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circumference seam in any 10 feet. Short joints between screen sections may be required. r 1. All joints of any stainless steel casing sections shall be closed by continuous welding. A welding sequence shall be followed which will avoid excessive distortion. All joints shall be welded watertight with a minimum 90% penetration. Welding shall be in accordance with applicable provisions of the latest edition of the American Welding Society publication, "Transmission Pipelines". 2. If plain end, beveled or butt-welded casing is used, no less than four straps, 114-inch thick and 1-112 inches wide shall be provided and used at each joint. If welding collars are used, no welding straps shall be required. Welding collars shall be the same material as the casing. 3. Dielectric couplings shall be used at all joints between dissimilar metals. H. Casing Guides: Centering guides shall be welded or attached in a an approved manner to the outside of conductor, screen and well casing sections to center the elements in the bore hole. Centering guides shall, at a minimum, consist of 2-inch-wide by 318-inch-thick steel, having a bearing area of at least 1-foot length at the casing/bore interface. Centering guides shall of the same material as the casing and/or screen, welded at both ends to the casing and screen and bent to form a guide at the required depth. Centering guides shall be sized to create a uniform annular space around the casing in the bore hole. ,a 1. On conductor casing, a minimum of ei ht centering guides shall be provided at each of the following locations: 4 feet from the bottom, 4 feet from the ground surface and in between at intervals of not over-40 feet. 2. On the screen, centering guides shall be provided at the top and bottom and in between at intervals of not over 40 feet. shall be provided 3. On the well casing, a minimum of fqr, centering guides p x at the following locations: 4 feet from the bottom of the well screen, 4 feet up from the bottom of the conductor casing, 4 feet below ground I;Vel, and in between at intervals of not over 40 feet. v 2.02 WATER h A. Water used in well construction and disinfection shall be potable water from a source approved by the Engineer. The City will issue a "no fee" water permit for the Contractor's use of a nearby fire hydrant. The Contractor or on the supply a City-approved backflow prevention device at the fire hydrant water truck. r—.- �t' 2.03 DRILLING FLUID A. A circulating fluid shall be maintained at all times during the drilling -Vf operations. No mud additive shall be used without demonstrated need. If an b additive is required to do a satisfactory job, it shall be an inorganic, non- Division III- 17 f