Laserfiche WebLink
SOP-010 Standard Operating Procedure <br />Well Construction Page 8 of 11 Revision No. 0 March 2020 <br /> <br />Sharpe Army Depot <br />4.5 Post-Operation <br />Following the well completion and demobilization of the rig, the well site should be cleared of all debris and trash and restored to a neat and clean appearance per the project work plans. All investigation derived waste (IDW) generated at the well site should be appropriately contained and managed per the project work plans. <br />4.6 Temporary Monitoring Wells <br />4.6.1 Temporary Well Materials <br />Materials used in the construction of temporary monitoring wells are the same standard materials used in the construction of permanent monitoring wells. Sand used for the filter pack (if any) should be as specified in the work plan. The well screen and casing should be stainless steel (for ruggedness and suitability for steam cleaning and solvent rinsing) or polyvinyl chloride. Appropriate QA/QC must be performed to ensure there will be no introduction of contamination. <br />4.6.2 Temporary Well Borehole Construction <br />Borehole construction for temporary wells should be of sufficient diameter so that well construction can proceed without major difficulties. For open boreholes, the annular space should be approximately 2 inches to allow the uniform deposition of well materials around the screen and riser, and to allow the passage of tremie pipes and well materials without unduly disturbing the borehole wall, using a drill rig. Alternatively, boreholes may be constructed using hand augers or portable powered augers (generally limited to depths of ten feet or less). If a drill rig is used to advance the borehole, the augers must be pulled back the length of the well screen (or removed completely) before sampling. When hand augers are used, the borehole is advanced to the desired depth (or to the point where borehole collapse occurs). In situations where borehole collapse occurs, the auger bucket is typically left in the hole at the point of collapse while the temporary well is assembled. When the well is completely assembled, a final auger bucket of material is quickly removed, and the well is immediately inserted into the borehole, pushing, as needed, to achieve maximum penetration into the saturated materials. <br />4.6.3 Temporary Monitoring Well Types <br />The following five types of monitoring wells have been shown to be acceptable, and are presented in the order of increasing difficulty to install and increasing cost: <br />1. No Filter Pack. After the borehole is completed, the casing and screen are simply inserted. This is <br />the least expensive and fastest well to install. This type of well is extremely sensitive to turbidity <br />fluctuations because there is no filter pack. Care should be taken to not disturb the casing during <br />purging and sampling. <br />2. Inner Filter Pack. A filter pack is placed inside the screen to a level approximately 6 inches above <br />the well screen. This ensures that all water within the casing has passed through the filter pack. For <br />this type well to function properly, the static water level must be at least 6-12 inches above the <br />filter pack. The screen slots may plug in some clayey environments with this construction method <br />and others that use sand only inside the well screen.