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C- A% A S S O C I A T E S I N C SCOPE OF WORK Planning ATC has prepared the drilling permit application for installation of the proposed monitoring wells. The permits and associated fees are attached. ATC will also schedule field personnel and equipment, notify Underground Services Alert to locate underground utilities as required, and perform other necessary field preparation and job start-up activities. Monitoring Well Installation Two groundwater monitoring wells (MW7 and MW8) will be installed at the locations shown on Figure 2 using a hollow stem auger drilling rig. Drilling will be conducted by a State-licensed (C57) drilling company. A field geologist will be present to log drill cuttings and soil samples from the borings. Descriptions of soil types encountered and sample collection intervals will be recorded on boring/well logs. The monitoring wells will be constructed of 2-inch inside diameter schedule 40 PVC well screen and casing with approximately ten feet of 0.020 inch slot screened PVC. Based on recent historical groundwater elevation data, it is anticipated the wells will be installed to a depth of approximately 16 feet bgs. A sand pack will be placed in the annulus of the well extending from the bottom of the well screen to approximately one foot above the top of the screen. Approximately one foot of bentonite will be placed on top of the sand pack and hydrated with potable water. The remaining annulus will be grouted to surface with cement grout. To protect the integrity of the wells, locking,watertight well plugs will be installed on each well and a flush-mounted watertight wellhead labeled "monitoring well" will be installed over each well. Once the monitoring wells are installed, the tops of the well casings will be surveyed to sub-meter accuracy relative to a known benchmark by a State of California licensed land surveyor. Well Development and Groundwater Sampling At least 48 hours after installation, the two new wells will be developed using surging and bailing techniques until the purged groundwater is relatively sediment free. The wells will be sampled at least 48 hours after they are developed. Prior to the collection of groundwater samples, the depth to groundwater will be measured in each well to evaluate the direction and magnitude of the groundwater gradient beneath the site and a minimum of three well volumes (casing and sand pack) of groundwater will be purged from each well. Temperature, pH, and electric conductivity will be measured and allowed to stabilize. Groundwater samples will be collected using disposable bailers, one dedicated to each well. Groundwater samples collected from the monitoring wells will be submitted under chain-of-custody procedures to a State-certified laboratory. The groundwater samples will be analyzed for TPHg by EPA Method 8015B and BTEX and MTBE by EPA Method 8260B. Purged groundwater will be �-' stored in 55-gallon drums approved for hazardous liquid storage pending laboratory results. sA17861\reports\wdIinstwkpin.doc 3