Construction Emissions: Using Project Data to Improve Regional Inventories

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Construction Emissions Using Project Data to
Improve Regional Inventories
Douglas Eisinger, Ph.D. Deb Niemeier, Ph.D.,
P.E. UC Davis-Caltrans Air Quality
Project Presented at the 86th Annual Meeting of
the Transportation Research Board, Workshop
135 Guidelines on Conducting Project Level Air
Quality Analysis Washington, D.C. January 21,
2007
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Outline

• Motivation Need Local Activity Data
• Setting the Context Example Project
• Top-Down Regional Emissions
• Bottom-up Regional Emissions
• Number and type of construction projects per year
• Equipment and use per project
• Emissions
• Sacramento Example Bottom-up Inventory
• Comparison Top-Down vs. Bottom-up
• Some Observations
• Conclusions

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1. Motivation Need Local Activity Data
Powerpoint From Caltrans Training Exercise
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2. Setting the Context Example Project

• 1.7 mile long I-80 auxiliary lane addition in
  Sacramento
• 6 month project, four construction stages
• Land clearing
• Roadway grading and excavation
• Drainage/utilities/sub-grade
• Paving

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Sacramento ProjectYear 2008 NOx Emissions

• Analysis inputs
• Total disturbed project area 8 acres
• Soil moved 300 yd3 per day (imports and
  exports)
• Model-Assigned Equipment by phase

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Sacramento ProjectYear 2008 NOx Emissions

• Modeled with Sacramento area air district tool
• Total project NOx emissions 3.5 tons
• But emissions would be about 10-15 less with
  solar sign boards (instead of diesel-powered
  sign boards)

Lets look at building a regional inventory
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3. Sacramento NOx Emissions Top-Down

• Diesel-powered construction is 8 of annual
  average NOx emissions (2008)

• Basis regional equipment populations, activity,
  and OFFROAD emission factors
• Note transportation construction is not
  separated

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Top Down Estimating Transportation Construction
NOx

• Need to disaggregate total construction emissions
• Possible approaches
• Road construction PM emissions are 58 of all
  construction and demolition PM emissions
• ARB construction equipment population surveys
• SIC Group 161 (highway / street construction) is
  12
• SIC Group 162 (includes bridge, tunnel, elevated
  highway) is 38
• SIC 161 162 equal 50 of all construction
  equipment
• Possible range 12-58 of all construction
  transportation construction

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4. Bottom Up Regional Emissions

• Data needs
• Equipment and use per project
• Number of construction projects
• Emission factors

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Equipment and Use Per Project (1 of
2)California Statewide Data

• UCD created data set of Caltrans projects for
  years 2000-2005
• Established six major construction categories

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Equipment and Use Per Project (2 of 2)

• Collected daily reports (diaries) for 30 projects
• Built data set of equipment activity by project

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Year 2008 NOx Emissions for Average Project
EFs gms/equip piece/hr (from OFFROAD2007)
Wide range by project type 0.3 10.7 tons
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5. Sacramento Example Bottom-Up Inventory a.
Number of Projects

• Caltrans data 57 Caltrans projects / year
• SACOG data 63 other transportation projects /
  year
• Total 120 projects per year

Source average of 2004-2006 project data from
Caltrans and SACOG.
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5. Sacramento Example Bottom-Up Inventory b.
2008 Regional NOx Emissions Estimate
289 NOx tons/yr
X

Ave. project 2.7 tons NOx
120 projects/yr
1.1 NOx tons/day

Ave. project 253 days
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Sacramento Example Caveats

• Lots of assumptions!
• Caltrans data set is representative
• Other Caltrans projects are similar to top six
  categories
• SACOG projects are similar to Caltrans projects
• Average project represents typical project mix
  for a given year

Main point illustrate concept, give sense of
scale to emissions
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6. Comparison Top-Down vs. Bottom-Up
Sacramento 2008 NOx Emissions

• Top-Down (OFFROAD2007)
• All NOx 238 tpd
• All construction 19 tpd
• IF THEN
• 58 trans. 11 tpd (PM )
• 50 trans. 9.5 tpd (SIC 161 162)
• 12 trans. 2.3 tpd (SIC 161 only)
• Bottom-Up
• 1.1 tpd trans.

In this illustration, top-down emissions are 2-10
X higher than bottom-up
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7. Some Observations

• Activity varies by project type in Caltrans data
• Project duration 181 394 days
• Total project NOx emissions 0.3 10.7 tons
• Caveat data set needs to be expanded to better
  represent individual project types

Main point estimating project emissions
requires activity data specific to project type
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Some Observations Off-Road Modeling Not as
Mature as On-Road Modeling

• Nov. 2006 California ARB releases OFFROAD2007
• 8 less equipment than prior model
• Construction equipment useful life doubled from
  prior model

Example year 2000 equipment populations
(statewide)
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8. Conclusions

• Activity assumptions are central to emissions
  estimates
• Inventory tools are still in early development
  stages
• Bottom-up can quality-check top-down
  inventories
• Sacramento illustration includes lots of
  assumptions but results imply
• Lots of uncertainty in regional inventories
• Need to disaggregate sources to quality-check
  findings
• Need better project and regional activity data
  (spatial, temporal, fleet mix)

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Acknowledgments

• The study team thanks the following individuals
  for their assistance
• Song Bai, U.C. Davis
• Mike Brady, Caltrans
• José Luis Cáceres, SACOG
• Zhen Dai, California Air Resources Board/UCD
• Gordon Garry, SACOG
• Justin Kable, Port of Oakland/UCD
• Robert OLoughlin, Federal Highway Administration
• Jeff Pulverman, Caltrans
• Sharon Tang, Caltrans
• Ru Wang, U.C. Davis

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For Q A

• Top Five NOx Emitters by Construction Equipment
  Type
• OFFROAD2007 Caltrans Data
• Rollers v
• Graders v
• Scrapers v
• Excavators v
• Generator Set v
• Crawler Tractors v
• Skid Steer Loaders v
• Rubber Tire Loaders v v
• Tractors/Loaders/Backhoes v

Main point construction activity in model does
not characterize road construction per se