SITE INFORMATION AND CORRESPONDENCE

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UtC 1 6 2006 ENVIRONNI .NT HEALTHI \ PERI,t��1 1 ERVICES FOOTHILL \f ENGINEERING Mr. Michael Infurna 8442 PH0916R729 5184YFAAX:(916oP29,005935843 San Joaquin County Public Health Services 304 E. Weber Third Floor December 17, 2006 Stockton, CA 95202 Subject: Mrs. Helen Higgins /Vogue Cleaners 2315 N California Street Stockton, CA Site code: 231032 Global ID T0607700741 Dear Mr. Infurna: In order to address the concerns expressed by San Joaquin County Environmental Health Department (SJCEHD) in the letter of November 1 C, 2006 Foothill Engineering proposes the following: 1. SJCEHD was concerned that the grab sample of ater from CPT#3 taken at 97' to 102' is in an isolated layer of low permeability. Foothill Engineering would propose that the data be accepted as sufficient evidence as to the existence o a vertical boundary at MW-3 because the extremely hard layer (qt=500tsf) at depth of 93' is aquifer boundary and were the CPT hit refusal at depth of 116' is a second aquifer boundary. The distance between 93' and 116' should be considered the target aquifer below the sand layer at 75'. The sampled depth of 9T to 102' produced plenty of water and did not give any indication of low permeability. If SJCEHD is not agreeable to this line of thought, the only alternative is to collect an additional grab sample at a depth satisfactory to SJCEHD. A CPT can be collected above 116' but if a deeper sample is required a well will be needed since the CPT hit refusal at 116' 2. CPT#4 showed 1,2-DCA contamination at depths of 67'to 72' at 4.9ppb. In order to investigate and monitor the horizontal extent of 1,2 DCA contamination, Foothill Engineering proposes to place MW-91) screened 70'to 80', 42' E st of CPT#4. The location of MW-9D was chosen after considering probable locations of underground utilities, overhead high voltage lines, and the desires of the property owner to place the well cover on the employee parking side of the lot to minimize inconvenience to patients wit limited mobility. It should be noted that CPT#4 did not indicate any sand layers to find, therefore the screen will probably by set at the depths indicated and are simply selected to match up with other contamination depths. A 10' screen is proposed in Order to produce more water for purge and to provide more opportunity to intercept the most cont minated level. The location was selected further down gradient from CPT#4 and not at CPT#4 in order to expand the investigation area and hopefully find the horizontal limits of the 1,2- CA.plume. 3. SJCEHD asked for continuous core samples fro 70' to tip of proposed MW-7D and MW- 8D. Foothill Engineering is agreeable to this. Enclosed is a site map showing the proposed location of the new wells, well construction 1