detention basin

[tsli001]

Hi guys:

I got a question regarding detention basin. A contractor come to us saying that water has spill out of berm of the detention basin we design. I went back check my design. the Hydr. part is good enough for 100 years storm, the basin side slope is 3 to 1, and just completed this winter. I was wondering how many different ways that the contractor can mess it causing the water spill out of the detention basin.

thanks guy

 

[francesca]

We had it happen once when logs and debris had blocked the outlet. Has an as-built survey been completed to check the basin volume and stage-storage capacity?

 

[cvg]

not all possibilities are the contractors fault...

contractor could have made it too small, or
contractor could have left a low spot in the berm, or
contractor didn't compact berm well and it settled, or
contractor didn't compact berm well and water piped through causing breach, or
gopher tunneled through the berm, causing a leak, or
outlet pipe could have plugged up, or
hydrology was incorrect, or
you had a 100-year storm, or
you had back to back storms, or
infiltration estimate / perc tests were overstated, or
runoff was diverted from another watershed into your basin, or
skateboarders used the berm for a ramp and wore it down, creating a low spot, or...

 

[singingk]

addition to cvg...
There are even detention and infiltration bassins without any overflow, planned without any doubt about the hydraulic and geotechnical assumptions made for planning...

 

[newnickname]

After confirming the as-built, I would check the pre-developed time of concentration and see how accurate it may be.