What is the detention time in minutes for a basin of 40 feet by 30 feet with a flow of 3 MGD?

To determine the detention time for a basin, we need to calculate the volume of water in the basin and then find out how long it takes for the flow to completely pass through this volume given the flow rate.

First, calculate the volume of the basin. The surface area can be determined from the dimensions provided (40 feet by 30 feet), giving:

[

\text{Area} = \text{Length} \times \text{Width} = 40 , \text{ft} \times 30 , \text{ft} = 1200 , \text{ft}^2

]

Next, to find the volume of water, we need to know the average depth (the question does not provide this, but for the purpose of calculations, we can assume a reasonable depth based on standard practices or scenarios). For illustrative purposes, let’s say it’s a depth of 5 feet (you can replace this value based on the scenario). The volume in cubic feet would then be:

[

\text{Volume} = \text{Area} \times \text{Depth} = 1200 , \text{ft}^2 \times 5 , \text{ft