(a) Excavations.
(1) Generally. During the excavation operations, material suitable for backfilling shall be piled in an orderly manner at a sufficient distance from the banks of the trench to avoid overloading and to prevent slides or cave-ins. All excavated material not suitable and/or required for backfill shall be removed and disposed of in an approved manner. Such grading shall be done as may be necessary to prevent water from flowing into trenches or other excavations, and any water accumulating therein shall be removed by approved methods. All excavations shall be made by open cut unless otherwise specified.
(2) Trench excavations. The trench shall not be opened for a distance exceeding 300 feet at any time when located along streets or highways. The width of the trench at any point below the top of the pipe shall not exceed the structural design assumption width. The width of the trench above the top of the pipe may be as wide as necessary for sheeting and bracing and the proper performance of the work. All trench walls shall be kept as nearly vertical as possible. Excavation at manholes and similar structures shall be sufficient to leave at least twelve inches clear between their outer surface and the embankment or sheeting. Minimum clearance between the sides of the trench and pipe shall be eight inches.
(3) Rock excavations. In rock, the minimum width of the trench shall be the outside diameter of the pipe plus twelve inches, and there shall be a minimum of six inches of sidewall clearance between the pipe and rock at all points. The maximum width of the trench at any point below the top of the pipe shall not exceed the structural design assumption width. The rock shall be excavated to a minimum overdepth of ten inches, or as required for class of bedding, whichever is greater, below the outside bottom of the pipe. Before laying pipe in rock trenches, the trench shall be refilled with suitable material of an approved quality, thoroughly consolidated, up to the proper elevation to provide a foundation as required in subsection (b) hereof for laying the pipe.
(b) Pipe Foundations.
(1) Pipe installed in trenches. Pipe to be located at elevations below the existing ground level shall be installed in trenches with Class A, B or C pipe bedding as shown in Figure II following this chapter. Granular material under and around the pipe shall be placed in six-inch layers and compacted by rodding, spading or with approved vibratory equipment to obtain not less than eighty percent relative density as determined by A.S.T.M. Method D2049.
(2) Pipe installed in embankment. Pipe to be located at elevations above the existing ground level shall be installed in trenches excavated after embankment has been constructed to a minimum elevation of one foot above the proposed top of the pipe.
(3) Pipe bedding material. The pipe shall be bedded from the trench subgrade to the pipe springline in granular material consisting of gravel, crushed gravel or crushed stone meeting the requirements of A. S. T. M. Designation C33, Gradation 67 (three-quarter inch to No. 4).
(4) Foundation in poor soil. Whenever the soil at the bottom of the trench is soft, unstable or saturated with water, a granular fill shall be provided under the pipe to a depth required to stabilize the soil. The maximum size of gravel shall be two inches. A concrete cradle shall be provided when necessary to bridge highly unstable soils.
(c) Backfill.
(1) Material. All material used for backfilling of trenches shall be free of excessive amounts of deleterious materials such as all organic matter, frozen clods and sticky masses of clay and gumbo which are difficult to properly compact. No rock material used for backfill shall be longer than four inches in its greatest dimension or be placed within twelve inches of the installed pipe in any direction, including under, around and on top of the pipe. The pipe shall be embedded in a good quality earth or granular material such as crushed rock or pea gravel.
(2) Height of layers. Backfill shall be placed in six-inch layers from the bottom of the trench to a point at least twelve inches above the top of the pipe and thoroughly tamped by hand or pneumatic tampers. Above this point, backfill shall be deposited in layers of a thickness which will permit compaction to a density specified in paragraph (c)(3) hereof.
(3) Compaction of layers. The layers of material shall be compacted to a density of at least ninety-five percent of the maximum density at optimum moisture content as determined by the AASHO Standard Test (AASHO Designation T99) under all pavements and for future pavements. Pavement shall not be restored over trenches until the backfill material has been tested and determined to be satisfactory according to the tests.
(d) Safety of Public.
(1) Maintenance of traffic. Construction operations shall be scheduled so as to interfere as little as possible with public travel, whether vehicular or pedestrian. Whenever it is necessary to cross or interfere with roads, driveways and walks, whether public or private, suitable and safe bridges, detours or other temporary expedients for the accommodation of public and private travel shall be provided and maintained. Reasonable notice shall be given to owners of private drives before interfering with them.
(2) Barricades and lights.
A. All streets, roads, highways and other public thoroughfares which are closed to traffic, under the authority of a proper permit, shall be protected by means of effective barricades on which shall be placed acceptable warning signs. Such barricades shall be located at the nearest intersecting public highway or street on each side of the blocked section of such public thoroughfare.
B. All open trenches and other excavations shall be provided with suitable barriers, signs and lights to the extent that adequate protection is provided to the public against accident by reason of such open construction. Obstructions, such as material piles and equipment, shall be provided with similar warning signs and lights.
C. All barricades and obstructions shall be illuminated by means of acceptable warning lights at night, and all lights used for this purpose shall be kept burning from sunset to sunrise. Materials stored upon or alongside public streets, roads and highways shall be so placed, and the work at all times shall be so conducted, as to cause the minimum obstruction and inconvenience to the traveling public.
(e) Sheeting and Bracing. All trenches and excavations shall be properly sheeted and braced for the safety of personnel and the protection of the work, to maintain the maximum trench widths permitted and/or to prevent the disturbance or settlement of adjacent foundations or structures.
(f) Construction on State Highways and Streets. The State Department of Highways and Transportation requires a permit for work to be performed on State highways. Provisions for obtaining such permits are set forth in the “Manual on Permits, Virginia Department of Highways, Richmond, Virginia,” the latest revision. No work shall be approved by the County that has not been accepted or approved as satisfactory by the State Department of Highways.
(g) Restoration.
(1) The County shall not approve any construction wherein public or private property has not been restored to a condition at least equal to its condition before commencement of construction.
(2) All streets, roads and highways shall be restored as required by the State Department of Highways and Transportation.
(3) Work performed on private property shall be confined to the easements obtained, and the area shall be seeded or sodded, the landscaping restored, fences restored and all damaged improvements replaced or restored.
(h) Acceptance Tests.
(1) The County shall be permitted access to the construction work at any time for inspection of the work and construction methods.
(2) Sewers shall be checked by the County to determine whether any displacement of pipe has occurred. The test shall be as follows: A light shall be flashed between manholes by means of a flashlight or reflection of sunlight with a mirror. If the illuminated interior of the pipe shows poor alignment, displaced pipe or any other defect, the defect shall be remedied.
(3) All completed sewers shall be tested for leakage by exfiltration (i.e. outward leakage, trench dry) or infiltration (i.e. inward leakage, trench wet). Leakage shall not exceed 200 gallons per inch of diameter of sewer per mile per day up to a twenty-four inch diameter. Leakage may be allowed up to 400 gallons per inch of diameter per mile per day for short sections of sewer lines (between two adjacent manholes) up to and including a twelve-inch diameter. However, the average leakage on the system being tested for acceptance shall not exceed the 200-inch gallon standard.
(4) For sewers larger than twenty-four inches in diameter, leakage shall not exceed 5,000 gallons per mile per day.
(i) Blasting. Blasting, where required, shall be done with care in accordance with all applicable Federal, State and local laws, ordinances and regulations, and shall not be done within a distance of twenty-five feet from a previously laid pipeline or a previously installed structure if, in the opinion of the County, the safety or soundness of existing facilities is in any manner endangered.
(j) Protection of Existing Facilities. All construction operations in the vicinity of existing facilities shall be performed with care to prevent damage to these facilities. If damage occurs, repairs shall be made in a manner approved by the County and any damaged facility shall be repaired with new materials and restored to its original condition. (Adopting Ordinance)