The new Hamilton Family Children’s Zoo at the Philadelphia Zoo transforms the former pachyderm building and elephant yard into a new indoor/outdoor interactive children’s zoo where water and its role in supporting the environment are a key educational feature. Meliora Environmental Design provided full civil engineering and permitting services. Meliora’s approach was to manage rainfall as a resource instead of managing stormwater as a problem, and this process required an integrated design team.
The site design for this project began with analyzing how rainfall would be distributed across the proposed site features – rooftops, pavements, planted areas, and animal exhibits. Focus on small, frequent stormwater events and the safe conveyance of large storms. A diverse palette of water management techniques were used including cisterns that capture roof water for flushing all new toilets, green roofs, pervious pavement to reduce runoff and protect an existing tree root system, multiple rain gardens that are part of a restored landscape, and subsurface stormwater infiltration beds.
The site design had numerous challenges due to compacted soils, a maze of existing utilities, the construction of a geothermal well field beneath the site, and multiple overhead bridges and raceways for the animals that required utilities. Also, runoff from animal areas was treated as “wastewater,” so it was necessary to manage runoff from impervious areas outside of the project limit in lieu of animal areas where runoff must be handled as wastewater. The project met the stringent requirements of the Philadelphia Water Department and LEED Silver certification is anticipated.
In order to promote infiltration, the subsurface stone beds that manage 1-inch of runoff from impervious surfaces were designed such that their bed bottom would be below the compacted soils of the animal yards, which had been trampled by elephants, rhinos, and hippos for numerous years. Initial testing showed favorable infiltration rates, but retesting at the actual bed bottom at the time of construction showed rates that did not meet the requirements of the Philadelphia Water Department. An alternative slow-release design using an underdrain had already been created, but instead of employing that design, the soils were scarified 6-inches in depth and retested. The infiltration rate improved to meet the design requirements, and it was possible for both beds to infiltrate the project runoff to replenish groundwater.
Watershed: Schuylkill River
The Hamilton Family Children’s Zoo is part of the Philadelphia Zoo in the city of Philadelphia, PA., in the Lower Schuylkill River Watershed.
Viridian Landscape Studio
Bruce E. Brooks & Associates
Becker & Frondorf, W.S. Cumby
For rain gardens, cisterns, and infiltration beds – $320,000
Altje Hoekstra, LEED AP
Meliora Environmental Design, LLC, Water Resources Designer
100 N. Bank Street
Phoenixville, PA 19460