FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

Mr.Michael Infurna August 4,2010 Page 2 of 3 Monitoring Well Destruction On May 13, 2010, a Ground Zero Geologist, under the supervision of a California Professional Geologist, supervised V&W Drilling, Inc. ([V&W] C57 License #720904) during the destruction of groundwater monitoring wells MW 1, MW2, MW4 and MW5 by pressure grouting. An attempt was made to destroy well MW3 on May 13th, which is located beneath the canopy that covers the station's pump islands, however, the drilling rig, even at half mast, did not have enough vertical clearance to fit beneath the canopy. Consequently, well MW3 was destroyed by overdrilling on June 14,2010,by Fisch Drilling Inc. ([Fisch] C57 License#683865). Ms. Victoria McCartney of EHD was on site to inspect the pressure grouting of wells MW1, MW2, MW4 and MW5 on May 13, 2010 and Mr. Mike Infurna of EHD was on site to inspect the overdrilling and grouting of well MW3 on June 14, 2010. A site plan showing the location of the destroyed monitoring wells is provided as Figure 2. Prior to well destruction activities the depth to bottom (DTB) in all site wells was measured to insure no obstructions were present in any of the wells. The wells were each 2-inches in diameter and were screened from 10 to 30 feet below ground surface (bgs). Well construction details are summarized in Table 1. On May 13, 2010 wells MW1, MW2, MW4 and MW5 were destroyed by pressure grouting with neat cement grout. Neat cement grout was pumped into each well in one slow continuous operation, through a tremie pipe system, until each well was completely full. Pressure was then applied at each wellhead using a pressure cap at approximately 20-25 pounds per square inch (psi) for three minutes forcing the grout through the well screen and into the filter-pack. The grout levels were then checked for subsidence and more grout was added as necessary until the grout level in each well stabilized. After the wells were grouted, the well boxes on wells MW1, MW2, MW4 and MW5 were removed by over-drilling with 8-inch diameter hollow stem augers to a depth of 5 feet bgs. The resulting annulus was then backfilled with neat cement grout to approximately 18-inches below grade and the soil cuttings were used to backfill to just below the ground surface. The surface of each well was completed with concrete dyed black to match the existing asphalt surface. Soil generated during the destruction of wells MW1, MW2, MW4 and MW5 was placed in a DOT approved 55-gallon drum, pending disposal. Well MW3 was destroyed by overdrilling on June 14, 2010, by Fisch using a Geoprobe rig equipped with 8-inch diameter hollow stem augers. Well MW3 was overdrilled to a depth of 32 feet bgs. Prior to drilling, 3/4-inch direct push drilling rods were installed down the center of MW3 to act as guide/centering rods for the augers. After overdrilling to 32 feet bgs the guide rods were removed and the 2-inch diameter well casing was pulled from the borehole. The boring was then grouted with neat cement grout, through the augers, to just below the ground surface. Surface completion consisted of concrete, which was left gray to match the existing surface. All soil generated during the destruction of MW3 was placed in a DOT approved 55-gallon drum, pending disposal. G:\GROUNDZE\WOOLSEY.CHTI Reports\Other Reports\Well Destruction Rpt.doc