FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

Temporary PieS.Aer Installation and Destruction Work Plan City of Stockton,Regional Wastewater Control Facility Page 2 Site-specific Health and Safety Plan will be discussed with, and presented to, all field personnel for their signatures as acknowledgement of the Health and Safety Plan. i Proposed Temporary Piezometer Locations The purpose of the four proposed temporary piezometers is to conduct a 14-day groundwater gradient study of the groundwater under the RWCF's Channel. This Channel is an approximately 1,000 foot long structure located on the southwest side of the SJR and north of the railroad tracks. Quarterly groundwater monitoring reports of the site indicate that the groundwater gradient in this area has consistently been to the southwest, away from the SJR. Two temporary piezometers will be placed between the Channel and the SJR, and two temporary piezometers will be placed southwest of the Channel for the purpose of collecting groundwater gradient information. The relative locations and elevations of the temporary piezometers will be surveyed to a local benchmark. The approximate locations of the proposed four temporary piezometers are shown in Figure 2—Proposed Temporary Piezometer Locations, attached. Temporary Piezometer Installation,Surveying, and Destruction Activities The four proposed temporary piezometers will be installed to depths of approximately 15 to 25 feet below ground surface (bgs) by a California Licensed C-57 contractor using the hollow stem auger drilling method. All drilling and well completion activities will be completed under the supervision of a Condor geologist in accordance with the provisions of the SJCEHD permits. Four boreholes will be drilled at the locations indicated on Figure 2 (attached), and a temporary piezometer will be constructed in each borehole. Each borehole will be a minimum diameter of eight inches. The four proposed temporary piezometers will be constructed with five JjLfeeLof two-inch outside diameter (O.D.), Schedule 40, flush-threaded, machine-slotted PVC s reen slot size 0.010). A PVC slip cap will be placed at the bottom of the temporary piezometer screens. Blank PVC casing wr be installed above the screens to the ground surface. No glue or solvents will be used in the construction of the temporary piezometers. A filter pack of #3 Monterey sand will be placed in the annular space to approximately two feet above the screens while the augers are in place. The depth of the sand in the annulus of the temporary piezometers will be monitored with a weighted tape measure while the sand is being placed and the augers are being gradually retracted to avoid bridging. If conditions allow, the sand pack will be surged prior to placement of the bentonite seal. A bentonite slurry seal will be pumped into the annulus of the temporary piezometers and will extend from above the sand to within three (3) feet of the ground surface to form a protective seal. Native fill will be used to complete the temporary piezometers to the ground surface2. The bentonite slurry will be installed as the augers are retracted. Monuments will be placed over the temporary piezometers casings for protection. A construction diagram for the proposed temporary piezometers is shown in Figure 3 — Proposed Temporary Piezometer Construction Diagram, attached. Soil cuttings from the four boreholes will be used to complete the upper portion of the temporary piezometers to ground surface; excess soil will be spread at the site. Condor will prepare completion logs for each temporary piezometer. Completion details recorded on logs will include the type of screen and casing, depth intervals of the screen, blank casing, sand pack, bentonite seals and surface seals, and the quantities of materials added to the annular spaces. 'Personal communication with Mike Infuma with the San Joaquin County Environmental Health Department, July 25,2007 4M A�_ 68 CONDOR