Job Story
Pucillo Construction Co.Newbury Park, California
8" sewer line and man hole - 120 linear feet 9' deep.
Equipment used: Cat 330bl w/HRC120 cutter attachment in trenching mode (cutter spins towards the excavator or spins the in the direction of the trench).
The trench was down the center of an asphalt road and needed to be at least 30" wide at depth (9 feet). The rock was 8000psi Conejo Volcanic and layers of Basalt or (Blue Rock) at 11000 to 13000psi. The back fill on the trench was two sack slurry. The trench was cut in one pass.
The Bottom Line - cutter vs breaker:
The 83 cu/yds of Spoils from the grinding operation were found to be suitable for backfill on a retaining wall Pucillo Construction was also building on site. Had a breaker been employed to cut the trench the resulting spoils could not have been reused on site, but would have had to be removed. Pucillo estimated this alone saved them $2000.
Because the cutter is able to grind a straight sided trench down to depth there is no need to 'layback' the sides as is necessary with a breaker. This means that when it came time to backfill, the contractor was able to reduce the amount of the 2 sack slurry needed. This represented an additional savings of $5000.
Also Because there was no layback the contractor needed to rent just 9 - 4' x 12' steel plates, placed end to end, to cover the opening in the street, rather than 25 plates placed side by side to cover the wider opening that would have been left by a breaker. A nearly 2/3 cost savings on the rental cost as well as the machine time and manpower needed to place them.
The 30" trench top also meant that clean out could be accomplished with on site standard backhoe equipment and far less asphalt to repave the road when the work was done.
The contractor realized cost savings of at least $5000 by using the cutter attachment on this job and likely more.