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<br />- - ----.------- <br /> I <br /> GEOTECHNICAL EXPLORATION AND REVIEW J <br /> FOR <br /> PROPOSED STREET IMPROVEMENTS <br /> ARDEN HILLS, MINNESOTA I <br /> AET #93-1379 I <br /> SUMMARY <br /> PUlllose I <br /> The City of Arden Hills is considering improvements to Keithson Drive, Amble Drive, Bussard I <br /> Court and Dunlap Street. The purpose of our work on this project is to obtain subsurface <br />;." information along the streets, and based on this data, prepare a geotechnical engineering report <br /> presenting comments and recommendations to assist you and the project team in planning and I <br /> construction. <br /> Scope I <br /> To accomplish the above purpose, you have authorized our firm to drill 13 test borings on the <br /> existing streets, perform laboratory testing, and furnish a geotechnical engineering report. <br /> Findine:s I <br /> Most subgrade soils are clayey (lean clays to clayey sands), except for Keithson Drive which <br /> includes a 2' + granular borrow layer at the top of subgrade. The subgrade instability due to . <br /> wet conditions is most apparent in the north segment of Amble Drive and the west segment of <br /> Bussard Court. Otherwise, existing distress appears to be the result of poor subgrade frostl <br /> drainage characteristics. Clayey soils below the granular borrow layer at Keithson Drive are I <br /> judged reasonably stable and consistent, even in roadway "dip" areas. <br /> Recommendations I <br /> These recommendations are in condensed form for your convenience. It is important that you <br /> study our entire report for detailed recommendations. I <br /> . The borings indicate Keithson Drive has favorable subgrade soil conditions. Past local <br /> sagging of the road may be associated with utility trench settlement, although we suspect I <br /> future settlements will be low. Surface improvements by means of cold, in-place <br /> recycling may be the appropriate improvement method for this roadway. <br /> . The remainder of the roadways include significant surface distress, much of which we I <br /> attribute to the poor frost and drainage characteristics of the subgrade. We recommend <br /> reconstruction of these roads, including the use of aI' minimum thickness of Select <br /> Granular Borrow. I <br /> . We recommend increasing the sand layer thickness to 2' in areas of wet, unstable clays. <br />, . Unstable soils in subcut bottoms should be scarified, dried and recompacted until a test- <br />I <br />I <br /> roll can be passed. An alternative would be to place a geotextile fabric at the subcut I <br /> bottom. <br /> . Sand layers should be provided with a means of subsurface drainage. -- <br /> I <br />