The SR 2001 over Trout Creek project involved replacing a single-span, concrete slab bridge with a corrugated metal pipe arch. The bridge is located southeast of Allentown in Salisbury Township, Lehigh County. The bridge was closed after it was damaged by flooding in the fall of 2011. NTM Engineering was responsible for the bridge and roadway design, hydrologic and hydraulic (H&H) analysis, erosion and sedimentation control, waterway permitting, and utility coordination. NTM also oversaw subconsultants for the project’s environmental, geotechnical, and survey services.
This small project presented many challenges due to site restrictions and a compressed schedule to obtain available PEMA funding. A high-voltage utility line close to the downstream outlet prevented bridge designs that required a crane to place a precast culvert and temporary shoring. With these limitations and time constraints, NTM designed a 117-inch by 79-inch corrugated aluminized steel pipe arch replacement structure. Since temporary shoring at the outlet could not be used and temporary right-of-way easements could not be completed within the limited timeframe, a mitered, engineered 1:1 slope was used at the outlet. For the upstream inlet, NTM designed a cast-in-place headwall with flared wings. To ensure long-term serviceability, NTM recommended a 16-inch reinforced concrete relief slab be built over the pipe arch.
NTM performed a detailed H&H analysis of Trout Creek of the project site and determined that the proposed pipe arch conveys the 10‐year design event and reduces upstream backwater for the 10‐, 50‐, and 100‐year events.
NTM’s erosion and sedimentation control design addressed construction of the new culvert to limit stream impacts. Riprap protection was designed at both ends of the culvert to prevent erosion and scour.
For the roadway design, NTM recommended a tangent roadway over the proposed structure with two 10-foot lanes for traffic and two-foot shoulders with guiderails.
NTM began project design in September 2012 and secured the GP-7 waterway permit and completed the bid package by April 2013. The project was let in May 2013. The crossing was constructed and then opened in October 2013.