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Well Sampling Frequency -2- 12 July 1991 <br /> DDRW, Sharpe Site <br /> 5. To develop a program which has documentable quality <br /> assurance/quality control and has defined procedures for sample <br /> collection and well maintenance. <br /> 6. To collect consistent ground water level measurements so that <br /> hydraulic analyses may be performed including the determination of <br /> flow directions, gradients, head differences and whether there are <br /> seasonal variations in the hydraulic system. <br /> 7. To assure that ground water sampling is performed in a cost <br /> effective manner so as to meet the above stated objectives. <br /> Page 1-1 . A map of the site was not provided in the Report. The Report should <br /> have included a site map which depicted the locations of all of the <br /> wells so that the proposed changes in the monitoring program could be <br /> readily referenced with respect to the plume configuration, other supply <br /> wells and to on-site disposal areas. <br /> Page 1-2. The Report does not consider use of the automated ground water level <br /> measuring system which in-place at the site. We recommend that Sharpe <br /> consider using this system to generate and interpret data which would be <br /> beneficial to the on-going monitoring program and the Remedial <br /> Investigation/Feasibility Study (RI/FS) . <br /> Page 2-1. Our major concern with the quarterly and annual monitoring program as <br /> proposed is that the monitoring wells in a cluster are not sampled all <br /> together so that some of the wells in the cluster are sampled quarterly <br /> and the others are sampled annually. We believe that this sampling is <br /> not optimizing the data and such a monitoring program is confusing. We <br /> recommend that the full clusters be sampled either quarterly, semi <br /> annually or annually so that the vertical as well as the horizontal <br /> extent of the plume can be defined. <br /> The monitoring plan did not indicate when the annual sampling would <br /> occur. Semiannual sampling with alternating quarterly sampling is <br /> preferred because of the apparent seasonal fluctuations in the hydraulic <br /> system at the site. Therefore, semiannual sampling would be best if <br /> taken at the height of the wet winter season when the hydraulic system <br /> would be anticipated to be the most quiescent and at the height of the <br /> dry summer season when outflows from the system would be at a maximum <br /> due to the agricultural pumpage in the area. Analysis for the worst <br /> case of the lateral and vertical extent of the plume should be performed <br /> using data collected during the dry, summer season. We recommend that <br /> semiannual sampling be considered in the future. <br /> In general , the proposed quarterly program includes too many wells. We <br /> believe that the number of full well clusters can be reduced to include <br /> well clusters with the highest concentrations of VOCs along the axes of <br /> the plume for the quarterly sampling round. The proposed annual <br /> monitoring should be increased to semi-annual . We recommend that a more <br /> comprehensive monitoring program be performed at the height of the wet <br /> and dry seasons and that a reduced monitoring program be performed for <br /> the two quarters between the semi-annual sampling rounds. <br />