SR0085556 - Laserfiche WebLink

Home Browse Search

3/5 Well ID Total Depth of Well (feet bgs) Installation Date1 TOC Elevation (feet MSL)2 Depth to Water (feet bgs)1 GW Elevation (feet MSL)1 Well Diameter (inches) Borehole Diameter (inches) MW-1R 19.2 08/08/2016 19.66 9.25 10.41 2 8 MW-1 17.282 NA 19.11 7.53 11.58 NA NA MW-2 13.902 NA 18.46 7.86 10.60 NA NA MW-3 13.492 NA 21.04 9.72 11.32 NA NA MW-4 17.0 08/08/2016 19.34 9.05 10.29 2 8 MW-5 16.0 07/17/2017 17.23 6.66 10.57 2 8 MW-6 10.7 07/17/2017 18.55 6.103 12.453 2 8 MW-7 18.9 12/07/2018 19.41 9.51 9.90 2 8 Notes: 1 = WOOD, 2019 2 = SOS, 2021 3 = SOS, 2019 All data included in the table above was collected from initial well construction logs from the GeoTracker database, when available, unless otherwise noted. No other well construction information was obtained from the resources mentioned above. URS created Table 1 using the information above to calculate the minimum volume of grout to be added to the wells to complete well destruction activities. Information that was assumed and has not been confirmed is highlighted in yellow and will be updated based on the results of the utility clearance field activities. Well Abandonment Procedures Groundwater monitoring wells MW-1 through MW-7 and MW-1R will be abandoned by overdrilling and backfilling with a cement bentonite slurry in accordance with San Joaquin County Well Standards, (SJCDEH, 2005). Prior to abandonment, each well will be cleaned, as needed, to remove all undesirable materials, including obstructions, debris, and other appurtences that could interfere with well destruction. Procedures for cleaning out the borehole include observing the top of the well casing for any hanging lines, shining a flashlight into the open hole, and lowering a measuring tool to the total depth of the well. If obstructions are seen and/or felt while lowering the measuring tool, they will be removed by either removing the hanging lines or fishing the obstruction out with a three-pronged hook or similar tool. Prior to drilling, a URS field representative will measure the following at each well: total depth of the well, depth to water, well diameter, and assumed borehole diameter. Using the field measurements collected, the annular space inside of the well and the filter pack will be calculated by updating Table 1. For wells with a total depth above 20 feet, the filter pack is assumed to be 12 feet (ten feet of screen with one foot of filter pack above and below the screen), for wells with a total depth below 20 feet, the filter pack is assumed to be 17 feet (fifteen feet of screen with one foot of filter pack above and below the screen). The screen slots are assumed to be 0.020-inches and the assumed porosity of the filter pack is 30%. Using hollow stem auger technology, each monitoring well will be overdrilled to a depth of at least 3 feet. The diameter of the auger shall be 1 foot greater than the diameter of the original borehole. The casing will be cut to 6 inches above the bottom of the hole and removed. The seal will consist of a bentonite grout slurry tremied into the well until the measured depth of equilibrated groundwater. Type I/II Portland cement grout (with a maximum of 7 gallons of water per 94 pounds of concrete) with up to 5 percent bentonite will be tremied into the well from the depth of equilibrated groundwater to the top of casing. The amount of bentonite grout slurry and cement grout added to the well will, at minimum, be equal to the