SITE INFORMATION AND CORRESPONDENCE

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DENT BY:CLA"T70N ENV I F:OC•MENTA vI-26-90 4: 15PM 012 ;# 3 r. s ENvfRQNME, CONSULTANTS W. Donald C. Lewis Augst 9, 1990 Page 2 collected. Following removal of the septic tank,, and the oil contained in this (�} septic tank, Clayton removed additional soil from beneath and adjacent to this tank•, No soil was left in the e=vation which exceeded the LUFT manual guidelines, which is documented and reported in our October 23, 1990 report. • Although monitoring well MW-3 was destroyed during excavation, the excavation 1\,-� was sealed with quarry gravel and clean clayey soil from a depth of 11 feet below ground surface (bgs) to a depth of 7 feet bgs before stockpiled (aerated) soils were placed in ties excavation. Clayton does not feel that this abandoned monitoring well will provide a conduit for migrMdOn of Contamination based upon the fact that the source (soil) of contaminant has been removed from the L excavation and the groundwater samples collected from this and other wells have detected Any contaminants. * Sail sample MN-2 was analyzed for oil and grease by FPA Method 418.1. Although the results of this analyses were not listed in the table on page 4 of our report, the result was included in the laboratory analysis (Appendix C). M sample contained 1063 than 10 parts per million (ppm) of oil and grease. • wring development of monitoring wells MW-2 and MW-3, tap water was introduced to facilitate development, This is an accepted and recognized practice when initial (development) pumping dewaters the well casing and sufficient water is not recharged into the ween. Sampling of these two wells was conducted two days after development. No tap water was introduced during the purging and sampling process. In addition, with regard to field sampling procedure for wells that recover slowly after purging (resulting in the well being evacuated and recharging slow sampling is commonly aeceptabk if the water in the well recovers to 80% of the initial volume. This was indeed the case for wells MW-2 and MW-3, although field PH and conductivity readings were not taken. + All three origins! wells were surveyed by a licensed land surveyor, Tronoff and Associates of San Francisco, California. Three point problem were utilized to calculate the required groundwater flow direction and gradient, as discussed on page 3 of Clayton's Report No. 29531.00, dated April 26, 1990. • A well to replace the destroyed well, downgradfent of the excavation, has been discussed and is planned. C0nccntratic= of oil and g�rcese ranging from 20 para per minion (ppm) to So ppm in the sail were left in the c cMtiOn. This is acceptable and within the guidelines of the California LUFT manual. Additionally, at these levels we believe the hydrocarbons �saut