Retention Basin Plugs

We have a retention basin that collects excess rain runoff water independent of our ponds. The opening at the far side where the runoff eventually feeds into a creek is about a 6 inch circle at ground level that often gets clogged with leaves and requires our landscaper (for an extra fee) to unclog a few times a year when it backs up maybe 4-5 foot-deep water for days. There is also a 2nd drain at around 8 feet off the ground to handle massive runoff. The thing is, we recently took a close look at it and discovered the 6 inch circle is, in fact, part of a bolted-on, removable cover that hides a much bigger (2 foot?) outlet hole in the permanent cement structure. We assume the developer had the temp cover for some reason, though as the 2 foot outlet hole is permanent, we assume we can remove it to speed draining and avoid service calls.

Your thoughts?

Thanks in advance.

John, I know exactly what you are talking about. We have several detention ponds with a similar discharge setup into the two streams that bisect our community. And yes, the grates need to be cleaned several times a year. And when they were not cleaned one year, we had a detention pond overflow that nearly flooded a couple of homes.

My understanding is that these ponds are carefully engineered to control the rate of storm water discharge to control flooding. In our area they are part of a comprehensive storm water management plan that regulates the flow rates and handling capacities of the streams into which they drain.

The size of the cover grate determines the rate at which storm water is discharged. We also have the much larger grate higher up to serve as a back up in extreme situations.

If you are not having any problems, you may simply want to leave well enough alone. You could probably find out more about discharge flow rates and requirements through your county government. They may even have a inspector that could come out and take a look, and answer questions.

Alternately, you might be able to find the developer's site plans that may show what kind of discharge flow rates and grate sizes that are mandated.

Detention ponds do require ongoing maintenance. You can't ignore them. Keep those grates clean, particularly after the leaves fall in November and December.

Thanks all, as always, for your comments.

I called the Township (our local governing body), found the right man for the job, and asked the question. He said he'd get back to me. Which he did in less than hour!

Our site plan demonstrates the panel is meant to be permanent, the small opening planned for...here he calmly rattled off a bunch of technical stuff...to constrict the drainage into the creek.

And as a friendly aside, he noted removing it could result in.......as soon as I heard 10 days in prison, I was sold!

Kirk,

Agree. And we do dry raking when things build up. The trouble is when we get a heavy rain. Stuff washes down from hundreds of yards away, starting from a huge corn field. So aside from leaves, we also get stalks, twigs, whatever, which arrive within the hour.

I guess we'll need a bigger, submersible rake and hip=waders, or just call the landscaper.