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The sides of all excavations, including related or resulting embankments, that are 5 feet (1524 mm) or greater in depth or height measured from the level of the adjacent ground surface to the deepest point of the excavation, shall be protected and maintained by shoring, bracing, sheeting, sheet piling, or by other retaining structures as may be necessary to prevent the sides of the excavation from caving in before permanent supports are provided. Such methods of protection shall be subject to special inspection in accordance with the provisions of Chapter 17.

Alternatively, excavation sides may be sloped not steeper than 45 degrees or stepped so that the average slope is not steeper than 45 degrees with no step more than 5 feet (1524 mm) high, provided such slope does not endanger any structure, including subsurface structures. Deviation from the foregoing limitations for cut slopes shall be permitted only upon the completion of a soil investigation report acceptable to the commissioner.

Exception: Rock cut excavation.
3304.4.1.1 Sheet Piling and Bracing
Sheet piling and bracing used in trench excavations shall be at least equivalent in strength to that specified in Tables 3304.4.1.1(1) and 3304.4.1.1(2).

TABLE 3304.4.1.1(1)
MINIMUM SIZES OF TIMBER BRACING AND TIMBER SHEET PILING FOR TRENCHES 4 FEET WIDE OR LESSa
SHEET PILING STRINGERS CROSS BRACING
Depth of trench
(ft.)
Size
(in.)
Horizontal,spacing
(ft.)
Size
(in.)
Vertical spacing
(ft.)
Size
(in.)
Horizontal spacing
(ft.)
Hard and solid soild
5-10
10-15
More than 15
2 x 6
2 x 6
2 x 6
6
4
tight
2 x 6
2 x 6
4 x 8
6
4
6
2 x 6
2 x 6
4 x 8
6
4
6
Soil likely to crack or crumble
5-10
10-15
More than 15
2 x 6
2 x 6
2 x 6
3
2
tight
2 x 6
2 x 6
4 x 10
5
4
4
2 x 6
2 x 6
4 x 10
5
4
6
Soft, sandy filled-in loose soil
5 - 10
10 - 15
More than 15
2 x 6
2 x 6
2 x 6
tight
tight
tight
4 x 6
4 x 6
4 x 12
6
5
4
4 x 6
4 x 6
4 x 12
6
6
6
Where hydrostatic pressure exists
Top 10
More than 10
2 x 6
3 x 6
tight
tight
6 x 8
6 x 10
4
4
6 x 8
6 x 10
6
6

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
Note for Table 3304.4.1 (1): A steel sheet piling and bracing of equivalent strength may be substituted for wood sheet piling and timber bracing.


TABLE 3304.4.1.1(2)
MINIMUM SIZES OF TIMBER BRACING AND TIMBER SHEET PILING FOR TRENCHES 4 TO 8 FEET WIDEa
SHEET PILING STRINGERS CROSS BRACING
Depth of trench
(ft.)
Size
(in.)
Horizontal,spacing
(ft.)
Size
(in.)
Vertical spacing
(ft.)
Size
(in.)
Horizontal spacing
(ft.)
Hard and solid soild
5-10
10-15
More than 20
2 x 6
2 x 6
2 x 6
6
tight
tight
4 x 6
6 x 6
6 x 8
4
4
4
4 x 6
6 x 6
6 x 8
6
6
6
Soil likely to crack or crumble
5-10
10-120
More than 20
2 x 6
2 x 6
2 x 6
3
tight
tight
4 x 6
6 x 6
6 x 8
4
4
4
4 x 6
6 x 6
6 x 8
6
6
6
Soft, sandy filled-in loose soil
5 - 10
10 - 20
More than 20
2 x 6
2 x 6
2 x 6
tight
tight
tight
4 x 6
6 x 6
6 x 8
4
4
4
4 x 6
6 x 6
6 x 8
6
6
6
Where hydrostatic pressure exists
Top 10
More than 10
2 x 6
3 x 6
tight
tight
6 x 8
6 x 10
4
4
6 x 8
6 x 10
6
6

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
Note for Table 3304.4.1 (2): A steel sheet piling and bracing of equivalent strength may be substituted for wood sheet piling and timber bracing.

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