Location: The proposed project is located near US-70 in Section 2, Township 5 South, Range 8 West, on Beaver Creek, in Waurika, Jefferson County, Oklahoma. The project site can be found on the Waurika West, Oklahoma 7.5 Minute USGS Quadrangle map at North Latitude 34.158531 and West Longitude 98.007166.
Project Description: This proposed bank protection project (ODOT Job Piece 34260(04)) is designed to eliminate a large scour hole within Beaver Creek that is threatening the US-70 bridge. The application is for the construction of two Turf Reinforcement Mats (TRM) with appurtenant features and rock riprap to provide a resilient channel with restored stream function to reduce erosion and instability. Soil fill material consisting of unclassified borrow topsoil would also be used for grade sloping and bedding for the TRM. The proposed improvements to Beaver Creek (scour hole) would consist of three primary components for restoration of stream channel and bed: 1) Rock Riprap, 2) TRM, and 3) Installation of Sheet Pile Structures and Cap (SPSC).
Purpose: The proposed project would provide long-term protection against channel erosion and bank instability while restoring stable channel functions. The overall purpose of this work is to prevent the loss of the existing bridge and roadway and make sure that this portion of US-70 Highway is safe for public transportation. The project is not a water dependent activity.
Description of Work: The applicant proposes to place fill material that results in permanent impacts to 0.44 acre (171 linear feet) of Beaver Creek using SPSC (65 cubic yards) for construction. The project would also include rock riprap (1,258 cubic yards), unclassified borrow topsoil (290 cubic yards), and TRM (177 cubic yards).
SPSC: Both SPSC includes metal sheet pilings and is capped with concrete. Each SPSC would be driven below ground to an estimated depth between 18 and 32 feet. The concrete cap would be approximately 1.5 feet tall and 2 feet wide. The top of the structure would match the proposed grade of the new channel bed. Each SPSC would be placed perpendicular to the channel from streambank to streambank, which is approximately 130 feet wide.
Rock Riprap: The various sized rock riprap would be used to form a stable channel bed at the upstream and downstream of each sheet pile structure. Additional various sized rock riprap would be placed at depths of 2 and 6 feet within the existing scour hole located between the upstream and downstream sheet pile structures.
TRM: TRM would be used to promote establishment of vegetation along the restored banks of Beaver Creek. ODOT proposes to restore streambanks by grading a 2:1 slope and placing TRM on top of the earthen grading. Following the installation of TRM, 5 inches of topsoil would be evenly spread to serve as a growth medium for drought resistant herbaceous vegetation.
Temporary Fill: Temporary fill would be utilized for the temporary earthen coffer dam and temporary erosion control rock check dams. The estimated volume of the temporary earthen coffer dam is approximately 80 cubic yards. The estimated volume of the rock check dam is approximately 20 cubic yards. The ODOT’s construction contractor would be required to maintain low-flow conditions through the project area, implement best management practices for water quality, and remove the temporary fill following completion of the proposed improvements.
The work would be performed using conventional earthmoving equipment such as excavators, wheeled dump trucks, and tracked equipment.
Due to active/ongoing erosion occurring between the time that design is conducted, and construction begins, the site conditions during construction are anticipated to be different than current existing condition. The scour hole could be larger than the ODOT design before construction. The extension of the TRM could be further up the bank to provide additional stabilization within the newly graded areas.