CCP 11-12-1996 - Laserfiche WebLink

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I I. AET #96-2601 - Page 5 I Relatively good stability also appears to be present at Boring #8 on the Hamline A venue Service I Road. However, Boring #9 in the northern more southerly portion of the Hamline A venue Service I Road appears to be slightly to moderately unstable. I The clays below the Snelling Avenue Service Road are judged to be moderately unstable. The fme grained silty sand layer at Boring #11 has more favorable stability. I Drainage I The sands with silt at Borings #6 and #8 are relatively fast draining. The fine grained silty sand at Boring #11 is moderate draining. The remainder of the site soils are relatively slow draining , materials. Because the fast to moderate draining soils are underlain by slow draining soils, water can still build up unless a means of subsurface drainage is provided. Ie Frost Susceptibility , The sands with silt are relatively low in frost susceptibility. Otherwise, the soils are at least moderately high in frost susceptibility. The fme grained silty sands and the silty clays at Borings I #10 and #11 are judged to be highly frost susceptible. , Improvement Discussion , In cases where subgrade soils are poor draining and/or frost susceptible, it is usually desired to place a sand subbase to better control aggregate base and upper subgrade drainage and the frost , related distress. We understand your typical approach on Arden Hills projects is to use a sand subbase, particularly where in place soils are unstable; although make field decisions in certain , areas to eliminate the subbase if significant zones of the street appear favorable in its existing condition. This approach should be feasible for your 1997 Street Improvement projects. At a few , locations, it appears that sands are already in place in the upper subgrade zone. Also, you may ,- find some segments of road which have high levels of stability which can reduce the need for a sand subbase (at least from a stability standpoint). ,