The Maryland Zoo Water Quality Mitigation Designs

EBA conducted geotechnical, topographic, hydrologic, and pollutant-load site evaluations for two new water quality treatment systems at The Maryland Zoo. The information was used to design two water quality treatment facilities: a bioretention facility to treat 2.75 acres of existing impervious area and a step pool stormwater conveyance system (SPCS) regenerative practice to restore 100 feet of eroded channel. These new systems will control stormwater runoff and reduce the pollutant loads released by stormwater runoff to the Jones Falls stream system.

The bioretention facility ponded water to a depth of 1 foot and covered an area of approximately 10,000 square feet to filter and infiltrate parking lot runoff to the maximum extent practicable. The SPCS had step pools that were placed at a 5 percent slope with steeper cascades and at both ends of the system to stabilize the stream channel’s failed 12 percent slope and to tie a storm drain outfall into the perennial receiving water system. Natural areas were preserved to enhance zoo themes and protect the environment. Pollutant load reductions for nutrients and sediments were achieved to support Baltimore’s efforts to restore the Chesapeake Bay and meet total maximum daily load targets.