ARCHIVED REPORTS_MONTHLY STATUS REPORT - APRIL 2013

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Stantec Monthly Status Report - April 2013 Chevron Facility #92033 - Stockton Charter Way Commingled Plume No . CP0057 May 14 , 2013 AS System Description The AS system consists of twelve sparge wells (AS - 1 through AS - 12 ) and a PRM AS system . The PRM AS system includes a 15 horsepower ( hp) rotary claw air compressor capable of generating flows up to 60 scfm at 30 pounds per square inch ( psi ) , a 1 /2 hp after-cooler, and a 12- leg manifold . The after cooler decreases the temperature of the air generated from the air compressor. Process air flow is then routed through the 12- leg manifold to the sparge wells . AS System Operation Stantec first operated the AS system on March 7 , 2013 under the supervision of PRM . During the operation , Stantec observed that flow rates into sparge wells AS- 11 and AS - 12 were minimal and suspected that the well screens may had silted - up between the time of their installation and system start- up . Stantec developed the sparge wells on April 5 , 2013 and observed silt in the purged groundwater. Stantec performed an influence test using AS-9 on April 9 , 2013 and influence tests using AS- 5 and AS - 11 individually on April 12 , 2013 . Influence data were consistent with previous pilot study findings . In order to optimize sparging in the subsurface of the Site , the AS system is currently programmed to sparge in pulsed mode and cycle through three groups for the time interval specified in the table below . Each group was determined based on individual pressures and flow rates and may change in the future . The AS system was started for full time operation on April 26 , 2013 . Field notes and field parameter readings including flow rates and pressures are summarized in Table 5 and are included in Attachment B . AS SYSTEM PULSE MODE Group Sparge Wells Time Interval 1 AS- 1 , AS- 10 , AS - 11 , and AS - 12 00 : 00-04 : 00 , 12 : 00- 16 : 00 2 AS1= 3 , AS -6 , AS-8 , and AS -9 04 : 00-08 : 00 , 16 : 00-20 : 00 3 AS -2 , AS4 , AS-5 , and AS -7 08 : 00- 12 : 00 , 20 : 00-24 : 00 AS System Performance The AS system began full time operation on April 26 , 2013 with the sparge pressure to each sparge well below its respective fracture pressure (Table 3 ) . Sparge manifold pressure ranged from 10 . 5 to 20 . 5 psi and sparge manifold flow ranged from 4 to 11 scfm . AS SYSTEM OPERATION AND PERFORMANCE Equipment inventory : AS with 15 hp , 60 scfm at 30 psi air compressor Reporting period : April 2013 ( March 14 through April 26 , 2013 ) Period total flow rate ( scfm ) : Average : 52 Period after-cooler pressure ( psi) : Average : 16 . 5 Period operating hours : 37 ( primarily for startup testing and optimization ) Operating hours since startup : 37 ( primarily for startup testing and optimization ) Minimum Average Maximum Period well manifold pressure ( psi ) : 10 . 5 16 . 1 2005 Period well manifold flow ( scfm ) : 4 . 0 6 . 3 11 . 0 Stockton Charter Way Commingled Plume Monthly Status Report - April . doc 4