Wild About Water Conservation
The Denver Zoo saved money and transformed its culture while fulfilling its mission.
One might think water conservation would come naturally to an institution like the Denver Zoo. After all, “Conservation is a key component of the zoo’s mission,” declares George Pond, the zoo’s vice president for planning and capital projects. And yet, when staff reviewed the zoo’s water usage in 1999, “It was breathtaking to discover how much water we were using,” admits Curator of Birds John Azua. “We didn’t realize it until we took a deeper look.” The zoo’s water audit found that it was using 40 million gallons of water per year in the flamingo pond alone. Today, as a result of an upgrade to the flamingo pond and an ongoing series of repairs and redesigns of other exhibits, the zoo has gone from using 300 million gallons of water annually at the time of the audit to 75 million gallons. Its water bill for 2005 was $228,000, compared to $924,000 in 1999. Most importantly for an organization dedicated to conservation, though, “We were able to meet our environmental goals of using water wisely while providing a great habitat for our animals,” says Azua.
The initiative at the zoo originated in converging efforts by both the zoo and Denver Water, the utility that supplies water to the city and county of Denver as well as many surrounding suburbs, to focus on conservation. The zoo undertook a master planning process in 1998, culminating in the adoption of its Millennium Master Plan. At the time, Pond says, there was widespread recognition that “we’re a conservation organization.
We’re in Denver, Colorado, which has significant water issues. We needed to walk our talk” when it came to water usage. Jim Reed, a conservation specialist with Denver Water, concurs with Pond’s assessment of the region’s resources, noting that the area is periodically subject to water shortages. Mindful that Denver’s population increased more than 19% between 1990 and 2005 (according to US Census Bureau figures), Denver Water has launched a 10-year conservation plan, aiming for a 20% reduction in water usage by all its customers—residential, commercial, and industrial. Indeed, in developing its 50-year water supply plan, Reed says the utility decided that one-third of future water needs would be met by conservation measures, while one-third would come from reused sources, and one-third from new sources. When conservation specialists at the utility determined that the Denver Zoo’s water consumption was greater than that of some larger zoos, they approached the zoo with this information and offered to conduct an audit. The zoo accepted, and a two- to three-month review of water usage at the 80-acre campus began, going “hose by hose,” recalls Pond.
 |
| Lessons learned from the flamingo pond project will be incorporated into the zoo's next major project, the Asian Tropics exhibit for elephants. |
The findings led the zoo to implement what Denver Water refers to as “the three Rs of water conservation”—repair, retrofitting, and replacement. This was no simple task for a century-old institution. Korbin Pugh, the zoo’s construction coordinator, reckons that some of the pipes were 60 to 70 years old, which Billy Gregg, a landscape architect associated with the project, thinks is a conservative estimate. “Moving a facility forward that hadn’t been improved in a hundred years,” says Gregg, was a significant challenge. The first projects the zoo tackled were the polar bear and sea lion exhibits. Parts of the filtration system were not working, so the system was modified. As an interim measure to address the high water usage in the flamingo pond, a management decision was made to cut usage in the exhibit by half—to 20 million gallons. Although the animal staff, according to Pond, had been using the amount of water they thought was needed to maintain the health of the birds and the aesthetic appeal of the exhibit to visitors, the dramatic reduction in water use harmed neither the birds nor the exhibit.
That was only the beginning for the flamingo pond, however. Pond and his staff embarked on an ambitious plan to transform the flamingo pond from a “dump and fill operation”—as Pugh describes the old exhibit—to a constructed wetland complete with ecologically appropriate plants and stocked with fish approved by the State of Colorado. The $50,000 project, explains Pond, was a way to field-test the feasibility of recirculation systems and wetland features that were being contemplated for future redevelopment projects at the zoo.
There was one critical variable in this experiment: “the collection,” as Gregg has learned to call the zoo’s inhabitants. “Flamingos are tremendously difficult and sensitive to work with,” notes Gregg, who at the time of the project was with Wenk Associates and is now principal of his own firm, Parks and Gardens. With the health and safety of the flamingos paramount, the pond project was a true collaboration among the animal staff, planning staff, and design professionals. “By sharing our needs up-front, we were able to alleviate my concerns that we’d have the water we needed to provide for our animals,” explains Bird Curator Azua. This is not to say that the planning process was entirely smooth. While the zoo’s staff includes “more tree-huggers than tree-killers,” in Pond’s colorful description, he also recalls that some staff members were skeptical of the wetland idea, and others were uncomfortable at the prospect of changing ingrained practices. Ultimately, though, says Azua, “We were all on the same page working toward the same goals of being wise water stewards and responsible caretakers for our animals.”
 |
| The zoo began its water conservation efforts with the polar bear and sea lion exhibits, where the filtration system was modified. |
In this case, taking care of the animals meant starting the project while the flamingos were in their winter quarters. The pond, which is not concrete-lined, was dredged and sludge was removed. A recirculating pump was installed to move water from the pond to the wetland return area, where layers of sand and gravel had been added for filtration. Brandon Mix, a fisheries biologist with the water-quality consulting firm Aqua Sierra, designed a hybrid air diffusion system for the pond itself, consisting of linear aeration tubing as well as a funnel-like coil of tubing. “It’s definitely a unique system,” says Mix, who also recommended the use of beneficial bacteria to balance the nutrient content of the water. Time constraints on the project were significant, reports Gregg: There was only a brief interval of time between the ground thawing sufficiently to allow for planting and the return of the flamingos to their summer exhibit space. “We needed to get plants in and established with protection [fencing to keep them safe from migratory birds],” explains Gregg. “Then once the flamingos were in, the level of protection was reduced.”
Like many prototypes, the redesigned flamingo pond was not an unqualified success. Everybody associated with the project describes it in terms such as “work in progress” and “learning experience.” For example, says Pond, the flow of water through the wetland was not as smooth and even as they had hoped, as sedimentation gradually began clogging some of the water lines, causing water to come through only three or four heads rather than all 11 installed. Pond says this taught him that future designs should incorporate a self-cleaning feature or allow for non-disruptive, cost-effective maintenance of the water lines. And despite Pond’s valiant efforts to establish plant life in the wetland—virtually encasing plants in mesh to protect them from being eaten by ravenous migratory birds passing through—the plants thrived for only the briefest period of time before anaerobic conditions in the pond caused them all to die.
 |
As a field test, however, the flamingo pond imparted valuable lessons to those associated with it. Mix, of Aqua Sierra, quickly learned that water chemistry is a primary factor—along with typical considerations such as volume of water, exchange rate, and maximum and average depths of water—in designing an effective aeration system. The flamingo pond is a challenging environment, explains Mix, due to the “high nutrient loading” of the water. This is a fisheries biologist’s euphemism for the large volume of bird droppings that settle to the bottom of the pond and decompose, eating up oxygen and overloading the water with nutrients such as phosphorus and nitrogen. Gregg, the landscape architect, concluded that the size of the constructed wetland (well under half an acre) was probably too small to filter water effectively. In retrospect, he says, “I don’t think it is practical to build or retrofit a wetland strictly for the purposes of achieving water-quality goals at the zoo. It takes up too much space, it’s a complicated process that would take time to establish, and there would be seasonal fluctuations in water quality related to freezing temperatures.” Even given all that, Pond notes that the incidence of problems such as algae blooms and odor is no greater under the current configuration and has probably even improved a little.
Yet despite his second thoughts about constructed wetlands, Gregg maintains, “It was worth the effort in this case, because reducing consumption was and remains a very high priority.” Gregg’s comment underscores the fact that, although the flamingo pond project may not have accomplished all of its goals, annual water usage in the exhibit dropped impressively from an already-reduced 20 million gallons to under 1 million gallons, without any negative effects on the animals. In fact, notes Pond, by installing the wetland “upstream,” they modified the birds’ feeding area, which is now larger and allows the birds to engage in more natural feeding behavior.
While conservation goals drove the project, the zoo benefited from substantial cost savings as well. As part of its incentive program for industrial and commercial customers, Denver Water offers a one-time rebate of up to $40,000 for conservation projects that result in a minimum water savings of 300,000 gallons per year. The first year after the completion of the new flamingo pond, the zoo saved about $50,000 on its water bill. The project thus paid for itself even without the added bonus of the rebate the zoo received from Denver Water. “It’s good business. It’s good conservation,” says Pond simply.
Not content to rest on the laurels it’s earned for the flamingo pond project, the zoo is looking to the future. Pond plans to increase water savings by redesigning a series of two concrete-lined duck ponds—an exhibit that currently uses about 25 million gallons of water a year. Rather than draining, cleaning, and refilling it every other week, as is currently done, the zoo will be adding a sand filtration system and a copper-electrode system to mitigate algae. The zoo has also embraced reuse: Pond estimates the zoo can use recycled water, which Denver Water began offering in 2003, for up to 75% of its water needs. For its redesigned front entry and new Predator Ridge exhibit, the zoo installed the first phase of its recycled water infrastructure: a pump station, underground piping for irrigation, and a hose-down for the lions. The animals in the exhibit appear to be thriving with recycled water in their environment: Pond notes that the zoo has one of the more successful captive-breeding programs for lions, hyenas, and wild dogs.
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The zoo’s next big project, says Pond, will be Asian Tropics, an elephant exhibit that will have the capacity to house perhaps as many as eight bull elephants and possibly even a breeding facility. It will feature a 700-gallon recycled-water recirculation system, and in key locations, the barrier between visitors and the elephants will be underwater, invisible. Having learned firsthand from the flamingo pond the difficulty of establishing a water filtration system in the midst of the animal habitat, Gregg says that for Asian Tropics, they will try to filter the water in an area separate from the elephants’ habitat, in what he calls “the vegetated margins” between the visitor paths and fencing.
Working on the flamingo pond has broadened the perspectives of all involved. “This project has been very good for us in many ways,” says Azua. “It has helped us look at what we are doing in all of our exhibits and challenged us to use what we learned to conserve water in exhibits and daily use as well.” Having begun with a focus on water quality and water conservation, Pond says the zoo now plans to pursue LEED (Leadership in Energy and Environmental Design) certification from the US Green Building Council for the Asian Tropics exhibit. Gregg emphasizes the importance of integrating water conservation into design: “Water conservation and especially water quality aren’t just problems to be solved parallel to design. The solution to a problem should form the basis for design. We were trying to make a functional and attractive exhibit space that also worked to conserve water and improve water quality.”
Author's Bio: Based in Santa Barbara, CA, Journalist Amy R. Ramos writes on scientific and technical subjects.
November-December 2006
Wild About Water Conservation
The Denver Zoo saved money and transformed its culture while fulfilling its mission.
One might think water conservation would come naturally to an institution like the Denver Zoo. After all, “Conservation is a key component of the zoo’s mission,” declares George Pond, the zoo’s vice president for planning and capital projects. And yet, when staff reviewed the zoo’s water usage in 1999, “It was breathtaking to discover how much water we were using,” admits Curator of Birds John Azua. “We didn’t realize it until we took a deeper look.” The zoo’s water audit found that it was using 40 million gallons of water per year in the flamingo pond alone. Today, as a result of an upgrade to the flamingo pond and an ongoing series of repairs and redesigns of other exhibits, the zoo has gone from using 300 million gallons of water annually at the time of the audit to 75 million gallons. Its water bill for 2005 was $228,000, compared to $924,000 in 1999. Most importantly for an organization dedicated to conservation, though, “We were able to meet our environmental goals of using water wisely while providing a great habitat for our animals,” says Azua.
The initiative at the zoo originated in converging efforts by both the zoo and Denver Water, the utility that supplies water to the city and county of Denver as well as many surrounding suburbs, to focus on conservation. The zoo undertook a master planning process in 1998, culminating in the adoption of its Millennium Master Plan. At the time, Pond says, there was widespread recognition that “we’re a conservation organization.
We’re in Denver, Colorado, which has significant water issues. We needed to walk our talk” when it came to water usage. Jim Reed, a conservation specialist with Denver Water, concurs with Pond’s assessment of the region’s resources, noting that the area is periodically subject to water shortages. Mindful that Denver’s population increased more than 19% between 1990 and 2005 (according to US Census Bureau figures), Denver Water has launched a 10-year conservation plan, aiming for a 20% reduction in water usage by all its customers—residential, commercial, and industrial. Indeed, in developing its 50-year water supply plan, Reed says the utility decided that one-third of future water needs would be met by conservation measures, while one-third would come from reused sources, and one-third from new sources. When conservation specialists at the utility determined that the Denver Zoo’s water consumption was greater than that of some larger zoos, they approached the zoo with this information and offered to conduct an audit. The zoo accepted, and a two- to three-month review of water usage at the 80-acre campus began, going “hose by hose,” recalls Pond.
|
| Lessons learned from the flamingo pond project will be incorporated into the zoo's next major project, the Asian Tropics exhibit for elephants. |
The findings led the zoo to implement what Denver Water refers to as “the three Rs of water conservation”—repair, retrofitting, and replacement. This was no simple task for a century-old institution. Korbin Pugh, the zoo’s construction coordinator, reckons that some of the pipes were 60 to 70 years old, which Billy Gregg, a landscape architect associated with the project, thinks is a conservative estimate. “Moving a facility forward that hadn’t been improved in a hundred years,” says Gregg, was a significant challenge. The first projects the zoo tackled were the polar bear and sea lion exhibits. Parts of the filtration system were not working, so the system was modified. As an interim measure to address the high water usage in the flamingo pond, a management decision was made to cut usage in the exhibit by half—to 20 million gallons. Although the animal staff, according to Pond, had been using the amount of water they thought was needed to maintain the health of the birds and the aesthetic appeal of the exhibit to visitors, the dramatic reduction in water use harmed neither the birds nor the exhibit.
That was only the beginning for the flamingo pond, however. Pond and his staff embarked on an ambitious plan to transform the flamingo pond from a “dump and fill operation”—as Pugh describes the old exhibit—to a constructed wetland complete with ecologically appropriate plants and stocked with fish approved by the State of Colorado. The $50,000 project, explains Pond, was a way to field-test the feasibility of recirculation systems and wetland features that were being contemplated for future redevelopment projects at the zoo.
There was one critical variable in this experiment: “the collection,” as Gregg has learned to call the zoo’s inhabitants. “Flamingos are tremendously difficult and sensitive to work with,” notes Gregg, who at the time of the project was with Wenk Associates and is now principal of his own firm, Parks and Gardens. With the health and safety of the flamingos paramount, the pond project was a true collaboration among the animal staff, planning staff, and design professionals. “By sharing our needs up-front, we were able to alleviate my concerns that we’d have the water we needed to provide for our animals,” explains Bird Curator Azua. This is not to say that the planning process was entirely smooth. While the zoo’s staff includes “more tree-huggers than tree-killers,” in Pond’s colorful description, he also recalls that some staff members were skeptical of the wetland idea, and others were uncomfortable at the prospect of changing ingrained practices. Ultimately, though, says Azua, “We were all on the same page working toward the same goals of being wise water stewards and responsible caretakers for our animals.”
|
| The zoo began its water conservation efforts with the polar bear and sea lion exhibits, where the filtration system was modified. |
In this case, taking care of the animals meant starting the project while the flamingos were in their winter quarters. The pond, which is not concrete-lined, was dredged and sludge was removed. A recirculating pump was installed to move water from the pond to the wetland return area, where layers of sand and gravel had been added for filtration. Brandon Mix, a fisheries biologist with the water-quality consulting firm Aqua Sierra, designed a hybrid air diffusion system for the pond itself, consisting of linear aeration tubing as well as a funnel-like coil of tubing. “It’s definitely a unique system,” says Mix, who also recommended the use of beneficial bacteria to balance the nutrient content of the water. Time constraints on the project were significant, reports Gregg: There was only a brief interval of time between the ground thawing sufficiently to allow for planting and the return of the flamingos to their summer exhibit space. “We needed to get plants in and established with protection [fencing to keep them safe from migratory birds],” explains Gregg. “Then once the flamingos were in, the level of protection was reduced.”
Like many prototypes, the redesigned flamingo pond was not an unqualified success. Everybody associated with the project describes it in terms such as “work in progress” and “learning experience.” For example, says Pond, the flow of water through the wetland was not as smooth and even as they had hoped, as sedimentation gradually began clogging some of the water lines, causing water to come through only three or four heads rather than all 11 installed. Pond says this taught him that future designs should incorporate a self-cleaning feature or allow for non-disruptive, cost-effective maintenance of the water lines. And despite Pond’s valiant efforts to establish plant life in the wetland—virtually encasing plants in mesh to protect them from being eaten by ravenous migratory birds passing through—the plants thrived for only the briefest period of time before anaerobic conditions in the pond caused them all to die.
|
As a field test, however, the flamingo pond imparted valuable lessons to those associated with it. Mix, of Aqua Sierra, quickly learned that water chemistry is a primary factor—along with typical considerations such as volume of water, exchange rate, and maximum and average depths of water—in designing an effective aeration system. The flamingo pond is a challenging environment, explains Mix, due to the “high nutrient loading” of the water. This is a fisheries biologist’s euphemism for the large volume of bird droppings that settle to the bottom of the pond and decompose, eating up oxygen and overloading the water with nutrients such as phosphorus and nitrogen. Gregg, the landscape architect, concluded that the size of the constructed wetland (well under half an acre) was probably too small to filter water effectively. In retrospect, he says, “I don’t think it is practical to build or retrofit a wetland strictly for the purposes of achieving water-quality goals at the zoo. It takes up too much space, it’s a complicated process that would take time to establish, and there would be seasonal fluctuations in water quality related to freezing temperatures.” Even given all that, Pond notes that the incidence of problems such as algae blooms and odor is no greater under the current configuration and has probably even improved a little.
Yet despite his second thoughts about constructed wetlands, Gregg maintains, “It was worth the effort in this case, because reducing consumption was and remains a very high priority.” Gregg’s comment underscores the fact that, although the flamingo pond project may not have accomplished all of its goals, annual water usage in the exhibit dropped impressively from an already-reduced 20 million gallons to under 1 million gallons, without any negative effects on the animals. In fact, notes Pond, by installing the wetland “upstream,” they modified the birds’ feeding area, which is now larger and allows the birds to engage in more natural feeding behavior.
While conservation goals drove the project, the zoo benefited from substantial cost savings as well. As part of its incentive program for industrial and commercial customers, Denver Water offers a one-time rebate of up to $40,000 for conservation projects that result in a minimum water savings of 300,000 gallons per year. The first year after the completion of the new flamingo pond, the zoo saved about $50,000 on its water bill. The project thus paid for itself even without the added bonus of the rebate the zoo received from Denver Water. “It’s good business. It’s good conservation,” says Pond simply.
Not content to rest on the laurels it’s earned for the flamingo pond project, the zoo is looking to the future. Pond plans to increase water savings by redesigning a series of two concrete-lined duck ponds—an exhibit that currently uses about 25 million gallons of water a year. Rather than draining, cleaning, and refilling it every other week, as is currently done, the zoo will be adding a sand filtration system and a copper-electrode system to mitigate algae. The zoo has also embraced reuse: Pond estimates the zoo can use recycled water, which Denver Water began offering in 2003, for up to 75% of its water needs. For its redesigned front entry and new Predator Ridge exhibit, the zoo installed the first phase of its recycled water infrastructure: a pump station, underground piping for irrigation, and a hose-down for the lions. The animals in the exhibit appear to be thriving with recycled water in their environment: Pond notes that the zoo has one of the more successful captive-breeding programs for lions, hyenas, and wild dogs.
The zoo’s next big project, says Pond, will be Asian Tropics, an elephant exhibit that will have the capacity to house perhaps as many as eight bull elephants and possibly even a breeding facility. It will feature a 700-gallon recycled-water recirculation system, and in key locations, the barrier between visitors and the elephants will be underwater, invisible. Having learned firsthand from the flamingo pond the difficulty of establishing a water filtration system in the midst of the animal habitat, Gregg says that for Asian Tropics, they will try to filter the water in an area separate from the elephants’ habitat, in what he calls “the vegetated margins” between the visitor paths and fencing.
Working on the flamingo pond has broadened the perspectives of all involved. “This project has been very good for us in many ways,” says Azua. “It has helped us look at what we are doing in all of our exhibits and challenged us to use what we learned to conserve water in exhibits and daily use as well.” Having begun with a focus on water quality and water conservation, Pond says the zoo now plans to pursue LEED (Leadership in Energy and Environmental Design) certification from the US Green Building Council for the Asian Tropics exhibit. Gregg emphasizes the importance of integrating water conservation into design: “Water conservation and especially water quality aren’t just problems to be solved parallel to design. The solution to a problem should form the basis for design. We were trying to make a functional and attractive exhibit space that also worked to conserve water and improve water quality.”