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Kennedy/Jenks Consultants 4.4 Stabilization Criteria for Adequacy of Monitoring Well Purging Environmental Investigations Standard Operating Procedures and Quality Assurance Manual(EPA 2001) states that "with respect to groundwater chemistry, an adequate purge is achieved when pH, specific conductance, and temperature of groundwater have stabilized and the turbidity has either stabilized or is below 10 Nephelometric Turbidity Units (NTUs). Wells should be considered stable when the criteria listed in the following table have been met for pH, specific conductance, temperature, and turbidity. Attempts should also be made to stabilize ORP and dissolved oxygen. Field Stabilization Criteria for Three Parameters or More Consecutive Readings Notes pH Difference between three or more consecutive readings is within ±0.2 units Temperature Difference between three or more consecutive readings is constant Specific Difference between three or — Conductance more consecutive readings is within±3% Turbidity Difference between three or Generally, turbidity is the last parameter to more consecutive readings is stabilize. Attempts should be made to within ±10% or three consecutive achieve stabilization; however, this may readings below 10 NTUs not be possible. It should be noted that natural turbidity in groundwater may exceed 10 NTUs. If turbidity is greater than 50 NTU, redevelopment of the well may be warranted. ORP Difference between three or Very sensitive. Attempts should be made more consecutive readings is to achieve stabilization; however, due to within ±20mV parameter sensitivity this may not be possible. Dissolved Difference between three or Very sensitive. Attempts should be made Oxygen more consecutive readings is to achieve stabilization, especially when within ±10%or±0.2 milligrams collecting samples of VOC analysis; per liter(mg/L), whichever is however, due to parameter sensitivity this greater may not be possible. Attempts should be made to achieve the stabilization criteria. Because of geochemical heterogeneities in the subsurface environment, stabilization of field parameters during purging may not always be achievable. If field parameter measurements do not indicate stabilization, continued conventional purging may be required until a minimum of three wetted-casing volumes have been removed. During low-flow purging of a well containing a large volume of casing water, it may be practical to discontinue low-flow purging and proceed with sampling if field parameters have not stabilized within a reasonable period. This judgment must be made on a site-specific/project- specific basis. Hydrogeologic Investigation and Groundwater Sampling and Analysis Work Plan SOG 4 Sutter Home Lodi Winery, Lodi, California Page 5 of 7 g4s-vwpledminVOM 086500506_su eftm%09,vWsY*ksksll"ydo l pfwlappen&alappb mpldg ..p wdw