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R604 :UPDATE 9-MARCH, 1992 • OPERATION UNDER AUTHORITY TO CONSTRUCT PERMIT # AP 91-106 . The Authority to Construct (Permit No . AP 91-106 ) was issued on February 24, 1992 . Once the carbon scrub units were received (after rejuvenation at Cameron - Yakima) , the vapor recovery system was remanifolded with 2 100 gallon carbon vapor scrub units (R1283 and R1284 ) placed in series behind one Rotron DR505 Blower. Vapor extraction wells P1 , P3 Swarm (P3-A, P3-D, and P3 ) , EX, along with ground water monitoring well MW5 , were attached to the manifold and the system was restarted at 12 : 35 PM on March 31, 1992 . The San Joaquin County Air Pollution Control Officer, Teresa Stuyt, was on hand to inspect the system. Under the Authority to Construct, the vapor extraction system must be monitored twice weekly, with three measurements of the effluent be performed for the first month, then monthly thereafter. Table 3B represents these measurements, see Appendix B for field notes and chromatograms, and Appendix C-Permit to Construct . System Operation On March 31 , 1992, the influent to the carbons was 4 . 02 pounds per day ( lbs/day) at a flow rate of 57 cubic feet per minute (cfm) and an effluent measurement from the last carbon of 0 . 32 lbs/day. This equates to a 92% absorption/destruction of the vapor stream hydrocarbons. The 57 cfm flow rate was not maintained, the blowers heat sensor shut the blower off for a 20 minute cool down. Once the blower came back on the pump bypass was used to decrease the flow rate to 28 . 7 cfm, which decreases the pounds per day to 2 . 02 on the influent and 0 . 05 on the effluent, ie, 97% absoption/destruction of the vapor stream hydrocarbons. On subsequent visits the flow rate ranged between 26 cfm to 32 cfm with the influent dropping from a high of 3 . 12 lbs/day on April 7 , 1992 to 1 . 45 lbs/day on April 14, 1992 . The effluent from the last carbon ranged from below detection limits to a high of 1 . 07 lbs/day. As can be seen when comparing the three per day effluent samples as shown on Table 3B (March 31 through April 14, 1992 ) , a slight bleedthrough (channeling) is occurring from the last carbon, even during the first minutes of operation. This channeling occurs as specific molecules of the contaminant in the vapor stream absorb and "desorb" from the carbon surfaces and are not trapped in the micro or macro pores of the carbon. This absorption-desorption along with the low concentration of the influent stream ( 3 . 12 to 1 . 56 lbs/day) , which allows the hydrocarbons to remain in equilibrium in the vapor stream, does not allow an effective absorption ( greater than 90% ) to occur. page 9