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. , <br /> � ' � - � Ciry of Orono <br /> Project BABX-92-806 <br /> February 3, 1993 <br /> Page 2 <br /> Excavation Observations <br /> Our observations were performed on December 3, 1992, by a senior engineer. Our services <br /> included observing the soils encountered at the surface of the proposed tank pad area. In <br /> addition, shallow hand auger borings were attempted in the slab azea. Soil classifications were <br /> detemuned by examining the auger cuttings. Approximate consistency or density of the soils <br /> encountered was estimated by judging the force required to advance ehe auger. <br /> These hand auger probes encountered frozen sand and silry sand soils. Due to the soils being <br /> frozen, we could not determine the relative densiry of the soIls. <br /> Discussion and Conclusions <br /> Basetl on discussions with Mr. Rivard, we understand that this area had ponded water for some <br /> time prior to freezing. Construction traffic had also rutted the area and caused the soils to <br /> become "pumped up." <br /> Based on the results of our excavation observation and hand auger probes, it is our opinion the <br /> soils encountered in the proposed tank pad area aze not suitable for support of the fuel tank <br /> pads at this time. Silty sands are frost-susceptible soils. Since these soils became saturated and <br /> frozen, 1 to 2 inches of heave and subsequent settlement may occur. We recommend removing <br /> the frost-susceptible soils to a depth of 3 feet and replace them with nonfrost-susceptible sand <br /> or sandy gravel. Sand or sandy gravel with less than 5 percent of the particles by weight <br /> passing a 200 sieve is nonfrost-susceptible. <br /> Altematively, if time allows, we recommend waiting until spri.ng when the soils thaw, <br /> removing the soils, and replacing them in a dried and compacted manner. The fill soils should <br /> be compacted to a minimum of 98 percent of the maximum standard Proctor density (ASTM <br /> D 698). <br /> General <br /> Services performed by Braun Intertec for this project have been conducted in a manner <br /> consistent with that level of care and skill ordinazily exercised by members of the profession <br /> cunently practicing in this area under similar budget and time restraints. No warranry, <br /> expressed or implied, is made. <br />