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CITY OF EVERETT SPECIAL PROVISIONS 7-08.3(1)D Trench Dewatering I (******) This section specifies the definition, responsibilities and execution for dewatering associated with trench excavation for pipes, manholes, catch basins, cleanouts, side sewers and other buried utility work. Implement trench dewatering measures where necessary or directed by the Engineer. Implementation shall include, but Ilnot be limited to, the design, furnishing, installation, operation, maintenance, monitoring, reporting and removal of dewatering systems to achieve proper completion of Work performed under this Contract. Prevent the flow of surface water runoff into the trench excavation. Control I surface water and other erosion control measures associated the Work in accordance with 8-01 of the Standard Specifications and modified in these Special I Provisions. Maintain groundwater level at or below the bottom of the excavation in all Work areas during excavation, foundation preparation, pipe and structure installation I and backfilling. Trench dewatering shall sufficiently control groundwater to prevent softening of the bottom of the excavations or formation of "quick" conditions or "boils" during excavation. Use gravel or non-moisture sensitive trench backfill in areas encountering groundwater. If foundation soils are disturbed or oversaturated I with water, then over excavate and replace the affected areas with suitable fill at no additional cost to the Owner. Upon completion of dewatering operations, restore the normal water table to its natural level in such a manner as to not I disturb the pipe, its foundation and structures. Contractor shall be solely responsible to control the rate and effect of the dewatering in a manner to avoid all objectionable settlement and subsidence. I Direct discharge flow from trench dewatering to a nearby sewer or storm drain system unless otherwise directed by the Engineer. Obtain, at no cost, a Discharge Authorization Permit from the City prior to discharging trench dewatering flows into I the City sewer or storm drain system. Control groundwater by trench dewatering systems designed and operated to minimize turbidity of the discharged flow and to prevent removal of the natural soils or imported fill. I Soils data for use in planning the dewatering system is available from the Geotechnical Report in Appendix A or the Contractor may perform its own soils investigation. Contractor shall be responsible for cost of additional investigative I work Contractor requires for designing the dewatering system. Plan and implement trench dewatering systems using accepted and professional methods of design and engineering consistent with the best modern practice. Trench dewatering systems shall be comprised of gravel-lined sumps, dewatering pumps, piping and conveyance components necessary for complete and reliable function. Before dewatering operations begin, the Contractor shall have available on the 111Work site sufficient pumping equipment, or other machinery, or both, to assure maintaining continuous operation of the trench dewatering system. Supply power service to dewatering pumps including, but not limited to, electrical, hydraulic, gas, or diesel, Maintain the dewatering system to allow for continuous operation I without interruptions. If necessary, provide 24-hour supervision and follow-up by personnel skilled in the operation, maintenance, and replacement of dewatering system components. Damage to Work in place and the excavation, including I damage to the trench bottom, due to "boiling", material removal, or discharge pumping from the excavated area, that may result from negligence, inadequate or improper installation, maintenance and operation of the dewatering system, or I Sewer Regulators R4 and Division 7—STORM, SEWER,WATER May 2017 R39 Modifications I WO No.—UP3633 SP-160