The existing SR 0722 Bridge and dam over Lititz Run was integral in the operations of the nearby Oregon Mill, which is listed on the National Register of Historic Places. Structurally deficient and functionally obsolete, however, the existing SR 0722 Bridge needed to accommodate modern-day traffic demands. Adding to the challenge was the role the existing bridge and dam played in sustaining local bird and fish habitats. The Black-crowned Night Heron — a potential endangered species — prefer breeding near the bridge’s high waters located upstream, and the American shad, a local fish, inhabit Lititz Run and could not migrate upstream from the bridge. The Pennsylvania Department of Transportation wanted the replacement structure to preserve the historic setting of Oregon Mill yet desired a consultant who could also address the environmental constraints and challenges this bridge replacement project posed.
RETTEW designed a single-span prestressed-concrete bridge with architectural surface treatments on the parapets, which mimic the stone on the historic mill. To ensure that the breeding patterns of the Black-crowned Night Heron remained undisturbed while also allowing the American shad the ability to swim upstream, RETTEW installed grade-control structures in the stream channel. These structures maintain stream characteristics upstream for the birds while reducing water levels for the fish. Additionally, the wider two-lane structure accommodates traffic demands while preserving the historic setting of Oregon Mill.