Award-Winning Water Smart Infrastructure
Modjeska Park is a 23.5-acre park located in Anaheim, California within Orange County. The neighborhood around the park would often experience extensive ﬂooding caused by an under-sized storm drain line posing a hazard to motorists and pedestrians alike. An underground stormwater infiltration and retention system were needed to protect and enhance regional water quality, manage stormwater runoff, increase local groundwater supply, and improve public safety. The system consisted of an underground; pre-manufactured inﬁltration/detention system constructed beneath the existing 37,000-square-foot parking lot in Modjeska Park.
Underground Detention and Infiltration System
The project constructed a six-acre-ft (2M Gallon) reinforced pre-cast concrete stormwater detention and infiltration system including subgrade drainage wicks, a diversion drop structure, a trash capture system, and landscaping restoration. The project diverted stormwater from an existing 48-inch storm drain line running south along Nutwood Street through a 48-inch diversion drop structure to a new reinforced cast-in-place concrete trash capture system before entering the detention and infiltration gallery. The project was designed to infiltrate approximately 150 acre-ft/per year. The project required excavating 48,600 CY of native material, of which, 17,000 CY was exported offsite. A cast-in-place concrete drop structure was installed to intercept water from the existing 48-inch storm drain. From there, stormwater enters a 6 Acre-ft (2.0 MGal) reinforced pre-cast high-strength concrete detention gallery with a pretreatment settling chamber comprising of 456 individual pieces, then through a mesh trash capture vault with stainless steel capture screens. Once the underground facility was completed, more than 31,600 CY of material was backfilled and compacted. The site was further enhanced with decorative interlocking pervious pavers for the parking lot surface and landscape restoration.
Ghirardelli Associates performed construction management, contract administration, and inspection throughout all phases of the project from award to completion.
Community and Environmental Benefits Ahead of Schedule
Once completed, the project effectively reduced the stormwater volume in regional flood control channels and enhanced water quality. Nuisance flooding no longer encroaches on homeowners’ properties or threatens damage to current infrastructure. By eliminating backflow into the street, the roadway conditions are safer for motorists and pedestrians alike during storm events. This project was completed ahead of schedule and received two awards for its success including a 2021 Water Project of the Year from the American Society of Civil Engineers Orange County Chapter and a 2020 Project of the Year Award from the American Public Works Association’s Southern California Chapter.