Abandon an existing manhole 2

[redbridge]

I am working on a sewer line replacement project and I was wanting to know the proper way to abandon an existing manhole. I was thinking of plugging the sewer line with concrete, remove the top manhole ring and fill the manhole with no. 57 gravel except for the last 2 feet which would be top soil. Please let me know if there is a better way to do this.

 

[francesca]

If you filled it with gravel and topsoil, you'd be creating a large, buried bucket.

How deep is the manhole and will the sewer continue as a solid pipe through the manhole or near by? Or is the sewer line being abandoned too?

 

[redbridge]

There will be about 40 manholes that are going to be abandoned that range from 4 feet to 15 feet deep. The sewer line is being abandoned too.

 

[bimr]

I did something very similar with a lift station.

I asked the contractor to drill some holes in the bottom of the lift station for drainage, remove the top 3 feet of the structure, and then backfilled the lift station with aggregate.

If you have a deep manhole, you would require a large hole if you wanted to completely remove the structure. You would have to replace more pavement and worry about adjacent structures. That is expensive and unnecessary.

 

[nackra]

I have used CALTRANS spec:

15?2.05A Frames, Covers, Grates, and Manholes

? When existing manholes or inlets are to be abandoned, pipes entering the manhole or inlet shall be securely closed by a tight fitting plug or wall of minor concrete not less than 150-mm {0.5-foot} thick, or by a tight brick wall not less than 200-mm {0.67-foot} thick with cement mortar joints. Minor concrete shall conform to the provisions in Section 90-10, "Minor Concrete." The bases of manholes or inlets shall be broken in a manner to prevent entrapment of water. The manhole or inlet shall be demolished to an elevation one meter {3.5 feet} below finished grade and backfilled in conformance with the provisions in Section 19-3.06, "Structure Backfill."

Good luck