SR 310 Bridge Replacements over Mattie Creek and Nelson Creek

Mendrop Engineering Resources, LLC (MER) was selected by the Mississippi Department of Transportation (MDOT) to provide hydraulic recommendations and bridge plans for the hydraulic crossings of Mattie Creek (Bridge #33.2) and Nelson Creek (Bridge #33.6) on State Route 310 (SR 310). In a separate contract, MER was selected to develop Phase “A” Final Right-of-Way plans for the bridge replacements (Bridges # 33.2 and #33.63) on SR 310 in Panola County.

The Final Right-of-Way plans for the bridge replacements included roadway design, roadway hydraulic design, and wetland delineations for the project of approximately 1.0 miles in length. MER developed 3-D CADD models for the realigned roadway using the latest version of Bentley Geopak. Based on the provided geometric guidelines (RWD600), topographic survey, and the MDOT SS4 Geopak platform, the roadway model was designed to include two bridges, a superelevated roadway, special ditches, and a local road intersection. The model was then utilized in determining Phase “A” Right-of-Way limits for SR 310.

Hydraulic design for the replacement bridge included hydraulic modeling, scour analysis, guide bank design, and stream stability assessment. Hydraulic field surveys and LiDAR data were employed to develop hydraulic models using the U.S. Army Corp of Engineers Hydrologic Engineering Center River Analysis System (HEC-RAS). Scour analysis was performed according to Federal Highway Administration, Hydraulic Engineering Circular No. 18 (HEC-18). Following HEC-20 guidelines, a qualitative geomorphic analysis was performed to help identify stream instability problems at the highway crossing. Riprap protection for bridge abutments was evaluated in accordance with HEC-23, and a riprap rock chute was evaluated in accordance with the USDA, Agricultural Research Service Technical Paper No. 972062. • Phase “A” Conceptual, Preliminary, and Final Bridge Plans • Phase “A” Final Rightof- Way Plans • Hydraulic Bridge Recommendations • Stream Stability Assessment