Laserfiche WebLink
) <br /> I. H. KLEINFELQER & ASSOCIATES <br /> i ' <br /> - i <br /> l�l <br /> 4 DISCUSSION OF FINDINGS I <br /> i <br /> As of April 16, 1957 the vapor extraction system has been operating on a <br /> 5-day, 16--hour--a- day basis for about 30 operating days. The. typical <br /> i <br /> vacuum recorded at the vapor extraction well was 4.5 inches mercury at <br /> about 500 actual cubic feet per minute (ACFM). The principal analytical <br /> instrument used to monitor the discharge total hydrocarbon concentration <br /> was a photoionization detector (PID). Periodically, duplicate samples <br /> were obtained in carbon tubes and analyzed in accordance with the standard <br /> EPA test methods by Cal/Enseco. <br /> i� <br /> Table I describes the operational data obtained from field PID values and ` <br /> corresponding TPH removal rates calculated in pounds per hour. Plate 7 <br /> illustrates the PID values over the 456-hour operating period and the <br /> total hydrocarbon removal rate expressed in pounds TPH removed per hour <br /> over the operating period. An interesting observation was noted on the j <br /> two figures. At the 115-, 260-, and 408-hour intervals a noticeable <br /> increase in TPH concentration occurred during the vapor extraction system <br /> operation immediately after these three weekend shutdowns. This higher tl <br /> TPH concentration (and removal rate) on the Monday and Tuesday following <br /> the weekend may be due to soil re-equilibration after 80 hours of weekday <br /> operation (5 days at 16 hours each day). Further tests are being F <br /> performed to confirm this occurrence. It should be noted, however, that <br /> the overall trend appears to be a decreasing level of TPH concentration !. <br /> (and corresponding TPH removal rate per hour) as the total hours of vapor f€ <br /> extraction system operation increase. <br /> } <br /> i <br /> i <br /> 10 <br /> 41-87-137 ' - <br />