25 MWs thru solar
Millions of gallons
100% solar powered
HQ & yard
LEED & SWPPP
As general contractors, our actions and decisions have a big impact on both our local community and the environment. We are committed to integrating sustainability practices into our everyday operations, material sourcing, design approaches, and construction techniques.
Recommending lower carbon building materials
We work with our engineers and suppliers to optimize concrete mix designs to contain higher percentages of low carbon admixtures in lieu of cement. We can often achieve 30% reduction in concrete carbon emissions on a project by optimizing the specified concrete. Since concrete related activities make up 55% of our work volume, these savings can add up.
Fly ash, slag and other admixtures, known as Supplementary Cementitious Materials (SCMs) can replace some of the Portland cement in concrete without affecting cost, strength or durability. These admixtures are byproducts of industrial processing. Slag happens when iron ore is melted and fly ash, a rough textured particle, is a remnant of burning coal. Using these byproducts in concrete provides circular benefits for industrial processes while at the same time lowering the embodied carbon in concrete. Emerging bio-based technology, such as kelp admixtures, are promising.
Low carbon concrete is suitable for foundations, slabs, pavements, and wall applications. Even tilt-up wall panels can be constructed with low carbon concrete mix designs. There is no material cost increase to use low carbon concrete, but cure times usually increase, so schedule needs to be carefully considered.
The only application not suitable for SMCs is pervious concrete, such as site paving that needs to allow rain to permeate into ground waters.
Finding structural approaches to reduce carbon
The most significant scope for reduction in building mass is often found in structural design.
- For example, Overaa works closely with our structural design partners on certain projects to reduce slab or beam span (and increase associated column density) which can yield carbon savings.
- Alternatively, we recommend emerging technologies such as mass timber in lieu of concrete or steel structural members to achieve significant carbon savings.
Finding construction efficiencies
- Prefabrication can decrease waste and improve schedules, but must be carefully weighed against transportation costs.
- Centralization of various tasks, such as preassembling wall components in an controlled environment, can streamline operations and reduce waste.
Aggressive material waste management
- Reducing material waste with thoughtful, site specific landfill diversion programs.
- Increasing material reuse by purchasing materials, such as concrete forming materials, that can be reused for several applications.
For every project, our goal is to decrease embodied carbon emissions through strategic material selections and construction processes. Embodied carbon is the amount of carbon emitted into the environment from a building during its entire lifecycle: manufacturing, installation, construction, maintenance, and demolition. (Embodied carbon is different from Operational Carbon, which measures building energy consumption.) When choosing various construction materials, we consider its lifespan, including extraction, transportation, construction and disposal.
During our collaborative preconstruction sessions, we analyze design and construction approaches and offer carbon reduction strategies. We have found that the most significant opportunity for carbon reduction lies in the structural design – specifically the type of concrete we use and the approach to framing. On past projects, our deep understanding of the nuances of these building materials and methods has enabled our clients and design teams to make informed decisions, and has resulted in substantial carbon savings.
During the construction phase, we focus on reducing material waste, finding efficiencies and opportunities for re-use, and sourcing clean energy for operations.
Measuring and understanding the carbon impact of construction is an important step towards carbon neutral construction. Our Environmental Strategy is aimed at assessing our actions via quantifiable metrics, within the following categories:
- Carbon Emissions
- Material Waste Management
- Water Management
- Community Impact
- Project Selections
Net Zero Certification
Goal 1 | Carbon Emissions
Establish a corporate carbon commitment and metrics.
- Integrate Embodied Carbon Calculator (EC3) and make informed procurement selections based on low carbon emissions.
- Collect Environmental Product Declarations (EPD) for materials used which include a cradle-to-gate Life Cycle Assessment (LCA).
- Partner with suppliers to increase cement replacement alternatives in concrete mixes, and partner with designers to provide lower carbon building alternatives such as mass timber.
- Increase usage of solar power or other renewable energy sources, such as green powered generators at jobsites, prefabrication sites, and offices.
Goal 2 | Material Waste Management
Restructure Waste Management approach for optimized landfill diversion and transparency.
- Reduce total waste generated on jobsites.
- Increase usage of reusable formwork.
- Aggregate forming operations in centralized locations to facilitate reuse.
- Invest in reusable aluminum and steel formwork.
- Increase centralized and prefabrication operations where viable.
- Increase number of projects certified with TRUE Zero Waste program. (Certified projects divert 90% from landfill.)
- Utilize Recycling Certification Institute (RCI) facilities for mixed construction and demolition.
Goal 3 | Water Management
Reduce virtual water consumption (water consumed during construction projects.)
- Increase usage of rainwater harvesting, greywater recycling systems.
- Use water metering through smart irrigation systems, pressure-reducing valves.
- Use water-efficient toilets.
- Decrease usage of plastic single use drinking water bottles on construction sites.
Goal 4 | Transportation
Decarbonize corporate transportation, travel, and equipment.
- Commit to sourcing regional materials within 100 miles of project site.
- Decrease diesel and gas powered vehicles and equipment in corporate fleet. Increase fleet of electric, hybrid, biofuel, and hydrogen-powered trucks, passenger vehicles, and heavy equipment.
- Encourage telecommuting options where appropriate.
- Increase public transportation benefits for employees.
- Increase number of carpool vans and increase carpooling benefits for employees.
Goal 5 | Community Impact
Expand collaboration, training, and participation of Green Team.
- Increase participation and engagement in LEED (Leadership in Energy and Environmental Design) and SWPPP (Stormwater Pollution Prevention Plan) training.
- Commit to learning and understanding emerging sustainability policies and practices – so that we can help our clients make informed decisions. Some of the San Francisco and California State Climate change policies include:
- Design for All Electric Building Act.
- Buy Clean California Act (BCCA) Meet targets for GWP (Global Warming Potential) for Structural Steel, Rebar, Flat Glass, Board Insulation.
- Architecture 2030 Challenge Reduce embodied carbon emissions from all new buildings, infrastructure, and associated materials by 65% by 2030 and zero by 2040.
- SB 100 100% Clean Energy Act: California to be powered by carbon-free electricity by 2045.
Goal 6 | Project Selection
Seek projects that help the environment and align with partners that share our values.
- Pursue local projects near our workforce.
- Seek out water purification, water recycling, material recycling, and green energy generation projects such as solar, cogeneration, hydrogen, and biofuel.
- Seek out LEED projects, ParkSmart projects, and other certified green building projects.
How we're doing
Using low carbon concrete
Overaa helps recommend concrete mix designs for various applications to decrease the embodied carbon in our projects.
Reducing embodied carbon in concrete
Case Study: Optimizing concrete mix designs.
Concrete is typically the biggest source of embodied carbon in our projects. Embodied carbon measurements take into account the entire lifespan of the material including its extraction, transportation, construction and disposal.
Overaa buys approximately 75,000 cubic yards of concrete annually. By proactively optimizing our concrete mix designs, we can make a significant impact on the project’s carbon footprint. Working with the structural engineer and our concrete suppliers, we customize mix designs for each application – flatwork, structural elements, architectural features, etc. Admixtures including fly ash, slag, and calcined clays in lieu of cement help reduce the amount of embodied carbon in the concrete.
We track our annual concrete usage so we can work toward reducing our overall carbon footprint and global warming potential (GWP).
Overaa invests in equipment and material that can be reused multiple times, such as these Cunningham beams that are used in horizontal deck forming applications. They are collapsible for transport and storage.
Choosing materials that promote reuse and decrease emissions
Case Study: Finding efficiencies in forming operations
Concrete related activities represent 55% of our work volume, so a primary focus is on material, equipment and processes used in concrete forming operations. Overaa buys approximately 132,000 board feet of milled lumber and 195,000 board feet of forming plywood annually. That’s a lot of raw natural resources. Most of the wood is cut and assembled into forming panels at Overaa’s fabrication yard in Richmond then dispatched to various jobsites. By centralizing prefabrication, we create less waste. Additionally, we invest in materials that can be reused in forming operations, such as steel beams or aluminum panels.
Many of our projects involve water purification, material recycling, and green energy generation, such as the Miners Ranch Water Treatment Plant Improvement project, a progressive design build project that expanded plant capacity from 14 to 21 million gallons per day of clean water to serve approximately 6,700 households in Butte County.
Choosing projects and partners that align with our values
Case Study: Choosing projects that support the environmental initiatives
Overaa actively pursues projects that include water purification, water recycling, material recycling, and green energy generation such as solar, cogeneration, and biofuel.
In 2009, Overaa invested in people and equipment to increase our ability to compete in the water resource and municipal infrastructure market. Today, more than half of our volume of work involves water resource management, material resource management, and renewable energy. We have been named one of the Top Environmental Firms in the nation three years in a row by Engineering News Record (ENR).
Additionally, we seek out LEED projects, Net Zero projects, ParkSmart projects, and other certified green building projects. We built the world’s first rotating laboratory, The FLEXLab at Lawrence Berkeley National Laboratory to support research in building system efficiency such as building envelopes, windows, and ventilation, and energy control systems.
We recently built the largest commercial kitchen in Northern California, the Central Commissary, for Oakland Unified School District. That project was named a Top Environmental Project Merit Award by ENR in 2021. The project uses 35% less electricity than comparable structures thanks to extensive daylighting, carbon dioxide-based refrigeration, waste heat recapture system, and full building systems integration.
100% SOLAR Headquarters
Since 2016, Overaa has invested in renewable energy to power operations.
100% Solar Powered, Centralized Operations
Case Study: Going green
Our Richmond headquarters – including our prefabrication yard and shop – is 100% solar powered.
In 2016, we added our first solar array to our rooftop and in 2018, we added an additional 5,852 SF carport structure equipped with solar panels. Together, the system produces approximately 194,151 KW per year of energy, enough to power our offices, shop, and prefabrication yard most days of the year. On days that this is not enough, we source our supplemental energy from MCE Solar One, a 10.5 megawatt solar farm that Overaa helped design-build in 2018.
The energy generated from Overaa’s solar system is equivalent to 137 metric tons of carbon dioxide emissions avoided. This is equal to 23.9 homes’ electricity use in one year, removing 29.1 passenger vehicles from the road each year, or the carbon sequestered by 162 acres of US forest in one year.
Prefabrication, centralized operations, and a robust waste management program help us reuse and recycle building materials.
Choosing methods that promote reuse, decrease waste, and lower emissions
Case Study: Finding efficiencies in centralized forming operations and prefabrication
- Our centralized prefabrication location lets us save wood remnants for other applications and utilize 95% of the original purchased material.
- We use aluminum and steel forms that can be reused up to 250 times wherever possible.
- We invest in laminated veneered lumber (LVL) which uses the remnants of milled lumber and dismantle prefabricated wood “I” joists to reuse the components in other forming material.
- We replace high strength steel, re-useable wall forming ties in 85% of our wall forming applications, thereby replacing one-time use steel snap ties with plastic cones.
- Recycled plastic nailers are used in place of wood nailers in aluminum joists.
- We encourage the use of recycled Class II aggregate subbase in 92% of our subgrade preparation work.
Most of our clients are interested in investigating methods and materials that can lower the impact of construction on natural resources and carbon emissions. Our in house team provides thoughtful analysis and options.
Certified Green Building Specialists
Case Study: Education, training and engagement in the newest approaches to sustainability
Overaa LEED certified professionals get involved with design teams early in the development phase to help analyze materials and methods and to incorporate concepts to achieve LEED accreditation. From our knowledge base, we provide critical value analysis for project teams to make strategic decisions during the project development.
We also have Stormwater Pollution Prevention Plan (SWPPP) certified staff, ready to help you implement and maintain your project’s SWPPP that was developed during design. Our comprehensive SWPPP services cover: regulatory compliance and compatibility and feasibility for both construction as well as industrial general permits.
In addition to LEED, our team uses benchmark systems to validate sustainable design approach for our projects including Living Building Challenge, ParkSmart, CHPS, Labs 21, SITES, Well Building Standard, Buy Clean California Act, Architecture 2030, SB 100 etc.
How does Overaa recycle plywood and lumber?
How does Overaa recycle concrete, steel and asphalt?