(A) Excavation.
(1) General.
(a) Excavation shall be performed to the lines and grades shown on the plans. The work shall be performed in a safe and proper manner with suitable precautions being taken against all hazards. Excavations shall provide adequate working space and clearances for the work to be performed including the installation and removal of concrete forms. In no case shall excavation faces be undercut for extended footings.
(b) Subgrade surfaces shall be clean and free of loose material of any kind when concrete is placed thereon.
(c) All suitable excavated material meeting the requirements of general fill shall be used as backfill, in the formation of embankments or engineered fill, or for other purposes shown on the plans. All unsuitable material shall be removed from the site unless otherwise allowed by the town. Satisfactory excavated materials shall be stockpiled until required for fill or embankment. Stockpiles shall be graded and shaped for proper drainage.
(d) Excavation work shall be performed in accordance with all applicable provisions of the OSHA standards for excavation safety.
(2) Underground utilities. Utilities shall be located in areas of work prior to commencement of work. If utilities are to remain in place, adequate means of support and protection during earthwork operations shall be provided. Should unknown or unidentified piping or other utilities be encountered during excavation, the contractor shall consult applicable utilities immediately for directions. The contractor shall cooperate with the town and the utility companies in keeping respective services and facilities in operation. The contractor shall repair damaged utilities to the satisfaction of the utility owner.
(3) Sheeting and shoring. Except where banks are cut back on a stable slope, excavation for structures and trenches shall be properly and substantially sheeted, braced and shored, as necessary, to prevent caving or sliding, to provide protection for workers and the work. Sheeting, bracing and shoring shall be designed and built to withstand all loads that might be caused by earth movement or pressure, and shall be rigid, maintaining shape and position under all circumstances. Sheeting and shoring shall comply with all applicable requirements of the OSHA standards for excavation.
(4) Unsuitable bearing material. Materials encountered at design elevations which are considered inadequate for suitable bearing shall be removed and replaced. Removal shall be to a depth as required to reach suitable bearing material. Fill material shall consist of either structural backfill or concrete.
(5) Subgrade stabilization.
(a) Subgrades for concrete structures shall be firm, dense and thoroughly compacted and consolidated; shall be free from mud; and shall be sufficiently stable to remain firm and intact under the feet of the workers.
(b) Subgrades for concrete structures which are otherwise solid, but which become mucky on top due to construction operations, shall be reinforced with crushed stone or gravel. The finished elevation of stabilized subgrades shall not be above subgrade elevations shown on the plans.
(6) Dewatering.
(a) The contractor shall provide and maintain adequate dewatering equipment to remove and dispose of all surface and ground water entering excavations, trenches or other parts of the work. Each excavation shall be kept dry during subgrade preparation and continually thereafter until the structure to be built, or pipe to be installed therein is completed to the extent that no damage from hydrostatic pressure, flotation or other cause will result.
(b) All excavations which extend down to or below static ground water elevations shall be dewatered by lowering and maintaining the ground water surface beneath such excavations a distance of not less than 12 inches throughout the time the excavation remains open.
(c) Surface water shall be diverted or otherwise prevented from entering excavated areas or trenches to the greatest extent practicable without causing damage to adjacent property.
(d) The contractor will be held responsible for the condition of any pipe or conduit which he or she may use for drainage purposes, and all such pipes or conduits shall be left clean and free of sediment.
(e) Water shall be disposed of in such a manner as will not cause injury to public or private property, nor be a nuisance or a menace to the public. The contractor shall be responsible for any and all permits and approvals thereof necessary for disposal of the water.
(B) Backfill and embankment.
(1) Materials. All material placed in fills and embankments shall meet the requirements of general fill as previously defined. No rocks or stones shall be placed in the upper 18 inches of any fill or embankment. Rocks or stones within the allowable size limit may be incorporated in the remainder of fills and embankments; provided, they are distributed so that they do not interfere with proper compaction; except that, no rocks or stones shall be placed in fill area under structures.
(2) Placement.
(a) The backfill and fill materials shall be evenly placed adjacent to structures, piping or conduit to the required elevations. Care shall be taken to prevent wedging action of backfill against structures or displacement of piping or conduit by carrying the material uniformly around the structure, piping or conduit to approximately the same elevation in each lift.
(b) Where fill is required on both sides of a foundation or wall, the fill shall be placed simultaneously on each side. Fill against building walls shall not be placed until the first floor slab has been poured and set.
(c) Fill against other work shall be in a manner and at such time as not to endanger the stability or damage the work. No fill shall be placed against water bearing walls until they have been tested for water tightness. No fill shall be placed over snow or frozen material.
(d) Materials such as brush, hedge, roots, stumps, grass and other organic matter shall not be incorporated or buried in the engineered fill.
(3) Compaction.
(a) Compaction of backfill and embankment material shall be accomplished by mechanical means such as vibratory plates or rollers. Compaction by jetting methods will not be performed unless specifically allowed by the town. No backfill shall be deposited or compacted in water.
(b) Backfill shall be placed in eight-inch loose layers and each layer compacted to not less than 95% of maximum dry density; the moisture content shall be within two percentage points of optimum as determined by ASTM D-698.
(c) Embankment fill shall be placed in eight-inch loose layers and each layer compacted to not less than 98% of maximum dry density. The moisture shall be within two percentage points of optimum as determined by ASTM D-698.
(d) Granular fill under slabs shall be placed after the subgrades have been leveled and cleared of all debris and immediately prior to pouring of the slab. Granular material shall be placed in eight-inch loose layers and each layer compacted to not less than 98% of maximum dry density; the moisture content shall be with two percentage points above optimum as determined by ASTM D-698.
(C) Compaction testing.
(1) Sampling and testing shall be the responsibility of the contractor. Tests shall be performed by an approved commercial testing laboratory or may be tested with approved facilities furnished by the contractor. All test results shall be submitted to the town.
(2) Laboratory tests for moisture-density relations shall be determined in accordance with ASTM D-698. A minimum of one test shall be performed on each different type of material used for backfill.
(3) Field in-place density tests:
(a) The contractor shall perform a sufficient number of compaction density tests to demonstrate that the required compaction requirements are being met. In general, a minimum of one satisfactory compaction test shall be performed for each cumulative lift length of 400 feet. Upon failure of a test, the lift shall be recompacted and retested. Additional tests will be required if the first tests consistently fail, if material changes, or if the contractor’s method of compaction changes.
(b) Density tests shall be determined in accordance with ASTM D-1556, ASTM D-2167 or ASTM D-2922. When ASTM D-2922 is used, the calibration curves shall be checked and adjusted using only the sand cone method as per ASTM D-1556. ASTM D-2922 results in a wet unit weight of soil and when using this method, ASTM D-3017 shall be used to determine the moisture content of the soil. The calibration curves furnished with the moisture gages shall be checked along with density calibration checks as described in ASTM-D3017. The calibration checks of both the density and moisture gages shall be made at the beginning of a job and on each different type of material encountered.
(c) Copies of calibration curves and results of calibration tests shall be furnished to the town.
(2004 Code, Art. I, § A, part 3)