NTM Engineering provided the Post-Construction Stormwater Management (PCSM) Plan, Erosion and Sediment Pollution Control (E&S) Plan, NPDES (stormwater) Permit, and Dam Safety Permit for 1.25 miles of roadway widening (from two to four lanes and from three to six lanes) along SR 0228, Mars-Valencia Road. Design challenges included discharging to waters with 303(d) impairments, soils with limited or no infiltration capacity, and an urban landscape with limited space for BMPs.
NTM designed several unique and site-specific stormwater BMPs, including a biofiltration basin, bioslope, wet pond, and infiltration trench with a level spreader. An adjacent property’s existing wet pond was displaced by the roadway widening, and relocating and increasing the pond’s capacity to help offset stormwater impacts necessitated obtaining a Dam Safety Permit. NTM prepared the Dam Safety Permit, coordinated agency meetings, and facilitated expedited approval of the Dam Safety Permit prior to the project’s let date. NTM also prepared an NPDES permit for the project, and the PA DEP approved the NPDES permit with no comments on the PCSM design. The E&S design received minimal comments from the Butler County Conservation District.
As part of this SR 0228 corridor project, NTM performed a hydrologic and hydraulic (H&H) study and the Type, Size, and Location Report for the Section 251 Arch Culvert Extension over Break-neck Creek. NTM was tasked with developing the culvert extension’s preliminary and final designs for a 75-foot extension to a cast-in-place arch culvert at a 55 degree skew.
To eliminate backwater increases, NTM designed the new arch culvert to widen from the existing 26 feet 9 inches to 36 feet and, because the extension is in the upstream direction, included a tapered funnel arch section. NTM also analyzed and reviewed all culvert components, including the arch barrels, headwalls, and counterfort designs.