Tc for roadway

[cvg]

Anyone ever heard of an agency requiring a 60 minute Tc for each catch basin on an urban roadway? C values are all 0.95 for pavement and design is for a 10-year storm. I am speculating that this was a blunder by the engineer doing the report as it appears to underestimate peak runoff and water quality volumes by about a factor of 3.

 

[civilperson]

This is a lesser requirement than normal time of concentration. I agree in a junior engineer wonder blunder. Had similar mistake in Carson City and then the senior Engineer enforced normal Q volumes for all inlets and pipes.