Apx E_Paleo Resources Assessment
Appendix E
Paleontological Resources Assessment
Appendix E
Paleontological Resources Assessment
Kimley»Horn
Paleontological Resources Assessment
for the
1515 Walnut Grove Avenue Project
in the
City of Rosemead
Los Angeles County, California
Prepared by:
Jamie Parra, MA, RPA, and Christina Livingston, MA
Kimley-Horn and Associates, Inc.
September 2025
Paleontological Resources Assessment
for the
1515 Walnut Grove Avenue Project
in the
City of Rosemead
Los Angeles County, California
Kimley»Horn
Expect More. Experience Better.
Prepared by:
Jamie Parra, MA, RPA, and Christina Livingston, MA
Kimley-Horn and Associates, Inc.
September 2025
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
September 2025
Page | ii
TABLE OF CONTENTS
1.0 INTRODUCTION ............................................................................................................................1
1.1 Project Description ............................................................................................................. 1
1.2 Regulatory Setting............................................................................................................... 1
2.0 METHODS ....................................................................................................................................4
3.0 PROJECT SETTING .........................................................................................................................4
3.1 Natural Setting .................................................................................................................... 4
3.2 Geologic Setting .................................................................................................................. 4
4.0 RESULTS .......................................................................................................................................5
4.1 Paleontological Record Search ........................................................................................... 5
4.2 Database Review ................................................................................................................. 6
5.0 CONCLUSION AND RECOMMENDATIONS ......................................................................................8
5.1 Paleontological Resources .................................................................................................. 8
5.2 Recommendations .............................................................................................................. 8
6.0 REFERENCES ............................................................................................................................... 10
APPENDICES
Appendix A: Paleontological Record Search Results
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
TABLE OF CONTENTS
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APPENDICES
Appendix A: Paleontological Record Search Results
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Kimley»Horn
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Paleontological Resources Assessment
September 2025
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1.0 INTRODUCTION
Kimley-Horn and Associates, Inc. (Kimley-Horn) conducted a Paleontological Resources Assessment for
the 1515 Walnut Grove Avenue Project (Project) located within the City of Rosemead (Lead Agency) in Los
Angeles County, California. This study was completed to support the Lead Agency’s review of potential
impacts to paleontological resources as a result of the proposed Project. A literature review and records
search were conducted for the property to identify the likelihood of present paleontological resources
that would be adversely impacted by the Project.
1.1 Project Description
The Project area is located in the south-central portion of the City of Rosemead, in the County of Los
Angeles (Figure 1). Specifically, the Project area is located at 1515 Walnut Grove Avenue and situated on
Assessor Parcel Number 5279-027-001 (Figure 2). The property is currently bounded by Walnut Grove
Avenue to the east, commercial buildings to the north, single-family housing to the west, and institutional
uses to the south.
The Project will involve the demolition of an existing Southern California Edison building and detached
central plant building and will construct 191 townhome dwelling units. Vehicular access provisions for the
property would be provided via two full-movement unsignalized driveways along Walnut Grove Avenue.
The proposed Opening Year for the Project is 2029. The Project will be developed in a single project phase.
1.2 Regulatory Setting
Paleontological resources are limited, nonrenewable resources of scientific, cultural, and educational
value and are afforded protection under federal and state laws and regulations. This study satisfies project
requirements in accordance with state regulations, as well as guidelines and criteria specified by the
Society of Vertebrate Paleontology (1995, 2010).
California Environmental Quality Act
California Environmental Quality Act (CEQA) is the principal statute governing environmental review of
projects occurring in the State and is codified at Public Resources Code (PRC) Section 21000 et seq. CEQA
requires lead agencies to determine if a proposed project would have a significant effect on the
environment, including significant effects on paleontological resources. Guidelines for the
Implementation of CEQA, as amended December 1, 2016 (Title 14, Chapter 3, California Code of
Regulations [CCR] 15000 et seq.), define procedures, types of activities, persons, and public agencies
required to comply with CEQA.
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
1.0 INTRODUCTION
Kimley-Horn and Associates, Inc. (Kimley-Horn) conducted a Paleontological Resources Assessment for
the 1515 Walnut Grove Avenue Project (Project) located within the City of Rosemead (Lead Agency) in Los
Angeles County, California. This study was completed to support the Lead Agency’s review of potential
impacts to paleontological resources as a result of the proposed Project. A literature review and records
search were conducted for the property to identify the likelihood of present paleontological resources
that would be adversely impacted by the Project.
1.1 Project Description
The Project area is located in the south-central portion of the City of Rosemead, in the County of Los
Angeles (Figure 1). Specifically, the Project area is located at 1515 Walnut Grove Avenue and situated on
Assessor Parcel Number 5279-027-001 (Figure 2). The property is currently bounded by Walnut Grove
Avenue to the east, commercial buildings to the north, single-family housing to the west, and institutional
uses to the south.
The Project will involve the demolition of an existing Southern California Edison building and detached
central plant building and will construct 191 townhome dwelling units. Vehicular access provisions for the
property would be provided via two full-movement unsignalized driveways along Walnut Grove Avenue.
The proposed Opening Year for the Project is 2029. The Project will be developed in a single project phase.
1.2 Regulatory Setting
Paleontological resources are limited, nonrenewable resources of scientific, cultural, and educational
value and are afforded protection under federal and state laws and regulations. This study satisfies project
requirements in accordance with state regulations, as well as guidelines and criteria specified by the
Society of Vertebrate Paleontology (1995, 2010).
California Environmental Quality Act
California Environmental Quality Act (CEQA) is the principal statute governing environmental review of
projects occurring in the State and is codified at Public Resources Code (PRC) Section 21000 et seq. CEQA
requires lead agencies to determine if a proposed project would have a significant effect on the
environment, including significant effects on paleontological resources. Guidelines for the
Implementation of CEQA, as amended December 1, 2016 (Title 14, Chapter 3, California Code of
Regulations [CCR] 15000 et seq.), define procedures, types of activities, persons, and public agencies
required to comply with CEQA.
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City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
September 2025
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Figure 1: Project Vicinity Map
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
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Figure 1: Project Vicinity Map
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City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
September 2025
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Figure 2: Project Area Map
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
Project Area Map
0 375 75 150 225 300 -US Feet 3 Project Area
Figure 2: Project Area Map
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City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
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Public Resources Code Section 5097.5
Requirements for paleontological resource management are included in the PRC Division 5, Chapter 1.7,
Section 5097.5, and Division 20, Chapter 3, Section 30244. These statutes prohibit the removal, without
permission, of any paleontological site or feature from lands under the jurisdiction of the state or any city,
county, district, authority, or public corporation, or any agency thereof. Consequently, local agencies are
required to comply with PRC Section 5097.5 for their own activities, including construction and
maintenance, as well as for permit actions (e.g., encroachment permits) undertaken by others. PRC
Section 5097.5 also establishes the removal of paleontological resources as a misdemeanor and requires
reasonable mitigation of adverse impacts to paleontological resources from developments on public
(state, county, city, and district) lands.
2.0 METHODS
This report was prepared pursuant to CEQA. This study identifies whether any paleontological resources
were previously recorded within the Project area, the potential for unrecorded paleontological resources,
and whether any present paleontological resources are potentially significant under the above-referenced
regulations. Tasks completed include:
• A paleontological resource record search through the Natural History Museum of Los Angeles
County (NHMLAC) for the Project area and vicinity,
• Review of the University of California Museum of Paleontology (UCMP) online database,
• Review of geological and historical maps and imagery to identify the paleontological resource
sensitivity of the Project area,
• Recommendations regarding any identified or potential paleontological resources.
3.0 PROJECT SETTING
3.1 Natural Setting
The proposed Project is situated in an urban environment within the San Gabriel Valley. The San Gabriel
Valley ranges around 400 square miles and spans from the San Gabriel Mountains (north), Los Angeles
(west), Pomona (east), and Orange County (south) (Cheng 2014). This area has an elevation between 200
to 900 feet above mean sea level (amsl). The Project area is situated along the East Montebello fault line
(U.S. Geological Survey 2025). The soil composition of the Project area consists of Urban land-Pico-Metz
complex with the underlain soil considered to be Holocene-age loam from an alluvial fan (SoilWeb 2025).
However, the Project area is currently developed with no native soil visible on the surface.
3.2 Geologic Setting
The San Gabriel Valley is situated in the greater Los Angeles Basin. The Los Angeles Basin is a structural
depression that is approximately 50 miles long and 20 miles wide that developed as a result of tectonic
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
Public Resources Code Section 5097.5
Requirements for paleontological resource management are included in the PRC Division 5, Chapter 1.7,
Section 5097.5, and Division 20, Chapter 3, Section 30244. These statutes prohibit the removal, without
permission, of any paleontological site or feature from lands under the jurisdiction of the state or any city,
county, district, authority, or public corporation, or any agency thereof. Consequently, local agencies are
required to comply with PRC Section 5097.5 for their own activities, including construction and
maintenance, as well as for permit actions (e.g., encroachment permits) undertaken by others. PRC
Section 5097.5 also establishes the removal of paleontological resources as a misdemeanor and requires
reasonable mitigation of adverse impacts to paleontological resources from developments on public
(state, county, city, and district) lands.
2.0 METHODS
This report was prepared pursuant to CEQA. This study identifies whether any paleontological resources
were previously recorded within the Project area, the potential for unrecorded paleontological resources,
and whether any present paleontological resources are potentially significant under the above-referenced
regulations. Tasks completed include:
eo A paleontological resource record search through the Natural History Museum of Los Angeles
County (NHMLAC) for the Project area and vicinity,
eo Review of the University of California Museum of Paleontology (UCMP) online database,
eo Review of geological and historical maps and imagery to identify the paleontological resource
sensitivity of the Project area,
eo Recommendations regarding any identified or potential paleontological resources.
3.0 PROJECT SETTING
3.1 Natural Setting
The proposed Project is situated in an urban environment within the San Gabriel Valley. The San Gabriel
Valley ranges around 400 square miles and spans from the San Gabriel Mountains (north), Los Angeles
(west), Pomona (east), and Orange County (south) (Cheng 2014). This area has an elevation between 200
to 900 feet above mean sea level (amsl). The Project area is situated along the East Montebello fault line
(U.S. Geological Survey 2025). The soil composition of the Project area consists of Urban land-Pico-Metz
complex with the underlain soil considered to be Holocene-age loam from an alluvial fan (SoilWeb 2025).
However, the Project area is currently developed with no native soil visible on the surface.
3.2 Geologic Setting
The San Gabriel Valley is situated in the greater Los Angeles Basin. The Los Angeles Basin is a structural
depression that is approximately 50 miles long and 20 miles wide that developed as a result of tectonic
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forces and the San Andreas Fault zone (Critelli et al. 1995; Ingersoll and Rumelhart 1999). Sediments have
eroded into the Basin from the surrounding mountains since the middle Miocene (13 million years ago),
resulting in thousands of feet of sediment accumulation within the Basin. When the sea level dropped
during the Pleistocene (2.58 million to 11,700 years ago), the uppermost layers of the Basin then became
composed of alluvial sediments (Yerkes et al. 1965). In the present day, the Project area is underlaid by
geologic deposits from the Holocene epoch (Figure 3). The deposits are derived from an undivided alluvial
fan and valley and consist of young sand (Qyfa) (Tan 2000). Pleistocene-aged deposits (Qof) are located
immediately west and south of the Project area. The Pico Formation (Tfuc), which dates to the Pliocene
epoch, is located further to the southwest. The Alhambra Wash runs in a southeasterly direction
immediately north of the Project. Young geologic deposits associated with the wash encompass the
Project area and to the east (Tan 2000).
Figure 3: Geologic Map of the Project Area (Indicated with Red Star)
4.0 RESULTS
4.1 Paleontological Record Search
Kimley-Horn conducted a paleontological record search for the Project area and vicinity through the
NHMLAC. The repository responded on August 10, 2025, and indicated that no previously recorded fossil
localities were identified in the Project area. However, NHMLAC noted that fossil localities have been
recorded near the Project area. The repository provided information about the closest known fossil
localities, as outlined in Table 1. Though resources were recorded nearby, it is notable that the geologic
deposits where the fossil localities were recorded are not consistent with the geologic deposits within the
Project area. A copy of the repository’s response is included in Appendix A: Paleontological Record Search
Results.
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
forces and the San Andreas Fault zone (Critelli et al. 1995; Ingersoll and Rumelhart 1999). Sediments have
eroded into the Basin from the surrounding mountains since the middle Miocene (13 million years ago),
resulting in thousands of feet of sediment accumulation within the Basin. When the sea level dropped
during the Pleistocene (2.58 million to 11,700 years ago), the uppermost layers of the Basin then became
composed of alluvial sediments (Yerkes et al. 1965). In the present day, the Project area is underlaid by
geologic deposits from the Holocene epoch (Figure 3). The deposits are derived from an undivided alluvial
fan and valley and consist of young sand (Qyfa) (Tan 2000). Pleistocene-aged deposits (Qof) are located
immediately west and south of the Project area. The Pico Formation (Tfuc), which dates to the Pliocene
epoch, is located further to the southwest. The Alhambra Wash runs in a southeasterly direction
immediately north of the Project. Young geologic deposits associated with the wash encompass the
Project area and to the east (Tan 2000).
ATE or Ne A 2
Figure 3: Geologic Map of the Project Area (Indicated with Red Star)
4.0 RESULTS
4.1 Paleontological Record Search
Kimley-Horn conducted a paleontological record search for the Project area and vicinity through the
NHMLAC. The repository responded on August 10, 2025, and indicated that no previously recorded fossil
localities were identified in the Project area. However, NHMLAC noted that fossil localities have been
recorded near the Project area. The repository provided information about the closest known fossil
localities, as outlined in Table 1. Though resources were recorded nearby, it is notable that the geologic
deposits where the fossil localities were recorded are not consistent with the geologic deposits within the
Project area. A copy of the repository’s response is included in Appendix A: Paleontological Record Search
Results.
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Table 1: Previously Recorded Fossil Localities Near the Project Area
Locality Number Location Formation Taxa Depth Approx. Distance LACM IP 11852 Merced Hills to the north of Whittier Narrows Recreation Area
Pico Formation (conglomerate bed in siltstone)
Invertebrates, including tusk shell (Dentalum neohexagonium) and foraminifera
Unknown 1 mile south
LACM IP 2896 T2S; R12W. El Monte Quad Pico Formation Invertebrates (uncatalogued) Surface 2 miles south
LACM VP 3363 W of Monterey Pass Road in Coyote Pass; Monterey Park
Unknown formation (Pleistocene; sand and silt)
Horse (Equus) Unknown 7 miles west
LACM VP 7702 Intersection of 26th St and Atlantic Blvd, Bell Gardens
Unknown formation (Pleistocene; silt)
Fish (Gasterosteus); snake (Colubridae), rodents (Thomomys,
Microtus, Reithrodontomys); rabbit (Sylvilagus)
30 feet bgs 9 miles southwest
4.2 Database Review
Kimley-Horn reviewed the UCMP online database to identify any previously recorded paleontological
resources in the Project area or vicinity. The UCMP did not report any fossil localities in Los Angeles County
that date to the Holocene or Pleistocene epochs. Though there are no Pleistocene-aged deposits within
the Project area, Kimley-Horn searched the UCMP for fossil localities from that epoch due to the Project’s
adjacency to some Pleistocene-aged deposits.
Kimley-Horn reviewed a database of historic maps and aerial imagery for the Project area. Historic aerial
imagery is available for the Project area from 1948 through present, and historic topographic maps are
available from 1894 through present (Historic Aerials 2025). The aerials show that the Project area was
developed as farmland before the 1940s (Figure 4). By 1980, the Project area was vacant and no longer
operated as agricultural land (Figure 5). A commercial property was developed in the Project area
between 1980 and 1987 (Figure 6). Little to no changes have occurred to the built environment since that
time.
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
Table 1: Previously Recorded Fossil Localities Near the Project Area
ocality Location Formation Taxa App
umber Dis’
LACM IP Merced Hills to Pico Formation Invertebrates, Unknown | 1 mile
11852 the north of (conglomerate including tusk shell south
Whittier Narrows | bed in siltstone) (Dentalum
Recreation Area neohexagonium)
and foraminifera
LACM IP 2896 | T2S; R12W. El Pico Formation Invertebrates Surface 2 miles
Monte Quad (uncatalogued) south
LACM VP 3363 | W of Monterey Unknown Horse (Equus) Unknown | 7 miles
Pass Road in formation west
Coyote Pass; (Pleistocene;
Monterey Park sand and silt)
LACM VP 7702 | Intersection of Unknown Fish 30 feet 9 miles
26th St and formation (Gasterosteus); bgs southwest
Atlantic Blvd, Bell | (Pleistocene; silt) | snake
Gardens (Colubridae),
rodents
(Thomomys,
Microtus,
Reithrodontomys);
rabbit (Sylvilagus)
4.2 Database Review
Kimley-Horn reviewed the UCMP online database to identify any previously recorded paleontological
resources in the Project area or vicinity. The UCMP did not report any fossil localities in Los Angeles County
that date to the Holocene or Pleistocene epochs. Though there are no Pleistocene-aged deposits within
the Project area, Kimley-Horn searched the UCMP for fossil localities from that epoch due to the Project's
adjacency to some Pleistocene-aged deposits.
Kimley-Horn reviewed a database of historic maps and aerial imagery for the Project area. Historic aerial
imagery is available for the Project area from 1948 through present, and historic topographic maps are
available from 1894 through present (Historic Aerials 2025). The aerials show that the Project area was
developed as farmland before the 1940s (Figure 4). By 1980, the Project area was vacant and no longer
operated as agricultural land (Figure 5). A commercial property was developed in the Project area
between 1980 and 1987 (Figure 6). Little to no changes have occurred to the built environment since that
time.
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Paleontological Resources Assessment
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Figure 4: Historic Aerial Image of the Project Area in 1948
Figure 5: Historic Aerial Image of the Project Area in 1980
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
SO Oma NIN yy Chats se | | “
Figure 5: Historic Aerial Image of the Project Area in 1980
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Paleontological Resources Assessment
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Figure 6: Historic Aerial Image of the Project Area in 1987
5.0 CONCLUSION AND RECOMMENDATIONS
5.1 Paleontological Resources
Kimley-Horn did not identify any previously recorded paleontological resources in the Project area. The
NHMLAC reported that fossil localities have been recorded near the Project area, though were located
within different types of geologic deposits. The Project area contains deposits of young geologic age and,
therefore, has a low paleontological sensitivity. The Pico Formation from the Pliocene epoch is
paleontologically sensitive, but it is located one mile south of the Project area.
5.2 Recommendations
The paleontological sensitivity of the Project area is low, but there is still potential for paleontological
resources to be inadvertently discovered during construction depending on the depth of proposed
disturbance and the location of deeper, older soils underlying the mapped Holocene-aged deposits. As
such, Kimley-Horn recommends a mitigation measure or condition of approval that outlines the process
for inadvertent discovery. With this measure or condition in place, any potential impacts to
paleontological resources would be less than significant. Example language is included below.
• PALEO-1: Inadvertent Discoveries of Paleontological Resources
Should paleontological resources be inadvertently encountered, construction activities shall be
temporarily halted within 50 feet of the find so that the resource can be evaluated by a
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
Figure 6: Historic Aerial Image of the Project Area in 1987
5.0 CONCLUSION AND RECOMMENDATIONS
5.1 Paleontological Resources
Kimley-Horn did not identify any previously recorded paleontological resources in the Project area. The
NHMLAC reported that fossil localities have been recorded near the Project area, though were located
within different types of geologic deposits. The Project area contains deposits of young geologic age and,
therefore, has a low paleontological sensitivity. The Pico Formation from the Pliocene epoch is
paleontologically sensitive, but it is located one mile south of the Project area.
5.2 Recommendations
The paleontological sensitivity of the Project area is low, but there is still potential for paleontological
resources to be inadvertently discovered during construction depending on the depth of proposed
disturbance and the location of deeper, older soils underlying the mapped Holocene-aged deposits. As
such, Kimley-Horn recommends a mitigation measure or condition of approval that outlines the process
for inadvertent discovery. With this measure or condition in place, any potential impacts to
paleontological resources would be less than significant. Example language is included below.
eo PALEO-1: Inadvertent Discoveries of Paleontological Resources
Should paleontological resources be inadvertently encountered, construction activities shall be
temporarily halted within 50 feet of the find so that the resource can be evaluated by a
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City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
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paleontologist meeting the Society of Vertebrate Paleontology (SVP) professional qualifications.
A paleontologist shall temporarily divert or redirect grading and excavation activities in the area
of the exposed material to facilitate evaluation and, if necessary, salvage. The paleontologist shall
then assess the discovered material(s) and prepare a memorandum evaluating the impact. The
Applicant shall then comply with the recommendations of the evaluating paleontologist, and a
copy of the survey report shall be submitted to the Natural History Museum of Los Angeles
County. Ground disturbing activities may resume once the paleontologist’s recommendations
have been implemented.
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
paleontologist meeting the Society of Vertebrate Paleontology (SVP) professional qualifications.
A paleontologist shall temporarily divert or redirect grading and excavation activities in the area
of the exposed material to facilitate evaluation and, if necessary, salvage. The paleontologist shall
then assess the discovered material(s) and prepare a memorandum evaluating the impact. The
Applicant shall then comply with the recommendations of the evaluating paleontologist, and a
copy of the survey report shall be submitted to the Natural History Museum of Los Angeles
County. Ground disturbing activities may resume once the paleontologist’s recommendations
have been implemented.
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6.0 REFERENCES
Cheng, Wendy
2014 A Brief History (and Geography) of the San Gabriel Valley. PBS SoCal. A Brief History (and
Geography) of the San Gabriel Valley | History & Society | PBS SoCal.
Critelli, S. P. Rumelhart, and R. Ingersoll
1995 Petrofacies and Provenance of the Puente Formation (Middle to Upper Miocene), Los
Angeles Basin, Southern California: Implications for Rapid Uplift and Accumulation Rates.
Journal of Sedimentary Research A65: 656-667.
Historic Aerials
2025 Historic Aerial Viewer. https://www.historicaerials.com/viewer.
Ingersoll, R. V. and P. E. Rumelhart
1999 Three-stage Basin Evolution of the Los Angeles Basin, Southern California. Geology 27:
593-596.
SoilWeb
2025 National Resources Conservation Service Soil Survey Program website.
https://casoilresource.lawr.ucdavis.edu/gmap/.
Tan, S.S.
2000 Geologic Map of the El Monte 7.5-Minute Quadrangle, Los Angeles County, California.
California Division of Mines and Geology. Open-File Report OFR-98-29.
U.S. Geological Survey
2025 U.S. Quaternary Faults.
https://usgs.maps.arcgis.com/apps/webappviewer/index.html?id=5a6038b3a1684561a
9b0aadf88412fcf.
Yerkes, R.F., T.H. McCulloh, J.E. Schollhamer, and J.G. Vedder
1965 Geology of the Los Angeles Basin: An Introduction. Geological Survey Professional Paper
420-A.
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
6.0 REFERENCES
Cheng, Wendy
2014 A Brief History (and Geography) of the San Gabriel Valley. PBS SoCal. A Brief History (and
Geography) of the San Gabriel Valley | History & Society | PBS SoCal.
Critelli, S. P. Rumelhart, and R. Ingersoll
1995 Petrofacies and Provenance of the Puente Formation (Middle to Upper Miocene), Los
Angeles Basin, Southern California: Implications for Rapid Uplift and Accumulation Rates.
Journal of Sedimentary Research A65: 656-667.
Historic Aerials
2025 Historic Aerial Viewer. https://www.historicaerials.com/viewer.
Ingersoll, R. V. and P. E. Rumelhart
1999 Three-stage Basin Evolution of the Los Angeles Basin, Southern California. Geology 27:
593-596.
SoilWeb
2025 National Resources Conservation Service Soil Survey Program website.
https://casoilresource.lawr.ucdavis.edu/gmap/.
Tan, S.S.
2000 Geologic Map of the El Monte 7.5-Minute Quadrangle, Los Angeles County, California.
California Division of Mines and Geology. Open-File Report OFR-98-29.
U.S. Geological Survey
2025 U.S. Quaternary Faults.
https://usgs.maps.arcgis.com/apps/webappviewer/index.html?id=5a6038b3a1684561a
9b0aadf88412fcf.
Yerkes, R.F., T.H. McCulloh, J.E. Schollhamer, and J.G. Vedder
1965 Geology of the Los Angeles Basin: An Introduction. Geological Survey Professional Paper
420-A.
September 2025
Kimley»Horn Page | 10
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
September 2025
Page | 11
Appendix A
Paleontological Record Search Results
City of Rosemead 1515 Walnut Grove Avenue Project
Paleontological Resources Assessment
Appendix A
Paleontological Record Search Results
September 2025
Kimley»Horn Page | 11
Research & Collections
e-mail: paleorecords@nhm.org
August 10, 2025
Kimley-Horn
Attn: Christina Livingston re: Paleontological resources records search for the 1515 Walnut Grove Project
Dear Christina:
I have conducted a search of our paleontology collection records for the proposed development at the 1515 Walnut Grove project area as outlined on the portion of the El Monte USGS topographic quadrangle map that you sent to me via e-mail on August 5, 2025. We do not have fossil localities that have been recorded or georeferenced directly within the proposed project area, but we do have fossil
localities nearby from similar sedimentary deposits that may occur in the proposed project area, either at the surface or at depth.
The following table shows the closest known localities in the collection of the Natural History
Museum of Los Angeles County (NHMLA).
Locality Number Location Formation Taxa Depth
LACM VP 3363
W of Monterey Pass Road in Coyote Pass; Monterey Park
Unknown formation (Pleistocene; sand and silt) Horse (Equus) Unknown
LACM VP
7702
Intersection of 26th St and Atlantic Blvd, Bell
Gardens
Unknown formation
(Pleistocene; silt)
Fish (Gasterosteus); snake (Colubridae), rodents (Thomomys, Microtus, Reithrodontomys); rabbit
(Sylvilagus)
30 feet
bgs
LACM IP 11852
Merced Hills to the north of Whittier Narrows Recreation Area
Pico Formation (conglomerate bed in siltstone)
Invertebrates, including tusk shell (Dentalum
neohexagonium) and foraminifera Unknown
LACM IP 2896 T2S; R12W. El Monte Quad Pico Formation Invertebrates (uncatalogued) Surface
VP, Vertebrate Paleontology; IP, Invertebrate Paleontology; bgs, below ground surface
This records search is limited to the records of the NHMLA. It is not intended as a paleontological assessment of the project for the purposes of California Environmental Quality Act (CEQA) or National Environmental Policy Act (NEPA). Potentially fossil-bearing units are
present in the project area, either at the surface or in the subsurface. As such, NHMLA
Natural History Museum
of Los Angeles County
900 Exposition Boulevard
Los Angeles, CA goooy
tel 213.763.DINO
NATURAL www.nhm.org
HISTORY
MUSEUM .
LOS ANGELES COUNTY Research & Collections
e-mail: paleorecords@nhm.org
August 10, 2025
Kimley-Horn
Attn: Christina Livingston
re: Paleontological resources records search for the 1515 Walnut Grove Project
Dear Christina:
I have conducted a search of our paleontology collection records for the proposed development at the
1515 Walnut Grove project area as outlined on the portion of the El Monte USGS topographic
quadrangle map that you sent to me via e-mail on August 5, 2025. We do not have fossil localities that
have been recorded or georeferenced directly within the proposed project area, but we do have fossil
localities nearby from similar sedimentary deposits that may occur in the proposed project area, either at
the surface or at depth.
The following table shows the closest known localities in the collection of the Natural History
Museum of Los Angeles County (NHMLA).
Locality
Number Location Formation Taxa Depth
W of Monterey Pass Unknown formation
LACM VP Road in Coyote Pass; (Pleistocene; sand
3363 Monterey Park and silt) Horse (Equus) Unknown
Fish (Gasterosteus); shake
(Colubridae), rodents
Intersection of 26th St (Thomomys, Microtus,
LACM VP and Atlantic Blvd, Bell Unknown formation Reithrodontomys); rabbit 30 feet
7702 Gardens (Pleistocene; silt) (Sylvilagus) bgs
Merced Hills to the Invertebrates, including tusk
north of Whittier Pico Formation shell (Dentalum
LACM IP Narrows Recreation (conglomerate bed neohexagonium) and
11852 Area in siltstone) foraminifera Unknown
T2S; R12W. El Monte
LACM IP 2896 Quad Pico Formation Invertebrates (uncatalogued) Surface
VP, Vertebrate Paleontology; IP, Invertebrate Paleontology; bgs, below ground surface
This records search is limited to the records of the NHMLA. It is not intended as a
paleontological assessment of the project for the purposes of California Environmental Quality
Act (CEQA) or National Environmental Policy Act (NEPA). Potentially fossil-bearing units are
present in the project area, either at the surface or in the subsurface. As such, NHMLA
recommends that a paleontological assessment be conducted by a paleontologist meeting Federal (43 Code of Federal Regulations Part 49.110) or Society of Vertebrate Paleontology standards
for compliance with applicable regulations, such as CEQA or NEPA.
Sincerely,
Alyssa Bell, Ph.D. Natural History Museum of Los Angeles County
recommends that a paleontological assessment be conducted by a paleontologist meeting Federal
(43 Code of Federal Regulations Part 49.110) or Society of Vertebrate Paleontology standards
for compliance with applicable regulations, such as CEQA or NEPA.
Sincerely,
(Ueqpaer Sep
Alyssa Bell, Ph.D.
Natural History Museum of Los Angeles County