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Mr. William J. Marshall <br /> February 11, 1992 <br /> Page 3 <br /> To address persistence and permanence of potential adverse effects, chloroform has a water solubility <br /> (8,000 mL at 20°C) and is poorly absorbed to soil. Where initially released to surface soils it will <br /> evaporate rapidly due to high vapor pressure (160mm Hg at 20°C). When released to surficial waters, <br /> modeling studies estimate the half life for evaporation of chloroform to be 36 hours in a river, 40 hours <br /> in a pond and 9-10 days in a lake. However, when present in groundwater, the chloroform will volatilize <br /> into the soil vapor, and ultimately discharge into the atmosphere. <br /> Proposed Clean up Goal <br /> To meet the criteria described above, we proposed to stop groundwater remedial activities, and continue <br /> groundwater monitoring of the wells downstream of the storm water basin and the two recovery wells <br /> in the vicinity of the basin on a quarterly basis for a period of one year. If chloroform concentrations <br /> exceed the goal of 100 ug/1, for any two consecutive quarters, the program will be reviewed and modified <br /> with concurrence from the RWQCB. <br /> Schedule <br /> We propose to begin the one year quarterly monitoring program upon receiving approval from the <br /> RWQCB. We look forward to our meeting with you later this month. <br /> Yours very truly, <br /> 9c � ' <br /> - ,GGA"(g <br /> uli�B. Raming U <br /> Environmental Engineer <br /> JBR <br />