COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Additional Subsurface Investigation and Well Installation Work Plan San Joaquin County Public Works June 19, 2017 Page 5 with hollow stem augers. Soil samples will be collected at 5-foot intervals using a 2-inch diameter California-modified split spoon sampler for soil characterization using the Unified Soil Classification System (USCS). Condor does not anticipate collecting any soil samples from the shallow monitoring wells for laboratory analyses. The shallow monitoring wells will be constructed with 15 feet of 2-inch outside diameter, Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.010). A flush-threaded PVC bottom cap will be placed at the bottom of the screen section in each well. Blank PVC casing will be installed above the screen to the ground surface. A filter pack of #2/12 or #2/16 sand will be placed in the annular space to approximately two feet above the screen while the augers are in place. The depth of the sand in the annulus of the well will be monitored with a weighted tape measure while the sand is being placed and the augers are being gradually retracted to avoid bridging. To form a protective seal, approximately two feet of bentonite chips will be installed above the sand in the well. The bentonite chips will be installed as the augers are retracted. The bentonite chips will be hydrated with potable water. A surface seal of neat cement will be poured into the annulus of the well using a tremie pipe and will extend from the bentonite to the ground surface. The monitoring wells will be completed at the ground surface with traffic-rated, locking well boxes. Details of well construction will be noted on the geologic logs, including the depth intervals of the screen, sand pack, and seal. A typical monitoring well construction diagram is shown on Figure 7 (Appendix A). All down-hole drilling equipment will be decontaminated prior to use in each well boring. The drill cuttings and any cleaning effluent will be placed in Department of Transportation (DOT)-approved 55- gallon drums, sealed, labeled, and left on site pending laboratory analyses. 4.5 OZONE INJECTION WELL INSTALLATION PROCEDURES One additional ozone injection well will be installed at the Site to provide adequate injection of ozone throughout the heart of the dissolved contaminant plume. The ozone injection well (0W-7) will be installed between the southern dispenser and UST #2, where ozone injection well OW-7 was previously proposed but not installed. The proposed location is shown on Figure 6 (Appendix A). The ozone injection well will be installed using hollow-stem auger drilling methods. Drilling activities will be performed under the supervision of a Condor geologist. The soil cuttings from the borings will be logged in accordance with the Unified Soil Classification System (USCS). Descriptions of soil types encountered will be recorded on geologic logs. All down-hole drilling equipment will be decontaminated prior to use in each well boring. The drill cuttings and any cleaning effluent will be placed in Department of Transportation (DOT)-approved 55-gallon drums, sealed, labeled, and left on site pending laboratory analyses. The ozone injection well bore hole will be drilled to a total depth between approximately 45 to 48 feet bgs. The actual installation depth may be modified after completion of the deep boring investigation confirms the lithology beneath the Site. The anticipated depth of the ozone sparge point is intended to correlate with a poorly graded sand layer identified during the installation of MW-1 and shown cross section B-B' (Figure 4, Appendix A). The ozone injection well will be constructed with an 18-inch long, 1.5-inch outside diameter (0.D.) porous Kynar sparge point. Blank 1-inch Schedule 80 PVC casing will be installed above the sparge point to the ground surface. A filter pack of #3 or #2/12 Monterey sand will be placed in the annular space to approximately 1.5 feet above the sparge point while the augers are in place. The depth of the sand in the annulus of the well will be monitored with a weighted tape measure while the sand is being placed and the augers are being gradually retracted to avoid bridging. Approximately two feet of time-release bentonite pellets will be placed above the sand to form a CONDOR