areas west of Site #14 would be provided along Clouds Rest Trail (Site Access #2). Site #21
and the additional site upstream of Site #21 included in the revised project would be accessed from
the northern end of the Coal Creek OSP, using Ciervos Street via Alpine Road (Site Access #3).
Construction workers’ vehicles would park at the existing trailhead parking and along the existing trail.
The 2021 IS/MND indicated that net soils exported from the project site would equal approximately
160 cubic yards or about 10 truckloads. The revised project would include one additional repair site
located upstream of Site #21 requiring 140 cubic yards of excavation and 165 cubic yards of fill. The
165 cubic yards of fill (approximately 10 truckloads) would consist of rock, which would be imported.
The 140 cubic yards of excavated materials would remain on site as backfill and spread out along the
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trail. As such, implementation of the revised project would increase the number of truckloads from
the project site. Implementation of the revised project would result in 160 cubic yards of net soils
exported from the project site and 165 cubic yards of materials imported to the project site, requiring
approximately 20 truckloads. Over the duration of the construction period, these haul trips would
average fewer than one per day; therefore, haul trips would not affect the AM or PM peak hours,
similar to the approved project.
The 2021 IS/MND indicated that a work crew of two employees could be present at each of the initial
14 sites with four managers/foremen for the entire project area. As such, the 2021 IS/MND
determined that a total of 32 workers would be present on the project site each day. For the purposes
of calculating trip generation, no carpooling was assumed. Therefore, each worker was counted as a
separate vehicle arriving during the AM peak hour and leaving during the PM peak hour, resulting in
32 inbound trips in the AM peak hour and 32 outbound trips in the PM peak hour for a total of 64
average daily trips (ADT). The revised project would include one additional repair site located
upstream of Site #21. Using the same analysis as the 2021 IS/MND, with the incorporation of one
additional repair site, the revised project would result in an additional 8 construction workers present
on the project site each day, resulting in an additional 8 inbound trips in the AM peak hour and an
additional 8 outbound trips in the PM peak hour for a total of 16 additional average daily trips (ADT),
resulting in a total of 80 ADT for the revised project.8 This is less than 100 peak hour trips, which is
below the threshold for providing traffic impact analysis according to County guidelines. Similar to the
approved project, the revised project is not anticipated to result in additional daily or peak hour trips
upon completion of construction.
Based on the analysis presented above, the revised project would result in less than significant
impacts associated with a conflict with a program, plan, ordinance, or policy addressing the circulation
system. In addition, according to the screening threshold for small projects, defined in the State of
California Governor’s Office of Planning and Research Technical Advisory On Evaluating
Transportation Impacts in CEQA dated December 2018, “projects that generate or attract fewer than
110 trips per day generally may be assumed to cause a less‐than‐significant transportation impact.”
As the revised project is expected to generate a total of 72 average daily trips (ADT), in accordance
with the Technical Advisory, impacts related to CEQA Guidelines section 15064.3, subdivision (b) can
be assumed to be less than significant with implementation of the revised project.
Similar to the approved project, the revised project is a rehabilitation of an existing trail and is
representative of a trail use that is currently in operation and is compatible with surrounding land
uses. As such, the revised project would not result in hazards due to incompatible uses (e.g., farm
equipment). The revised project would also not result in inadequate emergency access, similar to the
project, as implementation would maintain the existing connection between the Alpine Road Trail
and the Coal Creek OSP. The existing trail is not currently maintained to handle large, heavy
emergency vehicles, which could impede emergency vehicle access in the event of a wildfire.
However, similar to the approved project, the revised project would improve access allowing for
8 It should be noted that much of the project construction has already been completed; therefore, the
potential ADT generated by the revised project would be even less than 80 trips.
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easier ingress and egress for light weight emergency vehicles, pedestrians, and bicyclists during an
emergency.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts associated with
transportation, nor result in new significant impacts. With adherence to applicable regulatory
requirements there would be no new or substantially more severe significant impacts related to
transportation. No new impacts or increase in severity of impacts related to transportation would
occur.
TRIBAL CULTURAL RESOURCES
Section 3.18 of the 2021 IS/MND analyzed potential impacts on tribal cultural resources with
implementation of the project. The 2021 IS/MND determined that all potential impacts on tribal
cultural resources could be reduced to less than significant levels with incorporation of mitigation.
Pursuant to AB 52, the District sent letters describing the approved project and maps depicting the
project site on December 6, 2019, to tribes eligible to consult with the District. On December 9, 2019,
Andrew Galvan of the Ohlone Indian Tribe responded via email to the District’s letter to request the
results of the “Phase I literature search and/or foot survey” that was completed for the project. On
December 10, 2019, the District responded to Mr. Galvan’s email with the requested information. The
District described the results of the Northwest Information Center (NWIC) records search and
provided Mr. Galvan with a copy of the resource record for P‐41‐002199, the closest pre‐contact
resource to the project site. The results of the cultural resources field survey were described. Later
that day, Mr. Galvan responded to the District’s email “... what are the professional recommendations
made by the Archaeologists based on the Lit Search and the field survey.” On December 17, 2019, the
District transmitted the draft recommendations presented in the cultural report to Mr. Galvan. On
January 15, 2020, Mr. Galvan concurred with the archaeological recommendations and did not list
any additional concerns.
The 2021 IS/MND indicated that the project site is not listed on, or eligible for listing on, the CRHR.
Additionally, the District, as Lead Agency, has not determined that there are any existing resources
significant to Native American Tribes within the project site. The 2021 IS/MND determined that with
implementation of Mitigation Measures CUL‐1 and CUL‐2, potential impacts on tribal cultural
resources would be less than significant. As the revised project would be located on the same site as
the approved project, potential impacts on tribal cultural resources would be similar to those
discussed in the 2021 IS/MND and during tribal consultation efforts. The revised project would also
be required to implement Mitigation Measures CUL‐1 and CUL‐2, and as such, potential impacts on
tribal cultural resources would be similar to the approved project and would be less than significant.
Implementation of Mitigation Measures CUL‐1 and CUL‐2 as identified in the 2021 IS/MND would
remain applicable to the revised project and ensure that impacts to all tribal cultural resources would
be reduced to less than significant levels. No new impacts or increase in severity of impacts related
to tribal cultural resources would occur and no additional mitigation measures are required.
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UTILITIES AND SERVICE SYSTEMS
Section 3.19 of the 2021 IS/MND analyzed potential impacts on utilities and service systems with
implementation of the approved project and identified either no impacts or less than significant
impacts associated with utilities and service systems. The project site does not contain any existing
water, wastewater, stormwater drainage, electric, natural gas, or telecommunication infrastructure.
Similar to the approved project, the revised project would not include the construction of any new
buildings and therefore would not require any new or relocated utility lines or connections. In
addition, similar to the approved project, the revised project would not include any new structures or
facilities that would generate wastewater or water demand, and as such, there would be no impact
to existing or future water supplies or impact on wastewater treatment services.
The District does not provide regular trash collection services, as District ordinances require users to
dispose of any refuse brought to the Coal Creek OSP and prohibit public littering or dumping of any
material onto the Coal Creek OSP. Illegal trash is removed from the Coal Creek OSP by District
maintenance crews and properly disposed of. Solid waste may be generated by users of the project
site once operational; however, similar to the approved project, the amount of solid waste generated
by the revised project would be minimal. Further, because the District would properly dispose of any
illegal litter, the revised project would not affect landfill capacity and would comply with all statutes
and regulations related to solid waste.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts associated with
utilities and service systems, nor result in new significant impacts. With adherence to applicable
regulatory requirements there would be no new or substantially more severe significant impacts
related to utilities and service systems. No new impacts or increase in severity of impacts related to
utilities and service systems would occur.
WILDFIRE
Section 3.20 of the 2021 IS/MND analyzed potential wildfire impacts with implementation of the
project and identified no impacts associated with wildfire. The project site is located in a State
Responsibility Area (SRA) for fire hazards, as mapped by CAL FIRE, and is located within a high fire
hazard severity zone. As the revised project would be located in the same area as the approved
project, no impairment or interference with emergency response or emergency evacuation plans
would occur due to the distance of the project site from population centers and the nature of the
revised project. Similar to the approved project, the District would continue to coordinate with local
and regional fire agencies and undertake a number of wildfire management practices. Additionally,
one of the BMPs identified in the 2021 IS/MND and included in the approved project design would be
to restore the project site to pre‐project conditions after the completion of the work. The revised
project would be required to implement this BMP; therefore, the revised project would not
exacerbate wildfire risks.
Similar to the approved project, the revised project would include repairs and improvements along
the existing Alpine Road Trail, including the additional repair site located upstream of Site #21. These
improvements would include the maintenance of vehicular access (generally a minimum of 12 feet)
S LIDE R EP AIR A DJ ACE NT TO A LPINE R OAD S ITE #21
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A DDEN DUM TO THE A LPINE R OAD I MP ROVE MEN TS P ROJE CT IS/MND
S EPTE MBER 2023
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along approximately 2,600 linear feet of road, extending from Page Mill Road to Site #10. The revised
project would not include any buildings and therefore would not require emergency water sources,
power lines, or other utilities to be installed. The repairs would consist of grading, drainage, and
erosion control and would therefore reduce the potential for downslope or downstream flooding or
landslides. The revised project would also include the repair of a fill slope failure at Site #21 and the
repair of a fill slope failure at a site located upstream of Site #21. As such, similar to the approved
project, the revised project would not exacerbate fire risk associated with the installation or
maintenance of infrastructure and would not expose people or structures to significant risks, including
downslope flooding or landsides.
Based on the information in the 2021 IS/MND and this environmental analysis, the revised project
would not substantially increase the severity of the previously identified impacts associated with
wildfire, nor result in new significant impacts. With adherence to applicable regulatory requirements
there would be no new or substantially more severe significant impacts related to wildfire. No new or
substantially more severe significant effects related to wildfire would occur.
A DDEN DUM TO THE A LPINE R OAD I MP ROVE MEN TS P ROJE CT IS/MND
S EPTE MBER 2023
S LIDE R EP AIR A DJ ACE NT TO A LPINE R OAD S ITE #21
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COMPARISON TO THE CONDITIONS LISTED IN CEQA GUIDELINES SECTIONS
15162 AND 15164
The following discussion summarizes the reasons that a new or subsequent IS/MND or EIR, pursuant
to CEQA Guidelines Sections 15162, is not required to evaluate the environmental effects of the
revised project. The analyses prepared for each CEQA topic in the previous sections demonstrate that
the revised project is addressed within the scope of the 2021 IS/MND, and no new significant impacts
are identified, no significant impacts are more severe, no new mitigation measures are required, and
no substantial changes to the existing environmental circumstances have occurred leading to new or
more severe previously identified significant impacts.
SUBSTANTIAL CHANGES TO THE PROJECT
As discussed in Section 2.0, Project Description, the revised project has not substantially changed from
the project identified and evaluated in the 2021 IS/MND. Additionally, the changes identified for the
revised project do not substantially change the scope of proposed improvements proposed and
evaluated in the 2021 IS/MND. As such, an Addendum is the appropriate document to address these
minor modifications rather than a Subsequent IS/MND or EIR.
SUBSTANTIAL CHANGES IN CIRCUMSTANCES
As described for each CEQA topic in the previous sections, the existing environmental conditions or
circumstances in and around the project site have not changed such that implementation of the
proposed minor modifications to the project would result in new significant environmental effects or
a substantial increase in the severity of significant environmental effects identified in the 2021
IS/MND, and thus major revisions to the 2021 IS/MND are not required.
NEW INFORMATION
No new information of substantial importance, which was not known and could not have been known
when the 2021 IS/MND was adopted, has been identified to show that the proposed minor
modifications to the project would be expected to result in: 1) new significant environmental effects
not identified in the 2021 IS/MND; 2) substantially more severe environmental effects than shown in
the 2021 IS/MND; 3) mitigation measures or alternatives previously determined to be infeasible
would in fact be feasible and would substantially reduce one or more significant effects of the project,
but the project sponsor declines to adopt the mitigation measure or alternative; or 4) mitigation
measures or alternatives which are considerably different from those identified in the 2021 IS/MND
would substantially reduce one or more significant effects of the project but the project sponsor
declines to adopt the mitigation measure or alternative. In addition, the proposed minor
modifications to the project would require no new mitigation measures because no new or
substantially more severe impacts are expected beyond those identified in the 2021 IS/MND.
S LIDE R EP AIR A DJ ACE NT TO A LPINE R OAD S ITE #21
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A DDEN DUM TO THE A LPINE R OAD I MP ROVE MEN TS P ROJE CT IS/MND
S EPTE MBER 2023
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A DDEN DUM TO THE A LPINE R OAD I MP ROVE MEN TS P ROJE CT IS/MND
S EPTE MBER 2023
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CONCLUSION
On the basis of the evaluation presented above, the revised project, if implemented, would not trigger
any of the conditions listed under the CEQA Framework for Use of an Addendum section of this
Addendum, requiring preparation of a subsequent or supplemental IS/MND. Thus, this Addendum
satisfies the requirements of CEQA Guidelines Section 15162 and 15164. The implementation of the
additional slide repair would not introduce new significant environmental effects, substantially
increase the severity of previously identified significant environmental effects or demonstrate that
mitigation measures or alternatives previously found not to be feasible would in fact be feasible. The
proposed changes that would be implemented as part of the revised project would not alter the
findings in the 2021 IS/MND. In addition, no change has occurred with respect to the circumstances
surrounding the project that would cause new or substantially more severe significant environmental
effects than identified in the 2021 IS/MND, and no new information has become available that shows
that the project would cause significant environmental effects not already analyzed in the 2021
IS/MND. Therefore, no further environmental review is required beyond this Addendum to the 2021
IS/MND.
S LIDE R EP AIR A DJ ACE NT TO A LPINE R OAD S ITE #21
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S EPTE MBER 2023
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