706.01 Structural Timber and Lumber
Furnish timbers and lumber being:
A.Standard sawn Douglas fir, larch, or southern yellow pine. Coastal and intermountain varieties of Douglas fir are allowed. See additional treatment requirements for intermountain Douglas fir in Subsection 706.04.2.
B.Graded under the current West Coast Lumber Standard Grading Rules or the Western Lumber Grading Rules.
C.Grade stamped by an American Lumber Standards certified inspection agency. The recommended design values under the rules for grading timbers and lumber grades cannot be less than those shown in the contract for the required minimum timber stress. Note the grade, the grading rule, and the recommended design stress value for that rule on the shop drawings for each size. Use only pieces of sound wood free from all decay. When untreated timber is specified, it must show at least 85% heartwood on the girth, measured where the least amount of heartwood occurs on any girth. When treated timber is specified, there are no heartwood requirements, and the sapwood amount is not limited.
706.02 Reserved
706.03 Poles and Posts
Furnish the poles and posts in accordance with the contract.
706.04 Treated Timber and Lumber
Furnish structural timber and lumber treated with a wood preservative specified as follows.
706.04.1 Treating
Furnish timber and lumber that is pressure treated meeting the preservative retention and penetration requirements found in AWPA Standards U1 and T1, Commodity Specification A, B or D, use category 4A, appropriate for the application of material. Use one of the following preservatives:
1.Ammoniacal Copper Zinc Arsenate (ACZA) meeting AWPA Standard P22.
2.Chromated Copper Arsenate, Type C (CCA) meeting AWPA Standard P23.
3.Copper Naphthenate Solvent Type A (CuN) meeting AWPA Standard P36.
4.5% by weight solution of Pentachlorophenol Solvent Type A (PCP-A) meeting AWPA Standards P35.
5.4,5-Dichloro-2-N-Octyl-4-Isothiazolin-3-One (DCOI) meeting AWPA Standard P39. Treated timber or lumber to receive paint must permit the paint to adhere to the treated surface without discoloration. Meet AASHTO M 133 requirements for all preservatives and their sampling and testing methods. Treat injuries, cuts, and holes in wood after treatment with 3 applications of ACZA or copper naphthenate solution containing a minimum of 2% copper metal meeting AWPA M4 requirements. 706 – TREATED AND UNTREATED TIMBER 2020 EDITION V5.1 706-2
706.04.2 Incising
Mechanically incise timber and lumber as specified in Section 8 of Commodity Specification A, part 12 of AWPA Standard T1 having a nominal thickness of 2 inches (actual 38 mm thickness) or greater before treating. Incise timber and lumber 3 inches (63 mm actual thickness) thick or greater on all four sides. Incise timber and lumber less than 3 inches (63 mm actual thickness) thick on the wide faces only, unless otherwise specified. Ensure incision depth and pattern for all material are dense enough to achieve uniform depth of penetration as specified in Section 8 of Commodity Specification A, part 12 of AWPA standard T1. Incise intermountain Douglas fir and treat to refusal with preservative. Meet retention requirements in AWPA standards listed in 706.04.1 . Refusal is defined as maintaining pressure and temperature or increasing pressure and temperature, within a range that is good practice for the material being treated, until the quantity of preservative absorbed in each of any two consecutive half hours in not more than 2% of the amount already injected. 1½-inch (38 mm actual dimension) center-matched material used for flumes, boxes, etc., does not need to be incised. Ensure incised wood meets the penetration and retention requirements appropriate for the identified Use Category Commodity Specification.
706.04.3 Inspection
Wood products will be inspected in accordance with MT 404. Wood products with worm holes and any staining due to fungus will be inspected in the white. Moisture content of intermountain Douglas fir will also be inspected in the white. Provide the Department a minimum of 72 hours advanced notice for inspection in the white. Wood products must be traceable from inspection in the white to inspection of the treated product. If stain is present in the wood, use only material with blue stain. The correct moisture content for Intermountain Douglas Fir is 22% ± 2% and the method to obtain this moisture content is outlined in the AWPA standards. The acceptance of any material or finished members by the Inspector does not prevent their rejection if found defective. Replace rejected material and work at Contractor expense.
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Source: Standard Specifications for Road and Bridge Construction, 2020 (v5.1) Edition. Pages 559–560 of 611. View official source ↗