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Barrier wall B1 was modeled to reduce noise impacts to residences along Bentwood Drive, Rollins Court, Brigham Drive, Delhi Road, and Long Shadow Lane.
The barrier was modeled at 7,559 feet in length and was evaluated at 3 fixed heights of 25 feet, 20 feet, and 15 feet.
Feasibility
For all 3 barrier wall height scenarios (25 feet, 20 feet, 15 feet), barrier wall B1 meets the criteria for both acoustic feasibility and engineering feasibility
Since both acoustic and engineering feasibility criteria are met with barrier wall B1, the evaluation continues for reasonableness.
Reasonableness
Noise Reduction Design Goal
Barrier wall B1 of all wall height scenarios (25’, 20’, 15’) meet the noise reduction design goal; therefore, evaluation continues for cost effectiveness.
Cost-effectiveness – cost estimates were prepared for each of the 3 barrier wall height scenarios based on a $35/square foot prescribed cost. This prescribed cost is based on SCDOT’s Noise Abatement Policy. As a reminder, the maximum allowable cost is $30,000 per benefitted receptor.
Barrier wall B1 with 15’ wall height exceeds the allowable $30,000 cost per benefitted receptor; therefore, the evaluation stops and the barrier wall is considered not reasonable to construct.
Barrier wall B1 with 20’ wall height is within the allowable $30,000 cost per benefitted receptor; therefore, evaluation continues. The following slide describes the continuation of this evaluation.
Barrier wall B1 with 25’ wall height exceeds the allowable $30,000 cost per benefitted receptor; therefore, the evaluation stops and the barrier wall is considered not reasonable to construct.
Out of the 3 barrier wall heights analyzed, only barrier wall B1 with a wall height of 20’ meets the initial cost-effectiveness criteria. The project team then prepared a project-specific cost estimate which is described on the following slide.
