New Jersey Turnpike Authority Phase II Detail Scour Analysis

Princeton Hydro was part of a two-firm team tasked with the completion of Phase II detail scour analyses for the New Jersey Turnpike Authority (NJTA), a major state-wide transportation authority. Princeton Hydro was specifically tasked with the completion of scour analyses for 13 individual major highway bridges. These bridges were distributed throughout the state and included structures in both the coastal plain and piedmont physiographic provinces. The road crossings at the focus of the study range from single lane exit ramps to five-lane single direction major highways. The average daily traffic load of combined 13 road crossings which were studied is 1.3 million vehicles per day.

The detailed Phase II studies were conducted on structures which were previously identified during separate Phase I scour investigations and Biennial Bridge Inspection Reports. Inspections and investigations ultimately either confirmed the existing Federal Highway Authority Structure Inventory and Appraisal of the Nation’s Bridges (SI&A) codes including Items 61 (Channel and Channel Protection), Item 71 (Waterway Adequacy) and Item 113 (Scour Critical Bridges).

Princeton Hydro provided a wide range of services as it related to the scour assessments. These services included field inspection service planning and logistics as well and watercraft access to bridge structures. In-field engineering inspections of bridge structures with a focus on scour were also completed for the 13 structures. These inspections included the collection of photographs of the bridge and surrounding channel conditions as well as the collection of representative soil samples.

The soil samples were then delivered to our in-house soil laboratory, which is accredited under the American Association of State Highway and Transportation Officials (AASHTO) Accreditation Program (AAP), for analysis with the results of the soil analyses being applied in the scour analysis hydraulic calculations.

Our engineering services included a detailed review of previous documentation for each bridge including original as-built drawing, previous inspection reports, and other National Bridge Inspection Standards (NBIS) reporting. The Phase II detailed scour analysis also included a hydrologic analysis for each road crossing with consequent hydraulic modeling of the bridge structure and stream channel being performed in HEC-RAS. Results from HEC-RAS were then used to conduct additional scour analysis in the Federal Highway Administration Hydraulic Toolbox.