This is the third of an open ended series of articles detailing the design and construction experiences of the Hensley Field Operations Center, a facility currently seeking LEED certification.

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LEED WEcr1 focuses on water efficient landscaping. These two credits can be achieved through a variety of methods, including plant selection, non-potable water use, and water reduction through the design of the irrigation system. It’s interesting to note that interior irrigation is not included in this credit, and is also exempt from WEcr3. This is often an opportunity that is overlooked, as interior plants do not go dormant and require watering year round, resulting in significant water usage.

One of the first design items that we reviewed during the design charette of Hensley Field was rainwater harvesting. Initially, this seemed like a no-brainer. We had 80,000 square feet of membrane roof which would easily accommodate the collection of rainwater – this would easily be enough water to supply the irrigation requirements for our landscaping. However, this is easier said than done. This was the renovation of an existing facility, so we were dealing with existing slopes and drain lines. Because of the access to the facility, it quickly became impractical to divert all this water into a central tank. We also had too much existing concrete surrounding the facility to make it feasible to route new piping underground. Using several independent collection systems would also prove troublesome, as it would require segmenting the irrigation system. At the end of the day, we decided it was more practical to control the water requirements through Xeriscape, which also allowed us the elimination of the irrigation system altogether (and an $20,000 credit).

When we moved to the interior though, the subject of rainwater harvesting came back up. For this centralized area it might make sense. I had one overriding design constraint for the design team – no maintenance. This included everything from the durability of the materials inside the atrium, plant selection, and the mechanical components necessary for the system.

The first item that needed to be solved was the water source itself. We needed a way that we could gather rainwater into a central source, and then disperse it to several zones. The existing facility did lend itself to this design quite well with the stepped roof system that we already had. Now, I want to caution you before you look at the high-tech method that we used: we basically followed the age-old tradition of a water barrel. We placed a 1500 gallon cistern on our roof above the atrium. The cistern is fed from an existing roof scupper on the next level up. When it rains, rainwater is diverted into the cistern, which once full goes into an overflow back onto the roof and is drained off normally. The entire system works off of gravity – the higher the level of water, the more pressure is generated. We were roughly 25 feet above our source, which gave us just enough pressure to run the interior irrigation system. This completely eliminated the use of pumps.

Our inside design follows this simplicity in design. We were looking for durable materials that would require little maintenance, and we did not want to perform extensive saw-cutting and pour back of the concrete slab for irrigation lines. This lent itself to the creation of several series of curbs, which would in turn designate walk paths, define planting areas, and most importantly hide the irrigation lines. Rock was designated for the majority of the planters. We picked a Wyoming Pink for a variety of reasons. The large size would scale well in the atrium, while at the same time be easy to remove if access to the irrigation was required. The color provided a good contrast to the vegetation, and also hides dust very well (dust build-up can be problematic on dark colors of rock, and require raking).

The planters themselves were also elevated. This allowed irrigation lines to penetrate underneath the pots while providing a stable base. The pots themselves utilize an interior water reservoir. This IROX system allows natural wicking to occur, rather than flooding the plant material with water. We selected plants that were highly durable and also non-flowering. A standard irrigation controller is the only mechanical component to the entire irrigation system. The controller we used is capable of several zones, and is not much different from the type you have at your house. The only constraint we had was the pressure that was generated for the system. Since we were using gravity, the pressure is much lower than you would normally expect, resulting in only one zone being able run at a time. This ended up not being an issue since we were on the interior and had more flexibility for scheduling.

The last major factor in the design was the walk paths. Again, low-maintenance was the key. With the traffic generated in this area, the material needed to be durable and long lasting. Also, I wanted a material that had no bonding or adhesion agents. Whenever dealing with water, it is always important to have an exit strategy if there is a leak. If a leak occurred over the weekend, we could have significant standing water for several days before it was noticed. We wanted a material that could handle being immersed in water with no ill effects.

EnviroGLAS Terrazzo proved the solution. Once this material is down, it will last forever – even in one of our facilities that will be in use for 75 plus years. It is capable of handling our traffic loads, and required very limited maintenance (no waxing). The EnviroGLAS system utilizes glass chips instead of the normal marble chips. This is a great benefit to us, as all the source material is generated locally, and any color combination is possible. It’s very difficult to tell this apart from standard terrazzo, and there is no cost difference. We used two different color combinations in our atrium that further accented the planters. I have to tell you, it’s a great feeling knowing that I can return to this facility in 20 years, and it will still look as good as it does today.