Hayward Area Recreation and Park District Completes Koi Pond Bio-Filtration Wetland and Cedar Bridge Restoration at Japanese Gardens

Horticultural curators with the Hayward Area Recreation and Park District (HARD) and master woodworkers from the Japanese Garden Society completed a biological wetland koi-pond filtration system, a traditional Port Orford cedar footbridge restoration, and an accessible stone viewing terrace on Sunday morning at the Hayward Japanese Gardens at 22373 North Third Street (at Crescent Avenue) in Hayward. Designed in 1963 by acclaimed landscape architect Kimio Kimura using traditional Sukiya teahouse principles and native Bay Area boulders, the 3.5-acre sanctuary bordering San Lorenzo Creek is recognized as the oldest public garden in California built in the authentic classical Japanese style.

To keep the central 110,000-gallon koi pond crystal clear during warm autumn afternoons without relying on chemical algaecides, aquatic engineers constructed a concealed 1,400-square-foot upflow gravel bog bio-filter and ultraviolet clarifier loop hidden behind the upper waterfall cascade. Beneficial nitrifying bacteria colonizing volcanic lava rock and native horsetail reeds naturally consume dissolved nutrients, improving dissolved oxygen levels for the garden's sixty prized Nishikigoi carp while cutting circulation pump electricity by 44 percent.

Spanning the central narrows of the pond, artisanal carpenters reconstructed the curved pedestrian footbridge using rot-resistant kiln-dried Port Orford cedar and traditional mortise-and-tenon joinery without exposed metal fasteners. Crews also graded a flush granite wheelchair viewing terrace beside the main teahouse pavilion.

The $345,000 garden preservation project was funded through HARD Measure F1 bond funds approved by the Board of Directors. East Bay visitors can check free daily admission hours on the Hayward Area Recreation and Park District Japanese Gardens Portal.