Corporate Responsibility Report 2023

We’re embracing challenges to make lasting contributions and forge the best path forward for our firm, our people and the planet.

Corporate Responsibility Report

There is no one path to solving complex problems. But there is a best path, forged through curiosity, innovative thinking and the relentless pursuit of new possibilities.

When projects – and the world they’re born into – become more complex, how do you choose the best path? We believe the journey starts with strong partnerships. When technical excellence, creativity and innovation merge with true collaboration, there’s no problem we can’t solve together.

We have the power to make a difference –and a responsibility to improve the world.

OVERVIEW Introduction

We have the power to make a difference – and a responsibility to improve the world.

This report is our annual communication of the firm’s corporate responsibility targets and of progress toward our ESG (environmental, social and governance) goals.

We’ve been publishing it, sharing our data for the purpose of maintaining transparency and accountability, for more than 10 years . In 2023, we launched a Climate Action initiative aimed at deepening our decarbonization and resilience solutions to help clients take holistic approaches to mitigating and adapting to climate change.

We hired our first ED&I Officer, entering a new stage in our equity, diversity and inclusion efforts. And we moved closer to achieving our corporate responsibility targets, took on new commitments and embraced challenges to make lasting contributions.

CORPORATE RESPONSIBILITY AT A GLANCE

OVERVIEW Executive Message

In solving complex problems for our clients, we have always merged analytical and creative thinking. We combine the logical processes of theory, math and science with art, ingenuity and imagination.

These qualities, together with strong collaboration, are ever more essential in a world of interconnected problems, competing priorities and expanding frontiers.

Climate change is a major driver of increased complexity in our work. We have been challenged to reduce the impact of our projects on the environment and make them more resilient in a warming world. What we call “climate action” has become a central task of project teams. Embodied and operational carbon are now embedded into design thinking, with interoperable parametric modeling and artificial intelligence helping us assess the carbon impact of alternative materials, processes and supply chains. We continue to push innovative systems, such as mass timber, literally to new heights. In all our partnerships, we strive to make a positive impact – reducing our carbon footprint while increasing our carbon handprint.

Climate action extends beyond physical building systems. Our support of circular economic principles means minimizing the impact of new construction and intelligently reusing existing structures to reduce cost, time and carbon impact. Our efforts to enhance resilience and sustainability extend to the energy supply itself, which is undergoing a rapid transformation to renewable, low-carbon sources, creating opportunities to reposition legacy energy infrastructure.

We are passionate about building better communities, and not just through the impact of our projects. A better Thornton Tomasetti community springs from people pursuing their passions –from mentoring the next generation to expanding our culture of inclusive leadership and belonging.

Navigating all this complexity requires a holistic view, which can be found only through collaboration with project partners. There is no one path to solving complex problems. But there is a best path, forged through curiosity, innovative thinking and the relentless pursuit of new possibilities.

Michael Squarzini Co-Chief Executive Officer New York

Peter DiMaggio Co-Chief Executive Officer New York

Thornton Tomasetti

OVERVIEW

Our Corporate Responsibility Approach

Our big goal is to be the global driver of change and innovation in our industry, and our purpose is to embrace challenges to make lasting contributions.

These principles inform our corporate responsibility approach, along with our core values:

• We are passionate about what we do.

• We see opportunity where others focus on risk.

• We look beyond the obvious to solve the real problem.

• We challenge people to grow.

As a technical consulting firm, Thornton Tomasetti works with clients to apply science, engineering, design, planning, investigation and analysis to help shape the future and improve the world. Our diverse skill set enables us to collaborate effectively – both internally among our integrated practices and externally with all types of service providers in a range of industries.

Our approach to sustainability management is built on the three Ps of the triple bottom line, reflecting what we have long recognized: that responsible firms operate and grow in ways that are socially accountable (“people”), environmentally friendly (“planet”) and financially sustainable (“profit”). We aspire to be one of the most sustainable firms in the AEC world, both in the way we design our projects and in how we operate as a responsible business. We recognize that with our wide-ranging expertise in the building and energy sectors, we can have a significant carbon “handprint,” or net-positive impact, and that we have a responsibility to address the challenges of climate change.

Strategy

In 2012, we founded a Corporate Responsibility department, led by a corporate responsibility officer who reports to a co-CEO and is guided by a steering committee that is representative of our diverse practices and offices. And although the department was originally established to meet the reporting requirements of the American Institute of Architects’ 2030 Commitment for carbon-neutral buildings, corporate responsibility now spans all our departments and disciplines. Many individuals, including a total of 70+ green champions distributed among our offices, contribute to progress toward meeting our corporate responsibility goals.

To manage the firm’s positive and negative impacts on the economy, the environment and people, every five years the Corporate Responsibility department works with our executive team and our Corporate Responsibility Steering Committee to update our short-, medium- and long-term strategies and reexamine our goals and measurable targets for achieving this vision ( see Our Goals & Targets ). We share our progress toward these goals in our annual corporate responsibility report.

By driving innovation and embracing challenges – seeing opportunity where others may focus on risk – we’ll ensure our firm’s own sustainable development and contribute to more sustainable industries. And in accordance with our core ideology, we’ll bolster our long-term growth and reduce business risks by making meaningful investments in people and the planet, recognizing that these investments drive innovation and lead to greater long-term value. Our approach will influence our clients and suppliers as we continue to build relationships with trusted partners who share our commitment.

Corporate Climate Action, the internal-facing arm of our Climate Action initiative, impels us to lead by example, augment our expertise and collaborate with others in the industry to effect change.

Thornton Tomasetti

OVERVIEW What Was New in 2023?

Milestones in Our Journey

• Established Corporate Responsibility department

• Initiated green champions program

• Conducted first emissions inventory

What Was New in 2023?

• Began publishing annual sustainability report

• Established green office certification policy

• Set goal of carbon neutrality by 2030

• Offset all air-travel emissions annually

• Joined the Carbon Leadership Forum

Climate change is one of the biggest challenges facing our society. And because it affects everyone, it demands our creativity, passion and collaboration to build a better, more enduring world. In 2023, we launched our Climate Action initiative which unites our engineers, scientists, architects and sustainability professionals – and leverages our understanding of decarbonization and resilience practices – in our efforts to mitigate and adapt to the effects of climate change.

Within our Climate Action initiative is our corporate climate action what we do internally that is built on our corporate responsibility approach and bolsters our external project work. It includes aiming to achieve carbon-neutral business operations in our 40+ offices around the world, providing sustainability education to staff and clients, and moving the industry forward by advocating for innovative carbon-reduction policies and practices.

• Joined U.S. EPA Green Power Partnership

• Offices began purchasing green power at the local level

• Adopted the Architecture 2030 Challenge

• Reported our progress as member of the AIA 2030 Commitment

• Established environmental policy

• Began our Embodied Carbon Community of Practice

We help clients think holistically about proactive and reactive steps to address climate change. Under the climate-action umbrella, our decarbonization work focuses on reducing the greenhouse gas emissions associated with energy supply and demand. Our resilience work supports adaptive buildings, resilient communities, and planning and policy.

We also invest in the success of our people throughout their careers to build a firm where people from diverse backgrounds want to come, grow and achieve their career goals. This year, we took an important step in our Equity, Diversity and Inclusion initiative by hiring our first ED&I officer, Vandana Juneja. Vandana collaborates on corporate responsibility initiatives and promotes our ED&I program. With a stronger ED&I team, we’re tracking and accelerating progress toward our goal of becoming a place where all our people can bring their authentic selves to work.

• Conceived our Climate Action initiative, deepening our commitment to sustainable operations, decarbonization and resilience services

• Partnered with Climate Group on ConcreteZero

• First year reporting (for 2022) in reference to Global Reporting Initiative

• Finalized climateaction plan

• Purchased 100% green power for all U.S. offices

• Planned for 2024 commitment to the Science Based Targets initiative

Our corporate climate-action timeline shows milestones on our path to carbon neutrality.

Thornton Tomasetti

OVERVIEW

EQUITY, DIVERSITY & INCLUSION

Our Materiality Topics

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In 2022, we conducted a materiality assessment that identified topics for ESG (environment, social and governance) measurement and reporting. This assessment built on our prior years of sustainability reporting and our corporate responsibility strategic planning.

We examined these questions: What is the impact to our business, and what is important to our stakeholders? Our stakeholders include our employees and potential hires; owners, clients and partners; potential clients and partners; our suppliers; and our communities.

We approached our materiality assessment with the following assumptions:

• After almost a decade of corporate responsibility reporting, we had come to a consensus on the social and environmental topics important to our business. A materiality assessment would help uncover impact areas we had not yet explored.

• We could learn about what was important to our stakeholders by researching the material topics that rose to the top for clients and partners within our sector.

• Thornton Tomasetti is a private service company in a nonmanufacturing and nonextractive industry. Therefore, topics that are significant to large public companies may not be immediately significant to our firm.

We started the process by outlining the Global Reporting Initiative (GRI) material topics and the legacy topics we had been measuring and chronicling through our annual sustainability reports. Since no GRI sector standard exists for engineering, we didn’t include any sector standard topics. Then we reviewed the GRI reports of client and partner firms in our industry and identified the material topics they value.

CARBONNEUTRAL OPERATIONS

PROFESSIONAL DEVELOPMENT

EMBODIEDCARBON REDUCTION PROJECTS WITH POSITIVE SOCIAL OUTCOMES

HEALTHY WORKPLACE

COMMUNITY SERVICE

CORPORATE RESPONSIBILITY

Five-Year Goals 2020-2024

After acquiring this information, we held dialogue sessions with our department leaders, executive committee and corporate responsibility steering committee. Co-CEO Peter DiMaggio approved the final list of significant topics for reporting.

Three tiers of material topics emerged from these sessions:

• Tier 1 topics are of highest materiality to Thornton Tomasetti and are recounted in this 2023 corporate responsibility report.

• Tier 2 topics are of importance to our stakeholders and to the engineering sector (for example, occupational health and safety) but currently are not outstanding risk factors or major impact areas for our firm. We may consider including some or all of these topics in future reporting.

• Tier 3 topics do not apply to our business model or sector (for example, freedom of association).

Our Tier 1 topics include economic performance, energy, emissions, employment, training and education, diversity and equal opportunity, and nondiscrimination. In addition to these topics listed by GRI, we include our company-specific legacy topics of community service and employee wellness.

When evaluating the impacts of these material areas, we considered both short- and long-term impacts and any areas of grievances. We recognize that our Tier 2 topics may not be immediately important, yet they could become more material to our business and sector in the long term. In selecting material topics, we considered that Thornton Tomasetti often provides a service to a multidisciplinary design team as a subcontractor to another firm and therefore may not have direct influence on suppliers to our projects.

Every five years, we establish goals, along with supporting targets, based on our materiality topics.

Thornton Tomasetti

Our Materiality Topics

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OVERVIEW Our Goals & Targets

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Our corporate responsibility goals guide our CR approach, help define our materiality topics and provide a gauge by which we measure our progress. How successful have we been in meeting the short- and long-term targets we’ve set for attaining these goals?

Demonstrate Positive Environmental & Social Impact Across All Practices

Surpassed 40% Target: We reduced CO 2 e from sustainability projects by about 1.5 times that of our 2020 baseline.

Surpassed 15+ Target: 19 communities increased resilience in 2023 with our assistance.

Surpassed 20% Target: 52% of our R&D supports environmental and social outcomes.

Making Progress on 50%: While we saw no increase in projects aimed specifically at achieving net-zero energy, projects with other energy reduction goals have continued to grow.

Making Progress on 25%: We’re setting a baseline against which we can measure progress toward our target of 25% reduction in embodied carbon in structural frames and continue to annually report to the Structural Engineers 2050 Commitment (SE 2050) on embodied carbon in our projects.

Achieve Carbon-Neutral Business Operations by 2030

Surpassed 4.2% Target: We reduced Scope 2 emissions between 2022 and 2023 by 43%.

Making Progress on 2.0 MT: We came close to achieving our target. We achieved a 2.34 MT CO 2 e per-person carbon footprint in 2022, and came closer in 2023, with a per-person carbon footprint of 2.05 MT CO 2 e.

Making Progress on 5%: Our absolute operational emissions between 2022 and 2023 fell by 3.5%. In 2024, several offices will move to more energy-efficient spaces per our office fit-out policy, which should lead to greater emissions reductions.

Making Progress on 2.5%: We did not reduce our Scope 3 emissions between 2022 and 2023. In 2024, we will align our reductions with the SBTi program and focus our efforts on Scope 3 emissions.

OVERVIEW Our Goals & Targets

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Promote an Inclusive & Diverse Community

Surpassed 75% Target: 87% of employees surveyed state that they are involved in one or more ED&I activities.

Met 75% Target: Over 70% of employees surveyed report that they are impacted positively by our Equity, Diversity & Inclusion initiative.

Met 100% Target: 100% of employees surveyed indicate that they are familiar with our ED&I initiative.

Met 2x Target: Since 2019, we’ve seen a 200% rise in the number of women shareholders and shares held by women.

Making Progress on 5+: In 2023, we had three employee network groups ( Women@TT, Mosaic and Spectrum ). While we might add more ENGs in the future, our current focus is on developing a strategic direction for the ED&I program following the hire of our first ED&I officer.

Support a Healthy Workplace & Accelerate Development

Surpassed 80% Target: 96% of employees surveyed say they’re satisfied with workplace flexibility.

Surpassed 60% Target: A recent survey indicated that 73% of employees engaged in at least one wellness program activity.

Surpassed 80% Target: 85% of employees surveyed state that they’re satisfied with company benefits.

Making Progress on 70%: 58% of employees are engaged in knowledge-sharing initiatives, such as our communities of practice Membership will grow as we add communities focused on new topics.

Met 100% Goal: 100% of employees have the opportunity to participate in our mentorship program.

Support Our Employees' Passion for Community Service

Surpassed 10% Target: Between 2022 and 2023, service hours documented on time sheets grew by 55%.

Making Progress on 100%: 64% of employees surveyed felt they had unfettered access to community service opportunities. Lack of time during the workday and not being aware of the benefit are the most common reasons given for not participating. We’re increasing the number of employees engaged in community service by bringing more awareness to volunteer opportunities and surveying employees to understand the challenges.

Making Progress on 30%: 18% of employees recorded Thornton Tomasetti Gives Back labor codes, indicating their use of paid hours for community service, on their time sheets in 2023. We expect to see more employees claiming community-service hours as awareness increases.

Making Progress on 90%: 67% of U.S. offices with access to the ACE Mentor Program are involved in the program. The program operates only in the U.S. and Canada. Only our smallest offices, with fewer than 10 employees, don’t participate. We expect greater involvement as these locations grow.

OVERVIEW Short-Term Targets

2023: We Met Our Short-Term Targets.

Last year, we shared three short-term targets to achieve by 2023, important steps toward achieving our corporate responsibility goals. We met all three. Here’s how:

20% of R&D Focused on Environmental or Social Outcomes

In pursuit of our goal of demonstrating positive environmental and social impacts across all practices, between 2022 and 2023 we increased the percentage of research and development projects we funded that are aimed at achieving environmental and social outcomes. In 2023, we funded 29 R&D projects proposed by staff through our innovation challenge. Fifteen of those, or 52%, met our criteria for this target. This funding supports exploration of such potential projects as increasing the capabilities of Beacon, our embodied-carbon measurement and tracking tool; using machine learning to develop a new method for evaluating bird-friendly glazing; and development of a natural ventilation calculator.

Maintain Over 80% Satisfaction With Flexibility

One way we pursue our goal of supporting a healthy workplace is to allow employees the flexibility to manage their personal and workplace responsibilities. Benefits can include increased productivity, stress reduction, improved employee satisfaction and reduced attrition. In an employee survey with a participation rate of 87%, 96% of respondents reported that they are satisfied with workplace flexibility, given the demands of their job. The responses show high satisfaction for both women and men.

Increase Community Service Hours by 10% Over 2022

In 2023, we saw a large jump of 55% over the previous year in community-service hours recorded on employee time sheets. We support our employees’ passion for community service through our Thornton Tomasetti Gives Back program, which pays employees to participate in local volunteer days, mentor students, and help disadvantaged communities. Communityservice hours dropped during the COVID-19 pandemic but have gradually risen back to prepandemic levels.

2024: We Look Ahead to Achieving These Short-Term Targets

We’re working to achieve these short-term targets by the end of 2024, moving us closer to achieving our corporate responsibility goals. We’ll report our progress in spring 2025, with the release of our next report.

• Set a baseline for achieving a 25% reduction in embodied carbon in structural frames.

• Reduce Scope 3 emissions by 2.5% from 2023 to align with the Science Based Targets initiative.

• Increase employee engagement in community service to 30%.

OVERVIEW Financial Vitality Progress Report

Each year, we report on several indicators (in U.S. dollars) that show progress toward achieving our financial-vitality goals. The trends this reveals can illustrate how our corporate responsibility programs contribute to our vitality over time.

Gross revenue is our total income from services. We continue to see strong financial returns from our work. Net revenue is billings from our services, excluding our expenses and bad-debt allowances. In line with our gross revenue, we continue to see growth.

Net project starts indicates the total revenue expected from projects that started in the reported year. Employee retention while not a direct financial indicator, is associated with financial vitality. Our retention rate remains high. Thornton Tomasetti is focused on equity, diversity and inclusion, knowledge sharing and career-development, and advancement initiatives to keep our retention strong. In 2023, 95% of employees stated in a survey that they would recommend the firm as a great place to work

Ford Foundation in Manhattan..

© Kenneth Laurence Neal

OUR PROJECTS

Introduction

Designing for a better world is the future of our industry. One of our corporate goals is to demonstrate that, through our work, we as design professionals can solve the most challenging social and environmental problems.

Our new Climate Action initiative is one way we’re pursuing that goal. Climate change is one of the biggest challenges facing our society. And because it affects everyone, it requires us to employ our utmost creativity, passion and collaboration to build a more enduring world. Our engineers, scientists, architects and sustainability experts support this initiative by applying their expertise in decarbonization and resilience to projects worldwide. Learn more by viewing our Climate Action initiative

The Past, Present & Future of Embodied Carbon: A Conversation With the Carbon Leadership Forum

Designingfor

Chris Erickson: CEO and CoFounder Climate Earth (which produces EPDs for the concrete industry), Founding CLF Member.

Amanda Kaminsky: Director of Sustainable Construction for Lendlease’s Americas Portfolio, CLF Advisory Board Member.

Amy Hattan: Thornton Tomasetti Corporate Responsibility Officer and Embodied Carbon Community of Practice Co-leader, Former CLF Board Member.

Kate Simonen: University of Washington Professor of Architecture, CLF Founder and Board Chair.

OUR PROJECTS

Our Projects Progress Report

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Each year, we track several indicators that show progress toward our goals for socially responsible and sustainable projects.

ENR Top 100 Green Buildings Design Firms Ranking:

Engineering News-Record’s annual Top 100 Green Buildings Design Firms ranking is based on the year’s design or construction revenue from projects that are green-building registered or certified by an independent rating organization (such as GBCI/LEED). Thornton Tomasetti continues to rank among the top 20 firms.

Number of Structural Projects Reported to SE 2050:

In 2020, we joined the Structural Engineers 2050 Commitment (SE 2050) as an inaugural member and have met our reporting requirement each year since. Before 2020, we measured embodied carbon for more than five years as part of an R&D project, the Thornton Tomasetti Embodied Carbon Lab. We shared that data as a member of the AIA 2030 Commitment and as a research partner of both the Massachusetts Institute of Technology and the Carbon Leadership Forum We continue to increase the number of projects in our annual embodied-carbon calculations toward our target of measuring embodied carbon for all our structural projects.

Number of Sustainability Consulting Projects:

Thornton Tomasetti began offering sustainability consulting in 2012. Since first reporting our project numbers in 2018, we have provided sustainability services, such as energy modeling net-zero strategies and green building consulting certifications for 757 projects. These projects encompass everything from dormitories to stadiums and are located around the world.

Reduction in Metric Tons From Sustainability

Consulting: The carbon dioxide equivalent (CO 2 e) reduction metric tracks the impact of energy-efficiency improvements from our sustainability consulting services. Each value is the sum of savings derived from energy modeling on sustainability projects completed that year. Since 2021, our work on all-electric and highly efficient buildings has continually increased.

OUR PROJECTS

Our Projects Progress Report

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Each year, we track several indicators that show progress toward our goals for socially responsible and sustainable projects.

Average Per-Project Savings From Sustainability Consulting: Average per-project cost savings are derived from the average energy cost savings from our sustainability consulting projects each year. Large-scale projects contributed to a growth in total savings in 2022. The 2023 dip reflects the higher baseline performance for a “typical building” caused by more stringent energy codes.

Employees With Green Building Accreditation:

More than 200 of our employees have a green building or a broader sustainable design accreditation. These include LEED Green Associate (GA), LEED Accredited Professional (AP), and other sustainability accreditations outside the LEED program, such as WELL Accredited Professional (AP) and Envision Sustainability Professional (SP).

Research and Development Spending:

Our R&D spending includes staffing and other expenses for CORE studio, our virtual idea incubator, as well as support for traveling innovation tournaments that identify and fund ideas from employees across the firm. We continue to prioritize R&D in pursuit of our long-term goal of becoming the global driver of change and innovation in our industry. In 2023, we saw a significant rise in R&D funding and an increase in the number of project ideas that target environmental improvements.

OUR PROJECTS

Climate Action Innovations

Climate change is one of the biggest challenges facing our society. And because it affects everyone, it demands our creativity, passion and collaboration to build a better, more enduring world.

• AI & Machine Learning for Climate Prediction

• A Greener Floor System

• Next-Gen AI Energy Modeling

• Optioneering Façade Embodied Carbon

• Sustainable Façades Get Greener

Energy Demand Projects

We’re helping create a more sustainable built environment by measuring, tracking and eliminating embodied and operational carbon in everything from individual buildings to entire neighborhoods.

• London’s Lowest-Embodied-Carbon Building

• Making Thermal Networking Work

• Mass Timber on a Large Scale

• The Long Decarbonization Game

Energy Supply Projects

Energy supply consists of all the primary energy sources used in power generation as well as direct fuel production. Increasing the share of renewables – a defining feature of the energy transition – and particularly wind and solar in the energy mix is an effective method of reducing the emissions.

• All Power to the Energy Transformation

• Growing Energy Independence

Resilience Projects

Our interdisciplinary team develops practical strategies to adapt to current and future climate risks, ensuring the resilience of projects over the short, medium and long terms.

• Going Against the Flow

• Preparing for a 500-Year Flood

Smoothed Common Practice Smoothed Ai-Based Method

OUR PROJECTS: Climate Action Innovations

AI & Machine Learning for Climate Prediction

Climate risk assessments that inform how the built environment might accommodate future weather rely heavily on climatemodel predictions derived from historical trends and data. AI presents an exciting opportunity to explore new ways to model these conditions.

Using 70-year continuous historical datasets recorded by the National Oceanic and Atmospheric Administration, we trained ML models to predict an hourly temperature dataset that can be used in building analytics to estimate monthly heating and cooling demand.

Incorporating additional information, like additional data stations, dry and wet bulb temperatures, dew point and relative humidity, we trained the model to predict hourly temperature data for 2020. The predicted and measured data track each other closely.

Our AI models, overall, produced less error than the common practice ( University of Southampton’s CCWorldWeatherGen ), which underpredicts heating demand and overpredicts cooling load. Further refinement of our approach should lead to improved building design and economic modeling of heating/cooling demands.

Measured Temperature vs. AI and Common-Practice Models. Thornton Tomasetti

OUR PROJECTS: Climate Action Innovations

A Greener Floor System

Conventional floor cassettes (prefabricated floor panels) are low-carbon, but because their fire, acoustic and vibration performance is limited, they’re used primarily in smaller buildings. Our patented GreenBox ® system is just as efficient – and it’s robust enough to use in large residential and commercial buildings.

Constructed of wood and recycled materials, GreenBox is beautiful and lightweight and can cut the embodied carbon in a building’s floors and frames by up to 40%, compared to concrete or cross-laminated timber flooring. And it’s easier to install. With an innovative filling that provides superior insulation, vibration damping and up to two hours of fire protection, GreenBox equals or exceeds the performance of other floor systems.

The sustainability benefits of GreenBox are matched by its biophilic appeal. Look up in a GreenBox building and you’ll see an attractive wood soffit with few, if any, down-stand beams. The standard GreenBox panel looks great – and specialty plywood can be used for customized architectural effects.

Thornton Tomasetti

OUR PROJECTS: Climate Action Innovations

Next-Gen AI Energy Modeling

Today’s energy modeling is a tedious process: chasing down myriad inputs, followed by weeks of modeling and analysis – only to arrive at an answer that is out-of-date because the design or procurement has moved on.

We’re revolutionizing this process, using AI/ML to deliver instantaneous results. This research, led by Associate Principal Vamshi Gooje, involves training a model on thousands of projects, spanning 20 years, including open-source databases. This speed allows for immediate feedback, real-time collaboration and swift decision-making.

While conventional modeling remains essential for addressing nuanced questions and compliance verification, our focus is on enhancing AI/ML model accuracy and forecasting operational carbon. It’s a transformative approach, streamlining a once-lengthy process into a rapid, data-driven solution for the future.

Traditional modeling of HVAC system performance takes two weeks for buildings like this assisted-living facility in Scarborough, Maine. Our AI/ML approach produces a first model in seconds.

Thornton Tomasetti

OUR PROJECTS: Climate Action Innovations

Optioneering Façade Embodied Carbon

Asked why he robbed banks, Willy Sutton reputedly replied, “Because that’s where the money is.”

Following Sutton’s law, engineers trim the largest sources of embodied carbon (EC) – the frame and concrete floors – but often overlook the significant carbon embodied in the façade

We’re developing a parametric tool to calculate the life-cycle EC of a façade panel based on its geometry and materials. Any design variable – such as bay dimensions and number of façade elements – can be modified to estimate its effect on EC.

Thornton Tomasetti

Next, we’ll add more façade types and ensure accurate component data, which varies by fabricator. Then we’ll determine a correction factor, since at schematic design, the contractor might not have identified each material’s supplier. The goal is to provide the project team with a reasonable range of façade EC for a given design.

OUR PROJECTS: Climate Action Innovations Sustainable Façades Get Greener

At the 2023 Architectural Ceramic Assemblies Workshop in Buffalo, New York, our façade engineers were part of a team that developed a prototype for a curtain-wall-supported green screen-wall system that promotes moss growth on terra cotta.

Moss has many eco-friendly properties, such as exceptional carbon-sequestration, water-retention and air-filtration capabilities, and it readily adapts to varying ecosystems. And root-free moss requires less maintenance than green walls that use other plants.

The terra-cotta-and-moss screen wall is supported by a backup curtain wall that allows building occupants to view the moss as growth spreads to the back of the panels.

Thornton Tomasetti

OUR PROJECTS: Energy Demand Projects

London’s LowestEmbodied-Carbon Building

In February 2024, the City of London’s lowest-embodied-carbon (EC) building topped out in the city’s finance and insurance center. The 350,000-square-foot Stonecutter, a mixed-use office and commercial development, aims for net-zero carbon by cutting EC in several ways.

To avoid the need for temporary works and excavation – and archaeological risk – the new basement lies within the volume of the old one. This approach reused existing piles and sidestepped the need for excavation, but required a lightweight structure. Our long-span design doubles the floor area of the previous building while maintaining the same weight and enlarges the bays by 250%. Avoiding groundworks also accelerated construction, providing significant cost savings while supporting a low-EC approach and circular-economy principles.

To further reduce Stonecutter’s carbon footprint, we decarbonized our structural materials specifications. For example, we replaced 60% of cement with slag in concrete where curing time wouldn’t slow the construction program – 45% of the total used. And for another 9% of the project’s concrete we used at least 50% slag. We selected steel sections produced by electric arc furnace (EAF), which emits about one-third the carbon of blast-furnace production. Altogether, our approach yielded an EC footprint of 550 kgCO 2 e/m 2 , which places it in the City of London’s “aspirational” class. The 13-story building is also targeting BREEAM Excellent and WELL Gold standards.

A broad approach to embodied-carbon reduction drove Stonecutter to the lowest levels so far for the City of London.

Courtesy V1

OUR PROJECTS: Energy Demand Projects

Making Thermal Networking Work

The retrofit of the historic 345 Hudson Street office building adapts the Nordic idea of thermal networking to drastically reduce energy demand and carbon emissions.

Heat recycling and sharing with nearby buildings cut energy demand by 30% and will reduce CO 2 emissions by 90% by 2040, when New York City’s grid is scheduled to go all-electric.

Our multidisciplinary team led several aspects of the retrofit, including a new lobby connection to the adjacent building and elevator machine room structural repair and relocation. We also conducted forensic evaluation of the structure and façade, augmenting manual façade inspections with AI-driven T2D2 drone surveys to identify needed repairs or replacements. And we wired the building and the one next door to monitor vibration.

“Overlapping schedules and multiple design and construction teams running simultaneously, sometimes in adjacent areas, required intensive coordination,” says Yasser Khalifa, Thornton Tomasetti vice president and project manager. “Daily briefings and coordination within and between all teams made for steady progress and quick resolution of issues.”

The result? When completed this year, 345 Hudson will become one of New York’s most sustainable buildings and, says Benjamin Rodney, vice president with Hines (a partner of Hudson Square Properties ), “It will showcase how ingenious design and engineering can help convert brown assets (buildings with excessive energy and carbon impacts) into green assets that are ready to take advantage of an all-electric, low-carbon energy future.”

Building a cohesive team that could coordinate between the different projects as been critical to ensure success.

– Benjamin Rodney, Hines

Anthony Magliozzi (Hines), Kyle Dew (Thornton Tomasetti), Yasser Khalifa (Thornton Tomasetti) and Gavin Ennis (Hines) at 345 Hudson Street.

Thornton Tomasetti

OUR PROJECTS: Energy Demand Projects

Mass Timber on a Large Scale

When Under Armour (UA) started planning a new building on their Baltimore, Maryland, campus, they wanted it to reflect their commitment to optimizing performance and acting sustainably.

We helped architect Gensler to embody these values in the design of Teammate Building 2 (TMB2) , UA’s new global headquarters. The 280,000-square-foot office building is being constructed almost entirely of mass timber – an ecoconscious choice that cuts the structure’s embodied carbon (EC) and imparts an appealing aesthetic to its interior spaces. Our structural design also supports a rainwater capture system, a green roof and a canopy carrying photovoltaic panels to help the new headquarters achieve net-zero-energy operations.

During the first phase of design, we collaborated with Gensler to develop structural schemes for mass timber, concrete and steel to uncover the pros and cons of each. We calculated quantity estimates for all three and used Beacon – the EC-tracking Revit plug-in we developed – to assess the EC impacts of all three materials. These details helped UA evaluate the options and make a fully informed decision to choose timber.

When Austrian mass-timber supplier binderholz was selected, we engaged with their team on the design of structural components. Switching from imperial to metric measurements was just one part of it. Collaborating closely, we evolved our design to accommodate their proprietary connections and adjust member sizes to match their fabrication practices. “Mass timber hasn’t standardized yet,” says Thornton Tomasetti Associate and Lead

Engineer Doug Schweizer, “so conforming our structural details to their preferences was much more cost-effective than specifying custom shapes. And at the same time, we could make sure the final design didn’t stray from Gensler’s vision.”

There’s still a massive learning curve when it comes to mass timber projects of this scale. Working with trusted partners allows for a smooth process to ensure we deliver on the client’s vision and desired experience.

– JJ Rivers, Gensler

The mass timber design for TMB2 has 50% less embodied carbon than concrete and 65% less than steel. Thornton Tomasetti

OUR PROJECTS: Energy Demand Projects

The Long Decarbonization Game

A revitalization of Brooklyn’s Boerum Hill neighborhood paved the way for the Alloy Block, Downtown, a mixed-use redevelopment that includes Brooklyn’s first all-electric residential tower. We’re providing architect/developer Alloy with sustainability consulting services for the ambitious project.

Plans for the residential tower, called 505 State Street , were based on three goals: to foster a connection to place, improve energy efficiency and design for future decarbonization. “Through the development process, we redefined the future of responsible building in Brooklyn,” says Jeffrey Sullivan, vice president of architecture at Alloy. “This was achieved through extensive collaboration among Alloy, Thornton Tomasetti’s sustainability team, city agencies and the local community.”

“Because we were aiming for an innovative approach, the entire project team came together from the start,” says Thornton Tomasetti Vice President Jose Rodriguez. We knew going in that electric heating technology was not yet commercially viable. We also knew electricity service to the area relied heavily on generation from natural gas, which produces greenhouse gas emissions and other pollutants. But ConEd had committed to building a zero-carbon electric grid by 2040, which let us look several moves ahead.

We focused first on reducing the building’s energy loads, then on electrifying its systems to eliminate on-site fossil fuel usage. We modeled the impacts of thousands of inputs – including simulated façade-performance values, infiltration rates and ventilation-recovery effectiveness – to find the combination of variables that yielded the lowest heating load. Our process

turned conventional energy modeling on its head by choosing an output aligned with our performance goals and working backwards to identify inputs to hit the target.

We worked with Alloy, Con Edison, the New York State Energy Research and Development Authority, and façade and MEP partners to understand what was possible and what measures we could evaluate for future implementation.

– Jose Rodriguez, Thornton Tomasetti

The first components of the development, the 505 State Street tower and the 350-seat Khalil Gibran International Academy (the city’s first public school building designed to Passive House standards) will be completed in 2024.

Thornton Tomasetti/Courtesy Alloy Development

OUR PROJECTS: Energy Supply Projects

All Power to the Energy Transformation

Collaboration between our forensics and applied science experts is helping safely demolish coal-fired power plants to make way for greener energy production in California, Georgia, Illinois, Kentucky, North Carolina and Ohio.

Our applied science team develops high-fidelity engineering simulations of explosions and explosive felling, dust cloud dispersion and vibration. A deep understanding of why structures fail helps our forensics specialists effectively analyze them, plan controlled destruction – by explosive felling or mechanical deconstruction – and prevent accidental collapse.

Combined, these skill sets provide an unmatched ability to manage safety and mitigate risk during the demolition of outdated power plants.

We partner with utilities, helping plant owners develop RFP (request for proposal) specifications that include robust safety and risk-management provisions or performing peer reviews of demolition plans. We also team with demolition contractors to determine the best approach for each project and devise means and methods. “When a contractor brings us in during the pre-bid phase, it shows that they’re proactive about managing risk,” says Vice President Mahesh Bailakanavar. “And that can set a really positive tone with the utilities.”

We’re working with B&B Wrecking and Excavating on demolition of the 1960s-era coal

W. H. Sammis Power Plant in Stratton, Ohio.

Thornton Tomasetti

OUR PROJECTS: Energy Supply Projects

Growing Energy Independence

Can a working farm become 100% self-reliant? We’re helping answer that question at Northeast Scotland’s HydroGlen demonstration project.

On-site wind and solar electricity generation with battery storage can meet part of the energy demand. Hydrogen production (using electrolysis), combined with fuel cell technology, will provide the rest. Together, they’ll power all the farm’s operations, including electric and hydrogen-fueled vehicles.

Green hydrogen – with its capacity for energy-dense compressed storage – is a clean and affordable replacement for hydrocarbons in gas turbines, boilers and combustion engines. Our applied science team provided hydrogen and hazard management expertise, working closely with our project partners to develop the design of HydroGlen’s hydrogen system.

The Glensaugh farm’s transformation into HydroGlen will show how the agriculture sector can help Scotland become a net-zero greenhouse-gas emitter by 2045.

Courtesy The James Hutton Institute

OUR PROJECTS: Resilience Projects

Going Against the Flow

When the remnants of Hurricane Ida hit New York City in September 2021, torrential rains flooded the New York Hall of Science (NYSCI) in Queens.

While making extensive repairs, the organization called in our resilience specialists to prevent substantial damages from happening again.

Our team, led by Vice President Aditya Bhagath, started with climate-hazard and stormwater assessments. A hydrological analysis of the watershed revealed that NYSCI’s front door is at a low point within the neighborhood. These findings informed short-term measures, like relocating the primary entrance, that would protect NYSCI while other flood resilience solutions were developed. The predicted water volume and associated depths also guided our design of a semipermanent flood-barrier system.

NYSCI is considering long-term measures, such as landscaping to divert floodwaters, permanent exterior flood barriers and flood-proofing for operations-critical rooms. These strategies factor in scientific data forecasting increasingly severe weather events fueled by climate change.

The current flood-barrier system had its first real test during a cloudburst event in April 2023. It kept the water out, and NYSCI stayed dry.

Vice President Aditya Bhagath inspects the semipermanent flood-barrier system. Thornton Tomasetti

OUR PROJECTS: Resilience Projects

Preparing for a 500-Year Flood

Located on the Spuyten Duyvil Creek tidal estuary in Upper Manhattan, the Philip & Cheryl Milstein Family Tennis Center is the heart of the Baker Athletics Complex. The facility features a unique design that allows floodwater to flow through the building while protecting mechanical systems and other operations. The design adds resilience to current and future climate risks, including coastal and tidal flooding, heavy rainfall, extreme heat, high winds and severe winter weather. Incorporating these considerations was part of a riskinformed, future-focused approach that reaches beyond New York City codes.

Building the facility high enough off the ground to avoid a 500-year flood would have been prohibitively expensive, so our resilience team developed a series of vents that open to allow water to flow in and out of the first floor during a storm.

Finishes on the first floor were selected for their resistance to water damage, so when stormwater subsides, the courts can be cleaned and used immediately.

We provided multihazard climate risk assessment , resilience consulting and design, and structural engineering services to Perkins&Will for the two-story building. The facility, which contains six indoor courts and six outdoor rooftop courts, also provides fitness, meeting and recreation space for alumni, affiliated hospital staff, faculty, students and their families.

The tennis center is designed to flood and quickly recover, making it ready for current and future climate risks from the outset.

Thornton Tomasetti

We aspire to be one of the world’s most sustainable firms, both in the way we design our projects and in how we operate as a business.

The Thornton Tomasetti San Francisco office. Thornton Tomasetti

SUSTAINABLE OPERATIONS Introduction

We aspire to be one of the world’s most sustainable firms, both in the way we design our projects and in how we operate as a business.

Our commitment to cutting carbon starts at home, with our goal of achieving carbon-neutral business operations by 2030. Most recently, we bolstered this commitment by joining the Science Based Targets Initiative (SBTi) for setting science-based emissions reduction targets. We engage our employees in the global effort to mitigate and adapt to climate change by establishing internal policies and practices, such as sustainable office guidelines, that complement our corporate responsibility goals. We’re committed to promoting sustainability – not just within our firm but across the industry and throughout our supply chain.

We aspire to be one of th e world ’s most sustainablefirms .

Decarbonizing the AEC industry requires global collaboration from everyone in the value chain. During Climate Week NYC in September 2023, we hosted a panel of experts from across the AEC industry to discuss how to work together to achieve this goal. Click the title above to view the video. Thornton Tomasetti

SUSTAINABLE OPERATIONS

Sustainable Operations Progress Report

(Page 1 of 2)

Each year, we track several indicators that show progress toward achieving our sustainable-operations goals. The trends revealed by this data show us where we need to stay the course and where we need to make changes.

Total Carbon Footprint (MT CO 2 e): We reduced absolute operational emissions by 35% from 2018 and by 3.5% from 2022. Factors in the reduction of our carbon footprint include the overall greening of the electrical grid, corporate renewable-energy purchases and air-travel emissions reductions. While we purchase offsets to cover 100% of our air-travel emissions, we report our emissions without offsets, in line with global reporting standards. We have stayed on track with our emissions-reduction targets each year, with emissions falling below the levels estimated for a 5% reduction per year.

Before 2022, we conducted biennial emissions inventories; we shifted to annual analysis starting in 2023. The scope of our inventory includes all offices except for a small number of offices with fewer than 10 employees. The data are primarily in CO 2 e, except for those from our offices in India, China and Vietnam, where electricity emissions factors are given in CO 2

Reduction of CO 2 e Emissions From Purchasing

Offsets and RECs (MT CO 2 e): We reduce our emissions even more by offsetting our annual flight emissions and purchasing renewable energy to cover some of our electricity use. In 2023, we achieved our greatest carbon-emissions reductions through the purchase of Renewable Energy Certificates (RECs) for every U.S. office’s electricity use. Because air travel has increased since 2020, purchased offsets have covered a larger amount of carbon emissions compared to the last two years.

Total Electricity Consumption (kWh): Since 2018, we’ve reduced electricity consumption in our leased offices by 25%. We’ve dramatically reduced our electricity use since the pandemic in 2020 and have only gradually increased our kWh usage since. This is largely due to high-performance offices with energy-efficient appliances and LED lighting, and to sustainable office fit-outs that have achieved LEED certification or were designed using our sustainable bestpractices policy. Only data from offices included in our annual emissions inventory is included in this analysis.

SUSTAINABLE OPERATIONS

Sustainable Operations Progress Report

(Page 2 of 2)

Total Fuel Consumption (MMBtu): Since 2018, we have reduced fuel consumption in our leased offices by 38%. Our offices in warm climates don’t use heating fuels, and some others are becoming fully electric. As more of our offices run on electricity alone, and our electric grids become greener, we can reduce overall building emissions. Only data from offices included in our annual emissions inventory is gathered for this analysis.

Annual Carbon Footprint

Employee (MT CO 2 e):

greater reduction in per capita emissions compared to our absolute emissions can be attributed to the firm’s continuous workforce growth, at roughly 10% more employees per year. Our per capita emissions for 2023 are 2.05 metric tons of CO 2 e, which is a 12% reduction from the prior year.

Since 2015, we have been a member of the Environmental Protection Agency’s Green Power Partnership, which requires 25% of our

to come from

This year, 100% of our offices in the U.S. procured green power through REC purchases. Our green energy purchasing strategy keeps us well under our Scope 2 specific-office energy reduction goals and SBTi targets.

SUSTAINABLE OPERATIONS Emissions Report

In pursuit of our goal of carbon-neutral business operations by 2030 – and in line with the Science Based Targets initiative (SBTi) – we’re aiming for a 5% reduction in absolute CO 2 e emissions (from 2018 baseline levels) each year. To achieve carbon neutrality, we’re reducing carbon emissions wherever possible and purchasing offsets to cover the rest.

In 2023, our absolute emissions declined by 3.4% from the previous year, despite a 10% growth in our workforce. Per capita emissions continued to drop, with reductions of 12% from 2022 levels and 53% from the 2018 baseline. And for the first time, we purchased Renewable Energy Certificates (RECs) for green power for all U.S. offices.

We accomplish reductions by:

Designing or moving into high-performance offices. We design every newly leased office space to meet energy-efficiency standards set forth in our Sustainable Fit-Out Policy, based on the best specifications of LEED and other green-building rating systems. For existing offices, we offer grants and other resources to encourage our green champions to implement energy-efficient retrofits.

Purchasing renewable energy. We are a member of the U.S. Environmental Protection Agency’s Green Power Partnership, and we’ve met the program’s green-energy purchasing percentage targets every year since 2015. Our annual purchase of RECs, now covering 100% of our U.S. offices, brings the net carbon footprint of our U.S. office electricity emissions to zero.

Reducing air-travel emissions. Because as a service firm we don’t often work directly with major suppliers, a large portion of our Scope 3 emissions originates from business travel. We avoid unnecessary travel by hosting meetings remotely and by centralizing large internal meetings. When travel is unavoidable, our travel policy encourages employees to choose lower emissions options like trains, nonstop flights and economy seating.

Renewable Energy Purchases

In this, our ninth year of offsetting all air-travel emissions, the offsets we purchased contributed to the Landfill Methane Gas to Energy project in New Bedford, Massachusetts. This project, which is not far from our Boston office, converts methane emissions from New Bedford’s landfill into liquified natural gas to be used as fuel.

We’re committed to pursuing the SBTi’s near-term targets, and next year we’ll set science-based reduction targets for our Scope 2 and 3 emissions, per SBTi guidelines. And we’ll further inspire reductions in energy consumption by upgrading our datamanagement and visualization technologies.

SUSTAINABLE OPERATIONS

Green Offices Report

As part of our efforts to achieve carbon-neutral business operations by 2030 and reach science-based emission-reduction targets, we’re moving into higher-performance offices and making our existing ones as efficient as possible.

When our offices move to new locations, our Sustainable Offices Fit-Out Policy prescribes fit-out guidelines based on green-building and wellness certifications like LEED and WELL. The recently revised policy offers greater flexibility and a broader reach across the firm than our former program, which required LEED certification for all our larger offices and did not touch all offices. In 2023, our San Francisco and Boston offices moved, and both are pursuing LEED Gold certification for their fit-outs.

Depending on its goals, each location may focus on different aspects of the policy. Chicago’s design, for example, was aimed at encouraging teamwork by incorporating collaborative areas throughout and including no private offices. All workstations have views to the outdoors, and the fit-out incorporated several energy-efficiency features, including LED lighting with vacancy sensors and an electricity submeter.

Eleven of our current offices hold green-building certifications (or have applied equivalent strategies). In total, 14 – past and present – have been designed to green standards.

Our green champions (employee volunteers who support corporate responsibility initiatives) help their offices reduce energy consumption and waste and meet carbonneutrality goals. They also coordinate activities that promote wellness and community service and contribute to climate-action education by organizing events like Earth Week and Daylight Hour (when we extinguish all artificial lighting). In 2023, we averaged around 65 green champions in 33 offices worldwide.

In 2023, we awarded $50,000 in corporate responsibility grants to 19 offices, which used the funds to pay for items or programs that support our corporate responsibility goals. For example, our Warrington England, office used its grant to fund an LED overhead lighting retrofit; our Boston office installed a “green wall” display of indoor plants; and our new Chicago office started a composting program.

Earth Day 2023 in our Portland, Maine, office. Thornton Tomasetti

SUSTAINABLE OPERATIONS

Sustainable Procurement

As designers and consultants in the AEC industry, we rarely become involved in the purchase of building materials or other project-related resources, so our direct procurement activities tend to be limited to the purchase of office supplies.

In cases where we can influence the selection of project materials, we apply our inhouse specifications, policies, and sustainability expertise. We seek trusted partners who share our value of responsible procurement, and we educate clients and collaborators about sustainable options for their projects.

Building Materials

One pillar of our environmental policy is to find creative ways to reduce carbon in our projects. To help accomplish this, we developed the Beacon embodied-carbon assessment tool and embodied-carbon specifications for designers to apply when sourcing building materials like concrete, steel and timber. These specifications direct project teams to consider materials or adjustments to materials that are less carbon intensive than the standard options. Our sustainability consultants conduct lifecycle assessments to guide material choices for projects and help clients avoid toxic materials identified in the Living Building Challenge Red List.

When hiring subconsultants or specifying project materials, we follow our ethical sourcing policy which outlines our commitment to using products that are sustainably sourced and those that are manufactured in fair and safe work environments. In pursuit of this vision, we’re collaborating with Grace Farms in a Design for Freedom supplychain mapping initiative. The policy also encourages the hiring of small and minorityowned businesses or firms that have demonstrated a clear mission of promoting social equity.

Office Supplies

Our sustainable office guidelines recommend the purchase of office supplies with high recycled content and low toxicity in our 43 offices around the world. Our operations staff meet regularly to discuss options for sustainable purchasing and have continued to buy kitchen and office supplies from vendors committed to sustainability.

More than half our purchases from Amazon were certified Climate Pledge Friendly a designation awarded to products that have received sustainability certifications deemed by Amazon to be “reputable, transparent, and have a focus on preserving the natural world.” We also urge our operations staff to purchase Emerald brand sustainable products, which are designed, manufactured and distributed by Paradigm Group.

Most of our offices provide reusable dishes and kitchen utensils and offer compostable or recyclable alternatives as backup. In 2019, we introduced a policy that limits our use of beverages in plastic bottles.

For our most recent Owners’ Week, an annual gathering of 200+ staff that takes place in our New York office, we purchased food from local woman- and minority-owned businesses. We look forward to continuing this practice into the foreseeable future.

By initiating a process for minimizing waste at the printer, we’ve significantly reduced the amount of paper we use, and we continue to use paper with recycled content and work with providers who adhere to sustainable forestry standards like those of the Forest Stewardship Council and PrintRelief Certified Reforested.

The Thornton Tomasetti Boston office.

Thornton Tomasetti

HELPING OUR COMMUNITIES

We support our employees’ passion for community service.

Employees in our Perth office volunteered at Dismantle, a youth development program that uses bicycle mechanics as a tool to empower young people.

Thornton Tomasetti

HELPING OUR COMMUNITIES Introduction

We support our employees’ passion for community service.

Our employees have unique abilities that can add value to their communities, and they want to share their skills with others in need. Our Thornton Tomasetti Gives Back program compensates employees with paid hours and other support for helping schoolchildren through the ACE Mentor Program , volunteering for local organizations and helping disadvantaged communities.

We partner with Bridges to Prosperity to build footbridges in rural communities to bolster economic development. Our charitable giving benefits many of the organizations where we volunteer and supports disaster-relief efforts, as well as the Thornton Tomasetti Foundation

Our team of volunteers built a footbridge in Rwanda's Southern Province to benefit 2,300 local residents.

Click the title to watch a video about the project.

Thornton Tomasetti

HELPING OUR COMMUNITIES

Helping Our Communities Progress Report

Each year, we track several indicators that show progress toward achieving our community service and philanthropy goals.

Company-Paid Community Service Hours: The companypaid community service hours metric tracks the on-theclock hours our employees spent in community service activities, including hours for local volunteerism through our Volunteer Days benefit and half the hours employees spent participating in the ACE Mentor Program Hours contributed to Bridges to Prosperity increased in 2023 as we returned to Rwanda for the first time since the pandemic. We are meeting our goal of increasing employee service hours by 10% each year.

Volunteer Days Benefit Claimed (Hours): Our Volunteer Days benefit allows employees to receive compensation for up to two days per year for community service activities. This metric tracks the hours employees logged under the “volunteer day” code on their time sheets. It does not account for volunteerism by employees in their personal time. The 43% increase in use of the benefit from 2022 to 2023 is the result of more group community service events organized by green champions and employee network groups, as well as our post-pandemic return to constructing bridges in Rwanda.

Company-Paid Student-Mentoring Hours: We track company-paid participation (time spent in mentoring or board membership activities) in the ACE Mentor Program, an organization serving high school students in the U.S. and Canada that was initiated by Thornton Tomasetti Founding Principal Charles Thornton. ACE volunteers are paid for 50% of their hours spent – an average of 15 per year. Because remote programming enabled employees to continue to serve during the pandemic, our participation remained steady throughout and has now begun to climb. Each year, we encourage employee involvement in the program through our ACE Mentor Appreciation Week.increased philanthropy.

Charitable Contributions: Charitable contributions include all payments in each year coded as “donations” in our accounting system. This includes annual contributions – such as those to the Thornton Tomasetti Foundation, Bridges to Prosperity and the ACE Mentor Program – and donations by our offices to local charities. It doesn’t account for contributions like pro bono work for

at universities and colleges, or labor hours spent performing community

– only tracked as “hours,” as described above. Contributions increased by 42% from 2022 to 2023, an indicator of a full return to pre-pandemic donations and a reflection of our new matching program for employee donations to the Red Cross.

HELPING OUR COMMUNITIES

Charitable Giving

Through our charitable initiatives, the firm and our staff support the next generation of professionals, strengthen the communities where we live and work, and help people in disadvantaged regions of the world. Our financial contributions align with many of the initiatives and organizations our employees support through their volunteerism.

In 2023, we donated $525,486 to charities and educational organizations, an increase of 42% over the previous year. We continued to provide support to the national ACE Mentor Program and its regional chapters, as well as to the Salvadori Center, Bridges to Prosperity, the Lee Petrella and Daniel A. Cuoco Memorial Scholarships, and the Thornton Tomasetti Foundation a 501(c)(3) organization that funds scholarships and philanthropic organizations in the AEC sector.

Thirty-three percent of our giving is decided at the local level. As a result, we provide financial support to a wide range of organizations and initiatives in different regions. In autumn 2023, several of our offices provided free school supplies to children. Among them were our Florida offices, which worked with HandsOn Broward to hold back-toschool drives and donated backpacks containing classroom essentials. Locally, we also supported organizations like St. Francis Food Pantry and Canstruction (New York, New York), the Ride to End Alzheimer’s (Denver, Colorado) and Cycle for Survival (Washington, D.C.).

In 2023, we initiated an ongoing program to match employee contributions to the Red Cross disaster relief campaign raising $20,680 in the first year. This partnership, which augments our previous practice of sporadically matching donations, was created in response to employees’ desire to help with disaster relief in areas where they live and work. This year, we also initiated a program of donating used laptops that are still in good working order to the ACE Mentor Program for use by participating high school students. This initiative was inspired by our Mumbai , India, office, which had donated used IT equipment to the village school in Karjat.

Our full scope of charitable giving is estimated at more than 1% of our net profits. This accounts for staff donations of more than 3,000 hours for community volunteerism and lecturing at colleges and universities. We also provide pro bono professional services to nonprofit clients.

Thornton Tomasetti team members pose with local schoolchildren while visiting Nyagisumo, Rwanda, to construct a footbridge with Bridges to Prosperity. Thornton Tomasetti

For CANstruction NYC 2023, our team built a canned-food version of Katsushika Hokusai's Great Wave Off Kanagawa. Click the title to watch a video of the build. Thornton Tomasetti

HELPING OUR COMMUNITIES Community Service

In five years, Thornton Tomasetti Gives Back has funded 4,140 hours (about 517 days) of “employee's choice” community service and 5,116 hours (about 640 days) for coaching high school students through the ACE Mentor Program

Our community-service initiative nurtures our people’s passion for volunteerism, encourages personal growth and promotes collaboration and lasting relationships. According to the Society of Human Resource Management, which offers the longestrunning annual survey of employee benefits in the U.S., only 28% of U.S. firms offer paid time off to employees who volunteer.

Our three-pronged “giving back” program includes our Volunteer Days benefit, which allows 16 paid hours per year for each employee to engage in community service. Between 2022 and 2023, the number of Volunteer Days hours used by employees grew by 55%, with 217 people volunteering in 19 locations. In 2023, employees participated in a wide range of charitable activities, often through group events in their offices. Among their many volunteer pursuits, some served as STEM ambassadors in London schools, while others organized an engineering-careers Day of Discovery for schoolgirls in New York City, planted trees in Mississauga, Ontario, Canada, or participated as mentors in capstone projects at various universities. Also in 2023, our Chicago office became a founding contributor to the ADEPT program pairing professional mentor-coaches with college students to advocate for aspiring Black and Brown engineers.

Because so much of our legacy as a firm comes from nurturing the next generation of AEC professionals, we continue to support and volunteer with the ACE Mentor Program, created by Founding Principal Charles Thornton. We’ve seen a 43% increase in mentoring hours since 2022, with 127 employees mentoring high school students or serving as board members in 14 locations. Since 1994, our people have been volunteering to help achieve ACE’s mission to engage, excite and enlighten high school students, empowering them to pursue AEC careers.

In addition to the local community services we provide, through our partnership with Bridges to Prosperity , our employees travel to Rwanda each year to help construct pedestrian bridges serving isolated rural communities. In 2023, our team constructed an 80-meter trail bridge in the Nyamagabe District of southern Rwanda serving more than 2,000 people and giving 840 children a safer way to get to school. Since we started this program, our employees have helped construct four bridges, enabling safe access to economic opportunity for more than 10,000 people.

“One way we aided the community was by helping build the bridge, but another way was by visiting the school and teaching the kids. We also donated school supplies, books and toys. The areas where Bridges to Prosperity works are remote, hard to get to and lack resources – these are things that sometimes we take for granted,” says Samantha Eng, a forensic engineer in our San Francisco office and 2023 Bridges to Prosperity team member.

“What stood out to me during the closing ceremony was listening to the community members talk about the impact of the bridge and hearing about the difficulties they faced before it was built and their hopes for a brighter future,” says Frank Fang, a structural engineer in our New York office and 2023 Bridges to Prosperity team member.

Twenty-five volunteers rode the ferry to Governors Island, where they tended GrowNYC’s one-acre teaching garden and learned about the farm and how to identify plants. They then separated into groups to organize seeds and perform landscaping work. It was a golden opportunity for staff to experience nature, work with their hands, enjoy time with their colleagues and – most importantly – give back to the community. Funding for the event was provided by our annual corporate responsibility grants program.

Thornton Tomasetti

In September 2023, our New York green champions and Mosaic , our multicultural employee network group, arranged a volunteer outing with GrowNYC a nonprofit organization that distributes locally grown food to people whose access to produce is limited. Thornton Tomasetti

HELPING OUR COMMUNITIES Disaster Response & Relief

In 2022, immediately after Hurricanes Ian and Nicole, our engineers and forensics specialists visited Florida and other impacted areas along the Eastern Seaboard to evaluate the damage and aid recovery efforts.

This work continued through 2023. We also sent a team to perform reconnaissance work after a 7.9 magnitude earthquake struck Turkey and Syria.

In 2023, we formalized a partnership with the American Red Cross to provide financial support to the organization’s disaster-relief campaigns through a donation-matching program. Thornton Tomasetti now matches staff donations to the Red Cross up to a total annual contribution of $100,000. Employees can contribute to specific campaigns or allow the charity to allocate the funds where they are most needed. This program enables faster response to disasters and doubles the impact of employee donations.

This year, $18,000 in combined donations from the firm and our employees went to relief efforts after multiple earthquakes shook southern Turkey and northern Syria, resulting in widespread loss of life and infrastructure damage. The firm also made donations for relief after Category 4 Hurricane Idalia swept the Big Bend region of Florida (which encompasses our Tampa office) at Category 3 strength.

After multiple earthquakes struck Turkey in 2023, causing widespread structural damage, we performed reconnaissance work in the affected area.

Courtesy Engineers in Action. Background ©Triff/shutterstock.com

HELPING OUR COMMUNITIES Thornton Tomasetti Foundation

The Thornton Tomasetti Foundation (TTF) is an independent 501(c)(3) organization that helps students prepare for careers in building engineering, design and technology by funding scholarships and fellowships for undergraduate and graduate students.

Thornton Tomasetti Foundation also supports initiatives that help communities around the world by providing financial assistance to individuals and organizations pursuing activities in building engineering, design or technology.

SURE Program

The Summer Undergraduate Research Experience (SURE) at Columbia University was established to increase diversity in science and engineering by providing a unique summer research experience for students from historically underrepresented and minority backgrounds. This year our $15,000 donation sponsored Marylyn Carrillo, a first-generation Latina student at UCLA and second-generation immigrant, who studied how advanced traffic-mapping techniques can provide insight into the variables that determine which areas are crash-prone, laying the foundation for better traffic-safety strategies.

Delivering Clean Water

We donated $10,000 to nonprofit organization charity: water to fund household biosand filters to more than 400 people in Cambodia, where nearly five million people lack access to clean water. The easily maintained filters remove pathogens by filtering water through a biological film, coarse sand, fine sand and gravel.

In Cambodia, families build their own biosand filter and keep it at their home for daily use.

Courtesy Charity Water

BUILDING GREAT WORKPLACES Introduction

95% of our employees agree that Thornton Tomasetti is a great place to work.

We seek to create a welcoming and rewarding environment where employees can achieve their full potential throughout their careers, so we’re building a culture of respect in which individual differences and contributions are recognized and valued.

Our employees thrive best in an environment that is inclusive, equitable and diverse, with excellent benefits and wellness programs. And they value opportunities for mentorship and continuous learning that support all staff and cultivate future leaders.

In 2023, past and present leaders of our employee network group for women reflected on the importance, impact and accomplishments that Women@TT has had over the past 10 years. Click the title to watch the video.

Thornton Tomasetti

BUILDING GREAT WORKPLACES

Building Great Workplaces Progress Report

Each year, we report on several indicators that show progress toward achieving our goals for inclusion and diversity, professional growth and a lifestyle-friendly workplace.

Employees Receiving Promotions: Employees receive promotions for exemplary performance. For some employees, promotions are associated with stock ownership levels. This metric accounts for continuous employees only; interns transitioning to staff positions are not included.

Retention of Female Employees: Retention of female employees is one indicator of a viable pipeline for the advancement of women into senior leadership positions. Our retention rate remains high, at 88% for 2023. We are proud that our rate remained over 80% during the pandemic, when many companies experienced a much higher turnover rate for female employees.

Employees Who Are Women: The percentage of employees who are women is based on self-reported employee records. While this breakdown is in line with numbers typical of our sector see the NCSEA SE3 Survey ), we’ve enhanced recruitment efforts aimed at increasing the number of women in our firm, and continue to support employee network groups like Women@TT In 2023, we hired an Equity, Diversity and Inclusion (ED&I) officer.

U.S Employees Who Are People of Color: The percentage of employees who are people of color is based on self-reported employee records from our U.S. offices; we do not collect this data outside the U.S. Thornton Tomasetti is committed to a diverse workforce through enhanced recruitment efforts; by supporting Mosaic , an employee network group focused on multicultural issues; and by expanding our ED&I initiative.

U.S. Employees Who Are Women or People of Color:

The percent of employees in our U.S. offices who are women or people of color is based on self-reported employee records. More than half our U.S. employees are women or of nonwhite ethnicity or race, and we’re working to improve this percentage through the actions described above.

Women in Senior Leadership: This metric defines senior leadership as employees with the title of vice president or above. We’re working to expand opportunities for women in leadership positions by supporting them at pivotal stages in their careers, encouraging promotions into leadership positions and providing stock ownership opportunities. Since 2020, we have seen overall improvement in this area.

BUILDING GREAT WORKPLACES

Equity, Diversity & Inclusion

It’s been proven that diverse and inclusive organizations are creative, innovative and better to work for. That’s why we’re expanding on our long-established initiative to cement ED&I into our culture, policies and practices. Since 2016, our ED&I initiative has contributed to building an inclusive environment and increasing the firm’s gender, ethnic and racial diversity.

Challenges & Opportunities

The past year has seen the environment for ED&I (or DEI) become more challenging. Judicial rulings, legislation and a growing number of legal disputes are causing some companies and institutions to pull back on ED&I efforts. Yet it’s been proven that diverse and inclusive organizations are more creative, innovative and better to work for. That’s why we’re expanding on our long-established initiative to cement ED&I into our culture, policies and practices. We hired Vandana Juneja as the firm’s first ED&I officer in October 2023. Her mission? To strengthen our ED&I programs, track and accelerate progress, and advance our goal of becoming a place where all our people can bring their authentic selves to work.

Milestones

Happy 10th Birthday, Women@TT Founded in 2013 by then-Managing Principal Aine Brazil, Women@TT was our first employee network group (ENG). It was guided by the pursuit of gender equity and dedicated to promoting awareness, providing support, and driving firm culture. In the intervening decade, the ENG has chalked up a panoply of accomplishments, including establishing mentoring programs and leadership activities to support the advancement of women. It has grown to include 25 chapters and is now accessible to over 94% of employees.

Our ED&I team has also been facilitating inclusion dialogues across the firm, bringing colleagues together for learning and sharing of lived experiences and perspectives.

The Path Forward

In 2023, we enlisted Catalyst, a global consultancy focused on gender equity and workplace inclusion, to help us measure the success of our ED&I engagement to date. An all-staff survey, coupled with in-depth focus groups and interviews, provided insight into what we’re doing right – and where we need to do better. This data helped us define our priorities for 2024:

• Perform an ED&I Audit. Understand how our policies, programs and practices affect ED&I.

• Enrich Our ENG Community. Expand programming and engagement to deepen our sense of community.

• Elevate Our Learning Journey. Refresh on-demand resources, provide Leading Inclusively dialogues for all levels and regions, and expand training on understanding and mitigating unconscious bias.

• Enhance Inclusive Career Growth. Hold listening sessions globally to learn about and cultivate effective pathways to advancement for all.

• Foster Community Through Courageous Conversations. Create more opportunities for coming together to share our stories and lived experiences, communicate authentically and actively listen to one another.

• Map the Future. Build a plan for ED&I efforts to align with the firm’s next five-year (2025–2029) strategic plan.

MULTICULTURAL

LGBTQIA+

Network Group

ED&I Officer Vandana Juneja discusses programming with Peggy Phillips, board member. Thornton Tomasetti

We're bringing colleagues across the firm together for Leading Inclusively/Building Inclusion dialogues (recent New York group shown above). Thornton Tomasetti

BUILDING GREAT WORKPLACES Learning & Professional Growth

As a learning organization and incubator of talent and ideas, we encourage our employees to contribute to knowledge sharing throughout the firm. Anyone with an idea can propose the formation of a community of practice (CoP) Once established, a CoP can grow into a multipractice initiative that yields technical solutions, inspires news ways of thinking and creates positive shifts in our organizational culture.

During a structured reflection exercise at their annual summit, our 34 CoP leaders identified a variety of ways in which their groups’ activities help staff grow their technical, management, sales and leadership skills.

"In the exercise, each leader wrote down everything their CoP does that fits into each competency. Until they did that, most didn't realize they were supporting the continuous improvement and learning of the firm,” says Colin McLeod, director of knowledge and data.

We Challenge Our People to Grow

From their first day on the job, employees can begin learning by participating in programs like Thornton Tomasetti University, which in 2023 offered 20 seminars on a wide range of technical themes. And additional support is available at every step in their career journey. In 2023, 1,245 employees, across all job titles, were offered the opportunity to receive guidance through our mentor-matching program.

Many of our learning initiatives are designed to multiply and strengthen connections among our people, offices, practices and departments. This is one goal of our group coaching program, which had 125 participants in 2023. This year, it was expanded to target employees at the senior associate level, with 37 taking part for the first time. In addition to introducing members to professionals throughout the firm, it also focuses on helping each participant develop a strategy to guide them through the next step in their career.

“The coaching program is an excellent opportunity for senior associates to develop their business goals with colleagues and leaders within the firm,” says Huston Dawson, a senior principal in our Protective Design and Security practice “They can ask questions and hone their goals into a business strategy, which paves the way for their continued success.”

As employees progress in their careers, they may also benefit from our leadership development program. This year, 25 employees were in the first cohort of our updated program, which now includes personalized coaching and group training for leadership skills.

What Do CoPs Do?

A lot! In 2023, members of our Drones CoP gathered in Florida to demonstrate best practices for piloting uncrewed aerial vehicles (UAVs). To ensure that our operators provide consistent service regardless of location, they brought and flew company drones. Other groups – like our Performance-Based Seismic Design CoP, which hosts discussions with academic experts, and our Embodied Carbon CoP, which produces monthly “shorts” and a related podcast – educate members through open dialogue and regularly scheduled presentations.

CoP leaders from across the firm met in New York in September for their annual summit, a dynamic exchange of ideas, insights and strategies.

Thornton Tomasetti

Season 1 of the Here's How podcast explores how designers of buildings and communities can apply fresh thinking and best practices to reduce embodied carbon in the built environment.

BUILDING GREAT WORKPLACES

Our Workplace Culture

2023 was an exciting year for our workplace culture; it was the first in which more than 50% of all new hires were women, and 48% of new hires in the U.S. were nonwhite. These figures surpass the AEC industry averages of 36% and 31%, respectively, according to the Environmental Financial Consulting Group (EFCG) benchmarking survey. We also improved our already industry-leading employee-retention rate, lowering attrition for the third year in a row.

Our benefits program continues to evolve to promote diversity, with the goal of making our firm a great place to work, according to a variety of metrics. A valuable shift in our medical benefits took place this year: we switched from two benefit tiers – one for individuals and one for families – to providing options that cover all types of families, beyond the traditional nuclear structure.

We began offering expanded mental health programs through our health insurance provider, Cigna, including an additional year of membership in the mindfulness and meditation app Headspace. Our hearing-aid benefit, which previously only covered a one-time purchase, grew to allow one every two years. And after the U.S. Internal Revenue Service suspended its exclusion of bicycle-commuting reimbursements from employee income, we opted to sponsor the benefit and continue to help pay these expenses.

In 2023, 16 women and 42 men took advantage of our paid family-caregiver leave. And our reimbursement program for gym memberships and fitness classes was used by 289 U.S. employees.

Thornton

Employee Wellness

Our wellness offerings in 2023 ranged from financial-health seminars to our popular (with 41% participation) Wellness Challenge, a multiweek event in which offices compete against each other for prizes. Employees accessed Cigna’s diverse health resources and counted their steps using our group membership in the Walkingspree fitness app. In our large offices, wellness fairs featured health seminars and free massages, and healthy snacks were distributed in all our U.S. locations.

Of the 21 offices that received funds from our annual corporate responsibility grants program, 13 engaged in local wellness events. The program, which is now in its 11th year, allows offices to apply for a variety of locally appropriate activities. In 2023, these included structured fitness activities in our offices in Australia and India, as well as in wellness activities in our Houston office.

Cybersecurity

Employee peace of mind and job satisfaction are, to some degree, dependent on a workplace that is safeguarded against computer scams and cybersecurity attacks. In 2023, we expanded our cybersecurity awareness program for all staff by hiring a world-class training firm, supplementing it with internally developed content, offering an employee discount for password vault programs and establishing stringent criteria for secure computing in many of the countries where we operate.

2023

Twenty-nine offices participated in our 2023 Wellness Challenge. Points were awarded for activities like drinking enough water daily, bringing in homemade meals and taking a workday walk. The challenge also brought co-workers together for volunteering, group fitness activities and office lunches.

With 92% participation, Pune , India (pictured above), was the medium-large office winner, while Houston and Philadelphia tied to win in the small-office category, with over 80% participation.

This challenge promotes healthy workday habits by offering opportunities for wellness at work and office comradery. Alan Kanybek, a senior engineer in our Philadelphia office, says, “These activities not only revitalized us professionally, but also strengthened our bonds as colleagues. Wellness is no longer just a trend for us; it’s a commitment to a balanced work-life equation.”

Wellness Challenge

In March 2023, employees and friends of our Portland office participated in a “TT Takeover” of Black Mountain of Maine. More than 300 people came together for a day of outdoor winter activities.

Tomasetti

ESG DISCLOSURES

U.N. Sustainable Development Goals

Global Reporting Initiative Content Index

Environmental Policy (external link only)

Ethical Sourcing Policy (external link only)

Modern Slavery & Human Trafficking Statement (external link only)

Legal & Privacy Policies (external link only)

Thornton Tomasetti

United Nations Sustainable Development Goals

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Thornton Tomasetti contributes in a significant way to many of the United Nations’ Sustainable Development Goals. As a multipractice firm with more than 100 capabilities , we apply scientific and engineering principles across disciplines to solve the world’s challenges. Our impact stretches across many of the U.N.’s global goals. Ensure inclusive and equitable quality education and promote lifelong learning opportunities for all.

End poverty in all its forms, everywhere.

By contributing to the development of affordable housing projects, Thornton Tomasetti is working toward increasing access to basic services and property (Target 1.4). Additionally, our Thornton Tomasetti Gives Back program and the Thornton Tomasetti Foundation support nonprofit organizations like Bridges to Prosperity and invest in impoverished communities in under-resourced regions of the world. We also have a partnership with the American Red Cross in which the firm matches staff donations (Target 1.a) for disaster relief. Thornton Tomasetti has a Sustainability and Resilience practice that helps clients prepare, endure, adapt and thrive in a disruptive and changing world (Target 1.5).

Ensure healthy lives and promote well-being for all, at all ages.

We promote healthy living and well-being for our employees and the communities we serve through our work. Our employees receive excellent, affordable health insurance, annual fitness reimbursement, generous family leave for new parents, and free access to fitness, mindfulness and other wellness programs (Target 3.8). Our largest office, our New York headquarters, is certified through the WELL Health-Safety standard to ensure a safe work environment. Our team of sustainability experts has worked on more than 450 green building certification projects and helped clients realize their project certification goals toward standards like WELL, WELL Health-Safety, LEED, BREEAM and the Living Building Challenge, as well as others that seek to improve the health and well-being of building occupants – in projects as diverse as schools and airports.

This goal is woven into the fabric of Thornton Tomasetti. Founding Principal Charles Thornton launched the ACE Mentor Program of America (ACE) – a free after-school program designed to attract high school students into AEC careers –28 years ago. Around 70% of ACE mentees are minority students, and all of our sizable offices in cities where ACE chapters exist participate (Target 4.4). Our Chicago office is a founding contributor to the ADEPT program, pairing professional mentor-coaches with college students to advocate for aspiring Black and Brown engineers. Thornton Tomasetti, Inc., funds several scholarships for engineering students and offers regular internships, and the Thornton Tomasetti Foundation offers fellowships and scholarships for undergraduate students planning to pursue graduate studies in building engineering, design or technology (Target 4.b). Many of our professionals are educators at colleges and universities worldwide. Within our firm, we offer our employees discretionary tuition reimbursement toward a degree program or for relevant courses.

United Nations Sustainable Development Goals

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Achieve gender equality and empower all women and girls.

Thornton Tomasetti aspires to be an industry leader in fostering the professional advancement, success and visibility of women, not just at all levels of our firm, but also in the engineering field. A passion for gender equality and innovation through diversity drives our efforts to increase our number of female shareholders and employees, encourage women to become involved in company management, empower women through our Women@TT employee network group and encourage girls to enter STEM professions (Target 5.5). Our Equity, Diversity and Inclusion and Women@TT initiatives promote education of all employees regarding challenges faced by women as a gender underrepresented in our industry. These initiatives create opportunities to improve inclusion for women, foster a supportive community for women in our firm at all stages of their professional development, and help create a culture in which women are treated equitably and inclusively (Target 5.1). We support shared responsibility within the family by offering generous parental leave for both mothers and fathers (Target 5.4).

Ensure availability and sustainable management of water and sanitation for all.

Our sustainable design projects – to which we apply our expertise to meet a broad range of sustainability objectives – contribute to the goals of clean water and sanitation. We help our clients earn water efficiency and safety credits through the LEED, Living Building Challenge, and WELL certification programs (Target 6.4). Our projects reduce water use and take a holistic water budget approach, especially in places like California, where drought is common. Our Sustainability and Resilience practice incorporates green infrastructure and natural habitat regeneration in master-planning projects and green building certifications (Target 6.6). Our Sustainability and Resilience, Structural Engineering, Façade Engineering, and Restoration and Renewal practices all support water solutions, as they ensure our building and site level projects can handle dynamic water inputs and provide for effective stormwater management (Target 6.5).

Ensure access to affordable, reliable, sustainable and modern energy for all.

Thornton Tomasetti’s work in decarbonization supports the goal of achieving affordable and clean energy globally. We’re helping decarbonize the power sector and heavy industry by minimizing the risks associated with carbon capture and storage technologies, batteries and onshore and offshore energy facilities. We’re also advancing technologies for electrifying transportation systems (Target 7.a). Our engineers apply their expertise to solving the structural and functional challenges of alternative energy systems. Our sustainability experts guide clients to pursue embodied-carbon reduction electrification, energy efficiency and net-zeroenergy buildings (Target 7.3). We support the deployment of renewable energy by purchasing renewable energy certificates to cover the electricity use of all our offices in the United States (Target 7.2).

United Nations Sustainable Development Goals

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Promote sustained, inclusive and sustainable economic growth, full and productive employment and decent work for all.

Attention to diverse and nondiscriminatory recruitment and company policy means that Thornton Tomasetti contributes to the goal of decent work and economic growth opportunities for all. Our company standard practices and healthy work environment support our employees.

Our work on a variety of projects, across a range of sectors, contributes to economic growth (Target 8.1). Many of our projects serve as local economic hubs and foster community development opportunities. Through our R&D and innovation accelerators, we contribute new technologies to the building sector and beyond, and we support entrepreneurship through AEC Angels which funds technology start-ups (Target 8.2). We provide mentorship and scholarships to high school students through the ACE Mentorship Program, building a pipeline to the engineering and architecture professions (Target 8.6).

Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation.

Thornton Tomasetti’s innovation engine, CORE studio develops innovative and dynamic tools that improve efficiency and enable us to provide optimized client solutions. This positively impacts the quality of the infrastructure in the cities where we work. Every year, R&D funding is made available through CORE studio to employees, in an open call for innovation developments. Our services contribute directly to the industry, innovation and infrastructure goal. Our resilience consulting helps clients prepare, endure, adapt and thrive in a disruptive and changing world. In addition, we’re working with hospitals and transit to develop equitable and resilient infrastructure designs and we have numerous Institute for Sustainable Infrastructure-certified Envision Sustainability Professionals (Target 9.1). Our Applied Science practice engages in research, development and design to engineer practical solutions that manage risks across a range of military and civilian applications. One project is HyperloopTT , with the goal of creating the world’s fastest, most efficient and most affordable endto-end transportation solution (Target 9.4).

Reduce inequality within and among countries.

Thornton Tomasetti applies fair employment policies and equitable wages across our 40+ offices and in our work in more than 50 countries. The company assesses pay parity to ensure income equity (Target 10.4). Our Equity, Diversity and Inclusion initiative and antidiscrimination policies help ensure equal opportunities for all employees (Target 10.2). We promote involvement in our ED&I employee resource groups across locations as far-flung as Mumbai, India, and Washington, D.C. By sharing our technology and expertise across locations, we contribute to greater equality among countries. Our designs of buildings and communities can have a secondary effect of increased social equity. Our service work in Rwanda with Bridges to Prosperity helps reduce inequality for under-resourced and isolated communities (Target 10.3).

United Nations Sustainable Development Goals

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Make cities and human settlements inclusive, safe, resilient and sustainable.

Thornton Tomasetti provides consulting services in resilience and sustainability , which positively impact the goal of sustainable cities and communities. Our work in all our practice areas requires that we honor our oath as engineers to protect public safety in the communities we serve. We’re committed to constructing a cleaner, healthier built environment by measuring, tracking and eliminating embodied and operational carbon in buildings and neighborhoods. We collaborate with other firms to create high-performance, low-energy facilities and communities that are efficient, comfortable and healthful at every stage of their life cycles. Our broad range of sustainability services – from water balancing, green building certification, circular economy guidance and healthy materials research to parametric energy analysis – contributes every day to creating sustainable cities and communities. We also promote low embodied carbon in buildings through mass timber and strategic concrete design (Target 11.6). Our firm contributes widely to this goal through our work on affordable housing development (Target 11.1), transportation (Target 11.2), master planning and resilience (Target 11.3), building renewal (Target 11.4), community resilience and building forensics for natural disasters (Target 11.5).

Ensure sustainable consumption and production patterns.

We adopt sustainable practices and integrate sustainability information into our reporting and help others in our industry do the same. Per our environmental policy , we aim to apply our embodied-carbon specifications so that our projects use materials or adjustments to materials that are less carbon intensive than typical choices are (Target 12.6). Since buildings produce 40% of global CO 2 emissions, and about 11% of those are from building materials, our embodied-carbon action plan commits us to advocate for the use of low-embodied-carbon or carbon-storing materials within our sector and adjacent industries. As a member of the Structural Engineers 2050 Challenge , the Carbon Leadership Forum and other AEC groups, we work with others in our industry to advance embodied carbon reduction in structures. Another area of impact is the selection of healthy materials. We avoid the use of toxic materials on the Living Building Challenge Red List and endeavor to influence clients and partners to choose responsible material consumption and production (Target 12.7). We contribute to a circular economy through our master-planning projects, into which we incorporate circular economy principles (Targets 12.2, 12.5). Our work in carbon capture and storage reduces the release of greenhouse gases into the atmosphere (Target 12.4).

Take urgent action to combat climate change and its impacts.

With our new initiative, Climate Action at Thornton Tomasetti we’re structuring many of our practices around providing decarbonization and resilience solutions (Target 13.1). We’re combating climate change through our internal policies, projects and services, and advocacy and partnerships. We participate in committees focused on reducing emissions in our industry and sponsor organizations like the Carbon Leadership Forum We promote and apply creative means to reduce carbon in our projects and are committed to achieving carbon-neutral business operations and influencing policies and practices for sustainability and resilience in our industry and communities. We’re a recognized leader in moving consideration of embodied carbon to the forefront of our industry. We co-initiated the Structural Engineers 2050 Challenge , urging all structural engineers to understand, reduce and eliminate embodied carbon in their projects by 2050, and are an inaugural member of the Structural Engineers 2050 Commitment. We released a podcast series explaining methods for reducing embodied carbon in the built environment (Target 13.3). Our sustainable design, decarbonization and resilience services help clients combat climate change and its impacts (Targets 13.1, 13.3).

United Nations Sustainable Development Goals

(Page 5 of 5)

Conserve and sustainably use the oceans, seas and marine resources for sustainable development.

Our resilience professionals are working in coastal places to strengthen the resilience of infrastructure and communities against floods (14.2). Ocean acidification, caused by the ocean’s absorption of carbon dioxide from the atmosphere, is a problem for which we offer solutions through our climate action work (mentioned above). This includes our work in renewable energy, energy efficiency, netzero energy buildings, nuclear power, and carbon capture and storage (14.3), as well as our research and development focused on climate action.

Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss.

Master planning is an opportunity to maximize long-term sustainability and resilience. We help communities develop sustainable master plans, encouraging biodiversity and habitat regeneration. We also recommend green spaces to co-benefit stormwater management and heat mitigation. This enhances wildlife corridors and creates habitats that may not have existed in urban settings (Target 15.9). We recognize that mass-timber construction has great potential to reduce embodied carbon and that reducing carbon means sustainably managing forests. We’re the structural engineer for the world’s tallest mass-timber tower . As a leader in mass-timber design, we have an opportunity to impel wood suppliers toward more sustainable practices. Our structural engineering work includes green roof design. Green, vegetative roofs can provide unique habitats for biodiversity in urban settings (Targets 15.1, 15.2, 15.b).

GRI Content Index 2023

Using GRI 1: Foundation 2021

Thornton Tomasetti has reported the information cited in this GRI content index for the period January 1, 2023, through December 31, 2023, with reference to the GRI Standards.

ESG DISCLOSURES

GRI 2: General Disclosures

(Page 1 of 9)

2-1

2-2 Entities included in the organization’s sustainability reporting

2-3

Reporting period, frequency and contact point

2-4 Restatements of information

2-6

value chain and other business relationships

Nature of ownership: Private, employee-owned corporation

Headquarters: New York City

11 countries of operation: ThorntonTomasetti.com/Contact-Us

All subsidiaries and joint ventures associated with Thornton Tomasetti, Inc., are covered in the report.

Year 2023 annual reporting: January 1, 2023, through December 31, 2023

Publication date: July 1, 2024

Financial reporting: May 2023

Contact: Amy Hattan, Corporate Responsibility Officer, AHattan@ThorntonTomasetti.com

In 2024, we updated our emissions data spanning back to 2018 to reflect CO 2 e instead of just CO 2 emissions by including the emissions factors for N 2 O and CH 4 in our calculations. We updated the 2020, 2022 and 2023 commuting emissions to reflect round-trip mileage instead of one-way mileage. We updated our Edinburgh office's energy data to reflect all facilities on-site instead of just office space for both 2022 and 2023.

Activities: T horntonTomasetti.com/Capabilities

Sectors: Private; architecture, engineering and construction (AEC); building sector; consulting Markets: www.ThorntonTomasetti.com (Client Solutions)

Value chain:

• Upstream construction materials: computing supplies; office products, furniture and equipment; contracted labor and project subcontractors to supplement workforce

• Downstream (buildings and other structures, infrastructure, clients – contractual relationships)

• Operational supply chain: Leased buildings and vendors (IT, office supplies)

ESG DISCLOSURES

GRI 2: General Disclosures

2-7 Employees

Our data includes continuous staff. We did not include seasonal workers, interns, temporary staff or retirees in the data set unless specified. Full-time/part-time is defined by the respective country of work. Gender of employees is self-designated.

ESG DISCLOSURES

GRI 2: General Disclosures

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GRI 2: General Disclosures

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2-8 Workers who are not employees

2-9

Governance structure and composition

2-11 Chair of the highest governance body

We use consultants who work independently. All workers whose work is controlled by the firm are our employees.

Our highest governance body responsible for decision-making and overseeing the management of impacts is our board of directors. The board comprises 12 employees and one external member. All employees on the board hold executive positions in the firm. See our leadership page for roles and competencies of board members. For diversity of leadership, see disclosure 405-1.

Our governance structure is organized as a matrix, with regions, practices and departments reporting to the coCEOs, who report to the board. The co-CEOs manage the company, and the board assures that the company is effectively managed. Board members serve two-year terms, with no term limits. Every two years, membership is reviewed and put to shareholder vote at the annual meeting.

The corporate responsibility steering committee and the equity, diversity and inclusion committee are management committees responsible for working with the CEOs on decision-making for ESG impacts. The corporate responsibility department helps develop firm-wide goals and drive policy implementation.

Nomination and selection of board members are done at the election of the board and coordinated by the board chair. Both existing and new board members are evaluated on past performance. Ownership is one criterion for board membership but is not compulsory, as we allow for external members, who cannot hold stock.

The most senior individuals in the firm are the Co-CEOs, currently Peter DiMaggio and Michael Squarzini. The CoCEOs have the responsibility and the authority to run and manage the company effectively. The Co-CEOs report to the board of directors. The board of directors (under the guidance of the lead director Michael Squarzini) as a group is the highest governing body in the firm. The board acts as representatives of the owners, has oversight of the CEOs and is responsible for ensuring that the company is run and managed effectively.

2-10 Nomination and selection of the highest governance body

ESG DISCLOSURES

GRI 2: General Disclosures

(Page 5 of 9)

2-12 Role of the highest governance body in overseeing the management of impacts

2-13 Delegation of responsibility for managing impacts

The president and a board member are executive advocates of the equity, diversity and inclusion committee. They work with the employee network group leaders, as well as the equity, diversity & inclusion officer, to weave ED&I into our company culture.

See disclosure 2-12.

The corporate responsibility officer, reporting to one of the co-CEOs, is a senior member of the staff, responsible for managing some of the impacts. Corporate responsibility is woven into our culture at Thornton Tomasetti. Therefore, management responsibility is delegated to leaders in the areas most relevant to specific impacts. In addition to the corporate responsibility department, this includes our equity, diversity and inclusion committee; our human resources department; our legal department; our sustainability practice, etc. A regular weekly call between our department leaders and executive team enables regular reporting, as do lines of supervision between managers and the CEOs.

The highest governance body is responsible for reviewing and approving the reporting information. Reviews take place via regular weekly department leader/executive leader meetings and regular meetings between the coCEO and the corporate responsibility officer. The co-CEO approves a final review before the sustainability report is released.

The interests of all senior and executive leadership, the board and stakeholders are aligned around our purpose and values. This mitigates conflicts of interest, as the board is in agreement with the direction of our purpose and values. Our five-year plan is clear about the company’s direction during any five-year period, and the board ensures that we are aligned with the five-year plan and our purpose and values.

Our rules for employees regarding conflicts of interest state: "Do not engage in any activities that create or appear to create a conflict of interest. If you are unsure if a situation creates a conflict of interest, please consult your manager, the CHRO or the Legal Department."

2-14 Role of the highest governance body in sustainability reporting

2-15 Conflicts of interest

ESG DISCLOSURES

GRI 2: General Disclosures

(Page 6 of 9)

2-16 Communication of critical concerns

2-17 Collective knowledge of the highest governance body

2-18 Evaluation of the performance of the highest governance body

2-19 Remuneration Policies

2-20 Process to determine remuneration

The co-CEOs bring any critical operational concerns to the executive committee, and these concerns are discussed in this forum. Weekly meetings of the department leaders and executive committee also cover areas of critical concern. At the quarterly board meetings, concerns are discussed under the umbrella of strategy and vision. Then, messages about critical concerns are communicated to department leaders, practice leaders, regional leaders and employees via direct CEO town halls for their office locations.

The collective knowledge of the highest governance body on sustainable development is advanced through shared articles, invited speakers, internal seminars, conference attendance and involvement of individuals in industry associations.

Evaluation of our performance in sustainable development starts at the CEO level. The board evaluates how the co-CEOs are performing in the areas of the economy, the environment and people. This evaluation happens over time. Ultimately, the shareholders will inform the board if the evaluation is effective. Shareholders and other employees learn about our performance, as does the board, through several communication channels. Shareholders can voice disagreement or agreement with the company performance in sustainable development semiannually when selecting and reappointing board members.

Compensation decisions are conveyed through the matrix, from the top down. The board oversees CEO compensation, and the co-CEOs make compensation decisions for the firm.

Thornton Tomasetti adheres to a holistic compensation process consisting of elements of salaries, bonuses and equity. Our process is informed by firm performance, performance evaluations, project data and market conditions.

GRI 2: General Disclosures

ESG DISCLOSURES

GRI 2: General Disclosures

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2-23 Policy commitments

2-24 Embedding policy commitments

2-25 Processes to remediate negative impacts

See:

• Environmental Policies

• Ethical Sourcing Policy

• Modern Slavery & Human Trafficking Statement

• Legal and Privacy Policies

These policy commitments are approved by the executive committee and communicated via our website and employee handbook, and in our responses to requests for information.

Policy commitments are overseen by the department and practice leaders whose jurisdictions can have the greatest influence on the policy, with guidance and oversight from the executive committee. Staff in our departments and practices are rewarded in performance reviews, awards and bonuses and evaluated on how they embody the values outlined in our policies. Communication of our policies to our clients ensures compliance, as the results are seen in how we design our projects and how we deliver our services.

Thornton Tomasetti uses NAVEX Global, a confidential ethics-reporting hotline, to enable employees to report workplace grievances. This hotline can be accessed by all employees through our intranet on either a smartphone or computer. Employees also have the option to call the hotline directly to file a complaint. Our human resources business partners (HRBPs) are the only individuals with access to the account, and they monitor it regularly. Aside from the hotline, employees are encouraged to reach out to their local HRBP or the CHRO with any employee-relations issues. As with the hotline, once an issue is reported, the local HRBP or CHRO follows up with the employee to understand the issue in more detail and decide what next steps are needed. Once the issue has been resolved, the HRBP requests feedback on the process, which enables stakeholders to help improve the firm’s processes. Each employee-relations issue is logged into a spreadsheet, and the outcome is recorded (e.g., involuntary/voluntary termination, retained employee).

By tracking the outcomes and retention, the firm is able to assess whether the processes are effective.

GRI 2: General Disclosures

(Page 9 of 9)

2-26 Mechanisms for seeking advice and raising concerns

Employees who seek advice and raise concerns start with their supervisors or other matrix leaders. These concerns roll up to department leaders, the executive committee or the board. If employees are not comfortable speaking with their supervisors or other leaders, they can express their concerns through our confidential hotline, NAVEX Global. See disclosure 2-25.

2-27 Compliance with laws and regulations No instances of noncompliance in reporting period. 2-28 Membership associations

The membership associations in which we have significant (highest spend and most engagement on committees) involvement include the American Institute of Architects, the ACE Mentor Program of America, Beverly Willis Architecture Foundation, Urban Green Council, Structural Engineers Association of New York, Chicago Architecture Center, Council on Tall Buildings and Urban Habitat, American Council of Engineering Companies and the New York Building Congress.

Our significant stakeholders are clients, business partners, employees, governments, industry associations, shareholders, suppliers, and underrepresented groups. We engage with stakeholders to identify materiality areas for our sector, to identify areas of concern and reduce negative impacts, and to involve our stakeholders in the solutions. We work as a team with our stakeholders and seek inclusion for our employees in decision-making. 2-30

GRI 201: Economic Performance

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201-1 Direct economic value generated and distributed

See Financial Progress Report .

We do not engage in profit distribution to shareholders. We are a private company and do not publish profit or operational costs.

201-2 Financial implications and other risks and opportunities due to climate change The risks and opportunities posed by climate change that have the potential to generate substantive changes in our operations, revenue or expenditure include physical risks such as extreme weather, shortages of materials and health pandemics that impact our employees; new competition from a change in demand for particular services and new technologies; and civil unrest that can result in uncertain markets in our locations.

After our New York headquarters weathered Superstorm Sandy, we developed a business-continuity plan to reduce risk from extreme weather.

As an engineering-services firm that provides sustainable-design services, we have an opportunity to be competitive and to quickly respond to changes in demand for sustainability services as more climate-change policies and codes demand sustainable design and as more clients seek to achieve net-zero carbon in their projects.

We have an excellent opportunity to apply our expertise and capacities to solve climate-change problems. We are expanding our climate-action service areas in decarbonization and resilience and applying to these services our expertise in sustainable design, mass-timber structures, embodied carbon, carbon capture and storage, renewables and batteries, manufacturing, transportation systems and resilience. We're also developing new technologies that can be used toward reducing greenhouse-gas emissions and improving resilience against climate-change impacts.

Government policies and programs that seek to regulate emissions from businesses are less likely to impact Thornton Tomasetti, a private company, than large public companies. We set our goal of reaching carbon-neutral business operations by 2030 – informed by the Greenhouse Gas Protocol – before many private companies did, and we're on target to achieve it. Thornton Tomasetti is a member of the Science-Based Targets initiative (SBTi) and is setting near-term science-based emission-reduction targets.

GRI 201: Economic Performance

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201-3 Defined benefit plan obligations and other retirement plans

201-4 Financial assistance received from government

Thornton Tomasetti offers a defined contribution plan. U.S. employees may select a pretax contribution percentage, subject to the annual limit set by the U.S. IRS. The firm makes a matching contribution of 50% to the first 7% of employee contributions, not to exceed the maximum current-year tax-deferred limit.

N/A. Thornton Tomasetti did not receive financial assistance from government in the reporting period.

ESG DISCLOSURES

GRI 302: Energy

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302-1 Energy consumption within the organization

See Sustainable Operations Progress Report .

Electricity consumption: 11,051,253 megajoules

Total heating consumption: 4,859,965 megajoules

Natural gas heating: 3,344,250 megajoules

Steam: 1,515,715 megajoules

Total energy consumption (purchased) within the organization: 15,911,219 megajoules

Total renewable energy purchased: 8,792,159 megajoules

Total nonrenewable energy consumption (purchased) within the organization: 7,119,059 megajoules

302-2 Energy consumption outside of the organization

302-3 Energy intensity

Energy intensity ratio:

15,911,219/1,552 megajoules (9,332 GJ) per employee

Organization-specific metric:

1,552 employees counted in 2023 emissions analysis

Energy included:

Fuel and electricity consumed within the organization

ESG DISCLOSURES

GRI 302: Energy

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302-4 Reduction of energy consumption

302-5

Reduction of energy consumption in our operations is measurable where we have direct control in our leased office spaces. We can measure gains in energy efficiency from our green office fit-outs by comparing our green building design standards to average energy use intensity. We can also measure gains in efficiency from changes in equipment or technology.

Fourteen of our offices have been fitted out to a green building standard equivalent to that of LEED, as outlined in our office fit-out best practices policy. The energy-use reduction in lighting power intensity from a LEED Commercial Interiors project is an average of 20%. In 2023, our San Francisco, Newark and Boston offices moved into energy-efficient spaces.

Our corporate responsibility grant program provides support to offices implementing energy-reduction measures. In 2023, out of the 21 grants awarded to offices for corporate responsibility initiatives, two were slated specifically for office energy-use reduction.

Our Key3 initiative directs offices to reduce energy use in three key areas, which include installing energyefficient lighting, purchasing energy-efficient appliances and reducing plug loads.

See Our Projects Progress Charts.

Our sustainable design services contribute significantly to reductions in the operational and embodied energy requirements of buildings. Our consulting and design services assist clients in meeting project goals for energy efficiency; net-zero energy design; Passive House; life-cycle assessment and embodied-carbon reduction; and LEED and other green building certifications. The measurable impacts come from in-house energy models and comparisons to average building energy-use intensities.

Our growing services in decarbonization include further reducing the energy requirements of the building projects on which we consult, and we’re helping our clients in the energy sector develop non-fossil-fuel energy supplies. In addition, we’re working on reducing the energy requirements for transportation.

Reductions in energy requirements of products and services

ESG DISCLOSURES

GRI 305: Emissions

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305-1

305-2

We have no owned facilities and few owned vehicles. Scope 1 emissions are negligable and not included in the emissions inventory.

Gross location based Scope 2 emissions: 1,380.61 MT CO 2 e

Gross market-based Scope 2 emissions: 529.05 MT CO 2 e

Gases included in calculation: CO 2 , CH 4 , and N 2 O

Base year for the calculation, including the rationale for choosing it, emissions in the base year, context for any significant changes that triggered recalcs: 2018

Source of the emission factors and the global warming potential (GWP) rates used: EPA, DEFRA, and other national electricity emissions factors

Consolidation approach for emissions; whether equity share, financial control, or operational control: Financial Control

Standards, methodologies, assumptions, and/or calculation tools used: We collect and calculate emissions in line with the GHG protocol.

• Landfill Emissions

• Business Travel

• Commuting Emissions

Gases included in calculation CO 2 CH 4 and N 2 O

GHG emissions ratio: 2.05

Organization specific metric: Number of full-time employees in inventoried offices

Scope 1 and 2 Emissions ratio: 0.34

Scope 3 Emissions ratio: 1.71 MT CO 2 e

Gases included in calculation: CO 2 , CH 4 , and N 2 O

ESG DISCLOSURES

GRI 305: Emissions

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305-5 Reduction of GHG emissions

GHG emissions reduced as a direct result of reduction initiatives: 1,726.39 MT CO 2 e

Gases included in calculation: CO 2 , CH 4 , and N 2 O

Base year for the calculation: 2018

Scopes where emissions reductions took place: Scope 2 and 3

305-6 Emissions of ozone-depleting substances (ODS) N/A. We do not track, as we are a service company.

305-7 Nitrogen oxides (NOx), sulfur oxides (SOx), and other significant air emissions N/A. We do not track, as we are a service company.

ESG DISCLOSURES

GRI 401: Employment

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ESG DISCLOSURES

GRI 401: Employment

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ESG DISCLOSURES

GRI 401: Employment

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401-2 Benefits provided to full-time employees that are not provided to temporary or part-time employees

Full- and part-time U.S. employees regularly working a minimum of 30 hours per week are eligible for the Thornton Tomasetti benefits plans below. Other countries have similar offerings and differ based on local law and benefit norms.

• Cigna medical plans (employer/employee paid)

• High medical OAP

• Low medical OAP

• High deductible health plan with health savings account

• Cigna dental plan (employer/employee paid)

• Dental PPO

• EyeMed vision insurance (employer paid)

• Provides eye exams and offers discounts on lenses, frames and contacts

• Life insurance (employer paid)

• Basic life and AD&D insurance for $100,000

• Voluntary life (employee paid)

• Employees may purchase life insurance for employee or spouse/domestic partner

• Short-term disability (employer paid)

• Provides partial replacement income due to disability, up to a maximum of 26 weeks

• Long-term disability (employer paid)

• Provides partial replacement income in case of disability from 90 days to age 65 years.

• Employee assistance program (employer paid)

• This confidential program assists employees and their dependents with personal problems and/or workrelated problems that may impact their job performance, health, or mental and emotional well-being.

• Offers other services and information on elder care, pet care, financial, emotional health, physical health, job/career, relationship, family life, legal, and substance use.

• Flexible savings pretax accounts (employee paid)

• FSA healthcare

• FSA dependent care

• Limited purchase FSA

• Fitness program (employer paid)

• Fitness reimbursement up to $400 paid in a 12-month period

• Bicycle program (employer paid)

• Bicycle reimbursement up to $240 per year

• Commuter pretax benefits (employee paid)

• Parking

• Transit

ESG DISCLOSURES

GRI 401: Employment

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401-2 Benefits provided to full-time employees that are not provided to temporary or part-time employees (cont.)

• Health savings account (employer/employee contribution)

• HSA available for employee enrolled in the high deductible health plan

• Receives employer new hire and annual contributions

• Employee may contribute to HSA

• Contributions are based on annual IRS limits

• Raymond James (employer paid)

• Offers one-on-one financial advice to improve employees’ financial health and provides a monthly series of webinars covering financial planning topics.

• 401(k) profit sharing plan (employer match/employee contribution)

• Retirement savings plan that allows employees to save and invest a portion of their earnings on a pretax basis.

• 50% match, up to 7% employee contribution

• 401(k) student loan matching program (employer match)

• Enables employees who are repaying a student loan to save for retirement while continuing to pay down their student loan(s).

• Cigna programs, wellness tools and applications (employer paid)

• Voluntary programs (employee paid)

• Critical care insurance

• Hospital care insurance

• Accidental injury insurance

• Wellness apps (employer paid)

• Walkingspree

• International business travel

• Medical benefits abroad

• Employee overseas emergency care

ESG DISCLOSURES

GRI 404: Training & Education

401-3 Parental leave

Continuing full- or part-time employees with a minimum of one year of service at Thornton Tomasetti who have become disabled due to pregnancy are eligible to receive full salary under the Parental Family Caregiver Leave benefit, based on years of service. Part-time employees’ leave days are in proportion to the average number of hours worked in the year preceding the beginning of leave. Paid family leave begins with the birth of the baby and is paid based on years of service.

Maternity leave: At least one year of service, 40 days

At least three years of service, 45 days

At least four years of service, 50 days

Number who took parental leave: 16 women and 42 men

Number who returned to work after leave and were still employed 12 months after return: 11 women and 20 men

Return-to-work rates of employees who took parental leave: 68.75% women and 47.62% men

Retention rates of employees who took parental leave: 87.50% women and 95.24% men

3,233 by females

6,328 by males

26 nonbinary/not listed

Performance alignments are optional for part-time staff (less than 30 hours). 100% completion of performance alignments (both male and female).

GRI 405: Diversity & Equal Opportunity

405-1 Diversity of governance bodies and employees

Percentage of Individuals Within Executive Committee and Board Governance Bodies by Gender

Number of Individuals Within Executive Committee and Board Governance Bodies by Age Group

405-2 Ratio of basic salary and remuneration of women to men

We're not including a ratio of basic salary and remuneration of women to men in this report. We have a pay parity report that we publish internally every year, based on specific technical job categories, but our categories do not currently match those of GRI.

GRI 406: Nondiscrimination

406-1 Incidents of discrimination and corrective actions taken

Our policies dictate that we respect the privacy and confidentiality of these sensitive matters, so numbers and details are omitted.

Company-Specific Materiality Topic: Community Engagement

TTCE-1

TTCE-2

ESG DISCLOSURES

Company-Specific Materiality Topic: Employee Health & Wellness

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