Aluminum hydraulic shoring guidance

Yes — you may use the Appendix D tables when the trench is 20 feet deep or less and the conditions match the scope and limitations in Appendix D. Appendix D states it “must be used when design of the aluminum hydraulic protective system cannot be performed in accordance with [1926.652(c)(2)]” and limits use to trenches that do not exceed 20 feet in depth; it also requires you determine the soil type per the soil-classification method in Appendix A. See the Appendix D aluminum hydraulic shoring guidance and [1926.652(c)](https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.652#1926.652(c) for related design requirements.

You must classify the soil using the soil classification method in Appendix A to Subpart P before using the tables. Appendix D explicitly requires determining the soil type with the soil-classification method in Appendix A of Subpart P so you use the correct table (Type A, B, or C). See Appendix D to Subpart P of Part 1926 for this requirement.

Tables D-1.1 and D-1.2 cover vertical shore selections for Type A and Type B soils respectively for trenches up to 20 feet deep. Appendix D explains that Tables D-1.1 and D-1.2 are for vertical shores in Types A and B soil and are limited to the tabulated depths (note: for trench depths over 20 feet you must refer to 1926.652(c)(2). See the Appendix D aluminum hydraulic shoring guidance for the specific table values.

Tables D-1.3 and D-1.4 provide selection data for horizontal waler systems in Types B and C soils, and you must use a waler system when the soil type and need for sheeting indicate it. Appendix D states that Type B soils that may require sheeting and Type C soils that always require sheeting are found in the horizontal wale tables (D-1.3 and D-1.4), so use those tables when sheeting is required. See the Appendix D aluminum hydraulic shoring guidance and [1926.652(c)](https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.652#1926.652(c) for design references.

A 2-inch inside-diameter cylinder must have a safe working capacity of at least 18,000 pounds axial compressive load at maximum extension, and a 3-inch inside-diameter cylinder must have at least 30,000 pounds axial compressive load at the manufacturer's recommended extensions. Appendix D specifies these minimum cylinder capacities and that maximum extension includes the full recommended extension range. See Appendix D to Subpart P of Part 1926 for the cylinder capacity requirements.

When the tables call for 2-inch cylinders at the specified trench widths and spacings, Appendix D requires structural steel tube oversleeves of 3.5 × 3.5 × 0.1875 (or manufacturer's specified structural oversleeves) extending the full collapsed length. Appendix D notes this requirement in the general notes to the tables. See Appendix D to Subpart P of Part 1926 for these oversleeve specifications.

All spacing in the Appendix D tables is measured center-to-center. Appendix D explicitly states, “All spacing indicated is measured center to center.” See the Appendix D aluminum hydraulic shoring guidance for this note.

Vertical shoring rails must have a minimum section modulus of 0.40 cubic inches. Appendix D lists this minimum as a general note to the D-1 tables. See the Appendix D to Subpart P of Part 1926 for the requirement.

No — plywood is not intended as a structural member; it is intended only to prevent local raveling between shores. Appendix D specifically states that plywood is used to prevent local raveling (sloughing) of the trench face and is not a structural member. See the Appendix D aluminum hydraulic shoring guidance for this clarification.

Appendix D specifies 1.125-inch thick softwood plywood or 0.75-inch thick, 14-ply arctic white birch plywood for preventing local raveling behind shores. The appendix lists these thicknesses and materials in the table footnotes. See the Appendix D to Subpart P of Part 1926 for the plywood specifications.

When vertical shores are used, there must be a minimum of three shores spaced equally, horizontally, in a group. Appendix D includes this as a general note to the tables. See the Appendix D aluminum hydraulic shoring guidance for the requirement.

The tabulated members are inadequate and you must use another design under [1926.652(c)](https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.652#1926.652(c) when any of these conditions exist: a) vertical loads on cross braces exceed a 100‑pound gravity load distributed on a one‑foot section of the cylinder center; b) surcharge loads come from equipment weighing more than 20,000 pounds; or c) only the lower portion of a trench is shored while the remaining portion is sloped or benched unless the sloped portion is gentler than 3 horizontal to 1 vertical or members are selected based on depth measured from the top of the overall trench. Appendix D lists these limitations and refers you to 1926.652 for alternative design requirements. See Appendix D and [1926.652(c)](https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.652#1926.652(c).

Select cylinder diameter and spacing from the table that matches the soil type after determining the trench depth and width; the tables list maximum horizontal and vertical spacings for each cylinder size and member section modulus. Appendix D explains that you first determine soil type (Appendix A), choose the appropriate D-1 table for that soil type, then read across the depth and width rows to find the allowed cylinder size and maximum spacings (vertical spacing is held at 4 feet in many table entries). See Appendix D to Subpart P of Part 1926 for the tables and selection instructions.

If a trench is deeper than 20 feet, you must refer to design requirements in 1926.652(c)(2) and 1926.652(c)(3), because Appendix D tables only cover trenches up to 20 feet and note that for depths in excess of 20 feet you must use those provisions. See Appendix D and 1926.652(c)(2).

Treat it as the soil type that best matches the field conditions and use the appropriate table for that type; Appendix D gives an example where previously disturbed Type B soil with Type C characteristics requires sheeting and selection from the Type C (waler) table. Appendix D emphasizes classifying the soil per Appendix A and using the correct D-1 table for the observed soil behavior. See the Appendix D aluminum hydraulic shoring guidance.

Plywood is required only to prevent local raveling of the trench face between shores and is not a structural member; Appendix D also specifies plywood thickness (1.125 in. softwood or 0.75 in. 14‑ply birch) and indicates when it should be used in the table footnotes (for example, when minor raveling is present). Use the table footnotes to determine when plywood is required and how closely it must be spaced vertically. See Appendix D to Subpart P of Part 1926 for these notes.

You cannot exceed the maximum horizontal spacing listed in the applicable table without a site‑specific design; to get greater spacing you must either consult the manufacturer’s tabulated data used per 1926.652(c)(2) or have a design by a qualified person under 1926.652(c). Appendix D includes examples showing alternative wale section moduli and cylinder sizes that permit greater spacing, but you must stay within the table limits or use an engineered design. See Appendix D and 1926.652(c)(2).

Wales in Appendix D are calculated for simple span conditions, and the tables list required section moduli; Appendix D otherwise directs you to consult the product manufacturer or a qualified engineer for the actual section modulus of available wales. Appendix D includes a note stating wales are calculated for simple span conditions and includes an asterisk telling users to consult the manufacturer for section modulus data. See the Appendix D aluminum hydraulic shoring guidance for this instruction.

If part of the trench is sloped and the other portion is shored, you must select members from the tables using a depth measured from the top of the overall trench (not from the toe of the slope), unless the sloped portion is less steep than 3 horizontal to 1 vertical. Appendix D explicitly says members must be selected for a depth determined from the top of the overall trench unless the slope is gentler than 3:1. See Appendix D to Subpart P of Part 1926 and [1926.652(c)](https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.652#1926.652(c) for related provisions.

Vertical spacing is held constant at 4 feet on center in the Appendix D vertical shore tables, though the tables present maximum vertical spacings according to depth and system type. Appendix D explains that in the tables the vertical spacing is held constant at four feet on center and shows the maximum horizontal spacing for cylinders. See Appendix D for the table notes.

Consult a qualified engineer or the product manufacturer when your job conditions are not covered by the Appendix D tables (including trenches deeper than 20 feet, unusual surcharge or vertical loads, nonstandard soil conditions, or when manufacturer tabulated data is needed per 1926.652(c)(2)). Appendix D states it does not apply to every field situation and that systems for conditions not covered by the data must be designed under 1926.652(c). Also consult manufacturers for waler section modulus data. See Appendix D and 1926.652(c)(2).