COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Air Sparging Pilot Test Related Activities Report and Remedial Action Work Plan Former Countryside Market, Stockton, California April 30, 2015 The field monitoring data (tabulated) collected during the test is provided as Appendix I and observation well head pressure readings are presented in Graph 2A. 4.5.4 Groundwater Level Changes (AS-2 Testing) Groundwater mounding is a potential indication of AS influence since the rise in groundwater levels is attributable to the addition of air into the saturated zone at or near that location. To monitor for the effect of air injection into AS-2, groundwater levels were monitored before, during, and after the injection phase of testing using the data loggers. Graph 2B shows changes in water levels versus time (raw Troll data provided in Appendix J). Apparent displacement was observed in observation wells OBS-1 and AS-1 during each step of testing. The groundwater levels in each observation well showed slight increases in response to initiation of air sparge testing and changes in air sparge flow rate. After an initial increase in groundwater level in response to both initiation and changes in flow rate, the groundwater levels quickly returned to background levels for the duration of each phase of testing. MW-5 showed no apparent change in groundwater level in response to air sparge activities. Groundwater levels in the observation wells returned to background levels within approximately 20 to 30 minutes after air injection was ceased, and the measured displacements during testing were confirmed to not be the result of changes in barometric pressures. 4.5.5 Dissolved Oxygen Monitoring (AS-2 Testing) Approximate background (i.e. pre-injection) DO levels for AS-2 testing were elevated from actual background levels from AS-1 testing on January 27, 2015. DO levels in OBS-1 recovered to approximately 10.5 mg/L prior to commencement of the low-flow (2 scfm) and held at that level through the low-flow step of AS-2 testing. As discussed previously, the actual DO concentration prior to the start of the second test was likely at or near the background level of 2.4 mg/L measured in well OBS-1 prior to the start of the first test. As a result, relative changes in DO levels were used to evaluate the feasibility of sparging during AS-2 testing. During medium-flow testing (7.5 scfm), DO levels in OBS-1 rose to approximately 12.5 mg/L. During high-flow testing (15 scfm) DO levels in OBS-1 rose to approximately 13 mg/L. Following AS-2 testing DO levels in OBS-1 continued to gradually decline to a concentration of 9.72 mg/L when the data logger was extracted from the well on January 29, 2015. DO concentrations in MW-5 did not change significantly during AS-2 testing. DO concentration data for AS-2 testing are presented in Graph 2C. DO readings (raw data) recorded by the data loggers deployed in wells OBS-1, AS-1, and MW-5 are provided in Appendix J. 4.5.6 Oxidation-Reduction Potential Monitoring (AS-2 Testing) Pre-injection ORP levels in OBS-1 (7.5 feet from AS-2) and MW-5 (42 feet from AS-2) were approximately 116 mV and -380 mV, respectively. ORP readings in AS-1 began immediately prior to commencement with a value of 117 mV. During low, medium, and high-flow testing, ORP levels 4-9 The Source Group, Inc.