Temporal Assessment of the Embodied Greenhouse Gas Emissions of a Toronto Streetcar Line

Makarchuk, Benjamin; Saxe, Shoshanna

doi:10.1061/(ASCE)IS.1943-555X.0000475

Open access

Technical Notes

Jan 31, 2019

Temporal Assessment of the Embodied Greenhouse Gas Emissions of a Toronto Streetcar Line

Authors: Benjamin Makarchuk and Shoshanna Saxe, Ph.D., M.ASCE [email protected]Author Affiliations

Publication: Journal of Infrastructure Systems

Volume 25, Issue 2

https://doi.org/10.1061/(ASCE)IS.1943-555X.0000475

PDF

Abstract

Transportation greenhouse gas (GHG) emissions often account for the largest share of urban GHG emissions. Consequently, large-scale reductions in urban GHG emissions will not be possible without significant improvements in the transport sector. Increasing public transit mode share is widely promoted in efforts to reduce GHG emissions from transport. Large increases in public transit use will require the provision of new transportation infrastructure, which is itself GHG intensive. This paper presents a time-dependent analysis of the embodied GHG emissions associated with construction and reconstruction for the refurbishment and street redesign of the 510 Spadina streetcar route in Toronto, Canada during a 38-year period. From 1987 to 2015, the embodied emissions in the line’s civil infrastructure are calculated as 27.4 kilotons of

{CO}_{2}

equivalent (

{ktCO}_{2} e

). It is expected that, by 2025, further reconstruction of the right-of-way (ROW) will increase embodied GHG emissions to

32.1 {ktCO}_{2} e

. Overall, reconstruction projects increase GHG emissions by 25.9% beyond initial construction. When accounting only for at-grade infrastructure, reconstruction increases embodied emissions by 45.8% during the 38-year study period.

Introduction

Urban areas are at the forefront of efforts to reduce greenhouse gas (GHG) emissions (Bansard et al. 2017; Watts 2017). An ongoing challenge is the need to reduce emissions associated with travel, which account for 27% of emissions worldwide (EPA 2017) and 41% of emissions in Toronto, Canada (City of Toronto 2016). The provision of public transit infrastructure provides an important opportunity to drive reductions in transport emissions by motivating changes in travel behavior and land use (Chester and Cano 2016). However, the construction of new infrastructure is itself associated with the production of GHG emissions through the use of materials (mainly concrete and steel) and the consumption of energy.

Recent studies have explored the life cycle environmental impacts of transit infrastructure (Chester and Cano 2016; Saxe et al. 2017). Other research has focused on the embodied GHG emissions in buildings (Gantner et al. 2018; Kaethner and Burridge 2012; De Wolf et al. 2016). However, only a limited body of work has focused on the embodied emissions associated with materials and fuel use in horizontal infrastructure and/or the impacts of reconstruction over the infrastructure’s lifetime.

This paper presents an ex-post, temporal analysis of the embodied GHG emissions produced during the construction and reconstruction of the 510 Spadina streetcar right of way (ROW) in Toronto. The results of this time-dependent analysis highlight how the embodied GHG emissions of the studied infrastructure increase over time given reconstruction. This finding has important implications when calculating GHG payback periods for transportation infrastructure and highlights how refurbishment and reconstruction continually increase embodied emissions. This research is useful for engineers, contractors, and policymakers working to reduce the overall GHG impact of the infrastructure and transport sectors.

Materials and energy consumption during the initial construction (1987), extension, and reconstruction of the Streetcar ROW are examined using construction records from 1987 to 2015. Further, projected reconstruction needs are estimated through 2025, at which point the entirety of the at-grade ROW will have been rebuilt.

This paper focuses exclusively on embodied GHG emissions from construction and major refurbishment or reconstruction activities. Operation and everyday maintenance are outside the scope of this research.

Research Context

Interest in the GHG impacts of infrastructure construction increased in the mid-2000s (Horvath 2004). Research by Chester and Horvath (2009) found that, for rail systems, accounting for infrastructure and vehicle construction increases the overall GHG impacts of travel by a factor of 1.8–2.5. However, to date, examination of the GHG impacts of transit infrastructure has been hampered by limited access to construction data and even more limited assessment of the refurbishment and reconstruction needs over the life of a rail line (Chester and Horvath 2010; Hanson et al. 2016; Saxe et al. 2017). Most work in the field has been time independent and provides limited differentiation between the years and causes of emissions (Chester and Horvath 2009, 2010; Hanson et al. 2016; Kimball et al. 2013; Li et al. 2016). A few recent studies have adopted a time-dependent approach (Chester and Cano 2016; Saxe et al. 2017), which provides valuable information on the temporal distribution of emissions. The impacts of infrastructure provision on overall GHG emissions remain underexplored.

To the knowledge of the authors, this paper presents the first ex-post, temporal examination of the GHG impacts of a rail transit line that considers ongoing reconstruction and refurbishment. This study addresses two important gaps in the literature by providing (1) a detailed assessment of rail construction emissions; and (2) a temporal examination of the impacts of reconstruction on embodied GHG emissions.

510 Spadina Streetcar

The 510 Spadina streetcar line operates on a dedicated ROW; it is 6.17-km long and is located in downtown Toronto (Toronto Transit Commission 2017a). The streetcar operates at-grade between Union and Spadina subway stations (Toronto Transit Commission 2017b). A portal connecting the at-grade track to an underground interchange platform is located at each end of the line. Fig. 1 indicates the route of the Spadina streetcar. The main construction and reconstruction activities examined in this paper are listed in Table 1. The city of Toronto expects that the tangent tracks on Spadina Ave. will need to be rebuilt before 2025 (Project Manager for the City of Toronto, personal communication, 2016). Based on the pace of past work observed in prior refurbishment projects, this project is assumed to occur over four years, beginning in 2022. No major reconstruction has been reported or predicted for the underground sections of the streetcar line.

Fig. 1. Construction and reconstruction projects along Spadina streetcar route (not to scale). (Adapted from City of Toronto Archives 1990.)

Table 1. Construction stages for Spadina streetcar

Stage	Dates	Construction activities
Stage 1 (City of Toronto Archives 1986)	1987–1990 (Howell 1990; Smith 1987)	• 2.2 km of at-grade ROW
		• 0.12 km long portal
		• Underground platforms
Stage 2 (City of Toronto Archives 1990)	1992–1997 (James 1992; Leckie 1997)	• Track-work and curbs along 2.4-km section of Spadina Ave.
		• Entrance portal and platform at Spadina subway station
		• Platforms along a 3.3-km section
Stage 1M (Waterfront Toronto and City of Toronto 2009)	2012–2014 (Waterfront Toronto and City of Toronto 2009)	• 1.3-km section of track was demolished and reconstructed
Stage 2M (City News Toronto 2014; Toronto Transit Commission 2012, 2013, 2015b)	2012–2015 (City News Toronto 2014; Toronto Transit Commission 2012, 2013, 2015b)	• Each of the four major unions (special tracks) along the route were rebuilt.
		• One union was reconstructed each summer.

Data Sources

A mix of data sources was used for this project, including construction drawings, specification standards, construction videos, and data from similar Toronto infrastructure projects. Material quantities are estimated from construction drawings sourced from predesign reports (City of Toronto Archives 1986), construction standards (City of Toronto 2001, 2014a), and environmental assessments (City of Toronto Archives 1990; Waterfront Toronto and City of Toronto 2009) from each of the line’s construction stages. A subset of drawings, including details from the Spadina Ave. and College St. intersection reconstruction (City of Toronto 2014b), was received from the city via email (Project Manager for the City of Toronto, personal communication, 2016, 2017). Waste rates were estimated using data from a similar project in Toronto—the St. Clair Avenue Streetcar (Project Manager for the City of Toronto, personal communication, 2016). Construction emissions were calculated from time-lapse footage of a 2015 intersection reconstruction (Toronto Transit Commission 2015a).

Material GHG emission factors were drawn from the following two sources: (1) the Canadian Athena Sustainable Materials Institute (ASMI) (Athena Sustainable Materials Institute 2017); and (2) the UK-based Inventory of Carbon and Energy (ICE), (Circular Ecology 2017). ASMI’s Canadian data were preferred. Emission factors for construction machinery were drawn from three sources that addressed (1) construction equipment undergoing normal operation cycles (Frey et al. 2010); (2) idling emissions (Lewis et al. 2012); and (3) heavy-duty on-road vehicles (Graham et al. 2008).

Methods

GHG emissions associated with the construction and reconstruction of the Spadina streetcar are estimated by examining (1) upstream emissions from material use; (2) onsite emissions from energy consumption in construction machinery; and (3) transport emissions produced when materials are brought to and removed from the site. GHG emissions are reported in kilotons of

{CO}_{2}

equivalents (

{ktCO}_{2} e

), calculated using the procedures outlined by the Intergovernmental Panel on Climate Change (2007) using 100-year global warming potentials.

Emissions from Construction Materials

Material emissions,

M

, are calculated by accounting for gross material consumption,

V

, and applying appropriate emission factors,

η

, to the results. Total material emissions for the

i

^th stage of construction (

M_{i}

) are calculated using Eq. (1), where

M_{i, j}

= emissions for a given material

j

during construction stage

i

.

The total material GHG emissions for a given stage of construction is as follows:

M_{i} = \sum_{j} M_{i, j} = \sum_{j} V_{i, j} η_{j}

(1)

GHG emissions of multiyear activities were equally apportioned across all years because of limited data availability.

Estimating Material Consumption in At-Grade Structures

At-grade structures were categorized into one of the following four categories: (1) track-work (tangent track); (2) curbs; (3) pedestrian platforms and platform finishings; and (4) union intersections (special track). Drawings and construction standards from different periods were used to capture design changes that have occurred since initial construction. Fig. 2 provides a 2014 drawing of the city of Toronto’s track-work design.

Fig. 2. 2014 design of streetcar track-work (not to scale). (Adapted from City of Toronto 2014a.)

Tables 2 and 3 highlight key features of straight and curved track-work, respectively. Platform specifications are presented in Table 4 and platform finishings are listed in Table 5. Material quantities for union intersections (at which the crossing of tracks makes material calculations involved) were calculated based on the geometry of the King St. and Spadina Ave. intersection, which was analyzed using satellite imagery (Google Earth 2017).

Table 2. Key features of straight track-work

Feature	Stage 1 (City of Toronto Archives 1986)	Stage 2 (City of Toronto 2001)	Stage 1M, 2M (City of Toronto 2014a)
Track type	Embedded	Embedded	Embedded
Track gauge (mm)	1,495	1,495	1,495
Rail section used	100 lb A.R.A-A	100 lb A.R.A-A (assumed same rail section used for Stage 2 constructions as stage 1 because no additional information was available)	115 lb A.R.E.A (City of Toronto 2008)
Foundation	Tangent track: 75-mm thick layer of HI-60 Styrofoam placed on top of subgrade; Special track: 600-mm thick layer of crushed limestone placed on top of subgrade	Compacted gravel foundation used in all track sections	Compacted gravel foundation used in all track sections
Track slab depth (mm)	610	625	680
Width of track-work (mm)	6,720	5,735	5,735
Tie specifications	Tracks mounted to foundation slab via direct-fixation system; no ties were used	Creosote impregnated hardwood ties used (cross section: $178 \times 266 mm$ ) spaced 610 mm apart (Project Manager for the City of Toronto, personal communication, 2017)	Steel I-beam ties— $W 150 \times 22$ (City of Toronto 2014b)

Note: If no source is listed for a given piece of information, assume that the default source for the construction stage in question was used, as listed in the heading.

Table 3. Key features of curved track-work

Stage	Standard curved track-section	Special track-sections (located in intersections only)
Stage 1	NP4aM girder railway is used only on one side of the tracks	NP4aM girder railway is used on both sides of the track. Creosote hardwood ties included at a spacing of 610 mm (same as Stage 2 constructions)
Stage 2	NP4aM girder railway is used only on one side of the tracks. Tie spacing unchanged compared with straight track-sections (original spacing is 610 mm, less than what is specified in the 2008 drawing; however, because generally curved sections require more support, the original spacing of 610 mm is preserved)	NP4aM girder railway is used on both sides of the track. Tie spacing unchanged compared with straight track-sections (original spacing is 610 mm, less than what is specified in the 2008 drawing; however, because generally curved sections require more support, the original spacing of 610 mm is preserved)
Stages 1M and 2M	NP4aM girder railway is used on only one side of the tracks. Tie spacing 914 mm	NP4aM girder railway is used on both sides of the track. Tie spacing 1,524 mm

Source: Data from City of Toronto (2008).

Table 4. Platform specifications

Feature	Narrow platform (City of Toronto Archives 1986)	Wide platform (City of Toronto Archives 1990)	Wide, ramped platform (City of Toronto Archives 1990)	New wide platform (Waterfront Toronto and City of Toronto 2009)
Stage	1	2	2	1M
Number of platforms constructed	8	16	8	6
Width (mm)	1,500	2,500	2,500	2,400
Length (mm)	30,000	30,000	30,000 (plus a 12,000-mm long access ramp)	30,000
Depth of concrete slab (mm)	830	830 (assumed to be the same as narrow platforms)	830 (average height of the ramp is 750 mm)	830 (assumed to be the same as narrow platforms)
Foundation specifications	75-mm thick HI-60 styrofoam foundation above the subgrade	150-mm thick gravel foundation (City of Toronto 2001)	150-mm thick gravel foundation (City of Toronto 2001)	150-mm thick gravel foundation (assumed to be the same as wide platforms)
Key platform finishings	Two steel splashboards 915-mm tall and 1,200-mm long	Three steel bus shelters 2,100-mm tall and 3,720-mm wide	Three steel bus shelters 2,100-mm tall and 3,720-mm wide	Three plastic bus shelters 2,200-mm tall and 4,500-mm wide
Key platform finishings	Two steel splashboards 915-mm tall and 1,200-mm long	Steel railing running the length of the platform	Steel railing running the length of the platform	Steel railing running the length of the platform

Note: If no source is listed for a given piece of information, assume that the default source, as listed in the heading, was used. Information on platform finishings was determined during two site visits to different platforms along the line (site visit, 2017-06-15, 2017-06-20).

Table 5. Specifications of platform finishings

Stage	Platform	Key platform finishings
Stage 1	Narrow platform (City of Toronto Archives 1986)	Two steel splashboards 915-mm tall and 1,200-mm long
Stage 2	Wide platform (site visit, 2017-06-15)	Three steel bus shelters 2,100-mm tall and 3,720-mm wide
Stage 2	Wide platform (site visit, 2017-06-15)	Steel railing running the length of the platform
Stage 2	Wide, ramped platform (site visit, 2017-06-15)	Three steel bus shelters 2,100-mm tall and 3,720-mm wide
Stage 2	Wide, ramped platform (site visit, 2017-06-15)	Steel railing running the length of the platform
Stage 1M	New wide platform (site visit, 2017-06-20)	Three plastic bus shelters 2,200-mm tall and 4,500-mm wide
Stage 1M	New wide platform (site visit, 2017-06-20)	Steel railing running the length of the platform

Estimating Material Consumption in Underground Structures

Although the majority of the Spadina streetcar route runs at-grade, underground structures were constructed at the line’s terminal stations. The Spadina streetcar’s underground structures include (1) tunnels; (2) two portals; (3) Queen’s Quay station; (4) Union station streetcar platform; and (5) Spadina station streetcar platform.

Structures with a constant cross section were analyzed using elevation drawings to calculate material consumption per unit length and plan drawings to estimate length (City of Toronto Archives 1986). Underground track-work is ballasted and connected to a 400-mm thick concrete slab via a direct fixation mechanism (City of Toronto Archives 1986). Fig. 3 illustrates one of the two tunnel cross sections. Limited information on the use of reinforcing bars was available. Thus, data drawn from the tunnel drawings (the only drawings for which reinforcing data were available) was scaled at a constant ratio. Material consumption at streetcar platforms in subway stations was measured using plan drawings of the platform from the Harbourfront LRT predesign report (City of Toronto Archives 1986). Cross sections of this station were unavailable. As such, wall, floor-slab, and roof-slab thicknesses were assumed to be the same as in Queen’s Quay station (City of Toronto Archives 1986). Nonload-bearing walls are assumed to be 200-mm thick.

Fig. 3. Combined two-car box structure (not to scale). (Reprinted from City of Toronto Archives 1986, with permission.)

Estimating Waste Generation

Waste rates are estimated based on Toronto Transit Commission (TTC) records for concrete use on the 512 St. Clair ROW, a project quite similar to Spadina. The applied waste generation rate is

0.024 m^{3} / m^{3}

.

Emission Factors for Material Emissions

Manufacturing processes of most construction materials are expected to have evolved since construction began on the Spadina streetcar ROW in 1987 with commiserate changes in the GHG intensity per unit of material. However, capturing this evolution was difficult because historical data were available only for concrete. For concrete, emission factors from 1993, 1999, and 2005 were available (Athena Sustainable Materials Institute 2005). These factors were assigned to Stages 1, 2, and 1M/2M constructions, respectively. A summary of the emission factors used for each material is provided in Table 6.

Table 6. Material emission factors

Material	Material emission factors, $η$ ( ${kgCO}_{2} e / m^{3}$ )
Material	Stage 1	Stage 2	Stages 1M and 2M
Concrete^a	284.5	280.7	282.9
Steel—track and ties^b	9,753.8	9,753.8	9,753.8
Steel—rebar^b	4,330.6	4,330.6	4,330.6
Steel—platform finishings^b	13,459.1	13,459.1	13,459.1
Wood^c	609.0	609.0	609.0
Granular A, track infill and crushed limestone^c	11.6	11.6	11.6
Loose fill—soil^c	35.0	35.0	35.0
HDPE^c	2,419.2	2,419.2	2,419.2
Polystyrene^c	113.4	113.4	113.4
Unshrinkable fill^c	125.1	125.1	125.1
General plastic^c	3,177.0	3,177.0	3,177.0

a

Athena Sustainable Materials Institute (2005).

b

Athena Sustainable Materials Institute (2002).

c

Hammond and Jones (2011).

Emissions from Construction Machinery and Transportation

Construction machinery and transportation (CMT) emissions were calculated in detail for the 2015 reconstruction of the College and Spadina intersection based on a time-lapse video of the construction available on YouTube (Toronto Transit Commission 2015a). The video covers 19 work days and indicates the reconstruction of the intersection from demolition to completion (Toronto Transit Commission 2015a).

The results from this analysis were then compared with the material emissions associated with the intersection to develop a CMT emissions factor

γ

, using Eq. (3). This factor was then applied across the project to calculate total CMT emissions. In the equation,

C_{i n t}

represents CMT emissions generated during the reconstruction of the intersection and

M_{i n t}

represents material emissions.

The proportion of total emissions from construction machinery and transportation is as follows:

\frac{(c_{i n t} + τ_{i n t})}{(c_{i n t} + τ_{i n t}) + M_{i n t}} = \frac{C_{i n t}}{C_{i n t} + M_{i n t}} = γ

(2)

For machine

m

, construction emissions (

c_{m}

) were calculated by estimating that machine’s operating time (

T_{m}

) and subsequently applying an appropriate emission factor (

ξ_{m}

), as shown in Eq. (3).

The construction emissions from a given machine are as follows:

c_{m} = ξ_{m} T_{m}

(3)

Transportation emissions,

τ

, were divided into two parts: idling emissions,

τ_{i d l e}

(produced when onsite) and driving emissions

τ_{d r i v e}

(produced when traveling). To quantify each of these emissions, daily idling time

T_{i d l e, m}

, the average distance traveled per trip

s

(km), and the number of trips taken per day

N_{t r i p s, m}

were estimated. Next, emission factors for idling machinery

ξ_{i d l e, m}

and for driving

ζ_{m}

(reported in

g {CO}_{2} e / km

) were applied, as shown in Eq. (4).

The transportation emissions from a given machine are as follows:

τ_{m} = τ_{i d l e, m} + τ_{d r i v e, m} = T_{i d l e, m} ξ_{i d l e, m} + s N_{t r i p s, m} ζ_{m}

(4)

Estimating Operating Times for Construction Machinery

Machinery emissions were calculated based on an assumption of either full day or one-third-day operations. Machines that were onsite and operational in more than 70% of the surveyed frames were assumed to have been operating for the entire workday. Otherwise, machines were assumed to have been operating for one-third of the workday. The classification was updated daily for the 19-day construction period.

Estimating Distance Traveled and Idling Times for Transportation Machinery

The construction video indicates four different transportation vehicles: (1) dump trucks; (2) refueling trucks; (3) concrete mixers; and (4) heavy-duty trucks used to transport rail (Toronto Transit Commission 2015a).

To calculate average distance traveled per trip for a given machine, two methods were used. If the point of origin of a transport machine was known, Google Maps was used to measure transport distance. Otherwise, nine possible origin sites throughout the greater Toronto area were surveyed, and the distances to the five closest possible points-of-origin were averaged. A dump truck capacity of 27 t was used (Hanson and Noland 2015; Schlegel et al. 2016) to estimate the number of trips required. This load was converted to volume assuming a density of 55%—the average density of loosely packed spheres (Song et al. 2008)—of the density of concrete.

Load volumes for concrete mixers were calculated at

4.82 m^{3}

based on the maximum safe capacity (63%) (National Ready Mixed Concrete Association 2017).

A total of 15 deliveries of steel rail were completed over three days of construction (Toronto Transit Commission 2015a). On days when the refueling truck was required, only one trip was made per day (Toronto Transit Commission 2015a).

The idling time of transportation vehicles was estimated to be 20 min because vehicles generally stay in the video for one or two frames, or 15–30 min (Toronto Transit Commission 2015a).

Emission Factors for Machinery Emissions

Table 7 lists the literature emission factors by machine type (Frey et al. 2010; Graham et al. 2008; Lewis et al. 2012).

Table 7. Emission factors for construction machinery

Machine	Activity	Source	Emission factor ( ${gCO}_{2} / h$ )
Excavators	Normal operation	Excavators (Frey et al. 2010)	24,327
Wheel loaders	Normal operation	Wheel loaders (Frey et al. 2010)	10,008
Skid steer loader	Normal operation	Skid steer loaders (Frey et al. 2010)	8,721
Heavy-duty truck, dump truck, refueling trucks, concrete mixers	Driving	Graham et al. (2008)	$1,632 g / km$
	Idling	Off-road truck (Lewis et al. 2012)	11,000
Paving machine	Normal operation	Excavators (Frey et al. 2010)	24,327
Cold planers	Normal operation	Off-road truck (Frey et al. 2010)	19,842
Mini-excavators	Normal operation	Skid-steer loader (Frey et al. 2010)	8,721
Compactors	Normal operation	Backhoes (Frey et al. 2010)	10,008
Portable crane; road sweeper; vans with boom lift	Normal operation	Off-road trucks (Frey et al. 2010)	19,842
Rail threader	Normal operation	Skid-steer loader (Frey et al. 2010)	8,721

Note: Emission factors for machines listed in bold were not reported in the literature.

For machine types for which the literature did not report specific values (Table 7), emission factors were developed based on construction machinery with similar engine qualities. Specifically, engine displacement and power—known to be highly correlated with GHG emission rates (Frey et al. 2010)—were considered. Rail threaders, for which limited available data exist, were assigned the emission factors from skid-steer loaders based on machine size. All machines were assumed to be powered only by diesel fuel.

The construction machinery emission factors in the referenced literature are reported in

{gCO}_{2} / h

, rather than

{gCO}_{2} e / h

. However, studies have found that

{CO}_{2}

represents 99% of all GHG emissions from these machines (Graham et al. 2008; Xing et al. 2016). Consequently, construction machinery emissions are reported in

{gCO}_{2} e / h

.

Key Exclusions

Effort was made to capture the full impacts of material and energy usage from both the construction and reconstruction of the Spadina streetcar; however, given data limitations, a number of factors was excluded. These factors include the GHG impacts of (1) the manufacturing of mechanical equipment, including the streetcars themselves; (2) embodied emissions in the catenary system used to power the streetcars; (3) material usage in transverse expansion joints; and (4) simultaneous road widening and utilities construction carried out in parallel to the streetcar construction. Further, construction energy was assessed for an at-grade section of the line, and the calculated factor was applied line wide. This likely underestimates the construction (energy use) emissions associated with underground structures, which are known to be larger than at-grade works (Nicholson et al. 2012) given additional construction processes (tunnel digging, disposal of extra soil, and shoring) required when building rail-tracks underground.

Results

Material Emissions

Fig. 4 indicates a temporal breakdown of material emissions between 1987 and 2015. Material emissions are highest, at

2,550 {tCO}_{2} e / y

, for Stage 1 works (initial construction). This finding is driven by the underground structures that account for 63.6% of material emissions generated during this stage.

Concrete was the highest emitter of GHG and was responsible for 74.6% of total material emissions. Material consumption from all stages released a total of

24.6 {ktCO}_{2} e

during a 28-year period. The “other” category includes a variety of materials, including plastics, aggregate, soils, and styrofoam.

The data in Fig. 4 include waste generation. Initial construction of the Spadina streetcar (Stages 1 and 2) is estimated to have generated

2,180 m^{3}

of waste, whereas reconstruction activities (Stages 1M and 2M) generated

304 m^{3}

. Together, these amounts account for 2.4% of overall material emissions.

Fig. 5 provides a breakdown of material emissions by component, taking into account emissions from all construction and reconstruction stages. Underground structures, including stations, tunnels, and portals, account for a disproportionate share of the Spadina streetcar’s material emissions.

Fig. 5. Material emissions by component.

Construction Machinery and Transportation Emissions

Fig. 6 provides a temporal representation of CMT emissions generated during the reconstruction of the Spadina and College intersection. In Fig. 6, GHG emissions are divided by machine type, and the primary construction activity for each day is listed to allow for a complete depiction of machine activity. Approximately half of CMT emissions (50.5%) were produced during the first three days of construction, which involved demolition, excavation, and material disposal. Excavators and concrete mixers were the primary emitters during this stage of the project, with cement trucks and other machines representing most of the emissions in the project’s later stages. Pouring the line’s new track-infill and foundation produced significant CMT emissions (30.1%). However, these emissions were spread out over seven days.

Fig. 6. CMT emissions from the College and Spadina intersection.

No heavy machinery was on site between days 9 and 11, when switches were installed by hand. Consequently, emission rates on both of those days were calculated as negligible.

Construction machinery and transportation produced a total of

24.7 {tCO}_{2} e

during the intersection rebuild. This amount represents 10.2% of total emissions from the intersection. By applying this factor to all constructions along the streetcar line, construction machinery was estimated to have produced

2,790 {tCO}_{2} e

to date.

Fig. 7 illustrates the proportion of total CMT emissions generated by each type of machine. Excavators (29%), concrete mixers (29%), and dump trucks (26%) were all important emitters. The “other” category in Fig. 7 represents a variety of machines, including—but not limited to—loaders, compactors, and asphalt pavers.

Fig. 7. Proportion of construction machinery emissions from different types of machines.

Overall, transportation and construction machinery contributed approximately equally to CMT emissions, representing 56.1% and 43.9%, respectively.

Overall Emissions and Future Projections

From 1987 to 2015, construction and reconstruction activities for the Spadina streetcar produced

27.4 {ktCO}_{2} e

. Of these emissions, 45.9% come from material consumption in the line’s underground structures, 43.9% come from at-grade structures, and 10.2% come from construction machinery.

The city of Toronto expects to refurbish the tangent track along Spadina Ave. by 2025. This additional reconstruction is expected to emit an additional

4.7 {ktCO}_{2} e

using the same emission factors as stage 1M reconstruction works, subsequently increasing the line’s total GHG emissions to

32.1 {ktCO}_{2} e

.

Fig. 8 presents a temporal breakdown of the Spadina streetcar’s overall emissions for the entire study period, including projected emissions to 2025.

Fig. 8. Total emissions from Spadina streetcar between 1987 and 2025.

Discussion

The Spadina streetcar ROW’s original construction (Stages 1 and 2) emitted

23.8 {ktCO}_{2} e

, equating to

3.86 {ktCO}_{2} e / km

. This finding is comparable with published results for the Exposition LRT in Los Angeles California, which found a GHG emission rate of

4.84 {ktCO}_{2} e / km

(Chester and Cano 2016).

This research again struggled with access to detailed construction records, which significantly facilitate embodied GHG assessment. For example, we were not able to find data on yearly energy and material use for ongoing maintenance. In general, the field would benefit from access to detailed material and energy use data for transport infrastructure.

Material emissions accounted for 89.8% of the line’s overall emissions. This amount agrees with the results of studies completed by Krantz et al. (2015) and Li et al. (2016), who found that, for infrastructure construction projects, materials accounted for 81.7% and 89.6% of overall emissions, respectively. As such, future efforts to reduce overall GHG emissions would particularly benefit from efforts to limit material use. However, care must be taken to avoid shifting GHG impacts from initial construction to refurbishment projects (e.g., by light-weighting initial construction at the detriment of durability).

CMT emissions were found to have accounted for approximately 10% of the total. Methods for reducing these types of emissions include: (1) reducing material transport distances; and (2) improved efficiencies from excavators, concrete mixers, and dump trucks.

A disproportionate amount of GHGs was emitted from the line’s underground sections, especially given that underground structures account for only 17% of the total track-length (City of Toronto Archives 1990, 1986; Toronto Transit Commission 2017a). This finding highlights the added complexity and material requirements involved in the construction of underground structures and the potential for reduced GHG emissions through at-grade construction when appropriate.

Reconstruction projects have accounted for an important part of overall emissions. Assuming that the Spadina streetcar’s straight track work is rebuilt as expected, emissions from reconstruction will have accounted for 25.5% of the line’s overall emissions by the year 2025, without allowing for any reconstruction on underground sections of the line. Accounting only for the at-grade sections, reconstruction is expected to nearly double the embodied GHG emissions of the streetcar line over a 38-year period.

The construction of public transit infrastructure is often associated with GHG emission savings given changes in travel behavior (Chester and Cano 2016; Saxe et al. 2017). Existing research has calculated a GHG payback period, which quantifies the time required to recuperate embodied GHG emissions through travel behavior and/or land use changes. However, most studies limit embodied GHG emissions to initial construction when calculating payback (Chester and Horvath 2010; Chester and Cano 2016; Saxe et al. 2017). If rail infrastructure must be entirely rebuilt within 40 years, the embodied GHG that must be “paid back” is significantly higher than has been calculated in past work. In addition to reducing embodied GHG emissions in initial construction, care must be taken to increase the durability of the structures to limit ongoing refurbishment.

Conclusion

This paper examines the GHG emissions associated with the construction and reconstruction of the Spadina streetcar ROW, starting in 1987. To date, emissions from construction and reconstruction activities total

27.4 {ktCO}_{2} e

, produced during a 28-year period. Future emissions from reconstruction projects are expected to contribute an additional

4.7 {ktCO}_{2} e

by 2025. Material consumption in underground structures accounts for a disproportionate amount of overall emissions (46.3%) despite accounting for only 17% of track length.

One of the key findings of this study was the relative significance of reconstruction. If projected projects are completed as planned, reconstruction will represent 25.5% of the line’s overall emissions by 2025. This amount represents a 45.8% increase in the embodied emissions of the at-grade sections of the ROW through reconstruction.

Policy makers, engineers, and constructors should use the results of this paper to advise the development of future infrastructure projects, specifically by emphasizing the dual importance of limited up front embodied emissions and ongoing durability. Additionally, this paper encourages researchers to consider reconstruction need when completing future life-cycle analyses of infrastructure because the proportion of emissions attributable to refurbishment needs is significant.

This paper contributes to the existing literature by adding (1) a new case study to the portfolio of examined embodied GHG in rail projects, (2) a temporal assessment of embodied GHG impacts, (3) a detailed assessment of construction machinery and transport emissions in at-grade rail construction, and (4) the addition of ongoing infrastructure reconstruction needs to our understanding of capital GHG emissions.

Notation

The following symbols are used in this paper:

$C_{i n t}$: CMT emissions generated during reconstruction of College and Spadina intersection;
$c_{i n t}$: construction emissions generated during reconstruction of College and Spadina intersection;
$c_{M}$: construction emissions generated by machine $m$ ;
$M$: material emissions;
$M_{i}$: material emissions for $i$ ^th stage of construction;
$M_{i, j}$: material emissions produced by material $j$ during $i$ ^th stage of construction;
$M_{i n t}$: material emissions generated in reconstruction of College and Spadina intersection;
$N_{trips, m}$: number of trips taken per day by machine $m$ ;
$s$: distance traveled by transport machine per trip (round-trip);
$T_{idle, m}$: idling time for machine $m$ ;
$T_{m}$: operating time for machine $m$ ;
$V$: gross material consumption;
$V_{i, j}$: material consumption for material $j$ during $i$ ^th stage of construction;
$γ$: proportion of total emissions generated by construction machinery or transportation;
$ζ$: emission factor for transportation machinery;
$ζ_{m}$: emission factor for transportation machine $m$ ;
$η$: emission factor for materials;
$η_{j}$: emission factor for material $j$ ;
$ξ$: emission factor for construction machinery;
$ξ_{idle, m}$: idling emission factor for machine $m$ ;
$ξ_{m}$: emission factor for machine $m$ ;
$τ$: transportation emissions;
$τ_{drive, m}$: transportation emissions for machine $m$ generated when driving;
$τ_{idle, m}$: transportation emissions for machine $m$ generated when idling; and
$τ_{i n t}$: transportation emissions generated during reconstruction of College and Spadina intersection.

References

Athena Sustainable Materials Institute. 2002. Cradle-to-gate life cycle inventory: Canadian and US steel production by mill type. Ottawa: Athena Sustainable Materials Institute.

Google Scholar

Athena Sustainable Materials Institute. 2005. Cement and structural concrete products: Life cycle inventory update #2. Ottawa: Athena Sustainable Materials Institute.

Google Scholar

Athena Sustainable Materials Institute. 2017. “About ASMI.” Accessed July 23, 2017. http://www.athenasmi.org/about-asmi/overview/.

Google Scholar

Bansard, J. S., P. H. Pattberg, and O. Widerberg. 2017. “Cities to the rescue? Assessing the performance of transnational municipal networks in global climate governance.” Int. Environ. Agreements: Politics Law Econ. 17 (2): 229–246. https://doi.org/10.1007/s10784-016-9318-9.

Google Scholar

Chester, M., and A. Horvath. 2010. “Life-cycle assessment of high-speed rail: The case of California.” Environ. Res. Lett. 5 (1): 014003. https://doi.org/10.1088/1748-9326/5/1/014003.

Google Scholar

Chester, M. V., and A. Cano. 2016. “Time-based life-cycle assessment for environmental policymaking: Greenhouse gas reduction goals and public transit.” Transp. Res. Part D: Transp. Environ. 43 (Mar): 49–58. https://doi.org/10.1016/j.trd.2015.12.003.

Google Scholar

Chester, M. V., and A. Horvath. 2009. “Environmental assessment of passenger transportation should include infrastructure and supply chains.” Environ. Res. Lett. 4 (2): 024008. https://doi.org/10.1088/1748-9326/4/2/024008.

Google Scholar

Circular Ecology. 2017. “Embodied energy and carbon: The ICE database.” Accessed July 23, 2017. http://www.circularecology.com/embodied-energy-and-carbon-footprint-database.html#.WXT5tsYZNE4.

Google Scholar

City News Toronto. 2014. “Dundas-Spadina intersection closed for 4 weeks for construction.” Accessed June 8, 2017. http://www.citynews.ca/2014/07/14/dundas-spadina-intersection-to-close-for-4-weeks-for-construction/.

Google Scholar

City of Toronto. 2001. Streetcar track allowance cross-section: Dwg. T-216.02-10. Toronto: City of Toronto.

Google Scholar

City of Toronto. 2008. Plan views of resiliently embedded street track (for construction after 2007): Dwg. W8T-870. Toronto: City of Toronto.

Google Scholar

City of Toronto. 2014a. Streetcar track allowance cross-section: Dwg. T-216.02-10. Toronto: City of Toronto.

Google Scholar

City of Toronto. 2014b. Spadina Avenue at College Street: Dwg. P-4426-036. Toronto: City of Toronto.

Google Scholar

City of Toronto. 2016. Toronto’s 2013 greenhouse gas inventory, 1–14. Toronto: City of Toronto.

Google Scholar

City of Toronto Archives. 1986. Fonds 2, Series 1143, Item 267 Harboufront L.R.T: Predesign report-1986. Toronto: City of Toronto Archives.

Google Scholar

City of Toronto Archives. 1990. Fonds 2, Series 1143, Item 259 Spadina LRT environmental assessment: 1990. Toronto: City of Toronto Archives.

Google Scholar

De Wolf, C., F. Yang, D. Cox, A. Charlson, A. S. Hattan, and J. Ochsendorf. 2016. “Material quantities and embodied carbon dioxide in structures.” Proc. Inst. Civ. Eng.: Eng. Sustainability 169 (4): 150–161. https://doi.org/10.1680/ensu.15.00033.

Google Scholar

EPA. 2017. “Sources of greenhouse gas emissions.” Accessed August 22, 2017. https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions.

Google Scholar

Frey, H. C., W. Rasdorf, and P. Lewis. 2010. “Comprehensive field study of fuel use and emissions of nonroad diesel construction equipment.” Transp. Res. Rec. 2158 (1): 69–76. https://doi.org/10.3141/2158-09.

Google Scholar

Gantner, J., W., Fawcett, and I., Ellingham. 2018. “Probabilistic approaches to the measurement of embodied carbon in buildings.” In Embodied carbon in buildings, 23–50. Cham, Switzerland: Springer.

Crossref

Google Scholar

Google Earth. 2017. “King St. and Spadina Ave. intersection.” Accessed July 15, 2017. https://earth.google.com/web/@43.64549397,-79.39500252,87.53178513a,92.63163996d,35y,-0h,0t,0r.

Google Scholar

Graham, L. A., G. Rideout, D. Rosenblatt, and J. Hendren. 2008. “Greenhouse gas emissions from heavy-duty vehicles.” Atmos. Environ. 42 (19): 4665–4681. https://doi.org/10.1016/j.atmosenv.2008.01.049.

Google Scholar

Hammond, G., and C., Jones. 2011. Inventory of carbon and energy (ICE) version 2.0. Bath, UK: Univ. of Bath.

Google Scholar

Hanson, C. S., and R. B. Noland. 2015. “Greenhouse gas emissions from road construction: An assessment of alternative staging approaches.” Transp. Res. Part D: Transp. Environ. 40 (Oct): 97–103. https://doi.org/10.1016/j.trd.2015.08.002.

Google Scholar

Hanson, C. S., R. B. Noland, and C. D. Porter. 2016. “Greenhouse gas emissions associated with materials used in commuter rail lines.” Int. J. Sustainable Transp. 10 (5): 475–484. https://doi.org/10.1080/15568318.2014.985859.

Google Scholar

Horvath, A. 2004. “Construction materials and the environment.” Ann. Rev. Environ. Resour. 29 (1): 181–204. https://doi.org/10.1146/annurev.energy.29.062403.102215.

Google Scholar

Howell, P. 1990. “Waterfront streetcar gets rolling: Free rides offered on Red Rocket all this weekend.” Toronto Star, June 23, 1990.

Google Scholar

Intergovernmental Panel on Climate Change. 2007. Climate change 2007: The physical science basis, edited by S. Solomon, D. Qin, M. Manning, M. Marquis, K. Averyt, M. Tignor, H. Miller Jr., and Z. Chen. Cambridge, UK: Cambridge University Press.

Crossref

Google Scholar

James, R. 1992. “Spadina transit line wins approval.” Toronto Star, May 2, 1992.

Google Scholar

Kaethner, S. C., and J. A. Burridge. 2012. “Embodied

{CO}_{2}

of structural frames.” Struct. Eng. 90 (5): 33–40.

Google Scholar

Kimball, M., M. Chester, C. Gino, and J. Reyna. 2013. “Assessing the potential for reducing life-cycle environmental impacts through transit-oriented development infill along existing light rail in phoenix.” J. Plann. Educ. Res. 33 (4): 395–410. https://doi.org/10.1177/0739456X13507485.

Google Scholar

Krantz, J., J. Larsson, W. Lu, and T. Olofsson. 2015. “Assessing embodied energy and greenhouse gas emissions in infrastructure projects.” Buildings 5 (4): 1156–1170. https://doi.org/10.3390/buildings5041156.

Google Scholar

Leckie, J. 1997. “Spadina streetcar line ready to open this month.” Daily Commercial News and Construction Record, Toronto, July 22, 1997.

Google Scholar

Lewis, P., M. Leming, and W. Rasdorf. 2012. “Impact of engine idling on fuel use and emissions of nonroad diesel construction equipment.” J. Manage. Eng. 28 (1): 31–38. https://doi.org/10.1061/(ASCE)ME.1943-5479.0000068.

Google Scholar

Li, Y., Q. He, X. Luo, Y. Zhang, and L. Dong. 2016. “Calculation of life-cycle greenhouse gas emissions of urban rail transit systems: A case study of Shanghai Metro.” Resour. Conserv. Recycl. 128 (Jan): 451–457. https://doi.org/10.1016/j.resconrec.2016.03.007.

Google Scholar

National Ready Mixed Concrete Association. 2017. “Delivery of ready mixed concrete.” Accessed August 22, 2017. https://www.nrmca.org/aboutconcrete/howdelivered.asp.

Google Scholar

Nicholson, D., K. Soga, C. Chau, and N. O’Riordan. 2012. “Embodied energy evaluation for sections of the UK Channel Tunnel rail link.” Proc. ICE Geotech. Eng. 165 (2): 65–81. https://doi.org/10.1680/geng.9.00018.

Google Scholar

Saxe, S., E. Miller, and P. Guthrie. 2017. “The net greenhouse gas impact of the Sheppard Subway Line.” Transp. Res. Part D: Transp. Environ. 51 (Mar): 261–275. https://doi.org/10.1016/j.trd.2017.01.007.

Google Scholar

Schlegel, T., D. Puiatti, H.-J. Ritter, D. Lesueur, C. Denayer, and A. Shtiza. 2016. “The limits of partial life cycle assessment studies in road construction practices: A case study on the use of hydrated lime in Hot Mix Asphalt.” Transp. Res. Part D: Transp. Environ. 48 (Oct): 141–160. https://doi.org/10.1016/j.trd.2016.08.005.

Google Scholar

Smith, M. 1987. “$24 million harbor line contract signed.” Toronto Star, September 18, 1987.

Google Scholar

Song, C., P. Wang, and H. A. Makse. 2008. “A phase diagram for jammed matter.” Nature 453 (7195): 629–632. https://doi.org/10.1038/nature06981.

Google Scholar

Toronto Transit Commission. 2012. “TTC diversions due to track work July 9–23.” Accessed July 17, 2017. https://www.ttc.ca/News/2012/July/0706_queen_divert.jsp.

Google Scholar

Toronto Transit Commission. 2013. “Spadina-King intersection to close for TTC track work.” Accessed July 17, 2017. https://www.ttc.ca/News/2013/August/0801_king_spadina.jsp.

Google Scholar

Toronto Transit Commission. 2015a. “Rebuilding College-Spadina in just over 2 minutes.” Accessed August 8, 2017. https://www.youtube.com/watch?v=kPJuU8CaKAc.

Google Scholar

Toronto Transit Commission. 2015b. “TTC to conduct track work at Spadina-College intersection.” Accessed July 17, 2017. https://www.ttc.ca/News/2015/March/0325_college_spadina.jsp.

Google Scholar

Toronto Transit Commission. 2017a. “Service summary; May 7, 2017–June 17, 2017.” Accessed August 2, 2017. https://www.ttc.ca/PDF/Transit_Planning/Service.

Google Scholar

Toronto Transit Commission. 2017b. “510 Spadina.” Accessed August 15, 2017. http://www.ttc.ca/Routes/510/RouteDescription.jsp?tabName=route.

Google Scholar

Waterfront Toronto and City of Toronto. 2009. Queens quay revitalization environmental assessment. Toronto: City of Toronto.

Google Scholar

Watts, M. 2017. “Cities spearhead climate action.” Nat. Clim. Change 7 (8): 537–538. https://doi.org/10.1038/nclimate3358.

Google Scholar

Xing, Y., H. Song, M. Yu, C. Wang, Y. Zhou, G. Liu, and L. Du. 2016. “The characteristics of greenhouse gas emissions from heavy-duty trucks in the Beijing-Tianjin-Hebei (BTH) region in China.” Atmosphere 7 (9): 121. https://doi.org/10.3390/atmos7090121.

Google Scholar

Information & Authors

Information

Published In

Journal of Infrastructure Systems

Volume 25 • Issue 2 • June 2019

Copyright

This work is made available under the terms of the Creative Commons Attribution 4.0 International license, http://creativecommons.org/licenses/by/4.0/.

History

Received: Jan 29, 2018

Accepted: Sep 10, 2018

Published online: Jan 31, 2019

Published in print: Jun 1, 2019

Discussion open until: Jun 30, 2019

Authors

Affiliations

Benjamin Makarchuk

Undergraduate Candidate, Dept. of Civil Engineering, Univ. of Toronto, 35 St. George St., Toronto, ON, Canada M5S 1A4.

View all articles by this author

Shoshanna Saxe, Ph.D., M.ASCE [email protected]

P.Eng.

Assistant Professor, Dept. of Civil Engineering, Univ. of Toronto, 35 St. George St., Toronto, ON, Canada M5S 1A4 (corresponding author). Email: [email protected]

View all articles by this author

Metrics & Citations

Metrics

Citations

Download citation

If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.

Abstract

Introduction

Research Context

510 Spadina Streetcar

Data Sources

Methods

Emissions from Construction Materials

Estimating Material Consumption in At-Grade Structures

Estimating Material Consumption in Underground Structures

Estimating Waste Generation

Emission Factors for Material Emissions

Emissions from Construction Machinery and Transportation

Estimating Operating Times for Construction Machinery

Estimating Distance Traveled and Idling Times for Transportation Machinery

Emission Factors for Machinery Emissions

Key Exclusions

Results

Material Emissions

Construction Machinery and Transportation Emissions

Overall Emissions and Future Projections

Discussion

Conclusion

Notation

References

Information

Published In

Copyright

History

Authors

Affiliations

Metrics

Citations

Download citation

Cited by

Figures

Other

Share

Copy the content Link

Share with email

Share

Request Username

Create a new account

Change Password

Password Changed Successfully

Verify Phone

Congrats!