3620 36TH PL NE 2018-01-02 MF Import

I 3.4.2 Topsoil Topsoil consisting of organic rich silt/silty sand with roots from surface vegetation was generally observed in the upper 6 inches of the soil profile in each of the explorations. The topsoil layer appeared to be more developed over native alluvial soils and less developed over the fill soils and wood chips. J 3.4.3 Fill Soils Imported fill soils were encountered across the north, northeast, west, and central areas of the site. The fill materials and thickness varied across the site. The fill soils were commonly observed overlying wood chips. However, in some of the test pits fill soils were observed under the wood chips, as a layer within the wood chips, or mixed in with the wood chips.. In general, the fill soils observed consisted of: • Northeast Area: Fine to medium sand and fine to coarse gravel with sand and wood chips. The till was observed to be 5 to 6 feet thick in TP-I and TP-2, respectively. • North-Central and Central Areas: Fine to medium sand, fine to coarse gravel with sand and wood chips, and quarry spalls. The fill was observed to range from 0.5 to 3 feet thick. • West Area: Quarry spalls with silt, sand and gravel. The fill was observed to be about 3'/2 to 4 feet thick in TP-20 through TP-22. 3.4.4 -Woodchips Wood chips were encountered in the north -central and central areas of the site as shown on Figure 3. The wood chips are apparently residual materials from past logging activities on the site. The wood chips Igenerally consist of chipped or shredded wood materials, typically %2 to 1 %2 inches long and up to about %2-inch wide. In some of the test pits the wood chips were very clean, while other areas had soil mixed with the wood chips: In addition, there are areas (TP-8) where fill soil was observed between two layers of wood chips. As shown on Figure 3, the wood chips generally vary from 0 to 3'/ feet thick, but appear to be 2%2 to 5 feet thick in the area of the existing asphalt pad in the central area of the site. The bottom of the wood chip layer was occasionally 4 to 5 feet below the existing ground surface due to overlying fill and topsoil materials. Areas with the thickest observed wood chips appear to coincide with the topographic high areas in the north -central and bentral areas of the site. 3.4.5 Fine -Grained Alluvial Deposits The topsoil, fill, and wood chips are underlain by compressible native fine-grained deposits consisting of recent alluvial and estuarine deposits. These deposits are composed of organic silt, silt, and interbedded silts and sands. The organic silt and silt deposits were observed in all the test pits and they generally ranged from 5 to over 20 feet thick. The estimated thickness of the compressible layers at the site is shown on Figure 4. The organic silt deposits were commonly observed overlying silt having little organic matter. The organic silt generally ranged from 3 to 10 feet thick. while the less organic silt deposits were commonly 6 to 10 feet thick. The organic silt and silt layers contain variable amounts of fibrous organic material as well as occasional logs up to about 12 inches in diameter. G c o E n g i n e e r s 5 File No. 10625-00"2/123003