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Geo(oguaf7ecknirs Inc. 1-041Page5 C&B Equipment Additional Site Characterization Work Plan Project No. 336.2 July 15, 1996 ,. 3.4 Modified Groundwater Monitoring Well Sampling Procedure In addition to monitoring water quality parameters (i.e. temperature, conductivity, and pH) we propose to begin gathering data which will offer information regarding the plume's ` stability. Comparing upgradient information with that from the inside of the plume can offer evidence �- that an apparent reduction in gasoline range petroleum hydrocarbon concentration in the water is not completely due to sorption, diffusion, or advection but rather the system is taking care of itself. Some of the specific parameters can be monitored relatively inexpensively in the field and have the potential for providing valuable and comparative information regarding intrinsic bioremediation in the groundwater. There are computer models that will consider these parameters (Bioplume II/III) The following parameters are proposed: V • Dissolved Oxygen (OZ) - useful in determining if there is enough oxygen present to support aerobic degradation. ` Oxidation - Reduction Potential (ORP) - useful in determining the state (oxidizing or reducing conditions) of the aquifer. • Alkalinity - can be a useful indicator of biological activity. Nitrate (NOS) - can be a useful indicator of biological activity. �. Sulfate(SO,) - can be a useful indicator of anaerobic degradation of fuel compounds. • Ferrous Iron (Fez+) - can be a useful indicator of anaerobic degradation of fuel compounds. It is imperative that the D.O. and ORP parameters be evaluated using stabilized groundwater pumping techniques and a flow cell. Although field assay kits (colorimetric) are available, because of the data accuracy requirements we recommend that the electron acceptor data (NO„ SO„ Fez* ) be tested by laboratory analyses (NO, & SO,by EPA 300, & Fez+by SM 4500 Fe). We recommend that groundwater samples to be tested for NO,, SO„ & Fez+be placed in a plastic sample container and be completely filled avoiding headspace, and then placed in a ` chilled cooler as usual. The samples will be tested within 48 hours of sample collection. 3.5 Soil and Groundwater Analyses '— Soil and groundwater samples will be submitted to Sherwood Laboratories of Hilmar (State Certified Laboratory #1400) following chain of custody protocol. �. Based on field screening observations we recommend that at least three soil samples including one from the capillary fringe be submitted for analyses. If necessary additional soil samples collected from beneath the water table may be submitted for analyses. These samples may be useful in determining the sorbed portion of the groundwater plume. N.,