ARCHIVED REPORTS_2019 - Laserfiche WebLink

Home Browse Search

Mr. Brendan Kenny July 03, 2019 The proposed extraction well has been located on the western end of the POC, between existing extraction wells EW-3R and EW-2 (Figure 1). Spacing between the extraction wells is based on the hydraulic properties of the aquifer and capture capacities of the existing extraction wells. The proposed additional well EW-5 would be located approximately 575 ft to the east of EW-31R. The extraction well will be advanced using air rotary drilling technique or equivalent. It is anticipated that the total depth of the well will be approximately 100-120 feet below ground surface(bgs), based on the drilling logs from the existing extraction wells(EW-3R and EW-2; Figure 2).The well screen will be positioned in the shallow to intermediate water bearing zone targeting the most permeable materials. Prior to beginning drilling operations, all drill rig equipment will be decontaminated using steam cleaning equipment. Because the drilling operations will not take place near a residential area, noise abatement procedures are not proposed for this project and working hours will be approximately between 6 AM and 6 PM.A temporary borehole protective cover or steel sheeting will be placed on the entry hole during breaks in the drilling process. Well Installation The proposed well design is presented in Table 1 and in Attachment 2. Each borehole will be advanced using a minimum 12-inch-diameter drilling bit. The borehole will be terminated at the base of the intermediate permeable materials, anticipated to be 100-120 feet bgs. However,the final borehole depth will depend on the lithological interpretation at the time of drilling. A geologist under the supervision of a California registered geologist will continuously observe all drilling operations and representative samples of the drill cuttings will be collected and logged at regular intervals during drilling. Lithologic descriptions will include soil type, color, grade, sorting, matrix, accessory minerals, hardness, and an estimation of moisture content. Observations of the drilling progress will also be captured and logged in accordance with§20415 E.2.a of Title 27,which requires soils to be logged and described in accordance with ASTM Designation"D2488." Soil samples will be collected from the screen interval for grain size analysis,to be submitted to confirm anticipated screen and filter sizes. It is anticipated that following borehole advancement, the extraction well will be installed with up to 30 feet of 8-inch diameter 0.020 or 0.030 wire-wrapped stainless well screen and schedule 80 polyvinyl chloride internally threaded riser. The screen interval will be backfilled with #3 CEMEX Lapis Lustre/8/16 or similar sized silica sand as appropriate for the respective screen width, ensuring that a minimum of 5 feet of sand extends above the screen and near the surface. The well will be periodically surged during placement of the filter pack to consolidate the sand. Centralizers will be placed at the top and bottom of the screen and close to the surface. The well screen and well casing materials will be new, decontaminated and will be covered with plastic or similar protective materials when delivered to the site. The well annulus above the sand interval will be backfilled with five feet of'/hydrated bentonite chips. Depth soundings will be utilized to evaluate the thickness and uniformity of the sand pack and bentonite seal, to assure that no bridging occurs. The remaining annulus will be filled to the ground with a Portland neat cement grout, pumped into place using positive displacement tremie techniques. The well screen dimension, material, and slot size may be subject to change based on geologic observations and site conditions. arcadis.corn Page: Forward LF GWTS Upgrade WP 07032019.docx 4/7