OAR 690-240-0430: Casing

(1) The constructor shall consider the following factors when selecting monitoring well casing: (a) The casing installed shall not be readily reactive with the subsurface environment according to best available knowledge; (b) The casing installed shall not adversely affect or interfere with the chemical, physical, radiological, or biological constituents of interest according to best available knowledge; (c) The collapse strength of all casing used in monitoring well construction must be great enough to withstand the pressure exerted by the annular seal during seal placement, including heat of hydration. (2) All monitoring well casing shall conform to at least 304 or 316 stainless steel, polytetrafluoroethylene PTFE, Schedule 40 PVC casing, or other casing materials rated and approved by ASTM for monitoring well construction. (3) All casing installed shall be in new or like new condition, being free of pits or breaks, and shall be cleaned of foreign materials and contaminants prior to installation, unless removed from the manufacturer's packaging on site. (4) An approved special standard is required to use steel casing that requires welding in the construction of a monitoring well. This does not apply to temporary casing that is used during the construction of the monitoring well but is removed prior to completion.