Waterscape Renovation at Franklin Park Zoo

By Demi Fortuna and Edwin Scott-Fortuna

Our company, August Moon Designs recently complete a waterscape renovation in a historic rock garden at the Franklin Park Zoo. Franklin Park was first designed by Frederick Law Olmstead, creator of New York’s Central Park. Known as the jewel of the Emerald Necklace of parks encircling Boston, Olmstead would die before the Park’s completion. However in 1910, Arthur Shurcliff, a former employee of the Olmsted office, was appointed to prepare a plan for the Franklin Park Zoo. The Zoo opened its first exhibit in 1912.

Years later, around 1930, Shurcliff built the rock garden with a stream that coursed down a hill from the base of an iconic folly, a stone replica of an ancient tower overlooking the plantings. Not long afterward, John D. Rockefeller Jr. asked Shurcliff to design and oversee the restoration of Colonial Williamsburg. To bring some of his work back to life was an honor indeed.

The garden had fallen into neglect over the last century. No one could tell us exactly when or how the stream last flowed. The lower part of the garden had been removed to make way for the adjacent African Tropical Forest exhibit that opened in 1989. When we first saw it on a cold winter’s day in 2022, it was difficult to tell a magnificent garden had ever existed. Overgrown with weeds and trees, only the original bridge and two stairs were still visible. What remained of the watercourse was a shallow dimple across the slope. We had our work cut out for us!

Breaking Ground on the Waterscape Renovation at Franklin Park Zoo

Uncovering what remained of the garden was the first step in the waterscape renovation. Aided by an amazing collection of photographs, possibly taken by Shurcliff himself, and with the tireless help of the zoo’s horticultural department, we uncovered the remains of the original rock work.

The upper two-thirds of the original stones had escaped the bulldozers of the ‘80s and were exactly as pictured in the photos. However the lower third was a barren, weedy slope. That turned out to be our greatest advantage.

We needed machine access to the site, because we didn’t want to disturb any original rock work. Our plan was to create an ADA-compliant walkway up the steep slope. The lower third of the hill had just enough room to squeeze in a diagonal path to the center of the garden. This is the point where we would intersect the original paths hidden under the weeds.

We divided the work into two parts. First, to find and clear what remained of the stream and figure out how to make it run again. Then we would extend the original watercourse. We would add new features all the way down to the bottom to draw people exiting the tropical forest into the rock garden.

Extra Foam

Our first surprise was the depth of the stream. It appeared as a shallow depression lined with stones crossing the slope. However, we ended up pulling out between 2 and 4 feet of soil and debris to get down the bottom of the original concrete trough. The trough was still intact after more than a century. Its angled sections featured flat bottoms and walls that varied in height up to 6 feet above the floor, where the stream passed under the bridge. The inner concrete walls were covered from view with dry-stacked stone. They were always ready to collapse inward as we pulled saplings and debris out from between them.

We needed a way to stabilize the inner walls without changing them in any way. After all, this was the work of giants — literally, the first U.S. “landscape architects,” a term coined by Olmstead. We found the ideal solution in waterfall foam. It would lock the most precarious stones in place without damaging or defacing them. Once the foam dried, we could remove all the visible signs of its presence while ensuring stability.

At the end of the original stream, we created a hidden reservoir and pumping station that would circulate water from what would look like a shallow stream back up to headwater pool at the base of the tower. We built a block enclosure on a concrete floor, lined it with geotextile and EPDM liner, and then covered the liner with another layer of geotextile and a 2-inch-thick layer of fiber-reinforced concrete.

We built a ramp that would comply with wheelchair guidelines — 8 feet wide with landings every 30 feet. Once that was in, we could begin recreating the lost watercourse.

The liner, fully encapsulated in this way, can easily resist the ravages of weather, storms and time. (Not to mention lions and tigers and bears). It is our go-to method for zoos, botanical gardens and public parks where protection against damage is critical.

Every feature we installed at the zoo — and there were many — has fully encapsulated liner. We installed a 4-inch, cast-iron drain valve in the reservoir and filled it with EcoBlox water matrix blocks and dual PV15000 Pump Vaults. We left room to cover everything with 3 to 4 inches of gravel. A piece of liner on top of the blocks ensured that water would run on top of the reservoir to the very end of the stream. There, it appeared to dip under a second bridge.

Building “Bridges”

The “bridge” was nothing of the sort. We set stones along either side of the walkway at its narrowest point, where the ramp from the bottom of the garden met the original encircling paths. We used huge pieces of salvaged bluestone from a stairway that had once decorated a deconstructed area of the garden. An intern who saved the stone 20 years before would later became the zoo’s president. Talk about foresight!

On the other side of the bridge, outside of the original garden, we decided to build a pond in the only spot on the slope that could accommodate one. Its interesting shape was a result of needing to shoehorn it in between a 4-inch water line to an adjacent fire hydrant, and an 8-inch gas line to power plant for the tropical forest.

Thank goodness my son Edwin is an artist on machinery. We installed the concrete walls to make it seem like water entered the pond from underneath the other side of the “bridge,” as if coming from the stream. We sloped the concrete floor to a 4-inch bottom drain with cast-iron valve for easy cleaning.

Once we were ready to line the pond, we built a waterfall on the face of the slope above the pond. This retained the hill and returned the water from a reservoir at the very bottom of the garden. Access to the slope above the pond was limited,. with no way to get large rock there safely. As a result, we used waterfall foam to create the general shape of the falls, then covered that with fiber-reinforced concrete to keep roots from growing through. A single piece of liner covered top and bottom with geotextile covered everything, and we sculpted the waterfall out of the concrete layer that covered the liner sandwich.

Opposite the waterfall, we built a stream of concrete in the same manner, terminating at the very bottom of the garden at a second EcoBlox reservoir. We fit it with PV15000 Pump Vaults and a 4-inch valved drain for easy maintenance. Because the reservoir was right across from the doors of the tropical forest, and we wanted to draw people into the garden, we installed an Oase Aquarius EcoExpert 11500-gph fountain pump in one of the vaults, powering three Schaumsprudler nozzles (“frothy” in German sounds so much better!). The Aquarius pump makes the water continually dance, much to the delight of schoolchildren and adults alike.

The waterscape renovation of the rock garden took more than two years to complete because we ended up working on four other exhibits at the zoo, each of which took priority.

Condor Creek Waterscape Renovation

The first was the lining of the stream in the aviary, which we came to call Condor Creek after its rather intimidating inhabitants. We intended to quickly complete the straightforward, almost boring task of covering the 300-foot-long stream with our liner sandwich and then capping that with fiber-reinforced concrete. There would be no boulder work, because it was Shurcliff’s signature exhibit — one of the first and still one of the largest flight cages in the country, and perhaps the world.

We had to exactly match the appearance of the original plain concrete trough. A postcard turned that simple task upside down. One of the veteran zoo keepers found a postcard of the exhibit as it once looked, and it was a revelation. After the parks department rejected a number of designs, Shurcliff submitted a plan for a Grotto — three huge stone arches inset to form a cave that looked as if it receded deep into the earth. Stalactites grew from the ceiling and water flowed from its mouth.

Easily 40 feet tall and 50 feet wide, the only evidence of its existence were the few huge stones that made up the very top of the outer arch. No one at the zoo knows when it was done or why, but thousands of cubic yards of fill and truckloads of concrete were brought in at great expense to almost completely bury the Grotto.

Returning the Grotto

I couldn’t stand it. We had already bid the job and probably should have just let it stay buried, but I needed to see it returned to the light of day. With one crew making good progress relining the stream, I talked myself into splitting off a second crew to re-expose the monumental construct. The first hurdle was simple but arduous. We would break out the 4-inch-thick basin and “bowling ball” waterfall that had been built at the top of the mound concealing the rock work.

The process was complicated by the aviary itself. We had to pass all the excavated material by 5-gallon pail to a dumpster set outside through the aviary doorway. The next hurdle was massive and should have been impossible. Just under the 4-inch basin was a poured concrete cap 15 feet across and 2 feet thick. Obsessed by the task, I would have given up had fate not played a hand. On an off chance, I called the closest rental business to the zoo located literally blocks away. They specialized in electric machinery, and they had a tool I never knew existed. It was purpose built for what ailed us: a tracked robot bank vault dismantler designed to break up 24-inch reinforced concrete.

Who’d have thunk it? Not I! But there it was, climbing the 40-foot slope to the top of the mound, busting through the massive pour, making big rocks into little rocks. It took three days, but we completed the job. There was a bonus. The concrete had been poured on about 20 yards of clean, screened sand, for some unknown reason. There was enough sand for all the concrete I would need to remake the stream after excavation. We were able to expose the tops of all three arches and figure out the mystery of the stalactites visible in the postcard. We found a semicircular copper spray bar with tiny holes that must have sprayed limestone-rich water over concrete nubs that had been built into the ceiling of the Grotto.

Over time, the lime that had accreted on them gave them the look of natural stalactites. Brilliant! Now, the condors love to bathe in the generous stream that once again issues from the Grotto. I hope one day someone uncovers the rest of this amazing monument.

Standout Features of the Condor Creek Renovation

The rest of the stream works really well, also. We fixed the pump intake of the system, a skimmer grate completely surrounded by 30-inch-deep water. It used to required waders to clean it. Now it’s part of a surface level graveled upflow filter built with EcoBlox that makes access easy. A valve adjusts the flow between the stream and the upflow filter. Water flowing through the EcoBlox from a single point slows down and drops all its suspended solids. The 6-inch bed of gravel on top of the blocks supports plants that pull out the plentiful nutrients produced by the three massive raptors in the aviary — a pair of condors that might mate if all goes well, and a Stellar’s Sea Eagle named O-washi who is friendlier than his 6-inch talons might suggest.

Hyena Habitat

The last exhibit to mention combines a new 4-inch bottom drain, a wet sump and a shelter meant to evoke a response from the younger visitors to the zoo. The habitat for the hyena was difficult to clean, with an 1-1/2” pool style intake, a sand filter and a swimming pool pump. Bamboo all around the exhibit guaranteed an abundance of long, flat leaves that blocked the flow into the filter. The pool filter had difficulty with the debris that built up rapidly. Cleaning took two people a full day with an auxiliary pump to drain the pond and a lot of manual labor to clear the leaves in the convoluted stream that had many deep pockets that trapped and held leaves tenaciously.

We started with the drainage system, connecting a 4-inch bottom drain to a side inlet to a trough skimmer that hadn’t been functioning well. The 4-inch PVC line from the bottom drain pitched steeply down to a 4-inch cast iron valve, then out into a bamboo grove at grade. A 4-inch wye just before the valve extended a leg of 4-inch pipe pitched upward to a wet sump outside the pond made of an Atlantic PVRI Remote Pump Vault — basically a sealed box at the same level as the pond. A TT9000 submerged in the sump draws water down into the drainpipe from both the bottom and the skimmer trough.

Heavy wastes settle out near the wye instead of flowing uphill towards the sump, to be flushed at will by simply opening the valve. The pump delivered a generous flow — about 7500 gph — to the top of the stream, increasing circulation and oxygenation of the feature. To further simplify the cleaning procedure, we filled in the pockets of the stream, widened it to a constant broom width and built up the edges to contain the greater flow. In keeping with a theme, we built a termite mound over the pump vault to keep the hyena out and built a red sandstone cave for shelter. Can you guess the theme? The kids sure can, especially since the exhibit is right next to the lions.

Improvements Save Time When Cleaning

Today, the cleaning procedure takes one person an hour or so. First, they sweep the stream down with the pump running to push all the debris into the pond. Then, they turn the pump off and rake out the leaves in the skimmer trough. They rinse whatever they can’t lift out easily into the pond. Then, they open the bottom drain to clear both the plumbing lines, raking whatever debris is in the pond into the powerful suction of the drain. All that’s left is to close the drain, refill and turn the pump back on.

We installed similar improvements in the Australian Bird Exhibit and the Painted Dog Pool, but you probably get the picture. We hope we’ll be helping out for many years to come.  

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