SITE INFORMATION AND CORRESPONDENCE_1987-1992

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Antonia K. J. Vorster 5 December 18, 1989 THE REVISED PHASE II WORKPLAN The initial Phase II workplan included the installation of three shallow monitoring wells. The revised workplan included the installation of seven shallow monitoring wells, including the three in the initial plan. See attached map. The four additional monitoring wells are located along the suspected downgradient northern and eastern boundaries of the site. (The consultant within the revised Phase II workplan states that their monthly ground water measurements at this site indicate a generally east to northeasterly direction of flow at a gradient of approximately 0.3 percent.) These wells were apparently located based upon recent analytical results from an existing monitoring well (MW2) that indicate low level PCE contamination (1.8 ppb) . This well is located at the northwest corner of the Lincoln Village site. Therefore, the stated objective of the four new downgradient perimeter wells is to determine if off-site migration of contaminants is occurring within the uppermost water bearing zone. The Phase II workplan also calls for the sampling and analyses (EPA 601 compounds) of water samples from the three Phase I monitoring wells and the seven Phase II monitoring wells. The revised workplan also includes the sampling and analysis of soil samples from six on-site soil borings. See attached map. The soil sampling is to verify the presence and concentration of the potential PCE source areas delineated in the soil gas survey. In addition, soil samples will be taken from monitoring well boreholes. The consultant is prepared to commence the Phase II field investigation on 8 January 1989. The consultant is requesting our approval , of the revised workplan by 21 December 1989. However, based upon my review of this workplan, especially the new ground water results, approval cannot be given. The August 1989 water quality data for the LVMD wells indicate that the Phase II investigation must include an assessment of the vertical extent of contamination, and plans to abate the contamination of the deeper aquifer tapped by the municipal wells. Therefore, Lincoln Village, Inc. should revise the Phase II workplan to address my concerns, and to meet the objectives, as discussed below: 1) The monthly water level data must be submitted, including monthly water level contour maps. 2) All monitoring wells and LVMD wells shall be sampled and analyzed for EPA 601 compounds. Laboratory data sheets for all analyses must be submitted, including the quality control data sheets. 3) The seven shallow zone Phase II monitoring wells appear to be located based upon the results of the soil gas survey and the purported northeast to north ground water flow direction in this water bearing zone. However, we have not received the monthly water level data (Comment 1 above) , which is needed to verify the direction of the ground water movement within the shallow zone.