1806.2.3 Uncontrolled fills.

Fills other than controlled fill may be considered as satisfactory bearing material of applicable class, subject to the following:

   1.   Where spread footings will be used, the soil within the built-up area shall be explored using test pits at every column. All test pits shall extend to depths equal to the smaller width of the footing and at least one test pit shall penetrate at least 8 feet (2438.4 mm) below the level of the bottom of the proposed footings. All test pits shall be backfilled with properly compacted fill. Borings may be used in lieu of test pits, provided that continuous samples of at least 3 inches (76.2 mm) in diameter are recovered. Where mat foundations will be used, one test pit or minimum 3 inch (76.2 mm) diameter sampler boring shall be provided for every 1,000 square feet (92.9 m 2 ) of building footprint area. For continuous concrete footings, one test pit or minimum 3 inch (76.2 mm) diameter sampler boring shall be provided for every 25 linear feet (7620 mm).

   2.   The building area shall be additionally explored using one standard boring for every 2,500 square foot (232.3 m 2 ) of building footprint area. These borings shall be carried to a depth sufficient to penetrate into natural ground, but not less than 20 feet (6096 mm) below grade.

   3.   The fill shall be composed of material that is free of voids and free of extensive inclusions of mud and organic materials such as paper, wood, garbage, cans, or metallic objects and debris.

   4.   The allowable soil bearing pressure on satisfactory uncontrolled fill material shall not exceed 2 tons per square foot (191.5 kPa). One and two-family dwellings may be founded on satisfactory uncontrolled fill provided the dwelling site has been explored using at least one test pit, penetrating at least 8 feet (2438.4 mm) below the level of the bottom of the proposed footings, and the fill has been found to be composed of material that is free of voids and generally free of mud and organic materials, such as paper, garbage, cans, or metallic objects, and debris. Test pits shall be backfilled with properly compacted fill.

1806.2.4 Artificially treated soils.

Nominally unsatisfactory soil materials that are artificially compacted, cemented, or preconsolidated may be used for the support of buildings, and nominally satisfactory soil materials that are similarly treated may be used to resist soil bearing pressures in excess of those indicated in Table 1806.1. The engineer shall develop treatment plans and procedures and post-treatment performance and testing requirements, and submit such plans, procedures, and requirements to the commissioner for approval. After treatment, a sufficient amount of sampling and/or in-situ tests shall be performed in the treated soil to demonstrate the efficacy of the treatment for the increased bearing pressure.

Section BC 1807: Retaining Walls and Other Retaining Structures

1807.1 General.

Retaining walls shall be designed in accordance with Section 1807.2.

1807.2 Design.

Retaining walls shall be designed to ensure stability against overturning, sliding, excessive foundation pressure and the effects of water pressure, including uplift. Where a keyway is extended below the wall base with the intent to engage passive pressure and enhance sliding stability, lateral soil pressures on both sides of the keyway shall be considered in the sliding analysis.