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Work Plan for Additional Subsurface Assessment and Remedial Action.—Former Unocal Station#2$59 December 11,2001 Soil from each'sampled' interval will be:screened in,the field'foi-the6:'presence of Valaii16 ,Organic ` compounds using a photoionization:detector.;(PID).' .These data f will be, collected for reconnaissance - purposes only, and will riot_be used as verification of the presence or absence-of petroleum hydrocarbon's.- t Screening data will be recorded on the:boring,logs: The groundwater monitoring wells will be constructed with. 2-inch diameter Schedule SAO polyvinyl chloride (PVC) well casing and 0.02-inch"machine slotted 'w ell screen.. The wells will be'.screened from approximately 50 to 60 feet ,and 85 to 90 feet bgs. .The actual, screen interval -will depend on the groundwater depth and lithologic,conditions encountered during drilling ,Proposed"well construction ` details are presented in Figures 3 and'4: Drill cuttings will be stored at the site pending.receipt"of chemical analytical data for disposal. .The drill f. cuttings-will be stockpiled on and covered with plastid sheeting. Four'.discrete soil-samples will -be collected from the-drill cuttingsfor.disposal characterization as'described in-:Appendix A."These samples". will be submitted to the laboratory for compositing'and analysis'as'de'scribed.in'.Task 6" Stockpiled-soil ,. and steam cleaning rinsate will be transported for disposal at an'appropriately licensed facility. Task 3., Well Deyelopnient and Sampling The newly installed groundwater monitoring wells will .be'developed after being allowed to stand' a 1 minimum of 72 hours following completion. During development, .the'clarity of the discharged well water and selected groundwater parameters (pH,.temperature, and conductivity) will be monitored. When ' ' the discharge water runs clear and the groundwater parameters.havestabilized, a groundwater sample will, j be collected. Groundwater rernoved'frotri the wells during development-and sampling will:be.transpoi•ted" - to an appropriately licensed facility for disposal: The groundwater samples wilLbe analyzed as described ' = in Task 6. The newly installed.well will be included in the quarterly monitoring program beginning with i the quarterfollowing installation: i Task 4. Sparge Point Installation ; Ozone microsparge well 'will'will be completed in 'conjunction`with monitoring well .installation: Eight K-V Associates, Inc..-(KVA) microsparge wells-will be installed at the locations shown on Figure 2. " Drilling and sparge well installation.will.-be performed by'a California licensed driller. The`eigtit wells will be installed in three "sets, with the iwo;southern:';most,_sets,shown,on Figure'2`consisting bf three wells installed in well borings drilled.to depths of'approzimately 30,'60,-and,90 feet bgs; and the northern most.set, ' consisting of two wells.installed in well borings drilled to depths of approximately'30 and 60 feet bgs. Each microsparging well will consist'of a 2.5 foot long, 2-inch'diameier"micro=bubbling" well point screen segment set at the base of the well'boring,'witti,"3/4-inch diameter Schedule 40 PVC well casing extending from the top of the'well"point to ground surface..The annular'-space around each well point will be filled with Lonestar#60 sand to approximately two feet above the top of the well point, followed by a 3 to 5 foot ' seal of bentonite,then neat cement to ground surface. The top each microsparging well will'be protected with a flush mounted water-resistant-well'box ser in concreie. "Because these well borings"are„being drilled for a remediation system, no soil or grab"groundwater samples will be collected from these well borings for' ' chemical analysis. The microsparge well's construction .includes a check'”valve to 'prevent groundwater, 240072.06' 4 _ "