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November 7, 1991 Harding Lawson Associates <br /> 20548,001.03 <br /> Ms. Margaret Lagorio <br /> Sar. 3oaquin County <br /> Page 2 <br /> 4. The sample date on HLA's chain-of-custody and the <br /> laboratory report for groundwater samples collected <br /> September 3, 1991 needs to be formally corrected. <br /> The following paragraphs present this information in the same <br /> numeric order. <br /> 1. On October 24, 1991, we measured depth to groundwater at <br /> 94.74, 96.07, and 96.13 feet, respectively, in monitoring <br /> wells MW-1, -2, and --3. We calculate the gradient as 0.015 <br /> feet per foot towards the north-northwest. This gradient <br /> and direction is consistent with previous calculations. <br /> The gradient and direction of groundwater flow is <br /> apparently controlled by the nearby domestic well. Our <br /> readings of the flow totalizer for this well indicates that <br /> it produces about 1,200 gallons per day. <br /> 2. The chain-of-custody form and the laboratory report <br /> documenting total petroleum hydrocarbons (TPH) <br /> concentrations in soil samples from the aerated stockpile <br /> generated from the gasoline tank removal are attached to <br /> this letter. We have also included the report prepared by <br /> Covenant. Environmental Compliance Consulting, dated <br /> February 8, 1990. The report describes aeration and <br /> sampling of the soils from the tank removal. We understand <br /> that this aerated 5oil .has been spread out on site. <br /> 3. On October 24, 1991, HLA collected samples of the purged <br /> water (PW-1) collected from the monitoring wells. The <br /> sample was submitted for analysis by EPA Test Methods 8015 <br /> and 8020 for concentrations of TPH or gasoline and benzene, <br /> toluene, ethylbenzene, and xylenes (BTEX) . Results of the <br /> testing indicated that levels of TPH as gasoline and BTEX <br /> are below detection limits, and therefore, we propose to <br /> dispose of this water on site. Copies of the laboratory <br /> report and chain-of-custody form are attached. <br /> 4. Groundwater samples were collected September 3, 1991, in <br /> the presence of Ms. Lagorio. The laboratory picked up the <br /> samples from HLA's office on September 4, 1991. <br />