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<br />Woodward.Clyde Consultants <br /> <br />'"i Q ('10' <br />"',",'-.)0 <br /> <br />Field observations, recent flooding events and the <br />characteristics of the sandy, low plasticity, alluvial soils <br /> <br />indicate that these surficial soils are easily eroded and <br /> <br />I <br /> <br />transported. In our opinion, final design should consider the <br />direction and route the sediments will f~OW with respect to <br />the functioning of the appurtenant st~~~res. <br />6. Pierre Formation ~ ~ <br />Logs of test holes along t~7roposed dam a~s, Figure 2, <br />show the location and classificat~on of the Pierre formation <br />materials. The formation mat~ut:ls^have been generally <br />classified a siltstone. We ~~~sified the materials as <br />clayey siltstone. The Pierre forma~materials at this site <br />are generally less Cla~~eY~ 'i.e,rre formation materials often <br />found at other locations. so~e;PTer~e formation materials are <br />V I ' <br />fat clays (CH) a~~ain w~a~ seams. We inspected a few <br />samples from one Denison continuous sample hole, 555-0-24, that <br />:____was_r~~e_n_uy(~jn~the:.pr~osed -dam ,n:i's~'-Th-eresults of <br />physical prope~ties~ts made on these samples are contained <br />in a Bureaur:ieino~um dated November 18, 1977 (Ref l4). Some <br />fat cli are in ~id~e in other exploration holes at the <br />site~~t clay )(Weathered shales) were reported in EM-217 <br />(Ref 4) ~t~~~ergencY spillway location. This leads us to <br />conclude that s~e fat clays with low strength may be present <br />within the formation which might affect stability of the dam <br /> <br />and cause uplift of structures. In our opinion, the possible <br /> <br />- 16 - <br /> <br />" <br />