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�--r....�..--- -- <br /> �a <br /> DAVID L. �ELSON AND ASSOCIATES, INC. <br /> �„� Consulting Enginecring Geology <br /> ' ' May 37 , 1991 <br /> Project No. 4791 <br /> Page 6 <br /> �. <br /> i <br /> Since the steeper portions of the slope areas were found to be unde:iain <br /> �y primarily by dense glacial till, the site is considered stable with respect to <br /> � deep seated slides. The steeper gradients on site could be susceptible to <br /> � i shallow sloughing failures downslope, due to the presence of. the fill on the <br /> slope above the dense till. If ground water seepage (springs) were to occur <br /> in this vicinity, this susceptibility would increase. Provisions for <br /> i3 maintaining existing slope stability, including drainage control, earthwork <br /> 1 (filling and grading) control and structure placement, are presented herein to <br /> I� reduce potential risk of slope failures. <br /> � � <br /> � Springs!Grcund Water Seepage Areas <br /> E These two elements mentioned in the new ordinance are similar conditions, <br /> which are discussed together in this report. During our evaluation of the <br /> �� site, we observed the surface areas for springs and seeps, and observed our <br /> backhoe exploration (test) pits for ground water seepage conditions. <br /> I �' <br /> I � <br /> We did not encounter any evidence at all of springs or seeps within the site <br /> � ; alonq the southeasterly slope. Our discussions and recommendations in the <br /> � �� followinq RECOt�fENDATIONS section present methods of mitigation of any perched <br /> � or seepaqe waters encountered during construction. <br /> f� <br /> ' , Steep Slopes Associated With The Above Elements <br /> � ry The new ordinance states that steep slopes are those at 25 percent or greater. <br /> The steep slopes as defined are located below the "top-of-slope", southeast of <br /> i� the proposed duplex. As discussed previously, the underlyinq till is <br /> considered a stable geologic unit with respect to landslides. We recommend in <br /> ; the "Foundation" section a minimum depth of embedment into the till for all <br /> 1�' foundations located within 10 feet of the slope or on the slope. This <br /> embedment provides an effective setback of the foundation to the slope face oE <br /> L5 to 6 feet. <br /> � <br /> � <br />