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5.4 Drilling, Organic Vapor Monitoring, Soil Sampling and Well Installations IES proposes to utilize a CME-75, or equivalent, equipped with 8-inch diameter hollow-stem augers to advance the well borings, collect soil samples and allow for the proper placement of well construction materials. Due to high-power electrical transmission lines in the vicinity of proposed wells MW-15B and MW-16C and the other wells being proposed on an earthen easement, IES will contract a limited access drill rig for this phase of work. Drilling activities will be conducted in accordance with IES's Standard Operating Procedure — Soil Sampling/Drilling Methods and Procedures (Includes Well Installation, Development and Surveying).All IES SOPS were included in the Work Plan. During drilling, to obtain preliminary data regarding potential petroleum hydrocarbon-impacted soil and to monitor worker health and safety, a representative sample will be collected near each soil sampling depth and field screened for volatile organic vapors. Organic vapor readings will be collected using a Mini-Rae 3000 Photo-ionization detector (PID), calibrated to isobutylene, and will be recorded in the boring logs. Organic vapor monitoring will be conducted in general accordance with IES's Standard Operating Procedure-Field Soil Vapor Monitoring. Undisturbed soil samples will be collected from the well boring at approximately 5-foot intervals, changes in lithology, within the perceived soil/water interface, and at the bottom of the soil boring utilizing a California split-spoon sampler equipped with three, six-inch long,brass (or stainless steel), 1.5- inch diameter sleeves. As each soil sample is collected, the bottom tube will be sealed with Teflon TM tape, capped and properly labeled and placed in an ice-filled cooler for possible future analytical testing and the adjacent tube will be field screened for organic vapors and inspected for logging purposes. Only soil samples that field screening demonstrates volatile organic compound contamination as observed through RID readings will be submitted for laboratory analysis. Proposed wells MW-1513, MW-17B and MW-19B will target the B zone with a proposed well-screen interval placed between approximately 40- and 60-feet bgs. Proposed wells MW-16C, MW-18C, and MW-20C will target the C zone with a proposed well-screen interval placed between approximately 65- and 85-feet bgs. (It should be noted that per the CVRWQCB, the exact well screen interval placement for each well will be determined by an IES registered professional geologist who will be conducting the well installations. Field observations of encountered soils will determine the well-screen placement for each proposed monitoring well to ensure the appropriate water bearing zones are successfully targeted.) Following completion of the proposed B zone well borings MW-1513, MW-17B and MW-19B to an estimated depth of 60 feet bgs, they will be completed as a groundwater monitoring wells. The construction of the proposed wells will consist of blank 2-inch diameter Schedule 40 polyvinyl chloride (PVC) casing from the surface to an approximate depth of 40 feet bgs and attached beneath with 20 feet of slotted (0.010-inch slots) 2-inch diameter Schedule 40 PVC well screen. The annulus of the screened portion of the monitoring well will be backfilled with a #212 Monterey sand (or equivalent) filter pack from the bottom of each borehole to approximately 1 to 3 feet above the top of the screen interval. The filter material will then be settled by surging each well with a surge block. Additional sand will be California Tank Lines Innovative Environmental Solutions Addendum to Work Plan -5- Encinitas,California