SITE INFORMATION AND CORRESPONDENCE

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Mr. Kevin Graves April 28, 2006 Page 3 The request letter specified that the "work proposed should complete the investigation of the lateral and vertical extent of the soil and groundwater contamination so that the mass of contamination remaining can be calculated and evaluated (emphasis added). Clearly, any hydrocarbon sample analytical results from the early 1990s from soil still in place in 2006, are no longer representative, nor valid. Consequently, it is impossible for anyone "to complete the investigation of the lateral and vertical extent of the soil . . . contamination." (Emphasis added.) Section 1.0 - Lateral and Vertical Extent of the Soil Contamination of the work plan proposed that soil samples be collected from a depth of four feet to the depth of first encountered groundwater at twelve locations from around the former tank location remedial excavation and from between the former tank location and the enclosure to Thornton Municipal Well No. 2. Information provided by EHD indicates that first encountered ground water was previously reported at depths of 12.3 to 16 feet when monitoring wells MW-1 to MW-4 were installed in November 1990 and 16 to 17.5 feet when MW-5 and MW-6 were installed in October 1991. Static water levels were reported as being from 0.15 to 3 feet higher at these times, indicating that the first encountered aquifer is semi-confined to confined. "The Work Plan is not approved" letter states, as the first sentence in paragraph two, that "The lateral and vertical extent of soil contamination cannot be defined by collecting soil samples from a depth of four feet to the depth of first encountered groundwater." The Tr-Regional Board Staff Recommendations for Preliminary Site Evaluation and Investigation of Underground Tank Sites established the remedial goal definition of soil as that occurring above first encountered groundwater in Section III.1.a, wherein it is stated that "Soil samples are to be taken ... at a minimum of every five feet in the unsaturated zone ... ." The second paragraph of "The Work Plan is not approved" letter goes on to summarize old data from samples collected at a depth below first encountered groundwater as reported from the monitoring well boreholes. Saturated earth materials from below the first encountered groundwater, or the historically lowest water level in the event that it is below the first encountered groundwater at the time of the investigation, are not representative of soil conditions, but rather represent groundwater conditions. The first sentence in paragraph three states - "H2OGEOL did not provide a technical justification for the geoprobe investigation." Soil sampling to accomplish the EHD's requested extent determinations by nearly continuous direct push technology, such as that under the brand name of GeoprobeTm ,does not seem to warrant additional technical justification. The justification for the locations of sample points shown on Figure 3 of the work plan is intuitively obvious from the site configurations, particularly previous excavations and the location of the Thornton Municipal Well. No. 2. No technical justification should be required beyond EHD's request. A GROUNDWATER CONSULTANCY H2OGEOL