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645 -3601 TWIN CITY TESTING AND ENGINEERING LABORATORY, INC. REPORT OF: LABORATORY No. 9 -4010 ENGINEERS AND CHEMISTS 662 Cromwell Avenue - St. Paul, Minn. 55114 EXCAVATION INSPECTION DATE: September 5, 1972 PAGE: 2 INVESTIGATION (cont,) north footing line of the proposed construction. In this area the soils consisted of fine - grained, brown sand. The excavation extended to approximate elevation 885'. In this portion of the site the footings will bear on the natural sands. In the area designated for future construction we performed inspections of the east and north central portions. In these areas we observed the excavation of up to 6' of peat and soft silty clay. In the east portion of the site the excavation extended to approx- imate elevation 872' to a stratum of fine - grained, brown waterbearing sand. In the north central portion of the site the excavation extended to approximate elevation 870' where it was necessary to remove deeper layers of peat and soft silty clay. At the bottom of the excavation we encountered less than 6" of gray sandy silt overlying brown, fine - grained sands. At the time of our inspection there was less than 1' of water ponded in this portion of the site. In addition to our inspections we performed a series of six field density determinations etween August 4 and August 10, 1972. The results of these tests reported on August 15, 1972 indicated percentage compaction greater than 95 percent of the standard specified by ASTM:D698 -70. However, six field densities performed throughout a fill depth of up to 19' and over a relatively large area could not be representative of the entire fill system. Therefore, on August 18, 1972, we performed a deep standard penetration boring at the southeast corner of the building presently proposed for construction. The soil sampling was performed in accordance with ASTM:D1586 -67. Using this procedure, a 2" 0.D. split - barrel sampler is driven into the soil by a 140 -1b weight falling 30 ". After an initial set of 6 ", the number of blows required to drive the sampler an additional 12" is known as the penetration resistance or "N" value. The "N" value is an index of the relative density of cohesionless soils and the consistency of cohesive soils. As the samples were obtained in the field they were visually and manually classified by the crew chief in accordance with ASTM:D2488 -69. Representative portions of all samples were then returned to the laboratory for further examination and for verification of the field classification. Logs of the borings indicating the depth and identification of the various strata, the "N" value, water level information and pertinent information regarding the method of maintaining and advancing the drill holes are attached. Charts illustrating the soil classification procedure, the descriptive terminology and symbols used on the boring logs are also attached. The boring log indicates there is approximately 17' of generally granular fill in the south- east portion of the site. For the most part the fill is in a medium dense state with a 2' layer of relatively loose fill approximately 8' below the proposed floor elevation. The underlying soils consist of medium consistency silty clay and clayey silt. At the time of 5e boringawater was noted below the depth of the fill. However, our observations of the ater level during the excavation operations indicate with time the water level probably will rise another 3' to 4'. AS A MUTUAL PROTECTION TO CLIENTS. THE PUBLIC AND OURSELVES, ALL REPORTS ARE SUBMITTED AS THE CONFIDENTIAL PROPERTY OF CLIENTS, AND AUTHOR. IZATION FOR PUBLICATION OF STATEMENTS, CONCLUSIONS OR EXTRACTS FROM OR REGARDING OUR REPORTS IS RESERVED PENDING OUR WRITTEN APPROVAL.