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46 This section is organized into 26 highway construction categories (see Table 1 in Chapter 3). Each construction category has a summary page followed by a more detailed description of each of the SCPs, adding up to a total of 77 SCPs (see Table 4 in Chapter 3). Each SCP has a summary of the practice followed by key references that describe the SCP in detail, offering case studies, presenting supporting research, or otherwise providing insight into the practice. 8.1 How to Read a Highway Construction Category Page C H A P T E R 8 How to Read Chapter 9 Title of the Construction Category Overview of what the category is and general sustainability practices Of the 10 sustainability and 26 construction categories, highlights those related to this category. The summarized category is italicized. Unrelated categories are greyed out. Helps to cross-reference other SCPs. Best resources to consult for SCP guidance, assistance and tools in this category Of the 3 possible motivations for SCPs, which apply in this category (see Section 8.3 ) Brief listing of SCPs addressed in this category Principal Guidance, Assistance, and Tools Nazarian, S., M. Mazari, I. N. Abdallah, et al. 2015. Modulus-Based Construction Specification for Compaction of Earthwork and Unbound Aggregate. Transportation Research Board of the National Academies, Washington, D.C. TRB. n.d. Transportation Earthworks: Information Resource Center. http://www.trb.org/AFS10/AFS10.aspx.
How to Read Chapter 9 47 8.2 How to Read a Sustainable Construction Practice Page Title of the SCP SCP ratings (see Section 99.4) Summary of the SCP Key references that describe the SCP in more detail, provide examples or otherwise give more information Key References AASHTO and NSBA. 2016. G12.1-2016: Guidelines to Design for Constructability. Collaboration of AASHTO and National Steel Bridge Association. AASHTO. 2000. Constructability Review Best Practices Guide. AASHTO Subcommittee on Construction. NCHRP Project 10-99, Framework for Implementing Constructability across the Entire Project Development Process: NEPA to Final Design, is ongoing at the time of this publication. 8.3 Motivations Described Each highway construction category summary page contains a box that identifies the primary motivations a contractor would have for doing the SCPs in that category. These are: ⢠Business opportunity. These SCPs offer the contractor the opportunity to increase revenue and/or market share, reduce expenses, increase employee productivity, and/or reduce risks. ⢠Project requirement. These SCPs likely cost the contractor more to accomplish than the benefits they provide. Therefore contractors could be expected to accomplish these SCPs only if required to by the contract and properly compensated. This happens most often when the expense of accomplishing an SCP is assigned to the contractor, but the benefits of the SCP accrue to the owner or public. ⢠Goodwill. These SCPs might be accomplished by the contractor for the greater good of society regardless of contractor expense. 8.4 SCP Ratings Described Each SCP has been rated by a panel of experts for the effort necessary to do it, and the sustain- ability impacts it can have. Based on how they were done, ratings essentially represent an average of the expert panelâs perception of each SCP within the context of their own professional experi- ence. These ratings provide value by (1) quantifying expert industry perception of each SCP and (2) stimulating debate and thought about each SCPâs contribution to sustainability within the context of a particular project. Rating panel composition. Ratings were done by 22 individuals who were either (1) panel members for this NCHRP project, (2) industry experts invited to a workshop conducted for this NCHRP project, or (3) the team that did the work for this NCHRP project. Ratings process. Raters completed an online survey containing all SCPs. Raters were given instructions and asked to rate each SCP they felt qualified to rate. Raters could skip any SCP or rating that they did not feel qualified to address. Efforts and impacts of most SCPs are context sensi- tive. Therefore, one raterâs perception of the efforts and impacts of an SCP may not match anotherâs.
48 Sustainable Highway Construction Guidebook Rating topics. Each rating on the left (see Section 9.2) is an average of expert ratings in the following topic areas: 1. Effort. This is a combined rating that represents the cost and time it takes to do or implement the SCP. 2. Human welfare. This is the impact the SCP has on human health and well-being. This rating measures how much the SCP directly benefits people in terms of basic needs (food, water, sanitation), health and happiness (health, safety, culture, aesthetics), and personal/social development (education, equality, good governance). 3. Environmental benefit. This is the impact the SCP has on the environment. This rating measures how much the SCP contributes to maintaining clean air, water, and land; preserving natural resources (ecological resources, water resources, and reduced consumption of these resources); and conserving climate/energy (use of renewable energy, reduced use of fossil fuel, and reduced GHG emissions). 4. Cost savings. This is the immediate and long-term cost savings from the SCP. The cost of an SCP is captured in the effort topic; the savings is captured here. Rating values. Each rating is done on a scale of 0 to 5 with the following rough meaning: 0 = no meaningful impact in this category, 1 = impact is less than 1% of the total impact in this category for the project, 2 = impact is 1% to 5% of the total impact in this category for the project, 3 = impact is 5% to 10% of the total impact in this category for the project, 4 = impact is 10% to 15% of the total impact in this category for the project, and 5 = impact is over 15% of the total impact in this category for the project. Impact/effort ratio. A measure of return on an effort invested for the SCP. Calculated as the sum of impacts from human welfare, environmental benefit, and cost savings, divided by effort. Higher ratios indicate higher returns on investment but do not necessarily mean greater absolute impact. All ratings are relative. Effort and impacts for most SCPs vary based on project context. For instance, balanced earthwork may have a large impact on an earthwork-intensive project but may have little impact on a pavement overlay. It is nearly impossible to rate an SCP for all possible contexts. Therefore, experts rated SCPs based on their own personal experience and knowledge, which varies between experts. How to use the ratings. Ratings represent a general perception of the SCP, which may or may not coincide with reality for a given context. Use these ratings as a quick guide to their effort and impacts but be comfortable with overriding them for a given projectâs context. For example, semi-permanent high-mast lighting is listed at an effort of 2.5. But a particular project may have geometric constraints and neighborhood concerns that might make this kind of lighting more appropriate and can be considered at an effort of 4 or 5. Ratings Disclaimer Rating perceptions may not be generalizable to broad industry perceptions. Ratings by a select group of industry professionals may not be representative of the industry as a whole. This is true of any randomly or non-randomly selected sample population. Raters were selected based on their expertise in (continued on next page)
How to Read Chapter 9 49 highway construction and their knowledge of sustainability as it is defined in this guidebook; both are essential to produce ratings consistent with the ideas presented in this guidebook. Raters were not selected based on their ability to replicate industry perception. There is no absolute truth in sustainability ratings. Sustainability is context sensitive (see Section 2.1.4) and multi-faceted (see Section 3.1.2)âtraits which effectively prohibit a universal metric based on physically measurable parameters. Therefore, sustainability ratings and accounting standards necessarily involve subjectivity. Ratings Disclaimer (Continued)
