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Geologkal ireckxics/Ac. Page 3 Work Plan—Additional Site Characterization Marci's Property Project No. 770.2 October 25,2001 I The detection limits for these compounds are listed below. A Chain of Custody will be completed for all samples collected and tracked to ensure sample integrity. L DetectionLimits:of (pg/Kg) 1,000 I 2.1.3 Monitoring Well Construction I The construction of the deep wells will be the same as the existing deep well MW-105. The construction details are outlined in the table below: CWell No. Dia./TD Screen Slot Sand PackTrans. Grout Seal Seal - san = _ 86'-surface MW-106 90 sand -sur ace i i The wells will be constructed using. two inch (27) schedule 40 PVC casing with flush threads. Before installing the bentonite seal the wells will be surged using a clean surge block to achieve maximum filter pack-density. The transition seals will consist of weighted bentonite pellets. A surface seal will be achieved by pumping a neat cement grout (augmented with < 4% bentonite) through the augers, :as they are withdrawn to ensure that an integral grout seal is achieved. The wells will be secured with locking watertight caps encased in flush mounted traffic.rated well boxes. Well construction details are illustrated in Figure 3. 2.1A Monitoring Well Development After the well sealing materials have set (>24 hours), all of the new wells will be developed (using mechanical surging and pumping methods) until a clear stream of water is obtained. The wells will be purged and groundwater samples collected after well development. All development and purge water will be containerized in 55 gallon DOT approved containers and stored on site until their disposition can be arranged. 2.1.5 Well Head Elevation and Location Survey In accordance with Assembly Bill 2886, the location.and elevation of the new and existing well casings will be determined by a licensed surveyor. The surveyor will reference the casings into a benchmark elevation and this data will be included in future groundwater monitoring reports. 2.2 Groundwater-Monitoring The new wells will be incorporated into the current quarterly sampling/monitoring schedule. The schedule will be augmented with monthly depth to groundwater measurements to better define groundwater direction gradient trends. L