So when an underground CMP Pipe SWM facility sits unattended for ten – fifteen? – twenty? years or so, it may be no problem. On the other hand, it can turn into a nightmare. Following is an un-named facility we (Stormwater Maintenance, LLC) are currently working on.

Photo 1 – looking down into the control structure ( a weir wall on the right holding back 6′ of standing water, a 6″ orifice direct below with the nasty stains seeping out.

A quick look-over the weir wall and we see over six feet of standing water. Pretty creepy when standing behind the weir wall. The water completely fills over 400 linear feet of 72″ CMP.

And a look at the clogged orifice…. which was not designed with a trash rack.

This thing was holding back over 6 feet of water.

So a little prodding (not much, mind you!), and she was ripping! We WERE scampering up the manhole ladder!

It took about 8 hours to dewater.

And the result – between 2 and 4 feet of trash and sediment along 400 LF of pipe:

Cost to jet and vac out is unknown as of this writing – but it well into the tens of thousands of dollars.

Moral of the story – an annual inspection would have prevented this!

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