SITE INFORMATION AND CORRESPONDENCE

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carry-out further investigation. To summarize what is known in regards to water quality conditions in recently abandoned Well 1: • Well 1 was only screened in the Lower Tulare. • Analytical results of Well 1 groundwater samples detected significant levels of 4, 4 '-DDD, 4 , 4 ' -DDE, and dieldrin. Results can not be verified by resampling because Well 1 has been abandoned. • Monitoring wells surrounding Well 1 but screened in the Upper Tulare (LM 42 , LM 24, LM 25, LM 85) have not detected organochlorine pesticides in groundwater samples. Even if the Upper Tulare were contaminated with organochlorine pesticides, it is unlikely that Well 1 could have drawn pesticides down through 105 feet of Corcoran clay during its operational lifetime. Many factors could have led to the detection of 4 , 4 ' -DDD, 4, 4 ' -DDE, dieldrin in groundwater samples from Well 1. These factors include: 1) materials introduced into the well during original well closure activities, 2) leaching of chemicals from the clay, sand, and wood debris used to backfill the well, 3) field contamination during this investigation, 4) point source pesticide contamination drawn down from upper horizons through the Corcoran clay (This factor is unlikely for reasons stated above) , and 5) a regional low concentration pesticide plume as suggested by a letter from the RWQCB dated October 5, 1992 . Analytical results from Well 4 , believed to be perforated in the Upper Tulare and in the Lower Tulare, and Well 7, believed to be perforated at least in the Lower Tulare, have not detected organochlorine pesticides during this sampling event or during a sampling event conducted in April 1992 . SPECIFIC COMMENTS 1. Section 3 , Figure 3-1 Figure 3-1 is the Well Abandonment Log for Well 1. Nowhere on the log is it indicated that this is a well abandonment log. To dispel any confusion in the future, it is recommended that the log be identified as a well abandonment log. 2