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Rainwater Harvesting - Two Case Studies

Capturing Stormwater for Reuse

by Pacheco Koch

Rainwater Harvesting - Two Case Studies

One of the most extensive rainwater harvesting systems in the U.S. is operated at the Toyota Motor North American headquarters in Plano, Texas. It includes 40 aboveground, corrugated steel tanks with a total capacity of 320,000 gallons and four irrigation pump stations with integrated controls to feed the irrigation system at this 100-acre site. Collecting rainwater from the property's parking garages was the main goal of the system designed by landscape architecture firm Pacheco Koch.

Case Study 1
Located in Plano, Texas, the Toyota Motor North America Headquarters is home to one of the nation's largest capacity rainwater harvesting systems. The 320,000-gallon rainwater harvesting system was completed with teamwork between the designer Pacheco Koch, the general contractor Austin Commercial, and the installer inCon-trol Construction. The intent of the rainwater harvesting system included capturing parking garage roof runoff during rain storm events. The intent of the team was to provide sole source integration of the entire system including water storage, pumps, and controls for an irrigation system for 100 acres.

The rainwater storage system consists of a total of forty aboveground corrugated steel tanks split between four parking garages. The water harvesting system also includes four irrigation pump stations with integrated controls manufactured by the installer. Initial design considerations included whether to use multiple corrugated steel tanks, below ground fiberglass tanks or cast-in-place concrete tanks at each garage. In the end, the corrugated steel tanks became the final design option.

Drains on the top level of the garage are routed into each of the ten corrugated tanks per garage. The tanks in each garage structure are plumbed together via 12" communication plumbing to essentially create one large storage vessel. At one end of the tank series, the irrigation pump station draws water and charges the irrigation mainline.

A pressure monitoring level sensor at each tank series is used to not only decide which tank series to irrigate from, but to also call for domestic fill water to keep the irrigation system operational if the tanks are empty. The pump stations are pressure activated and require no communication to the site's multiple irrigation controllers. An 18" overflow line at each tank series is routed to storm outlet in overflow cases.

A radio control system is installed on the roof of each garage operating by line of sight for seamless communication between each water harvesting system.

Case Study 2
Just down the road from Toyota's headquarters is Kubota Tractor Corporation's new North America headquarters in Grapevine, Texas. There water harvesting techniques are also utilized. Site topography benefited the holistic water harvesting system by implementing both form and function.

Rainwater Harvesting - Two Case Studies

The tanks, 10 in each of the garages, are interconnected with 12" plumbing to create a single storage unit. One reason corrugated steel tanks were selected over other options is that they fit nicely in unused space in the center of each parking garage.

Rainwater Harvesting - Two Case Studies

A PLC (Programmable Logic Controller) determines start and stop of a 10-horsepower, variable speed drive, irrigation pump in a steel mounted skid and aluminum enclosure outside of each garage, capable of delivering 60 gallons per minute at 75 PSI. Additionally, all four systems can be activated simultaneously to provide a combined 240 gallons per minute at 75 PSI, allowing for a shorter watering window.

Roof runoff is captured from a set of downspout scuppers, creating a waterfall to a collection basin below. The stormwater is captured in a basin lined with boulders and river rock, designed to be visually pleasing whether during a rain event or a dry cycle. Drain lines then gravity feed to the 46,700-gallon galvanized corrugated steel storage tank to serve the system. Very early in the conceptual design phase, teamwork between Pacheco Koch and inCon-trol Construction identified goals, objectives, constraints, and opportunities to ensure the implementation and longevity of the water harvesting system.

As most water harvesting techniques collect sand, silt and debris; these pump stations include a self-cleaning filter to insure less debris goes into the irrigation system. The control system includes low water alarm/shut off, high water alarms, flow control, and soft fill. Variable speed drives allow for a wide
range of control and provide an energy efficient system.

On both Toyota's and Kubota's campuses, the plan was simple: Strive for the best system by offering a wide variety of landscape water usage services focusing on quality, conservation and resources.

Rainwater Harvesting - Two Case Studies

At Kubota's Tractor Corporation's new North America headquarters in Grapevine, Texas, it was determined that a single 46,700-gallon galvanized corrugated steel storage tank would serve the system.

Rainwater Harvesting - Two Case Studies

With the rainwater harvesting system at Kubota, also designed by Pacheco Koch, roof runoff is captured from a set of downspout scuppers that direct the water to a collection basin below. Drain lines then gravity feed the water to the storage tank.

"We see opportunities for large campus properties to be positive advertisements to the community of how owners and developers can create value and be environmentally sensitive through creating smart water solutions,' says Wade Peterson, principal and director of landscape architecture at Pacheco Koch.

"Sustainability, that's what we like to concentrate on when designing rainwater harvesting systems", remarks registered landscape architect Jesse Wells with inCon-trol Water Systems.
There is much to consider on each project and it is the perspective of both the designer and contractors that help brings about efficient and successful projects. As stewards of the land, there is a responsibility to create design opportunities, not constraints. No matter the water-related project, the environment should be considered in every design decision. A collection of educational and practical experience will create smart water management in every situation. And having a great team is vital.

As seen in LASN magazine, July 2019.

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December 5, 2019, 6:47 am PDT

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