05-21-2012 Planning Commission Packet

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� PC Exhibit A Description of Request—UPDATED MAY 9, 2012 790 N. Brown Road In response to the Planning Commission's questions and suggestion in the March 19tn meeting, I have attached a soil report dated April 30th (the "Report") from Carl Anderson, P.E., P.G., a licensed professional engineer and licensed professional geoscientist with experience in municipal zoning issues related to erosion. Based upon the field survey and drilling of multiple test probes on and immediately below the driveway bed, this Report summarizes "that existing soils at this site have sufFicient stability to allow construction of a home at the site indicated on the Gronberg and Associates survey without the risk of any material soil erosion." The Report also finds: ■ "Below the topsoil, the lean clay become increasingly stiff with depth and can be expected to provide adequate soil bearing capacity for single family residential dwelling footings, designed for clay." ■ "There was also no evidence of any erosion on or near the driveway bed. The fact that the driveway bed has shown no signs of erosion in over a century adds support to the conclusion of this analysis that the soils at this site have sufficient � stability to allow construction of a home at the site indicated on the Gronberg and Associates survey." ■ "The proposed location of a walkout structure on the Gronberg survey is well situated to minimize required grading and take advantage of the steady and gradual slope above the bluff line and to position the rear wall of the foundation just above the stable "shelf' created by the construction of a driveway bed more than a century ago." � ■ "Given the unique contour created by the construction of the driveway bed, positioning the structure further away from the bluff zone may actually create a greater potential for erosion of soil above the driveway bed. Positioning the structure immediately above the driveway bed "shelf" appears to be the most stable position for a structure near the allowed. building envelope in the Gronberg survejr. Having a relatively flat and demonstrably stable 15 foot wide area immediately behind the proposed structure alleviates concerns over erosion immediately behind the structure." . ■ "The large number mature and developing trees add significant stability to the soil below the driveway, mitigating potential concerns over erosion." .. ■ "the slope of the hill immediately below the top of the bluff line near the location of the proposed structure is significantly less than the 30% slope �