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Kennedy/Jenks Consultants Stabilization Criteria for Three or FField Parameters 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 more — Conductance consecutive readings is within±3% Turbidity Difference between three or more Generally, turbidity is the last parameter to consecutive readings is within±10% stabilize.Attempts should be made to achieve or three consecutive readings below stabilization; however, this may not be 10 NTUs 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 more Very sensitive. Attempts should be made to consecutive readings is within achieve stabilization; however, due to ±20mV parameter sensitivity this may not be possible. Dissolved Oxygen Difference between three or more Very sensitive. Attempts should be made to consecutive readings is within±10% achieve stabilization, especially when or±0.2 milligrams per liter(mg/L), collecting samples of VOC analysis; however, whichever is greater due to parameter sensitivity this 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. D.5 Quality Control Guidance Follow the quality control requirements specified in the Quality Assurance Project Plan (QAPP), project-specific field sampling and analysis work plan, and/or project-specific regulatory requirements, as applicable. The following may be used as guidelines. 1. Approximately one duplicate sample should be obtained for each sampling event or for each batch of samples (a batch is typically defined as 20 samples). Collect duplicate samples immediately after the original samples are collected. Purging is not performed between original sample collection and collection of duplicate samples. Original and duplicate samples are collected sequentially, without appreciable delay between collection cycles. Duplicate samples are to be submitted to the laboratory blind (i.e., not identified as a duplicate sample). 2. Typically, at least one type of field blank sample (rinsate or transfer) should be collected per day of water sampling. All field blank samples are to be collected, preserved, labeled, and treated Monitoring Well Installation Work Plan, D-6 Barrel Ten Quarter Circle Land Company, Escalon, California %\SFO\Groups\I S-Group\Adini n\J ob\03\030118.27_BTQ CLC\09-Reports\M W-Install-W Pln\Appendi xW PP_D.doc