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(8) Vapor distribution and migration (2) The number and location of initial sampling points in potential source (9) Unique site features. areas and areas with known contamination.The rationale for the number, location and depth of sampling points selected should be provided. The CSM is a dynamic and iterative tool,and is meant to be updated as new (3) A clear statement as to whether permanent or temporary vapor wells are information becomes available. Therefore,it should be revised after each stage to be installed,and the rationale for making that decision. of the investigation. (4) A clear statement as to whether a mobile and/or stationary laboratory will To identify sources,potential release mechanism(s)and pathway(s)for vapor be used when samples are collected,and the rationale for making that migration,collect some or all of the following information: decision. Note that non-specific portable organic vapor analyzers and/or gas chromatograph(GC)-based handheld detectors should not be used • soil types ` for quantification during a soil gas investigation. As of the date of this . • subsurface geology document,a laboratory certification program is in progress Once • hydrogeology(local and regional)including groundwater Flow,direction certification program is available by the California Department of Health • subsurface heterogeneity Services,laboratories should apply for a certification program as soon as • groundwater quality data possible. • regional groundwater Flow direction • well records (5) A schematic diagram of the well design and a cross-section of the site • boring logs showing the major lithologic units and zones for vapor monitoring should • surficial features of the area,such as ground cover and surface water be included in the workplan(see Figures 1 and 2). bodies. (6) A clear statement as to how to prevent infiltration of surface runoff with A cross-sectional diagram or equivalent depicting a three-dimensional concept of contaminates into the vadose zone,groundwater,and the monitoring points. the site may be helpful in demonstrating and understanding site dynamics. Examples of features to include for the three-dimensional conceptual model (7) q clear statement to how unauthorized access to the permanent include the items listed above as well as: • point of source entry into the vadose zone monitoring pointswill be prevented,for example,by a locking subsurface • primary and secondary source location and depths utility vault) • vertical profiling of lithologic changes down to the first occurrence of (8) Considerations for sampling frequency pursuant to the DQOs established groundwater for each site. • location of above ground buildings and receptors relative to the source. (9) Procedures for properly installing soil gas sampling points. The Elements of the Workplan workplan should provide sufficient details concerning installation of •Provide details of the study design in the Workplan,which include: sampling points based on known site conditions. (10) Procedures to properly decommission monitoring vapor wells that are no (1) A scaled site map which identifies proposed sampling points,with longer needed. The decommissioning activity should achieve an effective locations and coordinates of identifiable geographic landmarks,such as and long-term seal of subsurface geologic materials and prevent cross- street center-line,benchmarks,street intersection,and wells. The site contamination in the subsurtace, map should also include the known or inferred extent of contamination as well as,pertinent features that represent potential or known areas of (11) A health and safety plan for the project. concern. Examples of pertinent features include existing or former sumps,trenches,drains,sewer lines,clarifiers,septic systems,piping, and locations of ASTs,USTs,and chemical or waste management 2.1 Field Activities units. The project proponent should notify the regulating agency 10 working days prior 3/3/2010 -13- 3/3/2010 -14-