Why Water is a Valuable Resource for the New Walmart Home Office Campus

The master plan for the Walmart Home Office campus in Bentonville, Arkansas, was developed with a strong focus on sustainability and responsible water management. Embracing the concept of Big Nature—the idea that every landscape we inhabit, whether we develop large or small, is part of a larger ecological system—the Walmart campus civil engineering design actively implements stormwater management and treatment processes to mimic predevelopment conditions and minimize the impact to the environment.

To meet Walmart’s sustainability goals, the Big Nature plan was developed to celebrate the region’s natural beauty while fostering mental and physical well-being. This plan incorporates green spaces, courtyards, trails, over 13 acres of lake reservoirs, and regionally sourced plants.

Additionally, these goals of a comprehensive sustainable stormwater treatment train were implemented and spearheaded by Walter P Moore, which served as the civil engineer of record for the Walmart Home Office campus. This treatment train includes bioswales, rain gardens, the Razorback Greenway Trail—an open vegetated waterway traversing the campus—and the North and South wet-bottom lakes. Together, these features efficiently manage stormwater, filter pollutants, provide non-potable water supply, and improve water quality before it is discharged to the public waterways that include the Town Branch Creek and Osage Creek.

LID, an engineering and land planning approach to manage stormwater runoff onsite to minimize the impact on water quality, played a key role in the campus design. LID included the integration of bioswales along major roadways and conveyance paths that proves effective in attenuating stormwater runoff and reducing infrastructure costs across the campus. By providing storage, attenuating peak flows, and treating developed flows locally before entering the storm sewer system, the bioswales serve as a natural pretreatment mechanism while enhancing water quality and contributing to a more sustainable campus-wide stormwater water management strategy.

The stormwater collection systems on campus convey and discharge pretreated stormwater runoff to the central Razorback Greenway Trail vegetated waterway. The Razorback Greenway Trail was planned not only as a feature to the hike and bike extension of the Razorback Trail—connecting Town Branch Creek to Osage Park—but also to serve as the backbone of the campus stormwater conveyance and water quality treatment systems. The Razorback Greenway Trail allows for the connection of multiple stormwater treatments designed to activate, aerate, polish, and deliver naturally treated and clean stormwater that is free of sediment, excess nutrients, contaminants, and debris to the campus lakes and public streams that serve the outfalls from the lakes.

Organizing and connecting stormwater treatment to create the water treatment train upstream of the campus lakes allows for the critical reduction of costly and maintenance-intensive infrastructure, such as lake aeration, chemical and biological controls to regulate algae blooms, and dredging. Two lakes on the Walmart campus are specifically engineered to temporarily store and manage the stormwater. The lakes’ design allows for the controlled release of developed flow from the campus, prevents downstream flooding, and minimizes the impact from the developed campus on natural waterways such as Town Branch Creek and Osage Creek. The campus lakes serve as the final water treatment in the campus stormwater treatment train for stormwater runoff as the wet bottoms and wetland planting filter any water released into Town Branch Creek and Osage Creek.

A major component of the master plan for the Walmart Home Office campus was the clear understanding of the importance of water as a resource. The need for planning and engineering for the most effective use of the water resources on the campus was an overarching goal. The identification of water resources to serve the campus, evaluation of risk from the extremes of too much or too little water, and planning for management of the water resources on campus provided the framework for understanding the cycle of water. Additionally, the identification of water resources provides mutually beneficial solutions for the campus, community, and environment. Understanding site specific water supply sources, demands, and stresses from the development and the community was the foundation in engineering a more sustainable campus.

Water mapping and water balance analyses for Walmart’s original home office site was used to identify feasible options for on-site water collection, storage, and reuse as well as provide the critical information needed to design for LID and resiliency on the new campus. Ultimately, the water balance efforts for the new campus incorporate multiple uses of campus water resources into mapping software that was used to design and engineer the sustainable campus infrastructure.

Because of the water infrastructure design on campus, water supply demands can be diverted to non-potable sources, which will help reduce water supply costs. Additionally, using captured water from rainfall and condensate to supply irrigation and other low contact maintenance applications, the campus conserves potable water for more critical uses such as drinking water, food preparation, wellness facilities, hospitality services, and conference centers—ensuring high-quality water is available where it is most needed. 

To ensure the campus water supply was distributed accordingly, Walter P Moore developed flow diagrams to map the interdependency between water sources and campus water demand. These diagrams provided the framework for calculations used to determine the required storage capacity and to strategically position processes within the water supply chain. Furthermore, scenario development for the campus helped to determine the best fit for the planned campus, taking into consideration land use, recreation, operational needs, and costs.

Additionally, water resource protection measures were designed and engineered, including a progressive stormwater management train that transitions from small, distributed features to large, centralized features before leaving the campus. The campus accepts and treats stormwater from nearby neighborhoods, and stormwater detention is centralized in either of the two lakes upstream of each outfall. Discharge outfalls during extreme rain events are thereby reduced, leading to improved downstream drainage conditions.

A non-potable water supply distribution system captures stormwater runoff and building condensate through storm sewers and swales. The network delivers untreated water reuse volume from the lakes into a pressurized distribution system for irrigation and maintenance water, reducing reliance on the City of Bentonville’s municipal supply and enhancing water resiliency.

Water balance and mapping played a crucial role in designing the campus lakes, providing valuable insight into water sources and uses to optimize the design for effective water management.

The master plan prioritizes resource management strategies, including the integration of a weather-actuated gate known as the OPTISystem installed in the South Lake to optimize water harvesting, reuse, and active detention storage. The intelligent gate system enhances efficiency in real time by dynamically adjusting water levers, ensuring an overlap between storage, water release to the public, and campus reuse functions. 

By facilitating pre-storm peak releases, the gate discharges only the necessary volume to meet storage requirements for incoming storm events. This proactive approach mitigates downstream flooding impacts, improves stormwater management for existing developments, and enhances overall hydrologic resilience.

To ensure efficient maintenance, the bioswales and pass-through planters were designed for minimal landscaping requirements. Additionally, strategic planting around the lakes minimizes debris entry, contributing to the overall sustainability efforts.

Overall, the Walmart Home Office campus master plan presented a comprehensive approach to sustainable water management, ensuring environmental responsibility, and water resiliency for the Walmart.