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Project No. 1281 <br /> 11ikt01 <br /> dense, water-bearing sand with sih and gravel underlie the organic sihy sand, and extend <br /> to a depth of l0 feet. Very dense unweathered till underlies the very dense sand to the <br /> total depth ofihe boring. <br /> 5.3 Groundwater <br /> Groundwater was observed 'm each boring at depths rangmg between 5 and 8 feet. Pour <br /> days after drilling, water levels were measired at a depth of approximately 10 %z feet in <br /> thc l3-1 and B-3 monitoring wells. <br /> Table 1 —Groundwater Levels At Time of Drilli�and M1ieasared In Wells <br /> Groundwater Levels-DeQth in Feet <br /> Test Boring (Approi. Elevation in Fcet) <br /> At Time o(Drilling 24Aug01 <br /> Ikpth(Glev.)(Datc) <br /> 6-1 S(557) (20Aug01) 10.29(555) <br /> 6-2 7(555) (20AubA1) Dry <br /> I3-3 5(555) (2�Aug01) I0.65(549) <br /> TP-2"" Ury QOJim93) - <br /> TP-9" Dry Q U�m93) - <br /> ' 13as«1 on approxinute wata Ievel depths observ�d during drilling,and as measured in wc1ls <br /> relative to yaoimd surtace. Groimdwater elevations are based on goimd surface elevations <br /> interprded from topographic site plan. <br /> *''I'esl pits lo�ed by GcoEnpnccrs(gcvteehnical report daled 291un93� <br /> In E3-I and F3-3, the groundwater occurred as perched layers within the relatively <br /> penne�ble basal portion of the weathered i:il, and the sand with gravel overlying the <br /> impenncable unweathered till soils. This groundwater condition is commonly referred to <br /> as "interllow," and develops when surfar.e water infiltrates downward through the looser <br /> surficial soils and migrates laterally and down graJient along the top of the unweathered <br /> till surface. In B-2, minor groundWater �vas inferred from saturated cuttings at a depth of <br /> about 7 fcet. In this case, the groundwater likely occurs as a saturated sandy lens or <br /> p�cket within the very dense till. <br /> Our scope of work includes wet season measurements of water levels in the monitoring <br /> wells in orJer to assess maximum expecteJ groundwaler levels and, if required, provide <br /> adJitional rccommendations for detention pond anJ vault construction. <br /> (.0 DISCUSSION AND RECOMMENDATIONS <br /> 6.1 Gencral <br /> Based on the results of the field investigation and analyses, it is our opinion that there are <br /> no gcotechnical conslraints that would preclude project construction as planned provided <br /> our recommendations are incorporated into ihe Jesign. <br /> 'I7re proposcd detention vaults and retaining walls may be supported on the medium � <br /> dense to very Jense, weathered and unweathereJ glacial till soils, or on structur:,l fill <br /> Gedctihnical and T�mnel Engneers <br /> �030125"'/�veNG Phme(325)869-5778 � <br /> Ikllewe.WA�5005 Paµc 4 Fnr (425)86I-0677 <br />