Creek Crossing - Anti Seep Collars?

[esass13]

How important are the concrete anti-seep collars on water mains under a creek crossing? Are they necessary? I've seen many different specs with and without them.

Thanks for the help.

 

[francesca]

We didn't provide any on the sewer forcemain we had in a creek crossing. Presumably the water main will cross perpendicular to the creek, and therefore perpendicular to the flow of ground water under the creek. Antiseep collars in that case wouldn't do anything.

 

[bltseattle]

Seems like a cut-off would still provide function at the top of bank, where the trench starts to slope down the bank, to prevent gravel backfill erosion caused by water percolating into the trench upslope of the stream.