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A S S O C I A T E S I N C SCOPE OF WORK Planning and Permits ATC has completed the soil boring permit application for the proposed subsurface investigation. The permit application is attached to this addendum (Attachment 1). The associated permit fees (check no. 384) were previously included in the Workplan. Following the approval of this workplan addendum and monitoring well permit approval, ATC will schedule field personnel and equipment, notify Underground Services Alert to locate underground utilities as required, and perform any other necessary field preparation and job start-up activities. A private underground utility locating service may be warranted due to the proximity of nearby underground sewer, gas, and electrical lines. Installation of Soil Borin s and Monitorint Wells To further assess the extent of impacted soil and groundwater at the site, a total of five soil borings will be advanced at the site (Figure 3). To address lateral definition, four perimeter borings will be advanced to depths of approximately 27 feet bgs. A fifth soil boring will be advanced through the tank pit beyond the depth of existing well MW-1 to a total depth of approximately 35 feet bgs to assess the vertical extent of petroleum hydrocarbon contamination. The soil samples will be collected at five-foot intervals or significant changes in lithology. Drilling will be conducted by a State licensed (C57) drilling company. A field geologist will be present to log all drill cuttings and soil samples. Each soil sample will be field screened with a Photoionization Detection (PID) meter or similar instrument and at least two samples from each of the three borings, based on field observations (i.e. odor, discoloration, PID readings), will be placed in a cooler with ice and submitted for laboratory analysis. Groundwater Monitoring Wells Construction Details All borings will be completed as groundwater monitoring wells. The monitoring wells will be constructed of 2-inch inside diameter schedule 40 PVC well screen and casing. A 0.010-inch well screen slot and #2112 mesh sand pack will be used. Neat cement will be used to seal the wells in accordance with California Well Standards (December 1981). To .protect the integrity of the wells, locking, water-tight well plugs will be installed on each well and a water-tight wellhead labeled "monitoring well" will be concreted over each well. Proposed well construction details are shown on Figures 4 and 5. The top of casing of the new and existing wellheads will be surveyed to assess groundwater gradient and flow direction. All drill cuttings will be stored on site in 55-gallon drums pending laboratory results. wA17292.0002Vq)orts\wkp.dw 2