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M·E Companies was retained by the Cincinnati Zoo and Botanical Garden to design the expansion of three parking areas located along the Zoo perimeter (400 new spaces). As part of the Zoo’s commitment to Building Green, we explored various approaches to the design and material selection of the parking lots.

 

The use of traditional asphalt and concrete, pervious pavers, porous asphalt and pervious concrete were considered. Traditional detention and percolation were also considered. During the design process, double-ring infiltrometer tests were performed. These tests revealed that the soil was not capable of percolation.

 

We developed a “hybrid” (grey/green) design. Concrete was selected as the paving material for the drive aisles. The use of concrete paving lowers the long term maintenance costs for the Zoo and reduces the heat island effect. Pervious concrete was used in the parking areas. Under each “cell”, open graded #57’s and #2’s of varying depths are used to detain the stormwater. The MSD stormwater regulation requires the detention of a 25 year post developed storm back to a 10 year, pre-developed rate. Storms less than a 10 year event are undetained. The Zoo is sensitive to the issues of CSO’s and has worked diligently on other projects to minimize their impact on downstream neighbors (most of the Zoo is tributary to CSO 482). As such, the Zoo committed to detaining the 50 year, post developed storm back to a one year, pre developed rate.

 

Stormwater passes through the pervious concrete and is stored in the gravel layer. The gravel layer is drained with an underdrain system that connects to the combined sewer. Use of this type of system resulted in a 20% cost savings to the Zoo. This installation of pervious concrete is one of the largest in Ohio, with a total of more than 40,000 s.f. of pervious concrete. The underdrain system drains to a central manhole, where flow monitoring will be performed to determine the overall performance of the system.

 

The project also included the re-construction of 200’ of MSD combined sewer (SS #6012).