An international LCA conference is held every two to three years that focuses on sustainable transport infrastructure, in particular pavement and hardscape. The most recent of these conferences was held in Champaign, Illinois in 2017 . This symposium was a continuation of earlier conferences and workshops beginning with the Pavement LCA workshop held in Davis, California in 2010 ; the RILEM Symposium on LCA for Construction Materials held in Nantes, France in 2012 ; and the Pavement LCA Symposium held in Davis, California in 2014 . These conferences act as a platform to bring together international construction material industries, contractors, consultants, researchers, academia and the transport administrations . One of the major aims of these conferences is to implement life cycle thinking for transport infrastructures and promulgating the use of quantitative environmental assessment methods that help in decision support, such as the LCA. The most recent conference focused on data collection, inventory development, and data quality. Data essential for the UM-LCA approach is rapidly being improved through the work of various collaborators in industry and government, many of whom come together semi-annually through the Federal Highway Administration Sustainable Pavement Task Group . A framework has been developed for pavement LCA which can easily be extended to all urban hardscapes . Data availability for urban hardscape materials is becoming more widely available through several efforts being organized by consortia of government, industry and academia, such as the Federal LCA Commons ,vertical tower planter and the other efforts .Climate change is a pressing problem that cities will have to deal with and adapt to, but they have often not started making changes in infrastructure engineering and management.
Reasons for this delay include short term priorities driving design and planning, and inefficient use or omission of climate change data in infrastructure planning processes . A group of academics and transportation practitioners who are involved in the Infrastructure and Climate network in the northeastern region of the United States has addressed the systematic incorporation of climate change in infrastructure engineering and has worked to connect climate experts to front-line transportation infrastructure managers and designers. This approach provides a model for further improvement of communication between climate change modelers and infrastructure managers, particularly with regard to converting climate change predictions into actionable data for engineers. Permeable pavement is one approach to using hardscape for the multiple functions of transportation, storm water quality management, groundwater recharge and flood control, but it has been used in a small fraction of the potential places where it might provide multifunctional benefits. In early 2017, the University of California Pavement Research Center and the National Center for Sustainable Transportation , working with the Interlocking Concrete Pavement Institute , identified gaps in knowledge and other barriers to wider implementation that were perceived to be holding back the full potential for deployment of pavements that can simultaneously solve transportation, storm water quality, and flood control problems. A workshop was organized in November 2017 based on those discussions with the goal of identifying knowledge, information, and communication barriers to adoption of permeable pavement of all types, and creation of a road map to address and overcome them. The workshop brought together a diverse group of stakeholders from the planning, storm water quality, flood control, and pavement communities to listen to presentations, exchange and discuss unanswered questions identified by the group, and then to discuss a proposed road map to fill the gaps in knowledge, processes, and guidance. Some of the major findings in the final report from the workshop regarding the institutional and informational obstacles to making use of permeable pavement more acceptable to designers echo the principles identified by Chester et al. for improving the resiliency of flood control infrastructure.
These include recognition of the benefits of designing decentralized, autonomous infrastructure systems, such as making major portions of urban paved areas permeable instead of, or in addition to, building centralized storm water conveyance and storage systems; and, encouraging communication and collaboration that transcend disciplinary barriers rather than involving multiple, but distinct disciplinary perspectives. In this case, difficulties in identifying roles and relationships between urban transportation departments, storm water regulatory agencies, and flood control agencies in determining responsibility for maintaining the multi-functionality of permeable pavements emerged as an obstacle. Technical issues were also identified by the workshop, as well as the need for better cost and performance data. A presentation at a workshop by Haselbach discussed how the risk of flood damage increases in downstream cities built along rivers in long flood plains, such as those along rivers in Texas, when upstream cities expand their urban hardscape and flood conveyance to rapidly shed water. Thus, there is increased risk of flooding in each city as the area covered by hardscape increases, and that risk cascades and is multiplied significantly for downstream cities as upstream systems release water to protect the integrity of their own infrastructure and local urban areas. In addition to the review of the published literature, meetings were held with researchers at UC Los Angeles , UC Davis and the University of Southern California to review the concept for the UM-LCA framework presented in this white paper and potential data sources. The consulted experts included Stephanie Pincetl and Eric Fournier at UCLA, Jay Lund and Jon Herman at UCD and George Ban-Weiss at USC. As an example of data collection, Pincetl and Fournier pointed to the LCA framework and tool called City Road Network LCA developed for the roadway system in Los Angeles and used by Fraser and Chester and other studies. The data tracks the location of streets and highways over time and was developed in a GIS environment.
To complement this source of information for hardscape, potential data sources for soil permeability information were identified to assess where permeable hardscape could successfully be used to infiltrate water into the soil versus areas where permeable hardscape can only store water for later discharge. The SSURGO and STATSGO spatial data layers from the National Resources Conservation Service of the U.S.Information from the Permeable Pavement Road Map Workshop indicated that the scale of these maps is not sufficiently fine to capture the permeability for project design purposes, but should still provide adequate data on the scale of urban metabolism studies. Pincetl and Fournier pointed to use of fly-over maps to identify hardscape paved areas that can augment the estimates of surface areas of highways, streets and roads available from state and local government sources. Data regarding material flows can be obtained down to a sub-urban area level from the IMPLAN database and tool. They indicated that data regarding building ages can be obtained from the California Economic Development Division by business data centers. This is the data approach used by Reyna and Chester to also indicate the rate of demolition of buildings. The rate of demolition of publicly owned roads and streets would have to be estimated from maintenance and rehabilitation data from local and state government sources, inferred for private sources, and compared with estimates of civil infrastructure demolition hauling ton-miles.An UM-LCA framework was developed that can quantify water and hardscape material metabolism for a defined area/boundary as shown in Figure 7. It is based on the literature survey and discussions with experts in water management systems,lettuce vertical farming storm water runoff quality, freight systems and materials across number of institutions and agencies. For initial use in California, Caltrans adjusted urban area boundaries derived from the 2010 census and approved by FHWA are being considered as the system boundaries for the framework. The framework consists of horizontal and vertical flows. Horizontal flows are hardscape material flows which include asphalt products, concrete products, aggregates, crushed concrete demolition materials from building and other structures, additives, admixtures and recyclable materials. The vertical flow is the hydrologic cycle which is considered in the framework. The goal for development and use of the framework is to reduce environmental impacts of urban hardscape through analysis and rethinking of hardscape management, including design, construction, maintenance, rehabilitation and end-of-life to produce and compare alternatives to current practices. In addition to the typical environmental impact-indicators in the FHWA pavement LCA framework , it is proposed that later development should consider inclusion of the social LCA indicators developed in a separate recent report . Initial indicators have been developed for thermal comfort, focused on outdoor or pavement related thermal comfort rather than inside-building comfort, aural comfort and glare comfort . Only some of these references look at development of life cycle impact indicators; most are focused on comfort indices that could serve as mid-point indicators rather than indicators of effects on human health over the life cycle and considering all stages of the life cycle. Effects of pavement on the overall urban heat island for the entire urban area and the resultant impacts on thermal comfort, summertime cooling, wintertime heating and energy use from heating and cooling can also be considered.
Consideration of overall urban heat island effects requires climate modeling, and consideration of the energy sources for heating and cooling. A recent study in California found that the energy and greenhouse gas emission impacts of changing pavement surfaces to increase albedo and decrease urban area heat island were primarily dependent on the changes in pavement materials, and the effects of resultant changes in building energy use were much smaller. This result will change depending on the climate region and sources of electrical energy for air conditioning and building heating.There is no single source for data for hardscape material flows. Some of the common data sources include databases, LCA literature, public documents, surveys, etc. A comprehensive list of data sources for different materials were compiled in previous research conducted for development of an LCA framework for aviation pavements as well as the FHWA pavement LCA framework report as shown in Table 1, and which can be translated for use in the UMLCA framework. In LCA, the terms foreground and background data are often used to differentiate between data that defines or represent the study application and the datasets used to describe the background systems on which they rely datasets derived from databases. Table 1 include references to both background and foreground data sources, but mostly background data sources.For California, the UCPRC has previously developed LCI datasets for construction materials tailored to California conditions, which are particularly suitable for projects in California. UCPRC updated LCA models with new inventories, processes, and models recently to expand the capacities of LCA for improving the sustainability of pavement operations in California . The updates included new inventories for pavement materials such as asphalt, concrete, terminal blend rubberized asphalt concrete, warm-mix asphalt, open-graded friction courses, pre-cast concrete slabs, reinforced concrete, aggregate bases, cement treated bases, asphalt treated bases, maintenance treatments such as chip seals, slurry seals, and reflective coatings, and the different types of full- and partial-depth recycling strategies that are typically used by Caltrans. Furthermore, the UCPRC LCIs have been critically reviewed by three LCA experts for data assumptions, collection, processes and quality. These LCIs and impact calculations are included in a new LCA tool called eLCAP . Similar activities could be undertaken at any state or city level to generate geographically appropriate LCAs and eLCAP or other similar tools could include updated regionally adjusted inventories for locations outside California. Quantification of flows of materials that are transported in and out of the urban boundary are needed to be able to apply the unit process data. The Commodity Flow Survey is conducted under the partnership of the Bureau of Transportation Statistics and the U.S. Census Bureau every few years. CFS data covers movement of forty-three goods that are transported in and out of the boundaries of the U.S. and U.S. cities by road transport. The Freight Analysis Framework Data Tabulation Tool is another data source that can be used to collect data for a specific city or region in the U.S. that can then be used in the UM-LCA framework. The FAF4 tool is divided into four flow types; total flows, domestic flows, import flows and export flows. Total flows include domestic and foreign shipments between domestic origins and destinations whereas domestic flows do not include foreign trade flows. Import and export flows includes goods movement between domestic and foreign origins.