Sounds bogus to me, I would make you prove that.  I would guess water takes somewhere around a nanosecond or two to enter and pass through a catch basin.

Engineering is the practice of the art of science - Steve

Sniff - Sniff...smells like fertilizer.  The incoming water has to reach a point where the catch basin will discharge (if there is any storage).  Depending on the rate of inlow, this could be a couple of seconds to a couple of minutes.  Once the flow is going out, your Tc through the basin is essentially zero.

Do you mean catch basin or detention/retention basin?  Detention basins can increase times of concentration for hours.

Crystal has a point - catch basin is usually an inlet.
The detention/retention basin or pond will hold water, and could make an impact.

Your pipe flow time may be used in the Tc, but it won't be very much time.  

Thanks for the input. I was in a teleconference on detention basin design and the presentor specifically stated that 5-15 min. inlet concentration times could be added to the time of concentration. I had not ever heard that before and it seems like is it not a reasonable assumption.

The travel time for a lake or reservoir can be estimated by:

Tt = L / V

where V = sqrt( g D )

Tt = Travel time (seconds)
L = Flow length
V = wave velocity
g = gravitational constant
D = mean depth

I wonder if the presentor was refering to the minimum Tc of 5 minutes commonly used in Rational method calculaitons.

The overland travel time (time to reach the inlet) for a one acre parking lot will be about 100 ft/2fps = 50 seconds. For this reason computer models that require a minimum Tc of 5 minutes are inherently invalid.
The Rational Method was never intended to be used with Tc --this misconception was invented in 1890.
The Rational Method uses the IDF correlations that estimate the ability of a raincloud to generate rainfall. This ability is determined by rain gage data.
The minimum duration for IDF correlations is 5-minutes. This duration can be used as long as the pipe network travel time is less than 5 minutes. For example, a 1000-ft long storm sewer flowing at 3.3 fps has a travel time of 5 minutes.
Rational Method Runoff coefficients can be reduced to allow for ponding and/or the longer travel time for heavily vegetated areas.