Huntington Beach, CA
PACE provided planning and design for a flood control channel diversion system and wetland stormwater treatment system to treat at least 3 MGD of stormwater that would otherwise flow directly into the Bolsa Chica Wetlands and Huntington Harbor and further impair the water bodies. An innovative treatment system was developed specifically for a 22 square mile Orange County watershed tributary to the East Garden Grove-Wintersburg Channel in Huntington Beach, CA. The project diverts the flows from the channel to the existing City Central Park. The system relies on interconnected key components which include: (1) a flexible in-channel collection system, (2) conveyance system to the treatment train, (3) primary wetland treatment train system, (4) manmade lake polishing treatment system, and (5) groundwater recharge and reuse. An inflatable rubber dam in the existing concrete channel captures and temporarily stores the dry-weather flows while avoiding impacts to the flood control capacity. A forebay and pump station underneath the channel access road which pumps the flows to Central Park located approximately one mile away. The dry-weather flow delivered to Central Park is distributed to three independent wetland treatment cells which are composed of several interconnected shallow wetlands and wetland ponds. The wetland cells include surface and specialized subsurface wetland treatment elements that utilize surface area for the growth of bacterial biofilters. The outflow from the wetland treatment system discharges for final polishing into the existing manmade Talbert Lake which provides stormwater treatment, groundwater recharge, park irrigation and ensures a year-round permanent water body since the lake was previously subject to drying up in low rain event years. The restored manmade lake system is specifically designed for stormwater treatment utilizing (1) submerged media biofilters, (2) lake aeration, (3) in-lake pumped circulation, and (4) water quality filters and wetland planters. The water quality of the restored engineered lake is designed to recreate the natural biological processes and develop a managed ecosystem that provides water quality treatment.