RES 86453 - Laserfiche WebLink

Mr. Martin W. Inderbitzen May 27, 1986 Page 5 T Step 5. Drilled M7 near the previous boreholes where I .percent; methane had been measured in 1985. Step 6. 'Drilled B4R next to B4 because B4 had collapsed, and a monitoring probe could not be inserted. Field Methodology Boreholes M1 through M4 were drilled using a truck mounted Mobil B53 drilling rig, and boreholes M5 through M9 and B4R were drilled using an All Terrain CME 550 drilling rig. Each rig was equipped with 6-1/2 inch outside-diameter continuous-flight hollow-stem augers. Undisturbed soil samples for visual classification were collected at 5 foot intervals from 5 feet below ground surface to total depth of each borehole using a standard penetration sampler driven ahead of the auger with a 140 pound weight dropped over 30 inches. The number of blows required to penetrate each 6 inch interval were recorded on the borehole logs attached to this report. The sample was described on the borehole log then placed in a labeled plastic bag for storage. With the exception of Borehole M7, each borehole was drilled to an elevation approximately equal to the bottom of the closed landfill. Borehole M7 was drilled to 40 feet below ground surface. A gas monitoring probe was installed in each borehole by inserting slotted 1-inch diameter polyvinyl chloride casing with a maximum of 9 feet of blank casing attached to the top directly through the augers then pouring sand into the borehole as the augers were gradually removed from the borehole. A 1 foot thick layer of bentoni te pellets was emplaced above the sand, and the remaining annular space was filled with cement. A locking steel protective casing was installed at the surface of each probe. To allow access for gas monitoring a stop cock type valve with a hose nipple was installed on the top of each casing. The construction of each probe is shown on the borehole logs attached to this report. Methane Measurements During drilling, measurements of the methane concentration at each 5 foot interval were obtained with a Model NP-204 natural gas meter manufactured by Gastech. The probe was lowered into the hole at 5 foot intervals and the concentration of methane was recorded on the borehole log. At least 24 hours following probe installation the concentration of methane at the probe head was measured by attaching a flexible hose to the hose nipple and the probe of the meter. At most probes there was not a measurable concentration of methane using this method. Depth-specific measurements of methane were obtained by attaching a BROWN AND CALDWELL PO BOX B045 WALNUT CREEK, CA 94596-1220 · (415) 937-9010 TELEX33*6490 · OFFICE AT 348O BUSKIRK AVENUE PLEASANT HILL94523