Cofferdam for 4', 8' and 12' diameter tanks

A hole shoring device, comprising:

• a) a support frame supportable on an area around a hole;
• b) a plurality of concentrically disposed hollow octagonal shaped sleeves disposed below said support frame and positionable in the hole, each of said plurality of concentrically disposed hollow octagonal shaped sleeves being removably mounted within a previous one of said plurality of concentrically disposed hollow octagonal shaped sleeves and extending downwardly therefrom;
• and
• c) linkage removably connecting said plurality of said concentrically disposed hollow octagonal shaped sleeves to said frame and to each other.

A method of using a hole shoring device, comprising the steps of:

• a) excavating a pilot hole to a depth of 5';
• b) installing a crib of said hole shoring device on an area outside said pilot hole;
• c) installing a support frame of said hole shoring device on said crib;
• d) setting a hollow first octagonal shaped sleeve of said hole shoring device in said pilot hole;
• e) lowering said hollow first octagonal shaped sleeve to a depth of 5.33';
• f) connecting a frame linkage arrangement of said hole shoring device to said support frame and said hollow first octagonal shaped sleeve;
• g) setting a hollow second octagonal shaped sleeve of said hole shoring device inside said hollow first octagonal shaped sleeve;
• h) excavating a second sleeve hole below said pilot hole;
• i) lowering said hollow second octagonal shaped sleeve into said second sleeve hole to a depth of 10.33';
• j) connecting a first linkage arrangement of said hole shoring device to said hollow first octagonal shaped sleeve and said hollow second octagonal shaped sleeve;
• k) setting a hollow third octagonal shaped sleeve of said hole shoring device inside said hollow second octagonal shaped sleeve;
• l) excavating a third sleeve hole below said second sleeve hole;
• m) lowering a hollow third octagonal shaped sleeve of said hole shoring device into said third sleeve hole to a depth of 15.33';
• n) connecting a second linkage arrangement of said hole shoring device to said hollow second octagonal shaped sleeve and said hollow third octagonal shaped sleeve;
• o) setting a hollow fourth octagonal shaped sleeve of said hole shoring device inside said hollow third octagonal shaped sleeve;
• p) excavating a fourth sleeve hole below said third sleeve hole;
• q) lowering said hollow fourth octagonal shaped sleeve into the fourth sleeve hole to a depth of 20.33';
• r) connecting a third linkage arrangement of said hole shoring device to said hollow third octagonal shaped sleeve and said hollow fourth octagonal shaped sleeve;
• s) installing a filter fabric to the top of said hollow fourth octagonal shaped sleeve with a 9" overlap;
• t) installing gravel, a bottom slab, and a drain ring section in said hollow octagonal shaped sleeve to a height of 2';
• and
• u) positioning a tank in said excavation.