Raising the inside floor of a Catch Basin 2"

Question

Raising the inside floor of a Catch Basin 2"

Aggie83 (Civil/Environmental)

(OP)

9 Jul 19 17:36

Hello - this may be very trivial but I have a project in construction where we need to raise the outflow pipe going into an existing 36" precast catch basin (re-routing site storm around a new structure and in order to make up the delta in slope within the system, we are reducing the "drop" within this particular existing catch basin. In order to avoid 2" of standing storm water at the bottom, I was thinking the contractors could grout the bottom up to the invert of the new outflow pipe. Will this work for this application? Is there an industry standard? This is privately-maintained storm drain on a college campus. The District has bare bones construction standards/specifications.

Any help would be appreciated! Thanks!
NR

darthsoilsguy2 (Geotechnical) · Answer 1 · 2019-07-09 22:17:50

Most standard catch basin designs i've seen include a sump below the outflowing pipe so there is always stormwater standing in the basin. Our standard detail is 24" sump. This gives you a reservoir for sand, gravel, heavy debris, etc... so that routine maintenance can be done by periodically cleaning basin sumps alone... instead of cleaning basins AND the lines between them. Have you considered being 'OK' with the small amount of standing water?

If this was a sanitary sewer manhole (instead of a stormwater catch basin), i would say grout it up.

Ekenedilichukwu (Civil/Environmental) · Answer 2 · 2019-09-27 16:56:52

Normally you will need to have a drop or sump of 2-in or more between storm drain inflow and outflow, but in your case i think it should be ok.
This should work fine.

gbam (Civil/Environmental) · Answer 3 · 2019-09-30 15:48:26

Make sure to check your regulations and design criteria for the agency that will approve the design.

Cairo Datum (Civil/Environmental) · Answer 4 · 2019-10-26 01:29:34

Where I'm at it's standard to use flowable fill when abandoning structures but lightweight concrete for this type of application. We had to raise the bottom of a manhole 3 ft once and used lightweight concrete. But yes, like the others said with this small of an invert change just leave the sump as is.

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Raising the inside floor of a Catch Basin 2"