1
25-083
Spider Excavator Pilot Study for Removal Action Planning at
Abandoned Uranium Mine Sites
Jennifer Laggan
Freeport-McMoRan, Houston, TX
Key Rosebrook
Jacobs, New York, NY
Ashley Rivera
Jacobs, Houston, TX
ABSTRACT
Significant quantities of waste rock at abandoned uranium
mine (AUM) sites in the western United States require
removal from steep slopes exceeding 45 degrees in remote
locations. This prevents the use of traditional excavation
equipment and poses significant challenges for safe, effec-
tive material removal.
A pilot study was conducted using a spider excava-
tor to demonstrate the feasibility of removing waste rock
and transporting it to areas where conventional equipment
could be employed. The spider excavator was evaluated for
its effectiveness in excavation, material movement and con-
trol, container usage, dust mitigation, and ensuring human
health and environmental safety.
The study established constructability and engineer-
ing parameters for implementing spider excavators in these
challenging environments. Key outcomes include the pres-
ervation of existing vegetation, improved waste movement
control, and enhanced safety measures for workers, nearby
residents, and the environment.
INTRODUCTION
The AUM sites are characterized by challenging topogra-
phy, including steep mountains, mesas, and dry arroyos.
Many of these areas require the removal of materials con-
taminated with radionuclides and metals, often from loca-
tions inaccessible to conventional excavation equipment.
Typical AUM sites are located in rugged and remote loca-
tions and have steep cliffs and dense vegetation, which
limit accessibility for traditional excavation approaches (see
example in Figure 1).
Spider excavators are considered a potential solution
for removing waste from steep or inaccessible areas because
of their specialized ability to navigate challenging terrain
with slopes up to 60 degrees. The excavators can use a
winch cable system to anchor themselves securely, allow-
ing for safer operation in extreme conditions. To evaluate
the feasibility of using spider excavators for these tasks,
Freeport-McMoRan and Jacobs conducted a pilot study in
2024 at the Mt. Emmons Mining Company Site (MEMC
Site) in Crested Butte, Colorado. The size of waste rock,
type of vegetation, slope, and elevation at AUM sites are
similar to the MEMC Site to simulate operating condi-
tions. However, the MEMC Site does not have a history of
uranium mining or uranium contamination.
The objectives of the pilot study were to evaluate the
effectiveness of the spider excavator in accessing remote
sites, setting anchors, excavating waste rock, and identi-
fying health and safety issues. Lessons learned from this
pilot study provide essential data for future removal action
designs if traditional excavation equipment cannot be used.
PILOT SUMMARY
The following subsections summarize the pilot study objec-
tive, tasks, and results.
Determine Effectiveness of Excavator to Access
Remote Sites
The first objective was to determine the effectiveness of the
enclosed-cab Kaiser Spider Walking Excavator S2-4WD
in mobilizing across narrow, steep switchbacks to reach
remote work areas. The pilot involved mobilizing from a
25-083
Spider Excavator Pilot Study for Removal Action Planning at
Abandoned Uranium Mine Sites
Jennifer Laggan
Freeport-McMoRan, Houston, TX
Key Rosebrook
Jacobs, New York, NY
Ashley Rivera
Jacobs, Houston, TX
ABSTRACT
Significant quantities of waste rock at abandoned uranium
mine (AUM) sites in the western United States require
removal from steep slopes exceeding 45 degrees in remote
locations. This prevents the use of traditional excavation
equipment and poses significant challenges for safe, effec-
tive material removal.
A pilot study was conducted using a spider excava-
tor to demonstrate the feasibility of removing waste rock
and transporting it to areas where conventional equipment
could be employed. The spider excavator was evaluated for
its effectiveness in excavation, material movement and con-
trol, container usage, dust mitigation, and ensuring human
health and environmental safety.
The study established constructability and engineer-
ing parameters for implementing spider excavators in these
challenging environments. Key outcomes include the pres-
ervation of existing vegetation, improved waste movement
control, and enhanced safety measures for workers, nearby
residents, and the environment.
INTRODUCTION
The AUM sites are characterized by challenging topogra-
phy, including steep mountains, mesas, and dry arroyos.
Many of these areas require the removal of materials con-
taminated with radionuclides and metals, often from loca-
tions inaccessible to conventional excavation equipment.
Typical AUM sites are located in rugged and remote loca-
tions and have steep cliffs and dense vegetation, which
limit accessibility for traditional excavation approaches (see
example in Figure 1).
Spider excavators are considered a potential solution
for removing waste from steep or inaccessible areas because
of their specialized ability to navigate challenging terrain
with slopes up to 60 degrees. The excavators can use a
winch cable system to anchor themselves securely, allow-
ing for safer operation in extreme conditions. To evaluate
the feasibility of using spider excavators for these tasks,
Freeport-McMoRan and Jacobs conducted a pilot study in
2024 at the Mt. Emmons Mining Company Site (MEMC
Site) in Crested Butte, Colorado. The size of waste rock,
type of vegetation, slope, and elevation at AUM sites are
similar to the MEMC Site to simulate operating condi-
tions. However, the MEMC Site does not have a history of
uranium mining or uranium contamination.
The objectives of the pilot study were to evaluate the
effectiveness of the spider excavator in accessing remote
sites, setting anchors, excavating waste rock, and identi-
fying health and safety issues. Lessons learned from this
pilot study provide essential data for future removal action
designs if traditional excavation equipment cannot be used.
PILOT SUMMARY
The following subsections summarize the pilot study objec-
tive, tasks, and results.
Determine Effectiveness of Excavator to Access
Remote Sites
The first objective was to determine the effectiveness of the
enclosed-cab Kaiser Spider Walking Excavator S2-4WD
in mobilizing across narrow, steep switchbacks to reach
remote work areas. The pilot involved mobilizing from a