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.
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!
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!