SITE INFORMATION AND CORRESPONDENCE

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Collect and Report Accurate and*Reliable Data site decision making, tracking the progress of remediation, determining target capture zones, and Accurate data is crucial for making well-informed interpreting success or failure of actual capture (see decisions about site operations and strategy. It can also previous Section "Evaluate Plume Capture"). represent a significant portion of O&M cost. As a result, a number of considerations should be applied to Processing data and generating and reviewing these collection and management of ground water elevations plots for each monitoring event ensures data quality (Exhibit 6) and water quality data(Exhibit 7, on the because errors, inconsistencies, or data gaps can be following page). addressed before subsequent events. Electronic data management, spreadsheets, and plotting software Update Plume Maps,Potentiometric Surfaces, and allow these plots to be updated with minimal level of Trend Analyses effort and low cost. Thus, if practical, the plots should be generated after each monitoring event. Consistent Plume maps, potentiometric surfaces, interpreted flow contouring methods or software should be used for directions and magnitudes, and data trend plots are developing the plots for a given site, and the method fundamental to data interpretation and are useful for or software used should be noted. Exhibit 6 Considerations for Collecting and Recording Ground Water Elevation Measurements Measure depths to ground water in each well or piezometer two or three times to avoid false readings,and measure depths to water at all locations on the same day, if possible. Include water levels from surface water bodies that may influence ground water elevations. Have on hand historical data when measuring depths to ground water to confirm that current measurements are consistent with the historical ones. If there is a significant discrepancy,determine if a similar discrepancy exists for each sampling location. If the discrepancy appears to be an anomaly(exists at only one or two wells),note the discrepancy in the field log book and in the O&M reports. Note piezometer and monitoring well integrity and condition. Routine redevelopment or cleaning may be necessary. Always measure depths to ground water from a clearly visible surveyor's elevation mark on the well. The location of each piezometer and well should be accurately surveyed to within 0.1 feet horizontally,and the reference mark should be accurately surveyed to within 0.01 feet vertically. Re-survey wells and piezometers if changes in casing elevation are suspected due to settling,frost heaves,or other damage to wells. Maintain surveyor's mark to prevent fading. In reports,clearly distinguish the difference between the depth to ground water and the ground water elevation(i.e., "water level"). Specify the reference points and units for each measurement(i.e.,"feet below ground surface"for depth to ground water and"feet above mean sea level"for ground water elevation). Report new ground water elevations alongside previously recorded ground water elevations in tables so that trends can be easily noticed by the reader. Interpret each round of ground water elevation measurements with respect to the site conceptual model and site goals. Reconsider the frequency of measurement events if the amount of data and interpretation are either insufficient or excessive with respect to the system goals.The monitoring frequency for water levels and water quality need not be the same. Obtain ground water elevations from clusters of wells or piezometers with various elevations if vertical flow is an important aspect of the site conceptual model. Note:Inaccurate or insufficient data can lead to poor management decisions, and excessive data are not cost-effective. 9