SITE INFORMATION AND CORRESPONDENCE

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4 . Table 1, of these comments, represents only a portion of the data collected on these wells, but it indicates that concentrations exceed the California Department of Health Services (DHS) Maximum Contaminant Level (MCL) of 5 Ag/L for both TCE and PCE, in the Upper Horizon. • State in the text what precautions are to be taken to prevent downward migration of contaminants from the Upper Horizon during well abandonment. 5. Figure 2-3, Boring/Well Construction Log for Well LM-60, contains only page 2 of 2 . • Add the missing page 1 of 2 for Figure 2-3 . Page 3-2 . Section 3 . 1. 3 6 . DLA proposes to use reverse circulation with a 14-inch drill bit for Wells No. 1 and 2 . At 660 feet bgs there is a 12- inch casing in Well No. 1. • State in the text what size drill bit will be used to drill through the 12-inch casing. • State what precautions will be taken to preserve the 4 and 10 feet of plug at the bottoms of Wells No. 1 and 2 , respectively. • State whether the compressed air line will have an in- line filter, as is recommended practice. 7 . According to the San Joaquin County Health District "Wells and Construction and Destruction Suggested Procedures" and the City of Tracy Ordinance No. 348, if it is necessary to use "potable water or drilling fluids" the water or drilling fluids "shall be free from contamination and organic matter. " It is suggested that the use of potable water or drilling fluids be avoided if possible to minimize the inadvertent introduction of contaminants to the wells. If it is necessary to use these media, they should be sampled and analyzed for contaminants of concern prior to use in the drilling operations. • If the decision is made to use drilling fluids, state what type of drilling fluids will be used. Page 3-2 , Section 3 . 1.4 S. The drilling method chosen for LM-60 is a "casing hammer. " According to the National Water Well Association (1989) , one of the disadvantages in casing hammers is the difficulty 3 of 12