dredge fleet scheduling optimization and sensitivity analysis kenneth ned mitchell, phd erdc coastal...
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![Page 1: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/1.jpg)
Dredge Fleet Scheduling Optimization and Sensitivity Analysis
Kenneth Ned Mitchell, PhDERDC Coastal and Hydraulics Laboratory
Dr. Heather L. NachtmannUniversity of Arkansas Dept. of Industrial Engineering
Mack-Blackwell Rural Transportation Center
![Page 2: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/2.jpg)
USACE Dredging Program• Hundreds of projects dredged
every year to maintain navigable depths.
• Costs increasing, even though cumulative dredged volumes are not.
At least $X in Avg. annual O&M
funding
# of Navigati
on projects
$10M 34
$1M 190
$100k 448
$10k 669
$1k 797
Source: Dredging Information System, USACE Institute for Water Resources
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Dredge Fleet Scheduling• USACE dredging jobs are
contracted at the District level.
• Industry and Corps-owned dredges are selected based on cost, availability, and ability to execute project dredging requirements.
• Dredging at any one project must be completed during local environmental windows.
![Page 4: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/4.jpg)
Dredge Fleet Scheduling• Thousands of project-level
environmental restrictions for dozens of species, applied incrementally through the decades; easy to implement, hard to undo.
• Cumulative effect of these scheduling constraints has contributed to significant overall increases in USACE dredging mission execution costs.
• Costs of these environments restrictions cannot be quantified without considering the system-level interdependencies across projects.
http://www.theresilientfamily.com/wp-content/uploads/2012/01/ratchet-effect.png
http://coryandjennifer.net/corymorse/blog/wp-content/uploads/2011/01/GR0102TRAFFIC-LIGHTS-011.jpg
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Fleet Scheduling Optimization
• Constrained resource scheduling problem• Daily scheduling over a one year planning
horizon• Objective function
– Minimize total number of active dredge days (dredge time + travel time) to dredge all projects
• Model Constraints– Each project assigned to a single dredge– Dredge can only be assigned to one project at a time– Dredge may not work on a project during any
applicable restricted period
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Fleet Scheduling Optimization
• Optimal nationwide assignment and scheduling of dredges to navigation projects is interesting, perhaps even helpful…
• BUT, it is sensitivity analysis that will help answer persistent, long-standing questions concerning:– Critical environmental windows for targeted
R&D– Next-generation dredge fleet characteristics– Sequencing of projects with multi-year
dredging cycles
![Page 7: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/7.jpg)
Initial Fleet Scheduling Model• Dredging Information System (DIS) used to
parameterize dredges and project dredging requirements: http://www.ndc.iwr.usace.army.mil/data/datadrgsel.htm– Each dredge given a daily production rate (CY/day)– Each project given an average annual dredging
requirement (CY)
• USACE Threatened, Endangered, and Sensitive Species Protection and Management System used to establish project-level scheduling constraints: http://el.erdc.usace.army.mil/tessp/
![Page 8: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/8.jpg)
Fleet Scheduling Sample Problem• 32 dredge jobs of varying cubic yardage
requirements located throughout the U.S.; distance matrix for travel times
• 10 dredges with varying daily production rates• 4 restricted period scenarios evaluated for initial
sensitivity analysis to show proof of concept:– Baseline restricted periods (from TESSPMS)– 10% across-the-board restricted period
relaxation– 15% relaxation– 25% relaxation
Goal is to demonstrate that relaxation of environmental restrictions can lead to significant, quantifiable, system-level efficiency gains for USACE dredging program.
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Baseline scenario results
![Page 10: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/10.jpg)
10% relaxation results
![Page 11: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/11.jpg)
25% relaxation results
![Page 12: Dredge Fleet Scheduling Optimization and Sensitivity Analysis Kenneth Ned Mitchell, PhD ERDC Coastal and Hydraulics Laboratory Dr. Heather L. Nachtmann](https://reader036.vdocuments.net/reader036/viewer/2022062423/5697bfef1a28abf838cba2aa/html5/thumbnails/12.jpg)
Sensitivity Analysis Results• Simplified preliminary
model nonetheless captures system-level efficiency gains.
• Model output can be analyzed to pinpoint specific restrictions with largest impact on overall dredging costs.
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Next Steps• Increase model size and sharpen
parameter values to be more reflective of real-world conditions
• Include dredge-type specific environmental restrictions, as well as stochastic aspects (ie temperature thresholds).
• Incorporate dredging contract cost analysis (Linkov, et al., 2012) so that number of available dredges directly relates to dredging costs in model.
1 2 3 4 5 6 7
-40.00%
-30.00%
-20.00%
-10.00%
0.00%
10.00%
20.00%
Number of Bidders
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Dredge Fleet Scheduling Optimization and Sensitivity Analysis
Questions?
Kenneth Ned Mitchell, Ph.D.U.S. Army Corps of Engineers – Research and Development Center
Coastal and Hydraulics LaboratoryDredging Innovations Group (DIG) Deputy Director