R 325.1762 Wells 40 feet or less below grade.

Rule 262. A dewatering well used in conjunction with underground construction or building excavation when the dewatering well is not more than 40 feet below the working grade shall be plugged as provided in this rule except dewatering wells covered by R 325.1763. At the time the filter material is added, the well shall be backfilled from a depth of not less than 7 feet below the working grade to the working grade with an inorganic parent soil material encountered within the upper 7 feet. A finer textured inorganic soil shall be used when substituted for the parent material. The plugging shall be completed after the casing and screen are removed from the dewatering well by adding and compacting additional inorganic parent material naturally occurring in the upper 7 feet or with finer textured soils in the excavation remaining at the site due to slumping of the filter material. These soils shall be added in a manner to prevent future slumping and assure that the drill hole shall remain filled to the working grade. Where 1 or more dewatering wells are deeper than 40 feet in depth, plugging procedure prescribed in R 325.1763 shall be used on all wells penetrating the deeper aquifer. Exception to this plugging procedure may be requested and a written decision reached through a conference with the department.