Laserfiche WebLink
page 3 <br /> Drilling and sampling procedures <br /> Double cased wells may be specified where the wells are screen below an upper aquifer. <br /> In this situation, a minimum 10 inch diameter borehole is drilled to the base of the first <br /> aquifer and at least two feet into the aquitard. A conductor casing is then grouted in place <br /> and allowed to set for at least 72 hours. Drilling shall then continue within the conductor <br /> casing, with a drill bit smaller than the inside diameter of the conductor casing to the <br /> desired completion depth. <br /> All wellheads shall be completed with a watertight structure and furnished with a watertight <br /> cap which shall be enclosed in a locked well covering device. <br /> Ground-Water Well Development <br /> Well development of a newly installed well shall begin 24 to 48 hours after the well is <br /> installed to allow cement to harden sufficiently. The well is cleared of disturbed sediment <br /> and water before water samples are collected. All well development tools are thoroughly <br /> cleaned prior to use. Well development tools may be either a stainless steel, teflon, or PVC <br /> bailer, hand pumps or submersible pumps. Surging may be required to remove loose <br /> sediments. For complete development, the wells will be pumped until the discharge is clear <br /> or the turbidity has not noticeably changed within one half hour. A pH and conductivity <br /> meter may be utilized to determine if the groundwater parameters have stabilized. <br /> Ground-water sampling <br /> Prior to sampling, the wells are sounded to determine product levels, water levels, and total <br /> volume of water. Each ground-water monitoring well is purged of at least 3 well volumes <br /> of water using a mechanical or hand-operated pump, or bailer. Conductivity, pH, and <br /> temperature are generally measured during the purging procedure to verify that these <br />